title: Immune responses to human factor IX in haemophilia B mice of different genetic backgrounds are distinct and modified by TLR4.
abstract: Our laboratory develops protocols to prevent or reverse ongoing anti-hFIX IgG inhibitors in haemophilia B mice with a F9 gene deletion on BALB/c and C3H/HeJ backgrounds. C3H/HeJ F9(-/Y) mice develop high titre anti-hFIX IgG1 inhibitors and anaphylaxis, whereas most BALB/c F9(-/Y) mice have mild anti-hFIX IgG1 inhibitors and no anaphylaxis. Our aim was to determine if hFIX-specific B- and T-cell responses in BALB/c and C3H/HeJ F9(-/Y) mice trigger the difference in anti-hFIX immune responses. BALB/c and C3H/HeJ F9(-/Y) mice were challenged weekly with recombinant hFIX protein. Humoral immune responses were determined by IgG1 and IgG2a anti-hFIX ELISA, Bethesda assay for inhibitors and B-cell ELISpot on bone marrow and spleen cells. T-cell studies measured the TH 1 (IFN-γ) and TH 2 (IL-4) cytokine responses in splenocytes at the mRNA and protein level in response to hFIX protein. Antibody responses were also measured in C3H/HeJ/OuJ F9(-/Y) mice with restored toll-like receptor 4 (TLR4) function. BALB/c F9(-/Y) mice have a TH 2 skewed response and a reduction in anti-hFIX secreting plasma cells in the bone marrow. Independent antigen challenge revealed both strains generated equivalent IgG1 antibody titres to an intravenously delivered antigen. C3H/HeJ F9(-/Y) mice have a mixed TH 1 and TH 2 response (mainly TH 2). Importantly, TLR4 signalling has a modulatory role in the C3H background on the levels of anti-hFIX IgG1 and incidence of anaphylaxis. The background strain strongly impacts the immune response to hFIX, which can be significantly impacted by mutations in innate immune sensors.
authors.affiliation: Seattle Biomedical Research Institute, Seattle, WA, USA; Department of Pediatrics, University of Florida, Gainesville, FL, USA.
authors.forename: B K
authors.initials: BK
authors.lastname: Sack
authors.forename: X
authors.initials: X
authors.lastname: Wang
authors.forename: A
authors.initials: A
authors.lastname: Sherman
authors.forename: G L
authors.initials: GL
authors.lastname: Rogers
authors.forename: D M
authors.initials: DM
authors.lastname: Markusic
mesh_terms: D000818:Animals; D005164:Factor IX / Q000235:genetics / Q000276:immunology*; D002836:Hemophilia B / Q000276:immunology*; D006801:Humans; D051379:Mice; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology*
chemical_list: C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D005164:Factor IX
keywords: BALBc; C3H/HeJ; anaphylaxis; factor IX; haemophilia B murine model; immune response