Seronegative MSM at high-risk of HIV-1 acquisition show Immune quiescent profile with normal immune response against common antigens

HIV infection still represents a major public health problem worldwide, and a vaccine remains elusive. The study of HIV-exposed seronegative individuals (HESN) brings important information about the natural resistance to HIV, allows a better understanding of the infection and opens doors for new preventive and therapeutic strategies. Among HESN groups there are some men who have sex with men (MSM) with high-risk sexual behaviors, who represent an adequate cohort for the study of HESN because of their major exposure to HIV in the absence of infection. This study aimed to compare the immunological profile of Colombian seronegative MSM with different risk sexual behaviors. Sixty MSM at high-risk (n=16) and low-risk (n=44) of HIV-1 acquisition were included. No sex worker nor homozygous delta 32 mutation subjects were included. All the participants were negative for anti-HIV-1/2 antibodies and HIV-1 proviral DNA. The high-risk MSM presented a higher frequency of sexual partners in the last 3 months previous to the studys enrollment (Median 30 vs. 2), lifetime sexual partners (Median 1708 vs. 26), and unprotected anal intercourse (Median 12.5 vs. 2) than low-risk MSM. This group also showed a quiescent profile of T cells and NK cells, with a significantly lower percentage of CD4+CD38+, CD4+HLADR-CD38+, CD4+Ki67+ T cells, NKG2D+ NK cells (CD3-CD16+CD56+), a significantly higher percentage of CD4+HLADR-CD38- and a tendency to show a higher percentage of CD8+HLADR+CD38-T cells, than the low-risk group. Likewise, they showed higher mRNA levels of Serpin A1 from PBMCs. The results suggest that this cohort of MSM could be HESN individuals and their resistance would be explained by a quiescent profile of T cells and NK cells, and increased expression of Serpin A1. It is necessary to continue the study of MSM at high-risk of exposure to HIV-1 to better understand the natural resistance to HIV.