Antigenic and Molecular Evolution of the Vaccine Strain of Type 3 Poliovirus during the Period of Excretion by a Primary Vaccinee

TLDR

A 4‑month‑old child received the Sabin live‑attenuated trivalent poliovirus vaccine, and the antigenic and molecular evolution of the type 3 strain was tracked throughout the entire excretion period. Novel type 3 strains emerged at 8, 42, and 52 days post‑vaccination through intertypic recombination with type 2 and point mutations, excretion persisted for 73 days, and all strains retained the main antigenic site while showing variation at immunorecessive sites, underscoring potential evolutionary implications consistent with known antigenic stability.

Abstract

A 4 month old child was immunized with a vaccine containing the Sabin live attenuated vaccine strains of all three serotypes of poliovirus. The antigenic and molecular evolution of the Sabin strain of poliovirus type 3 was then followed throughout the entire period of virus excretion. Novel strains appeared at 8, 42 and 52 days post-vaccination and were the products of both intertypic recombination between type 2 and type 3 poliovirus in regions of the genome coding for non-structural proteins and of point mutations in the region coding for the structural proteins. Excretion of virus continued for 73 days. All strains examined reacted with all monoclonal antibodies specific for the main immunodominant antigenic site of type 3 poliovirus, but variation was observed at other, immunorecessive sites. These findings have possible implications for the evolution of the virus in vaccinees or in epidemics and are consistent with the known antigenic stability of the virus.