Objectives: HIV-1 modulates host cell epigenetic machinery to control its own replication and induce immune suppression. HIV-1 infection leads to activation of T regulatory cell (Treg), but the mechanism underlying this immune modulation is unclear. Treg plays a prominent role in gut-mucosal immune tolerance by restraining excessive effector T-cell responses, a mechanism that is known to be disturbed in chronic HIV-1 infection. DNA methylation plays a major role in Treg lineage commitment and immune homeostasis, which may be regulated by HIV. To investigate the mechanisms of aberrant methylation of the Treg marker FOXP3 in HIV-1 infection, we evaluated the expression pattern of methylation-related enzymes and its correlation to FOXP3 methylation.
Methods: FOXP3 promoter methylation in the colon mucosa and peripheral blood from HIV-infected patients and control subjects was measured using Pyrosequencing. Gene expression pattern of DNA methylation enzymes in the colon mucosa was investigated by Microarray and quantitative reverse transcriptase-polymerase chain reaction analysis in the same subjects.
Results: FOXP3 promoter was significantly (P ≤ 0.0001) demethylated in HIV-infected patients compared with control subjects in both tissues. Expression of DNA methyltransferase 1 (DNAMT1), DNA methyltransferase 1–associated protein 1(DMAP1), methyltransferase-like 7B (METTL7B), and methyltransferase-like 10 (METTL10) were significantly down regulated in HIV-infected patients compared with controls and had a significant positive correlation to FOXP3 promoter methylation.
Conclusions: We present evidence suggesting that altered methylation pattern of FOXP3 and accordingly higher Treg frequency in gut mucosa of HIV-infected patients may be because of aberrant methylation processing in HIV.