Radioimmune precipitation of group A arboviruses.

A radioimmune precipitation (RIP) test was used to study selected group A arboviruses. Purified preparations of Sindbis (SIN), western equine encephalitis (WEE) and eastern equine encephalitis (EEE) virus were examined in homologous and heterologous reactions. RIP reactions were comparable to plaque reduction neutralization tests in both sensitivity and specificity. When SIN virus was precipitated by WEE virus antiserum, the RIP curve was biphasic. RIP inhibition of the homologous and biphasic heterologous reaction suggested three separate antibody populations of differing specificities. The results indicated that WEE virus antiserum contained: a) a high titered specific antibody, b) a broadly crossreactive antibody at intermediate antiserum dilutions and c) a low titered antibody which detected only the intra-group WEE-SIN virus complex.