Eastern Equine Encephalitis Virus Exhibits More Charged Amino Acids in Its Envelope Proteins, Compared to Madariaga Virus

Given the importance of eastern equine encephalitis virus (EEEV; complex lineage I) in veterinary and public health in North America, there is limited knowledge about lineages II, III, and IV, also known as Madariaga virus (MADV), which are prevalent in Central and South America. Because charge mutations in the envelope glycoproteins are critical to the emergence of Venezuelan equine encephalitis virus, we analyzed the structural polyproteins of Venezuelan MADV isolates and compared them with sequences of EEEV. Four substitutions involving positively charged residues were identified in the E3 (R44Q) and E2 (R205H/Q, K260T/A, and R310Q) proteins. Additionally, histidine residues were present in EEEV and absent in MADV: E2 (H82Y, H94Y, H114Q, and H181S) and E1 (H118Q). None of these amino acids were predicted to be under selective pressure or associated with a significant conformational change in the envelope proteins. However, some of these substitutions might still be associated with the virulence and pathogenicity of EEEV.