Oral Presentation 49th Annual Scientific Meeting of the Australian and New Zealand Society for Immunology 2021

Th1 cell immunity to Salmonella is transient in the circulation and assumes liver-resident memory phenotype (#81)

Newton Peres 1 2 , Nancy Wang 1 , Joseph Benoun 3 , Paul Whitney 1 , Sven Engel 1 , Meghanashree Shreenivas 1 , Daniel Fernandez-Ruiz 1 , Ian Comerford 4 , Dianna Hocking 1 , Anna Erazo 1 5 , Irmgard Förster 5 , Andreas Kupz 6 , Thomas Gebhardt 1 , Shaun McColl 4 , Lynn Puddington 7 , Stephen McSorley 3 , Sammy Bedoui 1 , Richard Strugnell 1
  1. Department of Microbiology and Immunology, Peter Doherty Institute, Melbourne, VIC, Australia
  2. EMBL - Single Molecule Science, UNSW, Kensington, NSW, Australia
  3. Center for Comparative Medicine, University of California, Davis, CA, USA
  4. School of Biological Science, The University of Adelaide, Adelaide, SA, Australia
  5. Immunology & Environment, Life and Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany
  6. Centre for Molecular Therapeutics, James Cook University, Cairns, QLD, Australia
  7. Department of Immunology, University of Connecticut Health Center, Farmington, CT, USA

While Salmonella enterica is seen as an archetypal facultative intracellular bacterial pathogen where protection is mediated by CD4+ T cells and type 1 responses, this immunity cannot be found in the circulation after immunization. Exploiting a mouse model of vaccination, we show that the spleens of C57BL/6 mice vaccinated with live-attenuated Salmonella serovar Typhimurium (S. Typhimurium) strains carried a pool of CD4+ T cells that are transcriptionally active for ifng gene and could passively transfer protection, but only transiently. Circulating Salmonella-reactive CD4+ T cells highly expressed the liver-homing chemokine receptor CXCR6, accumulated over time in the liver and assumed dysfunctional characteristics associated with tissue-resident memory (Trm) T cells when ex vivo. Effector and resident Th1 subsets differ on the expression of a variety of membrane molecules, including CD69, KLRG1, CD101, LFA-1, P2rx7, ARTC2. Liver memory T helper 1 (Th1) cells showed enhanced reactivity for S. Typhimurium antigens after specific inhibition of P2rx7-mediated loss of functionality and preferential usage of TCR Vβ chains. Parabiosis and adoptive Trm transfer experiments demonstrated that non-circulating memory pools are important for optimal protection to lethal Salmonella strain. Our systematic study showed that CD4+ T cell-mediated immunity to Salmonella infection is circulant, but this is limited to a brief window during which Salmonella-specific CD4+ T cells migrate to peripheral tissues where becomes resident. Our observations are supported by volunteer studies of vaccination and highlight the importance of triggering tissue-specific immunity against systemic infections.