ITIH4 and infection: 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.