Molecular Size, pH, Temperature Stability, and Ontogeny of Inhibitor(s) of Infectious Pancreatic Necrosis Virus (IPNV) in Normal Rainbow Trout Serum

Abstract

In this study, we investigated the characteristics of inhibitor(s) of infectious pancreatic necrosis virus (IPNV) found in the serum of normal rainbow trout Oncorhynchus mykiss (RTS). The molecular size, stability to pH and temperature, and ontogeny of the inhibitor in trout were studied, and the effect of cations (Ca 2ϩ and Mg 2ϩ ) on the activity of the inhibitor was tested. The strongest inhibition of virus was obtained at approximately 150 kDa as measured by ultracentrifugation, sieve gel chromatography, and ultrafiltration. The inhibition decreased significantly when RTS was dialyzed or filtered in the absence of divalent cations, but replacement of at least one cation restored activity. Activity was stable at temperatures ranging from 30ЊC to 50ЊC, but 55ЊC completely destroyed the inhibitory capacity of RTS. The inhibitory activity of RTS was not reduced between pH 4 and 10 but was diminished below pH 4 and above pH 10; such activity was not abrogated by proteases. Additionally, pretreatment of RTS with the polysaccharide mannan significantly reduced inhibition. Thus, the serum inhibitor(s) had many characteristics of a lectin.To determine the ontogeny of inhibition, serum samples were taken from normal rainbow trout, beginning at 2 weeks posthatch; consistent inhibition was not obtained until the rainbow trout had reached the age of 23 weeks posthatch.

Salmonid alphavirus (SAV) and pancreas disease (PD) in Atlantic salmon, Salmo salar L., in freshwater and seawater sites in Norway from 2006 to 2008

“…One blood sample of 90 from one seawater site was found to neutralize SAV, while tissue samples failed to give a Ct value on real‐time RT‐PCR analysis, nor were any histopathological changes consistent with PD detected. The blood plasma from this single fish could have contained unspecific viral inhibitor(s) against SAV as has previously been shown to occur for infectious pancreatic necrosis virus (IPNV) (Park & Reno 2005). This is, however, assumed to be rare in salmonid blood, following a lack of such findings for other sites and absence of reports of this phenomenon from other serological studies of SAV (Graham et al.…”