Leishmania infection in blood donors: A new challenge in leishmaniasis transmission?

Transfusion-transmitted leishmaniasis has been a concern in regions endemic for the disease. Whether immediate or delayed, the risks posed by this mode of transmission call for careful assessment. The purpose of this study was to detect Leishmania infection in blood donors living in an endemic area and to investigate progression to the disease in these individuals. Immunofluorescent antibody test, enzyme-linked immunosorbent assay, leishmaniasis rapid test, and the polymerase chain reaction were applied to 430 donors in an initial evaluation. Of those donors with at least one positive test, 50 were reevaluated four years later by the same methods, as were 25 controls who had been negative on the same tests. In the first evaluation, Leishmania infection was detected in 41.4% (95% CI: 36.7-46.1) of donors (n = 430). None of the 75 reevaluated individuals had developed the disease, but retesting revealed positivity in at least one test in 36.0% (95% CI: 25.1-46.9) of donors. Of the 50 initially testing positive, 50% remained so on retesting. Of the 25 initially negative controls, two tested positive in the subsequent evaluation. The severity of the parasitosis and the risk of transfusion transmission warrant investigation of the potential inclusion of methods for Leishmania detection into blood banks for effective screening of infected donors.

Is Leishmania (Viannia) braziliensis parasite load associated with disease pathogenesis?

BACKGROUND: Leishmania (Viannia) braziliensis is the main etiological agent of tegumentary leishmaniasis in the Americas. Parasite molecular diversity and host immune status contribute to extensive variations in its clinical presentation within endemic areas of Brazil. Pentavalent antimonials have been used for more than 60 years as the first-line drug for all cases, despite the potential for severe side effects and refractoriness. In Rio de Janeiro, Brazil, most L. (V.) braziliensis infections are benign with a scarcity of parasites, although metastasis and refractory infections can arise. In this scenario, the use of novel molecular tools can be useful for diagnosis and to assess tissue parasitism, and is of benefit to clinical and therapeutic management. METHODS: In this study, parasite load was assessed by real-time PCR based on the leishmanial small subunit ribosomal RNA gene. RESULTS AND CONCLUSION: The data revealed a tendency to higher tissue parasitism in the skin compared to mucous lesion sites and a reduction with disease progression. Parasite load was lower in poor compared to good responders to antimonials, and was also reduced in recurrent lesions compared to primary ones. However, parasite load became higher with sequential relapses, pointing to an immune system inability to control the infection. Therefore the parasite burden does not seem to be a good predictor of disease progression.

Severity of tegumentary leishmaniasis is not exclusively associated with Leishmania RNA virus 1 infection in Brazil.

Leishmania RNA virus (LRV) has been shown to be a symbiotic component of Leishmania parasites in South America. Nested retro-transcription polymerase chain reaction was employed to investigate LRV1 presence in leishmaniasis lesions from Brazil. In endemic areas of Rio de Janeiro (RJ), no LRV1 infection was observed even with mucosal involvement. LRV1 was only detected in Leishmania (V.) guyanensis cutaneous lesions from the northern region, which were obtained from patients presenting with disease reactivation after clinical cure of their primary lesions. Our results indicated that the severity of leishmaniasis in some areas of RJ, where Leishmania (V.) brazi-liensis is the primary etiological agent, was not associated with Leishmania LRV1 infection.

Leishmania (Viannia) braziliensis: human mast cell line activation induced by logarithmic and stationary promastigote derived-lysates.

Herein we investigate the ability of live promastigotes and total lysate of Leishmania (Viannia) braziliensis, derived from parasites in the logarithmic (L-Lb) or stationary phase (S-Lb), to induce human mast cell line (HMC-1) activation. In comparison with medium-treated cells, a significant histamine release was observed in HMC-1 cultures stimulated with S-Lb. Lipophosphoglycan also induced histamine release by HMC-1 cells. In immunocytochemical assays, we found a marked staining for tryptase in medium-treated HMC-1 cells, however, stimulation with L-Lb or S-Lb caused a marked decrease in the color reaction as well as in the number of tryptase-positive cells. L-Lb and S-Lb induced an evident decrease in the intracellular expression of IL-4 but not IL-12. Live stationary promastigotes were able to induce high levels of IL-4 release in HMC-1 cultures. Furthermore, these cells released significant amounts of IL-12 when incubated with both types of live promastigotes. These results indicate that L. (V.) braziliensis promastigotes differ in their ability to induce direct human mast cells activation, according to the growth phase of the parasite. Furthermore, the release of pro-inflammatory mediators and cytokines could represent an important phenomenon that might favor the initial establishment of the infection.