Macrophage-Derived Factors with the Potential to Contribute to the Pathogenicity of HIV-1 and HIV-2: Roles of M-CSF and CXCL7

Human immunodeficiency virus (HIV) type 2 (HIV-2) is less pathogenic than HIV-1. However, the factors responsible for the differences in pathogenicity are still not well defined. To investigate this issue, we performed infection of primary human monocyte-derived macrophages (MDMs) with individual HIV-1 or HIV-2 strains and compared the levels of M-CSF, a cytokine shown to promote HIV-1 infection and replication in our previous studies, and CXCL7, a chemokine identified as being expressed at levels correlated with HIV type by our preliminary gene-expression analysis. We tested several HIV-2 isolates able to replicate in human MDMs and observed that all of them induced the production of M-CSF at high levels similar to those previously established for HIV-1 infection. In addition, the production of M-CSF in MDMs infected with HIV-1 or HIV-2 isolates correlated with the extent of virus replication. In contrast to M-CSF, the chemokine CXCL7 was differentially expressed between MDMs infected with HIV-1 or HIV-2 isolates, as revealed by qPCR and ELISA testing. Together, these results suggest that M-CSF induction may play similar roles in promoting the replication of HIV-1 and HIV-2, while differential regulation of chemokine expression may be an important factor contributing to the differential pathogenicity of the two HIV subtypes.