Effective Vaccine Response Research Articles

IFN-λ drives distinct lung immune landscape changes and antiviral responses in human metapneumovirus infection.

Human metapneumovirus (HMPV) is a common respiratory pathogen and often contributes to severe disease, particularly in children, immunocompromised people, and the elderly. There are currently no licensed HMPV antiviral treatments or vaccines. Here, we report novel roles of host factor IFN-λ in HMPV disease that highlight therapeutic potential. We show that IFN-λ promotes lung antiviral responses by restricting lung HMPV replication and spread from upper to lower airways but does so without inducing lung immunopathology. Our data uncover recruitment of lung macrophages, regulation of ciliated epithelial cells, and modulation of inflammatory cytokines and interferon-stimulated genes as likely contributors. Moreover, we found these roles to be distinct and non-redundant, as they are not observed with knockout of, or treatment with, type I IFN. These data elucidate unique antiviral functions of IFN-λ and suggest IFN-λ augmentation as a promising therapeutic for treating HMPV disease and promoting effective vaccine responses.

Clearance of persistent SARS-CoV-2 associates with increased neutralizing antibodies in advanced HIV disease post-ART initiation

SARS-CoV-2 clearance requires adaptive immunity but the contribution of neutralizing antibodies and T cells in different immune states is unclear. Here we ask which adaptive immune responses associate with clearance of long-term SARS-CoV-2 infection in HIV-mediated immunosuppression after suppressive antiretroviral therapy (ART) initiation. We assembled a cohort of SARS-CoV-2 infected people in South Africa (n = 994) including participants with advanced HIV disease characterized by immunosuppression due to T cell depletion. Fifty-four percent of participants with advanced HIV disease had prolonged SARS-CoV-2 infection (>1 month). In the five vaccinated participants with advanced HIV disease tested, SARS-CoV-2 clearance associates with emergence of neutralizing antibodies but not SARS-CoV-2 specific CD8 T cells, while CD4 T cell responses were not determined due to low cell numbers. Further, complete HIV suppression is not required for clearance, although it is necessary for an effective vaccine response. Persistent SARS-CoV-2 infection led to SARS-CoV-2 evolution, including virus with extensive neutralization escape in a Delta variant infected participant. The results provide evidence that neutralizing antibodies are required for SARS-CoV-2 clearance in HIV-mediated immunosuppression recovery, and that suppressive ART is necessary to curtail evolution of co-infecting pathogens to reduce individual health consequences as well as public health risk linked with generation of escape mutants.

Humoral and cellular immunity in three different types of COVID-19 vaccines against SARS-CoV-2 variants in a real-world data analysis.

An effective vaccine response is currently a critical issue in the control of COVID-19. Little is known about humoral and cellular immunity comparing protein-based vaccine with other types of vaccines. The relevance of basal immunity to antibody production is also unknown. Seventy-eight individuals were enrolled in the study. The primary outcome were the level of spike-specific antibodies and neutralizing antibodies measured by ELISA. Secondary measures included memory T cells and basal immunity estimated by flow cytometry and ELISA. Correlations for all parameters were calculated using the nonparametric Spearman correlation method. We observed that two doses of mRNA-based Moderna mRNA-1273 (Moderna) vaccine produced the highest total spike-binding antibody and neutralizing ability against the wild-type (WT), Delta, and Omicron variants. The protein-based MVC-COV1901 (MVC) vaccine developed in Taiwan produced higher spike-binding antibodies against Delta and Omicron variants and neutralizing ability against the WT strain than the adenovirus-based AstraZeneca-Oxford AZD1222 (AZ) vaccine. Moderna and AZ vaccination produced more central memory T cells in PBMC than the MVC vaccine. However, the MVC vaccine had the lowest adverse effects compared to the Moderna and AZ vaccines. Surprisingly, the basal immunity represented by TNF-α, IFN-γ, and IL-2 prior to vaccination was negatively correlated with the production of spike-binding antibodies and neutralizing ability. This study compared memory T cells, total spike-binding antibody levels, and neutralizing capacity against WT, Delta, and Omicron variants between the MVC vaccine and the widely used Moderna and AZ vaccines, which provides valuable information for future vaccine development strategies.

Effect of DMARDs on the immunogenicity of vaccines.

Vaccines are important for protecting individuals at increased risk of severe infections, including patients undergoing DMARD therapy. However, DMARD therapy can also compromise the immune system, leading to impaired responses to vaccination. This Review focuses on the impact of DMARDs on influenza and SARS-CoV-2 vaccinations, as such vaccines have been investigated most thoroughly. Various data suggest that B cell depletion therapy, mycophenolate mofetil, cyclophosphamide, azathioprine and abatacept substantially reduce the immunogenicity of these vaccines. However, the effects of glucocorticoids, methotrexate, TNF inhibitors and JAK inhibitors on vaccine responses remain unclear and could depend on the dosage and type of vaccination. Vaccination is aimed at initiating robust humoral and cellular vaccine responses, which requires efficient interactions between antigen-presenting cells, T cells and B cells. DMARDs impair these cells in different ways and to different degrees, such as the prevention of antigen-presenting cell maturation, alteration of T cell differentiation and selective inhibition of B cell subsets, thus inhibiting processes that are necessary for an effective vaccine response. Innovative modified vaccination strategies are needed to improve vaccination responses in patients undergoing DMARD therapy and to protect these patients from the severe outcomes of infectious diseases.

VIGET: A web portal for study of vaccine-induced host responses based on Reactome pathways and ImmPort data.

Host responses to vaccines are complex but important to investigate. To facilitate the study, we have developed a tool called Vaccine Induced Gene Expression Analysis Tool (VIGET), with the aim to provide an interactive online tool for users to efficiently and robustly analyze the host immune response gene expression data collected in the ImmPort/GEO databases. VIGET allows users to select vaccines, choose ImmPort studies, set up analysis models by choosing confounding variables and two groups of samples having different vaccination times, and then perform differential expression analysis to select genes for pathway enrichment analysis and functional interaction network construction using the Reactome's web services. VIGET provides features for users to compare results from two analyses, facilitating comparative response analysis across different demographic groups. VIGET uses the Vaccine Ontology (VO) to classify various types of vaccines such as live or inactivated flu vaccines, yellow fever vaccines, etc. To showcase the utilities of VIGET, we conducted a longitudinal analysis of immune responses to yellow fever vaccines and found an intriguing complex activity response pattern of pathways in the immune system annotated in Reactome, demonstrating that VIGET is a valuable web portal that supports effective vaccine response studies using Reactome pathways and ImmPort data.

Longitudinal mapping of hepatitis B vaccine-induced B-cell linear epitopes in healthy individuals.

The elimination of hepatitis B virus (HBV) infection is partially facilitated by the prophylactic HB vaccine. As the loss of seroprotection over time remains a conundrum for long-lasting protection, a comprehensive dynamic analysis of immunogenic targets of the HB vaccine will provide novel insights into the improvement and design of potential targets. In this study, 36 healthy subjects without prior history of hepatitis B infection and negative for hepatitis B surface antibody (anti-HBs) were enrolled. Participants were given a series of three doses of HB vaccine on a 0-, 1-, and 6-month schedule and longitudinally followed up. We systematically mapped 55 overlapping 15-mer peptides covering the small S protein of hepatitis B virus (SHBs) of vaccinees' serum samples at seven time points by performing an ELISA assay. Additionally, the frequencies and function dynamics of adaptive immune response were assessed by flow cytometry. We found that the SHBs peptide coverage presented an overall upward trend along with the vaccination progress, and the individual subpartition recognition was strongly correlated with the anti-HBs titers. Moreover, we identified one dominant epitope (S29) located on "a determinant region" associated with effective vaccine response. Besides, significant correlations between the proportion of plasmablasts and proliferating B cells and levels of anti-HBs were ascertained. Taken together, our data characterized the dynamics of HB vaccine-induced neutralizing antibodies against B-cell linear epitopes on SHBs and adaptive immune response, which will be constructive to develop the next-generation vaccine.

Infecção por circovírus suíno associado a micotoxicose: relato de caso

Circovirus is widespread in pig farming, and mainly affects piglets increasing morbidity and mortality rates, being vaccination the most effective strategy to control one. However, for an effective vaccine response, certain factors must be considered, such as the adoption of good practices during the conservation and handling of vaccines, environmental challenges, nutritional and health status of the animals, and presence of immunosuppressive agents, such as mycotoxins, in the feed. Here, we describe a circovirus outbreak associated with mycotoxin immunosuppression that occurred in the piglets during the nursery phase at a commercial farm, which initiated with a sudden increase in the mortality of vaccinated piglets. Blood samples were collected and analyzed using RT-PCR, while the feed was subjected to mycotoxicological analysis. RT-PCR analysis revealed the presence of porcine circovirus type 2 (PCV-2) in the blood serum samples, thereby confirming the circovirus outbreak. The feed analysis revealed elevated levels of mycotoxins (deoxynivalenol, aflatoxins, and fumonisins), which were above the levels tolerated by the piglets during the nursery phase. Therefore, the contaminated feed was discarded, and a new ration was made available. Concurrently, the vaccination program was amended to normalize the mortality rate. The presence of mycotoxins in the feed could be the predisposed factor for piglet infection caused by PCV-2 and other diseases. This is an important aspect because the immunosuppressive effect of mycotoxins can alter the vaccine response, thereby making the piglets more susceptible to the diseases even after being vaccinated, although they should be immunologically protected.

Preimmunization correlates of protection shared across malaria vaccine trials in adults

Identifying preimmunization biological characteristics that promote an effective vaccine response offers opportunities for illuminating the critical immunological mechanisms that confer vaccine-induced protection, for developing adjuvant strategies, and for tailoring vaccination regimens to individuals or groups. In the context of malaria vaccine research, studying preimmunization correlates of protection can help address the need for a widely effective malaria vaccine, which remains elusive. In this study, common preimmunization correlates of protection were identified using transcriptomic data from four independent, heterogeneous malaria vaccine trials in adults. Systems-based analyses showed that a moderately elevated inflammatory state prior to immunization was associated with protection against malaria challenge. Functional profiling of protection-associated genes revealed the importance of several inflammatory pathways, including TLR signaling. These findings, which echo previous studies that associated enhanced preimmunization inflammation with protection, illuminate common baseline characteristics that set the stage for an effective vaccine response across diverse malaria vaccine strategies in adults.

Disc Large Homolog 1 Is Critical for Early T Cell Receptor Micro Cluster Formation and Activation in Human T Cells.

T cell activation by antigen involves multiple sequential steps, including T cell receptor-microcluster TCR-(MC) formation, immunological synapse formation, and phosphorylation of mediators downstream of the TCR. The adaptor protein, Disc Large Homolog 1 (DLG1), is known to regulate proximal TCR signaling and, in turn, T cell activation, acting as a molecular chaperone that organizes specific kinases downstream of antigen recognition. In this study, we used knockdown and knockout technologies in human primary T cells and a human T cell line to demonstrate the role of DLG1 in proximal T cell signaling. High-end confocal microscopy was used for pictorial representation of T cell micro-clusters and colocalization studies. From all these studies, we could demonstrate that DLG1 functions even earlier than immunological synapse formation, to regulate T cell activation by promoting TCR-MC formation. Moreover, we found that DLG1 can act as a bridge between the TCR-ζ chain and ZAP70 while inhibiting binding of the phosphatase SHP1 to TCR-ζ. Together, these effects drive dysregulation of T cell activation in DLG1-deficient T cells. Overall, the activation and survival status of T cell is a critical determinant of effective vaccine response, and DLG1-mediated T cell signaling events can be a driving factor for improving vaccine-designing strategies.

Multi-Omic Data Integration Allows Baseline Immune Signatures to Predict Hepatitis B Vaccine Response in a Small Cohort.

BackgroundVaccination remains one of the most effective means of reducing the burden of infectious diseases globally. Improving our understanding of the molecular basis for effective vaccine response is of paramount importance if we are to ensure the success of future vaccine development efforts.MethodsWe applied cutting edge multi-omics approaches to extensively characterize temporal molecular responses following vaccination with hepatitis B virus (HBV) vaccine. Data were integrated across cellular, epigenomic, transcriptomic, proteomic, and fecal microbiome profiles, and correlated to final HBV antibody titres.ResultsUsing both an unsupervised molecular-interaction network integration method (NetworkAnalyst) and a data-driven integration approach (DIABLO), we uncovered baseline molecular patterns and pathways associated with more effective vaccine responses to HBV. Biological associations were unravelled, with signalling pathways such as JAK-STAT and interleukin signalling, Toll-like receptor cascades, interferon signalling, and Th17 cell differentiation emerging as important pre-vaccination modulators of response.ConclusionThis study provides further evidence that baseline cellular and molecular characteristics of an individual’s immune system influence vaccine responses, and highlights the utility of integrating information across many parallel molecular datasets.

Activation of miR-21-Regulated Pathways in Immune Aging Selects against Signatures Characteristic of Memory T Cells

SUMMARYInduction of protective vaccine responses, governed by the successful generation of antigen-specific anti-bodies and long-lived memory T cells, is increasingly impaired with age. Regulation of the T cell proteome by a dynamic network of microRNAs is crucial to T cell responses. Here, we show that activation-induced upregulation of miR-21 biases the transcrip-tome of differentiating T cells away from memory T cells and toward inflammatory effector T cells. Such a transcriptome bias is also characteristic of T cell responses in older individuals who have increased miR-21 expression and is reversed by antagonizing miR-21. miR-21 targets negative feedback circuits in several signaling pathways. The concerted, sustained activity of these signaling path-ways in miR-21high T cells disfavors the induction of transcription factor networks involved in memory cell differentiation. Our data suggest that curbing miR-21 upregulation or activity in older individuals may improve their ability to mount effective vaccine responses.

D-112 Structure of a natively-glycosylated HIV-1 Env reveals a new mode for VH1-2 antibody recognition of the CD4 binding site relevant to vaccine

Background: Structural studies of broadly neutralizing antibodies (bNAbs) bound to Env trimers have revealed mechanisms by which bNAbs targeting various epitopes penetrate the glycan shield to either accommodate or include N-glycans in their epitopes. Although accessibility to the conserved host receptor (CD4) binding site (CD4bs) is restricted by surrounding glycans, VRC01-class bNAbs mimic CD4 binding to share a common mode of gp120 binding and glycan accommodation using a VH1-2*02- derived variable heavy (VH) domain. While attractive candidates for immunogen design, features of VRC01-class bNAbs such as a high degree of somatic hypermutation (SHM) and a short (5-residue) light chain (LC) complementarity determining region 3 (CDRL3) (found in only 1% of human LCs) suggest they might be difficult to elicit through vaccination. However, we recently isolated a VH1-2*02-derived CD4bs bNAb, named IOMA, that includes a normal-length (8 residues) CDRL3. Methods: We used X-ray crystallography to solve the first structure of a fully- and natively-glycosylated Env trimer in complex with IOMA, and the V3-loop-directed bNAb 10-1074. Results: Our structure revealed antibody-vulnerable glycan holes and roles of complex-type N-glycans on Env that are relevant to vaccine design, while also demonstrating that IOMA is a new class of CD4-mimetic bNAb that contains features of both VH1-2/VRC01-class and VH1-46/8ANC131-class bNAbs. Conclusions: Analysis of the native glycan shield on HIV-1 Env allows the first full description of the interplay between heterogeneous untrimmed high-mannose and complex-type N-glycans within the CD4bs, V3-loop, and other epitopes on Env. In addition, the structural characterization of IOMA revealed an alternative pathway from VRC01-class bNAbs relevant to vaccine design, which could more readily lead to an effective vaccine response due to higher frequencies of normal-length CDRL3s compared with the rare 5-residue CDRL3s required for VRC01-class bNAbs, and a lower need for SHMs.

Specifically modified Env immunogens activate B-cell precursors of broadly neutralizing HIV-1 antibodies in transgenic mice.

VRC01-class broadly neutralizing HIV-1 antibodies protect animals from experimental infection and could contribute to an effective vaccine response. Their predicted germline forms (gl) bind Env inefficiently, which may explain why they are not elicited by HIV-1 Env-immunization. Here we show that an optimized Env immunogen can engage multiple glVRC01-class antibodies. Furthermore, this immunogen activates naive B cells expressing the human germline heavy chain of 3BNC60, paired with endogenous mouse light chains in vivo. To address whether it activates B cells expressing the fully humanized gl3BNC60 B-cell receptor (BCR), we immunized mice carrying both the heavy and light chains of gl3BNC60. B cells expressing this BCR display an autoreactive phenotype and fail to respond efficiently to soluble forms of the optimized immunogen, unless it is highly multimerized. Thus, specifically designed Env immunogens can activate naive B cells expressing human BCRs corresponding to precursors of broadly neutralizing HIV-1 antibodies even when the B cells display an autoreactive phenotype.

Evaluation of factors associated with response to hepatitis B vaccination in patients with inflammatory bowel disease.

It is recommended to investigate the serology of hepatitis B virus (HBV) and vaccinate seronegative patients at the time of diagnosis in inflammatory bowel diseases (IBD). This study aimed to investigate the efficacy of HBV vaccine and factors affecting the response.In this retrospective, observational study, HBV-seronegative IBD patients were administered 3 doses (at months 0, 1, and 6) recombinant 20 μg HbsAg. Patients’ demographics, IBD attributes, and treatment methods were investigated as the factors with potential impacts on vaccination outcomes.One hundred twenty-five patients with IBD were evaluated. The number of patients with Anti-HBs >10 IU/L was 71 (56.8%), and the number of patients with anti-HBs >100 IU/L was 50 (40%). Age, disease activity, Crohn disease subtype, and immunosuppressive treatment (IST) were found to have significant effects on immune response (P = 0.011, P < 0.001, P = 0.003, and P < 0.001, respectively). With multivariate analysis, age < 45 years (OR 3.1, 95% CI 1.2–8.3, P = 0.020), vaccination during remission (OR 5.6, 95% CI 2.3–14, P < 0.001), and non-IST (OR 11.1, 95% CI 2.9–43.2, P = 0.001) had favorable effects on the occurrence of adequate vaccine response.The likelihood of achieving adequate immune response with standard HBV vaccination protocol in IBD is low. Selecting vaccination protocols with more potent immunogenicity is a better approach to achieve effective vaccine response in patients with multiple unfavorable factors.

A polyvalent influenza A DNA vaccine induces heterologous immunity and protects pigs against pandemic A(H1N1)pdm09 virus infection

The composition of current influenza protein vaccines has to be reconsidered every season to match the circulating influenza viruses, continuously changing antigenicity. Thus, influenza vaccines inducing a broad cross-reactive immune response would be a great advantage for protection against both seasonal and emerging influenza viruses. We have developed an alternative influenza vaccine based on DNA expressing selected influenza proteins of pandemic and seasonal origin. In the current study, we investigated the protection of a polyvalent influenza DNA vaccine approach in pigs. We immunised pigs intradermally with a combination of influenza DNA vaccine components based on the pandemic 1918 H1N1 (M and NP genes), pandemic 2009 H1N1pdm09 (HA and NA genes) and seasonal 2005 H3N2 genes (HA and NA genes) and investigated the protection against infection with virus both homologous and heterologous to the DNA vaccine components.We found that pigs challenged with a virus homologous to the HA and NA DNA vaccine components were well protected from infection. In addition, heterologous challenge virus was cleared rapidly compared to the unvaccinated control pigs. Immunisation by electroporation induced HI antibodies >40 HAU/ml seven days after second vaccination. Heterologous virus challenge as long as ten weeks after last immunisation was able to trigger a vaccine antibody HI response 26 times higher than in the control pigs. The H3N2 DNA vaccine HA and NA genes also triggered an effective vaccine response with protective antibody titres towards heterologous H3N2 virus.The described influenza DNA vaccine is able to induce broadly protective immune responses even in a larger animal, like the pig, against both heterologous and homologous virus challenges despite relatively low HI titres after vaccination. The ability of this DNA vaccine to limit virus shedding may have an impact on virus spread among pigs which could possibly extend to humans as well, thereby diminishing the risk for epidemics and pandemics to evolve.

Cancer vaccines and carbohydrate epitopes.

Tumor-associated carbohydrate antigens (TACA) result from the aberrant glycosylation that is seen with transformation to a tumor cell. The carbohydrate antigens that have been found to be tumor-associated include the mucin related Tn, Sialyl Tn, and Thomsen-Friedenreich antigens, the blood group Lewis related Lewis(Y), Sialyl Lewis(X) and Sialyl Lewis(A), and Lewis(X) (also known as stage-specific embryonic antigen-1, SSEA-1), the glycosphingolipids Globo H and stage-specific embryonic antigen-3 (SSEA-3), the sialic acid containing glycosphingolipids, the gangliosides GD2, GD3, GM2, fucosyl GM1, and Neu5GcGM3, and polysialic acid. Recent developments have furthered our understanding of the T-independent type II response that is seen in response to carbohydrate antigens. The selection of a vaccine target antigen is based on not only the presence of the antigen in a variety of tumor tissues but also on the role this antigen plays in tumor growth and metastasis. These roles for TACAs are being elucidated. Newly acquired knowledge in understanding the T-independent immune response and in understanding the key roles that carbohydrates play in metastasis are being applied in attempts to develop an effective vaccine response to TACAs. The role of each of the above mentioned carbohydrate antigens in cancer growth and metastasis and vaccine attempts using these antigens will be described.

CD8 T-Cell Proliferative Capacity Is Compromised in Primary HIV-1 Infection

Understanding the correlates of immunity that control HIV-1 infection is imperative to our understanding of HIV-1 disease and vaccine development. HIV-1-specific cytotoxic T lymphocytes are fundamental to the control of viremia; however, which T-cell repertoire components enact this control remains unclear. We hypothesize that polyfunctional HIV-1-specific CD8 T cells capable of viral control are present in most patients early in infection and these cells are distinguished by their ability to secrete interleukin (IL)-2 and proliferate. We examined HIV-1-specific CD8 T-cell proliferation and cytokine secretion in primary HIV-1 infection (PHI) using known HIV-1 cytotoxic T-cell epitopes to exclude CD4 bystander effect. We found that only a subset of patients with PHI demonstrated "CD4-independent" CD8 proliferation ex vivo. The remainder of the patients lacked HIV-1-specific CD8 T cells with proliferative capacity, even after the addition of exogenous IL-2. Among the proliferators, IL-2 production from the total HIV-specific CD8 T-cell population correlated with proliferation. Surprisingly, though, we did not routinely detect both IL-2 secretion and proliferative capacity from the same antigen-specific CD8 T cells. Thus, there are distinct and heterogeneous populations of CD8 T cells, phenotypically characterized by either proliferation or IL-2 secretion and few with dual capacity. Generation of these responses may be an important measure of HIV-1 control but are not universal after PHI. Furthermore, the heterogeneity of this population suggests that a simple measure of an effective vaccine response remains elusive.

Immunosenescence and Vaccination in Nursing Home Residents

The elderly population continues to increase in most countries. Concomitantly, the number of individuals who are institutionalized is also increasing, unfortunately, with more and more individuals being institutionalized at greater ages. These elderly individuals are very different from healthy, community-dwelling elderly individuals, in that many are considered to be frail and have various chronic diseases. It is apparent that the immune response diminishes even in healthy elderly people and that the pathologies that occur in nursing home patients, together with malnutrition, further impair immunity required for an effective vaccine response. Therefore, it is important to take secondary age-related effects, attributable to factors such as chronic diseases, inflammation, frailty, nutrition, functional status, and stress, into account when assessing vaccination strategies. Despite these alterations that can affect immune function and their potential interaction with vaccination, vaccination is still worthwhile and is recommended for elderly nursing home residents. Research efforts should continue attempts to elucidate the immunological basis of impaired immunity in nursing home residents to design improved prevention strategies for this vulnerable group.

Influence of maternal antibodies on vaccine responses: inhibition of antibody but not T cell responses allows successful early prime-boost strategies in mice

The transfer of maternal antibodies to the offspring and their inhibitory effects on active infant immunization is an important factor hampering the use of certain vaccines, such as measles or respiratory syncytial virus vaccine, in early infancy. The resulting delay in protection by conventional or novel vaccines may have significant public health consequences. To define immunization approaches which may circumvent this phenomenon, experiments were set up to further elucidate its immunological bases. The influence of maternal antibodies on antibody and T cell responses to measles hemagglutinin (MV-HA) were analyzed following MV-HA immunization of pups born to immune or control BALB/c mothers using four different antigen delivery systems: live or inactivated conventional measles vaccine, a live recombinant canarypox vector and a DNA vaccine. High levels (> 5 log10) of maternal anti-HA antibodies totally inhibited antibody responses to each of the vaccine constructs, whereas normal antibody responses were elicited in presence of lower titers of maternal antibodies. However, even high titers of maternal antibodies affected neither the induction of vaccine-specific Th1/Th2 responses, as assessed by proliferation and levels of IFN-γ and IL-5 production, nor CTL responses in infant mice. On the basis of these unaltered T cell responses, very early priming and boosting (at 1 and 3 weeks of age, respectively) with live measles vaccine allowed to circumvent maternal antibody inhibition of antibody responses in pups of immune mothers. This was confirmed in another immunization model (tetanus toxoid). It suggests that effective vaccine responses may be obtained earlier in presence of maternal antibodies through the use of appropriate immunization strategies using conventional or novel vaccines for early priming.

Influence of maternal antibodies on vaccine responses: inhibition of antibody but not T cell responses allows successful early prime-boost strategies in mice.

The transfer of maternal antibodies to the offspring and their inhibitory effects on active infant immunization is an important factor hampering the use of certain vaccines, such as measles or respiratory syncytial virus vaccine, in early infancy. The resulting delay in protection by conventional or novel vaccines may have significant public health consequences. To define immunization approaches which may circumvent this phenomenon, experiments were set up to further elucidate its immunological bases. The influence of maternal antibodies on antibody and T cell responses to measles hemagglutinin (MV-HA) were analyzed following MV-HA immunization of pups born to immune or control BALB/c mothers using four different antigen delivery systems: live or inactivated conventional measles vaccine, a live recombinant canarypox vector and a DNA vaccine. High levels (> 5 log10) of maternal anti-HA antibodies totally inhibited antibody responses to each of the vaccine constructs, whereas normal antibody responses were elicited in presence of lower titers of maternal antibodies. However, even high titers of maternal antibodies affected neither the induction of vaccine-specific Th1/Th2 responses, as assessed by proliferation and levels of IFN-gamma and IL-5 production, nor CTL responses in infant mice. On the basis of these unaltered T cell responses, very early priming and boosting (at 1 and 3 weeks of age, respectively) with live measles vaccine allowed to circumvent maternal antibody inhibition of antibody responses in pups of immune mothers. This was confirmed in another immunization model (tetanus toxoid). It suggests that effective vaccine responses may be obtained earlier in presence of maternal antibodies through the use of appropriate immunization strategies using conventional or novel vaccines for early priming.