Dynamics of immune responses related to clinical status in Brugia pahangi-infected dogs.

Clinical signs of lymph node enlargement, limb edema, lymph duct fibrosis, and microfilaremia were monitored in dogs with chronic Brugia pahangi infections. During the study a single rear limb of each dog was reinfected with multiple low doses of infective larvae. The changing immune responses to parasite antigens prepared from three sources--Brugia pahangi adult worm homogenate extract, adult worm excretory-secretory products, and microfilaria excretory-secretory products--were monitored by Western blot ELISA of antigens fractionated on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and by microtiter plate ELISA. Assays were used to detect antibodies in both the the IgG and IgE classes. A wide range of clinical manifestations was demonstrated in response to reinfection: asymptomatic, amicrofilaremic; asymptomatic, microfilaremic; acute short duration node enlargement and/or limb edema with microfilaremia; and chronic limb edema, amicrofilaremic. On microtiter plate ELISA, the dogs demonstrating the highest anti-adult worm homogenate titers were amicrofilaremic and were asymptomatic or developed chronic limb edema, dogs with high anti-mf ES titers were persistently amicrofilaremic, and the most marked increases against all three antigen sources upon reinfection occurred in low or amicrofilaremic dogs. Quantitative changes in antibody levels against the three crude antigen sources following reinfection were often paralleled by distinct changes in recognition of specific bands of antigens fractionated by SDS-PAGE.