Toll like receptor 2 and CC chemokine receptor 5 cluster in the lipid raft enhances the susceptibility of Leishmania donovani infection in macrophages.

In experimental visceral leishmaniasis the causative obligate protozoan parasite, L. donovani invades and multiplies inside of macrophages, one of the sentries of the mammalian immune system. The initial host-parasite interaction between the Leishmania promastigote and the macrophage takes place at the plasma membrane interface. To trace any possible interaction between Toll-like receptor 2 (TLR2) and CC chemokine receptor 5 (CCR5) during early Leishmania-macrophage interactions, it was observed that the expression of both TLR2 and CCR5 were significantly increased, along with their recruitment to the lipid raft. TLR2 silencing attenuates CCR5 expression and restricts L. donovani infection, indicating a regulatory role of TLR2 and CCR5 during infection. Silencing of CCR5 and TLR2 markedly reduced the number of intracellular parasites in macrophages by host protective cytokine responses, while raft disruption using β-MCD affected TLR2/CCR5 cross-talk and resulted in a significant reduction in parasite invasion. In vivo RNA interference of TLR2 and CCR5 using shRNA plasmids rendered protection in Leishmania donovani-infected mice. Thus, this study for the first time demonstrates the importance of TLR2/CCR5 crosstalk as a significant determinant of Leishmania donovani entry in host macrophages.

Antiparasitic activity of plumericin & isoplumericin isolated from Plumeria bicolor against Leishmania donovani.

Background & objectives: The severe toxicity, exorbitant cost and emerging resistance of Leishmania species against most of the currently used drugs underscores the urgent need for the alternative drugs. The present study evaluates in vitro anti-leishmanial activity of Plumeria bicolor and its isolated compounds. Methods: The in vitro anti-parasitic activity of chloroform extract of Plumeria bicolor, plumericin and isoplumericin were tested alongwith appropriate controls against promastigote and amastigote forms of Leishmania donovani using 96 well microtiter plate. The concentration used for assessing the anti-leishmanial activity of extract of Plumeria bicolor and both isolated compounds were 100 μg/ml and 15 μM, respectively. The viability of the cells was assessed by MTT assay. The cytotoxicity of these compounds was performed against J774G8 murine macrophage cells lines at the concentration of 30 μM. Results: The Plumeria bicolor extract showed activity with the IC50 of 21±2.2 and 14±1.6 μg/ml against promastigote and amastigote forms of L. donovani, respectively. Plumericin consistently showed high activity with the IC50 of 3.17±0.12 and 1.41±0.03 μM whereas isoplumericin showed the IC50 of 7.2±0.08 μM and 4.1±0.02 μM against promastigote and amastigote forms, respectively. Cytotoxic effect of the chloroform extract of P. bicolor, plumericin and isoplumericin was evaluated in murine macrophage (J774G8) model with CC50 value of 75±5.3 μg/ml, 20.6±0.5 and 24±0.7 μM, respectively. Interpretation & conclusions: Our results indicated that plumericin showed more potent activity than isoplumericin and might be a promising anti-leishmanial agent against L. donovani.

An overview of paediatric leishmaniasis.

Leishmaniasis, a parasitic disease transmitted by the bite of some species of sandflies affects various age groups depending on the infecting Leishmania species, geographic location, disease reservoir, and host immunocompetence. Visceral leishmaniasis is the most severe form of the disease affecting children. The extent and presentation of the disease depend on several factors, including the humoral and cell-mediated immune response of the host, the virulence of the infecting species, and the parasite burden. Children are at greater risk than adults in endemic areas. Malnutrition contributes to the development of disease, and incomplete therapy of initial disease is a risk factor for recurrence of leishmaniasis. Children usually present with intermittent fever, paleness, refusal to feed or anorexia, weight loss, and abdominal distension. Splenomegaly, hepatomegaly, lymph node enlargement, thrombocytopaenia, anaemia, leukopaenia and hypergammaglobulinemia are the most common findings in Paediatric leishmaniasis. Molecular methods appear to offer the promise of accurate non-invasive tools for the diagnosis of Leishmaniasis. Till these methods are evaluated, definite diagnosis will rely on the demonstration of the infecting parasite in various tissues. World-wide, with the notable exception of India, pentavalent antimonial compounds remain the most effective and the most affordable therapy for this disease. Lipid formulations of amphotericin B were assessed as short duration treatment and were proved to be effective. However, their cost precludes their wide use in developing countries. Miltefosine, a new oral agent, might prove effective, safe, and affordable. Strategies aimed at control of the micro-population of sandflies, eradication of canine leishmaniasis, and offering personal protection against sandfly bites, together with health education programs in developing countries, can help control the disease. Development of an effective vaccine remains a priority.

Visceral leishmaniasis: a study of 73 cases in Ahwaz

Seventy three cases [47 male and 26 female] of Kala azar were diagnosed within 8 years [1983-1990]. 70 patients were under the age of 10 years [95.9%] and 3 were above 10 [4.1%]. The youngest patient was at the age of 5 months and the oldest was 40 years. Diagnosis was based on observation of Leishman bodies in Giemsa stained smears prepared from bone marrow aspiration specimen. All of the patients had hepatosplenomegaly. In 71 patients [95.8%], the hemoglobin level was under 10 mg/100 ml. The haematocrit under 30% was present in 79.4% [58 patients]. 66 [90.4%] patients were leukopenic and 79% showed lymphocytosis. The patients were living in different cities or villages of Khoozestan Province, predominantly from Izeh and Masjedsoleiman cities

Isolation of virulence genes directing GPI synthesis by functional complementation of Leishmania

Recent advances in molecular genetics of Leishmania parasites prompted us to develop methods of functional genetic complementation in Leishmania and apply them to the isolation of genes involved in the biosynthesis of the virulence determinant LPG, an abundant GPI-anchored polysaccharide. LPG1, the gene product identified by complementation of our R2D2 LPG- mutant, may be a glycosyltransferase responsible for the addition of galactofuranose to the nascent chain. As galactofuranose is not found in mammalian cells, inhibition of the addition of this sugar could be exploited for chemotherapy. Overall, the success of the functional complementation approach opens the way to the identification of a variety of genes involved in pathogenesis and parasitism

Comparative study of the biological behaviour in hamster of two isolates of Leishmania characterized respectively as L. major-like and L. donovani

Experimentos utilizando-se hamsters inoculados intraperitonealmente com 1 x 10**7 parasitas de 2 cepas, L. donovani (MHOM/BR/72/LD 46) e L. major-like (MCAN/BR/73/LD 70) isoladas no Novo Mundo foram realizados e estudados em grupos de 15,30,60 e 90 dias e infecçäo. A carga e a densidade parasitária mostraram progressivo aumento com a evoluçäo da infecçäo e foi maior nos grupos inoculados com L. donovani do que nos grupos inoculados com L. major-like. Os grupos inoculados com L. major-like mostraram densidade parasitária maior no baço que no fígado e foram semelhantes em ambos os órgäos nos grupos inoculados com L. donovani. A histopatologia mostrou intensa e difusa hiperplasia e hipertrofia do sistema reticuloendotelial com alto parasitismo nos grupos inoculados com L. donovani, enquanto foi encontrado envolvimento focal nestes órgäos nos grupos inoculados com L. major-like, formando nódulos de macrófagos discretamente parasitados. O comportamento biológico seria útil em estudos preliminares de identificaçäo de cepas de Leishmania em laboratórios regionais e na compreensäo da histopatologia das lesöes causadas por diferentes espécimes de leishmanias