Expression of the novel T cell activation molecule hpH4 in HIV-infected patients: Correlation with disease status

We have described hpH4, a surface glycoprotein selectively expressed by act ivated T cells and mature thymocytes and displaying weak lateral associatio n with CD4. The hpH4 expression pattern and biochemical features, together with analysis of its tryptic digest by peptide mass searching using MALDI-M S, suggested that it is a novel molecule. The aim of this work was to evalu ate the peripheral blood T cell expression of hpH3 in HIV-infected patients and the interplay between HIV gp120 and hpH4, since both molecules interac t with CD4, hpH4 expression during HTV-1 infection was evaluated by assessi ng 55 patients at various disease stages and following up 3 patients with p rimary infection and 3 patients with AIDS. hpH4 expression displayed a peak in the early phase of primary infection, dropped to control levels in the asymptomatic phase, and was newly expressed, at low levels, as AIDS develop ed. The expression kinetics were different than those shown by HLA-DR, CD25 , and CD38, The most striking findings were the transient hpH4 expression p eak displayed in the earliest stage, which was unique for hpH3. Incubation of T cells from normal donors with HIV gp120 induced transient hpH4 express ion in resting CD4(+) T cells and potentiated the hpH4 lateral association with CD4 in activated T cells. Moreover, hpH4 triggering inhibited gp120-in duced death of CD4(+) cells. Therefore, H4 expression may be a response to avoid apoptosis induced by HIV products.