PREVENTION OF TRANSMISSION OF SIMIAN IMMUNODEFICIENCY VIRUS FROM VACCINATED MACAQUES THAT DEVELOPED TRANSIENT VIRUS-INFECTION FOLLOWING CHALLENGE

Macaque immunization with a mixture of four SIV peptides from conserve d hydrophilic envelope regions has been shown to prevent virus persist ence following challenge with SIV(mne/E11s). Data shown here demonstra te that lymph node cells from all vaccinated monkeys and peripheral bl ood lymphocytes from one of the vaccinees were positive in a SIV-pol ' nested' polymerase chain reaction (PCR) amplification analysis. Howeve r, by 37 months after infection, all immunized monkeys were healthy wh ile two of three controls had died and the remaining animal was virus culture-positive and had declining CD4+ lymphocytes. Viable lymph node cells and peripheral lymphoid cells in blood were transferred from th e three immunized macaques to individual susceptible macaques. As a co ntrol for the transfer, one of the vaccine experiment controls that wa s actively producing virus in its peripheral blood was used. None of t he recipients of cells from the vaccinated macaques seroconverted and all were virus coculture- and PCR-negative 25 weeks post-transfer (p.t .). The recipient of cells from the control infected macaque became po sitive in these tests by 2- 3 weeks p. t. These results suggest thal, while peptide-vaccinated macaques permitted some level of SIV replicat ion following challenge, the vaccine prevented disease progression and virus transmission.