Multiplication of Machupo Virus, the Etiological Agent of Bolivian Hemorrhagic Fever, in Cell Cultures

Multiplication of Machupo virus, the etiological agent of Bolivian hemorrhagic fever, was studied in a variety of cell cultures. One line of African green monkey kidney cells (Vero) supported the multiplication of the virus to high titer, but developed no cytopathic effect. Machupo virus produced well-defined plaques in monolayer cultures of Vero cells under agar overlay. The plaques produced in Vero cells were better defined and clearer than those produced in continuous newborn rabbit kidney (MA-111) cells, and the pfu titers obtained in Vero cells were higher than those obtained in MA-111 cells. A linear relationship was observed between plaque counts and virus concentration. Maximum adsorption was obtained by 120-min incubation at 37 °. When the cultures were infected with 0.003 pfu per cell, the maximum virus titer was obtained on day 5 after inoculation. Neutralization tests employing 80% plaque reduction were readily performed and indicated the absence of antibody for Machupo virus in the Junin and Tacaribe antisera that were tested. Neutralizing antibody response with human sera indicated the same.