Phospholipid Metabolism Is Associated with Time to HIV Rebound upon Treatment Interruption

Abstract

Lipids are biologically active molecules involved in a variety of cellular processes and immunological functions, including inflammation. It was recently shown that phospholipids and their derivatives, lysophospholipids, can reactivate latent (dormant) tumor cells, causing cancer recurrence. However, the potential link between lipids and HIV latency, persistence, and viral rebound after cessation of antiretroviral therapy (ART) has never been investigated. We explored the links between plasma lipids and the burden of HIV during ART. We profiled the circulating lipidome from plasma samples from 24 chronically HIV-infected individuals on suppressive ART who subsequently underwent an analytic treatment interruption (ATI) without concurrent immunotherapies. The pre-ATI viral burden was estimated as time-to-viral-rebound and viral load set points post-ATI. We found that higher pre-ATI levels of lysophospholipids, including the proinflammatory lysophosphatidylcholine, were associated with faster time-to-viral-rebound and higher viral set points upon ART cessation. Furthermore, higher pre-ATI levels of the proinflammatory by-product of intestinal lysophosphatidylcholine metabolism, trimethylamine-N-oxide (TMAO), were also linked to faster viral rebound post-ART. Finally, pre-ATI levels of several phosphatidylcholine species (lysophosphatidylcholine precursors) correlated strongly with higher pre-ATI levels of HIV DNA in peripheral CD4⁺ T cells. Our proof-of-concept data point to phospholipids and lysophospholipids as plausible proinflammatory contributors to HIV persistence and rapid post-ART HIV rebound. The potential interplay between phospholipid metabolism and both the establishment and maintenance of HIV latent reservoirs during and after ART warrants further investigation.IMPORTANCE The likelihood of HIV rebound after stopping antiretroviral therapy (ART) is a combination of the size of HIV reservoirs that persist despite ART and the host immunological and inflammatory factors that control these reservoirs. Therefore, there is a need to comprehensively understand these host factors to develop a strategy to cure HIV infection and prevent viral rebound post-ART. Lipids are important biologically active molecules that are known to mediate several cellular functions, including reactivating latent tumor cells; however, their role in HIV latency, persistence, and post-ART rebound has never been investigated. We observed significant links between higher levels of the proinflammatory lysophosphatidylcholine and its intestinal metabolic by-product, trimethylamine-N-oxide, and both faster time-to-viral-rebound and higher viral load set point post-ART. These data highlight the need for further studies to understand the potential contribution of phosphatidylcholine and lysophosphatidylcholine metabolism in shaping host immunological and inflammatory milieu during and after ART.

Keywords: HIV; HIV persistence; TMAO; choline; lipids; lysophosphatidylcholine; lysophospholipid; phospholipid; viral rebound.

FIG 1

Higher pre-ATI lysophospholipid metabolism and its bioactive by-products associate with faster post-ATI time to viral rebound. (A) Lipids whose pre-ATI levels associate with post-ATI time to viral rebound, as determined by the Cox proportional-hazards model. Lipids with P < 0.01 and hazard ratio (HR) > 5 are shown in red and labeled. (B) Lipid pathway analysis of plasma lipids whose pre-ATI levels associated with time to viral rebound with P < 0.05 using LIPEA (Lipid Pathway Enrichment Analysis; https://lipea.biotec.tu-dresden.de/home). The graph shows all implicated pathways with FDR < 0.05. Numbers beside each pathway represent the number of dysregulated lipids within the particular pathway. GPI, glycosylphosphatidylinositol. (C) Lipid classes whose pre-ATI levels associate with post-ATI time to viral rebound, as determined by the Cox proportional-hazards model. FDR was calculated using the Benjamini-Hochberg approach. (D) Confirmatory analysis of the three lysophospholipid classes using the Mantel-Cox test. Low pre-ATI levels are levels lower than the group median; high pre-ATI levels are levels higher than the group median. (E) Participants were separated into shorter or longer time-to-viral-rebound groups by the median of days to viral rebound; the levels of TMAO were higher in individuals who rebounded faster than in individuals who rebounded slower. Mann-Whitney U test was used for statistical analysis. (F) Spearman’s rank correlation between pre-ATI TMAO and post-ATI time to viral rebound. Statistical analyses were performed in R and Prism 7.0 (GraphPad).

FIG 2

Pre-ATI phospholipid metabolism associates with post-ATI viral load set point and pre-ATI HIV DNA. (A) Spearman’s rank correlations between pre-ATI lipids and post-ATI viral load set point. Lipids with P < 0.01 and Spearman rho > 0.5 are shown in dark blue and are labeled. (B to D) Correlations between pre-ATI levels of LPC class (B), LPE class (C), or LPC (20:4) lipid species (D) and post-ATI viral load set point. Each symbol shows the value for one HIV-positive individual. (E) Spearman’s rank correlations between pre-ATI lipids and pre-ATI total HIV DNA measured in peripheral CD4⁺ T cells. Lipids with FDR < 0.1 and Spearman rho > 0.5 are shown in dark blue and are labeled. (F to H) Correlations between pre-ATI levels of several phosphatidylcholine species and pre-ATI levels of HIV DNA in peripheral CD4⁺ T cells. All correlations were evaluated using Spearman’s rank correlation coefficient tests. Statistical analyses were performed in R and Prism 7.0 (GraphPad).