GLYCOPROTEINS E2 OF THE VENEZUELAN AND EASTERN EQUINE ENCEPHALOMYELITIS VIRUSES CONTAIN MULTIPLE CROSS-REACTIVE EPITOPES

Enzyme immunoassay (EIA) with sixty types of monoclonal antibodies (MA bs) was used to study cross-reactive epitopes on the attenuated and vi rulent strains of the Eastern equine encephalomyelitis (EEE) and Venez uelan equine encephalomyelitis (VEE) viruses. All three structural pro teins of the EEE and VEE viruses were demonstrated to have both cross- reactive and specific antigenic determinants. The glycoprotein E1 of E EE and VEE viruses possesses three cross-reactive epitopes for binding to MAbs. The glycoprotein E2 has a cluster of epitopes for 20 cross-r eacting MAbs produced to EEE and VEE viruses. Cross-reactive epitopes were localised within five different sites of glycoprotein E2 of VEE v irus and within four sites of that of the EEE virus. There are no cros s-neutralising MAbs to the VEE and EEE viruses. Only one type of the p rotective Mabs was able to cross-protect mice against lethal infection by the virulent strains of the VEE and EEE viruses. Eight MAbs blocke d the hemagglutination activity (HA) of both viruses. Antigenic altera tions of neutralising and protective sites were revealed for all atten uated strains of the VEE and EEE viruses. Comparative studies of the E 2 proteins amino acid sequences show that the antigenic modifications observed with the attenuated strains of the VEE virus may be caused by multiple amino acid changes in positions 7, 62, 120, 192 and 209-213. The escape-variants of the VEE virus obtained with cross-reactive MAb s 7D1, 2D4 and 7A6 have mutations of the E2 protein at positions 59, 2 12-213 and 232, respectively. Amino acid sequences in these regions of the VEE and EEE viruses are not homologous. These observations indica te that cross-reactive MAbs are capable of recognising discontinuous e pitopes on the E2 glycoprotein.