Behavior of Machupo and Latino Viruses in Calomys callosus from Two Geographic Areas of Bolivia

Summary

Latino virus, a new member of the Tacaribe complex, was isolated from Calomys callosus, the rodent host of Machupo virus. Laboratory colonies of Calomys designated SJ (Machupo virus) and JL (Latino virus) were established with animals from their respective virus-specific areas of Bolivia. Newborn SJ animals gave a split response to infection with Latino virus; some had persistent viremia while others developed complement-fixing antibody and cleared virus from their blood. When these animals were super-infected with Machupo virus as adults, they evolved a similar pattern of split response unrelated to prior type of Latino virus infection.

Adult JL Calomys inoculated with Latino virus had immunofluorescent antibody, but no viremia or anemia 60 days later. Machupo virus-infected animals from this colony cleared virus from their blood more slowly and a few still were viremic and anemic 5 months after infection. Infection of suckling animals with Machupo virus resulted in uniform viremia among SJ rodents, whereas about half of the JL Calomys eventually were non-viremic. Latino virus was cleared from the blood by all JL Calomys after 4 months, but by only half of the SJ animals. Anemia was Machupo virus-specific rather than host-determined. Responses to both viruses in F₁ hybrid rodents inoculated as newborns were strongly related to origin of the male parent. The data indicate that factors specific to both virus and host influence the outcome of infection by related arenaviruses in a single rodent species. They also suggest that control of human disease caused by Machupo virus cannot be achieved by introduction of Latino virus or its geographic race of Calomys callosus.