Increased plasma levels of extracellular mitochondrial DNA during HIV infection: a new role for mitochondrial damage-associated molecular patterns during inflammation

HIV infection is characterized by a chronic inflammatory state. Recently, it has been shown that mitochondrial DNA (mtDNA) released from damaged or dead cells can bind Toll like receptor-9 (TLR9), an intracellular receptor that responds to bacterial or viral DNA molecules. The activation of TLR9 present within monocytes or neutrophils results in a potent inflammatory reaction, with the production of proinflammatory cytokines. We measured plasma levels of mtDNA in different groups of HIV⁺ patients, i.e., those experiencing an acute HIV infection (AHI), long term non progressors (LTNP), late presenters (LP) taking antiretroviral therapy for the first time, and healthy controls. We found that in AHI and LP mtDNA plasma levels were significantly higher than in healthy individuals or in LTNP. Plasma mtDNA levels were not correlated to peripheral blood CD4⁺ T cell count, nor to markers of immune activation, but had a significant correlation with plasma viral load, revealing a possible role for mtDNA in inflammation, or as a biomarker of virus-induced damage.