Inhibition of cell fusion in Junin virus-infected cells by sera from Argentine hemorrhagic fever patients.

BACKGROUND

Junin virus (JV), a member of the Arenaviridae family, is the etiological agent of Argentine hemorrhagic fever (AHF). A low pH-pulse, induces fusion of Vero cells infected with JV to form syncytia, whose production can be inhibited by neutralizing antibodies against the JV major glycoprotein.

OBJECTIVES

To characterize the existence of an antifusogenic activity present in sera obtained from natural infections of AHF over a 20-year period and to study both the fusogenic activity of one pathogenic and two attenuated strains of JV in Vero cells, at different pH. The study sample consisted of sera obtained from two provinces in the Argentine Republic. Vero cells grown in monolayers, were infected with different strains of JV and a 2 h pulse, at different pH, was performed. Syncytium production was evaluated 12 h later, after staining with Giemsa. Neutralization tests against the attenuated strain XJCl3 were carried out and the antifusogenic activity of immunosera was studied by incubating serum with JV-infected Vero cells. Also the fusion activity in Vero cells infected with three JV strains was assayed.

RESULTS AND

CONCLUSIONS

A pathogenic strain XJ exhibited the highest fusogenic activity at pH 5. Syncytium formation was prevented by patients' sera obtained from different geographical locations, independently of time of infection. However, when Vero cells were infected with XJ, a significant reduction of syncytium production was observed, though the level of inhibition was lower than that detected in other JV strains-infected cells. These results could be explained by the existence of a conserved domain on JV proteins and also antigenic heterogeneity among strains.