SEMIPERMISSIVE REPLICATION AND FUNCTIONAL-ASPECTS OF THE IMMUNE-RESPONSE IN A COTTON RAT MODEL OF HUMAN PARAINFLUENZA VIRUS TYPE-3 INFECTION

A cotton rat (Sigmodon fulviventer) model of human parainfluenza virus type 3 (HPIV-3) infection was used to study patterns of HPIV-3 replic ation in naive and immune hosts, Growth curves revealed that nasal and pulmonary tissues of naive animals were semi-permissive for virus rep lication, with amounts of progeny virus proportional to inoculating do ses. In naive animals there was a total eclipse in nasal tissues begin ning 4 h after inoculation. By contrast, there was only partial eclips e of virus in pulmonary tissues, most pronounced at 1 h after inoculat ion. Immune animals demonstrated a delayed eclipse in pulmonary tissue s upon rechallenge. Infection with very low doses of HPIV-3 induced co mplete protection against high-dose challenge in the absence of system ic neutralizing antibody, suggesting a significant role for other syst emic or local immune effectors.