Populations of infectious virus produced during avian adenovirus-associated virus infection

Multiple rounds of infection in vitro or in vivo with avian adenovirus-associated virus (AvA-AV) and avian adenovirus (AvAV) result in production of both heavy (H) and light (L) infectious forms. In this study, the infectious AvA-AV progeny produced at different hours during recombined dual infection of cells with either H or L AvA-AV and AvAV was determined by equilibrium CSCl centrifugation and infectivity assay. In both types of infection, H virions were found early, both intra- and extracellularly, whereas L virions were found late. The data iondicate an H to L particle density shift during infection. Virus-specified cell-dependent factors mediated the process extracellularly, as activity was detected in infected cell-conditioned medium and in lysates of infected cells but not in medium or components of uninfected cells. The shift in density was accompanied by a conversion in particle type. H and L virions differed in size and conformation as evidenced by differences in serological cross-reactivity and physical-chemical stability during heat inactivation, ultrasonic disruption and DNA extraction.