Natural killer cell activity varies with viral burden in HIV-1 infection

Receptor expression and activity of natural killer (NK) cells vary with viral burden in patients infected with HIV-1, according to a report in the November Journal of Medical Virology.

Natural killer (NK) cells play an important role in controlling viral infections, particularly herpes virus infections in humans, the authors explain. Aberrant expression of NK cell receptors may result in ineffective immune responses against such viruses and against tumours.

Dr Ali Ahmad from the University of Montréal in Québec, Canada and colleagues studied the modulation of NK activity and the expression of NK receptors in 36 adults infected with HIV-1 who had AIDS. Thirty patients were receiving highly active antiretroviral therapy.

The average NK activities of the patients were significantly less than those of healthy controls, the authors report. Surprisingly, the researchers note, the NK activities showed a clear tendency to increase with increasing HIV-1 viral burden. NK activity showed a negative trend with increasing CD4+ T-cell counts, the report indicates.

HIV-1 infected patients had decreased percentages of cells expressing CD56 and CD16 but increased percentages expressing CD8, GL183, CD94, and CD57, the investigators say. There were also significant perturbances in NK receptor expression in CD8+ cytotoxic lymphocytes.

To our knowledge, the researchers write, this is the first report that suggests a decrease in NK cell activity after suppression of viral replication in HIV-infected/AIDS patients. Equally surprising was the negative correlation of NK activity with CD4+ T-cell counts of the patients.

Taken together, the authors conclude, these data suggest a complex, multifaceted interaction with viral replication, its gene products, and different immune parameters.

The investigators add, the decrease in NK activity accompanying a decrease in plasma HIV burden of HIV-infected/AIDS patients, shown here, may necessitate measures to enhance innate immunity of these patients.