Impairment of Interleukin-17A Expression in Canine Visceral Leishmaniosis is Correlated with Reduced Interferon-γ and Inducible Nitric Oxide Synthase Expression.

Dogs are the primary urban reservoir of Leishmania infantum and play a crucial role in the transmission of this parasite to man via sandflies. The spleen and liver are the main target organs of L. infantum infection, but few studies have evaluated the immune response to this infection in the canine liver. To identify the immunological mediators involved in resistance and/or susceptibility to canine visceral leishmaniosis (CVL), we selected 21 dogs naturally infected by L. infantum and classified as asymptomatic or symptomatic. Immunological parameters were analysed and correlations with clinical signs were determined. Symptomatic dogs showed higher numbers of parasites and less leucocyte infiltration in the liver compared with asymptomatic dogs. The progression of this disease was characterized not only by the down regulation of T helper (Th) 1-related cytokines, such as interferon (IFN)-γ and tumour necrosis factor (TNF)-α, but also by the down regulation of genes encoding interleukin (IL)-17A, inducible nitric oxide synthase (iNOS) and IL-10 in the spleen and liver in symptomatic dogs compared with asymptomatic dogs. Importantly, IL-17A gene transcription level was positively correlated with mRNA expression for iNOS and IFN-γ. Th1- and Th17-related cytokines therefore appear to play a role in restricting parasite growth via iNOS activation and decrease susceptibility of dogs to CVL.

Genetic analyses of Trypanosoma cruzi isolates from naturally infected triatomines and humans in northeastern Brazil.

Trypanosoma cruzi genetic diversity was investigated in 25 isolates (vectors and humans) from the semiarid zone of the State of Rio Grande do Norte, Brazil. Molecular markers (3' region of the 24Salpha rRNA; mitochondrial cytochrome oxidase subunit 2 (COII) gene; spliced leader intergenic region (SL-IR) gene; allelic size microsatellite polymorphism) identified 56% TcIII (100% Panstrongyluslutzi; 50% Triatomabrasiliensis); 40% TcII (91.7% humans; 50% T. brasiliensis) and 4% TcI (human). Microsatellite analysis revealed monoclonal and heterozygous patterns on one or more microsatellite loci in 64% of T. cruzi isolates (92.3% triatomines; 33.3% humans) and 36% putative polyclonal populations (66.7% humans; 7.7% triatomines) by loci SCLE10, SCLE11, TcTAT20, TcAAAT6, all belonging to TcII. Identical T. cruzi polyclonal profiles (88.9%) were detected, mostly from humans. The adaptative natural plasticity of TcII and TcIII and their potential for maintaining human infection in T. brasiliensis were confirmed. Intraspecific and phylogenetic T. cruzi diversity in the sylvatic and domestic transmission cycles in this specific region will provide exclusive control strategies.

Random amplified polymorphic DNA profiles of Trypanosoma cruzi isolates from chagasic patients with different clinical forms.

The genetic variability of 61 Trypanosoma cruzi isolates from 47 chronic chagasic patients of Minas Gerais state was analyzed by random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) using M13-40, lambdagt11-F, and L15996 primers. Cluster analysis by unweighted pair group method analysis was applied to RAPD profiles, and cluster analysis used to verify a possible correlation among different clinical forms of the disease from these patients. The T. cruzi isolates showed distinct grouping on tree topology, with the isolates not being possible to establish a correlation to the clinical forms of Chagas' disease. These data showed that the T. cruzi isolates from these patients would compose a group of populations well correlated genetically.

Blood culture and polymerase chain reaction for the diagnosis of the chronic phase of human infection with Trypanosoma cruzi.

In the present study, we evaluated for the first time the profile of blood parasitism in untreated, chronic Chagas' disease. The study was conducted on 60 patients and a control group of nine serologically negative individuals. Analysis of three blood samples showed 70% cumulative positivity for blood culture and 86.7% positivity for PCR. The comparison of the two tests revealed that 41.1% (74/180) of the samples presented positive results for both PCR and blood culture, 22.2% (40/180) were positive for PCR alone, and 4.4% (8/180) were positive for blood culture and negative for PCR. The addition of the second sample raised positivity significantly for both blood culture ( P=0.0000) and PCR ( P=0.0369). Addition of the third sample was also statistically significant for blood culture ( P=0.0001) but not for PCR ( P=0.1186). These data point to the importance of studying the parasitemia of Trypanosoma cruzi-infected individuals before specific treatment. They also suggest that at least two blood samples should be collected and that two tests should be used, if possible--a procedure that considerably improves the parasitologic diagnosis of Chagas' disease and the evaluation of therapeutic efficacy.

Hemocultures from chronic chagasic patients using EDTA or heparin as anticoagulants

Hemoculture tests, a method for the detection of Trypanosoma cruzi, wre used to investigate the effects of the anticoagulants heparin or EDTA on the parasite growth in culture medium (liver infusion tryptose, LIT). Hemocultures from 13 patients with positive serology for chronic Chagas' disease performed in parallel with both anticoagulants resulted in a total of seven (54%) positive hemocultures, three positive with blood samples collected with EDTA (23%), two with heparin (15%) and two with both anticoagulants (15%). There was no significant difference between the number of positive tubes in blood samples collected with either heparin (11%) or with EDTA (13%), an indication that heparin does not block the growth of T. cruzi. However, the simultaneous use of both anticoagulants may improve the positivity index of the hemocultures