Glycoproteins E2 of the Venezuelan and Eastern equine encephalomyelitis viruses contain multiple cross-reactive epitopes

Abstract

Enzyme immunoassay (EIA) with sixty types of monoclonal antibodies (MAbs) was used to study cross-reactive epitopes on the attenuated and virulent strains of the Eastern equine encephalomyelitis (EEE) and Venezuelan equine encephalomyelitis (VEE) viruses. All three structural proteins of the EEE and VEE viruses were demonstrated to have both cross-reactive and specific antigenic determinants. The glycoprotein E1 of EEE and VEE viruses possesses three cross-reactive epitopes for binding to MAbs. The glycoprotein E2 has a cluster of epitopes for 20 cross-reacting MAbs produced to EEE and VEE viruses. Cross-reactive epitopes were localised within five different sites of glycoprotein E2 of VEE virus and within four sites of that of the EEE virus. There are no cross-neutralising MAbs to the VEE and EEE viruses. Only one type of the protective Mabs was able to cross-protect mice against lethal infection by the virulent strains of the VEE and EEE viruses. Eight MAbs blocked the hemagglutination activity (HA) of both viruses. Antigenic alterations of neutralising and protective sites were revealed for all attenuated strains of the VEE and EEE viruses. Comparative studies of the E2 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 MAbs 7D1, 2D4 and 7A6 have mutations of the E2 protein at positions 59, 212-213 and 232, respectively. Amino acid sequences in these regions of the VEE and EEE viruses are not homologous. These observations indicate that cross-reactive MAbs are capable of recognising discontinuous epitopes on the E2 glycoprotein.

Protective antibodies against Eastern equine encephalitis virus bind to epitopes in domains A and B of the E2 glycoprotein

“…Although prior studies have generated mAbs against the EEEV proteins, these mAbs either lacked neutralization activity or were not characterized extensively due to biosafety limitations 14–17 . One cross-reactive, non-neutralizing anti-EEEV mAb that was evaluated had moderate protective efficacy (~50%) against VEEV challenge in mice 17 .…”

“…Few anti-EEEV monoclonal antibodies (mAbs) have been described 14–16 and only one has protective activity in mice 17 . These anti-EEEV mAbs have been mapped using peptides to three linear epitopes on E2: the N-terminus of domain A, the N- and C-terminal arches of domain B, and the C terminus of domain C 14,15 .…”

The Structure of Barmah Forest Virus as Revealed by Cryo-Electron Microscopy at a 6-Angstrom Resolution Has Detailed Transmembrane Protein Architecture and Interactions

“…The sequence alignment of BFV with other alphaviruses shows amino acid identities of less than 59% in E1 and less than 45% in E2. The analyses of Venezuelan equine encephalitis virus (VEEV) (14,25), SINV (33), and RRV (37) neutralization escape mutants suggest that neutralizing epitopes cluster at E2 domain B (equivalent to residues 169 to 250 of BFV). Sequence comparison of SINV, RRV, and VEE to BFV shows a lower level of similarity (23 to 30%) in domain B compared to that in the rest of the E2 molecule.…”

Comprehensive Mapping of Common Immunodominant Epitopes in the Eastern Equine Encephalitis Virus E2 Protein Recognized by Avian Antibody Responses

“…Identification of E2 protein-specific antibody epitopes will further contribute to the development of diagnostic tests based on EEEV E2 protein antigenicity. Most information regarding antibody recognition of EEEV E2 stems from studies of the murine immune response [26], and there have been no reports describing E2 epitopes recognized by antibodies generated in avian species. In this study, we characterized the E2 protein epitopes recognized by the avian antibody response, and defined the common immunodominant E2 epitopes that were targeted by antibodies in chickens and ducks.…”