A PILOT PHASE-II STUDY OF THE SAFETY AND IMMUNOGENICITY OF HIV P17 P24-VLP (P24-VLP) IN ASYMPTOMATIC HIV-SEROPOSITIVE SUBJECTS/

The aim of this phase II study was to evaluate the safety, immunogenic ity and tolerability of the yeast-derived viruslike particle immunogen , Ty.p24.VLP (p24-VLP), in HIV-antibody-positive asymptomatic voluntee rs, Fifteen informed and consented volunteers, with p24 Antibody titre s >1/100, p24 Antigen <20 pg/l, and CD4>350 x 10(9)/l were enrolled, F ive were immunized with aluminium hydroxide placebo, five with 25 mu g , and five with 100 mu g p24-VLP in Alum adjuvant at weeks 0 and 4 by the intramuscular route, Patients were followed for 16 weeks post vacc ination and the main outcome assessments were CD4 and CD8 lymphocyte c ounts, p24 antigen and antibody, Ty antibody and quantitative viral cu ltures. No serious adverse events were observed in any of the groups, There were increases in CD4 counts in the treated groups but not in th e controls, although these changes were not statistically significant, There were no significant intrasubject or intergroup changes in the o ther parameters, such as p24 antigen and antibody. No pattern of chang e in plasma viraemia was detected, and most cultures were negative. Th erefore we conclude that p24-VLP immunizations of 25 mu g and 100 mu g are well tolerated, and the CD4 changes are encouraging, but higher d oses and larger numbers are required to see if there are significant h umoral or cellular responses, and extended phase II studies are now in progress.