Background: Chemokines provide critical immune cell homing and activation signals that if altered could affect the inflammatory milieu and cellular composition of lymphoid tissues. During HIV-1 and simian immunodeficiency virus (SIV)–infection, the virus triggers an increase in inflammation or activation, leading to immunodeficiency and development of opportunistic infections, such as in the lungs—a massive interface between the host and the environment.
Methods: Chemokine, cytokine, and chemokine receptor expression profiles were determined using real-time reverse transcriptase—polymerase chain reaction and in situ hybridization in hilar lymph nodes (HiLNs) from cynomolgus macaques at different stages after infection with SIV/DeltaB670. Immunostaining of tissue sections and flow cytometric analysis of cryopreserved cells were used to examine cellular compositions of lymph nodes.
Results: Interferon-gamma, type 1 chemokine, and cognate chemokine receptor mRNAs were upregulated, whereas type 2 and homeostatic chemokine and chemokine receptor mRNAs were down-regulated in HiLNs after SIV infection. Local SIV and interferon-gamma levels were positively correlated with type 1 chemokine levels but negatively correlated with type 2 and homeostatic chemokine levels. Using in situ hybridization, Pneumocystis carinii rRNA was detected in lung-draining lymph nodes from animals with P. carinii pneumonia. Changes in the cellular composition of HiLNs included decreased proportions of CD4+ cells and dendritic cells and increased proportions of CD8+, CXCR3+, and CCR5+ cells.
Conclusions: SIV infection of cynomolgus macaques dramatically alters the cellular homing signals of lung-draining lymph nodes, which correlated with changes in the immune cellular composition. These changes could contribute to the loss of immune function that defines AIDS.