This new proposal entitled The alveolar macrophage pool is a reservoir of HIV addresses a fundamental question; specifically, does the alveolar macrophage pool serve as a reservoir of HIV even when peripheral viral suppression is achieved by anti-retroviral therapy (ART) and if so, how does this reservoir alter the environment within the alveolar space and impair alveolar macrophage immune function? This is a critical question to address as lung infections remain the leading cause of death in persons living with HIV even when they are adherent to ART. We have compelling experimental evidence that HIV infection inhibits anti-oxidant defenses within the alveolar space and causes severe redox stress. Based on preliminary data presented in this proposal, we hypothesize that HIV inhibits the expression and actions of Nrf2, the master transcription factor that activates the anti-oxidant response element (ARE), in part by inducing zinc deficiency in this vulnerable microenvironment, and thereby prevents the alveolar epithelium and the alveolar macrophage from generating glutathione and other anti-oxidants that are critically required to maintain a healthy redox potential within the alveolar space. We further hypothesize that as a result of this targeted inhibition of the Nrf2-ARE signaling pathway, HIV promotes its own ability to infect alveolar macrophages and accumulate a large pool of intracellular pro-virus that produces a large HIV reservoir within the alveolar space. In parallel, HIV-induced oxidative stress shifts the alveolar macrophage toward alternative activation (so called 'M2 phenotype'). As a consequence, the innate immune capacity of the alveolar macrophage is impaired and this not only confers further resistance to clearing the viral reservoir but also renders the infected individual susceptible to serious lung infections. Our collaborative team of basic and clinical investigators will leverage our ongoing collaborative clinical studies in HIV-infected individuals. As a result, we not only have ongoing access to alveolar epithelial lining fluid and macrophages from well-defined subsets of HIV-infected individuals, we also have the expertise to apply state-of-the-art basic techniques in HIV pathogenesis, metabolomics, and redox signaling to test our hypotheses. In parallel, we are already conducting a prospective clinical trial of dietary zinc and S-adenosylmethionine (a thiol anti-oxidant that among its many actions increases the glutathione pool in the alveolar space) in HIV-infected individuals with inadequate immunological responses to ART. This unique cohort will form the foundation for a greatly expanded clinical trial that will enable us to test the corollary hypothesis that therapeutic strategies designed to improve zinc bioavailability and the redox potential within the alveolar space can enhance alveolar macrophage innate immune function and significantly decrease the HIV reservoir in the lung. This project will produce novel insights into how we can target the alveolar macrophage pool to decrease HIV burden as well as improve lung health in these vulnerable individuals.
This new project entitled 'The alveolar macrophage pool is a reservoir of HIV' will test the hypothesis that HIV infection of alveolar macrophages inhibits the Nrf2-ARE anti-oxidant defenses, thereby rendering the macrophage susceptible to further HIV infection and the intracellular accumulation of pro-virus and making it a reservoir for latent HIV. We have extensive empiric evidence from experimental and clinical studies that HIV disrupts zinc transport and anti-oxidant defenses within the alveolar space, thereby causing severe redox stress that interferes with alveolar macrophage host immunity and renders these individuals susceptible to serious lung infections. This project will elucidate the mechanisms by which HIV alters the microenvironment within the alveolar space and creates a viral reservoir even when there is evidence of adequate peripheral viral suppression as reflected by undetectable viral loads in the blood.
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