IgG response against infective larvae of Dirofilaria immitis in experimentally infected cats

Somatic antigens from third stage larvae of Dirofilaria immitis (SL3) were used to detect IgG response against heartworm infection in 8 experimentally infected cats. A moderate specific anti-SL3 IgG response was found one mon th post-infection. Afterwards, antibodies decreased reaching a basal level 4 months post-infection and remained at this level until the end of the stu dy, 6 months post-infection. Western blot analysis showed specific recognit ion of polypeptides of 79, 73, 60, 52, 40 and 39 kDa by sera from infected cats 1 month post-infection, but not by sera taken prior to the infection. The low antigenicity of the SL3 antigen in the cat should allow the parasit e to escape the host's immune response.