Enhancement of HIV type 1 infectivity in vitro by capsular polysaccharide of Cryptococcus neoformans and Haemophilus influenzae.

High concentrations of the cryptococcal capsular polysaccharide (CCP) are present in the serum, cerebrospinal fluid or both in the majority of AIDS patients infected with Cryptococcus neoformans. Because the prognosis of AIDS patients infected with cryptococcus is poor, we investigated whether the presence of CCP enhanced HIV-1 infection. The presence of CCP markedly increased the infectivity of HIV-1-infected H9 cells and subsequent production of infectious HIV-1 and formation of syncytia. In addition to enhancing the infectivity of H9 cells infected with laboratory isolates of HIV-1, the presence of CCP also increased the infectivity of peripheral blood mononuclear cells (PBMCs) infected with primary field strains of HIV-1. The in vitro infectivity of PBMCs from 20 of 44 HIV-1-infected individuals was significantly increased when cultured with CCP. Furthermore, HIV-1 was isolated from the PBMCs of three of these individuals only when cultured in the presence of CCP. CCP increased the binding of HIV-1 and recombinant gp120 to H9 cells and recombinant CD4, respectively. Thus, it is possible that the enhancement of HIV-1 infectivity by CCP is due to its capacity to increase the adherence of HIV-1 to target cells. Whereas the capsular polysaccharide of Haemophilus influenzae also markedly enhanced the infectivity of HIV-1, the capsular polysaccharides of C. freundii or S. flexneri had minimal effects on the infectivity of HIV-1. This indicated that the capacity to enhance HIV-1 infectivity was a property of polysaccharides from some pathogens and not others.(ABSTRACT TRUNCATED AT 250 WORDS)