IL‐10 in HIV infection: increasing serum IL‐10 levels with disease progression—down‐regulatory effect of potent anti‐retroviral therapy

To examine the potential pathogenic role of IL‐10 in HIV infection, we measured serum IL‐10 levels in 51 HIV‐infected patients and 23 healthy controls both on cross‐sectional and longitudinal testing. All clinical groups (Centers for Disease Control (CDC) categories) of HIV‐infected patients had significantly higher circulating IL‐10 levels than controls, with the highest levels among the AIDS patients, particularly in patients with ongoing Mycobacterium avium complex (MAC) infection. Among 32 HIV‐infected patients followed with longitudinal testing (median observation time 39 months), patients with disease progression had increasing IL‐10 levels in serum, in contrast to non‐progressing patients where levels were stable. While both IL‐10 and tumour necrosis factor‐alpha (TNF‐α) increased in patients with disease progression, the IL‐10/TNF‐α ratio decreased in these patients, suggesting imbalance between these two cytokines. Finally, we found that highly active anti‐retroviral therapy (HAART) induced a significant, gradual decrease in IL‐10 levels but without normalization. These findings suggest a pathogenic role for IL‐10 in HIV infection, and may suggest a possible role for immunomodulating therapy which down‐regulates IL‐10 activity in addition to concomitant potent anti‐retroviral therapy in HIV‐infected patients.