HIV-1 Restriction in Systemic Lupus Erythematosus Involves Iron Homeostasis
Authors: Kumari Namita , Ahmad Asrar , Wang Songping , Nekhai Sergei 
Published: December 2023

INTRODUCTION: Over the past two decades, there has been a growing emphasis on host restriction factors. However, a comprehensive understanding of their role in modulating HIV-1 infection in vivo requires further detailed investigation. Intracellular iron levels can affect HIV-1 replication by influencing expression of host cell viral restriction factors. Systemic Lupus Erythematosus (SLE) is characterized by upregulation of interferon response and the coexistence of SLE and HIV infection is rare. In lupus nephritis, deregulation of proteins involved in iron homeostasis have also been identified, with hepcidin suggested to play a role in disease severity . Hif1α, a protein regulated by hypoxia and under iron depletion, and reported to block HIV transcription, is upregulated in SLE. High levels of IL-10 and IL-16 which inhibits HIV infection are upregulated in SLE. APOBECs and oxysterols and Interferon Regulating Factors (IRFs) are also known to be upregulated in SLE. The current study is aimed to investigate ex vivo HIV-1 infection in peripheral blood mononuclear cells (PBMCs) derived from individuals SLE and identify factors that contributed to this inhibition.

METHODS: We utilized replication deficient VSVg-pseudotype HIV-1 and replication competent HIV-IIIB to infect SLE PBMCs. Real-time PCR was conducted to determine the upregulation of genes involved in HIV-1 replication. RNA-seq of PBMCs were done to identify altered restriction factors.

RESULTS: We investigated one round of HIV-1 infection in peripheral blood mononuclear cells (PBMCs) obtained from individuals with Systemic Lupus Erythematosus (SLE) and compared them to control PBMCs. We found that the HIV-1 infection in SLE-derived PBMCs was significantly reduced, as indicated by lower mRNA levels of Gag and Nef, two essential viral proteins.

Our ongoing study, which focused on the inhibition of HIV-1 replication ex vivo in Sickle Cell Disease (SCD), revealed interesting findings. RNA sequencing of PBMCs from individuals with SCD showed an upregulation of APOBEC3A, APOBEC3B, and CH25H, which are known restriction factors against HIV-1. Given these intriguing results, we decided to analyze the RNA expression of these restriction factors in SLE-derived PBMCs.

Surprisingly, we found a significant increase in the mRNA levels of APOBEC3A, APOBEC3B, and CH25H in SLE-derived PBMCs as well. This suggests that the enhanced expression of these restriction factors could be contributing to the reduced HIV-1 infection observed in SLE-derived PBMCs.

Additionally, we explored the RNA expression of HIF-1α and TFR1, which are iron-regulated factors, and found that their mRNA levels were upregulated in SLE-derived PBMCs. Furthermore, we observed an upregulation of interferon regulatory factors, including IL-10, IFN-β, and IRF-7, which are involved in immune responses and antiviral defense mechanisms. Interestingly IRF-7 was upregulated in SCD PBMCs too.

DISSUCION: The ongoing study in our lab on SCD and the study reported here are known for deregulated iron metabolism. Interestingly on one hand PBMCs derived from both inhibit HIV-1 and on other have some common restriction factors, iron regulated genes and IRF upregulated. Iron-regulated factors, such as TFR1, HIF-1α and ferroportin have been associated with antiviral effects. Modulating the expression or activity of these factors could influence HIV infection.

CONCLUSIONs: Taken together, our findings indicate that SLE-derived PBMCs exhibit a distinct gene expression profile that may confer protection against HIV-1 infection. The upregulation of APOBEC3A, APOBEC3B, CH25H, HIF-1α, TFR1, and interferon regulatory factors could collectively contribute to the observed reduction in HIV-1 replication in SLE-derived PBMCs. Further investigation is needed to fully understand the mechanisms underlying these observations and their implications for HIV-1 pathogenesis under altered intracellular iron levels influencing HIV-1 replication by modulating host cell factors.

Acknowledgments

This work was supported by NIH Research Grants 1R01HL125005, 5U54MD007597, P30AI087714 and P50AI150476. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.