Serological cross reactivity between polyomavirus capsids.

Multiple methods have been used to measure antibodies to polyomavirus virions. In order to have a common method for all polyomaviruses, we developed enzyme immunoassays (EIAs) using virus-like-particles (VLPs) produced in the baculovirus expression system. We tested serum samples from humans and rhesus macaques in VLP-based EIAs for the two human polyomaviruses, BK and JC virus, and two nonhuman primate polyomaviruses, simian virus 40 (SV40) and lymphotropic polyomavirus (LPV). Rhesus sera exhibited low level reactivity to BK and JC, and approximately 10 and 15% of human sera showed low level reactivity to SV40 and LPV, respectively. Competitive inhibition assays with VLP protein demonstrated that the reactivity of rhesus sera against BK and JC VLPs was blocked by both SV40 and the respective human polyomavirus, indicating that the BK and JC assays were detected cross-reacting antibodies. Similarly, the reactivity of the majority of human sera to SV40 was blocked by both SV40 and BK or JC, demonstrating that the SV40 reactivity of human sera is largely due to cross reacting BK and JC antibodies. In contrast, the reactivity of human sera to LPV VLPs was blocked by LPV but not by BK or JC, providing serological evidence for an unknown human polyomavirus related to LPV. SV40 and LPV VLP-based EIAs and competitive inhibition assays with heterologous VLPs provide tools for seroepidemiological studies of possible SV40 and LPV-like infections of humans.

Human papillomavirus capsid antibody response to natural infection and risk of subsequent HPV infection in HIV-positive and HIV-negative women.

The association between seropositivity to virus-like particles (VLP) of human papillomavirus (HPV) types 16, 18, 31, 35, or 45 and subsequent cervical HPV infection was examined in 829 women with HIV and 413 risk-matched HIV-negative women. We found no statistically significant differences between HPV-seropositive and HPV-seronegative women in the risk of a new infection with the homologous HPV type, with the exception of a reduced risk of HPV 45 infections 4.5 years beyond the baseline serology measurement in HIV-positive women [hazard ratio, 0.21; 95% confidence interval (CI), 0.05-0.89]. Among HIV-negative women, HPV seropositivity was not associated with a statistically significant reduced risk of infections with related viruses in the HPV 16, HPV 18, or "other" HPV groups. Among HIV-positive women, HPV seropositivity was associated with a slightly increased risk of infection with group-related viruses, but the differences were only statistically significant for infection with HPV 16 group viruses (hazard ratio, 1.6; 95% CI, 1.1-2.3) in HPV 18-seropositive women and for infections with "other" HPV group viruses in HPV 31-seropositive women (hazard ratio, 1.45; 95% CI, 1.0-2.0). The lack of a protective immune effect from natural infection is most likely due to the low level of antibody elicited by natural HPV infection and/or the potential for reactivation of HPV, especially in HIV-positive women.

Seroreactivity to human papillomavirus (HPV) types 16, 18, or 31 and risk of subsequent HPV infection: results from a population-based study in Costa Rica.

Whether antibodies to human papillomavirus (HPV) capsids, elicited by natural infection, are protective is unknown. This question was addressed in a population-based cohort of 7046 women in Costa Rica by examining the association between baseline seroreactivity to HPV-16, HPV-18, or HPV-31 virus-like particles and the risk of subsequent HPV infection at a follow-up visit 5-7 years after enrollment. Seropositivity to HPV-16, HPV-18, or HPV-31 was not associated with a statistically significant decreased risk of infection with the homologous HPV type [relative risk (RR) and [95% confidence interval (CI)], 0.74 (0.45-1.2), 1.5 (0.83-2.7), and 0.94 (0.48-1.8), respectively]. Seropositivity to HPV-16 or HPV-31 was not associated with a decreased risk of infection with HPV-16 or its genetically related types [RR (95% CI), 0.82 (0.61-1.1) and 0.93 (0.68-1.2), respectively]. Seropositivity to HPV-18 was not associated with a decreased risk of infection with HPV-18 or its genetically related types (RR 1.3; 95% CI 1.0-1.8). Thus, we did not observe immunity, although a protective effect from natural infection cannot be excluded because of the limits of available assays and study designs.

Serum immunoglobulin A response to human papillomavirus type 16 virus-like particles in human immunodeficiency virus (HIV)-positive and high-risk HIV-negative women.

Serum samples from 2008 human immunodeficiency virus (HIV)-positive and 551 HIV-negative women were tested for immunoglobulin A (IgA) to human papillomavirus (HPV) type 16 capsids. IgA seropositivity was lower than previously reported IgG seropositivity (7% vs. 51%), but, like IgG antibodies, HPV 16 IgA was associated with sexual behavior, cervicovaginal HPV 16 DNA, and cytological abnormalities. IgA seropositivity was higher in HIV-positive women than in HIV-negative women (7.7% vs. 4.9%; P=.02), but the association was lost after adjustment for HPV 16 cervicovaginal infection. IgA, but not IgG, seropositivity was associated with progression to high-grade cytological abnormalities (relative hazard [RH], 2.2 [95% confidence interval, 1.2-4.2]), raising the possibility that an IgA response to HPV 16, as described for other DNA viruses, may be a marker of persistent viral replication. The risk of incident infection with non-16-related HPV types was increased in IgA seropositive women (RH, 1.8 [95% confidence interval, 1.3-2.6]), compared with seronegative women (RH, 2.2 [95% confidence interval, 0.9-5.4]), but there was no difference in the risk of incident HPV 16 or HPV 16-related infections. This may be evidence of partial type-specific or clade-specific immunity conferred by seropositivity to HPV 16 capsids.

Serological cross-reactivities between antibodies to simian virus 40, BK virus, and JC virus assessed by virus-like-particle-based enzyme immunoassays.

Enzyme immunoassays (EIAs) for detection of serum antibodies to simian virus 40 (SV40), BK virus (BKV), and JC virus (JCV) were developed by using virus-like-particles (VLPs) produced in insect cells from recombinant baculoviruses expressing the VP1 protein of the respective virus. Rhesus macaque sera with neutralizing antibodies to SV40 showed a high level of reactivity in the SV40 VLP-based EIA, and these sera also showed lower levels of reactivity in the BKV and JCV VLP-based EIAs. Rhesus macaque sera negative for neutralizing antibodies to SV40 were negative in all three EIAs. Competitive binding assays showed that SV40 VLPs inhibited BKV reactivity. In rhesus macaque sera, high optical density (OD) values for antibodies to SV40 VLPs were correlated with high OD values for antibodies to BKV but not with high OD values for antibodies to JCV VLPs. Human sera with neutralizing antibodies to SV40 were more reactive to SV40 VLPs than human sera without neutralizing antibodies to SV40. The greater SV40 reactivities of human sera were correlated with greater reactivities to BKV VLPs but not JCV VLPs. These data suggest that cross-reactivity with BKV antibodies may account for part of the low-level SV40 reactivity seen in human sera. With their greater versatility and their suitability for large-scale testing, the VLP-based EIAs for SV40, BKV, and JCV are likely to contribute to a better understanding of the biology of these viruses.

Serum immunoglobulin G response to human papillomavirus type 16 virus-like particles in human immunodeficiency virus (HIV)-positive and risk-matched HIV-negative women.

Baseline serum samples from 2815 human immunodeficiency virus (HIV)-positive and 963 HIV-negative women enrolled in 2 cohort studies were tested for immunoglobulin G antibodies to human papillomavirus type 16 (HPV-16) capsids. HPV-16 seropositivity was associated with lifetime number of sex partners (P<.001) among both HIV-positive and HIV-negative women. Approximately 50%-60% of HPV-16 DNA-positive women were HPV-16 positive. HPV-16 seropositivity was associated with HIV infection; however, after adjustment for baseline cervical HPV infection and disease, the association disappeared. Thus, the high seroprevalence of HPV-16 among HIV-positive women may be explained by a high prevalence of HPV of all types. Approximately 50% of HIV-positive women had serological evidence of prior HPV-16 infection, but only approximately 5% had an HPV-16 cervical infection at baseline. Despite the higher prevalence of HPV infection in this group, most HIV-positive women are able to control HPV-16 replication at the cervix, and reactivation, if it occurs, is not very common.