Effect of threadfin aquareovirus recombinant proteins on the resistance of guppy (Peocilia reticulata) to guppy aquareovirus infection

Abstract

Two recombinant proteins obtained from the marine threadfin aquareovirus (TFV), representing the inner (rICP) (∼75 kDa) and outer (rOCP) (∼35 kDa) coat proteins of the virus were used to study their effects on the immunity of freshwater guppy (Poecilia reticulata), against guppy aquareovirus (GPV), a strain isolated from moribund guppy during a recent disease outbreak. Western blot analysis utilizing rabbit anti-GPV serum demonstrated that both the inner and outer coat proteins of the threadfin aquareovirus (TFV) share common epitopes with the native outer and inner viral coat proteins of guppy aquareovirus. The rabbit anti-GPV serum also exhibited neutralization activity against the guppy aquareovirus. Furthermore, both recombinant rICP and rOCP proteins could block GPV from infecting susceptible cultured cells. Hence, these two recombinant proteins were then assessed for their suitability as candidate vaccines against GPV in guppy through immersion and oral immunization. Immunization of guppy with recombinant rOCP and/or rICP resulted in the production of neutralizing substances. The neutralization titers of the tissue extracts obtained from guppy immunized orally or by immersion with either recombinant rOCP or rICP were lower (between 1:32 and 1:64) compared to those immunized with a combination of recombinant rOCP and rICP (1:1024). These results clearly indicated that the administration of a combination of recombinant rOCP and rICP for immunization is essential for the induction of high amounts of neutralization substances that prevents GPV infection in guppy. © 2004 Elsevier B.V. All rights reserved.