Persistent Antibody Response Research Articles

The Antibody Response to SARS-CoV-2 Infection.

BackgroundTesting for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)–specific antibodies has become an important tool, complementing nucleic acid tests (NATs) for diagnosis and for determining the prevalence of coronavirus disease 2019 (COVID-19) in population serosurveys. The magnitude and persistence of antibody responses are critical for assessing the duration of immunity.MethodsA SARS-CoV-2-specific immunofluorescent antibody (IFA) assay for immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin M (IgM) was developed and prospectively evaluated by comparison to the reference standard of NAT on respiratory tract samples from individuals with suspected COVID-19. Neutralizing antibody responses were measured in a subset of samples using a standard microneutralization assay.ResultsA total of 2753 individuals were eligible for the study (126 NAT-positive; prevalence, 4.6%). The median “window period” from illness onset to appearance of antibodies (range) was 10.2 (5.8–14.4) days. The sensitivity and specificity of either SARS-CoV-2 IgG, IgA, or IgM when collected ≥14 days after symptom onset were 91.3% (95% CI, 84.9%–95.6%) and 98.9% (95% CI, 98.4%–99.3%), respectively. The negative predictive value was 99.6% (95% CI, 99.3%–99.8%). The positive predictive value of detecting any antibody class was 79.9% (95% CI, 73.3%–85.1%); this increased to 96.8% (95% CI, 90.7%–99.0%) for the combination of IgG and IgA.ConclusionsMeasurement of SARS-CoV-2-specific antibody by IFA is an accurate method to diagnose COVID-19. Serological testing should be incorporated into diagnostic algorithms for SARS-CoV-2 infection to identify additional cases where NAT was not performed and resolve cases where false-negative and false-positive NATs are suspected. The majority of individuals develop robust antibody responses following infection, but the duration of these responses and implications for immunity remain to be established.

TGF-β2 interfering oligonucleotides used as adjuvants for microbial vaccines.

The success of using immune checkpoint inhibitors to treat cancers implies that inhibiting an immunosuppressive cytokine, such as TGF-β2, could be a strategy to develop novel adjuvants for microbial vaccines. To develop nucleic acid based TGF-β2 inhibitors, we designed three antisense oligonucleotides, designated as TIO1, TIO2, and TIO3, targeting the conserve regions identical in human and mouse TGF-β2 mRNA 3'-untranslated region. In cultured immune cells, TIO3 and TIO1 significantly reduced the TGF-β2 mRNA expression and protein production. In mice, the TIO3 and TIO1, when formulated in various microbial vaccines, significantly enhanced the antibody response to the vaccines, and the TIO3-adjuvanted influenza virus vaccine induced effective protection against the influenza virus challenge. In the immunized mice, TIO3 formulated in microbial vaccines dramatically reduced surface-bound TGF-β2 expression on CD4+ T cells and CD19+ B cells in the lymph node (LN) cells and spleen cells; up-regulated the expression of CD40, CD80, CD86, and MHC II molecules on CD19+ B cells and CD11c+ dendritic cells; and promoted IFN-γ production in CD4+ T cells and CD8+ T cells in the LN cells. Overall, TIO3 or TIO1 could be used as a novel type of adjuvant for facilitating the microbial vaccines to elicit more vigorous and persistent antibody response by interfering with TGF-β2 expression.

The role of serological testing in the SARS-CoV-2 outbreak

Antibody tests for the novel coronavirus, SARS-CoV2, have been developed both as rapid diagnostic assays and for high-throughput formalserology platforms. Although these tests may be a useful adjunct to a diagnostic strategy, they have a number of limitations. Because of theantibody and viral dynamics of the coronavirus, their sensitivity can be variable, especially at early time points after symptom onset. Additionaldata are required on the performance of the tests in the South African population, especially with regard to development and persistence ofantibody responses and whether antibodies are protective against reinfection. These tests may, however, be useful in guiding the public healthresponse, providing data for research (including seroprevalence surveys and vaccine initiatives) and development of therapeutic strategies.

In vitro Notch-mediated adjuvant immunogenic potency is induced by combining QS-21 and MPL in a co-culture model of PBMC and HUVEC cells

Few vaccine adjuvants have been approved for human use although several are currently being studied in preclinical and clinical trial. MPL is a toll-like receptor agonist able to trigger a high and persistent antibody response via-TLR-4 while QS-21 activates the NLRP3 inflammasome. Data suggest that there is a cross-talk between Notch and TLR signaling pathways modulating the polarization of the immune response in a MyD88-dependent manner. However, the role of Notch on the mechanism action of immunogenic adjuvants has not been addressed yet. This study aims to evaluate the in vitro toxicity and inflammatory response triggered by MPL and QS-21 using an in vitro human cell co-culture model and to determine whether NFκB or Notch signaling pathways are involved in their mechanism of immunotoxicity. In order to do this, we evaluated the effect of QS- 21/MPL alone or in combination using a co-culture of PBMC and HUVEC using cytotoxicity, surface expression of ECAMs, cell adhesion and cytokine release, NF-κB activation and NOTCH1 expression as observation endpoints. We found that both MPL and QS-21 were cytotoxic at concentrations over 5 μg/mL. Both adjuvants were able to trigger the expression of ECAMs and induce firm adhesion of PBMC to the endothelium. QS-21 and MPL combination demonstrated a synergistic effect on cellular recruitment and cytokine release generating a switch from Th2 to Th1 cytokine profile. Both MPL and QS-21 by themselves were able to generate significant NF-κB activation. However, this effect was not observed when both adjuvants were combined. On the contrary, the adjuvants alone and combined induced an overexpression of NOTCH-1. This is an important finding, as it provides new evidence that these adjuvants could modulate reactogenicity of vaccines through Notch signaling.

Dynamics of IgM and IgG responses to the next generation of engineered Duffy binding protein II immunogen: Strain-specific and strain-transcending immune responses over a nine-year period.

A low proportion of P. vivax-exposed individuals acquire protective strain-transcending neutralizing IgG antibodies that are able to block the interaction between the Duffy binding protein II (DBPII) and its erythrocyte-specific invasion receptor. In a recent study, a novel surface-engineered DBPII-based vaccine termed DEKnull-2, whose antibody response target conserved DBPII epitopes, was able to induce broadly binding-inhibitory IgG antibodies (BIAbs) that inhibit P. vivax reticulocyte invasion. Toward the development of DEKnull-2 as an effective P. vivax blood-stage vaccine, we investigate the relationship between naturally acquired DBPII-specific IgM response and the profile of IgG antibodies/BIAbs activity over time. A nine-year follow-up study was carried-out among long-term P. vivax-exposed Amazonian individuals and included six cross-sectional surveys at periods of high and low malaria transmission. DBPII immune responses associated with either strain-specific (Sal1, natural DBPII variant circulating in the study area) or conserved epitopes (DEKnull-2) were monitored by conventional serology (ELISA-detected IgM and IgG antibodies), with IgG BIAbs activity evaluated by functional assays (in vitro inhibition of DBPII-erythrocyte binding). The results showed a tendency of IgM antibodies toward Sal1-specific response; the profile of Sal1 over DEKnull-2 was not associated with acute malaria and sustained throughout the observation period. The low malaria incidence in two consecutive years allowed us to demonstrate that variant-specific IgG (but not IgM) antibodies waned over time, which resulted in IgG skewed to the DEKnull-2 response. A persistent DBPII-specific IgM response was not associated with the presence (or absence) of broadly neutralizing IgG antibody response. The current study demonstrates that long-term exposure to low and unstable levels of P. vivax transmission led to a sustained DBPII-specific IgM response against variant-specific epitopes, while sustained IgG responses are skewed to conserved epitopes. Further studies should investigate on the role of a stable and persistent IgM antibody response in the immune response mediated by DBPII.

A novel TLR7 agonist as adjuvant to stimulate high quality HBsAg-specific immune responses in an HBV mouse model

BackgroundThe global burden of hepatitis B virus (HBV) infection in terms of morbidity and mortality is immense. Novel treatments that can induce a protective immune response are urgently needed to effectively control the HBV epidemic and eventually eradicate chronic HBV infection.MethodsWe designed and evaluated an HBV therapeutic vaccine consisting of a novel Toll-like receptor 7 (TLR7) agonist T7-EA, an Alum adjuvant and a recombinant HBsAg protein. We used RNA-seq, ELISA and hTLR7/8 reporting assays to characterize T7-EA in vitro and real-time PCR to evaluate the tissue-retention characteristics in vivo. To evaluate the adjuvant potential, we administrated T7-EA intraperitoneally in a formulation with an Alum adjuvant and HBsAg in normal and HBV mice, then, we evaluated the HBsAg-specific immune responses by ELISA and Elispot assays.ResultsT7-EA acted as an hTLR7-specific agonist and induced a similar gene expression pattern as an unmodified TLR7 ligand when Raw 264.7 cells were exposed to T7-EA; however, T7-EA was more potent than the unmodified TLR7 ligand. In vivo studies showed that T7-EA had tissue-retaining activity with stimulating local cytokine and chemokine expression for up to 7 days. T7-EA could induce Th1-type immune responses, as evidenced by an increased HBsAg-specific IgG2a titer and a T-cell response in normal mice compared to mice received traditional Alum-adjuvant HBV vaccine. Importantly, T7-EA could break immune tolerance and induce persistent HBsAg-specific antibody and T-cell responses in an HBV mouse model.ConclusionsT7-EA might be a candidate adjuvant in a prophylactic and therapeutic HBV vaccine.

HPV-Specific Systemic Antibody Responses and Memory B Cells are Independently Maintained up to 6 Years and in a Vaccine-Specific Manner Following Immunization with Cervarix and Gardasil in Adolescent and Young Adult Women in Vaccination Programs in Italy.

Human papillomavirus (HPV) persistent infections are associated with cervical cancer and other HPV-related diseases and tumors. Thus, the characterization of long lasting immunity to currently available HPV vaccines is important. A total of 149 female subjects vaccinated with Cervarix or Gardasil participated to the study and they were stratified according to age (10–12-year-old and 16–20-year-old). Humoral immune responses (IgG and neutralizing antibody titers, antibody avidity) and circulating memory B cells were analyzed after an average of 4–6 years from the third immunization. The humoral responses against HPV-16 and HPV-18 (and HPV-6 and HPV-11 for Gardasil) were high in both age groups and vaccines up to six years from the third dose. However, Cervarix induced significantly higher and more persistent antibody responses, while the two vaccines were rather equivalent in inducing memory B cells against HPV-16 and HPV-18. Moreover, the percentage of subjects with vaccine-specific memory B cells was even superior among Gardasil vaccinees and, conversely, Cervarix vaccinated individuals with circulating antibodies, but undetectable memory B cells were found. Finally, a higher proportion of Cervarix-vaccinated subjects displayed cross-neutralizing responses against non-vaccine types HPV-31 and HPV-45. Gardasil and Cervarix may, thus, differently affect long-lasting humoral immunity from both the quantitative and qualitative point of view.

Next-generation serology: integrating cross-sectional and capture-recapture approaches to infer disease dynamics.

Two approaches have been classically used in disease ecology to estimate epidemiological parameters from field studies: cross-sectional sampling from unmarked individuals and longitudinal capture-recapture setups, which generally involve more limited numbers of marked individuals due to cost and logistical constraints. Although the benefits of longitudinal setups are increasingly acknowledged in the disease ecology community, cross-sectional data remain largely overrepresented in the literature, probably because of the inherent costs of longitudinal surveys. In this context, we used simulated data to compare the performances of cross-sectional and longitudinal designs to estimate the force of infection (i.e., the rate at which susceptible individuals become infected). Then, inspired from recent method developments in quantitative ecology, we explore the benefits of integrating both cross-sectional (seroprevalences) and longitudinal (individuals histories) data sets. In doing so, we investigate the effects of host species life history, antibody persistence, and degree of a priori knowledge and uncertainty on demographic and epidemiological parameters, as those are expected to affect in different ways the level of inference possible from the data. Our results highlight how those elements are important to consider in determining optimal sampling designs. In the case of long-lived species exposed to infectious agents resulting in persistent antibody responses, integrated designs are especially valuable as they benefit from the performances of longitudinal designs even with relatively small longitudinal sample sizes. As an illustration, we apply this approach to a combination of empirical and simulated data inspired from a case of bats exposed to a rabies virus. Overall, this work highlights that serology field studies could greatly benefit from the opportunity of integrating cross-sectional and longitudinal designs.

Persisting Antibody Response 9 Years After Bivalent Human Papillomavirus (HPV) Vaccination in a Cohort of Dutch Women: Immune Response and the Relation to Genital HPV Infections.

The bivalent human papillomavirus (HPV) vaccine is highly effective and induces robust serological responses. Using a Dutch prospective cohort initiated in 2009, including 744 vaccinated and 294 unvaccinated girls (1993-1994) who provide a vaginal self-swab sample, serum sample, and questionnaire yearly, we report a high, persisting antibody response up to 9 years after vaccination for vaccine types HPV-16 or HPV-18. Antibodies against nonvaccine HPV types 31, 33, 45, 52, and 58 were lower but still significantly higher than in unvaccinated individuals. This was also reflected in the seroprevalence. We compared participant characteristics and antibody levels between vaccinated women with and those without HPV infections 1 year before infection (204 incident and 64 persistent infections), but we observed no consistent difference in type-specific antibody levels. Having a high-risk HPV infection was associated with sexual risk behavior and smoking 1 year before infection. Although high antibody levels are necessary for protection, our study suggests that on the individual level other factors such as HPV exposure or antibody avidity could be important.

2770. Intrapulmonary Vaccination with an M Protein-Deficient Respiratory Syncytial Virus (RSV) Vaccine Protects Infant Baboons Against an RSV Challenge

BackgroundRSV infection is a major cause of lung disease in infants, yet there is no licensed vaccine. We are developing a live RSV vaccine with a deletion of the M protein (“Mnull RSV”). The RSV M protein is responsible for assembling newly synthesized RSV proteins into intact virus. Mnull RSV infects cells, replicates all proteins except M, and incites antibody and T-cell responses but, in the absence of the M protein, cannot replicate and infect other cells. We wished to show that vaccination with Mnull RSV directly into the lung in early infancy induces persistent neutralizing antibody (NA) responses that protect infant baboons against an RSV challenge.MethodsTwo-week-old infants were vaccinated with a single dose of Mnull RSV (8 × 107 vaccine units) or a sham preparation instilled into an endotracheal tube. Infants were observed continuously for signs of rapid breathing using infrared cameras. Four to six months later, serum RSV NA titers were determined, and infants were challenged intratracheally with the human RSV A2 strain. Respiratory rates were calculated daily. On days 0, 5, 7, and 12 after infection, arterial blood was drawn for blood gas analysis, lung function was assessed using a pneumotachometer, and bronchoalveolar lavage was performed for virus titrations.ResultsAt 4–6 months following vaccination, RSV NA was present at a mean titer of 192 in sera of Mull RSV recipients, but was undetectable in sera of sham vaccinated animals. Animals were then challenged with RSV, and sham vaccinated animals developed increased respiratory rates, increased alveolar-arterial (A-a) oxygen gradients, and BAL viral titers on day 5 were 3,500 pfu/mL. In contrast, Mnull RSV vaccinated animals had lower respiratory ratios throughout the length of the study (P = 0.038), lesser A-a gradients (improved oxygenation) vs. controls, and no virus was recovered from BAL fluids (P < 0.0001).ConclusionIntrapulmonary vaccination of infantswith Mnull RSV at 2 weeks of age results in strong RSV NA responses that persist beyond the length of an average RSV season. Mnull RSV recipients were protected against tachypnea, reduced oxygenation and viral replication for at least 4–6 months following vaccination. We will next study intrapulmonary vaccination administering Mnull RSV via a nebulizer.Disclosures All authors: No reported disclosures.

Persistence of antibody response in chikungunya.

Chikungunya is a mosquito-borne viral illness associated with chronic arthritic symptoms that persist for months. The IgM antibody appears within a week post any infection and declines at 2-3months. The present study was aimed to demonstrate the presence of specific IgM antibody among chikungunya confirmed cases. Blood samples were collected from chikungunya PCR positive patients at the time of diagnosis, at 1-week, 1, 8, 10 and 12months post infection. All acute and follow-up serum samples were evaluated for chikungunya virus-specific IgM antibodies using ELISA technique. Our findings indicate the persistence of anti-chikungunya IgM up to 10-months post-infection in a majority of chikungunya virus infected persons. Interpretation of results should be carefully done as only IgM ELISA is used to diagnose acute infection, especially post chikungunya outbreak. The presence of IgM antibody does not rule out the absence of any other diagnosis due to its persistence. Thus, we hypothesize that real-time PCR is more reliable for the detection of acute chikungunya cases in endemic areas while IgM detection may be useful in identifying exposure to this disease.

Vaccine induction of antibodies and tissue-resident CD8+ T cells enhances protection against mucosal SHIV-infection in young macaques.

Antibodies and cytotoxic T cells represent 2 arms of host defense against pathogens. We hypothesized that vaccines that induce both high-magnitude CD8+ T cell responses and antibody responses might confer enhanced protection against HIV. To test this hypothesis, we immunized 3 groups of nonhuman primates: (a) Group 1, which includes sequential immunization regimen involving heterologous viral vectors (HVVs) comprising vesicular stomatitis virus, vaccinia virus, and adenovirus serotype 5-expressing SIVmac239 Gag; (b) Group 2, which includes immunization with a clade C HIV-1 envelope (Env) gp140 protein adjuvanted with nanoparticles containing a TLR7/8 agonist (3M-052); and (c) Group 3, which includes a combination of both regimens. Immunization with HVVs induced very high-magnitude Gag-specific CD8+ T cell responses in blood and tissue-resident CD8+ memory T cells in vaginal mucosa. Immunization with 3M-052 adjuvanted Env protein induced robust and persistent antibody responses and long-lasting innate responses. Despite similar antibody titers in Groups 2 and 3, there was enhanced protection in the younger animals in Group 3, against intravaginal infection with a heterologous SHIV strain. This protection correlated with the magnitude of the serum and vaginal Env-specific antibody titers on the day of challenge. Thus, vaccination strategies that induce both CD8+ T cell and antibody responses can confer enhanced protection against infection.

FimH as a mucosal adjuvant enhances persistent antibody response and protective efficacy of the anti-caries vaccine

ObjectiveTo investigate whether the recombinant FimH-S.T protein could modulate immune response to anti-caries vaccine in vitro and in vivo. DesignRecombinant FimH protein derived from Salmonella was constructed and purified. The expression of dendritic cell maturation markers and cytokines release were performed by flow cytometry, Real-time PCR and ELISA. In addition, BALB/c mice were administered with anti-caries PAc vaccine plus FimH-S.T, antibody responses were evaluated by ELISA. Splenocytes of immunized mice were detected for their proliferative ability in response to in vitro retreatment with PAc antigen by flow cytometry. Caries protection against dental caries formation was also investigated. ResultsThe purified FimH-S.T induced phenotypic maturation of DC2.4 by up-regulating the expression of costimulatory molecules and MHC II, provoked the production and secretion of cytokines via TLR4-dependent signaling pathway in vitro. Furthermore, the mice immunized with the mixture of FimH-S.T and PAc significantly enhanced the PAc-specific antibodies in the serum along with saliva and promoted splenocyte proliferation. Our results also confirmed that PAc+FimH-S.T decreased the caries lesions formation which provided high protective efficacy against dental caries. ConclusionOur study demonstrates that recombinant FimH-S.T could enhance specific IgA responses and protection of anti-caries vaccine, possessing mucosal adjuvant ability by activating DC2.4 via TLR4 signaling pathway.

Kinetics of serum antibodies in response to infection with Yersinia enterocolitica.

Information on the kinetics of the serum antibody response to infection with Yersinia enterocolitica is essential to allow the estimation and comparison of seroconversion rates in a diversity of pools of cross-sectional serum antibody measurements. Data from 94 patients with acute enteritis caused by Yersinia infection were used. The follow-up period for the longitudinal study was 36 months, addressed by questionnaire. An indirect enzyme-linked immunosorbent assay method was adapted to determine the concentration of antibodies against Y. enterocolitica in human sera. A mathematical within-host model was used to describe the interaction between pathogen and immune system and the waning of immunity after clearing of the pathogen. All observed antibodies (IgG, IgM, IgA) reached peak levels shortly after infection and then decayed slowly indicating that the median levels decreased only little during the observation period. Estimated maximum peak antibody levels were highest in IgG. Seroresponse curves of all antibodies showed large individual variation between patients. There was no apparent pattern of variation with age, nor any notable difference between genders. Estimated half-times were very long for all antibodies, and their posterior distributions were highly skewed. IgA appeared to have the most persistent antibody response, compared with IgG and IgM. Median peak levels of all three antibodies were similar. There was no significance found between peak antibody levels and severity of symptoms of gastrointestinal infection and severity of joint pain. Our findings allow the use of cross-sectional serum antibody measurements as biomarkers, to estimate seroconversion rates. Such seroincidence estimates include asymptomatic seroconversions, thereby avoiding under-reporting, and allows the comparison of infection pressures among countries, independent of their healthcare and surveillance systems.

A Novel Human Papillomavirus 16 L1 Pentamer-Loaded Hybrid Particles Vaccine System: Influence of Size on Immune Responses.

Cervical cancer remains the second-most prevalent female malignancy around the world, leading to a great majority of cancer-related mortality that occurs mainly in developing countries. Developing an effective and low-cost vaccine against human papillomavirus (HPV) infection, especially in medically underfunded areas, is urgent. Compared with vaccines based on HPV L1 viruslike particles (VLPs) in the market, recombinant HPV L1 pentamer expressed in Escherichia coli represents a promising and potentially cost-effective vaccine for preventing HPV infection. Hybrid particles comprising a polymer core and lipid shell have shown great potential compared to conventional aluminum salts adjuvant and is urgently needed for HPV L1 pentamer vaccines. It is well-reported that particle sizes are crucial in regulating immune responses. Nevertheless, reports on the relationship between the particulate size and the resultant immune response have been in conflict, and there is no answer to how the size of particles regulates specific immune response for HPV L1 pentamer-based candidate vaccines. Here, we fabricated HPV 16 L1 pentamer-loaded poly(d,l-lactide- co-glycolide) (PLGA)/lecithin hybrid particles with uniform sizes (0.3, 1, and 3 μm) and investigated the particle size effects on antigen release, activation of lymphocytes, dendritic cells (DCs) activation and maturation, follicular helper CD4+ T (TFH) cells differentiation, and release of pro-inflammatory cytokines and chemokines. Compared with the other particle sizes, 1 μm particles induced more powerful antibody protection and yielded more persistent antibody responses, as well as more heightened anamnestic responses upon repeat vaccination. The superior immune responses might be attributed to sustainable antigen release and robust antigen uptake and transport and then further promoted a series of cascade reactions, including enhanced DCs maturation, increased lymphocytes activation, and augmented TFH cells differentiation in draining lymph nodes (DLNs). Here, a powerful and economical platform for HPV vaccine and a comprehensive understanding of particle size effect on immune responses for HPV L1 pentamer-based candidate vaccines are provided.

Intrastructural Help: Harnessing T Helper Cells Induced by Licensed Vaccines for Improvement of HIV Env Antibody Responses to Virus-Like Particle Vaccines.

ABSTRACTInduction of persistent antibody responses by vaccination is generally thought to depend on efficient help by T follicular helper cells. Since the T helper cell response to HIV Env may not be optimal, we explored the possibility of improving the HIV Env antibody response to virus-like particle (VLP) vaccines by recruiting T helper cells induced by commonly used licensed vaccines to provide help for Env-specific B cells. B cells specific for the surface protein of a VLP can internalize the entire VLP and thus present peptides derived from the surface and core proteins on their major histocompatibility complex class II (MHC-II) molecules. This allows T helper cells specific for the core protein to provide intrastructural help for B cells recognizing the surface protein. Consistently, priming mice with an adjuvanted Gag protein vaccine enhanced the HIV Env antibody response to subsequent booster immunizations with HIV VLPs. To harness T helper cells induced by the licensed Tetanolpur vaccines, HIV VLPs that contained T helper cell epitopes of tetanus toxoid were generated. Tetanol-immunized mice raised stronger antibody responses to immunizations with VLPs containing tetanus toxoid T helper cell epitopes but not to VLPs lacking these epitopes. Depending on the priming immunization, the IgG subtype response to HIV Env after the VLP immunization could also be modified. Thus, harnessing T helper cells induced by other vaccines appears to be a promising approach to improve the HIV Env antibody response to VLP vaccines.IMPORTANCE Induction of HIV Env antibodies at sufficient levels with optimal Fc effector functions for durable protection remains a challenge. Efficient T cell help may be essential to induce such a desirable antibody response. Here, we provide proof of concept that T helper cells induced by a licensed vaccine can be harnessed to provide help for HIV Env-specific B cells and to modulate the Env-specific IgG subtype response.

AS03- and MF59-Adjuvanted Influenza Vaccines in Children.

Influenza is a major cause of respiratory disease leading to hospitalization in young children. However, seasonal trivalent influenza vaccines (TIVs) have been shown to be ineffective and poorly immunogenic in this population. The development of live-attenuated influenza vaccines and adjuvanted vaccines are important advances in the prevention of influenza in young children. The oil-in-water emulsions MF59 and adjuvant systems 03 (AS03) have been used as adjuvants in both seasonal adjuvanted trivalent influenza vaccines (ATIVs) and pandemic monovalent influenza vaccines. Compared with non-adjuvanted vaccine responses, these vaccines induce a more robust and persistent antibody response for both homologous and heterologous influenza strains in infants and young children. Evidence of a significant improvement in vaccine efficacy with these adjuvanted vaccines resulted in the use of the monovalent (A/H1N1) AS03-adjuvanted vaccine in children in the 2009 influenza pandemic and the licensure of the seasonal MF59 ATIV for children aged 6 months to 2 years in Canada. The mechanism of action of MF59 and AS03 remains unclear. Adjuvants such as MF59 induce proinflammatory cytokines and chemokines, including CXCL10, but independently of type-1 interferon. This proinflammatory response is associated with improved recruitment, activation and maturation of antigen presenting cells at the injection site. In young children MF59 ATIV produced more homogenous and robust transcriptional responses, more similar to adult-like patterns, than did TIV. Early gene signatures characteristic of the innate immune response, which correlated with antibody titers were also identified. Differences were detected when comparing child and adult responses including opposite trends in gene set enrichment at day 3 postvaccination and, unlike adult data, a lack of correlation between magnitude of plasmablast response at day 7 and antibody titers at day 28 in children. These insights show the utility of novel approaches in understanding new adjuvants and their importance for developing improved influenza vaccines for children.

Long-term humoral immunity induced by CVC1302-adjuvanted serotype O foot-and-mouth disease inactivated vaccine correlates with promoted T follicular helper cells and thus germinal center responses in mice.

Long-lasting humoral immunity is one of the necessary criteria for a successful vaccine. In our previous study, it was demonstrated that the immunopotentiator CVC1302 could improve the humoral immunity induced by the foot and mouth disease virus (FMDV) killed vaccine (KV) with only one dose. Significantly higher FMDV-specific antibody titers and more persistent antibody responses were observed in pigs receiving CVC1302-adjuvanted KV (KV-CVC1302) than in those inoculated with KV alone. In this study, we show that CVC1302 enhances murine IgG responses to FMDV by promoting a potent T follicular helper cell (TFH) response, which directly controls the magnitude of the germinal center (GC) B cell response. These results indicate a need for studies to assess the capacity of CVC1302 to enhance the efficacy of FMDV KV immunization in pigs, and provide new insights into the development of FMDV vaccines.

An engineered vaccine of the Plasmodium vivax Duffy binding protein enhances induction of broadly neutralizing antibodies

Plasmodium vivax invasion into human reticulocytes is a complex process. The Duffy binding protein (DBP) dimerization with its cognate receptor is vital for junction formation in the invasion process. Due to its functional importance, DBP is considered a prime vaccine candidate, but variation in B-cell epitopes at the dimer interface of DBP leads to induction of strain-limited immunity. We believe that the polymorphic residues tend to divert immune responses away from functionally conserved epitopes important for receptor binding or DBP dimerization. As a proof of concept, we engineered the vaccine DEKnull to ablate the dominant Bc epitope to partially overcome strain-specific immune antibody responses. Additional surface engineering on the next generation immunogen, DEKnull-2, provides an immunogenicity breakthrough to conserved protective epitopes. DEKnull-2 elicits a stronger broadly neutralizing response and reactivity with long-term persistent antibody responses of acquired natural immunity. By using novel engineered DBP immunogens, we validate that the prime targets of protective immunity are conformational epitopes at the dimer interface. These successful results indicate a potential approach that can be used generally to improve efficacy of other malaria vaccine candidates.

Antibody persistence and evidence of immune memory at 5years following administration of the 9-valent HPV vaccine.

The 9-valent HPV (9vHPV) vaccine was developed to prevent infection and disease related to 9 HPV types (HPV6/11/16/18/31/33/45/52/58) which cause approximately 90% of cervical cancers, HPV-related vulvar, vaginal and anal cancers, and genital warts worldwide. In a pivotal efficacy study, the 9vHPV vaccine prevented infection and disease due to the 9 vaccine types. Duration of protection remains to be determined. Vaccines that induce long-term protection are generally characterized by the generation of immune memory. The purpose of this report is to assess the persistence of HPV antibody response and existence of immune memory at 5years post-vaccination. A subset of subjects (N=150) who received 3 doses of 9vHPV vaccine at day 1, month 2 and month 6 in the pivotal efficacy study continued in a study extension and received a fourth dose of 9vHPV vaccine at month 60. Serum HPV antibody levels were measured pre-dose 4 and at 7 and 28days post-dose 4 by competitive Luminex immunoassay. Adverse events were assessed using a vaccination report card. HPV antibodies induced following the 3-dose series of 9vHPV vaccine in the base study persisted through month 60 with seropositivity rates ranging from 77.5% to 100%. Geometric mean titers at 1week and 1month post-dose 4 were 1.25-4.10 and 1.65-4.88-fold higher, respectively, than levels observed 1month following the completion of the three-dose primary series. Seropositivity rates were >99% and 100% at 1week and 1month post-dose 4, respectively. The fourth dose of 9vHPV vaccine was generally well tolerated. A three-dose regimen of the 9vHPV vaccine induced persistent HPV antibody response through 5years post-vaccination. Administration of a fourth dose resulted in a strong anamnestic response to all 9 vaccine types. These findings suggest that the efficacy of the 9vHPV vaccine will be long lasting. Clinical Trials.gov Identifier:NCT00543543.