Alterations in expression of monocyte chemotactic protein-1 in the simian immunodeficiency virus model of disseminated Mycobacterium avium complex.

Mycobacterium avium complex (MAC) infection is the most common disseminated bacterial infection in untreated patients with acquired immunodeficiency syndrome (AIDS). We investigated the potential role of monocyte chemotactic protein-1 (MCP-1) in the pathogenesis of disseminated MAC, using the simian immunodeficiency virus (SIV)/macaque model of AIDS. Macaques were inoculated with SIV, followed by challenge with a pathogenic AIDS isolate of M. avium 14 days later. After challenge with M. avium, marked increases in serum MCP-1 levels were detected in SIV-infected macaques, a finding that was duplicated in coinoculated bronchoalveolar macrophages. MCP-1 levels were significantly higher in SIV-infected macaques than in non-SIV-infected controls (327.1 vs. 151.5 pg/mL, respectively; P=.04), suggesting that up-regulation of MCP-1 contributes to the development of progressive mycobacterial disease. Similarly, morphometric analysis revealed increased expression of MCP-1 in hepatic microgranulomas from SIV-infected macaques. We conclude that the pronounced increases in MCP-1 levels demonstrated in tissue and serum samples after M. avium inoculation may play a role in the development of disseminated mycobacterial disease.