In vivo innate immune sensing of HIV-1 infection

SUMMARY/ABSTRACT HIV-1 remains a major public health challenge worldwide, with 1.3 million new infections and over 600,000 AIDS- related deaths in 2022. An effective vaccine that confers long-term protection against infection would be an essential tool in eradicating AIDS, but all vaccine candidates have been largely unsuccessful to date. This is due

to the unique biology of the virus and its extraordinary ability to escape immune responses. The immune events immediately following HIV-1 transmission have critical impacts on the ensuing disease course, but the underlying biology has proven difficult to detail. Overall, the innate immune response to a viral infection can establish a state

of viral resistance and contribute to controlling virus replication, but it also induces inflammation that can favor viral spread, immunopathology and disease progression. Studies of prospective cohorts of volunteers at high risk of contracting HIV-1 have revealed the sequence of events during acute infection, including the cytokine

storm induced by the innate immune responses. Mechanistic in vitro studies have demonstrated the capacity of diverse innate immune sensors to detect HIV-1 and induce cytokine production. However, the relative contribution of each innate immune cell type and sensing pathway following in vivo HIV-1 infection, and their

functional impact on both the virus and the host, are largely unknown. To overcome this limitation, we developed the MISTRG model of mice repopulated with a complete human immune system (“humanized mice”), including monocytes, macrophages, dendritic cells and NK cells that are essential to mounting innate immune responses.

MISTRG mice are permissive for HIV-1 infection and recapitulate several aspects of the immune responses observed in humans, including the cytokine storm triggered in the first few weeks after infection. Furthermore, we have recently developed a highly efficient protocol to knockout genes from the human immune system of

MISTRG mice, providing genetic tools that were previously exclusive to conventional mouse models. Using the innovative MISTRG model, we now plan to investigate the fundamental in vivo mechanisms of the innate immune response to HIV-1, following infection through both intravenous and mucosal routes. First, we will identify the

cellular source of cytokines that are released during the acute phase of HIV-1 infection. We will complement these descriptive studies with functional depletion experiments, to determine how each cytokine-producing cell type affects the virus and the infected host. Second, we will use gene knockout approaches to determine the

functional roles of membrane-bound versus intracellular innate immune sensors in the response to HIV-1. We hypothesize that different cell types contribute to HIV-1 sensing in vivo, that they rely on distinct sensors to do so, and that their concerted responses functionally impact the course of disease. Our findings will address a

significant knowledge gap, and may inform the rationale design of novel innate immune interventions for the prevention or therapy of HIV-1/AIDS.