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Characterization of the B‐cell immune response elicited in BALB/c mice challenged with Neospora caninum tachyzoites

2005; Wiley; Volume: 116; Issue: 1 Linguagem: Inglês

10.1111/j.1365-2567.2005.02195.x

1365-2567

Luzia Teixeira, Andreia Marques, Carla Sofia Meireles, Ana R. Seabra, Diana Rodrigues, Pedro Madureira, Augusto Faustino, Carolina Silva, Adília Ribeiro, Paula Ferreira, José Manuel Correia da Costa, Nuno Canada, Manuel Vilanova,

Parasitic Infections and Diagnostics

Summary Activation of B cells occurring in hosts infected with protozoan parasites has been implicated either in protective or parasite‐evasion immune‐mediated mechanisms. Intraperitoneal inoculation of Neospora caninum tachyzoites into BALB/c mice induces an acute response characterized by a rapid increase in the numbers of CD69‐expressing peritoneal and splenic B cells. This early B‐cell stimulatory effect preceded an increase in the numbers of total and immunoglobulin‐secreting splenic B cells and a rise in serum levels of N. caninum ‐specific immunoglobulins, predominantly of the immunoglobulin G2a (IgG2a) and IgM isotypes. Increased numbers of B cells expressing the costimulatory molecules CD80 and CD86 were also observed in the N. caninum ‐infected mice. The B‐cell stimulatory effect observed in mice challenged with N. caninum tachyzoites was reduced in mice challenged with γ‐irradiated parasites. Contrasting with the peripheral B‐cell expansion, a depletion of B‐lineage cells was observed in the bone‐marrow of the N. caninum ‐infected mice. Intradermal immunization of BALB/c mice with diverse N. caninum antigenic preparations although inducing the production of parasite‐specific antibodies nevertheless impaired interferon‐γ (IFN‐γ) mRNA expression and caused lethal susceptibility to infection in mice inoculated with a non‐lethal parasitic inoculum. This increased susceptibility to N. caninum was not observed in naïve mice passively transferred with anti‐ N. caninum antibodies. Taken together, these results show that N. caninum induces in BALB/c mice a parasite‐specific, non‐polyclonal, B‐cell response, reinforce previous observations made by others showing that immunization with N. caninum whole structural antigens increases susceptibility to murine neosporosis and further stress the role of IFN‐γ in the host protective immune mechanisms against this parasite.