Anxiong Long [1], Maike Sperk [1,2], Wang Zhang [1,3], Anders Sönnerborg [1], Ujjwal Neogi [1,3]
Affiliates: [1] Karolinska Institutet, Huddinge, Stockholm, Sweden. [2 ]University of Tuebingen, Tuebingen, Germany. [3] KTH Royal Institute of Technology, Sweden.

Acute HIV infection is associated with a marked induction of several pathways associated with inflammation, CD4 T cell depletion, and seeding of the viral reservoir. Many of these processes do not fully resolve on short term antiretroviral therapy (ART) (<5 years), despite complete and durable suppression of viremia. The effects of long-term successful ART and the linkage between levels of biomarkers representing these pathways remain unclear and could provide useful insight into disease progression and pathogenesis. We, therefore, assessed the identity of soluble biomarker levels in chronic HIV infection in both treatment-naïve and ART-treated individuals.

Plasma samples were obtained from three categories of age- and sex matched individuals; HIV-1-positive male patients on long-term ART (n=10) median (IQR) 19 (17-20) years, treatment naïve patients with viremia (VP, n=14) and HIV-1-negative persons (HC, n=11). Plasma soluble factors were analyzed using the proximity extension assay (PEA) targeting 92 factors. Statistical analysis was performed with in-house R script and Qlucore Omics Explorer version 3.2.

Among the 92 proteins, 82 could be detected in >50% of the samples and were subsequently used for the explorative analysis. Based on the clustering profile and principal component analysis the major pathways enriched were cytokine-mediated signaling pathway (GO: 0019221), chemokine-mediated signaling pathway (GO:0070098), Programmed Cell Death (GO:0012501) and cell surface receptor signaling (GO:0007166). These four pathways included 29 soluble biomarkers. In concordance with other studies, elevations of pro-inflammatory cytokines and chemokines were seen in VP. In patients on long term suppressive ART, most of these protein levels were comparable to HC confirming that ART does not only lead to a pronounced decline in viral load but also reconstitutes immunity almost to a physiological level. Interestingly, in patients on ART, levels of killer cell lectin-like receptor subfamily D member 1 (KLRD1) were in between those of HC (p< 0.05) and VP (p< 0.001). This receptor is expressed on Natural Killer cells and plays a major role in mediating NK cytotoxicity.

Long-term ART normalizes the overall expression of cytokines, chemokines, and death receptor ligands. However, some biomarkers do not go back to physiological levels indicating that immunological events still take place in HIV-1-infected patients on despite very long successful ART. . Analysis of cellular subsets other than T lymphocyte populations gains further insight into the long-term restoration of the immune system by ART.