Response of cells persistently infected with arenaviruses to superinfection with homotypic and heterotypic viruses

Vero cell cultures persistently infected with the arenaviruses Junin, Pichinde, Tacaribe, and Tamiami were established and designated Vero-Jun, Vero-Pic, Vero-Tac, and Vero-Tam, respectively. Two types of carrier cultures could be easily distinguished: Vero-Jun and Vero-Tac systems were characterized by a lack of infectious virus production after a few cell transfers, whereas a more productive state with continuous release of virus was observed in Vero-Pic and Vero-Tam cultures. These differences appeared to be related to resistance of the culture to viral superinfection. In fact, Vero-Jun and Vero-Tac cultures totally excluded only the replication of the serologically more closely related arenaviruses Amapari, Junin, or Tacaribe, while the refractoriness of Vero-Pic and Vero-Tam cultures was extended to most of the virus group members. The resistance of Vero-Jun cells to superinfection by Junin or Tacaribe virus could be ascribed to the production of specific uv-resistant Junin interfering particles, which showed a specific range of interference against Junin and Tacaribe viruses. Interfering particles against homotypic and heterotypic arenaviruses were isolated from Vero-Pic cultures. However, the degree of interference developed by these Pic-interfering particles was not enough to fully explain reinfecting virus exclusion from Vero-Pic cultures. Viral susceptibility of persistent cultures is proposed as a useful tool to examine relationships of members of the arenavirus group.