Dirofilaria immitis: detection of parasite-specific antigen by monoclonal antibodies in glomerulonephritis in infected dogs.

For the identification of circulating parasite antigens associated with immune-complex glomerulonephritis in dogs infected with Dirofilaria immitis, monoclonal antibodies (mAbs) were generated against adult worms. A total of 11 mAbs were selected for cloning because of their high productivity and their lack of cross-reactivity with Toxocara canis in indirect immunofluorescence tests. The ability of mAbs to detect circulating antigens was examined using an antigen-capture enzyme-linked immunosorbent assay. Of the 11 mAbs, only NAK-1, an IgG2a mAb, was capable of detecting circulating antigens in 75% of infected dogs. However, this mAb was highly species-specific in its detection of circulating antigens, since sera from dogs infected with other nematode parasites were negative. Furthermore, the mAb detected antigens at the same glomerular sites in which IgG and/or C3 were deposited. The antigen deposits were observed along capillaries and/or in mesangial cells. The epitope recognized by this mAb is probably a carbohydrate, as it remained stable for 1 h at 100 degrees C and was sensitive to periodate treatment. Two bands of 62 and 26 kDa, respectively, were detected on Western blots by the mAb when sera from dogs infected with D. immitis were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transblotted.