Antifilarial activity of Caesalpinia bonducella against experimental filarial infections.

BACKGROUND & OBJECTIVE: Lymphatic filariasis is a disabling disease that continues to cripple population in tropical countries. Currently available antifilarial drugs are not able to control the disease. Therefore, a better antifilarial is urgently required for proper management of the disease. We undertook this study to assess the antifilarial activity of Caesalpinia bonducella-seed kernel against rodent filarial parasite in experimental model. METHODS: Microfilaraemic cotton rats and Mastomys coucha harbouring Litomosoides sigmodontis and Brugia malayi respectively, were treated with crude extract or fractions of the seed kernel C. bonducella through oral route for 5 consecutive days. Microfilaricidal, macrofilaricidal and female worm sterilizing efficacy was assessed. RESULTS: Crude extract showed gradual fall in microfilariae (mf) count in L. sigmodontis-cotton rat model from day 8 post-treatment attaining more than 95 per cent fall by the end of observation period. It also exhibited 96 per cent macrofilaricidal and 100 per cent female sterilizing efficacy. The butanol fraction F018 caused 73.7 per cent reduction in mf count and 82.5 per cent mortality in adult worms with 100 per cent female sterilization. The aqueous fraction F019 exerted more than 90 per cent microfilaricidal activity and 100 per cent worm sterilization. Two chromatographic fractions, F024 and F025 of hexane soluble fraction exhibited 64 and 95 per cent macrofilaricidal activity, respectively. Both the fractions caused gradual fall in microfilaraemia and 100 per cent worm sterilization. In B. malayi-M. coucha model F025 showed gradual reduction in microfilaraemia and caused 80 per cent sterilization of female parasites INTERPRETATION & CONCLUSION: In conclusion, C. bonducella- seed kernel extract and fractions showed microfilaricidal, macrofilaricidal and female-sterilizing efficacy against L. sigmodontis and microfilaricidal and female-sterilizing efficacy against B. malayi in animal models, indicating the potential of this plant in providing a lead for new antifilarial drug development.

Transmission of filarial infection through blood transfusion.

Microfilariae can be transmitted by blood transfusion and they may be circulated in the recipient's blood but they do not develop into adult worms. Mortality associated with transfusion associated filarial infection is not documented but it may give rise to morbidity in transfusion recipients in terms of allergic reaction. The present study was carried out to investigate the association of post transfusion reactions and filarial infections in an endemic area. About 11,752 transfusion recipients were followed up and in 15 months period, 47 (0.4%) post transfusion reactions (PTR) were reported. Routine investigations for post transfusion reaction were carried out in all 47 patients and their respective blood donor. Moreover, blood culture, microfilaria detection by concentration technique, filarial antibody and antigen detection (both by ELISA) were done in all subjects. Out of 47 patients showing post transfusion reaction, 29 (61.7%) patients developed allergic reaction. Eighteen (38.3%) patients having allergic reaction did not have previous history of blood transfusion and 14 (29.8%) of them received transfusion from blood donors who was either positive for microfilaria, filarial antigen or antibody. Microfilaremia was demonstrated in 4 (8.5%) patients and 5 (10.6%) blood donors. Microfilaria was concurrently present in 2 patients and their respective donors. Filarial antibody was detected in 27 (56.5%) patients and 26 (55.3%) blood donors but microfilaria was detected in 3 (6.4%) and 4 (8.5%) subjects, respectively. Antigen detection test correlated with microfileraemic state of subjects. The result shows that transfusion associated filarial infection may be a probable cause for transfusion-associated morbidity in endemic areas. In 14 (29.8%) patients having allergic reactions, the probable cause was transfusion-associated filarial infection. Filarial antigen detection test was found to be more useful in detecting infections. Blood donors with active history of filarial infection should be deferred from donating blood. Filarial antigen detection test may be employed as screening test for blood donors, if possible.

Optimization of test conditions for development of MTT as in vitro screen.

The quick and easy method of tetrazolium based colorimetric assay with MTT [3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] was used to test the viability of the adult parasites of a rodent filariid Acanthocheilonema viteae in vitro. The ideal conditions required for antifilarial screening were determined by correlating the MTT reduction ability of worms with their size and age in the vertebrate host, also the duration of incubation and temperature of the in vitro culture. It was observed that the worms collected from the host after 90 days of L3 (infective larvae) exposure were not suitable for in vitro screen as they could not reduce MTT to that extent as the worms of early infection. Healthy and full grown worms and also those incubated at 37 degrees C for 16 hr or more caused maximum MTT reduction. Thus, it is recommended to select healthy adult filariids of proper age and size (male > 3.5 cm; female > 7.0 cm). The incubation temperature of the in vitro culture system needs to be adjusted to 37 degrees C and parasites might be exposed to drugs upto 24 hr without much alteration in MTT reduction of untreated controls.

Carboline antifilarials: effects on carbohydrate metabolising enzymes in Litomosoides carinii female.

Two antifilarial compounds, viz., 90/55 (7-oxo-1-phenyl-8, 14-dihydropyrido (3,4-b) imidazo (1,2-c) quinazolo (4,5-g) and 87/639 (6-Nitro-1-phenyl-9H-pyrido (3,4-b) indole at 0.5 and 2.0 micron concentrations substantially inhibited glucose uptake and increased lactate production by L. carinii during in vitro incubation for 2 hr. The treated parasites, showed increased activities of glycogen phosphorylase, phosphofructokinase and pyruvate kinase. Hexokinase and fumarate reductase activities level in the worms were significantly lowered. Therefore it appears that both the compounds kill adult L. carinii by interfering with its carbohydrate metabolism.

Evaluation of vanillic acid analogues as a new class of antifilarial agents.

A number of vanillic acid analogues (1-14) have been synthesised and evaluated against experimental filarial infections using cotton rats (Sigmodon hispidus) infected with Litomosoides carinii, a primary screening model, at a dose of 30 mg/kg, ip for 5 days. Of the 8 compounds tested, 4 (5,7, 11 and 12) exhibited high micro- and macro-filaricidal activity with sterilization of surviving female worms. Compounds 5, 7, 12 showed remarkable adulticidal action (> 80%). Sterilization of the female worms by compounds 11 and 12 was highly significant (80-100%).

Impact of surface modifications of Acanthocheilonema viteae microfilariae on cell adhesion.

Exposure of A. viteae microfilariae to various lectins reduced their capacity to react with the peritoneal exudate cells of the host, Mastomys natalensis. Sugars corresponding to these lectins with the exception of N-acetyl glucosamine, did not affect the adhesion per se. They however, protected the parasite against the adverse effect of lectins. Neuraminidase and chitinase also suppressed adhesion capacity of the microfilariae. Except sodium dodecylsulphate which enhanced cell attachment, other surfactants inhibited this reaction considerably. The results indicate that antibody dependent adhesion of the microfilariae with the macrophages involves surface moieties of the parasite, where N-acetylglucosamine acts as the principal sugar residue. Participation of -SH groups also is inferred from the observations that p-chloromercuribenzoate and dithiobis-(2-nitrobenzoic acid) inhibited cell attachment and dithiothreitol provided protection against these agents.

Xanthine oxidase, superoxide dismutase, catalase and lipid peroxidation in Mastomys natalensis: effect of Dipetalonema viteae infection.

Status of xanthine oxidase, superoxide dismutase, catalase and lipid peroxidation, the enzymes metabolizing reactive oxygen intermediates in liver, lungs and spleen of M. natalensis during D. viteae infection was investigated. Xanthine oxidase and lipid peroxidation exhibited stimulation, while superoxide dismutase and catalase showed depression in liver and spleen of the infected animals. The filarial infection therefore appears to create O2 toxicity in these tissues. Lungs, on the other hand was found safe as it possessed elevated xanthine oxidase, superoxide dismutase and catalase. Lipid peroxidation in lungs operated below the control level. The impact of these changes in the establishment and development of the infection has been discussed.