Pseudovirion-based Neutralization Assay Research Articles

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.

Immune Response Following Quadrivalent Human Papillomavirus Vaccination in Women After Hematopoietic Allogeneic Stem Cell Transplant

Human papillomavirus (HPV) infection is found in about 40% of women who survive allogeneic hematopoietic stem cell transplant and can induce subsequent neoplasms. To determine the safety and immunogenicity of the quadrivalent HPV vaccine (HPV-6, -11, -16, and -18) in clinically stable women post-allogeneic transplant compared with female healthy volunteers. Participants received the quadrivalent HPV vaccine in intramuscular injections on days 1 and 2 and then 6 months later. This prospective, open-label phase-1 study was conducted in a government clinical research hospital and included clinically stable women posttransplant who were or were not receiving immunosuppressive therapy compared with healthy female volunteers age 18 to 50 years who were followed up or a year after first receiving quadrivalent HPV vaccination. The study was conducted from June 2, 2010, until July 19, 2016. After all of the results of the study assays were completed and available in early 2018, the analysis took place from February 2018 to May 2019. Anti-HPV-6, -11, -16, and -18-specific antibody responses using L1 virus-like particle enzyme-linked immunosorbent assay were measured in serum before (day 1) and at months 7 and 12 postvaccination. Anti-HPV-16 and -18 neutralization titers were determined using a pseudovirion-based neutralization assay. Of 64 vaccinated women, 23 (35.9%) were receiving immunosuppressive therapy (median age, 34 years [range, 18-48 years]; median 1.2 years posttransplant), 21 (32.8%) were not receiving immunosuppression (median age, 32 years [range, 18-49 years]; median 2.5 years posttransplant), and 20 (31.3%) were healthy volunteers (median age, 32 years [range, 23-45 years]). After vaccine series completion, 18 of 23 patients receiving immunosuppression (78.3%), 20 of 21 not receiving immunosuppression (95.2%), and all 20 volunteers developed antibody responses to all quadrivalent HPV vaccine types (P = .04, comparing the 3 groups). Geometric mean antibody levels for each HPV type were higher at months 7 and 12 than at baseline in each group (all geometric mean ratios >1; P < .001) but not significantly different across groups. Antibody and neutralization titers for anti-HPV-16 and anti-HPV-18 correlated at month 7 (Spearman ρ = 0.92; P < .001 for both). Adverse events were mild and not different across groups. Treatment with the HPV vaccination was followed by strong, functionally active antibody responses against vaccine-related HPV types and no serious adverse events. These findings suggest that HPV vaccination may be safely administered to women posttransplant to potentially reduce HPV infection and related neoplasia. ClinicalTrials.gov Identifier: NCT01092195.

Peak neutralizing and cross-neutralizing antibody levels to human papillomavirus types 6/16/18/31/33/45/52/58 induced by bivalent and quadrivalent HPV vaccines

We performed an independent comparison of neutralizing and cross-neutralizing antibody (ab) levels seven months after initiation of three-dose, six-month vaccination schedules with the bivalent and quadrivalent human papillomavirus (HPV) vaccines in adolescent Finnish and Indian females, respectively. We used a semi-automated Pseudovirion-Based Neutralization Assay and observed significantly higher HPV16/18 peak ab-levels in bivalent as compared to quadrivalent vaccine recipients. Bivalent vaccine induced cross-neutralizing HPV31/33/45/52/58 antibodies significantly more frequently and to higher levels than the quadrivalent vaccine. The correlation of bivalent vaccine-induced HPV45 ab-levels with HPV16/18 ab-levels was stronger than that of corresponding quadrivalent vaccine-induced ab-levels, suggesting a qualitatively different cross-reactive response. Our findings on the comparison of the immunogenicity of two HPV vaccine tested in two different populations indicate that further head-to-head studies are warranted.

Age distribution of human papillomavirus infection and neutralizing antibodies in healthy Chinese women aged 18–45 years enrolled in a clinical trial

ObjectivesData from clinical trials of human papillomavirus (HPV) vaccines showed that women naïve (negative for both type-specific antibodies and DNA) to vaccine types would derive benefit from vaccination; therefore, an understanding of the proportion of naïve women in different age groups is important for developing HPV vaccination strategies. MethodsFrom November 2012 to April 2013, a total of 7372 healthy women aged 18–45 years were recruited in five provinces in China. Cervical specimens and serum samples were collected for each woman at entry. Cervical specimens were first tested by the HPV DNA enzyme immunoassay method; if positive, the specimens were then tested by reverse hybridization line probe assay and HPV-16 and HPV-18 specific polymerase chain reactions. Neutralizing antibodies against HPV-16 or HPV-18 were tested with a pseudovirion-based neutralization assay. ResultsThe overall prevalence of high-risk HPV DNA was 14.8% (1088/7367, 95% CI 14.0–15.6), and the seroprevalence of neutralizing antibodies against HPV-16 and HPV-18 was 12.6% (925/7367) and 4.9% (364/7367), respectively. In younger women (18–26 years) and middle-aged women (27–45 years), 83.8% (3116/3719) and 81.4% (2968/3648) were naïve to both HPV-16 and HPV-18 (both neutralizing antibodies and DNA were negative), respectively. In addition, 98.5% (3664/3719) and 98.0% (3575/3648) of the younger or middle-aged women were naïve to at least one HPV type (HPV-16 or HPV-18). DiscussionThis study revealed that the majority of Chinese women aged 18–26 years and 27–45 years were naïve to both HPV-16 and HPV-18 and would thus derive full benefit from bivalent HPV vaccination.

Substitution of Human Papillomavirus Type 16 L2 Neutralizing Epitopes Into L1 Surface Loops: The Effect on Virus-Like Particle Assembly and Immunogenicity.

Cervical cancer caused by infection with human papillomaviruses (HPVs) is the fourth most common cancer in women globally, with the burden mainly in developing countries due to limited healthcare resources. Current vaccines based on virus-like particles (VLPs) assembled from recombinant expression of the immunodominant L1 protein are highly effective in the prevention of cervical infection; however, these vaccines are expensive and type-specific. Therefore, there is a need for more broadly protective and affordable vaccines. The HPV-16 L2 peptide sequences 108-120, 65-81, 56-81, and 17-36 are highly conserved across several HPV types and have been shown to elicit cross-neutralizing antibodies. To increase L2 immunogenicity, L1:L2 chimeric VLPs (cVLP) vaccine candidates were developed. The four L2 peptides mentioned above were substituted into the DE loop of HPV-16 L1 at position 131 (SAC) or in the C-terminal region at position 431 (SAE) to generate HPV-16-derived L1:L2 chimeras. All eight chimeras were transiently expressed in Nicotiana benthamiana via Agrobacterium tumefaciens-mediated DNA transfer. SAC chimeras predominantly assembled into higher order structures (T = 1 and T = 7 VLPs), whereas SAE chimeras assembled into capsomeres or formed aggregates. Four SAC and one SAE chimeras were used in vaccination studies in mice, and their ability to generate cross-neutralizing antibodies was analyzed in HPV pseudovirion-based neutralization assays. Of the seven heterologous HPVs tested, cross-neutralization with antisera specific to chimeras was observed for HPV-11 (SAE 65-18), HPV-18 (SAC 108-120, SAC 65-81, SAC 56-81, SAE 65-81), and HPV-58 (SAC 108-120). Interestingly, only anti-SAE 65-81 antiserum showed neutralization of homologous HPV-16, suggesting that the position of the L2 epitope display is critical for maintaining L1-specific neutralizing epitopes.

Establishment and evaluation of a triple-color human papillomavirus pseudovirion neutralization assay

Objective: To establish a triple-color pseudovirion-based neutralization assay (PBNA) and evaluate its capability of detecting immunogenicity of the sera generated by the immunization of HPV 9-valent vaccine. Methods: HPV pseudovirus (PsVs) 6/11/16/18/31/33/45/52/58 with the encapsidated fluorescence expressing red fluorescent plasmid N31-MCHREEY, green fluorescent N31-EGFP or blue fluorescent N31-mTagBFP were generated. The concentration of HPV PsVs and the infection titers of HPV PsVs were detected by double-antibody sandwich ELISA and TCID(50), respectively. The single- and triple color HPV 16/33/45 PsVs were used to detect the neutralization titers of mice sera immunized with HPV 9-valent vaccine and confirmed the accuracy and specificity of the triple-color PBNAs. Then, the single- and triple color HPV 6/11/18/31/33/45/52/58 PsVs were employed to detect the neutralization titers of cynomolgus macaques sera immunized with HPV 9-valent vaccine and determined whether the triple-color PBNAs could be applied to evaluate the immunogenicity of the sera generated by the immunization of HPV9-valent vaccine. Results: The concentration of HPV16 PsVs encapsulating green, red or blue fluorescent plasmid was 5.0 to 6.0 μg/ml and HPV6/11/18/31/33/45/52/59 triple-color HPV PsVs was about 1.0 to 3.0 μg/ml. 9 types HPV PsVs containing EGFP, Mcherry or mTagBFP reporter plasmid were obtained and the concentration can meet the need of neutralization detection. 9 types single-color fluorescent HPV PsVs had similar infectivity against 293FT cells with the infection titer values between 1×10(4) and 1×10(5). The results of PBNAs showed that there was no significant difference in the anti-HPV neutralization titers of mice sera induced by HPV 9-valent vaccine between single-color and triple-color HPV16/33/45 PsVs (P>0.05). Similarly, there was also no significant difference in the anti-HPV neutralization titers of cynomolgus macaques sera induced by HPV 9-valent vaccine between single-color and triple-color HPV6/11/18/31/33/45/52/58 PsVs (P>0.05). Conclusion: We successfully established the triple-color PBNAs and verified the accuracy and specificity of triple-color PBNAs consistent with single-color PBNAs. The triple-color PBNAs can be applied to evaluate the immunogenicity of HPV 9-valent vaccine's immune serum.

Epitope clustering analysis for vaccine-induced human antibodies in relationship to a panel of murine monoclonal antibodies against HPV16 viral capsid

Human papillomavirus (HPV) type 16 is the most common type implicated as the etiological agent that causes cervical cancer. The marketed prophylactic vaccines against HPV infection are composed of virus-like particles (VLPs) assembled from the recombinant major capsid protein L1. Elicitation of functional and neutralizing antibodies by vaccination is the mode of action by which the vaccines prevent the viral infection. In this study, a panel of murine mAbs against HPV16 L1 were generated and comprehensively characterized with respect to their mapping to the epitope spectrum on the viral capsid. These mAbs were categorized into five epitope bins by two different methods based on the pairwise cross-inhibition and competition with human polyclonal antibodies. In addition, a preliminary demonstration of the spatial relationship of the epitopes recognized by these mAbs was performed using a cross-blocking assay with a well-characterized human mAb, 26D1. Interestingly, two mAbs recognizing different epitopes were found to act synergistically in the pseudovirion-based neutralization assay (PBNA). To facilitate cross-lab and cross-study comparison, the international standard (IS) serum 05/134 was used to calibrate the mAbs as well as the human serum samples from the HPV16/18 vaccine recipients. The neutralizing mAbs, particularly those that recognizing immunodominant epitopes, would be useful in developing epitope-specific assays for monitoring the vaccine production process and for serological assessment.

Sequential immunization with consensus influenza hemagglutinins raises cross-reactive neutralizing antibodies against various heterologous HA strains

Seasonal and emerging epidemics caused by influenza virus remain as a public health concern and an economic burden. The weak immunogenicity of conserved epitopes on hemagglutinin that induces broad protective immune responses is the main obstacle to the development of universal vaccines. In the present report, we designed the cross-subtypic sequential vaccination strategy and evaluated its neutralizing antibody (nAb) activity by pseudovirus-based neutralization assays. The results clearly indicated that compared with traditional vaccines strategy, the cross-subtypic sequential immunization could significantly induce a broad serum cross-reactive nAb response in mice as well as against homologous strains, and provide protection from heterologous virus PR8 (H1N1) challenge. Furthermore, we isolated two monoclonal antibodies from sequentially immunized mice, which had potent broadly neutralizing activity against multiple influenza strains. These data suggest the feasibility of sequential immunization in universal flu vaccine development.

Progress in clinical immunology of human papillomavirus vaccines

Persistent human papillomavirus (HPV) infections have been identified as the main causes of cervical cancer. HPV vaccination has become the preferred option for the prevention of cervical cancer and pre-cancerous lesions. The effectiveness of vaccination could be indirectly reflected in the level of anti-HPV antibody. Therefore, immunogenicity analysis plays an important role in the clinical evaluation of HPV vaccines. Up to now, three HPV vaccines including Cervarix®, Gardasil® and Gardasil® 9 have been licensed in many countries, but a standard assay for assessing the immunogenicity of HPV vaccines has not been established. Currently, pseudovirion-based neutralization assay (PBNA), ELISA and competitive luminex immunoassay(cLIA) are the three major assays widely used in clinical trials of HPV vaccines. This study reviewed the traits of the three assays, the immunogenicity and durability of the three HPV vaccines, as well as the immune responses induced in different populations. Key words: Human papillomavirus; Vaccine; Immunogenicity; Cervical cancer

Development of a Triple-Color Pseudovirion-Based Assay to Detect Neutralizing Antibodies against Human Papillomavirus.

Pseudovirion-based neutralization assay is considered the gold standard method for evaluating the immune response to human papillomavirus (HPV) vaccines. In this study, we developed a multicolor neutralization assay to simultaneously detect the neutralizing antibodies against different HPV types. FluoroSpot was used to interpret the fluorescent protein expression instead of flow cytometry. The results of FluoroSpot and flow cytometry showed good consistency, with R2 > 0.98 for the log-transformed IC50 values. Regardless of the reporter color, the single-, dual-, and triple-color neutralization assays reported identical results for the same samples. In low-titer samples from naturally HPV-infected individuals, there was strong agreement between the single- and triple-color assays, with kappa scores of 0.92, 0.89, and 0.96 for HPV16, HPV18, and HPV58, respectively. Good reproducibility was observed for the triple-color assay, with coefficients of variation of 2.0%–41.5% within the assays and 8.3%–36.2% between the assays. Three triple-color systems, HPV16-18-58, HPV6-33-45, and HPV11-31-52, were developed that could evaluate the immunogenicity of a nonavalent vaccine in three rounds of the assay. With the advantages of an easy-to-use procedure and less sample consumption, the multiple-color assay is more suitable than classical assays for large sero-epidemiological studies and clinical trials and is more amenable to automation.

The agmatine-containing poly(amidoamine) polymer AGMA1 binds cell surface heparan sulfates and prevents attachment of mucosal human papillomaviruses.

The agmatine-containing poly(amidoamine) polymer AGMA1 was recently shown to inhibit the infectivity of several viruses, including human papillomavirus 16 (HPV-16), that exploit cell surface heparan sulfate proteoglycans (HSPGs) as attachment receptors. The aim of this work was to assess the antiviral activity of AGMA1 and its spectrum of activity against a panel of low-risk and high-risk HPVs and to elucidate its mechanism of action. AGMA1 was found to be a potent inhibitor of mucosal HPV types (i.e., types 16, 31, 45, and 6) in pseudovirus-based neutralization assays. The 50% inhibitory concentration was between 0.34 μg/ml and 0.73 μg/ml, and no evidence of cytotoxicity was observed. AGMA1 interacted with immobilized heparin and with cellular heparan sulfates, exerting its antiviral action by preventing virus attachment to the cell surface. The findings from this study indicate that AGMA1 is a leading candidate compound for further development as an active ingredient of a topical microbicide against HPV and other sexually transmitted viral infections.

Concordance assessment between a multiplexed competitive Luminex immunoassay, a multiplexed IgG Luminex immunoassay, and a pseudovirion-based neutralization assay for detection of human papillomaviruse types 16 and 18

There are two approved vaccines against anogenital human papillomaviruses (HPV) and a nine-valent vaccine is currently under development. Although there are several assays available to measure antibodies elicited by HPV vaccines, there is currently no global standard for HPV antibody assays. In the current study, antibody responses to HPV16 and HPV18 among young men and women vaccinated with a quadrivalent HPV6/11/16/18 (qHPV) vaccine were assessed using three assays: a competitive Luminex immunoassay (cLIA-4) which measures antibodies directed against a single neutralizing epitope, an immunoglobulin G Luminex immunoassay (IgG-9) which measures both neutralizing and non-neutralizing antibodies, and a pseudovirion-based neutralization assay (PBNA) which functionally measures the full spectra of neutralizing antibodies. To assess HPV16 and HPV18 responses, 648 and 623 serum samples, respectively, were selected from three prior clinical trials of the qHPV vaccine. For each HPV type, the functional relationship between pairs of assay methods was estimated using a linear statistical relationship model and Pearson correlation coefficients. For both HPV16 and HPV18, the agreement between the PBNA and IgG-9 (correlation coefficients of 0.95 and 0.93, respectively) was comparable to the agreement between the cLIA-4 and IgG-9 (correlation coefficients of 0.92 and 0.92, respectively). Of 478 and 399 post-dose 3 samples that tested positive in the cLIA-4, 100% and 98% also tested positive in the IgG-9 and PBNA. The proportion of cLIA-4 seronegative post-dose 3 samples that tested positive in both the IgG-9 and PBNA was 68% (19/28) for HPV16 and 58% (71/122) for HPV18. The data demonstrate the three assays are highly correlated and reflect the measurement of neutralizing antibody. This further verifies that the IgG-9 assay, which is used to assess the immune response to an investigational nine-valent vaccine, is similarly sensitive to the PBNA for the detection of HPV16 and HPV18 neutralizing antibodies.

Neutralizing and cross-neutralizing antibody titres induced by bivalent and quadrivalent human papillomavirus vaccines in the target population of organized vaccination programmes

Aim of this investigator-initiated study was to evaluate and compare the titres of neutralizing and cross-neutralizing antibodies (NAbs) induced by the bivalent (Cervarix®) and quadrivalent (Gardasil®) HPV vaccines in a cohort of girls aged 11–13 years from organized vaccination programmes. To this aim, HPV16 and HPV18 NAbs were measured by pseudovirion-based neutralization assays in serum collected at 1–6 months after the third vaccine dose in 107 girls vaccinated with Cervarix® and 126 vaccinated with Gardasil®, while HPV31 and HPV45 cross-NAbs were tested in the first 50 consecutive girls of both vaccine groups. The results of this study demonstrated that all vaccinated girls developed HPV16 and HPV18 NAbs, with the exception of two Gardasil® vaccinees with undetectable HPV18 NAbs. Geometric mean titres (GMTs) of both HPV16 and HPV18 NAbs were significantly higher in Cervarix® than in Gardasil® vaccinees [HPV16 NAb GMT 22,136 (95% CI, 18,811–26,073) vs 5092 (4230–6151), respectively; P<0.0001; HPV18 NAb GMT 11,962 (9536–14,363) vs 1804 (1574-2110), respectively; P<0.0001]. Cross-NAbs to HPV31 and HPV45 were detected more frequently Cervarix® (HPV31 NAb positivity rates 92.7% and 36%, respectively; P<0.05) than in Gardasil® vaccinees (HPV45 NAb positivity rates 56% and 6%, respectively; P<0.0001). The titres of cross-NAbs against HPV31 and HPV45 were also significantly higher in Cervarix® than in Gardasil® vaccinees [HPV31 NAb GMT 157.2 (95% CI, 92–269) vs 13.0 (6.5–25.8), respectively; P<0.0001; HPV45 NAb GMT 4.7 (2.1–10.2) vs 1.3 (0.3–3.1), respectively; P<0.01].In conclusion, in adolescent girls vaccinated within organized vaccination programmes, HPV vaccines drive the generation not only of NAbs to HPV vaccine types, but also of cross-NAbs. The bivalent vaccine induced significantly higher HPV16 and HPV18 NAb titres and more frequently and at higher titre HPV31 and HPV45 cross-NAbs than the quadrivalent vaccine.

Measurement of neutralizing serum antibodies of patients vaccinated with human papillomavirus L1 or L2-based immunogens using furin-cleaved HPV Pseudovirions.

Antibodies specific for neutralizing epitopes in either Human papillomavirus (HPV) capsid protein L1 or L2 can mediate protection from viral challenge and thus their accurate and sensitive measurement at high throughput is likely informative for monitoring response to prophylactic vaccination. Here we compare measurement of L1 and L2-specific neutralizing antibodies in human sera using the standard Pseudovirion-Based Neutralization Assay (L1-PBNA) with the newer Furin-Cleaved Pseudovirion-Based Neutralization Assay (FC-PBNA), a modification of the L1-PBNA intended to improve sensitivity towards L2-specific neutralizing antibodies without compromising assay of L1-specific responses. For detection of L1-specific neutralizing antibodies in human sera, the FC- PBNA and L1-PBNA assays showed similar sensitivity and a high level of correlation using WHO standard sera (n = 2), and sera from patients vaccinated with Gardasil (n = 30) or an experimental human papillomavirus type 16 (HPV16) L1 VLP vaccine (n = 70). The detection of L1-specific cross-neutralizing antibodies in these sera using pseudovirions of types phylogenetically-related to those targeted by the L1 virus-like particle (VLP) vaccines was also consistent between the two assays. However, for sera from patients (n = 17) vaccinated with an L2-based immunogen (TA-CIN), the FC-PBNA was more sensitive than the L1-PBNA in detecting L2-specific neutralizing antibodies. Further, the neutralizing antibody titers measured with the FC-PBNA correlated with those determined with the L2-PBNA, another modification of the L1-PBNA that spacio-temporally separates primary and secondary receptor engagement, as well as the protective titers measured using passive transfer studies in the murine genital-challenge model. In sum, the FC-PBNA provided sensitive measurement for both L1 VLP and L2-specific neutralizing antibody in human sera. Vaccination with TA-CIN elicits weak cross-protective antibody in a subset of patients, suggesting the need for an adjuvant.

Comparison of the immunogenicity of Cervarix® and Gardasil® human papillomavirus vaccines for oncogenic non-vaccine serotypes HPV-31, HPV-33, and HPV-45 in HIV-infected adults

Individuals infected with human immunodeficiency virus (HIV) have excess risk of developing human papillomavirus (HPV)-related disease. A substantial fraction of HPV-associated cancers is caused by HPV serotypes not included in the currently available vaccines. Among healthy women, both Cervarix® (HPV-16/18, GlaxoSmithKline Biologicals, GSK) and Gardasil® (HPV-6/11/16/18, Merck) have demonstrated partial cross-protection against certain oncogenic non-vaccine HPV-types. Currently, there are no available data on vaccine-induced cross-protection in men and little is known about cross-reactive immunity after HPV-vaccination of HIV-infected individuals.In an investigator-initiated trial, we randomized 91 HIV-positive men and women to receive vaccination with Cervarix® or Gardasil®. The HPV-DNA status of the participants was determined with pcr before and after immunization. Cross-reactive antibody responses against HPV-31, HPV-33, and HPV-45 were evaluated for up to 12 months using a pseudovirion-based neutralization assay (PBNA). Geometric mean antibody titers (GMTs) were compared among vaccine groups and genders at 7 and 12 months.Both vaccines induced anti-HPV-31, -33, and -45 neutralizing antibodies in participants who were seronegative and HPV-DNA negative for those types at study entry. Geometric mean antibody titers were comparable between vaccine groups. Interestingly, anti-HPV-31 and -33 antibody titers were higher among women compared with men at 7 and 12 months.In conclusion, both licensed HPV-vaccines induced cross-neutralizing antibodies against frequent oncogenic non-vaccine serotypes HPV-31, HPV-33, and HPV-45 in HIV-infected adults, and women had greater serological responses against HPV-31 and -33 compared with men.