Recombinant HIV-1 glycoprotein 120 induces distinct types of delayed hypersensitivity in persons with or without pre-existing immunologic memory

Induction of T cell help is critical in HIV-1 control and potentially in pr evention by immunization. A practical approach is needed to identify HIV-1- specific helper activities in vivo, We explored the feasibility of measurin g delayed-type hypersensitivity (DTH) following intradermal injection of re combinant soluble HIV-1,, glycoprotein 120 in HIV-1-infected, vaccinated, a nd exposed individuals. DTH reactions were elicited within 48 h in 16 of 29 untreated, infected patients and in 24 of 30 uninfected vaccinees, Concomi tant envelope-specific lymphoproliferation in vitro was undetectable among 9 infected patients tested with positive envelope-specific DTH, By contrast , no 48-h DTH reactions occurred among 25 high risk and 32 low risk, uninfe cted volunteers. However, 7-12 days after injection, 10 (40%) high risk and 11 (34%) low risk individuals developed induration resembling DTH, and the cellular infiltrates contained monocytes and T cells. Ave of 18 examined a lso developed anti-gp120 Abs. The very delayed time course and lack of corr elation with previous Ag exposure clearly distinguish this reaction from DT H. Thus, HIV-I skin testing can identify persons with HIV-specific recall r esponses resulting from infection, in the absence of in vitro lymphoprolife ration, and from vaccination In contrast, very late reactivities may signif y chemotactic properties of the envelope protein and/or herald the inductio n of primary HIV-specific Th1-type immunity.