AEGiS-13IAC: HIV-1 Vaccine trial in Uganda: Experience on pre- and post-vaccination screening of volunteers.

13th International AIDS Conference

Durban, South Africa - July 9-July 14, 2000

HIV-1 Vaccine trial in Uganda: Experience on pre- and post-vaccination screening of volunteers.

Int Conf AIDS 2000 Jul 9-14; 13:(abstract no. WeOrC557)

Serwanga J, Kaleebu P, Mugerwa R, Mugyenyi P, Mbidde E, Andersson K, Flores J, Ellner J, Hom DL
J. Serwanga, Uganda virus research institute, P.O. BOX 49, Entebbe, Uganda, Tel.: +256 41 320 385, Fax: +256 41 321 137, E-mail: arbovir@infocom.co.ug

BACKGROUND: Uganda initiated a phase I placebo-controlled, double-blind, randomized HIV-1 preventive vaccine trial in early 1999. Forty healthy low risk volunteers were randomized to receive recombinant ALVAC vCP205 HIV vaccine (n = 20), or 1 of 2 placebos. We present issues related to pre- and post-vaccination screening.

OBJECTIVES: 1) To establish criteria for pre-screening of volunteers; 2) to design an algorithm to differentiate vaccine-related immune responses from natural infection.

METHODS: Prior to recruitment, screening was done using two EIAs, Cambridge EIA and Welcozyme EIA and a Western blot (WB) (Cambridge Biotech). Those with indeterminate WB a second test was carried out on earlier stored (3 months) sera, in addition p24 gag or pol DNA PCR was performed. To differentiate vaccinees from natural HIV infection an algorithm that initially uses peptide based ELISAs that lack a portion of gp41 present in the vaccine construct i.e the Sanofi (Genetic Systems Corp) and Select-HIV (Biochem Corp) was used. If positive or discordant, WB, DNA PCR (p24 gag) and viral load (Roche, Amplicor 1.5) were performed to confirm infection. In addition viral typing by HMA or sequencing, and viral culture on a second sample were performed.

RESULTS: At screening all 40 volunteers were HIV negative.One individual became naturally infected during the trial. This subject was positive on both the Sanofi and Select EIA kits, was DNA PCR positive, and had a plasma viral load 18,000 copies/ml., with viral culture and viral typing underway to confirm acute HIV infection.

CONCLUSION: HIV diagnostic tests must be carefully selected for volunteer screening and differentiating vaccine-related immune responses from natural infection. The algorithm we instituted is adequate but labour intensive and expensive. Alternative simple algorithms need to be developed and validated before large efficacy trials.

Keywords: AEGIS, AIDS Vaccines, Vaccination, HIV-1, HIV Infections, Viral Load, Blotting, Western, CD4 Lymphocyte Count, Mass Screening, HIV Seropositivity, Immunoenzyme Techniques, Polymerase Chain Reaction, Uganda, Diagnosis
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