Kinetic and HPV infection effects on cross-type neutralizing antibody and avidity responses induced by Cervarix®

Abstract

Background We previously demonstrated that Cervarix® elicits antibody responses against vaccine-related types for which clinical efficacy was demonstrated (HPV-31 and -45). Here, we evaluated the kinetics of neutralization titers and avidity of Cervarix®-induced antibodies up to 36 months of follow-up in unexposed and HPV infected women. Methods A subset of women who participated in the Cost Rica HPV-16/18 Vaccine Trial had pre- and post-vaccination sera tested for antibody responses to HPV-16, -18, -31, -45, and -58 using a pseudovirion-based neutralization assay, and HPV-16 antibody avidity using an HPV-16 L1 VLP (virus-like particle)-based ELISA developed in our laboratory. Results In uninfected women, neutralizing antibody titers did not reach significance until after the 3rd dose for HPV-31 (month 12, p=0.009) and HPV-45 (month 12, p=0.003), but then persisted up to month 36 (HPV-31, p=0.01; HPV-45, p=0.002). Individuals infected with HPV-16 or HPV-31 at enrollment developed a significantly higher median antibody response to the corresponding HPV type after one dose, but there was not a difference between median titers after three doses compared to the HPV negative group. Median HPV-16 antibody avidity and titer increased over time up to month 12; however, the HPV-16 avidity did not correlate well with HPV-16 neutralizing antibody titers at each time point examined, except for month 6. The median avidity levels were higher in HPV-16 infected women at month 1 (p=0.04) and lower in HPV-16 infected women at month 12 (p=0.006) compared to the HPV negative women. Conclusions The persistence of cross-neutralization titers at month 36 suggests cross-reactive antibody responses are likely to persist long-term and are not influenced by infection status at enrollment. However, the weak correlation between avidity and neutralization titers emphasizes the need for examining avidity in efficacy studies to determine if high avidity antibodies play a critical role in protection against infection.

Durable Antibody Responses Following One Dose of the Bivalent Human Papillomavirus L1 Virus-Like Particle Vaccine in the Costa Rica Vaccine Trial

“…Infection inhibition may be more dependent on antibody affinity than simple antigen binding, and we recently found a clear increase in antibody avidity with each of the two boosts in CVT participants who received all three doses (27,28). Possible explanations for the observed one-dose neutralizing activity include: (i) low avidity antibodies may be able to neutralize HPV virions; and (ii) B-cell receptor affinity-dependent selection for plasma cell survival may be the predominant driving force of antibody avidity long term, regardless of the number of doses.…”

A comparative study of two different assay kits for the detection of secreted alkaline phosphatase in HPV antibody neutralization assays

“…For GE, 25 mL of supernatant was incubated with 75 mL of 1X Dilution Buffer, and incubated at 65 C in an oven (Heratherm OMH100, Thermo Scientific) for 45 min. 27,28 After equilibrating the plates to room temperature, 100 mL of substrate was added and incubated in dark at room temperature for 20 min before measuring SEAP activity. For ZiVa, 5 mL of supernatant samples were incubated with 75 mL of SEAP Sample Preparation Solution at 65 C in the oven for 45 min.…”

“…As such, cell-based in vitro neutralization assay is an ideal system to measure the levels of biologically active antibodies in clinical samples. Although different neutralization assays have been reported for HPV, [16][17][18][19][20][21][22][23][24][25] our laboratory has adopted, optimized, and validated [26][27][28][29] a pseudovirion (PsV)-based HPV neutralization assay that was originally reported by Pastrana et al 30 In this assay system, PsV particles that are composed of L1 and L2 capsid proteins from a particular HPV type are used to infect 293TT cells for 72 hr. Because a PsV particle encapsidates a reporter gene during its production, 31,32 magnitude of PsV entry and infection can be measured through the detection of the reporter gene product.…”

“…Using this 293TT cellbased system and secreted alkaline phosphatase (SEAP) as a reporter, we have measured titers of biologically active anti-L1 specific antibodies in HPV L1VLP vaccine recipients as well as in those who were naturally infected with HPVs. 27,28,30 As the number of samples from clinical trials can be large, conducting the cell-based neutralization assay and SEAP assay can be labor-intensive and expensive. This 293TT cell-based neutralization assay takes 72 hr before collecting and storing cell-culture supernatants for the subsequent SEAP assay.…”

Development of Neutralizing Monoclonal Antibodies for Oncogenic Human Papillomavirus Types 31, 33, 45, 52, and 58

“…This is important because the potential for vaccine-induced cross-reactivity has been established. Sera from women immunized with Cervarix (HPV16/HPV18) can neutralize HPV31 and HPV45 in vitro (20,21), presumably due to HPV16 and HPV18 cross-reactivity, respectively. Unlike same-type neutralization, the cross-reactive neutralization is apparent only after three vaccinations at months 0, 1, and 6, and the neutralization activity is reduced by more than a factor of 100.…”