PCR-RFLP analyses of Leishmania species causing cutaneous and mucocutaneous leishmaniasis revealed distribution of genetically complex strains with hybrid and mito-nuclear discordance in Ecuador

PCR-Restriction Fragment Length Polymorphism (RFLP) analyses targeting multiple nuclear genes were established for the simple and practical identification of Leishmania species without using expensive equipment. This method was applied to 92 clinical samples collected at 33 sites in 14 provinces of Ecuador, which have been identified at the species level by the kinetoplast cytochrome b (cyt b) gene sequence analysis, and the results obtained by the two analyses were compared. Although most results corresponded between the two analyses, PCR-RFLP analyses revealed distribution of hybrid strains between Leishmania (Viannia) guyanensis and L. (V.) braziliensis and between L. (V.) guyanensis and L. (V.) panamensis, of which the latter was firstly identified in Ecuador. Moreover, unexpected parasite strains having the kinetoplast cyt b gene of L. (V.) braziliensis and nuclear genes of L. (V.) guyanensis, L. (V.) panamensis, or a hybrid between L. (V.) guyanensis and L. (V.) panamensis were identified. This is the first report of the distribution of a protozoan parasite having mismatches between kinetoplast and nuclear genes, known as mito-nuclear discordance. The result demonstrated that genetically complex Leishmania strains are present in Ecuador. Since genetic exchanges such as hybrid formation were suggested to cause higher pathogenicity in Leishmania and may be transmitted by more species of sand flies, further country-wide epidemiological studies on clinical symptoms, as well as transmissible vectors, will be necessary.

Leishmaniasis caused by intracellular protozoa of the genus Leishmania is a neglected tropical disease widely distributing worldwide, especially in tropical and subtropical areas. Approximately 20 species are known to be pathogenic to humans, of which eight species have been recorded as causative agents of cutaneous and mucocutaneous leishmaniases in Ecuador. Since infecting species are the major determinant of clinical outcomes, identification at the species level is important for the treatment and prognosis. The parasite species have been identified conventionally by multilocus enzyme electrophoresis (MLEE) and recently by genetic analysis such as sequencing and genotyping. In the present study, PCR-Restriction Fragment Length Polymorphism (RFLP) targeting multiple nuclear genes was employed, and the results were compared with those obtained by kinetoplast cytochrome b (cyt b) gene sequence analysis, which is widely applied to species identification. Although most results corresponded between the two analyses, PCR-RFLP revealed presence of unexpected genetically complex Leishmania strains having characteristics of hybrid and mito-nuclear discordance. Since hybrid strains of Leishmania were suggested to increase disease severity and may be transmitted by a wider range of sand fly species, careful epidemiological research, including clinical courses and vector research, will be needed.

Geographic Distribution of Leishmania Species in Ecuador Based on the Cytochrome B Gene Sequence Analysis

A countrywide epidemiological study was performed to elucidate the current geographic distribution of causative species of cutaneous leishmaniasis (CL) in Ecuador by using FTA card-spotted samples and smear slides as DNA sources. Putative Leishmania in 165 samples collected from patients with CL in 16 provinces of Ecuador were examined at the species level based on the cytochrome b gene sequence analysis. Of these, 125 samples were successfully identified as Leishmania (Viannia) guyanensis, L. (V.) braziliensis, L. (V.) naiffi, L. (V.) lainsoni, and L. (Leishmania) mexicana. Two dominant species, L. (V.) guyanensis and L. (V.) braziliensis, were widely distributed in Pacific coast subtropical and Amazonian tropical areas, respectively. Recently reported L. (V.) naiffi and L. (V.) lainsoni were identified in Amazonian areas, and L. (L.) mexicana was identified in an Andean highland area. Importantly, the present study demonstrated that cases of L. (V.) braziliensis infection are increasing in Pacific coast areas.

Development of a loop-mediated isothermal amplification method for rapid mass-screening of sand flies for Leishmania infection

Entomological monitoring of Leishmania infection in leishmaniasis endemic areas offers epidemiologic advantages for predicting the risk and expansion of the disease, as well as evaluation of the effectiveness of control programs. In this study, we developed a highly sensitive loop-mediated isothermal amplification (LAMP) method for the mass screening of sand flies for Leishmania infection based on the 18S rRNA gene. The LAMP technique could detect 0.01 parasites, which was more sensitive than classical PCR. The method was robust and could amplify the target DNA within 1h from a crude sand fly template without DNA purification. Amplicon detection could be accomplished by the newly developed colorimetric malachite green (MG)--mediated naked eye visualization. Pre-addition of MG to the LAMP reaction solution did not inhibit amplification efficiency. The field applicability of the colorimetric MG-based LAMP assay was demonstrated with 397 field-caught samples from the endemic areas of Ecuador and eight positive sand flies were detected. The robustness, superior sensitivity, and ability to produce better visual discriminatory reaction products than existing LAMP fluorescence and turbidity assays indicated the field potential usefulness of this new method for surveillance and epidemiological studies of leishmaniasis in developing countries.

Dimiconin, a novel coagulation inhibitor from the kissing bug, Triatoma dimidiata, a vector of Chagas disease

Sequence analysis of Triatoma (T.) dimidiata salivary gland cDNA library resulted in the identification of two transcripts (Td60 and Td101) homologous to triabin, an inhibitor of thrombin in T. pallidipennis saliva. In the present study, a recombinant protein of Td60, designated dimiconin, was expressed in Escherichia coli and its activity was characterized. The resulting protein inhibited the intrinsic but not extrinsic blood coagulation pathway, suggesting that dimiconin is not a thrombin inhibitor. Measuring the enzymatic activity of coagulation factors using chromogenic substrates revealed that dimiconin efficiently inhibited factor XIIa (FXIIa) activity in a dose-dependent manner. In addition, pre-incubation of dimiconin with FXII effectively inhibited FXIIa activity whereas dimiconin did not affect already activated FXIIa, indicating that dimiconin inhibits the activation of FXII but not enzymatic activity of FXIIa. These results showed that dimiconin is an inhibitor of the contact phase initiated by FXII activation in the blood coagulation cascade, which differs from the bioactivity of triabin.

Comparison of major immunoglobulins intrathecal synthesis patterns in Ecuadorian and Cuban patients with angiostrongyliasis

Angiostrongylus cantonensis meningitis was first reported in Cuba in 1981, and it was recently reported in South America. The aim of this paper is to evaluate the intrathecal immunoglobulin synthesis patterns from Cuba's and Ecuador's patients with angiostrongyliasis; 8 Ecuadorian patients from two different outbreaks and 28 Cuban patients were studied. Simultaneous blood and cerebrospinal fluid samples were taken. Immunoglobulin (Ig) A, IgM, IgG, and albumin were quantified by radial immunodiffusion. Corresponding Reibergrams were applied. A three-Ig pattern was the most frequent in the two groups, but IgM was presented in all Ecuadorian young mature patients; however, in the Cuban children, only 12 of 28 patients had intrathecal IgM, but about 90% had an IgA and IgG synthesis at time of later puncture. This indicates that, with a larger amount of parasites ingested, clinical symptoms are more severe, and a higher frequency of intrathecal IgM synthesis could be observed. This is discussed as a similarity with the intrathecal IgM synthesis in African trypanosomiasis.