Search

The recombinant heavy chain myosin of Brugia malayi (Bm-Myo) has earlier been reported as a potent vaccine candidate in our lab. Subsequently, we further enhanced its efficacy employing heterologous DNA prime/protein boost (Myo-pcD+Bm-Myo) immunization approach that produced superior immune-protection than protein or DNA vaccination. In the present study, we evaluated the efficacy of heterologous prime boost vaccination in combination with CpG, synthetic oligodeoxynucleotides (ODN) adjuvant in BALB/c mice. The results showed that CpG/Myo-pcD+Bm-Myo conferred 84.5 ± 0.62% protection against B. malayi infective larval challenge which was considerably higher than Myo-pcD+Bm-Myo (75.6 ± 1.10%) following immunization. Although, both the formulations of immunization elicited robust production of specific IgG antibody and their isotypes (IgG1, IgG2a, IgG2b, and IgG3); however, CpG/Myo-pcD+Bm-Myo predominantly enhanced the level of IgG2a suggesting Th1 biased immune response in presence of CpG. Furthermore, spleen isolated from mice that immunized with CpG/Myo-pcD+Bm-Myo had greater accumulation of CD4+, CD8+, and CD19+ B cells and there was an augmented expression of co-stimulatory molecules CD40, CD86 on host dendritic cells (DCs). In contrast to Myo-pcD+Bm-Myo group, the splenocytes of CpG/Myo-pcD+Bm-Myo immunized mice developed comparatively higher pro-inflammatory cytokines IL-2 and IFN-γ leaving anti-inflammatory cytokine levels unchanged. Moreover, CpG formulation also upregulated the RNA expression of IL-12 and TNF-α in spleenocytes. The current findings suggest that the use of CpG would be more advantageous as an adjuvant predominantly in DNA/protein prime boost vaccine against Bm-Myo and presumably also for filarial infection.

The current antifilarial treatments are not up to the mark partly due to deep location of filarial parasites in the human lymphatic system. We report here on the improvement in the antifilarial activity of ivermectin (IVM) using chitosan-alginate nanoparticles prepared by modified complex coacervation method. The nanoparticles were spherical having 155 nm size and 4.56 and 75.67% loading and entrapment efficiency respectively for IVM. The delivery system maintained the sustained release and significantly augmented the microfilaricidal (MIF) activity at a single low dose (200 μg/kg body weight, subcutaneously) in contrast to much higher dose of free ivermectin (400 μg/kg body weight, subcutaneously) against human lymphatic filariid, Brugia malayi in rodent host, Mastomys coucha. To substantiate increase in MIF activity, pharmacokinetics study was designed on Wistar rats which revealed a greater peak plasma concentration (45.3 ± 1.79 ng/ml), area under the concentration curve (298 ± 38.7 ng d/ml) and extended mean residence time (23.4 ± 8.56 days)of IVM in chitosan-alginate nanoparticles. Administration of 25 mg/kg of diethylcarbamazine following nanoparticle therapy significantly improved the MIF and macrofilaricidal action of encapsulated drug and was considered superior in this study.

More than 2 billion people are infected with helminth parasites across the globe. The burgeoning drug resistance against current anthelmintics in parasitic worms of humans and livestock requires urgent attention to tackle these recalcitrant worms. This review focuses on the advancements made in the area of helminth drug target discovery especially from the last few couple of decades. It highlights various approaches made in this field and enlists the potential drug targets currently being pursued to target economically important helminth species both from human as well as livestock to combat disease pathology of schistosomiasis, onchocerciasis, lymphatic filariasis, and other important macroparasitic diseases. Research in the helminths study is trending to identify potential and druggable targets through genomic, proteomic, biochemical, biophysical, in vitro experiments, and in vivo experiments in animal models. The availability of major helminths genome sequences and the subsequent availability of genome-scale functional datasets through in silico search and prioritization are expected to guide the experimental work necessary for target-based drug discovery. Organized and documented list of drug targets from various helminths of economic importance have been systematically covered in this review for further exploring their use and applications, which can give physicians and veterinarians effective drugs in hand to enable them control worm infections.

The present study is aimed to evaluate antifilarial activity of Xylocarpus granatum (fruit from Andaman) against human lymphatic filarial parasite Brugia malayi in vivo. The in vitro antifilarial activity has already been reported earlier for this mangrove plant which has traditionally been used against several ailments. Aqueous ethanolic crude extract, four fractions (ethyl acetate fraction, n-butanol fraction, water-soluble fraction and water-insoluble fraction) and pure molecule/s of X. granatum (fruit) were tested in vitro on adult worms and microfilariae (mf) of B. malayi and the active samples were further evaluated in vivo in B. malayi (intraperitoneally) i.p. transplanted in the jird model (Meriones unguiculatus) and Mastomys coucha subcutaneously infected with infective larvae (L3). The crude aqueous ethanolic extract was active in vitro (IC50: adult = 15.46 μg/ml; mf = 13.17 μg/ml) and demonstrated 52.8% and 62.7% adulticidal and embryostatic effect on B. malayi, respectively, in Mastomys at a dose of 5 × 50 mg/kg by oral route. The antifilarial activity was primarily localized in the ethyl acetate-soluble fraction which revealed IC50 of 8.5 and 6.9 μg/ml in adult and mf, respectively. This fraction possessed moderate adulticidal and embryostatic action in vivo in Mastomys. Out of eight pure molecules isolated from the active fraction, two compounds gedunin (IC50 = 0.239 μg/ml, CC50 = 212.5 μg/ml, SI = 889.1) and photogedunin (IC50 = 0.213 μg/ml, CC50 = 262.3 μg/ml, SI = 1231.4) at 5 × 100 mg/kg by subcutaneous route revealed excellent adulticidal efficacy resulting in to the death of 80% and 70% transplanted adult B. malayi in the peritoneal cavity of jirds respectively in addition to noticeable microfilaricidalo action on the day of autopsy. The findings reveal that the extract from the fruit X. granatum contains promising in vitro and in vivo antifilarial activity against human lymphatic filarial parasite B. malayi which could be attributed to the presence of two pure compounds gedunin and photogedunin.

The present study reports on the antifilarial activity of a marine sponge Haliclona exigua (phylum Porifera). The crude methanol extract and n-butanol-soluble fraction killed adult Brugia malayi at 31.25-microg/ml concentration (both in motility and 3-(4,5 dimethylthiazol-2-yl)-2,5 diphenyl tetrazolium bromide assay) while the chloroform fraction was lethal at a lower concentration of 15.6 microg/ml. The activity could be located in a single molecule araguspongin C which brought about mortality of worm at 15.6 microg/ml. In vivo evaluation of the crude extract (5 x 500 mg/kg, orally) and the chloroform fraction (5 x 250 mg/kg, orally) in B. malayi-infected rodent host, Mastomys coucha, did not show any significant microfilaricidal actions; however, microfilarial densities in both the treated groups were significantly much lower than those of untreated group in contrast to standard filaricide diethylcarbamazine which exerted 79% microfilaricidal action on day 8 of treatment. Both these extracts also demonstrated adulticidal (macrofilaricidal) activity which was more pronounced in the chloroform fraction (50.2%). In addition, there was moderate adverse effect on the reproductive potential of female worms (crude extract 46.5%; chloroform 58.6%). The findings suggest that the marine sponge H. exigua possesses adulticidal and embryostatic action against human lymphatic filarial parasite B. malayi in experimental rodent model and this activity could be attributed to the presence of araguspongin C.

The discovery of the endosymbiont Wolbachia, which has a mutualistic relationship with filarial nematodes, and its importance in filarial parasite biology has provided a lead for developing novel chemotherapeutic agents against human filariasis. Wolbachia also appears to be involved in immunopathological responses as well as adverse reactions after antifilarial therapy. The aim of the present study was to explore the potential of administering anti-Wolbachial therapy before antifilarial treatment to improve the filaricidal efficacy of the present-day filaricide diethylcarbamazine. An additional objective was to minimize host inflammatory reactions using a rodent model Mastomys coucha and Meriones unguiculatus infected with human lymphatic filariid Brugia malayi. We observed: (1) a 40-day treatment schedule of tetracycline alone resulted in delayed reduction in microfilaraemia and a low degree of macrofilaricidal efficacy; (2) tetracycline therapy followed by 100 mg/kg diethylcarbamazine (DEC) x5 days led to marked reduction in microfilaraemia from day 48 onward after initiation of treatment. The combination treatment also brought about approximately 70% death of adult B. malayi and sterilization of 82.3% of the surviving female worms, thus exhibiting remarkable enhancement in the antifilarial activity of DEC; (3) tissue inflammatory reactions and pathogenesis were significantly reduced as observed by histopathology, and peritoneal macrophage mediated oxidative burst shown by fluorescence-activated cell sorting (FACS) analysis using dichlorofluorescein diacetate (DCF-DA); and (4) the characteristic filarial antigen-specific and mitogen-specific cellular unresponsiveness was significantly reversed, possibly due to marked clearance of microfilaraemia. It is therefore advisable to give an anti-Wolbachial antibiotic trial before starting antifilarial therapy to achieve maximum benefits.

Lymphatic filariasis continues to be a major health problem in tropical and subtropical countries. A macrofilaricidal agent capable of eliminating adult filarial parasites is urgently needed. In the present study, we report the antifilarial activity in the extract of stem portion of the plant Lantana camara. The crude extract at 1 g/kg for 5 days by oral route killed 43.05% of the adult Brugia malayi parasites and sterilized 76% of surviving female worms in the rodent model Mastomys coucha. A 34.5% adulticidal activity along with sterilization of 66% of female worms could be demonstrated in the chloroform fraction. Remarkable antifilarial activity was observed in the adult B. malayi transplanted gerbil model where up to 80% of the adult worms could be killed at the same dose and all the surviving female parasites were found sterilized. The extract was also found effective against a subcutaneous rodent filariid Acanthocheilonema viteae maintained in Mastomys coucha, where it exerted strong microfilaricidal (95.04%) and sterilization (60.66%) efficacy with mild macrofilaricidal action. Two compounds, oleanonic acid and oleanolic acid, isolated from hexane and chloroform fractions showed LC100 at 31.25 and 62.5 mug/ml, respectively, on B. malayi in vitro. This is the first ever report on the antifilarial efficacy of Lantana camara.

The antifilarial activity of two coumarin derivatives (A, B) and three glycosyl amine derivatives (D, E, F) was evaluated against a subperiodic strain of human lymphatic filarial parasite Brugia malayi by the intraperitoneal route at 50 mg/kg for 5 consecutive days. Of these, the two sugar derivatives (D and E) were selected for evaluation by the oral route based on their microfilaricidal (mild), macrofilaricidal and female worm sterilization efficacy using the i.p. route of administration. Compound E was finally selected for combination therapy on the basis of its microfilaricidal and embryostatic action by the oral route and its spectrum of activity against micro- and macrofilariae including embryostatic activity by the i.p. route. In addition, E also significantly inhibited the parasite DNA topoisomerase II. Compound A, in contrast, led to an enhanced adult worm burden. Compound B was toxic by the i.p. route, killing all of the treated animals before completion of the experiment. Some of these compounds demonstrated significant antifilarial efficacy of varying degree when tested in vitro Compounds B, D and F also killed adult B. malayi in vitro at 100 muM while 50 muM resulted in very slow motility of worms. Compound E in combination with a promising macrofilaricidal benzopyran derivative reported by us recently (compound C) did not show any synergistic or additive effect. These two compounds (C and E) individually on oral administration with either DEC or ivermectin significantly improved microfilaricidal efficacy in terms of intensity and duration of suppressed microfilaraemia. The combination of DEC with compound E demonstrated marginal enhancement in adulticidal efficacy, however, the embryostatic effect of the duo was significantly higher than that exerted by the individual agents. It may thus be inferred that in the absence of an adulticidal antifilarial drug, the use of potential antifilarials in combination with the standard filaricides may yield better results.

The antifilarial activity of the marine red alga Botryocladia leptopoda against rodent and human lymphatic filarial parasites is described. The animal filarial species included Litomosoides sigmodontis and Acanthocheilonema viteae maintained in cotton rats and Mastomys coucha, respectively, while a subperiodic strain of the human lymphatic filarial parasite Brugia malayi was maintained in M. coucha. The crude extract and its hexane fraction brought about a marked reduction in the peripheral microfilarial level in both of the rodent filarial parasites L. sigmodontis and A. viteae. The microfilaricidal effect began slowly from day 8 or 15 after initiation of treatment and increased with time with a very high efficacy at the end of the observation period against both rodent filariids. The microfilaricidal efficacy was, however, not as prominent in the case of B. malayi. The antifilarial activity, which occurred in the hexane fraction, exerted action at a much lower dose. The product killed a significant proportion of A. viteae and L. sigmodontis adult parasites. In the case of B. malayi, although the macrofilaricidal efficacy was much less than that of the rodent parasites, it (hexane fraction) caused sterilization of a significant proportion of the surviving female parasites. The present findings indicate the possibility of developing an adulticidal and female sterilizing agent against filarial parasites from a marine red alga.

The chloroform methanol (1:1) extract of an unidentified green zoanthus (Phylum Coelenterata, Class Anthozoa) showed promising in vitro adulticidal activity with a lethal concentration of 125 microg/ml on Brugia malayi. This extract brought about a 52.2% reduction in circulating microfilariae of B. malayi when administered to infected Mastomys coucha at 250 mg/kg, orally for 5 consecutive days. Further fractionation of the extract led to the recovery of four fractions, which were evaluated simultaneously in both in vitro and in vivo systems against B. malayi. The chloroform fraction at 250 mg/kg orally for 5 days exhibited the highest macrofilaricidal action (42.5%), closely followed by the insoluble n-butanol fraction (34.3%), the soluble hexane fraction (32.4%), and the soluble n-butanol fraction (20.4%). In addition, the hexane soluble fraction caused 44.3% sterilization of the surviving female parasites. Two compounds isolated were found devoid of antifilarial activity., (Copyright 2004 Springer-Verlag)

A compound of the coumarin class, 4-methyl-7-(tetradecanoyl)-2H-1-benzopyran-2-one, was evaluated for antifilarial activity against the human filarial parasite, Brugia malayi (sub-periodic strain) in Mastomys coucha. The test compound brought about a 24.4% reduction in circulating microfilaremia on day 8 after initiation of treatment when administered by the peritoneal route at a dose of 50 mg/kg for 5 consecutive days. The compound also caused a 62.0% mortality in adult parasites. Apart from killing adult filariids, it also brought about sterilization of 81.8% of the surviving female B. malayi. An oral dose of 200 mg/kg for 5 consecutive days was less effective (35.5% adulticidal efficacy and 65.8% sterilization). In vitro, the compound killed adult B. malayi at 100 microM concentration and inhibited DNA topoisomerase II activity in the filarial parasite. Studies are in progress using the compound in combination with standard antifilarials as well as other active agents.