Interleukin-12 as an adjuvant promotes immunoglobulin G and type 1 cytokine recall responses to major surface protein 2 of the ehrlichial pathogen Anaplasma marginale.
Anaplasma marginale is a tick-transmitted pathogen of cattle closely related to the human ehrlichiae, Ehrlichia chaffeensis and the agent of human granulocytic ehrlichiosis (HGE). These pathogens have in common a structurally conserved outer membrane protein (OMP) designated the major surface protein 2 (MSP-2) in A. marginale and HGE and OMP-1 in E. chaffeensis. Protective immunity against ehrlichial pathogens is believed to require induction of gamma interferon (IFN-gamma) and opsonizing immunoglobulin (Ig) subclasses directed against OMP epitopes that, in concert, activate macrophages for phagocytosis and killing. Because interleukin-12 (IL-12) acts as an adjuvant for protein immunization to induce IFN-gamma and protective immunity against intracellular pathogens, we hypothesized that as an adjuvant with MSP-2, IL-12 would augment type 1 recall responses to A. marginale. IL-12 was coadsorbed with MSP-2 to alum and shown to significantly enhance IFN-gamma production by lymph node cells (LNC) and LNC-derived CD4(+) T-cell lines from immunized calves following recall stimulation with A. marginale. LNC proliferation and IL-2 production were also enhanced in IL-12-treated calves. Elevated recall proliferative responses by peripheral blood mononuclear cells were still evident 9 months after immunization. Serum IgG levels were consistently increased in IL-12 immunized calves, predominantly due to higher IgG1 responses. The results support the use of IL-12 coadsorbed with OMP of ehrlichial pathogens in alum to amplify both antibody and type-1 cytokine responses important for protective immunity.
Tuo
W
W
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington 99164-7040, USA.
Palmer
G H
GH
McGuire
T C
TC
Zhu
D
D
Brown
W C
WC
D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000709:Anaplasma / Q000276:immunology* / Q000472:pathogenicity; D000818:Animals; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000276:immunology*; D001483:Base Sequence; D002417:Cattle; D016207:Cytokines / Q000096:biosynthesis / Q000145:classification / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004536:Ehrlichia / Q000276:immunology; D015870:Gene Expression; D006801:Humans; D007114:Immunization; D007074:Immunoglobulin G / Q000096:biosynthesis; D007156:Immunologic Memory; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000096:biosynthesis; D018664:Interleukin-12 / Q000494:pharmacology*; D008213:Lymphocyte Activation; D009500:Neutralization Tests
D000276:Adjuvants, Immunologic; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D016207:Cytokines; D017931:DNA Primers; D007074:Immunoglobulin G; C103348:msp2 protein, Anaplasma marginale; D018664:Interleukin-12; D007371:Interferon-gamma