Measurement of Human Papillomavirus-Specific Antibodies Using a Pseudovirion-Based ELISA Method.

Human papillomavirus (HPV) vaccines are safe and effective in preventing HPV infection and cervical precancers. Neutralizing antibodies are thought to be the primary mechanism of protection for HPV vaccines, although the exact level required for protection has not been identified. Three common serological assays used in clinical trials to measure HPV antibodies are HPV pseudovirion-based neutralization assay (PBNA), competitive or total Luminex immunoassays (cLIA or LIA) and VLP-based enzyme linked immunosorbent assays (ELISA). While PBNA is the gold-standard for measuring neutralizing antibodies (NAb), it is labor intensive. Luminex immunoassay and VLP-ELISA are rapid and high throughput, but their reagents and equipment can be difficult to source. Nevertheless, data generated from these assays generally correlate well with PBNA. Here, we described a simplified high-throughput PsV-based ELISA for HPV antibody measurement, to circumvent some of the limitations of existing assays. Using this assay, we were able to differentiate HPV-specific IgG and IgM, and found a strong correlation between HPV-specific IgG and NAb levels, as previously determined by PBNA. This assay platform is simpler and less time-consuming than PBNA. In addition, the materials can be readily produced and obtained commercially. This assay can be used as an alternative method to measure HPV antibodies.

Persistence of Immunity When Using Different Human Papillomavirus Vaccination Schedules and Booster-Dose Effects 5 Years After Primary Vaccination.

Background: There are limited data regarding the duration of immunity induced by different human papillomavirus (HPV) vaccination schedules and the immunogenicity of a booster dose of both bivalent HPV vaccine (bHPV) or quadrivalent HPV vaccine (qHPV). Methods: Follow-up of a nonrandomized clinical trial to evaluate the 5-year antibody persistence of the bHPV in girls (age, 9-10 years) and women (age, 18-24 years). Noninferiority of the 2-dose versus 3-dose schedule among girls was evaluated at months 54 (n = 639) and 64 (n = 990). Girls vaccinated with a 2-dose schedule of bHPV or qHPV received a booster dose of either vaccine at month 61. Immunogenicity was measured using a virus-like particle-based enzyme-linked immunosorbent assay. Geometric mean titers (GMTs) for HPV16/18 were estimated after stratification by vaccination schedule and age group. Results: At months 54 and 64, the 2-dose schedule remained noninferior to the 3-dose schedule. GMTs remained above natural infection levels across all age groups up to 64 months. After the booster, anti-HPV16/18 GMTs increased exponentially with the same pattern, regardless of vaccine administered. No safety concerns were identified with the booster dose. Conclusions: A 2-dose schedule is highly immunogenic in girls, suggesting a high immune memory. Thus, a booster dose is likely to be unprofitable, considering the low global immunization coverage. Clinical Trials Registration: NCT01717118.

Long-term study of a quadrivalent human papillomavirus vaccine.

BACKGROUND: We present a long-term safety, immunogenicity, and effectiveness study of a quadrivalent human papillomavirus (HPV4) vaccine. METHODS: Sexually naive boys and girls aged 9 to 15 years (N = 1781) were assigned (2:1) to receive HPV4 vaccine or saline placebo at day 1 and months 2 and 6. At month 30, the placebo group (n = 482) received HPV4 vaccine following the same regimen and both cohorts were followed through month 96. Subjects ≥ 16 years were eligible for effectiveness evaluations. The primary objective was to evaluate the long-term anti-HPV6/11/16/18 serological levels. The secondary objective was to estimate vaccine effectiveness against HPV6/11/16/18-related persistent infection or disease. RESULTS: For each of the HPV4 vaccine types, vaccination-induced anti-HPV response persisted through month 96. Among 429 subjects who received HPV4 vaccine at a mean age of 12, none developed HPV6/11/16/18-related disease or persistent infection of ≥ 12 months' duration. Acquisition of new sexual partners (among those ≥ 16 years) was ∼1 per year. Subjects receiving HPV4 vaccine at month 30 (mean age 15 years) had a similar baseline rate of seropositivity to ≥ 1 of the 4 HPV types to those vaccinated at day 1 (mean age 12 years; 1.9% [9 of 474] vs 1.7% [20 of 1157]); however, 4 of the 9 subjects vaccinated at the later age were seropositive to 3 vaccine types, indicating previous HPV exposure. No new significant serious adverse events were observed for 8 years postvaccination in both genders. CONCLUSIONS: When administered to adolescents, the HPV4 vaccine demonstrated durability in clinically effective protection and sustained antibody titers over 8 years.

Immunogenicity of quadrivalent HPV vaccine among girls 11 to 13 Years of age vaccinated using alternative dosing schedules: results 29 to 32 months after third dose.

BACKGROUND: Immune response to quadrivalent human papillomavirus (HPV) vaccine delivered at 0, 2, and 6 months in young adolescent females plateaus around 24 months after immunization. Antibody levels >24 months postvaccination using extended dosing schedules is unknown. METHODS: We conducted a follow-up immunogenicity study of adolescent girls in Vietnam who participated in a noninferiority trial to investigate whether immune responses using 3 alternative dosing schedules (0, 3, 9 months; 0, 6, 12 months; or 0, 12, 24 months) are noninferior to the standard schedule at >2 years after immunization. RESULTS: Quadrivalent HPV vaccine immunogenicity delivered on 3 alternative dosing schedules was noninferior for types 6, 11, 16, and 18 at 32 months post-dose 3 compared to the standard schedule. Pre-dose 3 antibody levels for the 0, 12, 24 month schedule were similar to those measured 32-months post-dose 3. CONCLUSIONS: We found similar antibody concentrations ≥29 months after 3 doses of HPV vaccine regardless of dose-timing, and extended schedules do not produce inferior immune responses. Our findings also suggested that 2 doses of HPV vaccine delivered at 0 and 12 months might afford similar protection. Evidence supporting dosing flexibility could be important for national HPV vaccination policies.

Immunogenicity and safety of human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine in healthy boys aged 10-18 years.

PURPOSE: The human papillomavirus (HPV)-16/18 AS04-adjuvanted vaccine (Cervarix) has been shown to be well-tolerated and immunogenic in females aged 10 to 55 years, and up to 100% effective for the prevention of HPV-16/18 infection and associated precancerous cervical lesions in females aged 15 to 25 years. This study is the first to evaluate the immunogenicity and safety of the vaccine in males. METHODS: Healthy males aged 10 to 18 years were randomized (2:1 ratio) to receive HPV-16/18 AS04-adjuvanted vaccine (n = 181) or hepatitis B virus (HBV) control vaccine (n = 89) at 0, 1, and 6 months, and were followed for 7 months. RESULTS: All initially seronegative subjects in the HPV-16/18 group seroconverted for HPV-16 and 18 (ELISA) at month 2. At month 7, all subjects were seropositive, and the HPV-16 and -18 antibody levels were, respectively, four- and twofold higher than at month 2. The anti-HPV-16 and -18 antibody responses for males aged 10 to 18 years and 10 to 14 years, respectively, were higher than those reported for females aged 15 to 25 years and 10 to 14 years, respectively, in a previous study. The reactogenicity profiles of the HPV-16/18 AS04 and HBV vaccines were similar, except that pain and swelling at the injection site were more common in the HPV-16/18 group. However, vaccine-related symptoms did not affect compliance with the three-dose course, which was equally high (97%) in both groups. CONCLUSIONS: The HPV-16/18 AS04-adjuvanted vaccine is immunogenic and well tolerated in boys aged 10 to 18 years. However, further data on the potential public health benefits of vaccination of boys are required before any recommendations can be made.