Increased Expression of Toll-Like Receptor 2 on Monocytes in HIV Infection: Possible Roles in Inflammation and Viral Replication

Background. Toll-like receptors (TLRs) are key pattern-recognition receptors of the innate immune system, but their role in human immunodeficiency virus (HIV) infection is largely unknown. Methods. In the present study, we examined the expression of TLR2 and TLR4 on monocytes from 48 HIV-infected patients and 21 healthy control subjects by flow cytometry. Results. We found that freshly isolated monocytes from HIV-infected patients displayed enhanced expression of TLR2 but not TLR4, that TLR2 expression on the surface of monocytes was significantly increased upon stimulation of HIV type 1 envelope protein gp120, and that TLR2 stimulation in HIV-infected patients induced increased viral replication and TNF-α response. Conclusion. Our findings suggest potential roles for TLR2 in chronic immune activation and viral replication in HIV infection.