Genetic and antigenic diversity among eastern equine encephalitis viruses from North, Central, and South America.

Abstract

Abstract. Eastern equine encephalitis virus (EEEV), the sole species in the EEE antigenic complex, is divided into North and South American antigenic varieties based on hemagglutination inhibition tests. Here we describe serologic and phylogenetic analyses of representatives of these varieties, spanning the entire temporal and geographic range available. Nucleotide sequencing and phylogenetic analyses revealed additional genetic diversity within the South American variety; 3 major South/Central American lineages were identified including one represented by a single isolate from eastern Brazil, and 2 lineages with more widespread distributions in Central and South America. All North American isolates comprised a single, highly conserved lineage with strains grouped by the time of isolation and to some extent by location. An EEEV strain isolated during a 1996 equine outbreak in Tamaulipas State, Mexico was closely related to recent Texas isolates, suggesting southward EEEV transportation beyond the presumed enzootic range. Plaque reduction neutralization tests with representatives from the 4 major lineages indicated that each represents a distinct antigenic subtype. A taxonomic revision of the EEE complex is proposed.Eastern equine encephalitis virus (EEEV) has been recognized as an important veterinary pathogen since the early nineteenth century, when the first clinical descriptions consistent with EEE were reported.

Chimeric Sindbis/eastern equine encephalitis vaccine candidates are highly attenuated and immunogenic in mice

“…Antibody responses to the vaccines appeared to be dose-dependent. Cross-neutralization titers between the 2 vaccines and their parent NA and SA EEEV strains generally differed by ≥ 4-fold, consistent with previous antigenic data indicating these 2 isolates represent EEEV subtypes [5]. However, despite the lower neutralization titers against the NA EEEV strain that were induced by the SIN/SAEEEV compared to the SIN/NAEEEV chimeric strain, the former exhibited complete protection against NA EEEV challenge, even at the lowest vaccination dose of (3.8 log 10 PFU per mouse).…”

“…Using antigenic and genetic analyses, EEEV virus has been classified into one North American (NA) and 3 South American (SA) subtypes [5]. The NA subtype consists of isolates from the Eastern equine encephalitis virus is a zoonotic, mosquito-borne virus that circulates among passerine birds in swamp habitats of NA.…”

Ecological studies of enzootic Venezuelan equine encephalitis in north-central Venezuela, 1997-1998.

“…The outgroup consisted of representative homologous sequences of four major lineages of EEE virus. 24 Nucleotide sequence accession numbers. The new VEE virus sequences were deposited in the GenBank library under accession numbers AF348335 and AF348336.…”

Molecular Epidemiology of Eastern Equine Encephalitis Virus, New York

“…The structural proteins are encoded in the 3′ third of the genome and are translated from a subgenomic RNA, 26S, resulting in 5 protein products: C, 6K, E1, E2, and E3 (2). Previous sequencing studies analyzed genetic relationships of EEEV strains in the Western Hemisphere and compared strains distributed across widespread geographic regions (3)(4)(5)(6). EEEV has 4 distinct genetic lineages; lineage I consists of highly conserved strains from North America, and lineages II-IV encompass strains from Central and South America (3).…”