First record of Acanthocheilonema dracunculoides from domestic dogs in Namibia.

Acanthocheilonema dracunculoides was diagnosed in 2 dogs from Windhoek, Namibia, by acid phosphatase staining of microfilariae. This is the 1st record of A. dracunculoides in Namibia.

Potent 1,3-disubstituted-9H-pyrido[3,4-b]indoles as new lead compounds in antifilarial chemotherapy.

Substituted 9H-pyrido[3,4-b]indoles (beta-carbolines), identified in our laboratory as potential pharmacophores for designing macrofilaricidal agents, have been explored further for identifying the pharmacophore responsible for the high order of adulticidal activity. This has led to syntheses and macrofilaricidal evaluations of a number of 1-aryl-9H-pyrido[3,4-b]indole-3-carboxylate derivatives (3-7). The macrofilaricidal activity was initially evaluated in vivo against Acanthoeilonema viteae. Among all the synthesized compounds, only 12 compounds, namely 3a, 3c, 3d, 3f, 4c, 4d, 4f, 5a, 6f, 6h, 6i, and 7h, have exhibited either >90% micro- or macrofilaricidal activity or sterlization of female worms. These compounds have also been screened against Litomosoides carinii, and of these only 3f and 5a have also been found to be active. Finally these two compounds have been evaluated against Brugia malayi. The structure-activity relationship (SAR) associated with position 1 and 3 substituents in beta-carbolines has been discussed. It has been observed that the presence of a carbomethoxy at position 3 and an aryl substituent at position 1 in beta-carbolines effectively enhances antifilarial activity particularly against A. viteae. Among the various compounds screened, methyl 1-(4-methylphenyl)-9H-pyrido[3,4-b]indole-3-carboxylate (4c) has shown the highest adulticidal activity and methyl 1-(4-chlorophenyl)-1,2,3,4-tetrahydro-9H-pyrido[3, 4-b]indole-3-carboxylate (3a) has shown the highest microfilaricidal action against A. viteae at 50 mg/kg x 5 days (ip). Another derivative of this compound, namely 1-(4-chlorophenyl)-3-(hydroxymethyl)-9H-pyrido[3,4-b]indole (5a), exhibited the highest activity against L. carinii at 30 mg/kg x 5 days (ip) and against B. malayiat 50 mg/kg x 5 days (ip) or at 200 mg/kg x 5 days (po).

Synthesis and anthelmintic activity of 5(6)-(benzimidazol-2-ylcarbamoyl) and (4-substituted piperazin-1-yl)benzimidazoles.

The synthesis of alkyl 5(6)-(benzimidazol-2-ylcarbamoyl)benzimidazole-2-carbamates (6, 7), and alkyl 5(6)-(4-substituted piperazin-1-yl)benzimidazole-2-carbamates (31-40) has been carried out. When the compounds were tested for their anthelmintic activity against Ancylostoma ceylanicum in hamsters, Hymenolepis nana in rats, Litomosoides carinii in cotton rats, and Dipetalonema viteae in Mastomys natalensis, methyl 5(6)-(4-benzoylpiperazin-1-yl)benzimidazole-2-carbamate (31), methyl 5(6)-[4-(2-furoyl)piperazin-1-yl]benzimidazole-2-carbamate and methyl 5(6)-[4-[(diethylamino)carbonyl]piperazin-1-yl]benzimidazole- -2-carbamate (36) showed 100% elimination of tapeworms H. nana at three oral doses of 100-250 mg/kg. Compounds 34 and 36 also killed the microfilariae and adult worms of L. carinii in cotton rats at an intraperitoneal dose of 30 mg/kg given for 5 days.

Structure-activity relationships of antifilarial antimycin analogues: a multivariate pattern recognition study.

The structure-activity relationships of a series of novel antifilarial antimycin A1 analogues have been investigated by using computational chemistry and multivariate statistical techniques. The physiochemical descriptors calculated in this way contained information which was useful in the classification of compounds according to their in vitro antifilarial activity. This approach generated a 53 parameter descriptor set, which was reduced with a multivariate pattern recognition package, ARTHUR. Regression analysis of the reduced set yielded several statistically significant regression equations; e.g.-log in vitro activity = 0.017 mp + 0.65 log P - 0.81ESDL10-7.33 (R = 0.9). With use of this equation, it was possible to make predictions for further untested analogues. The analysis indicated that membrane or lipid solubility is an important determinant in biological activity agreeing with the proposed primary mode of action of the compounds as disrupters of cuticular glucose uptake.

Effect of 2,2'-dicarbomethoxylamino-5,5'-dibenzimidazolyl ketone on antioxidant defenses of Acanthocheilonema viteae and its laboratory host Mastomys natalensis.

The effect of the macrofilaricidal agent of 2,2'-dicarbomethoxylamino-5,5'-dibenzimidazolyl ketone (C.D.R.I. compound 82/437), on the metabolism of reactive oxygen species (ROs) in Acanthocheilonema viteae and Mastomys natalensis was measured following intraperitoneal administration at therapeutic doses. The recovered worms possessed substantially reduced levels of catalase and glutathione peroxidase (GPx), and thus were less able to detoxify H2O2. Nonetheless, the subcutaneous and adjoining muscle tissues, in which the parasites were lodged, exhibited elevated levels of antioxidant enzymes and reduced glutathione. It is concluded that compound 82/437 kills the filariid by paralysing its H2O2 detoxifying capacity without altering ROs metabolism in the tissue in which the parasite resides. Furthermore, since catalase and GPx of the liver and lungs do not show sign of inhibition, a difference appears to exist in the enzymes of the parasite and the host.

Streptocerciasis: degeneration of adult Dipetalonema streptocerca in man following diethylcarbamazine therapy.

Thirty-three patients in Zaire with streptocerciasis were treated daily with diethylcarbamazine (DEC) for 21 days. Histopathologic studies of biopsy specimens with papules of skin established that during DEC treatment adult male and female Dipetalonema streptocerca die and degenerate. DEC may thus produce radical cures of streptocerciasis.

Filariasis testing in a jird model: new drug leads from some old standbys.

A total of 65 compounds, most of which were from chemical classes having members known to be active against one or more parasitic organisms, were evaluated against Brugia pahangi and Acanthocheilonema viteae for macrofilaricidal activity in male Mongolian jirds (Meriones unguiculatus). Sixteen of the 65 compounds tested suppressed the number of parasites. Of these 16, three were suppressive for B. pahangi, 10 for A. viteae, and three for both parasites. The antibiotic nigericin and the antihistaminic isothipendyl were found to be most active.

Immune response in a symptomatic case of Tetrapetalonema perstans infection.

The immune response in a 49-year-old Italian nun affected by Tetrapetalomena (Dipetalonema) perstans following an eight-year stay in Cameroon is reported. On admission the patient presented with polyarthralgia, conjunctival pruritus and irritation, oedema of the limbs, generalized itching, hypereosinophilia and low total IgE titre. During diethylcarbamazine treatment and, subsequently, during mebendazole administration, an exacerbation of her symptoms was observed. At the same time, activation of the alternative complement pathway and the appearance of circulating immune complexes were noted, suggesting a type III hypersensitivity reaction. Circulating immune complexes and diethylcarbamazine-induced release of parasitic antigens may also be considered responsible for the decrease of OKT3 and OKT4 positive lymphocytes.

Filaricidal effects of cyclosporin-A against Dipetalonema viteae in Mastomys natalensis.

Outbred male Mastomys natalensis were injected subcutaneously with 100 infective larvae of Dipetalonema viteae obtained from Ornithodorus tartakovskyi. Groups of five animals were treated with 30 mg/kg of the immunosuppressive drug Cyclosporin-A daily for five days (experimental) or Miglyol 812 (control). One group served as untreated controls. Contrary to expectations, 60% of the animals were completely protected against D. viteae and the remainder were partially protected. The mechanism remains unknown.

Alteration of amicrofilaremia in Dipetalonema viteae infected hamsters with immunosuppressive drugs.

Dipetalonema viteae-infected hamsters with amicrofilaremic infections were subjected to immunosuppressive therapy. Methyl prednisolone acetate caused the most severe recrudescence of microfilariae while cyclophosphamide caused a low level, transient microfilaremia. Saline injected control hamsters remained amicrofilaremic. Neither drug influenced the number of adult worms recovered at necropsy in the treated hamsters compared with control hamsters.

Experimental chemotherapy of filariasis: comparative evaluation of the efficacy of filaricidal compounds in Mastomys coucha infected with Litomosoides carinii, Acanthocheilonema viteae, Brugia malayi and B. pahangi.

Eleven types/classes of compound with antifilarial activity were comparatively evaluated in Mastomys coucha infected with Litomosoides carinii, Acanthocheilonema viteae, Brugia malayi or B. pahangi. The paper deals with the efficacy of (i) predominantly microfilaricidal compounds [diethylcarbamazine, levamisole, avermectins (ivermectin, milbemycin), nitrofurans (nitrofurantoin, hydroxymethylnitrofurantoin, nifurtimox, furazolidone, furapyrimidone), organophosphorals (metrifonate, haloxon), and aminophenyl-amidines], (ii) predominantly macrofilaricidal compounds [suramin, benzimidazoles (flubendazole, mebendazole, oxfendazole, ciclobendazole, albendazole, cambendazole, fenbendazole), and arsenicals (thiacetarsamide, Mel PH, R7/45)], and (iii) micro- and macrofilaricidal compounds [benzazole derivatives (CGP 20376 and other benzothiazoles) and nitrophenylamines (amoscanate, CGP 6140)]. Minimum effective doses against microfilariae and minimum curative doses against adult filariae as well as detailed data on dose-efficacy relationships are reported for the various drugs. The results obtained in M. coucha are compared with those published for other experimental in vivo filarial systems, thus attempting to describe a general status of in vivo antifilarial activity of the compounds.

Antifilarial activity of some 2H-1-benzopyran-2-ones (coumarins).

Six synthetic 2H-1-benzopyran-2-one (cournarin) derivatives (CDRI compounds # 1, 2, 3, 4, 5 and 6) were evaluated for filaricidal activity against Litomosoides carinii and Acanthocheilonema viteae infections in cotton rats (Sigmodon hispidus) and Mastomys coucha respectively. Significant effects on macrofilariae (>80% death/sterilisation) were detected with compounds #2, 3 and 6 against L. carinii and/or A. viteae. Thus detection of filaricidal activity in benzopyrones, which are so far known for anti-inflammatory activity, provides a new lead for development of better filaricidal agents for combating filariasis.

Development of in vitro screening system for assessment of antifilarial activity of compounds.

Evaluation of antifilarial activity of new potential agents in vivo is extremely time consuming and uneconomic. In the present study effort has been made to develop an in vitro screening method using Acanthocheilonema viteae, a subcutaneously dwelling rodent filariid with anaerobic metabolic characteristics like human filariids, W. Bancrofti/Brugia malayi as test parasite. Motility test and tetrazolium (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, MTT) based colorimetric assay were used as parameters in in vitro assay. Results showed that 92.3% of compounds (in vivo active) could be picked up in the in vitro assay when both adults and microfilarae (mf) were used simultaneously. Mf and adult stages separately detected, respectively, 84.6 and 69.2% of in vivo active compounds. The adults and mf separately and both the life stages together exhibited, respectively, 80.0, 50.0 and 80.0% false positive results in the in vitro test with in vivo inactive compounds. It is felt that mf stage when used in in vitro test using motility and MTT assays as parameters would be useful in primary screening of new potential filaricides.

Effects of Bay 44-4400, a new cyclodepsipeptide, on developing stages of filariae (Acanthocheilonema viteae, Brugia malayi, Litomosoides sigmodontis) in the rodent Mastomys coucha.

Bay 44-4400 was used as a spot on formulation and administered in single doses of 25 and 100 mg/kg to Acanthocheilonema viteae, Brugia malayi, and Litomosoides sigmodontis infected Mastomys coucha on various dates during prepatency, aiming to affect third stage larvae, fourth stage larvae or preadult worms. Microfilaraemia levels were controlled in comparison to untreated controls until necropsies were performed 100 days p.i. (A. viteae, L. sigmodontis) and 150 days p.i. (B. malayi) to determine the numbers of surviving worms and the condition of intrauterine developing stages. A significant proportion (86-100%) of larval and preadult stages of A. viteae were killed by Bay 44-4400 at a dose of 100 mg/kg. A dose of 25 mg/kg had only insignificant effects on the developing parasites, however, it strongly reduced microfilaraemia levels caused by surviving worms in the early phase of patency. Larval and preadult B. malayi and L. sigmodontis were not killed by Bay 44-4400 to a significant degree. Microfilaraemia developing by surviving parasites was generally and significantly reduced throughout the observation period when treatment was performed to affect the preadult parasites. In the other cases variable results were obtained. Intrauterine early embryonic stages were found to be pathologically altered in worms which had been treated at a preadult stage.

Effects of 2-deoxy-D-glucose on Acanthocheilonema viteae: rodent filariids as studied by multinuclear NMR spectroscopyt.

A well known glucose antimetabolite, 2-deoxy glucose (2DG) widely used in chemotherapy of cancer along with radiation, was evaluated as an antifilarial agent by nuclear magnetic resonance. The uptake and metabolism of 2DG in the experimental filarial infection Acanthocheilonema viteae was studied by in vivo multinuclear NMR. An unusually long retention time of 2DG6P within these parasites was observed on continuous 31P NMR monitoring, along with a decrease in ATP levels. These results led to therapeutic investigation in A. viteae infected host Mastomys coucha. 2DG showed a remarkable adulticidal activity (73.6%) with 50% sterilization of surviving female worms at a dose of 250 mg/kg x 5, p.o. NMR observations and activity profile substantiate the findings of one another, directed towards the hitting of bioenergetic machinery of A. viteae by macrofilaricidal agent (2DG).