Mucosal Humoral Immune Responses Research Articles

Cell-Mediated Proteomics, and Serological and Mucosal Humoral Immune Responses after Seasonal Influenza Immunization: Characterization of Serological Responders and Non-Responders.

Immunization against influenza through vaccination is the most effective method with which to prevent infection. To assess protection after immunization, analysing humoral response with a hemagglutinin inhibition assay is the gold standard, but cell-mediated immune response has been shown to better correlate with protection in the elderly. Our aim was to explore the influenza-specific cell-mediated and mucosal humoral responses in serologically defined responders and non-responders. We analysed sera for total immunoglobulins (Ig) A, G, and M and nasal swab samples for influenza-specific IgA. Peripheral blood mononuclear cells were stimulated with trivalent influenza vaccine VaxiGripTetra, and supernatants were analysed for influenza-specific responses with the Olink Immune-Oncology panel using a proximity extension assay. We included 73 individuals, of which 69 completed the study with follow-up sampling at one and six months post-vaccination. Of the 73, 51 (70%) were found to be serological responders and 22 (30%) were non-responders. We did not find any significant differences in sex or mucosal humoral response between responders and non-responders; however, a higher IFNγ/IL-10 ratio in individuals ≤65 years of age indicates an enhanced cell-mediated immune response in this age group. Characteristics of the non-responders were found to be higher levels of IgM, Granzyme B and Interleukin 12, and lower levels of C-X-C motif chemokine 13 compared with those of the responders. In conclusion, our results did not show any correlation between serological response and age. Furthermore, the majority of influenza-specific cell-mediated immune markers did not differ between responders and non-responders; the immune marker profile of the non-responders and its contribution to protection is of interest but needs to be further explored.

Mucosal humoral immune response of respiratory tract in medical workers during the post-COVID-19 period

Currently, the role of local respiratory tract immunoglobulins in COVID-19 and rearrangement of mucosal immune response in the post-COVID period have not been sufficiently studied. Our aim was to evaluate long-term effects of novel coronavirus infection on the mucosal immunity in healthcare workers over the post-infection period.
 A total of 180 healthcare workers, ranging in age from 18 to 65 years, were enrolled in a one-stage, cross-sectional study. The subjects with a history of COVID-19 were divided into three groups, depending on the severity of their disease. The control group consisted of 44 healthcare workers who had no history of novel coronavirus infection. Secretory immunoglobulin A (sIgA) and total immunoglobulin G (IgG) levels were quantified in saliva samples, induced sputum samples, naso- and oropharyngeal scrapings by ELISA technique. Specific anti-SARS-CoV-2 IgG antibodies were quantified in the serum by chemiluminescence immunoassay.
 Numerous shifts in adaptive immune response were detected for different mucosal compartments, i.e., in subjects who suffered from severe or moderate-to-severe COVID-19, salivary sIgA levels were significantly higher than those in the control group (p 0.05 and p 0.005, respectively). An inverse correlation was demonstrated between the levels of total sIgA in all mucosal sites, and the number of days from the onset of disease to the start of study (r = 0.278, р 0.05). When compared to the control subjects, all the patients with prior COVID-19 had significantly higher levels of total IgG in the induced sputum samples. Total IgG in saliva was also higher in the group of patients who had severe infection (p 0.05). By contrast, IgG levels in nasopharyngeal samples were decreased in severe and moderately severe groups compared to the control group, thus, probably, indicating an immunodeficiency state in these cases. A direct significant correlation was also detected between the levels of total IgG in all studied samples and the levels of specific IgG antibodies against SARS-CoV-2 in the serum.
 Long-term changes in the humoral mucosal immune response were most pronounced in the healthcare workers with a history of severe or moderate-to-severe COVID-19.

BCG vaccine-induced mucosal humoral immunity in human nasal associated lymphoid tissue

ObjectivesMycobacterium tuberculosis (Mtb) is the causative pathogen of tuberculosis (TB). TB vaccine studies have long been conducted. Since the discovery of the successful intradermally administered Mycobacterium bovis Bacillus Calmette–Guérin (BCG) vaccine against TB, no licensed TB mucosal vaccine has yet been approved. Our research aims to investigate the suitability of human NALT-derived MNCs as an in vitro human cell culture model to explore the mucosal humoral immune responses to the BCG vaccine. Moreover, to assure that BCG vaccine able to induce the different antibody isotypes including IgG, IgM and IgA. MethodsTonsils from 20 patients who underwent elective tonsillectomies at Madinah Germany Hospital were recruited. Tonsillar mononuclear cells (MNCs) were separated and co-cultured in the presence and absence of the BCG vaccine. ELISA was used to measure BCG-induced IgG, IgM and IgA antibodies in the cell culture supernatants following stimulation and culture. ResultsNasal-associated lymphoid tissue (NALT) cell culture as an in vitro model was successfully used to evaluate the BCG-induced humoral immune response. Significant (p = 0.001, n = 20) levels of specific, anti-TB IgG, IgM, and IgA antibody responses were detected in MNCs stimulated with the BCG vaccine compared with unstimulated MNCs. Significant differences were found between anti-TB antibody classes. Anti-TB IgG antibody was significantly higher (mean = 2.33) than anti-TB IgM (mean = 1.37) antibody (p = 0.0001, n = 20). Anti-TB IgM antibody was significantly higher than IgA (mean = 0.93) antibody (p = 0.0018, n = 20). ConclusionsThe current human model will be beneficial for the future comprehensive study of other immune components such as cellular immune responses to the BCG vaccine. The model would be ideal to design, improve and study the possible intranasal use of the BCG vaccine.

Mucosal immunity in health care workers’ respiratory tracts in the post-COVID-19 period

Coronavirus disease (COVID-19) has generated interest in the assessment of systemic immune status, but existing knowledge about mucosal immunity is clearly insufficient to understand the full pathogenetic mechanisms of the disease. The aim of this study was to evaluate the long-term effects of novel coronavirus infection on mucosal immunity in the postinfection period among health care workers (HCWs). A total of 180 health care workers with and without a history of COVID-19 who ranged in age from 18 to 65 years were enrolled in this one-stage, cross-sectional study. The study subjects completed the 36-Item Short Form (36) Health Survey (SF-36) and the Fatigue Assessment Scale. Secretory immunoglobulin A (sIgA) and total immunoglobulin G (IgG) levels were quantified in saliva samples, induced sputum samples, and nasopharyngeal and oropharyngeal scrapings by an enzyme-linked immunosorbent assay. Specific anti-SARS-CoV-2 IgG antibodies were quantified in serum samples by chemiluminescence immunoassay. Analysis of the questionnaire data showed that all HCWs with a history of COVID-19 reported health problems that limited their daily activities and negative changes in their emotional health three months after the disease, regardless of its severity. The following shifts were detected in the adaptive arm of the immune response in different mucosal compartments. Among subjects who had severe or moderate-to-severe COVID-19, salivary sIgA levels were significantly higher than those in the control group (p < 0.05 and p < 0.005, respectively). Compared to the subjects in the control group, all subjects with prior COVID-19 had significantly higher levels of total IgG in induced sputum. In the group of patients who had had severe infection, total IgG in saliva was also higher (p < 0.05). A direct statistically significant correlation was also detected between the levels of total IgG in all studied samples and the levels of specific IgG antibodies against SARS-CoV-2 in the serum. A significant correlation was observed between total IgG levels and the parameters of physical and social activities, mental health, and fatigue levels. Our study demonstrated long-term changes in the humoral mucosal immune response, which were most pronounced in health care workers with a history of severe or moderate-to-severe COVID-19, and an association of these changes with certain clinical signs of post-COVID-19 syndrome.

Correction: Guerrieri et al. Nasal and Salivary Mucosal Humoral Immune Response Elicited by mRNA BNT162b2 COVID-19 Vaccine Compared to SARS-CoV-2 Natural Infection. Vaccines 2021, 9, 1499

The authors wish to make the following corrections to this paper [...].

Characterization of Systemic and Mucosal Humoral Immune Responses to an Adjuvanted Intranasal SARS-CoV-2 Protein Subunit Vaccine Candidate in Mice.

Continuous viral evolution of SARS-CoV-2 has resulted in variants capable of immune evasion, vaccine breakthrough infections and increased transmissibility. New vaccines that invoke mucosal immunity may provide a solution to reducing virus transmission. Here, we evaluated the immunogenicity of intranasally administered subunit protein vaccines composed of a stabilized SARS-CoV-2 spike trimer or the receptor binding domain (RBD) adjuvanted with either cholera toxin (CT) or an archaeal lipid mucosal adjuvant (AMVAD). We show robust induction of immunoglobulin (Ig) G and IgA responses in plasma, nasal wash and bronchoalveolar lavage in mice only when adjuvant is used in the vaccine formulation. While the AMVAD adjuvant was more effective at inducing systemic antibodies against the RBD antigen than CT, CT was generally more effective at inducing overall higher IgA and IgG titers against the spike antigen in both systemic and mucosal compartments. Furthermore, vaccination with adjuvanted spike led to superior mucosal IgA responses than with the RBD antigen and produced broadly targeting neutralizing plasma antibodies against ancestral, Delta and Omicron variants in vitro; whereas adjuvanted RBD elicited a narrower antibody response with neutralizing activity only against ancestral and Delta variants. Our study demonstrates that intranasal administration of an adjuvanted protein subunit vaccine in immunologically naïve mice induced both systemic and mucosal neutralizing antibody responses that were most effective at neutralizing SARS-CoV-2 variants when the trimeric spike was used as an antigen compared to RBD.

Preclinical evaluation of safety and immunogenicity of a primary series intranasal COVID-19 vaccine candidate (BBV154) and humoral immunogenicity evaluation of a heterologous prime-boost strategy with COVAXIN (BBV152).

Most if not all vaccine candidates developed to combat COVID-19 due to SARS-CoV-2 infection are administered parenterally. As SARS-CoV-2 is transmitted through infectious respiratory fluids, vaccine-induced mucosal immunity could provide an important contribution to control this pandemic. ChAd-SARS-CoV-2-S (BBV154), a replication-defective chimpanzee adenovirus (ChAd)-vectored intranasal (IN) COVID-19 vaccine candidate, encodes a prefusion-stabilized version of the SARS-CoV-2 spike protein containing two proline substitutions in the S2 subunit. We performed preclinical evaluations of BBV154 in mice, rats, hamsters and rabbits. Repeated dose toxicity studies presented excellent safety profiles in terms of pathology and biochemical analysis. IN administration of BBV154 elicited robust mucosal and systemic humoral immune responses coupled with Th1 cell-mediated immune responses. BBV154 IN vaccination also elicited potent variant (omicron) cross neutralization antibodies. Assessment of anti-vector (ChAd36) neutralizing antibodies following repeated doses of BBV154 IN administration showed insignificant titers of ChAd36 neutralizing antibodies. However, the immune sera derived from the same animals displayed significantly higher levels of SARS-CoV-2 virus neutralization (p<0.003). We also evaluated the safety and immunogenicity of heterologous prime-boost vaccination with intramuscular (IM) COVAXIN-prime followed by BBV154 IN administration. COVAXIN priming followed by BBV154 IN-booster showed an acceptable reactogenicity profile comparable to the homologous COVAXIN/COVAXIN or BBV154/BBV154 vaccination model. Heterologous vaccination of COVAXIN-prime and BBV154 booster also elicited superior (p<0.005) and cross variant (omicron) protective immune responses (p<0.013) compared with the homologous COVAXIN/COVAXIN schedule. BBV154 has successfully completed both homologous and heterologous combination schedules of human phase 3 clinical trials and received the restricted emergency use approval (in those aged above 18 years) from the Drugs Controller General of India (DCGI).

Nasal Administration of M2e/CpG-ODN Encapsulated in N-Trimethyl Chitosan (TMC) Significantly Increases Specific Immune Responses in a Mouse Model.

The nasal passage is the primary entry point for many infectious agents. Therefore, nasal vaccines that can overcome the limitations associated with antigen uptake are likely to play an important role in protecting these infectious agents. Thus, adjuvants and antigen-carrying systems that can induce a suitable mucosal and systemic immune response against their accompanying antigens are highly important. In this study, synthetic oligodeoxynucleotides containing CpG motifs (CpG-ODN) accompanied by the recombinant ectodomain of influenza M2 protein were encapsulated in N-trimethyl chitosan (TMC) nanoparticles. After the preparation of TMC nanoparticles, the morphological characteristics and loading efficiency and in vitro antigen release, as well as their ability to induce efficient immune responses against M2e in intranasal inoculation in the mouse model, were studied. Based on the size and zeta potential of the nanoparticles prepared in this study, it was determined that they were all nanosized, and their positive zeta potential ranged from 25 to 28 mV, while their polydispersity index was between 0.1 to 0.2, indicating a narrow range of particle sizes. A significant increase in serum levels of the total M2e-specific IgG antibody and BALF anti-M2e IgA was observed in mice intranasally immunized with M2e/CpG-ODN/TMC as opposed to those that were intranasally immunized with M2e/TMC, M2e/CpG-ODN, free M2e, and CpG-ODN/TMC. There was also a significant change in the IgG2a/IgG1 ratio in favour of IgG2a seems that CpG-ODN is responsible for directing the immune system towards Th1. Our findings show that CpG-ODN can significantly enhance the mucosal and systemic humoral immune response against M2e when encapsulated in a suitable carrier such as TMC for intranasal administration. In conclusion, when combined with a suitable carrier, CpG-ODN can be considered an effective adjuvant for mucosal administration.

Evaluation of the systemic and mucosal immune response induced by COVID-19 and the BNT162b2 mRNA vaccine for SARS-CoV-2.

BackgroundThe currently used SARS-CoV-2 mRNA vaccines have proven to induce a strong and protective immune response. However, functional relevance of vaccine-generated antibodies and their temporal progression are still poorly understood. Thus, the central aim of this study is to gain a better understanding of systemic and mucosal humoral immune response after mRNA vaccination with BNT162b2.MethodsWe compared antibody production against the S1 subunit and the RBD of the SARS-CoV-2 spike protein in sera of BNT162b2 vaccinees, heterologous ChAdOx1-S/BNT162b2 vaccinees and COVID-19 patients. We monitored the neutralizing humoral response against SARS-CoV-2 wildtype strain and three VOCs over a period of up to eight months after second and after a subsequent third vaccination.ResultsIn comparison to COVID-19 patients, vaccinees showed higher or similar amounts of S1- and RBD-binding antibodies but similar or lower virus neutralizing titers. Antibodies peaked two weeks after the second dose, followed by a decrease three and eight months later. Neutralizing antibodies (nAbs) poorly correlated with S1-IgG levels but strongly with RBD-IgGAM titers. After second vaccination we observed a reduced vaccine-induced neutralizing capacity against VOCs, especially against the Omicron variant. Compared to the nAb levels after the second vaccination, the neutralizing capacity against wildtype strain and VOCs was significantly enhanced after third vaccination. In saliva samples, relevant levels of RBD antibodies were detected in convalescent samples but not in vaccinees.ConclusionsOur data demonstrate that BNT162b2 vaccinated individuals generate relevant nAbs titers, which begin to decrease within three months after immunization and show lower neutralizing potential against VOCs as compared to the wildtype strain. Large proportion of vaccine-induced S1-IgG might be non-neutralizing whereas RBD-IgGAM appears to be a good surrogate marker to estimate nAb levels. A third vaccination increases the nAb response. Furthermore, the systemic vaccine does not seem to elicit readily detectable mucosal immunity.

Systemic and Mucosal Humoral Immune Response Induced by Three Doses of the BNT162b2 SARS-CoV-2 mRNA Vaccines.

BNT162b2 (BioNTech/Pfizer) was the first SARS-CoV-2 mRNA vaccine approved by the European Medicines Agency. We monitored the long-term humoral responses of healthcare workers (HCWs) who received three vaccine doses. A total of 59 healthcare workers were studied: 47 were never SARS-CoV-2-infected (naïve-HCWs), and 12 (infected-HCWs) recovered from COVID-19 before the first vaccine. Serum and saliva were collected at baseline (before the first dose), just before the second dose, 1, 3, 6, and 9 months after the second dose, and 10 days after the third vaccine. SARS-CoV-2-specific IgG and IgA were evaluated in serum and saliva, respectively, and the presence of neutralizing antibodies (NAb) was analyzed in serum. SARS-CoV-2-specific IgG peaked one month after the second vaccine in naïve-HCWs but right before this timepoint in infected-HCWs. IgG titers significantly decreased during follow-up and at month 9 were still detectable in 50% of naïve-HCWs and 90% of infected-HCWs. NAb were significantly decreased 6 months after the second vaccine in naïve-HCWs and 9 months after this dose in infected-HCWs. Salivary SARS-CoV-2-specific IgA titers were significantly higher in infected-HCWs and were undetectable 9 months after the second vaccine in 43% of the naïve-HCWs alone. The third vaccine greatly increased humoral IgG and mucosal IgA in both groups. Two BNT162b2 doses induced strong systemic and humoral immune responses; to note, these responses weakened over time, although they are more prolonged in individuals who had recovered from COVID-19. The third vaccine dose quickly boosts systemic and mucosal humoral responses.

Altered Immunoglobulin Repertoire and Decreased IgA Somatic Hypermutation in the Gut during Chronic HIV-1 Infection.

ABSTRACTHumoral immune perturbations contribute to pathogenic outcomes in persons with HIV-1 infection (PWH). Gut barrier dysfunction in PWH is associated with microbial translocation and alterations in microbial communities (dysbiosis), and IgA, the most abundant immunoglobulin (Ig) isotype in the gut, is involved in gut homeostasis by interacting with the microbiome. We determined the impact of HIV-1 infection on the antibody repertoire in the gastrointestinal tract by comparing Ig gene utilization and somatic hypermutation (SHM) in colon biopsies from PWH (n = 19) versus age and sex-matched controls (n = 13). We correlated these Ig parameters with clinical, immunological, microbiome and virological data. Gene signatures of enhanced B cell activation were accompanied by skewed frequencies of multiple Ig Variable genes in PWH. PWH showed decreased frequencies of SHM in IgA and possibly IgG, with a substantial loss of highly mutated IgA sequences. The decline in IgA SHM in PWH correlated with gut CD4+ T cell loss and inversely correlated with mucosal inflammation and microbial translocation. Diminished gut IgA SHM in PWH was driven by transversion mutations at A or T deoxynucleotides, suggesting a defect not at the AID/APOBEC3 deamination step but at later stages of IgA SHM. These results expand our understanding of humoral immune perturbations in PWH that could have important implications in understanding mucosal immune defects in individuals with chronic HIV-1 infection.IMPORTANCE The gut is a major site of early HIV-1 replication and pathogenesis. Extensive CD4+ T cell depletion in this compartment results in a compromised epithelial barrier that facilitates the translocation of microbes into the underlying lamina propria and systemic circulation, resulting in chronic immune activation. To date, the consequences of microbial translocation on the mucosal humoral immune response (or vice versa) remains poorly integrated into the panoply of mucosal immune defects in PWH. We utilized next-generation sequencing approaches to profile the Ab repertoire and ascertain frequencies of somatic hypermutation in colon biopsies from antiretroviral therapy-naive PWH versus controls. Our findings identify perturbations in the Ab repertoire of PWH that could contribute to development or maintenance of dysbiosis. Moreover, IgA mutations significantly decreased in PWH and this was associated with adverse clinical outcomes. These data may provide insight into the mechanisms underlying impaired Ab-dependent gut homeostasis during chronic HIV-1 infection.

SARS-CoV-2 Vaccines: The Mucosal Immunity Imperative

The incessant continuance of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is attributable, in part, to ongoing viral residence, replication, and mutation within the upper airways of not only unvaccinated but also vaccinated individuals. It is this exposed portal of viral entry that gives rise to breakthrough infections as well as to ongoing interpersonal transmission. None of this is unanticipated in that the current, parenterally administered SARS-CoV-2 vaccines engender effective humoral (IgG-dominated) immunity but only limited mucosal (secretory IgA-dominated) immunity.1Russell M.W. Moldoveanu Z. Ogra P.L. Mestecky J. Mucosal immunity in COVID-19: a neglected but critical aspect of SARS-CoV-2 infection.Front Immunol. 2020; 11611337Crossref Scopus (138) Google Scholar A new generation of intranasal, mucosal immunity-inducing SARS-CoV-2 vaccines could potentially reverse this state of affairs. Early clinical trials to this very end are presently underway. It is also possible that all-out protection from SARS-CoV-2 will require the concurrent or sequential delivery of both parenteral and intranasal vaccines. In this Perspective, we review the potential benefit of mucosal immunity-inducing SARS-CoV-2 vaccines, explore recent developments in this arena, and discuss the potential impact thereof on the course of the ongoing pandemic. The current parenterally administered SARS-CoV-2 vaccines are remarkable for their effectiveness in reducing the likelihood of hospitalization and in-hospital death. However, their capacity to prevent breakthrough infections remains limited, a deficiency that appears to be related to the limited mucosal immune (IgA) response elicited by the parenteral vaccines.2Amanatidou E. Gkiouliava A. Pella E. et al.Breakthrough infections after COVID-19 vaccination: insights, perspectives and challenges.Metabol Open. 2022; 14100180Crossref PubMed Google Scholar These realities are consistent with the observation that parenterally administered SARS-CoV-2 vaccines give rise to prominent increments in the circulating levels of IgG antibodies against the SARS-CoV-2 receptor-binding domain (RBD) and spike protein (SP) while parallel increments in the circulating levels of IgM and IgA counterparts have proven far more modest.3Wang Z. Schmidt F. Weisblum Y. et al.mRNA vaccine-elicited antibodies to SARS-CoV-2 and circulating variants.Nature. 2021; 592: 616-622Crossref PubMed Scopus (697) Google Scholar Although a modicum of SARS-CoV-2–specific IgA activity was detected in nasal and salivary secretions after the parenteral administration of the mRNA-BNT162b2 SARS-CoV-2 vaccine, it appears that the degree of local mucosal protection afforded by most parenterally administered SARS-CoV-2 vaccines does not rise to a level that is clinically relevant.4Guerrieri M. Francavilla B. Fiorelli D. et al.Nasal and salivary mucosal humoral immune response elicited by mRNA BNT162b2 COVID-19 vaccine compared to SARS-CoV-2 natural infection.Vaccines (Basel). 2021; 9: 1499Crossref PubMed Scopus (17) Google Scholar The mRNA vaccines in current use are capable of producing a mucosal IgG response, but current evidence suggests that it is the IgA response that is required to prevent breakthrough infections and their related communal spread. It follows that vaccine-mediated all-out protection against SARS-CoV-2, one comprising both systemic IgG and mucosal IgA responses, has yet to materialize. The limitations ascribed to the current parenterally administered SARS-CoV-2 vaccines are hardly novel. Similar challenges have plagued the parenterally administered vaccines for the prevention of pertussis, or whooping cough. Indeed, vaccines directed against Bordetella pertussis, not unlike their SARS-CoV-2 counterparts, failed to bring about mucosal immunity capable of preventing infection or communal transmission. Notably, both SARS-CoV-2 and B. pertussis are restricted to the respiratory tract. Dissemination of either pathogen beyond the airway epithelium is rarely encountered. It therefore stands to reason that durable protection of the airways from either B. pertussis or SARS-CoV-2 may well require intranasal, mucosal immunity-inducing vaccines. Recent developments appear consonant with this presumption. The intranasal administration of a live attenuated B. pertussis vaccine (BPZE1) to nonhuman primates proved strongly protective against a challenge by a highly virulent B. pertussis isolate.5Jahnmatz M. Richert L. Al-Tawil N. et al.Safety and immunogenicity of the live attenuated intranasal pertussis vaccine BPZE1: a phase 1b, double-blind, randomised, placebo-controlled dose-escalation study.Lancet Infect Dis. 2020; 20 (Published correction appears in Lancet Infect Dis. 2020;20(9):e215): 1290-1301Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar Moreover, early phase 2b clinical trials of intranasally administered BPZE1 gave rise to durable mucosal immunity.5Jahnmatz M. Richert L. Al-Tawil N. et al.Safety and immunogenicity of the live attenuated intranasal pertussis vaccine BPZE1: a phase 1b, double-blind, randomised, placebo-controlled dose-escalation study.Lancet Infect Dis. 2020; 20 (Published correction appears in Lancet Infect Dis. 2020;20(9):e215): 1290-1301Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar However, the consequent prevention of B. pertussis transmission and pertussis disease is less than certain. A similar situation pertains to the intranasal live attenuated influenza vaccine (brand name in the United States, FluMist Quadrivalent) that was first approved in 2003. The vaccine showed a significant loss of effectiveness between 2013 and 2016, leading the Centers for Disease Control and Prevention to suspend the recommendation for its use. The recommendation was reinstated for the 2018-2019 influenza season, when the reformulated vaccine was shown to be as effective as the parenterally administered vaccine. There are no data currently available to indicate that its ability to attenuate spread of the virus is superior to that of the parentally administered vaccine. Evidence in support of the effectiveness of intranasal vaccination against SARS-CoV-2 has thus far been derived from studies in several animal species. Two recent reports indicate that intranasal administration of recombinant RBD of the SARS-CoV-2 SP to mice can elicit a robust mucosal immune response that persisted long term. In 1 case, the intranasal vaccine was administered as a booster after parenteral prevaccination.6Lam J.Y. Ng Y.Y. Yuen C.K. et al.A nasal omicron vaccine booster elicits potent neutralizing antibody response against emerging SARS-CoV-2 variants.Emerg Microbes Infect. 2022; 11: 964-967Crossref PubMed Scopus (4) Google Scholar In the second case, administration was to unvaccinated mice.7Lei H. Alu A. Yang J. et al.Intranasal administration of a recombinant RBD vaccine induces long-term immunity against Omicron-included SARS-CoV-2 variants.Signal Transduct Target Ther. 2022; 7: 159Crossref PubMed Scopus (4) Google Scholar In both cases, effectiveness extended to neutralization of the Omicron variant. Particularly compelling are additional studies in hamsters that have found the ability of mucosal (intranasal or oral) vaccine administration to prevent animal-to-animal transmission.8Wu Y. Huang X. Yuan L. et al.A recombinant spike protein subunit vaccine confers protective immunity against SARS-CoV-2 infection and transmission in hamsters.Sci Transl Med. 2021; 13eabg1143Crossref Scopus (24) Google Scholar,9Langel S.N. Johnson S. Martinez C.I. et al.Adenovirus type 5 SARS-CoV-2 vaccines delivered orally or intranasally reduced disease severity and transmission in a hamster model.Sci Transl Med. Published online May 5, 2022; https://doi.org/10.1126/scitranslmed.abn6868Crossref PubMed Scopus (13) Google Scholar These findings are consistent with the established role of mucosal immunity in preventing viral entry and replication.1Russell M.W. Moldoveanu Z. Ogra P.L. Mestecky J. Mucosal immunity in COVID-19: a neglected but critical aspect of SARS-CoV-2 infection.Front Immunol. 2020; 11611337Crossref Scopus (138) Google Scholar Whereas intranasally administered SARS-CoV-2 vaccines have the potential to reduce viral transmission, demonstration of such effectiveness will have to await the final outcome of the ongoing clinical trials,10U.S. National Library of Medicine. ClinicalTrials.gov.https://clinicaltrials.gov/Date accessed: May 20, 2022Google Scholar a number of which are proceeding rapidly across several continents.10U.S. National Library of Medicine. ClinicalTrials.gov.https://clinicaltrials.gov/Date accessed: May 20, 2022Google Scholar The Center for Genetic Engineering and Biotechnology of Cuba is concluding clinical trials of an intranasal vaccine (CIBG-669) aimed at the SARS-CoV-2 RBD. Bharat Biotech International of India and the University of Hong Kong are advancing intranasal vaccines (BBV154 and DeINS1-nCoV-RBD LAIV) aimed at the SARS-CoV-2 RBD and SP, respectively. The University of Oxford (in collaboration with AstraZeneca) and Intravacc (Bilthoven, The Netherlands), for their part, are pursuing similarly targeted intranasal SARS-CoV-2 vaccines (ChAdOx1-S and CovOMV). US-based Altimmune, Meissa Vaccines, Codagenix, and Tetherex are heavily invested as well in the development of distinct intranasal SARS-CoV-2 vaccines (AdCOVID, MV-014-212, COVI-VAC, and SC-Ad6-1). In a departure from the aforementioned trials, the Laboratorio Avi-Mex of Mexico and the Icahn School of Medicine at Mount Sinai are exploring the utility of dual parenteral and intranasal administration of SARS-CoV-2 vaccines (AVX/COVID-12 and NDV-HXP-S, respectively). The above notwithstanding, consideration must also be given to the induction of mucosal immunity by parenterally administered SARS-CoV-2 vaccines. A compelling illustration of such functionality was afforded by Corbett et al11Corbett K.S. Flynn B. Foulds K.E. et al.Evaluation of the mRNA-1273 vaccine against SARS-CoV-2 in nonhuman primates.N Engl J Med. 2020; 383: 1544-1555Crossref PubMed Scopus (621) Google Scholar in the course of assessing the utility of the mRNA-1273 SARS-CoV-2 vaccine in nonhuman primates. The authors make note of the fact that “no viral replication was detectable in the nose” of any of the vaccinated animals in the wake of an upper airway challenge with SARS-CoV-2.12Corbett K.S. Edwards D.K. Leist S.R. et al.SARS-CoV-2 mRNA vaccine design enabled by prototype pathogen preparedness.Nature. 2020; 586: 567-571Crossref PubMed Scopus (601) Google Scholar Similar results were previously reported for the mouse model, wherein parenterally administered mRNA-1273 was found to “protect against SARS-CoV-2 infection … in the nose” as evident from the absence of any discernible immunopathologic changes.7Lei H. Alu A. Yang J. et al.Intranasal administration of a recombinant RBD vaccine induces long-term immunity against Omicron-included SARS-CoV-2 variants.Signal Transduct Target Ther. 2022; 7: 159Crossref PubMed Scopus (4) Google Scholar These reports stand out as apparent exceptions to an otherwise extensive body of observations wherein the parenteral vaccination route appears to have failed to engender mucosal immunity.1Russell M.W. Moldoveanu Z. Ogra P.L. Mestecky J. Mucosal immunity in COVID-19: a neglected but critical aspect of SARS-CoV-2 infection.Front Immunol. 2020; 11611337Crossref Scopus (138) Google Scholar Taken together, these observations lead one to conclude that mucosal immunity, as distinct from systemic immunity against SARS-CoV-2, represents a “neglected but critical aspect of SARS-CoV-2 infection.”1Russell M.W. Moldoveanu Z. Ogra P.L. Mestecky J. Mucosal immunity in COVID-19: a neglected but critical aspect of SARS-CoV-2 infection.Front Immunol. 2020; 11611337Crossref Scopus (138) Google Scholar Indications are that mucosal immunity should be emphasized in the development of future SARS-CoV-2 vaccines. It follows that future vaccination efforts could well focus on intranasal SARS-CoV-2 vaccines as an effective stand-alone approach or as an adjunct to their parenteral counterparts. Should intranasal vaccination prove effective in the absence of parenteral vaccination, the process of needle-free immunization could be carried out by lay personnel. Ideally suited for children, intranasal vaccines are bound to be welcome by the public at large as well. The same could be said for the developing world, wherein the logistic challenges of distribution and administration of parenterally administered vaccines have been difficult to surmount. Polio, after all, was all but eradicated worldwide courtesy of markedly simplified oral rather than parenteral vaccine administration. Whereas comparable predictions for the SARS-CoV-2 pandemic may be premature, a renewed focus on mucosal immunity appears paramount. It is in this context that intranasal vaccines could well fill a void heretofore unattended to. The SARS-CoV-2 parenteral vaccines currently in use, although highly effective at preventing hospitalization, severe disease, and death, are limited in their ability to prevent breakthrough infections and disease transmission. This is likely a consequence of their relative inability to induce mucosal immunity. This limitation of the parenteral vaccines can best be overcome by the development and implementation of an effective intranasal vaccine, one that could serve as either a stand-alone vaccine or an adjunct to parenteral vaccination.

Defective Humoral Immunity Disrupts Bile Acid Homeostasis which Promotes Inflammatory Disease of the Small Bowel

Abstract Mucosal antibodies maintain gut homeostasis by promoting spatial segregation between host tissues and luminal microbes. Whether and how mucosal antibody responses influence gut health through modulation of microbiota composition is unclear. Here, we use a CD19−/− mouse model of antibody-deficiency to demonstrate that a relationship exists between dysbiosis, defects in bile acid homeostasis, and gluten-sensitive enteropathy of the small intestine. The gluten-sensitive small intestine enteropathy that develops in CD19−/− mice is associated with alterations to luminal bile acid composition in the SI, marked by significant reductions in the abundance of conjugated bile acids. Manipulation of bile acid availability, adoptive transfer of functional B cells, and ablation of bacterial bile salt hydrolase activity all influence the severity of small intestine enteropathy in CD19−/− mice. Collectively, results from our experiments support a model whereby mucosal humoral immune responses limit inflammatory disease of the small bowel by regulating bacterial BA metabolism. J.L.K. was supported by a NIAID K22 Award (AI123481), a Jeffrey Modell Network Specific Diseases Research Award, a University of South Carolina ASPIRE-I Award, a pilot project award through the University of South Carolina Center for Alternative Medicine COBRE program (P20GM103641; awarded to Drs. Mitzi and Prakash Nagarkatti), an R21 (AI142409), and 1R01AI155887.

Heterologous prime-boost vaccination based on Polymorphic protein D protects against intravaginal Chlamydia trachomatis infection in mice

The control of the worldwide spread of sexually transmitted Chlamydia trachomatis (Ct) infection urgently demands the development of a preventive vaccine. In this work, we designed a vaccine based on a fragment of polymorphic protein D (FPmpD) that proved to be immunogenic enough to generate a robust systemic and mucosal IgG humoral immune response in two strains of mice. We used a heterologous prime-boost strategy, including simultaneous systemic and mucosal administration routes. The high titers of anti-PmpD antibodies elicited by this immunization scheme did not affect murine fertility. We tested the vaccine in a mouse model of Ct intravaginal infection. Anti-PmpD antibodies displayed potent neutralizing activity in vitro and protective effects in uterine tissues in vivo. Notably, the humoral immune response of PmpD-vaccinated mice was faster and stronger than the primary immune response of non-vaccinated mice when exposed to Ct. FPmpD-based vaccine effectively reduced Ct shedding into cervicovaginal fluids, bacterial burden at the genitourinary tract, and overall infectivity. Hence, the FPmpD-based vaccine might constitute an efficient tool to protect against Ct intravaginal infection and decrease the infection spreading.

Defective humoral immunity disrupts bile acid homeostasis which promotes inflammatory disease of the small bowel

Mucosal antibodies maintain gut homeostasis by promoting spatial segregation between host tissues and luminal microbes. Whether and how mucosal antibody responses influence gut health through modulation of microbiota composition is unclear. Here, we use a CD19−/− mouse model of antibody-deficiency to demonstrate that a relationship exists between dysbiosis, defects in bile acid homeostasis, and gluten-sensitive enteropathy of the small intestine. The gluten-sensitive small intestine enteropathy that develops in CD19−/− mice is associated with alterations to luminal bile acid composition in the SI, marked by significant reductions in the abundance of conjugated bile acids. Manipulation of bile acid availability, adoptive transfer of functional B cells, and ablation of bacterial bile salt hydrolase activity all influence the severity of small intestine enteropathy in CD19−/− mice. Collectively, results from our experiments support a model whereby mucosal humoral immune responses limit inflammatory disease of the small bowel by regulating bacterial BA metabolism.

Nasal and Salivary Mucosal Humoral Immune Response Elicited by mRNA BNT162b2 COVID-19 Vaccine Compared to SARS-CoV-2 Natural Infection.

SARS-CoV-2 antibody assays are crucial in managing the COVID-19 pandemic. Approved mRNA COVID-19 vaccines are well known to induce a serum antibody responses against the spike protein and its RBD. Mucosal immunity plays a major role in the fight against COVID-19 directly at the site of virus entry; however, vaccine abilities to elicit mucosal immune responses have not been reported. We detected anti-SARS-CoV-2 IgA-S1 and IgG-RBD in three study populations (healthy controls, vaccinated subjects, and subjects recovered from COVID-19 infection) on serum, saliva, and nasal secretions using two commercial immunoassays (ELISA for IgA-S1 and chemiluminescent assay for IgG-RBD). Our results show that the mRNA BNT162b2 vaccine Comirnaty (Pfizer/BioNTech, New York, NY, USA) determines the production of nasal and salivary IgA-S1 and IgG-RBD against SARS-CoV-2. This mucosal humoral immune response is stronger after the injection of the second vaccine dose compared to subjects recovered from COVID-19. Since there is a lack of validated assays on saliva and nasal secretions, this study shows that our pre-analytical and analytical procedures are consistent with the data. Our findings indicate that the mRNA COVID-19 vaccine elicits antigen-specific nasal and salivary immune responses, and that mucosal antibody assays could be used as candidates for non-invasive monitoring of vaccine-induced protection against viral infection.

A Single-Cycle Influenza A Virus-Based SARS-CoV-2 Vaccine Elicits Potent Immune Responses in a Mouse Model.

The use of virus-vectored platforms has increasingly gained attention in vaccine development as a means for delivering antigenic genes of interest into target hosts. Here, we describe a single-cycle influenza virus-based SARS-CoV-2 vaccine designated as scPR8-RBD-M2. The vaccine utilizes the chimeric gene encoding 2A peptide-based bicistronic protein cassette of the SARS-CoV-2 receptor-binding domain (RBD) and influenza matrix 2 (M2) protein. The C-terminus of the RBD was designed to link with the cytoplasmic domain of the influenza virus hemagglutinin (HA) to anchor the RBD on the surface of producing cells and virus envelope. The chimeric RBD-M2 gene was incorporated in place of the HA open-reading frame (ORF) between the 3′ and 5′ UTR of HA gene for the virus rescue in MDCK cells stably expressing HA. The virus was also constructed with the disrupted M2 ORF in segment seven to ensure that M2 from the RBD-M2 was utilized. The chimeric gene was intact and strongly expressed in infected cells upon several passages, suggesting that the antigen was stably maintained in the vaccine candidate. Mice inoculated with scPR8-RBD-M2 via two alternative prime-boost regimens (intranasal-intranasal or intranasal-intramuscular routes) elicited robust mucosal and systemic humoral immune responses and cell-mediated immunity. Notably, we demonstrated that immunized mouse sera exhibited neutralizing activity against pseudotyped viruses bearing SARS-CoV-2 spikes from various variants, albeit with varying potency. Our study warrants further development of a replication-deficient influenza virus as a promising SARS-CoV-2 vaccine candidate.

Defective Humoral Immunity Disrupts Bile Acid Homeostasis Which Promotes Inflammatory Disease of the Small Bowel

Abstract Mucosal antibodies maintain gut homeostasis by promoting spatial segregation between host tissues and luminal microbes. Whether and how mucosal antibody responses influence gut health through modulation of microbiota composition is unclear. One critical metabolic function carried out exclusively by bacteria in the gut is bio-transformation of host bile acids (BAs), and dysregulation of BAs metabolism has been linked to numerous inflammatory and metabolic diseases in humans. Here, we use a CD19−/− mouse model of antibody-deficiency to demonstrate that a relationship exists between dysbiosis, defects in BA homeostasis, and enteropathy of the small intestine (SI). SI enteropathy that develops in CD19−/− mice is associated with alterations to the luminal BA pool in the SI, marked by significant reductions in the abundance of conjugated BAs. Manipulation of BA availability, adoptive transfer of functional B cells, and ablation of bacterial bile salt hydrolase (bsh) activity all influence the severity of SI enteropathy in CD19−/− mice. Collectively, results from our experiments support a model whereby mucosal humoral immune responses limit inflammatory disease of the small bowel by regulating bacterial BA metabolism.

In vitro cell culture model of human nasal-associated lymphoid tissue (NALT) to evaluate the humoral immune response to SARS-CoV-2 spike proteins.

To date, coronavirus disease 2019 (COVID-19) continues to be considered a pandemic worldwide, with a mild to severe disease presentation that is sometimes associated with serious complications that are concerning to global health authorities. Scientists are working hard to understand the pathogenicity of this novel virus, and a great deal of attention and effort has been focused on identifying therapeutics and vaccines to control this pandemic.MethodsThis study used tonsils removed from twelve patients who underwent an elective tonsillectomy in the ear, nose, and throat (ENT) department at Saudi Germany Hospital, Madinah, Saudi Arabia. Tonsillar mononuclear cells (MNCs) were separated and co-cultured in RPMI complete medium in the presence and absence of viral spike (S) proteins (the full-length S, S1 subunit, and S2 subunit proteins). Enzyme-linked immunosorbent assay (ELISA) was used to measure secreted antibody concentrations following stimulation.ResultsThe in vitro human nasal-associated lymphoid tissue (NALT) cell culture model was successfully used to evaluate the humoral immune response against SARS-CoV-2- S protein. Significant (p < 0.0001, n = 12) levels of specific, anti-S IgG, IgM, and IgA antibody responses were detected in cells culture supernatanat folloeing stimulation with the full-length S protein compared with unstimulated cells. In contrast, S1 and S2 subunit proteins alone failed to induce a mucosal humoral immune response following tonsillar MNC stimulation.ConclusionWe demonstrated a successful human NALT in vitro cell culture model that was used to study the mucosal humoral immune response to the SARS-CoV-2 S protein. This model could be advantageous for the in-depth study of cellular immune responses to the S protein and other viral antigens, such as nucleocapsid and matrix antigen. The S protein appears to be the important viral protein that may be able to mimic the natural infection process intranasally and should be studied as a component of a candidate vaccine.

Molecular characterization of a novel aspartyl protease-1 from Trichinella spiralis

The aim of this study was to characterize the biological properties of a novel aspartic protease-1 from Trichinella spiralis (TsASP1) and evaluate its potential in inducing immune response. TsASP1 gene was cloned and expressed in Escherichia coli BL21 (DE3). On Western blotting analysis with anti-rTsASP1 serum, native TsASP1 was detected in various T. spiralis phases other than newborn larvae (NBL). qPCR results showed that TsASP1 transcription was the highest in intestinal infective larvae (IIL) and the lowest in the NBL stage. Immunofluorescence test result shows that native TsASP1 was principally localized in stichosome, muscle cells of muscle larvae (ML) and IIL, and surrounded intrauterine embryos in female adult worms (AW). After silencing TsASP1 gene of the ML by siRNA, the worm development was significantly inhibited, showed by shorter AW and more wrinkles and longitudinal crack on epicuticle of AW on scanning electron microscopy; the AW and ML burdens were reduced by 41.82 and 56.36% respectively, compared with the control siRNA or PBS group (P < 0.001). Immunization of mice with rTsASP1 elicited an evident antibody response (serum IgG, IgG1/IgG2a and enteral sIgA), and systemic (spleen) and intestinal local mucosal (mesenteric lymph node) cellular immune response, demonstrated by a prominent elevation of IFN-γ and IL-4. The results suggested TsASP1 participated in T. spiralis development and survival in host, and immunization of mice with rTsASP1 induced systemic/intestinal local mucosal humoral and cellular immune response against Trichinella.