Horses naturally infected with EIAV harbor 2 distinct SU populations but are monophyletic with respect to IN

Diana T. Cervantes, Judith M. Ball, John Edwards, Susan Payne

Research output: Contribution to journalArticlepeer-review


Equine infectious anemia virus (EIAV) causes lifelong infections ranging from acutely fatal, to chronic, to asymptomatic. Within infected animals, EIAV is found as a quasispecies. Many experimental studies on EIAV, carried out in the U.S. over the past 70 years, have used either the highly virulent Wyoming (EIAVwyo) field strain or various derivatives of that strain. These infections have provided insights into the variety of genetic changes that accumulate in the env gene and LTR in experimentally infected horses. In the current study, we obtained EIAV sequences from blood samples collected from naturally infected Texas horses between 2000 and 2002. We found surface (SU) and long terminal repeat (LTR) sequences clearly related to EIAVwyo and its cell culture-adapted derivatives. Some blood samples yielded SU or LTR sequences belonging to 2 discrete clusters. In these cases, SU and LTR variation between animals was no greater than sequence variation within animals. In contrast, a portion of integrase (IN) was more homogeneous within animals than between animals. These results suggest that specific selective pressures are applied to SU and LTR sequences, potentially driving generation of two distinct sequence clusters within a horse. We speculate that viruses in one cluster may be more highly expressed and easily transmitted while those in the second cluster support long-term inapparent infection. The presence of homogeneous IN sequences within a horse supports the hypothesis that SU and LTR sequences diverged after the initial infection.

Original languageEnglish
Pages (from-to)71-80
Number of pages10
JournalVirus Genes
Issue number1
StatePublished - 1 Feb 2016


  • EIAV
  • Equine infectious anemia virus
  • Horse
  • Lentivirus
  • Retrovirus
  • Swamp fever


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