Anti-HSP70 Autoantibody Formation by B-1 Cells inToxoplasma gondii-Infected Mice

Abstract

Formation of anti-Toxoplasma gondii HSP70 (TgHSP70) antibody cross-reactive to mouse HSP70 (mHSP70) was observed in the sera of BALB/c (a resistant strain) and C57BL/6 (B6; a susceptible strain) mice after peroral infection with T. gondii cysts of the Fukaya strain. The levels of anti-mHSP70 immunoglobulin G (IgG) autoantibody production in B6 mice were higher than those in BALB/c mice. The isotype and subclass of IgG of anti-TgHSP70 monoclonal antibodies cross-reactive to mHSP70 were and ␥3. Anti-mHSP70 autoantibody in T. gondii-infected BALB/c and B6 mice was shown to be produced by the CD5 ؉ subset of B cells (B-1a cells) but not by conventional B cells (B-2 cells). The epitopes recognized by anti-mHSP70 autoantibody were located primarily in the C-terminal fragment of mHSP70.Toxoplasma gondii, an obligate intracellular parasitic protozoan, causes a life-threatening toxoplasmosis in fetuses or in immunocompromised humans and mice, and the mechanisms of antigen presentation of T. gondii-infected cells have been analyzed (2,45,46,48). We have previously demonstrated a potential role of human heat shock cognate protein 70 (hHSC70) in antigen processing and presentation of T. gondiiinfected cells to CD4 ϩ cytotoxic T lymphocytes in humans (44) and have reported anti-T. gondii HSP70 (TgHSP70) antibody formation in T. gondii-infected BALB/c and B6 mice (23).Members of the HSP family have been shown to have important functions as (i) intracellular detergents for aggregated and denatured molecules formed as a result of exposure of cells to physical stressors and (ii) molecular chaperones in peptide and protein transport between cell organelles (14,35,41). Of the HSP family members, HSP70 has been shown to be a major immunodominant antigen in bacterial and parasite infections as well as the preferred target of the humoral and cell-mediated immune responses to infection (7,28,49). The nucleic acid sequence of HSP70 is known to be highly homologous among different species. Indeed, the sequence of TgHSP70 is 68.1 and 74.1% homologous to those of mouse HSP70 (mHSP70) and hHSC70, respectively (6, 8, 47, 50); thus, it is possible that the high homology of HSP70 between T. gondii and hosts could induce autoreactive immune responses in T. gondii-infected hosts. Autoantibody induction against host components has been reported in infection with other parasites such as Trypanosoma cruzi (16), Plasmodium falciparum (21), Schistosoma mansoni (15), and Onchocerca volvulus (27). In particular, Mattei et al. demonstrated that sera from humans infected with malaria recognized the human HSP70, indicating that autoantibodies directed against host HSP70 could be induced by the homologous parasite protein (21). In contrast, humans infected with Echinococcus granulosus and Leishmania braziliensis did not induce autoimmune reactivity against homologous hHSP70, although specific antibodies reactive with parasite HSP70 were detected (4, 34).No such anti-host HSP70 autoantibody was induced in dogs during viscero-cutaneous leishmaniasis either ...

Pathogenicity of Toxoplasma gondii through B‐2 Cell‐Mediated Downregulation of Host Defense Responses

“…ϩ (B-2) cells from spleens of T. gondii-infected GKO mice were obtained by magnetic cell separation (Miltenyi Biotec) as previously described (8,14). The purity of these cells was Ͼ98%.…”

Correlation between the Avidity Maturation of Anti‐HSP70 IgG Autoantibody and Recombination Activating Gene Expressions in Peripheral Lymphoid Tissues of Toxoplasma gondii‐Infected Mice

“…The purities of B-1 cells and B-2 cells were 91.6% and 92%, respectively. The production of anti-TgHSP70 antibody and anti-mHSP70 autoantibody by B-1 and B-2 cells from T. gondii-infected BALB/c and B6 mice was detected by ELISA as previously described (1). Differences between mean values were analyzed by an unpaired Student's t test.…”

“…The avidity index was calculated by the following formula: percentage of urea-resistant IgG of total bound IgG (A 405 Urea ϩ /A 405 Urea -). B-1 cells and B-2 cells were purified from peritoneal exudate cells (PECs) of BALB/c and B6 mice 1 week after T. gondii infection as previously described (1). The purities of B-1 cells and B-2 cells were 91.6% and 92%, respectively.…”

“…The production of anti-mHSP70 autoantibody by B-1 and B-2 cells in Mice were perorally infected with 10 cysts of the Fukaya strain. By using rTgHSP70 protein as antigens, formation of anti-TgHSP70 antibody 2 and 9 weeks after T. gondii infection was tested by ELISA as previously described (1,17). (B) The avidity index of anti-TgHSP70 IgG antibody 2 and 9 weeks after T. gondii infection was analyzed.…”

“…B-1 and B-2 cells from PECs of BALB/c and B6 mice 1 week after T. gondii infection were purified as previously described (1). After 3 days of incubation at 37 C, formation of anti-TgHSP70 antibody in the supernatant of B-1 and B-2 cells was analyzed by ELISA.…”