Modulation of expression of the MHC class I-binding natural killer cell receptors, and NK activity in relation to viral load in HIV-infected/AIDS patients

The natural killer (NK) cells play an important role in viral infections vi a their spontaneous cytolytic activity against virus-infected cells as well as via secreting a variety of soluble mediators. The MHC class I-binding N K receptors of these cells have emerged as the most important regulators of the effector activities of cytolytic cells (both NK and CTL). We have stud ied the modulation of NK activity and the expression of NK receptors in HIV -infected/AIDS patients and report here that the NK activities of the patie nts with the lowest plasma HIV load were minimal and vice versa, suggesting a decrease in this activity following suppression of HIV replication. Inte restingly, the NK activity correlated negatively with the peripheral blood CD4(+) T-cell counts of these patients. Furthermore, these patients showed decreased percentages of CD56(+) cells expressing NK receptors of the immun oglobulin superfamily, whereas the percentages of CD8(+) cells expressing t hese receptors were increased. Moreover, the expression of C-type lectin-li ke NK receptor-associated invariant molecule CD94 was increased on CD8(+) c ells in these patients as compared with HIV-seronegative controls. These ch anges in the expression of NK receptors were also evident within groups of these patients having different viral loads. These results show, for the fi rst time, decreased innate immunity and changes in the expression of NK rec eptors on cytolytic cells in relation to viral burden in HIV-infected/AIDS patients. (C) 2001 Wiley-Liss, Inc.