A 43-kDa circulating filarial antigen fraction of Wuchereria bancrofti in immunoprophylaxis against Brugia malayi in jirds.

A 43 kiloDaltan (kDa) antigen fraction (CFA2-6) isolated from microfilaraemic plasma of bancroftian filarial patients showed selective reactivity with sera samples collected from endemic normals. Antibodies raised against this antigen showed a strong reactivity with the surface of Brugia malayi infective larvae as well as microfilariae. Similar antigenic determinants were detected in the parasite extracts, but not in the excretory-secretory products. Further analysis was done on the immunoprophylactic potential of CFA2-6 in inducing immunity against Brugia malayi in Meriones unguiculatus (jird) in vivo. A strong protective response of approximately 84% was observed against the development of the filarial parasite in the jirds immunized with CFA2-6. The immunized jirds also showed a significant clearance (87%) of microfilariae inoculated intravenously. Approximately 65% of infective larvae failed to survive in jirds transferred with anti-CFA2-6 serum compared to the jirds transferred with sera from the control jirds. Passive transfer of anti-CFA2-6 antibody to the jirds followed by intravenous inoculation of microfilariae resulted in the reduction of 77% of circulating microfilariae. This study suggests that the 43-kDa CFA2-6 could stimulate a strong protective immune response against infective larvae and microfilariae in experimental animals.