Follow-up of HIV Infected Patients Who Received a Therapeutic Anti-Tat Vaccination

Basic and epidemiological documentation as well as non human primate experimentation prompted us to develop anti Tat therapeutic vaccine based on Tat toxoid, a non toxic but immunogenic HIV-1 Tat derivative. Phase I trial conducted at the Hemophiliac Bonomi Center of Milan (Pr. Gringeri) in 1997–1998 and Phase I/II trial organized by Aventis Pasteur showed that the Tat toxoid immunogen adjuvanted with either Seppic oil (ISA51), DcChol or Alum was safe and immunogenic on patients under HAART or not. A structured treatment interruption study (STI) monitored according to EU guidelines was conducted at Brussels (Pr. Clumeck) on the 31 vaccinees who received either a DcChol adjuvanted Tat Toxoid (n = 12), a DcChol placebo (n = 8) or non adjuvanted Tat Toxoid (n = 11). Anti-Tat Ab responders (n = 9) exhibiting both high serum Ab titers (>10 pg/ml) and a serum anti-Tat neutralizing capacity at the end of the vaccine trial remained significantly HAART-free. By contrast in patients in whom HAART has been prescribed during STI, serum collected prior to treatment did not exercise anti-Tat neutralizing capacity.