Interactions of Junin and Tacaribe viruses during mixed infections

The interaction between Junin virus (JV) and Tacaribe virus (TACV) during mixed infections of RK13 cells was examined. The effects of a prior infection with JV upon TACV replication depended on the time between the two inoculations. Simultaneous infection of RK13 cells with TACV and JV did not alter the plaquing efficiency of TACV; but if there was a 1- to 24-hour delay between JV preinfection and TACV superinfection, a variable increase of TACV replication was observed. The enhancement of TACV replication by preinfection with JV was dependent on several factors, such as the MOI of both viruses and the integrity of the JV genome. This effect was also highly specific, as the plaquing efficiencies of the arenavirus Pichinde and the unrelated vesicular stomatitis virus were not affected by preinfection with JV at any multiplicity assayed. The majority of the progeny formed in cells superinfected with TACV 1 or 24 h after JV infection was partially neutralized by antisera to both viruses. This suggested that phenotypic mixing, with JV or TACV genomes enclosed within an envelope containing TACV and JV glycoprotein, had occurred.