Preliminary observations on fluids incubated with Wuchereria bancrofti using the immunochromatographic test

Abstract

To assess the performance of the immunochromatographic test for filariasis, adult Wuchereria bancrofti worms were incubated under different conditions. The tests were strongly positive with incubation fluids from both living and mechanically damaged females. Negative results were observed with incubation fluids from all male worms and from intact dead females. The demonstration, in 1946, that parasite antigen is present in the blood of subjects with filarial infection 5 provided the foundation for the more recent development of antigen detection assays for Bancroftian filariasis cases using monoclonal antibodies. These are known as the Og4C3 test 7 and immunochromatographic test (ICT) 9 . The commercially available ICT provides an unprecedent sensitive and rapid method (taking just a few minutes) for diagnosing adult worm infection in Bancroftian filariasis cases. To further explore the sensitivity of the ICT diagnostic test, living adult Wuchereria bancrofti were obtained at the time of surgery from two microfilaremic patients who had signed an informed consent statement and previously received antifilarial treatment. These worms were incubated in vitro and supernatants were tested for filarial antigen. KeyAt the time of surgery for hydrocele repair, a segment of lymphatic vessel containing living adult Wuchereria bancrofti worms was excised from each patient. The vessel segments were placed in a Petri dish with sterile 0.9% saline solution at room temperature, incised with scissors, and for each patient, one living female and one living male worm actively emerged from the vessel. The male and female worms were placed in separate Petri dishes and gently washed three times with sterile saline.Term definitions. Female worm: longer worm with living embryos seen inside the uterus on microscopic examination (100X); male worm: shorter worm with a coiled caudal end seen on microscopic examination (100X); living worm: active and intact in appearance and, when observed with naked eye, exhibiting patterns of continuous movement characteristic of those seen on ultrasound, described previously as the filaria dance sign (FDS) 1 ; dead worm: inactive for at least 15 minutes, with no subsequent movement detected by the naked eye; mechanically disrupted worm: a worm that had died spontaneously in vitro, with subsequent disruption of the cuticle using forceps.