Population dynamics and in vitro antibody pressure of porcine parvovirus indicate a decrease in variability

Abstract

To estimate the impact of porcine parvovirus (PPV) vaccines on the emergence of new phenotypes, the population dynamic history of the virus was calculated using the Bayesian Markov chain Monte Carlo method with a Bayesian skyline coalescent model. Additionally, an in vitro model was performed with consecutive passages of the 'Challenge' strain (a virulent field strain) and NADL2 strain (a vaccine strain) in a PK-15 cell line supplemented with polyclonal antibodies raised against the vaccine strain. A decrease in genetic diversity was observed in the presence of antibodies in vitro or after vaccination (as estimated by the in silico model). We hypothesized that the antibodies induced a selective pressure that may reduce the incidence of neutral selection, which should play a major role in the emergence of new mutations. In this scenario, vaccine failures and non-vaccinated populations (e.g. wild boars) may have an important impact in the emergence of new phenotypes.

Porcine Parvovirus

“…Furthermore, the occurrence and distribution of new antigenic types have to be watched very closely. It was observed that new mutations in the capsid protein can modify antigenic properties, and may reduce the cross neutralization ability of sera raised against strains commonly used in commercial vaccines (Zeeuw et al, 2007;Streck et al, 2013Streck et al, , 2015a. New vaccines that induce a long-lasting immunity and cover all the dominant virus strains circulating in pig populations are needed to overcome currently observed putative vaccination failures.…”

Biology of Porcine Parvovirus (Ungulate parvovirus 1)

“…Mutations found on immune selected capsids (NADL-2 I320S, H383Q; Str. Challenge S45T, P436S) were not present on novel variants either [ 45 ]. The authors concluded that vaccine failures and non-vaccinated animals (e.g., wild boars) may have a more important impact on the emergence of new phenotypes than vaccinated populations.…”

An inactivated whole-virus porcine parvovirus vaccine protects pigs against disease but does not prevent virus shedding even after homologous virus challenge

“…Recently, a population dynamic analysis showed that, despite the high evolutionary rate, only a few PPV strains (similar to strain 27a) have been predominant in Europe in recent years (Streck et al, 2013b). For this reason, it is hypothesized that new PPV strains may interfere with the efficacy of the currently used vaccines (Truyen & Streck, 2012).…”