Serological evidence of an early seroconversion to Simian virus 40 in healthy children and adolescents

Abstract

At present Simian virus 40 (SV40) infection in humans appears to be transmitted independently from early contaminated vaccines. In order to test the spread of SV40 infection in children, an immunologic assay employing specific SV40 synthetic peptides corresponding to its viral protein (VP) antigens was employed to estimate the seroprevalence of this polyomavirus in Italian infants and adolescents. Serum samples from 328 children and adolescents, up to 17 years, were investigated. Serum antibodies against SV40 VPs were detected by indirect enzyme-linked immunosorbent assays. The seroprevalence of this polyomavirus was calculated after stratifying the subjects by age. Anti-viral capsid protein 1-2-3 SV40 IgG antibodies were detected in 16% of the study participants. The prevalence of antibodies against SV40 VPs tended to increase with age in children, up to 10 year old (21%). Then, in the cohort of individuals aged 11-17 years, the prevalence decreased (16%). A higher prevalence rate (23%) of SV40 VP antibodies was detected in the cohorts of 1-3 year and 7-10 year old children, than in children and adolescents of the other age groups. This age corresponds to children starting nursery and primary school, respectively, in Italy. IgM antibodies against SV40 VP mimotopes were detected in 6-8 month old children suggesting that SV40 seroconversion can occur early in life. SV40 VP antibodies are present at low prevalence in Italian children (16%), suggesting that SV40 infection, although acquired early in life, probably through different routes, is not widespread. The low SV40 seroprevalence suggests that SV40 is less transmissible than other common polyomaviruses, such as BKV and JCV. Alternatively, our immunologic data could be due to another, as yet undiscovered, human polyomavirus closely related to SV40.

Figure 1. Comparison of SV40 age-specific seroprevalence of antibodies.

Comparison of SV40 age-specific seroprevalence of antibodies among 214 Italian children and adolescents, <1–17 year old (this study), Panel A; compared to 288 Swedish children aged between 1 and 13 year old Panel B; and compared to 629 U.S. children and adolescents aged between 1 and 18 year old , Panel C.

Figure 2. Serologic profile of serum antibody reactivity to SV40 mimotopes, VP1 B (Panel A), VP2/3 C (Panel B) and VPs both peptides B–C (Panel C).

Data are presented as values of VPs B and C, OD readings at λ 405 nm, of serum samples diluted at 1∶20 detected in indirect ELISA testing. In scatter dot plotting, each plot represents the dispersion of OD values to a mean level, indicated by the line inside the scatter with standard error of the mean (SEM) for each age group of subjects analyzed. The OD readings of serum samples stratified by age of children were: 0.1–4 months, 4.1–12 months, 1.1–3 ys, 3.1–6 ys, 7–10 ys and 11–17 ys. Data were analyzed with one way Anova analysis, and Newman-Keuls Multiple Comparison Test (OD mean, 95% CI). Panel A. High levels of antibodies against SV40 VP1 B, mean OD values, were observed in children aged 11–17 ys (0.48 OD, 95% CI = 0.34–0.62) vs. children aged 0.1–4 months (0.13 OD, 95% CI = 0.10–0.17) (P<0.001) and vs. children aged 4.1–12 months (0.25 OD, CI = 0.18–0.32), with P<0.05. Panel B. The different levels of antibodies against SV40VP1 peptide C, mean OD values, were not statistically significant among children. Panel C. High levels of antibodies against SV40VPs, both peptides B and C, mean OD values, were observed in children aged 1.1–3 ys (0.33 OD, CI = 0.25–0.41), and 3.1–6 ys (0.28 OD, CI = 0.22–0.35) vs. children aged 0.1–4 months (0.16 OD, CI = 0.11–0.20), with *P<0.05. Highest level of mean OD values were observed in children aged 7–10 ys (0.35 OD, CI = 0.28–0.41) and 11–17 ys (0.36 OD, CI = 0.28–0.44) vs. children aged 0.1–4 months., with **P<0.001.