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.

Lethal LPS-independent side effects after microfilaricidal treatment in Acanthocheilonema viteae-infected rodents.

Mastomys coucha and jirds infected with Acanthocheilonema viteae, a filarial species free of endosymbiontic bacteria of the genus Wolbachia, suffer lethal side effects after effective microfilaricidal therapy with diethylcarbamazine and levamisole, whereas, M. coucha infected with the Wolbachia-infested species Brugia malayi or Litomosoides carinii tolerate corresponding treatment. Mortality in A. viteae infected, treated animals varied with microfilariae density in the blood. It was up to 100% in highly microfilaraemic M. coucha and jirds, but low or absent in animals with low microfilariae counts. Deaths occurred in most cases 5-24 h after treatment. Characteristic symptoms in animals, which died subsequently were a rapid drop in body temperature by 4-7 degrees C, an increase in hematokrit values by up to 10% and a moderate blood acidosis. Lethal effects in A. viteae infections did not depend on a particular status of hypersensitivity of the animals since desensitization procedures, which protected infected M. coucha against an otherwise lethal intravenous challenge with A. viteae homogenate did not protect against adverse reactions to a subsequent microfilaricidal treatment. The animals were protected from treatment induced death by injection of N-LMMA. Thus the final morbific agent seems NO. The data show that adverse effects after effective microfilaricidal therapy may be caused by microfilariae derived components different from Wolbachia-released LPS.

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).

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.

Syntheses and antifilarial profile of 7-chloro-4-(substituted amino) quinolines: a new class of antifilarial agents.

The syntheses of 7-chloro-4-(substituted amino) quinolines (2-22) and their antifilarial activities are delineated. Some of the screened compounds have shown promising filarial response and sterilization effect on female Acanthocheilonema viteae in rodents.

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 pharmacophore for designing macrofilaricidal agents, have been explored further for identifying the pharmacophore responsible for 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 macrofilarical activity was initially evaluated in vivo against Acanthoeilonema viteae. Amongst all the synthesized compounds, only twelve compounds namely 3a, 3c, 3d, 3f, 4c, 4d, 4f, 5a, 6f, 6h, 6i and 7h have exhibited either > 90% micro- or macrofilaricidal activity or sterilization 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 have been discussed. It has been observed that the presence of carbomethoxy at position-3 and an aryl substituent at position- in beta-carbolines effectively enhance antifilarial activity particularly against A. viteae. Amongst the various compounds screened, methyl 1-(4-methylphenyl)-9H-pyrido[3,4-b]indole-3-carboxylate (4c) has shown highest adulticidal activity and methyl 1-(4-chlorophenyl)-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole-3-carboxyla te (3a) has shown highest microfilaricidal action against A. viteae at 50 mg/ kg x 5 days (i.p.). Another derivative of this compound namely 1-(4-chlorophenyl)-3-hydroxymethyl-9H-pyrido[3,4-b]indole (5a) exhibited highest activity against L. carinii at 30 mg/kg x 5 days (i.p.) and against B. malayi at 50 mg/kg x 5 days (i.p.) or at 200 mg/kg x 5 days (p.o.).

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).

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.

Antifilarial activity of a synthetic marine alkaloid, aplysinopsin (CDRI Compound 92/138).

CDRI Compound 92/138, a synthetic analogue of aplysinopsin, was evaluated in experimental filarial infections, Litomosoides carinii in cotton rats (Sigmodon hispidus) and Acanthocheilonema viteae in Mastomys coucha. The compound killed 63.8 and 90% of adult L. carinii and A. viteae at doses of 30 and 50 mg/kg (i.p.) respectively given for 5 days. By the oral route, at 100 mg/kg for 5 days the compound caused 50.9 and 57% mortality of adult L. carinii and A. viteae, respectively. At 200 mg/kg administered orally on days 0, 10 and 25 post-infection, it reduced establishment of adult A. viteae by 68.5%. We also found 43.7 and 37.8% effect in vivo respectively on L3 and L4 stages of A. viteae at a single dose of 250 mg/kg, p.o. The compound was active in vitro at 100 micrograms/ml concentration and caused a significant decline in MTT reduction and 14C-glucose uptake by adult filariids. Thus synthetic marine aplysinopsin could provide a new pharmacophore for the development of antifilarial agents.

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.

Activity of alpha-anilinobenzyl cyanides and 2-methoxycarbonylamino-1-phenylimidazoles, a new class of antifilarial agents.

The activity of alpha-anilinobenzyl cyanides (2a-f), 5-aryl-4,5-dihydro-2-methoxycarbonylamino-1-phenylimidazoles (5a-d) and 2-methoxycarbonylamino-1-phenyl-1,3-diazaspiro[4:5]dec-2-ene (5f) have been tested for their micro- and macrofilaricidal activity against Litomosoides carinii and Acanthocheilonema viteae in rodents. In this test alpha-anilinobenzyl cyanides (2a-b), 5-(4-methoxyphenyl)-4,5-dihydro-2-methoxy-carbonylamino-1-phenylim idazole (5b) and 2-methoxycarbonylamino-1-phenyl-1,3-diazaspiro[4:5]dec-2-ene (5f) were found to possess marked filaricidal activity at doses ranging from 3-100 mg/kg given parenterally or orally for 5 days.

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.

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.

Antifilarial activities of benzazole derivatives. 3. Effects of benzothiazoles on third stage larvae and preadult worms of Acanthocheilonema viteae, Brugia malayi and B. pahangi in Mastomys natalensis.

Ten structurally defined benzothiazoles (5-methyl and the analogous 5-methoxy derivatives) with known macrofilaricidal and microfilaricidal activities were tested for efficacy against third stage larvae and preadult worms in Acanthocheilonema viteae, Brugia malayi, and B. pahangi infected Mastomys natalensis. Drugs were administered in single oral doses of maximally 100 mg/kg. The benzothiazoles were active against the two stages of the three species. Generally the 5-methoxy derivatives displayed slightly higher activity than the 5-methyl compounds. 6-Isothiocyanates (CGP 21306, CGP 20308) and 6-dithiocarbamic-S-(2-carboxyethyl)esters (CGP 21835, CGP 20376) were more active than thiocarbonylamides (CGP 21833, CGP 20309, CGP 26702, CGP 24589). 6-Dithiocarbamic-S-(sulfomethylsodium)esters (CGP 26701, CGP 24588) showed intermediate efficacy. A. viteae was usually slightly more resistant than the Brugia spp. Minimum curative doses (greater than 95% reduction of worms) against the two stages of the various species were either identical or preadult worms were slightly more resistant than third stage larvae. When these curative doses were compared with curative adulticidal doses or effective doses against microfilariae the various doses were very similar and never differed from each other by more than the factor 2.

Effect of ivermectin on filariae of Mastomys natalensis.

The efficacy of ivermectin (Iv) was evaluated against four species of filariae, Litomosoides carinii, Acanthocheilonema viteae, Brugia pahangi and Brugia malayi in Mastomys natalensis. Animals with patent infections, induced with L3 larvae, by intravenous (iv) infusion of the respective microfilariae (Mf) (5 x 10(4) Mf per animal) or by intraperitoneal (ip) route (2 x 10(4) Mf per animal) were used in this study. A single dose of Iv (100 micrograms.kg-1) given subcutaneously (sc) to Mastomys infected with L. carinii or A. viteae resulted in the disappearance of microfilaremia within 2 h of treatment. Iv treatment of sc-infected animals with Brugia spp. had no immediate effect on the circulating Mf 60 days post-treatment. In contrast, such treatment of animals infected with Mf by intravenous infusion completely eliminated the larvae of all four species from the circulation. Iv treatment had no significant effect on the Mf of L. carinii, B. pahangi and B. malayi in animals infected by the ip route. However, the drug had dramatic effect in killing the Mf of A. viteae in the peritoneal cavity. Sera from Iv-treated normal or from L. carinii- or A. viteae-infected Mastomys were effective in clearing the circulating Mf of the species when administered to animals with the respective infections. Similar rapid clearance of Mf was seen when the sera were administered to animals infected iv with these larvae. Furthermore, adult females of L. carinii and A. viteae recovered from Mastomys on different days after Iv treatment released smaller numbers of Mf in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Antifilarial activities of benzazole derivatives. 2. Microfilaricidal effects against Litomosoides carinii, Acanthocheilonema. vitae, Brugia malayi and B. pahangi in Mastomys natalensis.

The spectrum of antimicrofilarial activities of eighteen 2-tertbutylbenzazole derivatives was evaluated comparatively in Mastomys natalensis infected with Litomosoides carinii, Acanthocheilonema viteae, Brugia malayi or B. pahangi. The minimal effective dose (DEM) against microfilariae (greater than 95% reduction of microfilariae counts in the peripheral blood) was determined on day 3 (DEM-3), on day 7, 14, 21, 28 and 42 (DEM-7, DEM-14, DEM-21, DEM-28 and DEM-42) after the first treatment. All compounds were effective against the microfilariae of all 4 species. The benzoxazole derivatives were invariably less potent than the corresponding benzothiazole analogues. Upon repeated oral treatment (once daily [o.d.] for five days) the DEM-7 of the benzoxazoles varied depending on the species and on the chemical structure between 25 mg/kg o.d. x 5 and greater than 100mg/kg o.d. x 5 days. Within the benzothiazole series the DEM-7 varied between 6.25 mg/kg o.d. x 5 and 100 mg/kg x 5. In all but 5 of the 40 parasite-compound combinations of the benzothiazoles the 5-methoxy-derivates were more effective than the 5-methyl analogues. Similar differences were found with the eight benz-oxazoles tested. The lowest DEM-7 was observed with compound CGP 20308 which is 2-tert-butyl-5-methoxy-6-isothio-cyanatobenzothiazole and with compound CGP 20376 which is 3-(2-tert-butyl-5-methoxy-benzothiazol-6-yl] amino-thiocabo-nylthio) propionic acid.(ABSTRACT TRUNCATED AT 250 WORDS)