Willie L. Chapman

Improved therapy of experimental leishmaniasis by use of a liposome-encapsulated antimonial drug

Abstract The anti-leishmanial antimonial drug meglumine antimoniate (Glucantime ®) was incorporated into liposomes, and was tested for effects against experimental leishmanial infection in hamsters. When the hamsters had been infected for a short period before treatment (3 days), treatment doses of 416 mg/kg of free meglumine antimoniate, or 4 mg/kg of liposome-encapsulated drug, each gave 99.8% suppression of parasites. After 10 or 17 days of infection prior to treatment liposome-encapsulated compound was more than 300 times as effective as the antimonial drug alone. Use of liposomes containing appropriate drugs is proposed as a markedly superior means to treat certain chronic intracellular parasitic infections.

Liposomes in leishmaniasis: Therapeutic effects of antimonial drugs, 8-aminoquinolines, and tetracycline

Abstract This study investigated the role of liposomes in changing the pharmacological efficacy of anti-leishmanial drugs in hamsters infected with visceral leishmaniasis. Enhanced anti-leishmanial activity could be accounted for only by liposome-encapsulated drugs. “Empty” liposomes (lacking anti-leishmanial drug) gave no therapeutic benefit by themselves, nor did they enhance the effectiveness of concurrently administered drugs. In the absence of additional drugs, empty liposomes actually resulted in a higher mortality due to endstage leishmaniasis. Mortality associated with chronic leishmaniasis, including that induced by empty liposomes, was reduced approximately 50% by orally administered unencapsulated tetracycline. Liposome-encapsulated tetracycline, given i.c., had no anti-leishmanial activity, thus indicating that tetracycline did not have inherent anti-leishmanial properties, and was beneficial because of its anti-bacterial effects. Liposomes containing an antimonial drug were effective when given i.c., i.p., or i.m., but not when given s.c. or p.o. Liposome-encapsulated antimonial drug had prophylactic activity and was effective when administered 8 days prior, but not 17 days prior, to infection. Unencapsulated antimonial drug had no prophylactic effect. In addition to antimonials, another class of compounds, 8-aminoquinolines, had marked anti-leishmanial activity in liposomes. One of these, WR 6026, was 700 to 1800 times more effective than an antimonial drug alone.

Liposomes in leishmaniasis: effects of parasite virulence on treatment of experimental leishmaniasis in hamsters

During studies on the use of liposomes as drug carriers in experimental leishmaniasis in hamsters, we noted incidentally that the apparent virulence of the infection often varied widely between different large groups of animals. When the death rates among control animals (injected only with saline) were compared with hepatic parasite counts of survivors in the same group, three distinctive types of infection were observed: type I, low death rate, low parasite count in survivors; type II, high death rate, low parasite count in survivors; type III, high death rate, high parasite count in survivors. The apparent virulence, based on death rates both at early and late stages of infection, was in the order I less than II less than III. Therapeutic efficacy of a drug (meglumine antimoniate) or liposome-encapsulated drug against each type of infection was in the order I greater than II greater than III. Liposomes reduced the drug dose required for each infection type many hundred-fold and reduced the death rate for type I to zero. However, among animals with type III (or even type II) infection certain individuals were completely refractory to treatment, even when liposome-encapsulated drug was employed, and the lowest mortality rate achieved was approximately 30%. This latter resistance to treatment may have been due to irreversible tissue damage caused by advanced disease, or it may have reflected resistance of certain virulent infections to treatment.

Leishmania donovani: Cellular and humoral immune responses after primary and challenge infections in squirrel monkeys, Saimiri sciureus

Cellular and humoral immune responses were studied in squirrel monkeys after primary and challenge infection with a Khartoum strain (WR 378) of Leishmania donovani. Each of 7 squirrel monkeys, Saimiri sciureus, was inoculated intravenously with 5 X 10(7) amastigotes/kg body weight, and one other monkey (control) was inoculated with uninfected hamster spleen homogenate. Five infected monkeys recovered from visceral leishmaniasis and two infected monkeys died. Three of the five squirrel monkeys which recovered from the primary infection demonstrated acquired resistance when challenged with an intravenous inoculation of 1.0 X 10(8) amastigotes of L. donovani/kg of body weight. Each of these same three monkeys, the two remaining monkeys which recovered from the primary infection and an uninfected control monkey, were challenged subsequently with an intradermal injection of 2.2 X 10(7) promastigotes of L. braziliensis panamensis (WR539) and developed cutaneous lesions. The reactivity of peripheral blood leukocytes from infected squirrel monkeys to phytohemagglutinin was depressed 2 to 10 weeks after infection, and the reactivity to concanavalin A was not affected. Data on responses to pokeweed mitogen were inconclusive. Reactivity to leishmanial antigens was detected at 12 weeks after infection, which coincided with a marked decrease or disappearance of parasites in liver imprints. Two of five surviving squirrel monkeys developed weak delayed skin test responses to leishmanin antigens after 23 weeks; the three remaining monkeys were anergic during the primary infection but developed strong delayed skin test responses to leishmanin antigens at 7 weeks after a challenge with L. donovani. All squirrel monkeys inoculated with L. donovani developed a hyperproteinemia, hypergammaglobulinemia, hypoalbuminemia, and a reversal of the albumin/globulin ratio between 4 to 18 weeks after infection. Plasma IgM and IgG levels were increased between 2 to 18 weeks after infection; much of this increase was due to IgG. Class-specific antileishmanial antibodies, with generally low IgM and high IgG titers, reached a maximum after 14 and 16 weeks, respectively. A correlation was observed between concentration of gamma-globulins and plasma IgM and IgG levels, but not gamma-globulin concentrations and maximum titers of class-specific antileishmanial antibodies. Squirrel monkeys challenged with L. donovani again developed hyperproteinemia, hypergammaglobulinemia, and increased concentrations of plasma IgM and IgG which correlated with high titers of IgG class-specific antileishmanial antibody 4 weeks after reinoculation.(ABSTRACT TRUNCATED AT 400 WORDS)

Leishmania braziliensis: Development of primary and satellite lesions in the experimentally infected owl monkey, Aotus trivirgatus

Twelve male and 8 female feral owl monkeys, Aotus trivirgatus, were inoculated intradermally at the dorsal base of the tail with 2 X 10(7) promastigotes (strains WR 128 or WR 539) or 5 X 10(5) amastigotes (strain WR 128) of Leishmania braziliensis panamensis, and the progression and regression of subsequent lesions were examined for up to 13 or 54 weeks after inoculation. Three of these monkeys had been infected previously with L. donovani, had been treated with meglumine antimoniate, and had recovered clinically from visceral leishmaniasis. All monkeys developed a cutaneous nodule at the inoculation site, but the size of the nodule varied (maximum 78 to 326 mm2 between 4 and 16 weeks after inoculation.) The initial nodule became ulcerated after 4 to 8 weeks in 17 of the 20 monkeys, and the ulcers persisted for 4 to 16 weeks until covered by a crust. Primary lesions disappeared by 17 to 52 weeks after inoculation, but satellite lesions, of similar morphology to the primary lesions but smaller, developed after 4 to 21 weeks in 14 of the monkeys. The primary nodule was excised in 4 monkeys at 6 weeks and did not recur nor did satellite lesions subsequently develop. The satellite lesions (median total number of 4, range 1 to 25) were adjacent to or at a maximum distance of 6 cm from the primary lesion, varied in size from 3 to 117 mm2, and persisted for 10 to 37 weeks. At 6 and 8 weeks after inoculation, tissue from the cutaneous leishmanial lesions from five monkeys was excised and examined. The granulomatous leishmanial lesions, located primarily in the dermis and subcutis, consisted of macrophages containing parasites, lymphocytes, plasma cells, and occasionally eosinophils. Satellite lesions at 14 weeks after inoculation were similar grossly and microscopically to the initial nodule. No significant differences were observed between promastigote or amastigote derived infections, between the two strains of L. b. panamensis, or between the course of infection based on the sex, age, karyotype, or country of origin of the owl monkeys. Cutaneous lesions developed when 5 X 10(5) amastigotes of L. b. panamensis (strain WR 128) were inoculated intradermally into the dorsal base of the tail, the upper eyelid, and the thorax of three monkeys. Leishmanial nodules which developed on the thorax regressed rapidly (after 2 to 5 weeks) whereas those on the upper eyelid and at the dorsal base of the tail persisted for 5 to 45 weeks after inoculation.(ABSTRACT TRUNCATED AT 400 WORDS)

The effects of total-body X-irradiation on Trypanosoma cruzi infection (chagas' disease) in mice and rats

SummaryCF1 mice or COBS rats were exposed to a single dose of 300 R total-body X-irradiation at various times during the course of infection with Trypanosoma cruzi. The effect of this dose of X-irradiation on the parasitemia, numbers of tissue parasites, and mortality in young mice and rats was studied. Irradiation of mice and rats 3 days prior to intraperitoneal inoculation of 50000 or 200000 trypomastigotes of a Brazil strain of T. cruzi, respectively, resulted in markedly enhanced numbers of blood and tissue parasites and increased mortality of these hosts. Irradiation of mice late in the acute infection, i.e., when the numbers of blood parasites were decreasing, resulted in a temporary increase in the numbers of blood and tissue parasites. When irradiation was administered to mice after the parasites had disappeared microscopically from the blood, there was no microscopic evidence of a parasitemia during the succeeding 14 days.

Brugia pahangi: histopathological study of golden hamsters.

Abstract Sixteen male hamsters were inoculated subcutaneously with 95 to 150 infective larvae of B. pahangi and were examined for histopathologic lesions at 39–109 days postinfection. The basic microscopic lesion observed was obstructive granulomatous lymphangitis. Analogous lymph node changes sometimes occurred along with lymphoreticular hyperplasia and increased numbers of eosinophils. Cellular infiltration of perivascular and perinodal tissues was common, with plasma cells and eosinophils predominating. Genital lesions included funiculitis, epididymitis, and mild orchitis. Live and dead worms were found in the testicular parenchyma. Pulmonary changes in hamsters infected more than 105 days included multiple small, granulomatous foci and periarteriolar, peribronchiolar, and subpleural cellular accumulations of plasma cells and eosinophils. Granulomatous obstruction of pulmonary arteries associated with dead worms was observed in two hamsters infected for 39–45 days and in one hamster infected for 109 days. Small liver granulomas were common. Disintegrating microfilariae occurred within giant cells in the lymph nodes, spleen, lungs, and testes.

Leishmania braziliensis: Effects of bacteria (Staphylococcus aureus and Pasteurella multocida) on the developing cutaneous leishmaniasis lesion in the golden hamster

Experimentally induced lesions of cutaneous leishmaniasis and the effect of concurrent bacterial infection on the development of these lesions were studied in the golden hamster. Male outbred golden hamsters received intradermal injections at the base of the tail with approximately 10(7) promastigotes of Leishmania braziliensis panamensis, or promastigotes combined with Staphylococcus aureus or Pasteurella multocida or both, bacteria only, or sterile Eagles minimal essential medium (MEME). The size of the resulting lesions was measured at least twice each week. Hamsters were killed at postinoculation Days 6, 13, 20, 27, 41, or 48, and each lesion was measured, aseptically excised, and bisected; half was used for bacteriologic culture and the other half was prepared for light microscopic examination. Lesions resulting from L. b. panamensis alone progressed from initial erythema to a granulomatous nodule and finally to a necrotic granuloma, often capped by a crateriform ulcer. Lesions resulting from a suspension of L. b. panamensis with added S. aureus or S. aureus and P. multocida, were initially larger, more erythemic and contained a greater proportion of neutrophils up to postinoculation Days 14-21 than did lesions resulting from L. b. panamensis alone. Concurrent infections with bacteria such as S. aureus and P. multocida had little effect on the development of ulcerating characteristics of lesions, but when S. aureus was present it appeared to enhance the severity of the early lesions. Between postinoculation Days 14-28, lesions produced by L. b. panamensis, with or without added bacteria had similar developmental progression of sufficient size for optimal testing of antileishmanial compounds.