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The present study incorporates the findings on in vitro and in vivo antifilarial activity in the marine sponge, Haliclona oculata using an experimental rodent infection of human lymphatic filarial parasite, Brugia malayi. The in vitro antifilarial action was determined on both adult female worms as well as microfilariae using two parameters viz. adverse effect on motility and inhibition in MTT reduction by the treated adult parasite over control worm. The antifilarial activity could be located in the methanol extract and one of its four fractions (chloroform). Bioactivity guided fractionation of chloroform fraction led to localization of in vitro activity in one of its eight chromatographic fractions. Methanol extract, chloroform fraction and one of the chromatographic fractions revealed IC(50) values of 5.00, 1.80, and 1.62μg/ml, respectively when adult B. malayi were exposed to these test samples for 72h at 37°C. Under similar exposure conditions, the IC(50) values for microfilariae were 1.88, 1.72 and 1.19μg/ml, respectively. The active test samples were found to be safe revealing >10 selectivity indices (SI) on the basis of cytotoxicity to Vero cells (monkey kidney cells) and therefore selected for in vivo evaluation against primary (adult B. malayi intraperitoneal transplanted jird) and secondary (subcutaneous infective larvae induced mastomys) screens. In primary jird model, the three test samples at 100mg/kg for five consecutive days by subcutaneous route demonstrated significant macrofilaricidal efficacy to the tune of 51.3%, 64% and 70.7% by methanol extract, chloroform and chromatographic fraction, respectively. The three samples demonstrated 45-50% macrofilaricidal activity with moderate embryostatic effect in secondary model at 5×500, 5×250 and 5×125mg/kg by oral route. Chromatographic fraction possessing highest antifilarial action was primarily found to be a mixture of four alkaloids Mimosamycin, Xestospongin-C, Xestospongin-D and Araguspongin-C in addition to few minor compounds., (Copyright © 2012 Elsevier Inc. All rights reserved.)

We earlier reported the successful experimental transmission of Wuchereria bancrofti from humans to the Indian leaf monkey (Presbytis entellus) [Misra, S., Tyagi, K., Chatterjee, R.K., 1997. Experimental transmission of nocturnally periodic Wuchereria bancrofti to Indian leaf monkey (Presbytis entellus). Experimental Parasitology 86,155-157.; Dube, A., Murthy, P.K., Puri, S.K., Misra-Bhattacharya, S., 2004. Presbytis entellus: a primate model for parasitic disease research. Trends in Parasitology 20(8), 358-360.] using a small number of animals. The present study, involving 27 langur monkeys, found the development of pathological manifestations ranging from filarial fever, lymphangitis, lymphadenitis, hydrocoele, and limb edema to minor histopathological changes in tissues after single, double, triple, or multiple inoculations of infective larvae of W. bancrofti recovered from Culex quinquefasciatus fed on human microfilaraemic blood. Thirty-eight percent of the infected langurs developed detectable microfilaraemia in their blood. Single or double larval exposure resulted in better worm establishment than multiple exposures with small numbers of larvae. All of the langurs receiving a single large inoculum and 85.71% of those receiving two inoculations harbored adult parasites. Worm establishment decreased with increasing number of larval inoculations. In all, 60% of infected langurs developed classical gross-pathological symptoms of lymphatic filariasis. Of these, 29.16% developed thickening of the lymphatics, 25% suffered from periodic rise in rectal temperature, and 16.66% developed scrotal swelling with presence of microfilariae in the hydrocoele fluid. Only one out of 25 langurs (4%) developed acute limb edema. It appeared that a single inoculum of a large number of infective larvae was able to induce maximum pathology. Fifty-six percent of the infected langurs acquired a peculiar sitting posture, retracting both the hind limbs, usually after 4-5 months of larval inoculation and eventually resulting in reduced mobility. Oral administration of diethylcarbamazine (citrate) at 12mg/kg for 12 consecutive days to one langur caused 80% suppression in microfilaraemia on day 8, killing all the adult parasites. Of the two immunosuppressed (cortisone- or prednisolone-treated) male rhesus monkeys included in the study, neither developed any of the above lymphatic symptoms or parasites after receiving larval inoculations on two or three occasions; however, a rise in rectal temperature in one of the animals was noticed. The present study thus reveals that the Indian leaf monkey, P. entellus, may serve as an ideal non-human primate model of human bancroftian filariasis for carrying out longitudinal studies on pathology, host-parasite interactions, and preclinical evaluation of candidate anti-filarial drugs or vaccines.

Immunocompetent mouse model for human filarial parasite Brugia malayi is urgently required in view of the paucity of commercial reagents for other susceptible rodent viz. mastomys and gerbil. Genes within the major histocompatibility complex have been reported to influence the susceptibility of mouse to helminth parasites. Attempts have therefore been made in the present investigation to experimentally infect various inbred strains of mice viz. NZB/BINJ, BALB/c, AKR, C(3)H, and SJL/J with H-2 haplotype (H-2: d, d, k, k, s, respectively) and outbred strains of mice viz. Parks and Swiss. Findings indicate that susceptibility of mice to B. malayi is strain associated. This is the first report on the successful completion of full developmental cycle of subperiodic B. malayi in NZB/BINJ, an immunocompetent mouse strain. In some of the other strains, partial development or low degree of establishment of worms was observed.