Genetic evidence for the origins of Venezuelan equine encephalitis virus subtype IAB outbreaks

Scott C. Weaver, Martin Pfeffer, Kathleen Marriott, Wenli Kang, Richard M. Kinney

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

Epizootics of Venezuelan equine encephalitis (VEE) involving subtype IAB viruses occurred sporadically in South, Central and North America from 1938 to 1973. Incompletely inactivated vaccines have long been suspected as a source of the later epizootics. We tested this hypothesis by sequencing the PE2 glycoprotein precursor (1,677 nucleotides) or 26S/nonstructural protein 4 (nsP4) genome regions (4,490 nucleotides) for isolates representing most major outbreaks. Two distinct IAB genotypes were identified: 1) 1940s Peruvian strains and 2) 1938-1973 isolates from South, Central, and North America. Nucleotide sequences of these two genotypes differed by 1.1%, while the latter group showed only 0.6% sequence diversity. Early VEE virus IAB strains that were used for inactivated vaccine preparation had sequences identical to those predicted by phylogenetic analyses to be ancestors of the 1960s-1970s outbreaks. These data support the hypothesis of a vaccine origin for many VEE outbreaks. However, continuous, cryptic circulation of IAB viruses cannot be ruled out as a source of epizootic emergence.

Original languageEnglish (US)
Pages (from-to)441-448
Number of pages8
JournalAmerican Journal of Tropical Medicine and Hygiene
Volume60
Issue number3
DOIs
StatePublished - Mar 1999

ASJC Scopus subject areas

  • Parasitology
  • Virology
  • Infectious Diseases

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