Pseudovirion-based Neutralization Assay Research Articles

Proteomics Platform Reveals Broad-Spectrum Nanobodies for SARS-CoV-2 Variant Neutralization.

The ongoing evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to the emergence of different variants of concerns with immune evasion that have been prevalent over the past three years. Nanobodies, the functional variable regions of camelid heavy-chain-only antibodies, have garnered interest in developing neutralizing antibodies due to their smaller size, structural stability, ease of production, high affinity, and low immunogenicity, among other characteristics. In this work, we describe an integrated proteomics platform for the high-throughput screening of nanobodies against different SARS-CoV-2 spike variants. To demonstrate this platform, we immunized a camel with subunit 1 (S1) of the wild-type spike protein and constructed a nanobody phage library. The binding and neutralizing activities of the nanobodies against 72 spike variants were then measured, resulting in the identification of two nanobodies (C-282 and C-39) with broad neutralizing activity against six non-Omicron variants (D614G, Alpha, Beta, Gamma, Delta, Kappa) and five Omicron variants (BA.1-5). Their neutralizing capability was validated using in vitro pseudovirus-based neutralization assays. All these results demonstrate the utility of our proteomics platform to identify new nanobodies with broad neutralizing capability and to develop a treatment for patients with SARS-CoV-2 variant infection in the future.

HPV-specific antibodies in female genital tract secretions captured via first-void urine retain their neutralizing capacity

ABSTRACT Human papillomavirus (HPV) vaccines, primarily relying on neutralizing antibodies, have proven highly effective. Recently, HPV-specific antibodies have been detected in the female genital tract secretions captured by first-void urine (FVU), offering a minimally invasive diagnostic approach. In this study, we investigated whether HPV16-specific antibodies present in FVU samples retain their neutralizing capacity by using pseudovirion-based neutralization assays. Paired FVU and serum samples (vaccinated n = 25, unvaccinated n = 25, aged 18–25) were analyzed using two orthogonal pseudovirion-based neutralization assays, one using fluorescence microscopy and the other using luminescence-based spectrophotometry. Results were compared with HPV16-specific IgG concentrations and correlations between neutralizing antibodies in FVU and serum were explored. The study demonstrated the presence of neutralizing antibodies in FVU using both pseudovirion-based neutralization assays, with the luminescence-based assay showing higher sensitivity for FVU samples, while the fluorescence microscopy-based assay exhibited better specificity for serum and overall higher reproducibility. High Spearman correlation values were calculated between HPV16-IgG and HPV16-neutralizing antibodies for both protocols (rs: 0.54–0.94, p < .001). Significant Spearman correlations between FVU and serum concentrations were also established for all assays (rs: 0.44–0.91, p < .01). This study demonstrates the continued neutralizing ability of antibodies captured with FVU, supporting the hypothesis that HPV vaccination may reduce autoinoculation and transmission risk to the sexual partner. Although further protocol optimizations are warranted, these findings provide a foundation for future research and larger cohort studies that could have implications for the optimal design, evaluation, and implementation of HPV vaccination programs.

Inter-epitope spacer variation within polytopic L2-based human papillomavirus antigens affects immunogenicity

The human papillomavirus minor capsid protein L2 is being extensively explored in pre-clinical studies as an attractive vaccine antigen capable of inducing broad-spectrum prophylactic antibody responses. Recently, we have developed two HPV vaccine antigens – PANHPVAX and CUT-PANHPVAX- both based on heptameric nanoparticle antigens displaying polytopes of the L2 major cross-neutralizing epitopes of eight mucosal and twelve cutaneous HPV types, respectively. Prompted by the variable neutralizing antibody responses against some of the HPV types targeted by the antigens observed in previous studies, here we investigated the influence on immunogenicity of six distinct glycine-proline spacers inserted upstream to a specific L2 epitope. We show that spacer variants differentially influence antigen immunogenicity in a mouse model, with the antigen constructs M8merV6 and C12merV6 displaying a superior ability in the induction of neutralizing antibodies as determined by pseudovirus-based neutralization assays (PBNAs). L2-peptide enzyme-linked immunosorbent assay (ELISA) assessments determined the total anti-L2 antibody level for each antigen variant, showing for the majority of sera a correlation with their repective neutralizing antibody level. Surface Plasmon Resonance revealed that L2 epitope-specific, neutralizing monoclonal antibodies (mAbs) display distinct avidities to different antigen spacer variants. Furthermore, mAb affinity toward individual spacer variants was well correlated with their neutralizing antibody induction capacity, indicating that the mAb affinity assay predicts L2-based antigen immunogenicity. These observations provide insights on the development and optimization of L2-based HPV vaccines.

Immune escape of BA.2.86 is comparable to XBB subvariants from the plasma of BA.5- and BA.5-XBB-convalescent subpopulations.

The EG.5.1 variant of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has been prevalent since mid-July 2023 in the United States and China. The variant BA.2.86 has become a major concern because it is 34 mutations away from the parental variant BA.2 and >30 mutations from XBB.1.5. There is an urgent need to evaluate whether the immunity of the population and current vaccines are protective against EG.5.1 and BA.2.86. Based on a cohort of two breakthrough-infected groups, the levels of neutralizing antibodies (NAbs) against different subvariants were measured using pseudovirus-based neutralization assays. XBB.1.5, EG.5.1, and BA.2.86 are comparably immune-evasive from neutralization by the plasma of individuals recovered from BA.5 infection (BA.5-convalescent) or XBB.1.9.2/XBB.1.5 infection following BA.5 infection (BA.5-XBB-convalescent). NAb levels against EG.5.1 and BA.2.86 subvariants remained >120 geometric mean titers (GMTs) in BA.5-XBB-convalescent individuals 2 months postinfection but were <40 GMTs in BA.5-convalescent individuals. Furthermore, the XBB-targeting messenger RNA (mRNA) vaccine RQ3033 induced higher levels of NAbs against XBB.1.5, EG.5.1, and BA.2.86 than against BA.5-XBB infection. The results suggest that BA.2.86 and EG.5.1 are unlikely to cause more severe concerns than the currently circulating XBB subvariants and that the XBB.1.5-targeting mRNA vaccine tested has promising protection against EG.5.1 and BA.2.86.

Development of a proficiency testing program for HPV serology assays used to evaluate antibody responses in vaccine trials

In this study, a proficiency panel was created for evaluation of assay performance and inter- and intra-laboratory assay comparisons, especially the ability to accurately measure negative, low, intermediate, and high levels of HPV type-specific antibodies. Comprised of 80 deidentified samples, this panel is designed for individual labs to evaluate assay performance characteristics on a biennial basis, to promote standardization of methodology and harmonization of data from human papillomavirus (HPV) serology tests in vaccine trials. The proficiency panel was qualified using 2 types of assays (singleplex Enzyme-Linked Immunosorbent Assays [ELISAs] or Multiplex antibody-binding assays and Pseudovirion-based neutralization assays [PBNAs]) in 10 laboratories from 7 countries, monitoring HPV antibody responses for up to 9 HPV types and using 3 different analysis methods. Sensitivity, specificity, and correlations (concordance, accuracy, and precision) were evaluated for each HPV type. In laboratories that tested all 80 samples, results from most (74/80) samples were reported with 100% accuracy across all 9 HPV types. The average sensitivity and specificity for singleplex and multiplex antibody binding assays ranged from 86.7% to 98.3% (sensitivity) and 84.2% to 94.3% (specificity), while the average sensitivity and specificity for the Pseudovirion (PsV)-based neutralization assays (PBNA) ranged from 87.6% to 99.4% (sensitivity) and 52.4% to 94.4% (specificity). This proficiency panel will help with assessing performance characteristics of HPV serology assays used in clinical trial studies and assure the data generated from these assays is harmonized.

Advances on two serological assays for human papillomavirus provide insights on the reactivity of antibodies against a cross-neutralization epitope of the minor capsid protein L2.

A second generation of prophylactic human papillomavirus (HPV) vaccines based on the minor capsid protein L2 has entered clinical trials as promising alternative to meet the gaps left out by the current vaccines concerning type-restricted protection, high costs and low penetrance in immunization programs of lowand middle-income countries. Most of the serological assays available to assess anti-HPV humoral responses are, however, not well suited for measuring vaccine-induced anti-L2 antibody responses. In this work, we have advanced our automated, purely add-on High-Throughput Pseudovirion-Based Neutralization Assay (HT-PBNA) in an L2-oriented approach for measuring antibody-mediated neutralization of HPV types 6/16/18/31/33/52/58. With the optimized settings, we observed 24- to 120-fold higher sensitivity for detection of neutralizing Ab to the L2 protein of HPV6, HPV16, HPV18, and HPV31, compared to the standard HT-PBNA. Alternatively, we have also developed a highly sensitive, cell-free, colorimetric L2-peptide capture ELISA for which the results were strongly concordant with those of the advanced neutralization assay, named HT-fc-PBNA. These two high-throughput scalable assays represent attractive approaches to determine antibody-based correlates of protection for the HPV L2 vaccines that are to come.

Phenotypic analysis of HIV-1 resistance to CD4 binding site broadly-neutralizing antibodies

Abstract Broadly neutralizing antibodies (bNAbs) show strong immunotherapy potential by targeting conserved regions of the HIV-1 envelope. Single bNAb use in viremic individuals quickly results in the emergence of escape variants, likely originating from existing quasispecies. An ex vivo assay was developed to predict bNAb efficacy in viremic individuals. The development of a predictive bNAb efficacy model may assist with the planning of future clinical trials. The ex vivoassay used pre-infusion CD4 +T cells from participants enrolled in the VRC 607/ACTG A5378 phase I study of the CD4 binding site (CD4bs) bNAbs’ VRC01LS (n=7) or VRC07-523LS (n=9). From these assays, the escape variant signatures of outgrowth viruses that replicated in presence of CD4bs bNAbs, were identified. We found that these escape variants contained key changes to the ß23-V5 region of the gp120 envelope, including charge changes, glycan loss, and/or glycan shifts. Outgrowth viruses from each participant had similar escape mutation patterns. Resistance mutations of the viral env sequences were confirmed in pseudovirus-based neutralization assays. We found complementary escape profiles from 3 CD4bs bNAbs (1–18LS, N6LS, and VRC01v23) with ex vivoand neutralization assays showing suppression by 1 or 2 but not all 3 bNAbs, supporting the potential for combination bNAb therapy. Our data suggest that the simultaneous use of multiple CD4 binding site bNAbs together could aid in limiting viral escape. Supported by intramural funds from NIH.

Precision and correlation of ED50 and endpoint titer method in measuring HPV vaccine immunogenicity

Cervical cancer, the second leading cause of cancer-related deaths among women, is caused by human papillomavirus (HPV), a sexually transmitted virus. Vaccination is an effective preventive measure against viral infections and subsequent development of cervical cancer. Enzyme-linked immunosorbent assay (ELISA) is commonly used to measure specific binding antibody titers and assess the immunogenicity of test vaccines in preclinical models or clinical volunteers. Two methods of deriving titers, the endpoint titer (ET) and the effective dilution producing a median maximal effective fold of dilution (ED50) with a cut-off value, are widely used. For HPV, a pseudovirion-based neutralization assay (PBNA) is used to measure functional antibody titers. The ELISA binding titers and functional PBNA titers were found to be well-correlated for all nine HPV types tested in the vaccine, consistent with previous studies on HPV 16/18. Comparing the PBNA results with the two titration methods, the ED50 method showed higher precision and a closer correlation with PBNA results, both for individual types and pooled data analysis for all nine types. When comparing the titration results of the ET method based on a cut-off value with the ED50 method using all the data points across the dilution series, the ED50 method demonstrated better precision and a stronger correlation with PBNA results.

Application of Pseudotyped Viruses.

Highly pathogenic emerging and reemerging viruses have serious public health and socioeconomic implications. Although conventional live virus research methods can more reliably investigate disease pathogenicity and evaluate antiviral products, they usually depend on high-level biosafety laboratories and skilled researchers; these requirements hinder in vitro assessments of efficacy, as well as efforts to test vaccines and antibody drugs. In contrast, pseudotyped viruses (i.e., single-round infectious viruses that mimic the membrane structures of various live viruses) are widely used in studies of highly pathogenic viruses because they can be handled in biosafety level 2 facilities. This chapter provides a concise overview of various aspects of pseudotyped virus technologies, including (1) exploration of the mechanisms of viral infection; (2) evaluation of the efficacies of vaccines and monoclonal antibodies based on pseudovirion-based neutralization assay; (3) assessment of antiviral agents (i.e., antibody-based drugs and inhibitors); (4) establishment of animal models of pseudotyped virus infection in vivo; (5) investigation of the evolution, infectivity, and antigenicity of viral variants and viral glycosylation; and (6) prediction of antibody-dependent cell-mediated cytotoxic activity.

Immunogenicity correlation in cynomolgus monkeys between Luminex-based total IgG immunoassay and pseudovirion-based neutralization assay for a 14-valent recombinant human papillomavirus vaccine.

A new virus‐like particle based vaccine covering 14 types of high‐risk and disease‐inducing human papillomavirus (HPV) can offer better coverage against HPV‐induced diseases, particularly cervical cancers. However, the assessment of immunogenicity of the vaccine is an important task, representing not only its significant clinical characteristics, but also a major challenge, in terms of both the suitability of methods and the clinical sample testing throughput supporting clinical development. This work covers the development and evaluation of a method based on Luminex technology (a coded‐bead and flow‐cytometric approach) to assess the HPV‐type specific total immunoglobulin G (IgG). This method can evaluate the antibodies in sera post immunization against multiple types of HPV simultaneously (i.e., with multiplexing capability), save time and cost, and improve test throughput with higher sensitivity and precision than the classical, plate‐based enzyme‐linked immunoassay and competitive Luminex‐based immunoassays. Using cynomolgus monkeys as model, we demonstrated the good correlation between the results from the pseudovirion‐based neutralization assay (PBNA), and the Luminex‐based total IgG assay, supporting that the latter method can be considered as a viable, dependable replacement method for the PBNA supporting immunogenicity evaluation of HPV vaccine in preclinical development and clinical investigation.

Immunogenicity of a Two-Dose Human Papillomavirus Vaccine Schedule in HIV-Infected Adolescents with Immune Reconstitution.

HIV-infected patients are at increased risk of human papillomavirus (HPV) acquisition and HPV-associated diseases. This study set out to determine whether a two-dose (2D) HPV vaccination schedule was sufficient in HIV-infected adolescents with immune reconstitution (IR) following antiretroviral treatment. Participants aged 9–15 years who had CD4 cell counts > 500 cells/mm3 and HIV-1 RNA < 40 copies/mL for at least one year were assigned to the 2D schedule, while older participants or those without IR received a three-dose (3D) schedule. Antibodies to HPV-16 and -18 were measured using a pseudovirion-based neutralization assay. A total of 96 subjects were enrolled; 31.3% and 68.7% received the 2D and 3D schedule, respectively. Of these, 66.7% and 57.6% of the 2D and 3D participants, respectively, were male. The seroconversion rates for HPV-16 and HPV-18 were 100% in all cases, except for HPV-18 in males who received the 3D schedule (97.4%). In males, the anti-HPV-16 geometric mean titers (GMTs) were 6859.3 (95% confidence interval, 4394.3–10,707.1) and 7011.1 (4648.8–10,573.9) in the 2D and 3D groups (p = 0.946), respectively, and the anti-HPV-18 GMTs were 2039.3 (1432.2–2903.8) and 2859.8 (1810.0–4518.4) in the 2D and 3D (p = 0.313) groups, respectively. In females, the anti-HPV-16 GMTs were 15,758.7 (8868.0–28,003.4) and 26,241.6 (16,972.7–40,572.3) in the 2D and 3D groups (p = 0.197), respectively, and the anti-HPV-18 GMTs were 5971.4 (3026.8–11,780.6) and 9993.1 (5950.8–16,781.1) in the 2D and 3D groups (p = 0.271), respectively. In summary, a 2D schedule is as immunogenic in young adolescents with IR as a 3D schedule in older subjects and those without IR.

Multiplex immunoassay to measure antibody response to nine HPV vaccine types

Well-characterized HPV serology assays are required to evaluate performance of biosimilar candidate vaccines, reduced dosing schedules and novel administration methods. We report characterization of an expanded assay, M9ELISA, that detects antibodies to HPV virus-like particles (VLP) of nine types using direct IgG ELISA on the Meso Scale Discovery (MSD) electrochemiluminescence platform. The method is based on the previously published M4ELISA which detects antibodies to HPV6,11,16, and 18. It has been modified to add detection of antibodies to HPV31,33,45,52 and 58, and to streamline assay and reduce background.The M9ELISA plates were prepared with purified type specific L1 + L2 VLPs coated on 10-spot/well standard MSD microplates. Results of ELISA on three serial dilutions of serum were read on MSD imager, and titers calculated using the parallel line method. Evaluations included dynamic range, assay reproducibility, and stability over time. We compared M9ELISA results to those from a pseudovirion-based neutralization assay in sera from a mixed cohort of unvaccinated and vaccinated individuals (n = ~116) and to competitive Luminex immunoassay (cLIA) results in sera from a predominantly unvaccinated cohort (n = 4426).The linear range of the assay extended over 5 logs, with inter-assay reproducibility coefficient of variation ≤25% for all types. The pre-coated plates were stable for at least 2 years. Spearman correlation of antibody titers showed excellent correlation with PBNA (r = 0.86–0.97) and moderate correlation (r = 0.52–0.68) with cLIA. Thus, the M9ELISA can serve as a useful platform for high-throughput, sensitive and simultaneous quantitation of the antibody responses to nine HPV vaccine types.

Naturally acquired HPV antibodies against subsequent homotypic infection: A large-scale prospective cohort study

SummaryBackgroundAlthough recent studies have suggested that naturally acquired Human papillomavirus (HPV) antibodies are partly protective against subsequent homotypic infection, the extent of protection remains indecisive. Here, we evaluate the protective effect of neutralizing and IgG antibodies simultaneously.MethodsIn a cohort of 3634 women aged 18-45 years from the control arm of a phase III trial of the HPV-16/18 bivalent vaccine, participants were tested for neutralizing antibodies by pseudovirion-based neutralization assay (PBNA) and IgG antibodies by enzyme-linked immunosorbent assay (ELISA) at baseline. HPV-16/18 incident and persistent infections were identified using cervical specimens periodically collected during the 5·5 years of follow-up. The protective effects of HPV-16/18 neutralizing and IgG antibodies against homotypic infection were assessed using a Cox proportional hazard model.FindingsFor the persistent infection (PI) endpoints of HPV-16/18 lasting for over 6/12 months, a prevalence of type-specific neutralizing antibodies was highly protective (6-month PI: hazard ratio (HR) = 0·16, 95% confidence interval (CI): 0·04, 0·65; 12-month PI: HR = 0·23, 95% CI: 0·06, 0·94), whereas a prevalence of IgG antibodies was associated with minor and non-significant protection (6-month PI: HR = 0·66, 95% CI: 0·40, 1·09; 12-month PI: HR = 0·66, 95% CI: 0·36, 1·20). After increasing the cut-off value to the median IgG level, the risk of 6-month PI was significantly lower in seropositive vs seronegative women (HR = 0·38, 95% CI: 0·18, 0·83).InterpretationNaturally acquired antibodies are associated with a substantially reduced risk of subsequent homotypic infection.FundingNSFC; The Fujian Province Health Education Joint Research Project; Xiamen Science and Technology Major Project; CIFMS; and Xiamen Innovax.

AIDS Malignancy Consortium 054: Safety and Immunogenicity of the Quadrivalent Vaccine in Indian Women Living With HIV.

Human papillomavirus (HPV)-associated cervical cancer is a leading cause of death among Indian women. Indian women living with HIV (WLWH) may be at especially high risk. The quadrivalent HPV (qHPV) vaccine is effective in prevention of initial infection with HPV-6/11/16/18 in HIV-negative women. Little is known about previous exposure to HPV-6/11/16/18, safety, and immunogenicity of qHPV in Indian WLWH. One hundred fifty WLWH with different CD4 levels and HIV viral load (VL) were vaccinated at 0/2/6 months at CART-CRS-IDMC, Chennai, India. Serology was performed at weeks 0, 28, and 52 for HPV-6/11/16/18 using a competitive Luminex immunoassay and for HPV-16/18 using a pseudovirion-based neutralization assay. Mean age was 30.8 years (range, 19-44 years). 71/87/73/81% of women were naive (sero-negative and DNA-negative) to HPV-6/11/16/18 at baseline, respectively. Among per-protocol women naive to HPV-6/11/16/18 at baseline, 100/99/99/90%, respectively, seroconverted at week 28 and 95/96/98/71% were sero-positive at week 52, respectively. Pseudovirion-based neutralization assay identified more seroconversion to HPV-18 than competitive Luminex immunoassay. There were no significant differences in the proportion seroconverting by baseline or nadir CD4 or HIV VL; however, there was a trend for increased proportion seroconverting to HPV-18 among women with higher baseline CD4 level (P = 0.052). There were no qHPV-related serious adverse events and no change in CD4 level or HIV VL among women on ART. qHPV vaccine was safe and immunogenic in Indian WLWH. A high proportion were naive to HPV-6/11/16/18 and may benefit from vaccination although many were married and several years post-initiation of sexual activity.

Naturally Acquired Antibodies Against Human Papillomavirus are Protective Against Subsequent Homotypic Infection: A Large-Scale Prospective Cohort Study

Background: Currently, knowledge of the protective effects of natural acquired immunity against human papillomavirus (HPV) is mostly based on studies using binding antibodies (IgG) as biomarkers due to the labor-consuming characteristics of neutralizing antibodies assays, and the conclusions from different studies are inconsistent. Methods: In a phase III clinical trial of the Escherichia coli-produced HPV-16/18 bivalent vaccine, participants were tested for neutralizing antibodies and IgG antibodies with pseudovirion-based neutralization assay and L1 virus-like particle-based ELISA, respectively. HPV-16 and HPV-18 infections were identified using cervical specimens periodically collected during the over 5·5 years of follow-up. Data of the 3,634 women aged 18-45 years in the control arm were used to evaluate the protective effects of the type-specific neutralizing antibodies as well as the IgG antibodies. Findings: For the persistent infection (PI) endpoints of HPV-16/18 lasting for over 6/12 months, the prevalence of type-specific neutralizing antibodies was highly protective (6 m PI: RR = 0·16, 95% CI: 0·04, 0·63; 12 m PI: RR = 0·23, 95% CI: 0·06, 0·95), while the prevalence of IgG antibodies was associated with minor and nonsignificant protection (6 m PI: RR = 0·71, 95% CI: 0·44, 1·16; 12 m PI: RR = 0·76, 95% CI: 0·43, 1·36). Women with neutralizing antibodies had a lower risk of subsequent homotypic infection, irrespective of their IgG status. In contrast, women with positive IgG while negative neutralizing antibodies showed a similar risk of subsequent infection as those with neither neutralizing nor IgG antibodies. Interpretation: The findings indicate that naturally acquired neutralizing antibodies are associated with a substantially reduced risk of subsequent homotypic infection. Funding: National Natural Science Foundation of China ; The Fujian Province Health Education Joint Research Project; Xiamen Science and Technology Major Project; Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences; and Xiamen Innovax. Declaration of Interest: We declare no competing interests. Ethical Approval: Written informed consent was obtained from all participants, and the trial was conducted in accordance with Good Clinical Practice and was approved by independent ethics committees.

Immunogenicity of Plant-Produced Human Papillomavirus (HPV) Virus-Like Particles (VLPs).

Cervical cancer is ranked fourth among the top cancers in women and is the second most common cancer in low- and middle-income regions, with ~570,000 new cases reported in 2018, which attributed to 84% of worldwide cervical cancer cases. Three commercially available prophylactic Human papillomavirus (HPV) vaccines are effective at preventing HPV infections. However, these vaccines are expensive due to their complex production systems, therefore limiting their use in developing countries. Recently, the use of plants to produce vaccines has emerged as a cost-effective alternative to conventionally used expression systems. Here, L1 proteins of eight high-risk (HPV 16, 18, 31, 33, 35, 45, 52, and 58) and two low risk (HPV 6 and 34) HPV types were successfully expressed in Nicotiana benthamiana, and transmission electron microscopy (TEM) analysis showed the presence of VLPs and/or capsomeres. Immunogenicity studies were conducted in mice utilizing HPV 35, 52, and 58 and showed that type-specific L1-specific antibodies were produced which were able to successfully neutralize homologous HPV pseudovirions in pseudovirion-based neutralization assays (PBNAs). This work demonstrated the potential for using plant-based transient expression systems to produce affordable and immunogenic HPV vaccines, particularly for developing countries.

Evaluation of serological assays to monitor antibody responses to single-dose HPV vaccines

IntroductionWhether existing serological assays are sufficiently robust to measure the lower antibody levels expected following single-dose HPV vaccination is unknown. MethodsWe evaluated seven assays measuring HPV-16/18 immunological responses overall and by number of doses in 530 serum samples from participants receiving varying doses of Cervarix or Gardasil up to 36-months post-vaccination. Serum was evaluated by simplex (HPV-16 ELISA, HPV-18 ELISA), multiplex (LIA-4, VLP-MIA, M9ELISA, GST-L1), and high-throughput pseudovirion-based neutralization assays (HT-PBNA), and results were compared to the gold standard HPV-16/18 secreted alkaline phosphatase neutralization assay (SEAP-NA). Reproducibility was assessed by the coefficient of variation (CV) and intraclass correlation coefficient (ICC). Percent agreement, Pearson correlation, and weighted-kappa were used to assess validity. Determinants of seronegativity were evaluated by chi-squared test. ResultsHPV-16: Seropositivity range was 97.1–99.5% for single dose and 98.8–99.8% overall. CV range was 4.0–18.0% for single dose and 2.9–19.5% overall. ICC range was 0.77–0.99 for single dose and 0.74–0.99 overall. Correlation with SEAP-NA range was 0.43–0.85 for single dose and 0.51–0.90 overall. Weighted-kappa range was 0.34–0.82 for single dose and 0.45–0.84 overall. HPV-18: Seropositivity range was 63.9–94.7% for single dose and 86.2–97.9% overall. CV range was 8.1–18.2% for single dose and 4.6–18.6% overall. ICC range was 0.75–0.99 for single dose and 0.83–0.99 overall. Correlation with SEAP-NA range was 0.31–0.99 for single dose and 0.27–0.96 overall. Weighted-kappa range was 0.35–0.83 for single dose and 0.45–0.84 overall. HPV-16 seronegativity was <5% for all assays. HPV-18 seronegativity range was 5.5–17.3%. For LIA-4 and GST-L1 where the proportion of seronegativity was >10%, the strongest correlates of seronegativity were receiving a single vaccine dose and receiving Gardasil. Conclusions:These results support the utility of existing serological assays to monitor antibody responses following single-dose HPV vaccination.

Monitoring Neutralization Property Change of Evolving Hantaan and Seoul Viruses with aNovel Pseudovirus-Based Assay.

The Hantaan virus (HTNV) and Seoul virus (SEOV) mutants have accumulated over time. It is important to determine whether their neutralizing epitopes have evolved, thereby making the current vaccine powerless. However, it is impossible to determine by using traditional plaque reduction neutralization test(PRNT), because it requires large numbers of live mutant strains. Pseudovirus-based neutralization assays (PBNA) were developed by employing vesicular stomatitis virus (VSV) backbone incorporated with HTNV or SEOV glycoproteins (VSVΔG*-HTNVG or VSVΔG*-SEOVG). 56 and 51 single amino acid substitutions of glycoprotein (GP) in HTNV and SEOV were selected and introduced into the reference plasmid. Then the mutant pseudoviruses were generated and tested by PBNA. The PBNA results were highly correlated with PRNT ones with R2 being 0.91 for VSVΔG*-HTNVG and 0.82 for VSVΔG*-SEOVG. 53 HTNV mutant pseudoviruses and 46 SEOV mutants were successfully generated. Importantly, by using PBNA, we found that HTNV or SEOV immunized antisera could neutralize all the corresponding 53 HTNV mutants or the 46 SEOV mutantsrespectively. The novel PBNA enables us to closely monitor the effectiveness of vaccines against large numbers of evolving HTNV and SEOV. And the current vaccine remains to be effective for the naturally occurring mutants.

Immunogenicity and safety of the AS04-HPV-16/18 and HPV-6/11/16/18 human papillomavirus vaccines in asymptomatic young women living with HIV aged 15–25 years: A phase IV randomized comparative study

BackgroundWomen living with HIV (WLWH) are at higher risk of acquisition and progression of human papillomavirus (HPV) infection. Evidence on effect of HPV vaccination in this population is limited. MethodsThis phase IV randomized controlled observer-blind study assessed immunogenicity and safety of two HPV vaccines (AS04-HPV-16/18 vs. 4vHPV) given in WLWH (stage 1) and HIV- females aged 15–25 years. Co-primary endpoints were to demonstrate, in WLWH subjects, non-inferiority (and if demonstrated, superiority) of AS04-HPV-16/18 vs. 4vHPV for HPV-16 and HPV-18 by pseudovirion-based neutralization assay (PBNA) at month 7 and safety. Non-inferiority criteria was lower limit (LL) of the 95% confidence interval (CI) of the GMT ratio AS04-HPV-16/18/4vHPV above 0.5, in the according to protocol population. NCT01031069 FindingsAmong 873 subjects recruited between 26-Oct-2010 and 14-May-2015, 546 were randomized (1:1) and received at least one vaccine dose (total vaccinated cohort, TVC): 257 were WLWH (129 AS04-HPV-16/18; 128 4vHPV) and 289 were subjects without HIV (144 AS04-HPV-16/18; 145 4vHPV). Baseline CD4 cell count in WLWH was at least 350 cells/mm3.At month 7, AS04-HPV-16/18 showed immunological superiority to 4vHPV in WLWH. Neutralizing anti-HPV-16 and HPV-18 antibody GMTs were 2·74 (95% CI: 1·83; 4·11) and 7·44 (95% CI: 4·79; 11·54) fold higher in AS04-HPV-16/18 vs. 4vHPV (LL of the GMT ratio >1 in TVC, p<0·0001), respectively. Similar results were observed by ELISA up to month 24.Solicited local and general symptoms were in line with product labels. The number of reported serious adverse events (SAEs) was balanced throughout the study. InterpretationBoth vaccines showed an acceptable safety profile in all subjects. Despite the absence of an immunological correlate of protection for HPV, differences in immune responses elicited by the vaccines especially for HPV-18 may translate into longer lasting or more robust protection against cervical cancer with the AS04-HPV-16/18 vaccine in WLWH. FundingGlaxoSmithKline Biologicals S.A. funded this study (NCT01031069) and related publications. Trial registrationwww.clinicaltrials.gov - NCT01031069

Structural basis of transmembrane coupling of the HIV-1 envelope glycoprotein

The prefusion conformation of HIV-1 envelope protein (Env) is recognized by most broadly neutralizing antibodies (bnAbs). Studies showed that alterations of its membrane-related components, including the transmembrane domain (TMD) and cytoplasmic tail (CT), can reshape the antigenic structure of the Env ectodomain. Using nuclear magnetic resonance (NMR) spectroscopy, we determine the structure of an Env segment encompassing the TMD and a large portion of the CT in bicelles. The structure reveals that the CT folds into amphipathic helices that wrap around the C-terminal end of the TMD, thereby forming a support baseplate for the rest of Env. NMR dynamics measurements provide evidences of dynamic coupling across the TMD between the ectodomain and CT. Pseudovirus-based neutralization assays suggest that CT-TMD interaction preferentially affects antigenic structure near the apex of the Env trimer. These results explain why the CT can modulate the Env antigenic properties and may facilitate HIV-1 Env-based vaccine design.