Properties and Characterization of Monoclonal Antibodies to Tacaribe Virus

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Abstract
Monoclonal antibodies prepared against Tacaribe and Junin viruses were used to define further the serological relationships between arenaviruses of the Tacaribe complex. A close relationship was found between these 2 viruses and the heterologous Amapari and Machupo viruses, with Pichinde and Parana viruses being more distantly related. Among the antibodies specific For Tacribe virus, 5 reacted with viral antigens at the surface of infected cells and neutralized virus infectivity in vitro. These 5 antibodies were differentiated by competitive immunoassay as recognizing at least 2 antigenically distinct epitopes. The kinetics of reaction between antibody and virus were examined for all 5 neutralizing antibodies. One antibody (2.25.4) effectively neutralized all infectious virus. The remaining 4 directed against a 2nd epitope gave significant persistent fractions which were reduced by addition of complement, anti-mouse Ig or antibody 2.25.4. Variants of Tacribe virus resistant to neutralization by antibody 2.25.4 were obtained by growth in the presence of this antibody and neutralization kinetics were reexamined using the heterologous monoclonal neutralizing antibodies. Several different neutralization profiles were obtained, suggesting that point mutations resulted in conformational change at topographically selected distinct epitopes recognized by the remaining antibodies.