Background:  HIV infection and subsequent ART have been associated with an increased incidence of dyslipidemia and cardiovascular disease. However, the role of viral infection in induction of dyslipidemia remained controversial. 

Methods:  We followed 8 macaques prospectively for 6 months after being switched from normal to atherogenic diet, and then for additional 2 months after infection with simian immunodeficiency virus (SIV) _mac239 (atherogenic diet +SIV). Non-denaturing 2-dimensional PAGE was used to characterize HDL composition. Nef in macaque plasma and liver was measured by Western blotting. Expression of ABCA1 in liver was characterized by immunohistochemistry with quantitative image analysis. Recombinant HIV-1 Nef was produced in Escherichia coli and myristoylated in vitro.

Results:  On a background of atherogenic diet, SIV infection drove remodeling of high-density lipoprotein (HDL), characterized by significantly increased ratio of lipid-poor HDL particles with pre-b electrophoretic mobility to more mature HDL particles with a mobility (pre-b-1/a-5 ratio changed from 4.01 on normal diet to 4.53 on atherogenic diet to 10.15 on atherogenic diet + SIV, p <0.05 by Tukey post test comparison). Such increase suggests an SIV-specific block to HDL remodeling at the step of conversion of pre-β-1 to α-5 particles. This conversion is mediated by ABCA1 and takes place predominantly in the liver, suggesting that SIV inhibits ABCA1 activity in the liver. Consistent with this hypothesis, ABCA1 was significantly down-regulated in the livers of the infected macaques (image analysis performed on 2 liver samples showed decrease of ABCA1-specific staining from 50±3% to 25±5%, p <0.01). Although little or no infected cells were found in liver, Nef could be detected in this tissue and also in plasma (50 to 100 ng/mL). Soluble extracellular myristoylated Nef inhibited ABCA1-dependent cholesterol efflux from macrophages and hepatocytes. Sera from SIV-infected macaques inhibited cholesterol efflux, and this effect was eliminated when Nef was immunodepleted from the sera.

Conclusions:  Our results show that Nef released from SIV (or HIV-1) -infected cells can affect cholesterol efflux from uninfected peripheral cells, including macrophages and hepatocytes, inhiting reverse cholesterol transport.  This effect of Nef leads to changes in HDL metabolism and causes the alterations in HDL profiles observed in SIV-infected macaques. Therefore, lentiviral infection induces fundamental alterations in lipid metabolism that may contribute to increased risk of cardiovascular disease.