Actividad anti-Toxoplasma de extractos metanólicos de frutos y hojas de Sambucus nigra (Caprifoliaceae)

<p><em>Toxoplasma gondii </em>is an obligatory intracellular parasite that infects a wide range of warm-blooded animals and humans. Considering the severity of toxoplasmosis, side effects of current treatments, and the contribution of the ethnopharmacological knowledge for the treatment of parasitic infections, the aim of the present study was to investigate the efficacy of methanolic extracts from the fruits and leaves of <em>Sambucus nigra </em>against tachyzoite of <em>T. gondii</em>. For this, fruits and leaves of <em>S. nigra </em>were collected from Mazandaran province, Iran, were dried under the shade, and powdered using a commercial electrical blender. For extractions, methanol was used as solvent. Virulent RH strain of <em>T. gondii</em> was maintained in mice and macrophages containing tachyzoites were aspirated from the peritoneal cavity. Four concentrations (5, 10, 25 and 50mg/mL) of <em>S. nigra </em>extract were incubated with infected macrophages for 30, 60, 120 and 180 minutes and the viability of the tachyzoites were evaluated by trypan blue staining. Results showed that <em>S. nigra </em>fruit extracts at the concentrations of 5 and 10mg/mL killed 100% of <em>T. gondii</em> tachyzoites after 60 and 120 minutes, respectively; and concentrations of 25 and 50mg/mL killed 100% of the tachyzoites after 30 minutes. Additionally, extract of <em>S. nigra</em> leaves, at the concentrations of 5, 10 and 25mg/mLafter 180 minutes, and concentration of 50mg/mLafter 60 minutes, resulted with the highest efficacy. Our results showed that <em>S. nigra</em> has acceptable efficacy <em>in vitro</em> and the parasiticidal effect of fruit extract was significantly better than leaf extract. However, <em>in vivo</em> efficacy of this extract needs further investigation.</p>

Vaccines for Canine Leishmaniasis

Leishmania infantumis the obligatory intracellular parasite of mammalian macrophages and causes zoonotic visceral leishmaniasis (ZVL). The presence of infected dogs as the main reservoir host of ZVL is regarded as the most important potential risk for human infection. Thus the prevention of canine visceral leishmaniasis (CVL) is essential to stop the current increase of the Mediterranean visceral leishmaniasis. Recently considerable advances in achieving protective immunization of dogs and several important attempts for achieving an effective vaccine against CVL lead to attracting the scientists trust in its important role for eradication of ZVL. This paper highlights the recent advances in vaccination against canine visceral leishmaniasis from 2007 until now.

Q Fever at the Turn of the Century

Q fever is an infectious zoonotic disease characterized by sudden fever, headache, and atypical pneumonia, caused by Coxiella burneti--an obligatory intracellular parasite. Based on phylogenetic analysis of the genes sequences, the classification was changed and C. burnetii species was included to the gamma subgroup of the proteobacteria, Legionellales order and Coxiellaceae family. This analysis showed more than 99% sequence similarity of 16SrRNA gene among the strains isolated in different regions of the world. Q fever is a widespread in the world zoonosis. Its main reservoir in the rural environment are farm animals: cows, sheep, goats, and urban pets such as dogs, cats, rabbits. In acute infection these bacteria are detected in various internal organs such as lungs, liver, spleen, and in excretion in urine, faeces and milk. During childbirth, they occur in large number in the amniotic fluid and placenta. Recently, it has been found that free-living amoeba Acanthamoeba castellani may also be a reservoir of the pathogen. The intra-amoebal location of C. burnetii cells was observed.

Genome reduction in prokaryotic obligatory intracellular parasites of humans: a comparative analysis

Obligatory intracellular parasites have undergone significant genome reduction by gene loss over time in the context of their obligate associations with the host. The flux, streamlining and elimination of genes in these genomes constitute a selective and ongoing process. Comparative analyses of five completely sequenced obligatory intracellular parasite genomes reveal that these genomes display marked similarities in patterns of protein length and frequency distribution, with substantial sharing of a ‘backbone genome’. From category distribution based on the database of cluster of orthologous groups of proteins (COG), it is clear that habitat is a major factor contributing to genome reduction. It is also observed that, in all five obligatory intracellular parasites, the reduction in number of genes/proteins is greater for proteins with lengths of 200–600 amino acids. These comparative analyses highlight that gene loss is function-dependent, but is independent of protein length. These comparisons enhance our knowledge of the forces that drive the extreme specialization of the bacteria and their association with the host.

A novel polymer of tubulin forms the conoid of Toxoplasma gondii

Toxoplasma gondii is an obligatory intracellular parasite, an important human pathogen, and a convenient laboratory model for many other human and veterinary pathogens in the phylum Apicomplexa, such as Plasmodium, Eimeria, and Cryptosporidia. 22 subpellicular microtubules form a scaffold that defines the cell shape of T. gondii. Its cytoskeleton also includes an intricate apical structure consisting of the conoid, two intraconoid microtubules, and two polar rings. The conoid is a 380-nm diameter motile organelle, consisting of fibers wound into a spiral like a compressed spring. FRAP analysis of transgenic T. gondii expressing YFP-α-tubulin reveals that the conoid fibers are assembled by rapid incorporation of tubulin subunits during early, but not late, stages of cell division. Electron microscopic analysis shows that in the mature conoid, tubulin is arranged into a novel polymer form that is quite different from typical microtubules.

Molecular biology of Leishmania

Leishmania is a trypanosomatid protozoa with a digenetic life cycle. Sandflies inject promastigotes, the free living form present in their salivary glands, into mammals where the parasite colonizes macrophages, transforming into intracellular amastigotes. The cycle is completed when during a blood meal the insect ingests infected macrophages, the amastigotes are released in the gut where they transform back into promastigotes. Leishmania has to adapt to the changing life conditions, from free-living forms in the poikilothermic insect vector to obligatory intracellular parasite in the homeothermic mammalian host. It also has to adapt to the acidic pH of the macrophage's phagolysosome where amastigotes multiply. The adaptative response of Leishmania includes morphological, physiological, and biochemical changes. Promastigotes can be grown in culture medium. Studies of changes taking place during adaptation have been facilitated by the establishment of in vitro conditions that allow the transformation of amastigotes into promastigotes and vice versa. The system is well suited for studying regulation of gene expression during adaptative differentiation. Some mechanisms of mRNA processing are unique to these protozoa: trans-splicing and RNA editing. Several genes that are differentially expressed in the two stages have been studied. No obvious cis regulatory motifs have been found in the DNA.Key words: Leishmania, genes, differentiation, regulation.