Because 12% HIV infectivity of HeLa-CD4 occurs through the binding of gp120 to CD4 molecules on the cell surface of HeLa-CD4 cells, we would expect that infection of LNCaP by HIV Env(-) virus would occur through binding of unknown proteins of the virus and the cells, and the binding affinity should be comparable to that between gp120 and CD4 molecules. The gene discussed is CD4; the disease is infection.