IgG Antibody Responses Research Articles

Immunogenicity of PE18, PE31, and PPE26 proteins from Mycobacterium tuberculosis in humans and mice.

The large family of PE and PPE proteins accounts for as much as 10% of the genome of Mycobacterium tuberculosis. In this study, we explored the immunogenicity of three proteins from this family, PE18, PE31, and PPE26, in humans and mice. The investigation involved analyzing the immunoreactivity of the selected proteins using sera from TB patients, IGRA-positive household contacts, and IGRA-negative BCG vaccinated healthy donors from the TB endemic country Mozambique. Antigen-recall responses were examined in PBMC from these groups, including the evaluation of cellular responses in healthy unexposed individuals. Moreover, systemic priming and intranasal boosting with each protein, combined with the Quil-A adjuvant, were conducted in mice. We found that all three proteins are immunoreactive with sera from TB patients, IGRA-positive household contacts, and IGRA-negative BCG vaccinated healthy controls. Likewise, antigen-recall responses were induced in PBMC from all groups, and the proteins stimulated proliferation of peripheral blood mononuclear cells from healthy unexposed individuals. In mice, all three antigens induced IgG antibody responses in sera and predominantly IgG, rather than IgA, responses in bronchoalveolar lavage. Additionally, CD4+ and CD8+ effector memory T cell responses were observed in the spleen, with PE18 demonstrating the ability to induce tissue-resident memory T cells in the lungs. Having demonstrated immunogenicity in both humans and mice, the protective capacity of these antigens was evaluated by challenging immunized mice with low-dose aerosol of Mycobacterium tuberculosis H37Rv. The in vitro Mycobacterial Growth Inhibition Assay (MGIA) and assessment of viable bacteria in the lung did not demonstrate any ability of the vaccination protocol to reduce bacterial growth. We therefore concluded that these three specific PE/PPE proteins, while immunogenic in both humans and mice, were unable to confer protective immunity under these conditions.

The inflammasome‐related ASC‐speck is a microglial danger signal and therapeutic target for vaccine development to address neuroinflammation

AbstractBackgroundAmyloidβ plaques and tau neurofibrillary tangles are the primary pathological components of Alzheimer’s disease. In response to these danger‐associated molecular patterns, microglia assemble a multiprotein complex called the inflammasome that drives chronic neuroinflammation. The inflammasome is composed of the NACHT, LRR, and PYD domain‐containing protein 3 (NLRP3); apoptosis‐associated speck‐like protein containing a CARD (ASC); and inflammatory caspase‐1. The fully assembled inflammasome results in the activation of caspase‐1 which promotes the maturation of the inflammatory cytokine IL‐1β. The ASC‐speck, a supramolecular complex of activated inflammasome proteins, is secreted into the extracellular space during an inflammatory cell‐death process and is capable of propagating inflammation and cross‐seeding amyloid beta in a prion‐like fashion. Our recent study in a small patient cohort detected ASC‐specks in the cerebrospinal fluid of patients with tauopathies. It is unknown how microglia respond to extracellular ASC‐specks or if ASC‐specks could be therapeutically targeted through a vaccination strategy. We hypothesize that ASC‐specks behave as a danger‐associated molecular pattern to promote microglial inflammation and that neutralizing antibody responses against ASC in response to an active vaccine strategy could reduce inflammatory signaling in the central nervous system.MethodPrimary murine microglia were stimulated with purified ASC‐specks. The release of proinflammatory cytokines and chemokines were measured using a MesoScale Discovery pro‐inflammatory panel. Vaccines against ASC were synthesized using a Qβ virus‐like particle (VLP) platform conjugated to ASC peptide epitopes and used to vaccinate non‐transgenic mice for safety profile, immunogenicity, and efficacy characterization. Intraperitoneal lipopolysaccharide (LPS) injection was used to induce systemic inflammation in vaccinated mice and inflammasome activity and tau phosphorylation were measured by Western blot to assess vaccine efficacy.ResultUpon exposure to ASC‐specks, microglia release significantly higher levels of TNFα, CXCL1, and IL6 compared to control, indicative of a proinflammatory phenotype. ASC‐VLP vaccines are safe in non‐transgenic mice, elicit high‐titer IgG antibody responses against ASC, and reduce hippocampal inflammasome proteins and tau phosphorylation in response to LPS stimulation.ConclusionExtracellularly released ASC‐specks have the ability to induce an inflammatory microglial response. Neutralization of microglial ASC‐specks using a systemic active vaccine strategy can mitigate neuroinflammation in the brain parenchyma in response to inflammatory stimuli.

The gift of preexisting immunity for developing an alternative vaccine strategy.

Despite the worldwide application of vaccination and other antiviral interventions, pulmonary viral infections remain a persistent threat to human health. The 1918 influenza pandemic killed more than 40 million people in just one year, and the SARS-CoV-2 pandemic has killed more than 6.9 million people since 2019. While the current approved COVID-19 vaccines are administered parenterally and induce systemic immunity, they only prevent the progression to severe disease. Thus, other vaccine platforms are still needed for completely preventing the disease and subsequent transmission. In this issue of the JCI, Kawai et al. present an adjuvant-free subunit (RBD-HA) fusion vaccine, which produces robust IgG and IgA antibody responses against SARS-CoV-2, enriched within the nasal cavity, by using the host's preexisting immunity to influenza infection. This preclinical study has tremendous implications for future mucosal vaccine design and provides a roadmap for generating a safer and effective intranasal vaccine against pulmonary infections.

Humoral and T cell responses to SARS-CoV-2 reveal insights into immunity during the early pandemic period in Pakistan

BackgroundProtection against SARS-CoV-2 is mediated by humoral and T cell responses. Pakistan faced relatively low morbidity and mortality from COVID-19 through the pandemic. To examine the role of prior immunity in the population, we studied IgG antibody response levels, virus neutralizing activity and T cell reactivity to Spike protein in a healthy control group (HG) as compared with COVID-19 cases and individuals from the pre-pandemic period (PP).MethodsHG and COVID-19 participants were recruited between October 2020 and May 2021. Pre-pandemic sera was collected before 2018. IgG antibodies against Spike and its Receptor Binding Domain (RBD) were determined by ELISA. Virus neutralization activity was determined using a PCR-based micro-neutralization assay. T cell – IFN-γ activation was assessed by ELISpot.ResultsOverall, the magnitude of anti-Spike IgG antibody levels as well as seropositivity was greatest in COVID-19 cases (90%) as compared with HG (39.8%) and PP (12.2%). During the study period, Pakistan experienced three COVID-19 waves. We observed that IgG seropositivity to Spike in HG increased from 10.3 to 83.5% during the study, whilst seropositivity to RBD increased from 7.5 to 33.3%. IgG antibodies to Spike and RBD were correlated positively in all three study groups. Virus neutralizing activity was identified in sera of COVID-19, HG and PP. Spike reactive T cells were present in COVID-19, HG and PP groups. Individuals with reactive T cells included those with and without IgG antibodies to Spike.ConclusionsAntibody and T cell responses to Spike protein in individuals from the pre-pandemic period suggest prior immunity against SARS-CoV-2, most likely from cross-reactive responses. The rising seroprevalence observed in healthy individuals through the pandemic without known COVID-19 may be due to the activation of adaptive immunity from cross-reactive memory B and T cells. This may explain the more favourable COVID-19 outcomes observed in this population.

Oral Immunization with Attenuated Salmonella Choleraesuis Expressing the FedF Antigens Protects Mice against the Shiga-Toxin-Producing Escherichia coli Challenge.

Edema disease (ED) is a severe and lethal infectious ailment in swine, stemming from Shiga-toxin-producing Escherichia coli (STEC). An efficient, user-friendly, and safe vaccine against ED is urgently required to improve animal welfare and decrease antibiotic consumption. Recombinant attenuated Salmonella vaccines (RASV) administered orally induce both humoral and mucosal immune responses to the immunizing antigen. Their potential for inducing protective immunity against ED is significant through the delivery of STEC antigens. rSC0016 represents an enhanced recombinant attenuated vaccine vector designed for Salmonella enterica serotype Choleraesuis. It combines sopB mutations with a regulated delay system to strike a well-balanced equilibrium between host safety and immunogenicity. We generated recombinant vaccine strains, namely rSC0016 (pS-FedF) and rSC0016 (pS-rStx2eA), and assessed their safety and immunogenicity in vivo. The findings demonstrated that the mouse models immunized with rSC0016 (pS-FedF) and rSC0016 (pS-rStx2eA) generated substantial IgG antibody responses to FedF and rStx2eA, while also provoking robust mucosal and cellular immune responses against both FedF and rStx2eA. The protective impact of rSC0016 (pS-FedF) against Shiga-toxin-producing Escherichia coli surpassed that of rSC0016 (pS-rStx2eA), with percentages of 83.3%. These findings underscore that FedF has greater suitability for vaccine delivery via recombinant attenuated Salmonella vaccines (RASVs). Overall, this study provides a promising candidate vaccine for infection with STEC.

Study of the Immunogenicity of Combination of Recombinant RBD (Omicron) and Nucleocapsid Proteins of SARS-CoV-2 Expressed in Pichia Pastoris

Background: SARS-CoV-2 is a virus responsible for the COVID-19 pandemic that began in late 2019. This pandemic has had a devastating impact worldwide, resulting in over 6.95 million deaths. The development of effective vaccines against the virus is crucial for preventing infection and reducing the severity of the disease. Objective: This study aimed to obtain the recombinant receptor-binding domain (RBD) and the nucleocapsid (N) proteins of SARS-CoV-2 as well as assess the immunogenicity of the combination of these recombinant proteins. Methods: The recombinant plasmids encoding the receptor-binding domain (RBD) of the spike protein of the Omicron variant and the nucleocapsid protein of SARS-CoV-2 were cloned into the yeast Pichia pastoris. The optimal fermentation conditions were established for recombinant P. pastoris strains. The methods for the isolation and purification of the target recombinant RBD and nucleocapsid proteins were developed. The immunogenicity of the purified recombinant proteins was evaluated by injecting them into mice and analyzing the specific IgG antibody responses using ELISA. Results: The study found that RBD and N proteins, as well as their combination, showed antigenic specificity and were highly immunogenic in mice. The immunogenicity was measured by determining the antibody titer, which represents the concentration of antibodies produced in response to the antigen. The antibody titers were 1:60000 for both RBD and N proteins, and 1:80000 for their combination. Conclusion: These findings suggest that the expressed proteins could be potential candidates for the development of vaccines or immunological diagnostic test kits for combatting or detecting the Omicron variant of SARS-CoV-2.

1169. Unconjugated Multi-epitope Peptides Adjuvanted with ALFQ Induce Durable and Broadly Reactive Antibodies to Human and Avian Influenza Viruses

Abstract Background Traditional influenza vaccine production often leads to mismatch due to antigenic drift, thereby reducing protection. Alternate vaccine strategies that are peptide-based, nanoparticle-based or nucleic acid-based are being developed. Composite multi-epitope peptides provide a cost-effective and easily scalable strategy towards a universal influenza vaccine. In this study, we demonstrate that unconjugated, multi-epitope peptides formulated with the highly potent adjuvant Army Liposome Formulation with QS-21 (ALFQ) generate broadly reactive durable antibodies to human and avian influenza viruses when administered intramuscularly or intradermally. Methods ICR mice were immunized with an unconjugated composite influenza peptide vaccine comprising HA+NA (Flu Pep11) and Matrix (M1/M2/M2e)+T-cell epitope (Flu Pep5906) formulated with ALFQ. A low-dose (1 µg) and high-dose (20 µg) of vaccine was administered intramuscularly or intradermally. Isotype-specific IgG titers to composite peptides, individual epitopes, and multiple strains of influenza A (H1N1, H3N2, H5N1), and B (Yamagata, Victoria) were analyzed by ELISA. Neutralizing titers against Group 1 and Group 2 viruses were determined using microneutralization assay. Results A robust IgG1 and IgG2b antibody response was seen at day 21 post primary immunization and remained steady for all groups up to day 200 (duration of study). IgG2a and IgG3 titers were also generated. Antibodies recognized multiple strains each of human and avian influenza A and influenza B virus subtypes, 200 days post primary immunization, and were comparable between doses and routes. Strong neutralizing titers were shown against Group 1 and 2 influenza viruses. Conclusion An unconjugated peptide vaccine comprising multiple highly conserved epitopes of HA, NA and Matrix formulated with ALFQ adjuvant and administered intramuscularly or intradermally, generated broad and durable antibodies to human and avian influenza viruses. Induced antibodies neutralized seasonal and pandemic influenza strains. These composite peptides adjuvanted with ALFQ generate durable and broad immunity and provide a cost-effective and easily scalable strategy that moves us closer to a universal influenza vaccine. Disclosures All Authors: No reported disclosures

Adoptive transfer of allergen-expressing B cells prevents IgE-mediated allergy.

Prophylactic strategies to prevent the development of allergies by establishing tolerance remain an unmet medical need. We previously reported that the transfer of autologous hematopoietic stem cells (HSC) expressing the major timothy grass pollen allergen, Phl p 5, on their cell surface induced allergen-specific tolerance in mice. In this study, we investigated the ability of allergen-expressing immune cells (dendritic cells, CD4+ T cells, CD8+ T cells, and CD19+ B cells) to induce allergen-specific tolerance in naive mice and identified CD19+ B cells as promising candidates for allergen-specific cell therapy. For this purpose, CD19+ B cells were isolated from Phl p 5-transgenic BALB/c mice and transferred to naive BALB/c mice, pre-treated with a short course of rapamycin and an anti-CD40L antibody. Subsequently, the mice were subcutaneously sensitized three times at 4-week intervals to Phl p 5 and Bet v 1 as an unrelated control allergen. Allergen-expressing cells were followed in the blood to monitor molecular chimerism, and sera were analyzed for Phl p 5- and Bet v 1-specific IgE and IgG1 levels by RBL assay and ELISA, respectively. In vivo allergen-induced lung inflammation was measured by whole-body plethysmography, and mast cell degranulation was determined by skin testing. The transfer of purified Phl p 5-expressing CD19+ B cells to naive BALB/c mice induced B cell chimerism for up to three months and prevented the development of Phl p 5-specific IgE and IgG1 antibody responses for a follow-up period of 26 weeks. Since Bet v 1 but not Phl p 5-specific antibodies were detected, the induction of tolerance was specific for Phl p 5. Whole-body plethysmography revealed preserved lung function in CD19+ B cell-treated mice in contrast to sensitized mice, and there was no Phl p 5-induced mast cell degranulation in treated mice. Thus, we demonstrated that the transfer of Phl p 5-expressing CD19+ B cells induces allergen-specific tolerance in a mouse model of grass pollen allergy. This approach could be further translated into a prophylactic regimen for the prevention of IgE-mediated allergy in humans.

Association of Viral Control and Maternal Antibody Titers in Congenital Zika Virus Infection

Abstract Background Exposure to Zika virus (ZIKV) in utero can result in a wide spectrum of outcomes, ranging from asymptomatic to severe neurological defects or fetal demise. The presence of virus in the fetus or in the mother’s blood for a prolonged period of time may lead to worse outcomes, which means that limiting the duration of fetal exposure to virus may improve outcomes. One factor that may be related to control of maternal viremia and presence of virus in the fetus is the maternal IgG antibody response. We utilized a rhesus macaque model of prenatal ZIKV to quantify the viral RNA present in the maternal blood and maternal-fetal interface (MFI) tissues and determine the association of viral RNA loads with maternal IgG antibody titers over time. Methods Dams were infected with either African lineage ZIKV-DAKAR (n=9) or Asian lineage ZIKV-PRVABC59 (PR, n=10) isolate in the first trimester, then all fetal and MFI tissues were removed either 7 or 14 days post-infection (dpi) and viral RNA loads were measured. Maternal plasma was tested for viral RNA and IgG throughout pregnancy. Results A greater proportion of animals infected with the DAKAR isolate had viral RNA present in the MFI tissues compared with the animals infected with the PR isolate, at both 7 and 14 dpi. DAKAR animals also tested positive for ZIKV-specific IgG at 14 dpi or earlier, while IgG was typically negative at 14 dpi for PR animals. Viral RNA was detected in the fetal and MFI tissues in a higher proportion of dams that still had ZIKV RNA positive plasma at 14 dpi had viral RNA. We found no difference in IgG antibody titers between dams that were ZIKV positive or negative at 14 dpi. Conclusions The presence of ZIKV in the MFI tissues and earlier detection of ZIKV-specific maternal IgG responses were both associated with the DAKAR isolate, suggesting that it may be a more virulent isolate. A higher proportion of dams that had virus in their plasma at 14 dpi also had virus present in the fetal and MFI tissues, but there was no difference in long term IgG response within either isolate between animals that tested positive or negative at 14 dpi. This suggests that the dam clearing viral RNAfrom their plasma by 14 dpi may impact whether or not the virus infects the MFI tissues, but that maternal IgG response likely does not play a role in this difference.

Transient hypogammaglobulinemia of infancy and unclassified syndromic immunodeficiencies are highly common in oesophageal atresia patients.

Due to the high rate of post-operative sepsis and other infectious complications, a routine immunological screening protocol has been initiated since 2015 in our paediatric surgery clinic for all patients admitted with oesophageal atresia (EA) and warrant a delayed definitive treatment. In our study, we aimed to evaluate the immunodeficiencies in EA patients, by comparing them to healthy age-matched controls. As a prospective cohort study, EA patients admitted between 2015 and 2022, who had their definitive operation after the newborn period (>28 days of age) were included. On admission, serum concentrations of IgG, IgA, IgM, lymphocyte subset levels, C3 and C4 levels, specific IgG antibody responses against hepatitis B, hepatitis A, measles, varicella zoster were evaluated. The patients were age-matched with healthy controls to compare the results and followed up until three years of age. If a humoral immunodeficiency was detected, intravenous immunoglobulin treatment was administered before major oesophageal surgery and during follow-up. 31 EA patients (18 M/13F) with a mean age of 13.3 ± 9.0 months were compared with 40 age-matched healthy controls. Mean serum IgG levels were found to be statistically lower than controls in all age groups (P < .05). Transient hypogammaglobulinemia of infancy (THI) and unclassified syndromic immunodeficiencies (USI) were found to be strikingly high, accounting for 29.0% and 22.5%, respectively, adding up to 51.5% of EA patients. This is the first study evaluating immunodeficiencies in EA patients found in the reviewed literature. More than half of EA patients that required delayed surgery had humoral immunodeficiency, so preoperative screening and immunology referral may improve patient outcomes.

Multi-antigen pan-sarbecovirus DNA vaccines generate protective T cell immune responses.

SARS-CoV-2 is the third zoonotic coronavirus to cause a major outbreak in humans in recent years, and many more SARS-like coronaviruses with pandemic potential are circulating in several animal species. Vaccines inducing T cell immunity against broadly conserved viral antigens may protect against hospitalisation and death caused by outbreaks such viruses. We report the design and pre-clinical testing of two T-cell-based pan-sarbecovirus vaccines, based on conserved regions within viral proteins of sarbecovirus isolates of human and other carrier animals, like bats and pangolins. One vaccine (CoVAX_ORF1ab) encoded antigens derived from non-structural proteins, the other (CoVAX_MNS) antigens from structural proteins. Both multi-antigen DNA vaccines contained a large set of antigens shared across sarbecoviruses and were rich in predicted and experimentally validated human T cell epitopes. In mice, the multi-antigen vaccines generated both CD8 and CD4 T cell responses to shared epitopes. Upon encounter of full-length spike antigen, CoVAX_MNS-induced CD4 T cells were responsible for accelerated CD8 T cell and IgG antibody responses specific to the incoming spike, irrespective of its sarbecovirus origin. Finally, both vaccines elicited partial protection against a lethal SARS-CoV-2 challenge in human-ACE2-transgenic mice. These results support clinical testing of this universal sarbecovirus vaccine for pandemic preparedness.

Serial evaluation of antibody titres in patients recovered from COVID-19 and their correlation with disease severity.

On March 11, 2020, the World Health Organization (WHO) declared COVID-19 a pandemic. According to the findings of various studies conducted around the world, the serological response varies greatly among different populations, with the determinants of variable response still unknown, including the role of disease severity, which is thought to have a definite correlation. The purpose of this study was to assess serial SARS-CoV-2 IgG antibody response in COVID-19 patients and correlate it with disease severity. It was a longitudinal observational study in which 45 patients (age >18 yrs), were enrolled who had recovered from COVID-19 and were reporting to the post-COVID Care OPD Clinic. Patients who had been on long-term immunosuppressive therapy prior to SARS-CoV-2 infection were not eligible. All patients had not been immunized against SARS-CoV-2 and had no history of contact with recent COVID-19 cases. The patients underwent serial blood tests to determine serum IgG titers specific for SARS-CoV-2 at 30, 60, and 90 days after being diagnosed with COVID-19. Chemiluminescence was used to perform a semi-quantitative evaluation of the SARS-CoV-2 IgG antibody. At 30 days after confirmed SARS-CoV-2 infection, 98.78% had detectable serum IgG levels, and sero-reversion (loss of previously detectable antibodies) occurred in 2.5% at 60 days and 90 days. Serum IgG was found to peak at 30 days out of the three time points of measurement (30, 60, and 90 days from diagnosis). Serum IgG levels at 90 days were significantly lower than those at 30 days (p<0.0001) and 60 days (p=0.002). The current study's findings shed light on the presence and persistence of serum SARS-CoV-2-specific IgG antibodies following a natural infection. The findings point to a long-lasting immune response with increasing severity of initial COVID-19 disease.

The Time-Dependent Association of Torque Teno Virus Load with the Level of SARS-CoV-2 S1 IgG Antibodies Following COVID-19 Vaccination in Kidney Transplant Recipients.

Kidney transplant recipients (KTR) show an impaired humoral immune response to COVID-19 vaccination due to their immunocompromised status. Torque teno virus (TTV) is a possible marker of immune function. This marker may be helpful in predicting the immune response after COVID-19 vaccination in order to decide which vaccination strategy should be applied. We therefore investigated whether TTV load is associated with the humoral response after COVID-19 vaccination. Of the KTR who participated in two prospective vaccination studies and received two to four doses of the mRNA-1273 COVID-19 vaccine, 122 were included. TTV load was measured prior to vaccination, and S1 IgG antibody levels were measured 28 days after vaccination. TTV load was independently inversely associated with S1 IgG antibodies after COVID-19 vaccination (B: -2.19 (95% CI: -3.6--0.8), p = 0.002). Interestingly, we found a significant interaction between TTV load and time after transplantation (p = 0.005). When patients were longer after transplantation, TTV load was less predictive for S1 IgG antibody response after vaccination compared to patients that were shorter after transplantation. Our data suggest that TTV load is a good marker in predicting COVID-19 vaccination antibody response and may be helpful in selecting a strategy shortly after transplantation. However, this marker should be handled with caution longer after transplantation.

Stereoselective Synthesis of Sialyl Lewisa Antigen and the Effective Anticancer Activity of Its Bacteriophage Qβ Conjugate as an Anticancer Vaccine

AbstractSialyl Lewisa (sLea), also known as cancer antigen 19‐9 (CA19‐9), is a tumor‐associated carbohydrate antigen. The overexpression of sLea on the surface of a variety of cancer cells makes it an attractive target for anticancer immunotherapy. However, sLea‐based anticancer vaccines have been under‐explored. To develop a new vaccine, efficient stereoselective synthesis of sLea with an amine‐bearing linker was achieved, which was subsequently conjugated with a powerful carrier bacteriophage, Qβ. Mouse immunization with the Qβ‐sLea conjugate generated strong and long‐lasting anti‐sLea IgG antibody responses, which were superior to those induced by the corresponding conjugate of sLea with the benchmark carrier keyhole limpet hemocyanin. Antibodies elicited by Qβ‐sLea were highly selective toward the sLea structure, could bind strongly with sLea‐expressing cancer cells and human pancreatic cancer tissues, and kill tumor cells through complement‐mediated cytotoxicity. Furthermore, vaccination with Qβ‐sLea significantly reduced tumor development in a metastatic cancer model in mice, demonstrating tumor protection for the first time by a sLea‐based vaccine, thus highlighting the significant potential of sLea as a promising cancer antigen.

Stereoselective Synthesis of Sialyl Lewisa Antigen and the Effective Anticancer Activity of Its Bacteriophage Qβ Conjugate as an Anticancer Vaccine.

Sialyl Lewisa (sLea ), also known as cancer antigen 19-9 (CA19-9), is a tumor-associated carbohydrate antigen. The overexpression of sLea on the surface of a variety of cancer cells makes it an attractive target for anticancer immunotherapy. However, sLea -based anticancer vaccines have been under-explored. To develop a new vaccine, efficient stereoselective synthesis of sLea with an amine-bearing linker was achieved, which was subsequently conjugated with a powerful carrier bacteriophage, Qβ. Mouse immunization with the Qβ-sLea conjugate generated strong and long-lasting anti-sLea IgG antibody responses, which were superior to those induced by the corresponding conjugate of sLea with the benchmark carrier keyhole limpet hemocyanin. Antibodies elicited by Qβ-sLea were highly selective toward the sLea structure, could bind strongly with sLea -expressing cancer cells and human pancreatic cancer tissues, and kill tumor cells through complement-mediated cytotoxicity. Furthermore, vaccination with Qβ-sLea significantly reduced tumor development in a metastatic cancer model in mice, demonstrating tumor protection for the first time by a sLea -based vaccine, thus highlighting the significant potential of sLea as a promising cancer antigen.

Vaccination against tick-borne encephalitis elicits a detectable NS1 IgG antibody response

Vaccine-induced protection against tick-borne encephalitis virus (TBEV) is mediated by antibodies to the viral particle/envelope protein. The detection of non-structural protein 1 (NS1) specific antibodies has been suggested as a marker indicative of natural infections. However, recent work has shown that TBEV vaccines contain traces of NS1, and immunization of mice induced low amounts of NS1-specific antibodies. In this study, we investigated if vaccination induces TBEV NS1-specific antibodies in humans. Healthy army members (n = 898) were asked to fill in a questionnaire relating to flavivirus vaccination or infection, and blood samples were collected. In addition, samples of 71 suspected acute TBE cases were included. All samples were screened for the presence of TBEV NS1-specific IgG antibodies using an in-house developed ELISA. Antibodies were quantified as percent positivity in reference to a positive control. For qualitative evaluation, cut-off for positivity was defined based on the mean OD of the lower 95% of the vaccinated individuals + 3 SD. We found significantly higher NS1-specific IgG antibody titers (i.e., quantitative evaluation) in individuals having received 2, 3, or 4 or more vaccine doses than in non-vaccinated individuals. Similarly, the percentage of individuals with a positive test result (i.e., qualitative evaluation) was higher in individuals vaccinated against tick-borne encephalitis than in unvaccinated study participants. Although NS1-specific IgG titers remained at a relatively low level when compared to TBE patients, a clear distinction was not always possible. Establishing a clear cut-off point in detection systems is critical for NS1-specific antibodies to serve as a marker for distinguishing the immune response after vaccination and infection.

Phase II, Safety and Immunogenicity of RAZI Cov Pars (RCP) SARS Cov-2 Vaccine in Adults Aged 18–70 Years; A Randomized, Double-Blind Clinical Trial

BackgroundThis study explores the safety and immunogenicity of the Razi-Cov-Pars (RCP) SARS Cov-2 recombinant spike protein vaccine. MethodIn a randomized, double-blind, placebo-controlled trial, adults aged 18–70 were randomly allocated to receive selected 10 µg/200 µl vaccine strengths or placebo (adjuvant). It included two intramuscular injections at days 0 and 21, followed by an intranasal dose at day 51. Immediate and delayed solicited local and systemic adverse reactions after each dose up to a week, and specific IgG antibodies against SARS Cov-2 spike antigens two weeks after the 2nd dose were assessed as primary outcomes. Secondary safety outcomes were abnormal laboratory findings and medically attended adverse events (MAAE) over six months follow up. Secondary immunogenicity outcomes were neutralizing antibody activity and cell-mediated immune response. ResultBetween May 27th and July 15th, 2021, 500 participants were enrolled. Participants' mean (SD) age was 37.8 (9.0), and 67.0 % were male. No immediate adverse reaction was observed following the intervention. All solicited local and systemic adverse events were moderate (Grade I-II). Specific IgG antibody response against S antigen in the vaccine group was 5.28 times (95 %CI: 4.02–6.94) the placebo group with a 75 % seroconversion rate. During six months of follow-up, 8 SAEs were reported, unrelated to the study intervention. The participants sustained their acquired humoral responses at the end of the sixth month. The vaccine predominantly resulted in T-helper 1 cell-mediated immunity, CD8+ cytotoxic T-cell increase, and no increase in inflammatory IL-6 cytokine. ConclusionRCP vaccine is safe and creates strong and durable humoral and cellular immunity. Trial registration(IRCT20201214049709N2).

Control of maternal Zika virus infection during pregnancy is associated with lower antibody titers in a macaque model.

Zika virus (ZIKV) infection during pregnancy results in a spectrum of birth defects and neurodevelopmental deficits in prenatally exposed infants, with no clear understanding of why some pregnancies are more severely affected. Differential control of maternal ZIKV infection may explain the spectrum of adverse outcomes. Here, we investigated whether the magnitude and breadth of the maternal ZIKV-specific antibody response is associated with better virologic control using a rhesus macaque model of prenatal ZIKV infection. We inoculated 18 dams with an Asian-lineage ZIKV isolate (PRVABC59) at 30-45 gestational days. Plasma vRNA and infectious virus kinetics were determined over the course of pregnancy, as well as vRNA burden in the maternal-fetal interface (MFI) at delivery. Binding and neutralizing antibody assays were performed to determine the magnitude of the ZIKV-specific IgM and IgG antibody responses throughout pregnancy, along with peptide microarray assays to define the breadth of linear ZIKV epitopes recognized. Dams with better virologic control (n= 9) cleared detectable infectious virus and vRNA from the plasma by 7 days post-infection (DPI) and had a lower vRNA burden in the MFI at delivery. In comparison, dams with worse virologic control (n= 9) still cleared detectable infectious virus from the plasma by 7 DPI but had vRNA that persisted longer, and had higher vRNA burden in the MFI at delivery. The magnitudes of the ZIKV-specific antibody responses were significantly lower in the dams with better virologic control, suggesting that higher antibody titers are not associated with better control of ZIKV infection. Additionally, the breadth of the ZIKV linear epitopes recognized did not differ between the dams with better and worse control of ZIKV infection. Thus, the magnitude and breadth of the maternal antibody responses do not seem to impact maternal virologic control. This may be because control of maternal infection is determined in the first 7 DPI, when detectable infectious virus is present and before robust antibody responses are generated. However, the presence of higher ZIKV-specific antibody titers in dams with worse virologic control suggests that these could be used as a biomarker of poor maternal control of infection and should be explored further.

Cell-mediated and Neutralizing Antibody Responses to the SARS-CoV-2 Omicron BA.4/BA.5-adapted Bivalent Vaccine Booster in Kidney and Liver Transplant Recipients.

The immunogenicity elicited by the Omicron BA.4/BA.5-adapted bivalent booster vaccine after solid organ transplantation (SOT) has not been characterized. We assessed cell-mediated and neutralizing IgG antibody responses against the BA.4/BA.5 spike receptor-binding domain at baseline and 2 wk after the administration of an mRNA-based bivalent (ancestral strain and BA.4/BA.5 subvariants) vaccine among 30 SOT recipients who had received ≥3 monovalent vaccine doses. Previous coronavirus disease 2019 history was present in 46.7% of them. We also recruited a control group of 19 nontransplant healthy individuals. Cell-mediated immunity was measured by fluorescent ELISpot assay for interferon (IFN)-γ secretion, whereas the neutralizing IgG antibody response against the BA.4/BA.5 spike receptor-binding domain was quantified with a competitive ELISA. The median number of BA.4/BA.5 spike-specific IFN-γ-producing spot-forming units (SFUs) increased from baseline to 2 wk postbooster (83.8 versus 133.0 SFUs/106 peripheral blood mononuclear cells; P = 0.0017). Seropositivity rate also increased (46.7%-83.3%; P = 0.001), as well as serum neutralizing activity (4.2%-78.3%; P < 0.0001). Patients with no prior coronavirus disease 2019 history experienced higher improvements in cell-mediated and neutralizing responses after booster vaccination. There was no correlation between BA.4/BA.5 spike-specific IFN-γ-producing SFUs and neutralizing activity. Nontransplant controls showed more robust postbooster cell-mediated immunity than SOT recipients (591.1 versus 133.0 IFN-γ-producing SFUs/106 peripheral blood mononuclear cells; P < 0.0001), although no differences were observed for antibody responses in terms of postbooster seropositivity rates or neutralizing activity. Booster with the BA.4/BA.5-adapted bivalent vaccine generated strong subvariant-specific responses among SOT recipients. Booster-induced cell-mediated immunity, however, remained lower than in immunocompetent individuals.

Measuring anti-spike IgG Antibody Response to SARS-CoV-2 vaccination in Patients Receiving Hemodialysis in Pakistan

The current state of the evidence is equivocal for IgG antibody response to SARS-CoV-2 vaccination in hemodialysis patients. Here, we assess the immune response in hemodialysis patients who have received a complete series of vaccines with or without a history of prior COVID infection irrespective of the vaccine administered. In this cross-sectional study, we obtained serum samples from Hemodialysis patients (n = 101). Our study found that nearly three-quarters of patients (72.2%) had two doses of either Sinovac or Sinopharm vaccine administered, and ninety-seven percent of participants were considered seropositive (COVID Ab titers &gt; 7.1 BAU/ml). Mean COVID19 spike antibody titers were 1892.4 BAU/mL and median titers were 971 BAU/mL. The comparative analysis was performed between patients who completed two-doses less than 6 months ago and more than 6 months ago when their antibody levels were measured. Mean and median antibody titers were 1895.8 and 792 BAU/mL in the former group compared to 1981.1 and 1033 BAU/mL respectively (P value 0.84) in the latter group, indicating no significant difference. There were also no statistically significant differences in IgG antibodies among subgroups defined by diabetes, hypertension, CAD or gender. However, older patients (age &gt;55 years) had significantly higher anti-spike antibody titers as compared to younger patients (2417.8 BAU/mL vs 1377.3 BAU/mL, P value 0.008). The result of this study provides important evidence, which can lead to vaccine efficacy especially in older populations. Future studies should address whether booster vaccination may play a role in providing an effective and long-lasting protection among vulnerable patients undergoing hemodialysis treatment.