Abstract Body


It is unclear how elite controllers (EC) spontaneously control HIV in the absence of antiretroviral therapy (ART). NK cells significantly contribute to antiviral innate immune responses and can display memory characteristics mirrored by high NKG2C expression. We aimed to investigate the phenotype of NK cells in ECs and their memory features, which favor antiviral control.


NK flow cytometry analysis was performed on CD56+-sorted PMBCs from 15 EC and 12 non-controlling people living with HIV (PLHIV) on suppressive ART (non-EC), as well as 1st degree family members from both groups (N&#3f10 and N&#3f12, respectively): Live/Dead ViaKrome, HLA-DR, CD3, CD45, CD56, CD16, CD57, CD94, NKG2A, NKG2C, NKG2D, ILT2 (LILRB1), KIR2DL2/3, DNAM, NKp30, NKp46. Machine learning algorithms viSNE and FlowSOM were used to identify and analyze fifteen metaclusters. CMV IgG serology was measured with ELISA. Between-group comparisons were done with Mann-Whitney U tests.


Through unsupervised analysis we identified two CD57highNKG2Chigh metaclusters. One was characterized as CD57highNKG2Chigh KIR2low and exclusively present in CMV-seropositive individuals, from both the PLHIV and family members groups without HIV (MT12). The second CD57highNKG2Chigh metacluster was KIR2high and specific to PLHIV (MT14, Fig 1B). In this subset, EC had a greater NKG2C and ILT2 (LILRB1) expression than non-EC (P=0.036 and P=0.012, respectively). EC family members had a higher percentage of CD56-CD16+KIR2high NK cells, a cytotoxicity subset, than non-EC family members (P = 0.0026, MT9). NKG2C expression on this subset was greater in EC family members (P = 0.036). Deposition of H3K4me3 mark of open chromatin at immune gene promoters is a hallmark of long-term innate immune memory (also called trained immunity). An increased H3K4me3 enrichment at the promoter of KLRC2 gene, the coding gene for NKG2C, was observed in 3 EC in comparison to 3 non-EC (Fig 1C).


Unsupervised analysis revealed the presence of two distinct memory NKs subpopulations in PLHIV. CD57highNKG2ChighKIR2high NK cells were specific to PLHIV and had greater NKG2C and ILT2 expression in EC. CD57highNKG2ChighKIR2low NK cells were only present in CMV-seropositive individuals. A high capacity for target cell-induced IFNγ production has been attributed to these NK cells. Increased NKG2C expression together with enrichment of H3K4me3 at the promoter of KLRC2 suggests improved antiviral control in ECs through induction of trained immunity.