Identification of NLRX1, a molecular target that can shut the door to HIV-1 and help make better vaccines and therapies.
Utilizing non-human primates (NHPs) to model HIV infection in humans has been well established and provides the opportunity to derive mechanistic insight in a controlled yet physiologically relevant system. We have been able to demonstrate that a dys-regulated inflammatory response leads to viral dissemination as early as day 1 of infection. We performed serial necropsies at Timepoints (0-Naiive) and (days 1, 3, 7 and 10 post SIV infection) and collected several tissues from over 40 monkeys that participated in this study. Using an unbiased systems biology approach, we were able to observe:
- Systemic dissemination of the virus as early as day 1 which indicates that it will be very difficult to develop therapies that can control HIV since it is spreading so quickly in the infected host
- Viral dissemination coincides with the development of a potent pro-inflammatory response as early as day 1 post infection, which included NLRX1; Expression of this molecule also coincides with the absence of anti-viral gene activity in early days of dissemination; NLRX-1 is known for its capacity to inhibit intrinsic antiviral innate immunity which could explain our observations that virus disseminates so quickly in all tissues of infected host; our research has led to the identification of upregulated expression of NLRX-1 as a potential mechanism that triggers inhibition of anti viral response and also a potential mechanism that suppresses SIV specific cellular immune responses. These findings were recently published in the high impact journal CELL and are the result of a continuous collaboration between my group and the Barouch group at Beth Israel.
We have corroborated some of these findings in two cohorts of human subjects. In one cohort, the MHRP RV217 acute infection cohort, we identify heightened pre-infection NLRX1 in multiple immune cells including monocytes and T cells as a positive correlate of HIV viral load during infection and NLRX1 expression is correlated with the presence of heightened inflammatory cytokines including IL-1. We have confirmed the ability for cytokines to augment NLRX1 in PBMC subsets in vitro. To demonstrate a mechanistic role for NLRX1 in promoting HIV infection, we utilized next generation gene editing by CRISPR RNP to target NLRX1 in resting memory CD4+ T cells, a major source of the HIV reservoir. Our preliminary findings indicate that knockdown of NLRX1 reduces primary HIV infection and delays induction of latency in our novel in vitro model of latency, the LARA. These findings highlight the critical role for pre-infection and early upregulation of NLRX1 as a mediator of HIV acquisition as well as a potential mechanism that promotes latency induction in CD4+ memory T cells.
We have also followed this work up by pursuing the impact of pre-infection and acute IL-1 family cytokines, and their regulators, on NLRX1 expression and HIV acquisition. Looking into the RV217 cohort, we find that key components of the inflammasome and IL-1 signaling (NLRP3, IFI16, CASP1, CASP4, IL1B, etc) are positive correlates of viral load and negative correlates of CD4 counts. Using recombinant cytokines and primary memory CD4+ T cells, we have demonstrated that pretreatment with IL-1b or IL-18 enhances HIV infection and augments NLRX1 expression in both infected and uninfected cells. Moving forward, we will utilize CRISPR and next generation single cell RNA sequencing techniques along with high dimensional flow cytometry to fully detail the function of NLRX1 and IL-1 cytokines in T cells during HIV infection. Further, we will use our novel in vitro latency model to define the function of NLRX1 and IL-1 family cytokines in promoting the establishment and maintenance of the HIV reservoir as well as the impact on viral reactivation strategies.
This research will be used as the foundation for investigating new treatment strategies that reduce NLRX1 expression and function during HIV infection. We also plan to investigate how anti-IL-1 therapies, multiple are currently FDA-approved, can be leveraged in HIV infection to limit viral acquisition, dissemination, and reservoir establishment. Effective targeting of the IL-1/NLRX1 axis may provide the unique opportunity to limit acquisition, reduce reservoir establishment, and promote restoration of normal immune function, which combined can lead to greater control of HIV disease and eventually an effective cure. I am planning to recruit a new junior faculty to develop this novel high profile program that can result in major breakthrough for clinical development of vaccines and cure strategies to HIV-1.