Differential susceptibility of quiescent CD4(+) lymphocytes to syncytial-inducing and non-syncytial-inducing isolates of HIV-1

It is generally believed that quiescent CD4(+) T cells are not susceptible to HIV-1 infection. However, infection of unstimulated peripheral mononucle ar cells by syncytial-inducing (SI) viruses has been shown to be much more efficient than with non-syncytial-inducing (NSI) viruses. This suggested th at SI, CXCR4-tropic viruses may be able to infect quiescent CD4(+) T cells. We studied the infection of highly purified quiescent CD4(+) T cells by SI and NSI viruses. In this article we show that although NSI viruses failed to significantly infect quiescent cells, SI viruses consistently infected t hese cells and produced viruses upon cellular activation by interleukin-2, 2 to 7 days after initial infection. To examine whether the difference was the result of viral or host factors, we purified CCR5(+) quiescent CD4(+) T cells and showed that these cells can be infected by dual tropic (R5X4) bu t not by R5 virus This indicated that CCR5(+) quiescent T cells were also s usceptible to HIV-1 infection, and the failure of NSI, CCR5-tropic viruses to infect quiescent cells may be due to some intrinsic properties of these viruses. (C) 2001 The Japanese Society of Hematology.