SPECIFIC IGG1 AND IGG2 ANTIBODY-RESPONSES OF DOGS TO LEISHMANIA-INFANTUM AND OTHER PARASITES

Sera from dogs naturally infected with Leishmania infantum were analys ed for the IgG subclass specificity of their antibody response by ELIS A. Dogs infected with L. infantum produced both IgG1 and IgG2 antibodi es with IgG2 being associated with asymptomatic infections and IgG1 be ing associated with disease (symptomatic dogs, non- or low-responsive to chemotherapy). The differential responses of IgG1 and IgG2 serum an tibodies in asymptomatic and symptomatic dogs may indicate a dichotomo us immune response to infection with L. infantum. To confirm this, on a broader scale, sera from dogs naturally exposed to an asymptomatic p rotozoan infection, Toxoplasma gondii, were also analysed as were sera from dogs exposed to the helminths, Dirofilaria immitis and Toxocara canis. Antibodies specific for T. gondii antigen detected in sera from 17 dogs were of the IgG2 subclass only. Both IgG1 and IgG2 antibodies to D. immitis and T. canis were present in the sera of naturally infe cted dogs but IgG1 appeared to be the predominant subclass. Furthermor e, in dogs experimentally infected with T. canis, selective regulation of IgG2 and IgG1 responses was apparent since production of the two s ubclasses occurred at different times following infection, with IgG2 l evels declining as IgG1 levels rose. Thus, the analysis of IgG subsets in parasitized dogs provides evidence of a dichotomous response to in fection. IgG2 is associated with asymptomatic protozoan infections and IgG1 is associated with helminth infections and disease caused by pro tozoan infection.