Lys-413 of S-phase mRNA cycling sequence binding protein from Leishmania donovani (LdCSBP) is modified through monoubiquitination that is responsible for inhibition of its riboendonuclease activity.

In addition to well-known process of proteasome-mediated degradation of polyubiquitinated proteins, monoubiquitination of proteins is also an important post-translational modification that regulates various non-degradative cellular processes like protein trafficking, cellular signalling, DNA replication and DNA repair. We have previously characterized a multi-domain cycling sequence binding protein LdCSBP from Leishmania donovani, which binds specifically to a conserved CAUAGAAG octamer containing RNAs via its uniquely arranged CCCH type Zn-fingers and degrades them using its Smr endonuclease domain, indicative of its potential role in the turnover of the S-phase mRNAs. Remarkably, its riboendonuclease activity is inhibited due to the incorporation of a monoubiquitin residue in the ZnF domain, though the target Lys residue remains unknown. Here, we report through systematic mutation of Lys residue to Ala that Lys-413 in LdCSBP is the site of monoubiquitination. However, the amino acid motif around the target Lys in LdCSBP is not consensus with any previously known monoubiquitination site, though partial homology is observed with a subset of recently identified mammalian ubiquitination target sites. Interestingly, Lys-413 of LdCSBP is conserved in the homologous annotated proteins from the related kinetoplastida parasites, suggesting similar monoubiquitination-mediated regulation of RNA endonuclease activity in the organisms.

Visceral leishmaniasis: Experimental models for drug discovery.

Visceral leishmaniasis (VL) or kala-azar is a chronic protozoan infection in humans associated with significant global morbidity and mortality. The causative agent is a haemoflagellate protozoan Leishmania donovani, an obligate intracellular parasite that resides and multiplies within macrophages of the reticulo-endothelial system. Most of the existing anti-leishmanial drugs have serious side effects that limit their clinical application. As an alternate strategy, vaccination is also under experimental and clinical trials. The in vitro evaluation designed to facilitate rapid testing of a large number of drugs has been focussed on the promastigotes milt little attention on the clinically relevant parasite stage, amastigotes. Screening designed to closely reflect the situation in vivo is currently time consuming, laborious, and expensive, since it requires intracellular amastigotes and animal model. The ability to select transgenic Leishmania expressing reporter proteins, such as the green fluorescent proteins (GFP) or the luciferase opened up new possibilities for the development of drug screening models. Many experimental animal models like rodents, dogs and monkeys have been developed, each with specific features, but none accurately reproduces what happens in humans. Available in vitro and in vivo methodologies for antileishmanial drug screening and their respective advantages and disadvantages are reviewed.

Glycobiology of Leishmania donovani.

Leishmania donovani, the causative organism of visceral leishmaniasis (VL) is one of the deadliest of the entire known Leishmania species. This protozoan parasite displays immense adaptability to survive under extremely harsh conditions. Cell surface glycoconjugates play a pivotal role in parasite virulence and infectivity. This review mainly highlights on the importance of these molecules and their reported roles with special emphasis on L. donovani sialobiology. The recently evolved information reported by our group regarding the identification and characterization of sialoglycans and their possible mode(s) of acquisition as also the detailed identification, characterization of anti-O-acetylated sialic acid (anti-OAcSA) antibodies and their emerging biological roles, notably as molecules that may aid in host defense against the pathogen has been vividly discussed in this review.

Susceptible hosts: a resort for parasites right in the eye of the immune response

Trypanosomatid protozoan parasites express an aggressive strategy of parasitism by infecting host macrophages and inducing extensive T-lymphocyte activation. One goal of such strategy is to drive the immune response of genetically susceptible hosts to a state of unresponsiveness regarding parasite killing. Unresponsiveness is achieved through different mechanisms, depending on the parasite species. In this brief review, recent findings on the molecular and cellular bases of the parasites' exploitation of host immune responses are discussed.

Epidemia de leishmaniose visceral no Estado de Piauí, Brasil, 1980-1986 / Visceral leishmaniasis in Piaui State, Brazil, 1980-1986

Analisou-se a epidemia de calazar ocorrida no Estado do Piauí, no período de 1980-1986. Os dados foram coletados pela SUCAM-Piauí, òrgäo do Ministério da Saúde para o controle de endemias, pela busca ativa na rede de assistência à saúde do Estado. A epidemia iniciou-se em municípios do centro e do norte, em 1980. No interior, ao contrário do período endêmico, quando predominou em áreas de maior altitude e clima semi-árido, a epidemia grassou nos vales de rios e em regiäo mais úmida, de clima tropical. A capital do Piauí, Teresina, foi atingida em 1981, com pico epidêmico em 1984 e tendo sido responsável por mais de 60 por cento dos 1.509 casos de todo o Estado. Foram feitas tentativas de controle de uso intensivo de inseticidas e eliminaçäo de cäes. Nas outras regiöes do Piauí, borrifadas intensivamente para o controle da doença de Chagas e da malária, a epidemia foi pouco importante e cedeu espontaneamente. Nem a casuística e nem a populaçäo flebotomínica de Teresina apresentaram variaçöes sazonais significativas, mas estiveram moderadamente correlacionadas entre si. Houve maior prevalência em menores de cinco anos, principalmente nos anos de maior incidência, e menor em maiores de 40 anos. A distribuiçäo geográfica do processo epidêmico e a concomitância de seu início com seca prolongada acompanhada de emigraçäo de pessoas e animais domésticos procedentes de regiöes endêmicas para aquelas epidêmicas, sugerem que estesd movimentos migratòrios desencadearam a epidemia. O fato de o processo epidêmico ter cedido espontaneamente em áreas onde näo se tentou o seu controle indica que näo se pode atribuir a apenas às medidas de controle o fim da epidemia. A partir da análise dos coeficientes de incidência específicos por faixa etária, é discutida a possibilidade da progressiva reduçäo na proporçäo de suscetíveis, determinada tanto por um grande número de infecçöes assintomáticas como pela ocorrência de imunidade duradoura, ter contribuído para a extinçäo da epidemia

Quantitative grading of Leishmania donovani amastigotes related to age of kala-azar patients.

Out of 370 Leishman Donovan bodies positive bone-marrow smears, maximum belonged to grade 1 + (42.4 per cent) and the least to grade 5 + (1.6 per cent). Persons belonging to 0-20 years age group were found in be statistically more susceptible to Leishmania infection as compared to persons above 20 years of age (P less than .01). The disease was least common in persons above 40 years (3.5 per cent) of age. Parasite load was found to be highest in 0-20 years group irrespective of grades of leishmania infection. Grade 5 + infection was found to be rare (1.6 per cent) and confined to 0-20 years age group. Males suffered from the disease predominantly (69.2 per cent) as compared to females (30.8 per cent).

Interacción de promastigotes de Leishmania donovani con celulas de exudado peritonial de ratones mediante la influencia de la quimotripsina / Interaction of Leishmania donovani promastigotes with peritoneal exudate cells of mice under the influence of chymotrypsin

Se hace un estudio de la interacción de promastigotes de Leishmania donovani con células de exudado peritoneal de ratón (c e p) mediante la influencia de la quimotripsina. La adhesión de los promastigotes a las c e p fue terminal y marginal, y en observaciones hechas a partir de los 10 minutos de enfrentamiento, esta adhesión fue nula hasta los 30 minutos en el grupo tratado, y sólo a las das horas hubo un pequeño incremento (2.4%) con respecto al control. Se observa marcada disminución en todos los parámetro medidos, tales como enlace, penetración, multiplicación intracelular, división de formas flageladas, en el grupo tratado. La quimiotripsina favorece la formación de formas intermedias flageladas, heciendose el parásito piriforme y esférico, apareciendo una forma aberrante de extremo anterior cilindrico que semeja a una forma coanoflagelada. Se sospecha que la enzima reduce efectivamente fragmentos proteicos o péptidos, los cuales pueden haber sido tan pequeños como para esconder a otros ligandos relacionados con la adhesión macrófago-parásito

Modulaçåo da resposta imune induzida por ciclofosfamida em Leishmaniose expeimental de Hamster / Effect of Cyclophosphamide in the modulation of immune response in the experimental Leishmaniose of the Hamster

Estudou-se a resposta imune da leishmaniose visceral em hamsteres inoculados com (10) x (7) amastigotas da Leishmania sp. cepa 70 por via intraperitonial. As alteraçöes imunológicas encontradas foram: produçåo de anticorpos anti-leishmânia, aumento da densidade linfocitária na zona B-dependente e reaçåo de hipersensibilidade tardia específica negativa. A modulaçåo da resposta imune com o uso da ciclofosfamida mostrou uma diminuiçåo no nível de anticorpos anti-leishmânia, depleçåo linfocitária da zona B-dependente, aparecimento da reaçåo de leishmania e sugeriu a existência de célula reguladora da reaçåo de hipersensibilidade tardia, sensível à ciclofosfamida, em hamster