title: Characterizing the interactions between a naturally primed immunoglobulin A and its conserved Bacteroides thetaiotaomicron species-specific epitope in gnotobiotic mice.
abstract: The adaptive immune response to the human gut microbiota consists of a complex repertoire of antibodies interacting with a broad range of taxa. Fusing intestinal lamina propria lymphocytes from mice monocolonized with Bacteroides thetaiotaomicron to a myeloma fusion partner allowed us to recover hybridomas that captured naturally primed, antigen-specific antibody responses representing multiple isotypes, including IgA. One of these hybridomas, 260.8, produced a monoclonal antibody that recognizes an epitope specific for B. thetaiotaomicron isolates in a large panel of hospital- and community-acquired Bacteroides. Whole genome transposon mutagenesis revealed a 19-gene locus, involved in LPS O-antigen polysaccharide synthesis and conserved among multiple B. thetaiotaomicron isolates, that is required for 260.8 epitope expression. Mutants in this locus exhibited marked fitness defects in vitro during growth in rich medium and in gnotobiotic mice colonized with defined communities of human gut symbionts. Expression of the 260.8 epitope was sustained during 10 months of daily passage in vitro and during 14 months of monocolonization of gnotobiotic wild-type, Rag1-/-, or Myd88-/- mice. Comparison of gnotobiotic Rag1-/- mice with and without subcutaneous 260.8 hybridomas disclosed that this IgA did not affect B. thetaiotaomicron population density or suppress 260.8 epitope production but did affect bacterial gene expression in ways emblematic of a diminished host innate immune response. Our study illustrates an approach for (i) generating diagnostic antibodies, (ii) characterizing IgA responses along a continuum of specificity/degeneracy that defines the IgA repertoire to gut symbionts, and (iii) identifying immunogenic epitopes that affect competitiveness and help maintain host-microbe mutualism.
authors: From the Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri 63108 and Department of Pathology, The Johns Hopkins University, Baltimore, Maryland 21205.
authors: Daniel A
authors: DA
authors: Peterson
authors: From the Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri 63108 and.
authors: Joseph D
authors: JD
authors: Planer
authors: From the Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri 63108 and.
authors: Janaki L
authors: JL
authors: Guruge
authors: From the Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri 63108 and.
authors: Lai
authors: L
authors: Xue
authors: From the Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri 63108 and.
authors: Whitt
authors: W
authors: Downey-Virgin
authors: From the Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri 63108 and.
authors: Andrew L
authors: AL
authors: Goodman
authors: From the Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri 63108 and.
authors: Henning
authors: H
authors: Seedorf
authors: From the Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri 63108 and jgordon@wustl.edu.
authors: Jeffrey I
authors: JI
authors: Gordon
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000235:genetics / Q000276:immunology*; D001439:Bacteroides / Q000235:genetics / Q000276:immunology*; D004251:DNA Transposable Elements; D000939:Epitopes / Q000235:genetics / Q000276:immunology*; D056426:Genetic Loci / Q000276:immunology; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology*; D007413:Intestinal Mucosa / Q000276:immunology* / Q000382:microbiology; D051379:Mice; D018345:Mice, Knockout; D016296:Mutagenesis; D009154:Mutation; D019081:O Antigens / Q000235:genetics / Q000276:immunology; D013045:Species Specificity
chemical_list: D000907:Antibodies, Bacterial; D004251:DNA Transposable Elements; D000939:Epitopes; D007070:Immunoglobulin A; D019081:O Antigens
keywords: Immunoglobulin A; Immunoglobulin A (IgA); Microbiome; Molecular Evolution; Mucosal Immunology; Symbiosis