In search of anti-Trypanosoma cruzi drugs: new leads from a mouse model.

Nine of 25 carefully selected compounds (from a stock of more than 200 000 chemical species amassed principally as a result of testing against other parasitic diseases) were found to have significant suppressive activity against the parasites in the blood of a Trypanosoma cruzi mouse model. Eight of these compounds evaluated in this model had suppressive activity equal to or greater than the reference compound, nifurtimox. For the first time, suppressive activity against T. cruzi is reported for a 7-aminoquinoline, a phosphonium salt, and TAC pamoate; The biological model is believed to be able to serve as a means of identifying other new "leads* in seeking drugs broadly effective against T=ruzi infections in man.

Blastogenic responses of peripheral blood leukocytes from owl monkeys experimentally infected with Leishmania braziliensis panamensis.

The relationship of the progression and regression of cutaneous lesions of 6 owl monkeys (Aotus trivirgatus) to the responses of their peripheral blood leukocytes (PBL) in vitro to mitogens and to leishmanial antigens, as well as their delayed skin test responses (DTH) in vivo to leishmanin antigen, were studied after primary and challenge infections with Leishmania braziliensis panamensis (WR 128 or WR 539). All 6 infected monkeys developed primary and satellite cutaneous leishmanial lesions which were measured for up to 30 weeks in 3 of the monkeys and up to 52 weeks in the other 3 monkeys. Two owl monkeys which had recovered from cutaneous leishmaniasis demonstrated acquired resistance when challenged with an intradermal inoculation of L. b. panamensis (WR 128). Reactivity of PBL from infected owl monkeys to PHA, Con A, and PWM was similar during primary and challenge infections to that observed prior to infection. Reactivity to leishmanial antigens was detected at 20 to 28 weeks post-infection (PI), became statistically significant after 28 weeks and remained elevated up to 52 weeks PI and after challenge infections. During primary infections DTH responses to leishmanin antigen were detected as early as 8 weeks PI, and continued up to 27 weeks PI. After challenge infections DTH reactivity was positive at 25 and 37 weeks, the only times the response was evaluated. The immunological responses of owl monkeys to L. b. panamensis were similar in many respects to those observed in humans with localized cutaneous leishmaniasis. This nonhuman primate model should be useful for future studies involving the immunology and chemotherapy of cutaneous leishmaniasis.

The antileishmanial activity of lepidines.

A series of lepidines (6-methoxy-4-methyl-8-aminoquinoline derivatives) was studied in a hamster-Leishmania donovani model. Members of this class were found to have activity many-fold that of the standard, meglumine antimoniate (Glucantime). One of them, 8-(6-diethylamino-hexylamino)-6-methoxy-4-methylquinoline, designated WR 6026, when given orally was over 700 times as effective as the standard antimonial drug.

Isolation of Acanthamoeba sp. from a greyhound with pneumonia and granulomatous amebic encephalitis.

Acanthamoeba were isolated from a naturally occurring animal infection of granulomatous amebic encephalitis. The amebas were grown from lung lesions from a 1-year-old greyhound puppy, which was 1 of several dogs in a kennel that was affected by a progressive fatal neurologic and respiratory disease. The Centers for Disease Control, Atlanta, Georgia, confirmed the disease to be acanthamebiasis and specifically identified the amebas as Acanthamoeba culbertsoni by fluorescent antibody testing on brain tissue from the dog. The amebas were cultured initially on potato dextrose agar and on nonnutrient agar plates that were seeded with a lawn of nonpathogenic Escherichia coli. The isolate was then transferred to nonnutrient agar plates containing killed Enterobacter aerogenes and subsequently to axenic medium and cell cultures. The isolate was highly pathogenic by intranasal inoculation into 2-week-old mice.

Canine leishmaniasis caused by Leishmania leishmania infantum in two Labrador retrievers.

Canine leishmaniasis, a generally fatal parasitic disease, was diagnosed in 2 dogs with a medical history of foreign travel, lymphadenopathy, emaciation, anorexia, intermittent fever, and cutaneous lesions. Clinically, hyperproteinemia, proteinuria, azotemia, and glomerulopathy were evident. Isolation of Leishmania species was done using Schneider's Drosophila medium. Syrian hamsters were used for infectivity studies. Clear taxonomic identification was done biochemically by isoenzyme analysis and comparison of zymogram banding patterns with 6 World Health Organization reference strains. Based on the geographic origin of affected dogs, clinicopathologic presentation, visceralization with hepatosplenomegaly in hamsters, and isoenzyme analysis, a diagnosis of Leishmania leishmania infantum was made. This study, representing the first taxonomic identification of an isolate from canine leishmaniasis, demonstrates the zoonotic and epidemiologic implications of this disease.

Intramuscular Sarcocystis sp. in two cats and a dog.

Sarcocystis sp. was diagnosed in the skeletal muscle of a cat and myocardium of a dog and cat. The cysts were similar in size and structure when examined by light and transmission electron microscopy. The 3 animals were debilitated and probably immunocompromised due to pancytopenia or terminal neoplasia.

The influence of gonadectomy of host on parasitemia and mortality of mice infected with Trypanosoma cruzi.

Male CF1 mice were more susceptible to acute infections of Trypanosoma cruzi than female mice as evidenced by significantly greater maximum mean parasitemia of approximately 8.9 times 10-6 per ml in males as compared to 1.5 times 10-6 per ml in females. Mortality was also greater in males (80 to 90% as compared to 28% in females). Ovariectomy of female mice made them more susceptible than unoperated female of similar age and stock to the Brazil strain of T. cruzi as indicated by maximum mean parasitemia of 10.9 times 10-6 per ml in the former and 7.5 times 10-6 in the latter. Mortality of the ovariectomized mice was as great as 90% in some experiments while that of unoperated controls nerve exceeded 30%. Parasitemia and mortality is castrated male mice were not significantly different from unoperated male mice infected with T. cruzi.

Leishmania braziliensis in the squirrel monkey: development of primary and satellite lesions and lack of cross-immunity with Leishmania donovani.

Three female and 2 male adult laboratory-reared squirrel monkeys (Saimiri sciureus) that previously had been inoculated with Leishmania (Leishmania) donovani and had recovered from experimental visceral leishmaniasis were each inoculated intradermally at the dorsal base of the tail with 2.2 x 10(7) culture-derived promastigotes of Leishmania (Viannia) panamensis. The progression and regression of subsequent lesions were examined for 36 wk in all 5 monkeys after which 3 of the monkeys were killed (1 with a primary lesion and all with satellite lesions) and the 2 surviving monkeys (1 with primary lesion and both with satellite lesions) were treated with 104 mg/kg/day of meglumine antimoniate for 10 days. All of the monkeys developed a primary lesions at the site of injection of the parasite and later developed satellite lesions peripheral to the primary nodule. The primary lesions had disappeared from 3 of the 5 monkeys by 36 wk, whereas satellite lesions persisted on all at this time. Satellite lesions were present at 52 wk after treatment and persisted for 169 wk in the 2 surviving monkeys. The histopathologic appearance of the lesions was characterized as granulomatous inflammation. Our results indicated that squirrel monkeys that had recovered from visceral leishmaniasis remained susceptible to infection with L. (V). panamensis.

Chemotherapy of experimental visceral leishmaniasis in the opossum.

Visceral leishmaniasis is a severe chronic disease of people and animals. The disease is caused by several subspecies of a protozoal organism, Leishmania donovani. If not treated, visceral leishmaniasis is often fatal. The most commonly used chemotherapeutic agents to treat the disease are pentavalent antimonials, which can be toxic, must be administered by parenteral routes, and are sometimes ineffective. In this study, meglumine antimoniate, a pentavalent antimony, was compared with WR 6026, an 8-aminoquinoline derivative, as to antileishmanial efficacy. The results indicate that either of these 2 drugs are effective in the suppression of amastigotes in the liver and spleen of the opossum. Despite the marked parasite suppression in the liver and spleen of the infected opossums, the experimental disease was fatal in all of the infected opossums, regardless of the therapy.

Leishmania donovani: clinical, hematologic and hepatic changes in squirrel monkeys (Saimiri sciureus).

Clinical signs, parasite densities, and hematologic and hepatic changes were studied in 7 squirrel monkeys (Saimiri sciureus) each of which was inoculated intravenously with amastigotes (5.0 X 10(7) per kg body weight) of a Khartoum strain (WR 378) of Leishmania donovani. One control monkey was inoculated with uninfected hamster spleen homogenate. Five of the infected monkeys recovered spontaneously from visceral leishmaniasis by 8 to 15 wk postinoculation (wk PI) and 2 of the infected monkeys died at 39 and 59 days PI, respectively. All monkeys inoculated with L. donovani experienced a slight body weight loss, mild but significant anemia, lymphocytosis and an inconsistent neutropenia. Liver parasite densities could be quantitated from liver imprints from 2 to 8 wk PI and reached a maximum mean of 6.3 X 10(7) amastigotes/g liver at 4 wk PI in Experiment 1 and 13.4 X 10(7) amastigotes/g liver at 6 wk PI in Experiment 2. None of the liver imprints contained parasites at 15 wk PI. The characteristic histopathologic findings in liver biopsy and necropsy samples were multiple granulomas consisting of macrophages (some of which contained parasites), lymphocytes and plasma cells. The squirrel monkey is a moderately susceptible host for L. donovani. Squirrel monkey visceral leishmaniasis has a sustained course and certain clinical, hematologic and pathologic characteristics which are similar to human visceral leishmaniasis.

Development of Leishmania (Viannia) panamensis lesions and relationship of numbers of amastigotes to lesion area on antimony-treated and untreated hamsters.

Young adult (60-70-g) male golden hamsters (Mesocricetus auratus) each were injected intradermally at the dorsal base of the tail with 15 x 10(6) promastigotes of Leishmania (Viannia) panamensis (MHOM/PA/83/WR539), and progression and regression of subsequent lesions were evaluated for up to 17 wk postinfection (PI) as to area, weight, and number of amastigotes within lesions in untreated hamsters and in hamsters treated with meglumine antimoniate (Glucantime). In untreated hamsters total area of lesion, weight, and numbers of amastigotes generally increased rapidly and concomitantly up to 3-4 wk PI. Amastigote numbers tended to decrease from 4 to 11 wk PI and subsequently the numbers of amastigotes within the lesions decreased rapidly, whereas relatively little change occurred in the area and weight of the lesions. Meglumine antimoniate treatment of cutaneous hamster lesions resulted in marked concomitant decrease in size of the lesions and numbers of amastigotes within the lesions examined 1 wk after treatment. Measurement of the area of cutaneous leishmanial lesions thus would appear to be a valid method of evaluating the efficacy of promising compounds against L. panamensis in hamsters when measurements are taken 3-5 wk after experimental infection and reflects the number of amastigotes present in the lesion.

Keratoconjunctivitis sicca: histopathologic study of nictitating membrane and lacrimal glands from 28 dogs.

Forty nictitating membrane glands and 9 main lacrimal glands were obtained for histologic evaluation from 28 dogs with keratoconjunctivitis sicca as the result of azosulfapyridine toxicity, canine distemper, multisystemic autoimmune disease (Sjögren's syndrome-like syndrome), congenital origin, and unilateral and bilateral idiopathic keratoconjunctivitis sicca. Similar glands from 6 control dogs were studied. The most prevalent (87%) histopathologic finding was variable degrees of multifocal chronic adenitis, characterized by acinar atrophy and replacement with increased numbers of plasma cells and lymphocytes within increased amounts of interacinar fibrous connective tissue stroma. Occasional tubular structures were dilated and filled with neutrophils and cellular debris.

Determination of virulence and pathogenesis of a canine strain of Leishmania leishmania infantum in hamsters and dogs.

Visceral leishmaniasis was experimentally induced in hamsters by the intracardiac inoculation of 10(7) amastigotes of Leishmania leishmania infantum of canine origin. At postinoculation (PI) days 7, 21, 42, and 63, hamsters were euthanatized. Body weights and total parasite numbers of the liver and spleen were determined. Gross and histologic evaluations of tissues were done. Dogs also were inoculated IV with 10(8) amastigotes/kg of body weight. Samples were obtained from dogs prior to infection and at biweekly PI intervals for CBC and serum chemical analysis, for lymphocyte blastogenic assay by use of blood leukocytes, and for ELISA to determine antileishmanial antibody titers. At PI week 12, dogs were necropsied; organ weights, tissue imprints of the liver and spleen, and histologic interpretations of tissues were obtained. Hamsters developed high parasite numbers within 7 days after inoculation, at which time the total parasite numbers in the liver (3.51 x 10(7) amastigotes) was observed to be approximately 11 times that in the spleen (2.93 x 10(6)). The liver had the highest parasite numbers throughout the infection period. Some infected hamsters became either cachectic and emaciated or ascitic. Two of the 10 infected hamsters died at PI days 54 and 58. Moderate to severe hepatosplenomegaly with granulomatous inflammatory reactions characterized by the presence of varied numbers of parasitized macrophages, giant cells, and hepatic Schaumann bodies were observed in infected hamsters. Infected dogs developed significantly altered hematologic values consisting of mild anemia and moderate leukopenia at PI weeks 8 to 12. Hyperproteinemia characterized by hyperglobulinemia (4.5 g/dl) was noticed at PI week 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Antileishmanial activity of liposome-encapsulated meglumine antimonate in the dog.

Experimental infections of Leishmania donovani in mixed-breed dogs were induced to determine the antileishmanial efficacy of liposome-encapsulated meglumine antimoniate ( LEMA ). Each dog was inoculated IV with 1.0 +/- 0.2 X 10(8) amastigotes of a Khartoum strain of L donovani/kg of body weight. The antileishmanial agents ( LEMA or unencapsulated meglumine antimoniate ) were given once daily, IV, for 1, 4, or 10 consecutive days beginning the 12th day after inoculation. The dogs were killed 3 or 4 days after completion of therapy, and parasites in the spleens were quantified. A single injection of LEMA (0.61 mg of Sb/kg of body weight) resulted in 89% suppression and 4 consecutive daily injections of LEMA (1.94 mg of Sb/kg/day) resulted in 95.8% suppression of splenic parasites. The dose of LEMA that would give 50% suppression ( SD50 ) was estimated as approximately 0.029 mg of Sb/kg. The SD50 for unencapsulated drug was estimated as approximately 24 mg of Sb/kg. The liposome-encapsulated drug was estimated to be more than 700 times more efficacious than the unencapsulated drug. Seemingly, liposomes can markedly reduce the drug dosage required for equivalent treatment of visceral leishmaniasis in dogs.

Occurrence of antibody to Trypanosoma cruzi in dogs in the southeastern United States.

Seven of 365 dogs from Georgia and other southeastern states were seropositive for antibody to Trypanosoma cruzi by the complement-fixation (CF) test. Sera from 24 dogs, including the 7 dogs seropositive by CF test, were reactive at dilutions of 1:128 or 1:256 by the direct-agglutination (DA) test. Dogs with positive CF titers were significantly (P less than 0.05) younger than were the dogs in the total population surveyed. The occurrence of antibody to T cruzi was similar, regardless of the dogs' origin, sex, or length of hair. Dogs with specific antibody to T cruzi did not have clinical signs of disease related to the cardiovascular or gastrointestinal systems, the systems most frequently affected in American trypanosomiasis (Chagas' disease). Sera from an additional 20 dogs from Minnesota were examined by the DA test. One of these sera had a reaction at a dilution of 1:2, and 19 sera had no reaction in the DA test for antibody to T cruzi.

alpha-Difluoromethylornithine: a promising lead for preventive chemotherapy for coccidiosis.

alpha-Difluoromethylornithine (DFMO; RMI 71,782) given in drinking water in concentrations as low as 0.0625% inhibited infections of Eimeria tenella and minimized the development of lesions in chickens. It had approximately the same activity as a currently used anticoccidial drug, amprolium, and also had the advantage of being relatively nontoxic in chickens. Body weight gains were not reduced in chickens given 0.0635% DFMO or less for 14 days starting 8 days before they were inoculated with oocysts, but were reduced in chickens given drinking water containing 0.125 and 0.25% DFMO. The anticoccidial activity of DFMO was completely reversed by injection (intraabdominal) of putrescine hydrochloride (300 mg/kg of body weight/day), indicating that the drug may act by blocking putrescine biosynthesis. Inoculated chickens, in which coccidial lesion development was suppressed by DFMO, resisted subsequent challenge exposure with E tenella, as did nontreated infected control birds which had recovered from infection.

Leishmaniasis: in search of new chemotherapeutic agents.

Members of a class of compounds designated lepidines (8-amino-6-methoxy-4-methylquinoline derivatives) were tested in a hamster-Leishmania donovani model and found to have activity many-fold that of a reference drug meglumine antimoniate. One of them, 8-(7-isopropylaminoheptylamino)-6-methoxy-4-methylquinoline, was found to be 138 times as effective as the standard antimonial drug used.

Amyloidosis in rhesus monkeys with rheumatoid arthritis and enterocolitis.

Generalized amyloidosis was diagnosed by light and electron microscopy in 4 of 5 monkeys (Macaca mulatta) that had a history of chronic arthritis or chronic intermittent diarrhea, or both. Clinical signs and lesions of arthritis in the monkeys were compatible with diagnostic criteria for rheumatoid arthritis. Shigella sp was cultured from 1 monkey, and 2 other monkeys had colonic lesions characteristic of shigellosis. At necropsy, gross changes attributed to amyloid were seen only in the liver. Amyloid deposits in the liver, spleen, mesenteric lymph nodes, kidney, heart, adrenal glands, and other organs were determined by staining reactions and fine structural characteristics.