Indirect fluorescent antibody technique with micro-fragments of Wuchereria bancrofti

Abstract

The indirect fluorescent antibody technique, using the actual causal agent as antigen, was evaluated as an immuno-diagnostic test for detecting patients who are sensitive to bancroftian filarial antigen. To achieve the economy in the use of the antigenic material micro-fragments, cut by means of a cryostat, of microfilariae and infective stage larvae of Wuchereria bancrofti were used. The usefulness of this technique was assessed with 3 batches of human sera:— 60 sera from elephantiasis patients, 208 sera collected in an endemic area of filariasis, and 105 sera from healthy citizens of New Zealand where filariasis is rare and found only in immigrants from the Pacific Islands. All elephantiasis sera gave good bright fluorescence with the internal tissue of both the microfilaria and infective stage larva, whereas all sera from New Zealanders failed to produce fluorescence. 42% of the sera obtained from the filariasis endemic area gave fluorescence of an intensity comparable to that observed from the elephantiasis sera. This percentage of the prevalence of filarial antibody obtained was compared with the microfilaraemia rates reported from previous epidemiological surveys. This difference and the pattern of the prevalence of filarial antibody was discussed and may be regarded as an indication of the sensitivity of this indirect fluorescent antibody technique in detecting also those persons who are sensitized to filarial antigen but do not possess detectable microfilariae in their peripheral blood.