[Molecular typing of Leishmania (Leishmania) amazonensis and species of the subgenus Viannia associated with cutaneous and mucosal leishmaniasis in Colombia: A concordance study]

Laboratory diagnostics for human Leishmania infections: a polymerase chain reaction-focussed review of detection and identification methods

Leishmania infections span a range of clinical syndromes and impact humans from many geographic foci, but primarily the world's poorest regions. Transmitted by the bite of a female sand fly, Leishmania infections are increasing with human movement (due to international travel and war) as well as with shifts in vector habitat (due to climate change). Accurate diagnosis of the 20 or so species of Leishmania that infect humans can lead to the successful treatment of infections and, importantly, their prevention through modelling and intervention programs. A multitude of laboratory techniques for the detection of Leishmania have been developed over the past few decades, and although many have drawbacks, several of them show promise, particularly molecular methods like polymerase chain reaction. This review provides an overview of the methods available to diagnostic laboratories, from traditional techniques to the now-preferred molecular techniques, with an emphasis on polymerase chain reaction-based detection and typing methods.

Comparative analysis of the transcriptional responses of five Leishmania species to trivalent antimony

BACKGROUND

Leishmaniasis is a neglected tropical disease caused by several species of Leishmania. The resistance phenotype of these parasites depends on the characteristics of each species, which contributes to increased therapeutic failures. Understanding the mechanism used by the parasite to survive under treatment pressure in order to identify potential common and specific therapeutic targets is essential for the control of leishmaniasis. The aim of this study was to investigate the expression profiles and potential shared and specific resistance markers of the main Leishmania species of medical importance [subgenus L. (Leishmania): L. donovani, L. infantum and L. amazonensis; subgenus L. (Viannia): L. panamensis and L. braziliensis)] resistant and sensitive to trivalent stibogluconate (SbIII).

METHODS

We conducted comparative analysis of the transcriptomic profiles (only coding sequences) of lines with experimentally induced resistance to SbIII from biological replicates of five Leishmania species available in the databases of four articles based on ortholog attribution. Simultaneously, we carried out functional analysis of ontology and reconstruction of metabolic pathways of the resulting differentially expressed genes (DEGs).

RESULTS

Resistant lines for each species had differential responses in metabolic processes, compound binding, and membrane components concerning their sensitive counterpart. One hundred and thirty-nine metabolic pathways were found, with the three main pathways comprising cysteine and methionine metabolism, glycolysis, and the ribosome. Differentially expressed orthologous genes assigned to species-specific responses predominated, with 899 self-genes. No differentially expressed genes were found in common among the five species. Two common upregulated orthologous genes were found among four species (L. donovani, L. braziliensis, L. amazonensis, and L. panamensis) related to an RNA-binding protein and the NAD(P)H cytochrome-B5-oxidoreductase complex, associated with transcriptional control and de novo synthesis of linoleic acid, critical mechanisms in resistance to antimonials.

CONCLUSION

Herein, we identified potential species-specific genes related to resistance to SbIII. Therefore, we suggest that future studies consider a treatment scheme that is species-specific. Despite the limitations of our study, this is the first approach toward unraveling the pan-genus genetic mechanisms of resistance in leishmaniasis.

Surveillance for Leishmania asymptomatic infection in endemic foci of cutaneous leishmaniasis in Venezuela: a combination of leishmanin skin test and PCR using blood clots improves detection and enables identification of species

BACKGROUND

Little is known about the prevalence of asymptomatic leishmaniasis in Venezuela. The objective of this study was to quantify Leishmania asymptomatic infection in six endemic foci of cutaneous leishmaniasis (CL) in Portuguesa State, Venezuela, where no previous data were available.

METHODS

Study of the prevalence of Leishmania asymptomatic infection was carried out in 841 individuals from six endemic foci of CL in the municipalities Sucre and Ospino, Portuguesa State. We applied the leishmanin skin test (LST) and the internal transcribed spacer 1 (ITS1) PCR to DNA from sera and blood clots of all LST-positive and 20% of LST-negative patients.

RESULTS

Of 841 inhabitants tested by LST, 197 returned a positive reaction (23.42%); all of the LST-positives (197) and 121 negatives were screened by nested PCR using serum and blood clots. Among the LST-positive group, 2.54% were PCR-positive with sera, while 44.67% were positive with blood clots. In the LST-negative group, PCR was positive in 2.48% of serum samples and in 38.84% of blood clots.

CONCLUSIONS

It is recommended that LST and PCR on blood clots are used together to detect exposure and asymptomatic infection and for identification of the Leishmania species.

Cutaneous leishmaniasis in the 21st century: from the laboratory to the bedside

PURPOSE OF REVIEW

Despite modern advances in molecular diagnostic tools and a better understanding of its complex pathophysiology, cutaneous leishmaniasis, a neglected tropical disease, remains a major global health problem. Laboratory methods to inform prognosis and treatment are not widely available, the therapeutic options are limited and have significant adverse effects, and emergence of drug resistance is a further complication. New advances in the understanding of the role of Leishmania RNA virus (LRV) as a prognostic factor, speciation methods and antimicrobial resistance testing and their limitations will be discussed.

RECENT FINDINGS

LRV, an intracytoplasmic endosymbiont found mostly in Leishmania spp. associated with more severe disease, appears to play a role in modulating the host immune response and has been associated with treatment failure in some Viannia subgenus species. Proper speciation is an important guide to management. However, recent findings have demonstrated significant heterogeneity of results related to differences in genotyping methods.

SUMMARY

Recognition of the role of LRV in immune modulation and response to treatment along with more accessible tools for its detection to guide management at the bedside should allow a better individualized approach. Improving accessibility and standardization of speciation methods and antimicrobial susceptibility testing should be major goals to improve cutaneous leishmaniasis management in the 21st century.

Leishmaniasis diagnosis: an update on the use of parasitological, immunological and molecular methods

Diagnosis of leishmaniasis has always been a major challenge as its clinical features resemble some other commonly occurring diseases such as tuberculosis, typhoid, and malaria. Reliable laboratory methods become important for differential diagnosis. Demonstration of the parasites in stained preparations of bone marrow and splenic aspirates being risky and invasive is still the gold standard for diagnosis. Serological tests utilizing rapid immunochromatographic formats or rK39 in enzyme linked immune sorbent assay, immunoblotting, direct agglutination test have complications related to high proportions of positive asymptomatic individuals and the inability to diagnose a relapse. Among the molecular techniques, polymerase chain reaction is the most commonly used technique that is successfully implied for diagnosis. This review provides updated information on the recent developments in the field of diagnosis in leishmaniasis, various methods utilized with their advantages and limitations.

Improving the sensitivity of an hsp20-based PCR for genus detection of Leishmania parasites in cutaneous clinical samples: a proof of concept

Leishmaniasis is a parasitic disease of medical importance widely distributed around the world. Several methods are available for diagnosis but molecular approaches are highly recommended. To improve the sensitivity of an existing hsp20 gene based-PCR protocol to detect Leishmania parasites, primers were redesigned to amplify a shorter fragment using a new PCR variant (PCR-hsp20S). In this study, we aimed at characterizing the performance of the new method on cutaneous clinical samples and compare it with the former PCR-hsp20. The analytical sensitivity of the PCR-hsp20S was evaluated using DNA dilutions (100-0.1 pg) from Leishmania donovani and resulted in the detection of 10 fg of parasitic DNA, the equivalent to 0.05 parasite genome. For the diagnostic evaluation, a panel of 127 human clinical samples was used to calculate the parameters of sensitivity, specificity, accuracy, and positive and negative predictive values of the PCR-hsp20S. Diagnostic sensitivity was 94% (CI, 89.1-99.7%) and the specificity of 100% (CI, 98.6-100%). The same panel was also evaluated with the PCR-hsp20 to calculate the agreement between both molecular assays and to compare their performances. While both hsp20-based PCRs showed a good agreement coefficient (kappa index = 0.6), the performance of the novel variant, PCR-hsp20S, was significantly higher in terms of sensitivity (P = 0.0001) allowing the accurate detection of a higher number of Leishmania-positive clinical samples. We endorse the use of the PCR-hsp20S over the former protocol for the detection of Leishmania parasites from cutaneous clinical samples. In addition, as an improved sensitivity was achieved with the new method merely through the amplification of a shorter gene fragment, this investigation constitutes an experimental proof of this concept.