Since the SIV burdens in heart tissue were lower in the CART group macaques than the untreated animals, the animals were not clinically ill, and no opportunistic agents were identified, we believe that the myocarditis is due to the treatment with two NRTIs, resulting in cardiomyocyte injury and necrosis, subsequent mononuclear cell recruitment, lymphohistiocytic infiltration, and increased cardiac expression of TNF-α and CXCL9 in the affected animals. This evidence concerns the gene CXCL9 and myocarditis.