CXCL16 in HIV infection – a link between inflammation and viral replication

Background  While some chemokines are thought to be protective in HIV-infected individuals by their ability to block HIV entry into T cells and macrophages, chemokines could also have harmful effects in HIV infection through their ability to promote inflammation. Here, we examined the regulation and the effects of CXCL16, a newly discovered chemokine of the CXC family, in HIV-infected patients. Materials and methods  We examined serum levels of CXCL16 in clinically well-defined subgroups of HIV-infected individuals both before (n = 62) and during HAART (n = 40) as well as in age- and sex-matched healthy controls (n = 30). We also examined the effects of CXCL16 on inflammatory and anti-inflammatory cytokines and HIV replication in peripheral blood mononuclear cells (PBMC). Results  Our main and novel findings were: (i) HIV-infected patients had significant raised CXCL16 levels according to disease severity and progression. (ii) During HAART, the immunological improvement was accompanied by a modest increase in CXCL16 level. (iii) While soluble CXCL16 promoted an anti-inflammatory response in PBMC from those on successful HAART, it induced an inflammatory response and enhanced HIV replication in PBMC from those with high viral load irrespectively of ongoing HAART. (iv) Recombinant HIV-tat protein significantly increased CXCL16 release in THP-1 macrophages. Conclusions  Our findings suggest a complex interaction between CXCL16 and HIV, promoting both inflammatory and anti-inflammatory effects as well as HIV replication, partly dependent on accompanying HIV replication.