Background: Natural killer (NK) cells play a crucial role in anti-viral immune responses. Our study aims to determine the effects of acute HIV infection on the engagement and expansion of NK cells and the cellular and molecular mechanisms regulating their activity and function in response to natural HIV-1 infection, by studying unique samples from some of the earliest stages of HIV infection.

Methods: Specimens from participants in the RV217 Early Capture HIV Cohort (ECHO) in East Africa and Thailand were used to investigate longitudinal NK cell modulations in 22 participants. We analyzed 4 timepoints: Pre-acquisition (28-365 days prior to acquisition), peak viral load (VL) (days 14-25), set-point (days 30-60) and chronic infection (>300 days). A 26-parameter flow cytometry panel was used to determine NK cell frequency and phenotype. Sorted NK cells from each donor were used for RNAseq analysis.

Results: At peak VL, we observed several changes in NK cells, such as increased activation measured by HLA-DR+CD38+, higher expression of transcription factor T-bet and the heterodimer CD94/NKG2A, together with a significant decreased of the inhibitory receptor ILT-2. Expression of inhibitory receptor KLRG1 starts decreasing around peak VL and reached significant level at set-point and chronic stage. Expansion of memory FcRg- NKG2C+ cells was not observed until the chronic stage. Moreover, RNAseq analysis revealed a negative correlation between viral loads and the expression of genes involved in NK cell cytolytic function and regulation, including ADGRE4P, SLC11A1, NR1D1 and CRNDE. Gene Set Enrichment Analysis showed that pathways related to the negative regulation of viral genome replication and viral processes were upregulated at setpoint VL.

Conclusions: Our preliminary data describes significant NK cell phenotypic and molecular changes in response to HIV acquisition. Understanding the impact of these genetic changes could provide valuable insight in the development of HIV prevention and cure strategies.