title: Temporal and anatomical host resistance to chronic Salmonella infection is quantitatively dictated by Nramp1 and influenced by host genetic background.
abstract: The lysosomal membrane transporter, Nramp1, plays a key role in innate immunity and resistance to infection with intracellular pathogens such as non-typhoidal Salmonella (NTS). NTS-susceptible C57BL/6 (B6) mice, which express the mutant Nramp1D169 allele, are unable to control acute infection with Salmonella enterica serovar Typhimurium following intraperitoneal or oral inoculation. Introducing functional Nramp1G169 into the B6 host background, either by constructing a congenic strain carrying Nramp1G169 from resistant A/J mice (Nramp-Cg) or overexpressing Nramp1G169 from a transgene (Nramp-Tg), conferred equivalent protection against acute Salmonella infection. In contrast, the contributions of Nramp1 for controlling chronic infection are more complex, involving temporal and anatomical differences in Nramp1-dependent host responses. Nramp-Cg, Nramp-Tg and NTS-resistant 129×1/SvJ mice survived oral Salmonella infection equally well for the first 2-3 weeks, providing evidence that Nramp1 contributes to the initial control of NTS bacteremia preceding establishment of chronic Salmonella infection. By day 30, increased host Nramp1 expression (Tg>Cg) provided greater protection as indicated by decreased splenic bacterial colonization (Tg<Cg). However, despite controlling bacterial growth within MLN as effectively as 129×1/SvJ mice, Nramp-Cg and Nramp-Tg mice eventually succumbed to infection. These data indicate: 1) discrete, anatomically localized host resistance is conferred by Nramp1 expression in NTS-susceptible mice, 2) restriction of systemic bacterial growth in the spleens of NTS-susceptible mice is enhanced by Nramp1 expression and dose-dependent, and 3) host genes other than Nramp1 also contribute to the ability of NTS-resistant 129×1/SvJ mice to control bacterial replication during chronic infection.
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, Washington, United States of America.
authors.forename: Wendy P
authors.initials: WP
authors.lastname: Loomis
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, Washington, United States of America.
authors.forename: Matthew L
authors.initials: ML
authors.lastname: Johnson
authors.affiliation: Department of Comparative Medicine, University of Washington, Seattle, Washington, United States of America.
authors.forename: Alicia
authors.initials: A
authors.lastname: Brasfield
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington, United States of America.
authors.forename: Marie-Pierre
authors.initials: MP
authors.lastname: Blanc
authors.affiliation: Department of Comparative Medicine, University of Washington, Seattle, Washington, United States of America.
authors.forename: Jaehun
authors.initials: J
authors.lastname: Yi
authors.affiliation: Department of Microbiology, University of Washington, Seattle, Washington, United States of America; Departments of Medicine and Genome Sciences, University of Washington, Seattle, Washington, United States of America.
authors.forename: Samuel I
authors.initials: SI
authors.lastname: Miller
authors.affiliation: Department of Laboratory Medicine, University of Washington, Seattle, Washington, United States of America; Department of Microbiology, University of Washington, Seattle, Washington, United States of America.
authors.forename: Brad T
authors.initials: BT
authors.lastname: Cookson
authors.affiliation: Department of Comparative Medicine, University of Washington, Seattle, Washington, United States of America.
authors.forename: Adeline M
authors.initials: AM
authors.lastname: Hajjar
mesh_terms: D000483:Alleles; D000818:Animals; D001835:Body Weight; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002875:Chromosomes; D005838:Genotype; D006720:Homozygote; D007113:Immunity, Innate / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D012481:Salmonella Infections, Animal / Q000235:genetics* / Q000382:microbiology; D019779:Salmonella enterica / Q000472:pathogenicity; D012486:Salmonella typhimurium / Q000472:pathogenicity*; D013997:Time Factors; D019076:Transgenes; D000099173:Natural Resistance-associated Macrophage Protein 1
chemical_list: D027682:Cation Transport Proteins; D000099173:Natural Resistance-associated Macrophage Protein 1