Attenuated HIV Vaccines

After 14 to 18 years of infection, half of the survivingpatients in an Australian cohort infected withHIV-1 carrying natural deletions in Nef are showingCD4 cell decline and viral load rise (Learmont et al.NEJM 1999;340:1715-22). Thus, although highlyattenuated, Nef-deleted or-mutated viruses are unsuitableas vaccine strains. Johnson et al. (J Virol1999;73:4952) showed that the degree of protectionby even further attenuated SIV strains, carryingdeletions in Nef, Vpr, Vpx and/or the U3 (LTR) region,against challenge with intact SIV was inverselyrelated to the extend of attenuation. Animals infectedwith virus carrying deletions in Nef, U3 andVpr were all protected against superinfection.