Host-adapted strains of Salmonella enterica cause systemic infections and have the ability to persist systemically within granulomas for long periods of time. Persistently infected hosts are often asymptomatic and transmit disease to nave hosts, thereby serving as a critical reservoir for disease. From the bacterial perspective, persistent infection is essential for microbial survival in nature. However, very little is known about the molecular mechanisms involved in persistent Salmonella infections and transmission between mammalian hosts. Increased knowledge of the molecular mechanisms of Salmonella persistence may lead to the ability to eradicate the Salmonella carrier state pharmacologically. Our long-term goal is to understand how Salmonella persists within tissues of mammalian hosts for preventive and therapeutic purposes. The objective of this proposal, which is our next step in pursuit of this goal, is to identify host pathways involved in granuloma dynamics and to determine how Salmonella manipulates host cells for long-term survival. The premise that will be tested in this application is that Salmonella injects virulence factors into granuloma macrophages that both promote an anti-inflammatory state and block specific proinflammatory responses in order to persist in mammalian hosts. We propose to study the molecular mechanisms of persistent Salmonella infections in granulomas of mammalian hosts.
Aim 1 will characterize the cellular organization and molecular regulation of granulomas during persistent Salmonella mouse infection, with a particular focus on visualization and analysis of gene expression of granuloma macrophages in tissue sections by spatial transcriptomics.
In Aim 2, we will identify mechanisms of Salmonella-dependent manipulation of granuloma macrophages.
Aim 3 will characterize the role of the Type 6 secretion system during persistent Salmonella infection. The proposed research is innovative because we investigate the spatial transcriptomics of granuloma macrophages, a heretofore- unexamined pathogen niche. Insight into host-pathogen interactions during persistent infection of a mammalian host is impactful as novel biomarkers and treatments of asymptomatic carriers are needed for eradication of this disease reservoir.

Public Health Relevance

Many enteric pathogens that cause high levels of morbidity and mortality are spread via the fecal oral route. Thus, an increased understanding of the molecular mechanisms that influence pathogen persistence within granulomas and their impact on host-to-host transmission will have a large impact on human health.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
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Host Interactions with Bacterial Pathogens Study Section (HIBP)
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Alexander, William A
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Stanford University
Schools of Medicine
United States
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