Gavin C Sampey, Mohammed Saifuddin, Angela Schwab, Robert Barclay, Shreya Punya, Myung-Chul Chung, Ramin M Hakami, Mohammad Asad Zadeh, Benjamin Lepene, Zachary A Klase, Nazira El-Hage, Mary Young, Sergey Iordanskiy, Fatah Kashanchi

HIV-1 infection results in a chronic illness since long-term HAART can lower viral titers to an undetectable level. However, discontinuation of therapy rapidly increases virus burden. Moreover, patients under HAART frequently develop various metabolic disorders, neurocognitive abnormalities and cardiovascular diseases. We have previously shown that exosomes containing trans-activating response (TAR) element RNA enhance susceptibility of undifferentiated naive cells to HIV-1 infection. The current study indicates that exosomes from HIV-1 infected primary cells are highly abundant with TAR RNA as detected by RT-real-time PCR. Interestingly, up to a million copies of TAR RNA per microliter were also detected in the serum from HIV-1 infected humanized mice suggesting that TAR RNA may be stable in vivo. Incubation of exosomes from HIV-1 infected cells with primary macrophages resulted in a dramatic increase of proinflammatory cytokines, IL-6 and TNF-beta, indicating that exosomes containing TAR RNA could play a direct role in control of cytokine gene expression. The intact TAR molecule was able to bind to PKR and TLR3 effectively, whereas 5-prime and 3-prime stems (TAR miRNAs) bound best to TLR 7 and 8 and none to PKR. Binding of TAR to PKR did not result in its phosphorylation and, therefore, TAR may be a dominant negative decoy molecule in cells. The TLR binding through either TAR RNA or TAR miRNA potentially can activate the NF-κB pathway and regulates cytokine expression. Collectively, these results imply that exosomes containing TAR RNA could directly affect the proinflammatory cytokine gene expression and may explain a possible mechanism of inflammation observed in HIV-1 infected patients under cART.