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Vaccine Induced Enhancement of Equine Infectious Anemia Virus (EIAV) Replication and Disease.

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Final rept. 15 Jul 94-14 Jan 97,

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We have used the equine infectious anemia virus EIAV-Shetland pony system to examine the antigenic determinants, mechanisms, and in vitro serological correlates of vaccine enhancement of virus replication and disease, as an animal model for human AIDS vaccine studies. The results of these studies demonstrated that the propensity for vaccine enhancement depended on the nature of the envelope subunit immunogen, the antigenic relatedness of the vaccine and challenge strain, and individual differences in a typical outbred population of ponies. The current studies combined with previous vaccine trials indicated that vaccine enhancement was a practical problem with all of the experimental envelope subunit vaccines in challenges with heterologous virus, even in cases where the particular vaccine provided apparently sterile protection against homologous virus challenge. Evaluations of various serological assays of immune serum from vaccinated ponies demonstrated that in vitro assays were unreliable and insensitive correlates for immune enhancement in vivo, although antibodies associated with protective and nonprotective immune responses could be differentiated by serological properties that reflect the maturity of antibody responses to viral envelope proteins. Thus, these observations made in the EIAV system indicate a continued necessity to consider the potential for immune enhancement in the design of AIDS vaccine trials and to develop in vitro serological assays to monitor the maturation of antibody responses to candidate vaccines.

Subject Categories:

  • Medicine and Medical Research
  • Microbiology
  • Pharmacology

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