Serial quantitative PCR assay for detection, species discrimination, and quantification of Leishmania spp. in human samples

Improved Treatment Outcome Following the Use of a Wound Dressings in Cutaneous Leishmaniasis Lesions

Leishmaniasis, caused by Leishmania parasites, is a neglected tropical disease and Cutaneous Leishmaniasis (CL) is the most common form. Despite the associated toxicity and adverse effects, Meglumine antimoniate (MA) remains the first-choice treatment for CL in Brazil, pressing the need for the development of better alternatives. Bacterial NanoCellulose (BNC), a biocompatible nanomaterial, has unique properties regarding wound healing. In a previous study, we showed that use of topical BNC + systemic MA significantly increased the cure rate of CL patients, compared to treatment with MA alone. Herein, we performed a study comparing the combination of a wound dressing (BNC or placebo) plus systemic MA versus systemic MA alone, in CL caused by Leishmania braziliensis. We show that patients treated with the combination treatment (BNC or placebo) + MA showed improved cure rates and decreased need for rescue treatment, although differences compared to controls (systemic MA alone) were not significant. However, the overall time-to-cure was significantly lower in groups treated with the combination treatment (BNC+ systemic MA or placebo + systemic MA) in comparison to controls (MA alone), indicating that the use of a wound dressing improves CL treatment outcome. Assessment of the immune response in peripheral blood showed an overall downmodulation in the inflammatory landscape and a significant decrease in the production of IL-1a (p < 0.05) in patients treated with topical BNC + systemic MA. Our results show that the application of wound dressings to CL lesions can improve chemotherapy outcome in CL caused by L. braziliensis.

Impaired signaling pathways on Berardinelli-Seip congenital lipodystrophy macrophages during Leishmania infantum infection

Berardinelli-Seip congenital lipodystrophy (CGL), a rare autosomal recessive disorder, is characterized by a lack of adipose tissue. Infections are one of the major causes of CGL individuals' premature death. The mechanisms that predispose to infections are poorly understood. We used Leishmania infantum as an in vitro model of intracellular infection to explore mechanisms underlying the CGL infection processes, and to understand the impact of host mutations on Leishmania survival, since this pathogen enters macrophages through specialized membrane lipid domains. The transcriptomic profiles of both uninfected and infected monocyte-derived macrophages (MDMs) from CGL (types 1 and 2) and controls were studied. MDMs infected with L. infantum showed significantly downregulated expression of genes associated with infection-response pathways (MHC-I, TCR-CD3, and granzymes). There was a transcriptomic signature in CGL cells associated with impaired membrane trafficking and signaling in response to infection, with concomitant changes in the expression of membrane-associated genes in parasites (e.g. δ-amastins). We identified pathways suggesting the lipid storage dysfunction led to changes in phospholipids expression and impaired responses to infection, including immune synapse (antigen presentation, IFN-γ signaling, JAK/STAT); endocytosis; NF-kappaB signaling; and phosphatidylinositol biosynthesis. In summary, lipid metabolism of the host plays an important role in determining antigen presentation pathways.

Simplified molecular diagnosis of visceral leishmaniasis: Laboratory evaluation of miniature direct-on-blood PCR nucleic acid lateral flow immunoassay

BACKGROUND

Diagnosis of visceral leishmaniasis (VL) in resource-limited endemic regions is currently based on serological testing with rK39 immunochromatographic tests (ICTs). However, rK39 ICT frequently has suboptimal diagnostic accuracy. Furthermore, treatment monitoring and detection of VL relapses is reliant on insensitive and highly invasive tissue aspirate microscopy. Miniature direct-on-blood PCR nucleic acid lateral flow immunoassay (mini-dbPCR-NALFIA) is an innovative and user-friendly molecular tool which does not require DNA extraction and uses a lateral flow strip for result read-out. This assay could be an interesting candidate for more reliable VL diagnosis and safer test of cure at the point of care.

METHODOLOGY/PRINCIPLE FINDINGS

The performance of mini-dbPCR-NALFIA for diagnosis of VL in blood was assessed in a laboratory evaluation and compared with the accuracy of rK39 ICTs Kalazar Detect in Spain and IT LEISH in East Africa. Limit of detection of mini-dbPCR-NALFIA was 650 and 500 parasites per mL of blood for Leishmania donovani and Leishmania infantum, respectively. In 146 blood samples from VL-suspected patients from Spain, mini-dbPCR-NALFIA had a sensitivity of 95.8% and specificity 97.2%, while Kalazar Detect had a sensitivity of 71.2% and specificity of 94.5%, compared to a nested PCR reference. For a sample set from 58 VL patients, 10 malaria patients and 68 healthy controls from Ethiopia and Kenya, mini-dbPCR-NALFIA had a pooled sensitivity of 87.9% and pooled specificity of 100% using quantitative PCR as reference standard. IT LEISH sensitivity and specificity in the East African samples were 87.9% and 97.4%, respectively.

CONCLUSIONS/SIGNIFICANCE

Mini-dbPCR-NALFIA is a promising tool for simplified molecular diagnosis of VL and follow-up of treated patients in blood samples. Future studies should evaluate its use in endemic, resource-limited settings, where mini-dbPCR-NALFIA may provide an accurate and versatile alternative to rK39 ICTs and aspirate microscopy.

Pentavalent Antimony Associated with G-CSF in the Treatment of Cutaneous Leishmaniasis Caused by Leishmania (Viannia) braziliensis

Cutaneous leishmaniasis (CL), caused by Leishmania braziliensis, in recent decades has shown decreasing cure rates after treatment with meglumine antimoniate (MA). Granulocyte colony-stimulating factor (G-CSF) is a cytokine associated with epithelialization and healing processes.

METHODS

This study compares the effectiveness of G-CSF associated with MA in the treatment of CL. A total of 32 patients aged between 18 and 50 years with CL confirmed for L. braziliensis were included in this study. G-CSF or placebo (0.9% saline) was applied by intralesional infiltration at four equidistant points on the edges of the largest ulcer on days 0 and 15 of treatment associated with intravenous MA.

RESULTS

Males predominated in the G-CSF group (59%), while females predominated in the control group (53%). Injuries to the lower limbs predominated in both study groups. The cure rate in the G-CSF group was 65% and in the control group it was 47%, 90 days after initiation of therapy.

CONCLUSIONS

Our data indicate that the association of G-CSF with MA is not superior to MA monotherapy. Although not significant, the potential benefit of this combination deserves further investigation. The use of higher doses or other routes of application of G-CSF in a greater number of patients should contribute to a definitive response.

Efficacy of the treatment using a microemulsion loaded with epoxy-α-lapachone in combination with meglumine antimoniate against murine infection by Leishmania (Leishmania) amazonensis

Leishmaniasis is a disease caused by Leishmania spp., affecting millions of people around the world. For decades, its treatment has been based on pentavalent antimonials, which notoriously cause toxic side effects in patients. In this study, epoxy-α-lapachone incorporated into an oil-in-water-type microemulsion (ELAP-ME) and meglumine antimoniate (MA) were assayed in monotherapy and in combination (ELAP-ME/MA) in BALB/c mice infected with Leishmania (Leishmania) amazonensis. In general, there was a reduction in paw lesion size (up to 37% reduction) and decreases of parasite loads in the footpad (∼40%) and lymph nodes (∼31%) of animals treated with ELAP-ME/MA, when compared to the non-treated control groups. Analyses of serum biochemical parameters revealed that the ELAP-ME/MA showed lower renal and hepatic toxicity when compared to MA 2-doses/week monotherapy. These findings indicate that the ELAP-ME/MA combination may be a promising approach for the treatment of cutaneous leishmaniasis.

Challenges of animals shelters in caring for dogs infected with Leishmania and other pathogens

The incidence of human Visceral Leishmaniasis (VL) has decreased in Brazil; however, the number of areas reporting human and canine cases has increased, with Leishmania infantum usually preceding human infection. This study aimed to analyze the profile of infectious diseases that are endemic for both human and canine VL, in dogs housed in a shelter located in the state of Rio Grande do Norte, Northeast Brazil. Data was obtained between November/2021 to April/2022. All dogs residing at the shelter (98 dogs) were examined and blood was collected for testing for L. infantum, Ehrlichia canis, and Babesia sp. Statistical analyses considered the clinical and laboratory findings. Of the 98 animals, approximately 43% were positive for L. infantum antibodies, 19% were positive for L. infantum kDNA, and 18% were L. infantum positive by culture. Greater levels of anti-leishmania antibodies were observed in dogs with symptoms suggestive of VL. The dogs tested positive for E. canis (19/98) and B. canis (18/98). Lutzomyia longipalpis was captured inside the shelter, representing 74.25% (n = 225) of whole sandflies in the dog shelter. Concomitant infection by L. infantum and E. canis increased the odds of death. Treatment of VL included the use of allopurinol (n = 48) and miltefosine (n = 8). Treated animals showed more signs of Leishmania infection. Tickborn parasites and Leishmania were prevalent in sheltered dogs in a VL-endemic area, which increases the odds of death and poses an additional challenge for caring for abandoned dogs and at the same time setting protocols to manage reservoirs of L. infantum.

Disseminated Leishmaniasis, a Severe Form of Leishmania braziliensis Infection

Disseminated leishmaniasis (DL) is an emergent severe disease manifesting with multiple lesions. To determine the relationship between immune response and clinical and therapeutic outcomes, we studied 101 DL and 101 cutaneous leishmaniasis (CL) cases and determined cytokines and chemokines in supernatants of mononuclear cells stimulated with leishmania antigen. Patients were treated with meglumine antimoniate (20 mg/kg) for 20 days (CL) or 30 days (DL); 19 DL patients were instead treated with amphotericin B, miltefosine, or miltefosine and meglumine antimoniate. High levels of chemokine ligand 9 were associated with more severe DL. The cure rate for meglumine antimoniate was low for both DL (44%) and CL (60%), but healing time was longer in DL (p = 0.003). The lowest cure rate (22%) was found in DL patients with >100 lesions. However, meglumine antimoniate/miltefosine treatment cured all DL patients who received it; therefore, that combination should be considered as first choice therapy.

Diagnostic accuracy of qPCR and microscopy for cutaneous leishmaniasis in rural Ecuador: A Bayesian latent class analysis

BACKGROUND

Clinical and laboratory diagnosis of cutaneous leishmaniasis (CL) is hampered by under-ascertainment of direct microscopy.

METHODS

This study compared the diagnostic accuracy of qPCR on DNA extracted from filter paper to the accuracy of direct smear slide microscopy in participants presenting with a cutaneous lesion suspected of leishmaniasis to 16 rural healthcare centers in the Ecuadorian Amazon and Pacific regions, from January 2019 to June 2021. We used Bayesian latent class analysis to estimate test sensitivity, specificity, likelihood ratios (LR), and predictive values (PV) with their 95% credible intervals (95%CrI). The impact of sociodemographic and clinical characteristics on predictive values was assessed as a secondary objective.

RESULTS

Of 320 initially included participants, paired valid test results were available and included in the diagnostic accuracy analysis for 129 from the Amazon and 185 from the Pacific region. We estimated sensitivity of 68% (95%CrI 49% to 82%) and 73% (95%CrI 73% to 83%) for qPCR, and 51% (95%CrI 36% to 66%) and 76% (95%CrI 65% to 86%) for microscopy in the Amazon and Pacific region, respectively. In the Amazon, with an estimated disease prevalence among participants of 73%, negative PV for qPCR was 54% (95%CrI 5% to 77%) and 44% (95%CrI 4% to 65%) for microscopy. In the Pacific, (prevalence 88%) the negative PV was 34% (95%CrI 3% to 58%) and 37% (95%CrI 3% to 63%). The addition of qPCR parallel to microscopy in the Amazon increases the observed prevalence from 38% to 64% (+26 (95%CrI 19 to 34) percentage points).

CONCLUSION

The accuracy of either qPCR on DNA extracted from filter paper or microscopy for CL diagnosis as a stand-alone test seems to be unsatisfactory and region-dependent. We recommend further studies to confirm the clinically relevant increment found in the diagnostic yield due to the addition of qPCR.

Subcutaneous, Oral, and Intranasal Immunization of BALB/c Mice with Leishmania infantum K39 Antigen Induces Non-Protective Humoral Immune Response

Visceral leishmaniasis is a high-burden disease caused by parasites of the Leishmania genus. The K39 kinesin is a highly antigenic protein of Leishmania infantum, but little is known about the immune response elicited by this antigen. We evaluated the humoral immune response of female BALB/c mice (n = 6) immunized with the rK39-HFBI construct, formed by the fusion of the K39 antigen to a hydrophobin partner. The rK39-HFBI construct was administered through subcutaneous, oral, and intranasal routes using saponin as an adjuvant. We analyzed the kinetics of IgG, IgG1, and IgG2a production. The groups were then challenged by an intravenous infection with L. infantum promastigote cells. The rK39-HFBI antigen-induced high levels of total IgG (p < 0.05) in all groups, but only the subcutaneous route was associated with increased production of IgG1 and IgG2a 42 days after immunization (p < 0.05), suggesting a potential secondary immune response following the booster dose. There was no reduction in the splenic parasite load; thus, the rK39-HFBI failed to protect the mice against infection under the tested conditions. The results presented here demonstrate that the high antigenicity of the K39 antigen does not contribute to a protective immune response against visceral leishmaniasis.

Parasite Detection in Visceral Leishmaniasis Samples by Dye-Based qPCR Using New Gene Targets of Leishmania infantum and Crithidia

Visceral leishmaniasis (VL) is a neglected disease considered a serious public health problem, especially in endemic countries. Several studies have discovered monoxenous trypanosomatids (Leptomonas and Crithidia) in patients with VL. In different situations of leishmaniasis, investigations have examined cases of co-infection between Leishmania spp. and Crithidia spp. These coinfections have been observed in a wide range of vertebrate hosts, indicating that they are not rare. Diagnostic techniques require improvements and more robust tools to accurately detect the causative agent of VL. This study aimed to develop a real-time quantitative dye-based PCR (qPCR) assay capable of distinguishing Leishmania infantum from Crithidia-related species and to estimate the parasite load in samples of VL from humans and animals. The primer LinJ31_2420 targets an exclusive phosphatase of L. infantum; the primer Catalase_LVH60-12060_1F targets the catalase gene of Crithidia. Therefore, primers were designed to detect L. infantum and Crithidia sp. LVH60A (a novel trypanosomatid isolated from VL patients in Brazil), in samples related to VL. These primers were considered species-specific, based on sequence analysis using genome data retrieved from the TriTryp database and the genome assembling of Crithidia sp. LVH60A strain, in addition to experimental and clinical data presented herein. This novel qPCR assay was highly accurate in identifying and quantifying L. infantum and Crithidia sp. LVH60A in samples obtained experimentally (in vitro and in vivo) or collected from hosts (humans, dogs, cats, and vectors). Importantly, the screening of 62 cultured isolates from VL patients using these primers surprisingly revealed that 51 parasite cultures were PCR+ for Crithidia sp. In addition, qPCR assays identified the co-infection of L. infantum with Crithidia sp. LVH60A in two new VL cases in Brazil, confirming the suspicion of co-infection in a previously reported case of fatal VL. We believe that the species-specific genes targeted in this study can be helpful for the molecular diagnosis of VL, as well as for elucidating suspected co-infections with monoxenous-like trypanosomatids, which is a neglected fact of a neglected disease.

Clinical Profile and Diagnosis of Recurrent Cutaneous Leishmaniasis

This case-control study compared the clinical profile, parasite load, polymerase chain reaction positivity, and response to therapy in patients with recurrent cutaneous leishmaniasis (RCL) with primary cutaneous leishmaniasis (CL). The RCL patients had milder diseases with lower parasite loads, a lower number of lesions, and more self-healing diseases than primary CL patients.

Dogs Harbor Leishmania braziliensis and Participate in the Transmission Cycle of Human Tegumentary Leishmaniasis

Dogs play an important role in transmission of Leishmania infantum, but epidemiologic and clinical studies of canine tegumentary leishmaniasis (CTL) are scarce. In an endemic area of human American tegumentary leishmaniasis (ATL) caused by Leishmania braziliensis, we determine the prevalence and incidence of both CTL and subclinical (SC) L. braziliensis infection in dogs and evaluated if the presence of dogs with CTL or SC L. braziliensis infection is associated with the occurrence of human ATL. SC infection in healthy animals and CTL in animals with ulcers were determined by PCR on biopsied healthy skin or on ulcers or by detecting antibodies against soluble leishmania antigen. We compared the occurrence of human ATL in homes with dogs with CTL or SC infection with control homes without dogs or with dogs without CTL or SC infection. The prevalence of SC infection was 35% and of CTL 31%. The incidence of SC infection in dogs was 4.6% and of CTL 9.3%. The frequency of ATL in humans was 50% in homes with infected dogs and 13% in homes without L. braziliensis infection in dogs. CTL and SC infection is highly prevalent, and dogs may participate in the transmission chain of L. braziliensis.

Post-kala-azar dermal leishmaniasis manifestation in a Mediterranean immunosuppressed patient: a rare incident

We present an interesting case of a patient with post-kala-azar dermal leishmaniasis (PKDL), encountered in Greece. The man developed PKDL while on treatment with lenalidomide and corticosteroids for multiple myeloma. PKDL is an important neglected tropical disease. It usually occurs in the Indian subcontinent and East Africa. To our knowledge, this is the first case of PKDL in a European territory. The case should raise awareness among clinicians that PKDL could be encountered in European countries, and further strengthens the immunosuppression hypothesis for the causation of PKDL.

Genetic Diversity and Population Structure of Leishmania infantum in Morocco as Revealed by Multilocus Sequence Typing (MLST) Approach

Leishmania infantum is endemic in Morocco, and it causes both visceral (VL) and cutaneous leishmaniasis (CL). In this study, the multilocus sequence typing (MLST) approach was used to investigate the phylogeny and population structure of Leishmania infantum strains isolated from CL and VL patients and the canine reservoir in different leishmaniasis endemic foci in Morocco. For this purpose, eight loci (pgm, alat, me, fh, g6pd, pgd, gpi and cytb) were amplified in 40 samples, out of which 31 were successfully sequenced. The genetic diversity analysis detected a high degree of intraspecific genetic variability among the studied strains. The phylogenetic and the haplotype analyses showed that most of the strains from the same geographical areas clustered together. The recombination among Leishmania infantum strains was revealed through a splits tree analysis and the number of recombination events. Moreover, the assessment of the gene flow between Leishmania infantum and Leishmania tropica through phylogenetic analysis and haplotype diversity in two endemic foci where the two species were sympatric showed no genetic exchange between the two species.

Assessing nystatin cream treatment efficacy against Leishmania (L.) amazonensis infection in BALB/c model

The current scenario for cutaneous leishmaniasis treatment includes the use of first and second-choice drugs, both therapeutic strategies presenting several adverse effects and being related to an increment of treatment-refractory parasite strains. These facts encourage the search for new treatment approaches, including repositioning drugs, such as nystatin. Although some in vitro assays show that this polyene macrolide compound has leishmanicidal activity, no in vivo evidence for a similar activity has been shown so far for the commercial nystatin cream formulation (25,000 IU/g). This work assessed the effects of nystatin cream administered on mice in an amount to completely cover the paw surface of BALB/c mice infected with L. (L.) amazonensis once a day, until a total of up to 20 doses. The data presented herein points to unequivocal evidence that this formulation is related to a statistically significant reduction of swelling/edema in mice paws when compared to animal groups not submitted to this treatment regimen after the fourth week of infection: lesion sizes at the sixth (p = 0.0159), seventh (p = 0.0079) and eighth (p = 0.0079) week. Furthermore, infection reduction relates to a decrease in parasite load in the footpad (∼48%) and in draining lymph nodes (∼68%) at 8th weeks post-infection. This is the first report of the effectiveness of nystatin cream used as a topical treatment in BALB/c model for cutaneous leishmaniasis.

Evaluation of a diagnostic device, CL Detect rapid test for the diagnosis of new world cutaneous leishmaniasis in Peru

BACKGROUND

Cutaneous leishmaniasis (CL) is a neglected disease and a public health problem in Latin America. The diagnosis of CL in poor hyperendemic regions relies to large extent on the identification of amastigotes in Giemsa-stained smears. There is an urgent need for a rapid, sensitive and low cost diagnostic method for use in field conditions for CL as current modalities are not readily available. The primary objective of this study was to determine the sensitivity and specificity of the FDA-cleared CL Detect Rapid Test in Peru, using modified test procedures rather than the instructions-for-use, by 1) increasing the extraction time and 2) increasing the volume of the sample added to the test strip. CL Detect Rapid Test results were compared against microscopy and kDNA-PCR, for the diagnosis of CL in ulcerated lesions. In addition, we compared two collection methods the dental broach used and mentioned in the CL Detect insert and the standard less invasive and easier to conduct scrapping method.

METHODOLOGY

Participants were patients who presented for medical consultation due to a suspected CL lesion. Four samples from the index lesion were collected using a dental broach, per package insert, and lancet scraping and tested by the modified CL Detect Rapid Test, microscopy, and PCR.

PRINCIPAL FINDINGS

A total of 156 subjects were eligible and evaluated. The modified CL Detect sensitivity was higher in specimens obtained by scraping (83.3%) than those from dental broach (64.2%). The specificity was lower in scrapings (77.8%) with a false positive rate of 22.2% compared with dental broach samples (91.7%) with a false positive rate of 8.3%. However, molecular analysis showed that all 8 false negative microscopy scrapings (those positive by modified CL Detect and negative by microscopy) were positive by kDNA-PCR, meaning that the modified CL Detect was more sensitive than microscopy.

CONCLUSIONS

These modifications to the package insert that resulted in a diagnostic sensitivity (83.3%) comparable to microscopy for species found in Peru may enable earlier anti-leishmanial drug treatment decisions based on a positive result from the CL Detect Rapid Test alone until further diagnostic tests like microscopy and PCR can be performed.

TRIAL REGISTRATION

NCT03762070; Clinicaltrials.gov.

Selective whole-genome amplification reveals population genetics of Leishmania braziliensis directly from patient skin biopsies

In Brazil, Leishmania braziliensis is the main causative agent of the neglected tropical disease, cutaneous leishmaniasis (CL). CL presents on a spectrum of disease severity with a high rate of treatment failure. Yet the parasite factors that contribute to disease presentation and treatment outcome are not well understood, in part because successfully isolating and culturing parasites from patient lesions remains a major technical challenge. Here we describe the development of selective whole genome amplification (SWGA) for Leishmania and show that this method enables culture-independent analysis of parasite genomes obtained directly from primary patient skin samples, allowing us to circumvent artifacts associated with adaptation to culture. We show that SWGA can be applied to multiple Leishmania species residing in different host species, suggesting that this method is broadly useful in both experimental infection models and clinical studies. SWGA carried out directly on skin biopsies collected from patients in Corte de Pedra, Bahia, Brazil, showed extensive genomic diversity. Finally, as a proof-of-concept, we demonstrated that SWGA data can be integrated with published whole genome data from cultured parasite isolates to identify variants unique to specific geographic regions in Brazil where treatment failure rates are known to be high. SWGA provides a relatively simple method to generate Leishmania genomes directly from patient samples, unlocking the potential to link parasite genetics with host clinical phenotypes.

Efficacy of intralesional meglumine antimoniate in the treatment of canine tegumentary leishmaniasis: A Randomized controlled trial

Dogs living in areas of Leishmania (Viannia) braziliensis transmission may present canine tegumentary leishmaniasis (CTL) characterized by cutaneous or muzzle ulcers as well as asymptomatic L. braziliensis infection. It is not clear if dogs participate in the transmission chain of L. braziliensis to humans. However, dogs may remain with chronic ulcers for a long time, and as there are no public policies about CTL, these animals die or are sacrificed. Here we compare the efficacy of intralesional meglumine antimoniate with intralesional 0.9% NaCl solution in CTL treatment. This randomized control study included 32 dogs with cutaneous or muzzle lesions who had L. braziliensis DNA detected by PCR in tissue biopsied. Group one received 5ml of intralesional Glucantime, and group two received 5ml 0.9% NaCl solution, both applied in the four cardinal points on days 0, 15, and 30. Cure was defined as complete healing of the ulcers in the absence of raised borders on day 90. There was no difference in animals' demographic and clinical features in the two groups (p >.05). While at the endpoint, the cure rate was 87.5% in the group test, and in those who received 0.9 NaCl the cure rate was only 12.5%. As important as the high cure rate, the healing time was faster in dogs treated with antimony than in those treated with saline (p < .001). Intralesional meglumine antimoniate is effective in the treatment of dogs with L. braziliensis infection and accelerates the healing time of CTL.

Assessment of Immune and Clinical Response in Patients with Mucosal Leishmaniasis Treated with Pentavalent Antimony and Pentoxifylline

Mucosal leishmaniasis (ML) is a severe form of tegumentary leishmaniasis associated with a persistent inflammatory response. High levels of TNF, IFN-γ, CXCL9 and CXCL10 are found in ML patients, and the association of pentoxifylline with antimony is more effective in decreasing the healing time in ML patients when compared to antimony alone. The present study aimed to investigate the existence of a correlation between cytokine and chemokine production and ML severity and evaluate the potential value of cytokine and chemokine production as marker of therapeutic response in ML patients. This prospective study included 86 subjects in an area of endemic Leishmania braziliensis transmission. Patients diagnosed with ML were classified into clinical stages ranging from I to V according to disease severity. TNF, IFN-γ, CXCL9 and CXCL10 levels were quantified in the supernatant of the mononuclear cell cultures by ELISA before and after treatment with antimony alone or antimony plus pentoxifylline. The median TNF level in the group with mild disease (Stages I-II) was 1064 pg/mL (142-3738 pg/mL), while, in the group with moderate or severe disease (Stages III-V), it was 1941 pg/mL (529-5294 pg/mL) (p = 0.008). A direct correlation was observed between ML clinical severity and levels of TNF production (r = 0.44, p = 0.007). Patients who were treated with antimony and pentoxifylline healed significantly faster than those treated with antimony alone (52 vs. 77 days, hazard ratio = 0.60; 95% confidence interval = 0.38-0.95, p = 0.013). Therapeutic failure was higher in the group that received antimony alone (25% vs. 7%; p = 0.041). There was a significant decrease in CXCL9 after therapy of ML in both groups (p = 0.013; p = 0.043). TNF levels are associated with the severity of mucosal diseases, and pentoxifylline associated with antimony should be the recommended therapy for ML in countries where liposomal amphotericin B is not available.

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.

Livestock and rodents within an endemic focus of Visceral Leishmaniasis are not reservoir hosts for Leishmania donovani

Leishmaniasis on the Indian subcontinent is thought to have an anthroponotic transmission cycle. There is no direct evidence that a mammalian host other than humans can be infected with Leishmania donovani and transmit infection to the sand fly vector. The aim of the present study was to evaluate the impact of sand fly feeding on other domestic species and provide clinical evidence regarding possible non-human reservoirs through experimental sand fly feeding on cows, water buffalo goats and rodents. We performed xenodiagnosis using colonized Phlebotomus argentipes sand flies to feed on animals residing in villages with active Leishmania transmission based on current human cases. Xenodiagnoses on mammals within the endemic area were performed and blood-fed flies were analyzed for the presence of Leishmania via qPCR 48hrs after feeding. Blood samples were also collected from these mammals for qPCR and serology. Although we found evidence of Leishmania infection within some domestic mammals, they were not infectious to vector sand flies. Monitoring infection in sand flies and non-human blood meal sources in endemic villages leads to scientific proof of exposure and parasitemia in resident mammals. Lack of infectiousness of these domestic mammals to vector sand flies indicates that they likely play no role, or a very limited role in Leishmania donovani transmission to people in Bihar. Therefore, a surveillance system in the peri-/post-elimination phase of visceral leishmaniasis (VL) must monitor absence of transmission. Continued surveillance of domestic mammals in outbreak villages is necessary to ensure that a non-human reservoir is not established, including domestic mammals not present in this study, specifically dogs.

Novel CRISPR-based detection of Leishmania species

Tegumentary leishmaniasis, a disease caused by protozoan parasites of the genus Leishmania, is a major public health problem in many regions of Latin America. Its diagnosis is difficult given other conditions resembling leishmaniasis lesions and co-occurring in the same endemic areas. A combination of parasitological and molecular methods leads to accurate diagnosis, with the latter being traditionally performed in centralized reference and research laboratories as they require specialized infrastructure and operators. Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas) systems have recently driven innovative tools for nucleic acid detection that combine high specificity, sensitivity and speed and are readily adaptable for point-of-care testing. Here, we harnessed the CRISPR-Cas12a system for molecular detection of Leishmania spp., emphasizing medically relevant parasite species circulating in Peru and other endemic areas in Latin America, with Leishmania (Viannia) braziliensis being the main etiologic agent of cutaneous and mucosal leishmaniasis. We developed two assays targeting multi-copy targets commonly used in the molecular diagnosis of leishmaniasis: the 18S ribosomal RNA gene (18S rDNA), highly conserved across Leishmania species, and a region of kinetoplast DNA (kDNA) minicircles conserved in the L. (Viannia) subgenus. Our CRISPR-based assays were capable of detecting down to 5 × 10⁻² (kDNA) or 5 × 10⁰ (18S rDNA) parasite genome equivalents/reaction with PCR preamplification. The 18S PCR/CRISPR assay achieved pan-Leishmania detection, whereas the kDNA PCR/CRISPR assay was specific for L. (Viannia) detection. No cross-reaction was observed with Trypanosoma cruzi strain Y or human DNA. We evaluated the performance of the assays using 49 clinical samples compared to a kDNA real-time PCR assay as the reference test. The kDNA PCR/CRISPR assay performed equally well as the reference test, with positive and negative percent agreement of 100%. The 18S PCR/CRISPR assay had high positive and negative percent agreement of 82.1% and 100%, respectively. The findings support the potential applicability of the newly developed CRISPR-based molecular tools for first-line diagnosis of Leishmania infections at the genus and L. (Viannia) subgenus levels.

Serodiagnosis and therapeutic monitoring of New-World tegumentary leishmaniasis using synthetic type-2 glycoinositolphospholipid-based neoglycoproteins

American tegumentary leishmaniasis (TL) caused by Leishmania braziliensis is characterized by a spectrum of clinical presentations, ranging from localized cutaneous ulcers (CL), mucosal (ML), or disseminated (DL) disease, to a subclinical (SC) asymptomatic form. Current diagnosis based on parasite culture and/or microscopy lacks sensitivity and specificity. Previous studies showed that patients with CL and ML have very high levels of Leishmania-specific anti-α-Gal antibodies. However, the native parasite α-Gal glycotope(s) is(are) still elusive, thus they have not yet been explored for a more accurate TL diagnosis. Using a chemiluminescent immunoassay, we evaluated the seroreactivity of TL patients across its clinical spectrum, and of endemic (EC) and nonendemic healthy controls (NEC) against three synthetic neoglycoproteins (NGP29b, NGP30b, and NGP28b), respectively comprising the L. major-derived type-2 glycoinositolphospholipid (GIPL)-1 (Galfβ1,3Manα), GIPL-2 (Galα1,3Galfβ1,3Manα), and GIPL-3 (Galα1,6Galα1,3Galfβ) glycotopes. Contrary to NGP29b and NGP30b, NGP28b exhibited high sensitivity and specificity to a CL serum pool. More importantly, NGP28b reacted strongly and specifically with individual sera from distinct clinical forms of TL, especially with SC sera, with 94% sensitivity and 97% specificity, by post-two-graph receiver-operating characteristic curve analysis. Contrary to NGP29b, NGP28b showed low cross-reactivity with Chagas disease and control (NEC/EC) sera. Additionally, seroreactivity of CL patients against NGP28b was significantly decreased after successful chemotherapy, indicating that L. braziliensis-specific anti-α-Gal antibodies may serve as an early biomarker of cure in CL. Our data also points towards the applicability of L. major type-2 GIPL-3-derived Galα1,6Galα1,3Galfβ glycotope for the serological diagnosis of American TL, particularly of the subclinical form.

Immune response to LinB13, a Lutzomyia intermedia salivary protein correlates with disease severity in tegumentary leishmaniasis

BACKGROUND

We have previously shown that seropositivity to rLinB-13, a salivary protein from Lutzomyia intermedia, predicted sand fly exposure and was associated with increased risk of developing cutaneous leishmaniasis (CL).

METHODS

Herein, we investigated the cellular immune response to saliva from Lu. intermedia, using rLinB-13 as a surrogate antigen in naturally exposed individuals presenting positive serology to LinB-13. We also investigated the response to rLinB-13 in leishmaniasis patients, displaying active ulcers and positive PCR for L. braziliensis.

RESULTS

Peripheral blood mononuclear cells (PBMCs) stimulated in vitro with rLinB-13 secreted elevated levels of IL-10, IL-4, IL-1β, IL-1α, IL-6 and chemokines (CCL3, CCL4, CCL5 and CXCL5). CL, and disseminated leishmaniasis (DL) patients displayed a significantly higher IgG response to rLinB-13, compared to healthy subjects and anti-rLinB-13 IgG was positively correlated with the number of lesions in DL patients. Positive serology to rLinB-13 was also associated with chemotherapy failure. PBMCs from DL patients stimulated with rLINB-13 secreted significantly higher levels IL-10 and IL-1β compared to CL individuals.

CONCLUSIONS

In this study, we observed an association between humoral and cellular immune response to the sand fly salivary protein rLinB-13 and disease severity in tegumentary leishmaniasis. This study brings evidence that immunity to rLinB-13 influences disease outcome in L. braziliensis infection and results indicate that positive serology to rLinB-13 IgG can be employed as marker of DL, an emerging and severe form of disease caused by L. braziliensis.

DNA-based quantification and counting of transmission stages provides different but complementary parasite load estimates: an example from rodent coccidia (Eimeria)

Background

Counting parasite transmission stages in faeces is the classical measurement to quantify “parasite load”. DNA-based quantifications of parasite intensities from faecal samples are relatively novel and often validated against such counts. When microscopic and molecular quantifications do not correlate, it is unclear whether oocyst counts or DNA-based intensity better reflects biologically meaningful concepts. Here, we investigate this issue using the example of Eimeria ferrisi (Coccidia), an intracellular parasite of house mice (Mus musculus).

Methods

We performed an infection experiment of house mice with E. ferrisi, in which the intensity of infection correlates with increased health impact on the host, measured as temporary weight loss during infection. We recorded the number of parasite transmissive stages (oocysts) per gram of faeces (OPG) and, as a DNA-based measurement, the number of Eimeria genome copies per gram of faeces for 10 days post-infection (dpi). We assessed weight loss relative to the day of experimental infection as a proxy of host health and evaluated whether DNA or oocyst counts are better predictors of host health.

Results

Absolute quantification of Eimeria DNA and oocyst counts showed similar but slightly diverging temporal patterns during 10 dpi. We detected Eimeria DNA earlier than the first appearance of oocysts in faeces. Additionally, Eimeria OPGs within each dpi did not explain parasite DNA intensity. Early dpi were characterized by high DNA intensity with low oocyst counts, while late infections showed the opposite pattern. The intensity of Eimeria DNA was consistently a stronger predictor of either maximal weight loss (1 value per animal during the infection course) or weight loss on each day during the experiment when controlling for between-dpi and between-individual variance.

Conclusions

Eimeria ferrisi oocyst counts correlate weakly with parasite intensity assessed through DNA quantification. DNA is likely partially derived from life-cycle stages other than transmissive oocysts. DNA-based intensities predict health outcomes of infection for the host more robustly than counts of transmissive stages. We conclude that DNA-based quantifications should not necessarily require validation against counts of transmissive stages. Instead, DNA-based load estimates should be evaluated as complementary sources of information with potential specific biological relevance for each host-parasite system.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05119-0.

Culture of Cutaneous Leishmania from Skin Biopsy Specimens

This protocol describes the culture of Leishmania parasites from skin biopsy samples of patients with cutaneous lesions. The use of antibiotics to prevent bacterial contamination of these cultures increases the ability of researchers to collect isolates for various research purposes, including genetic analysis and in vitro and in vivo experiments. © Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Basic Protocol: Culture of Leishmania from skin biopsy specimens.

Identification of Leishmania species by next generation sequencing of hsp70 gene

Leishmaniasis is a major public health problem worldwide. Although next generation sequencing technology has been widely used in the diagnosis of infectious diseases, it has been scarcely applied in identification of Leishmania species. The aim of this study was to compare the efficiency of MinION™ nanopore sequencing and polymerase chain reaction restriction fragment length polymorphism in identifying Leishmania species. Our results showed that the MinION™ sequencer was able to discriminate reference strains and clinical samples with high sensitivity in a cost and time effective manner without the prior need for culture.

A pilot and open trial to evaluate topical Bacterial Cellulose bio-curatives in the treatment of cutaneous leishmaniasis caused by L. braziliensis

The treatment of cutaneous leishmaniasis (CL) in Brazil using pentavalent antimony (Sb^v) is associated with a high failure rate and long time to heal. Moreover, standard Sb^v treatment cures only 50-60% of the cases. In this pilot clinical trial, we evaluated the topical use of bacterial cellulose (BC) bio-curatives + Sb^v in the treatment of CL caused by L. braziliensis, in Bahia, Brazil. A total of 20 patients were randomized in two groups assigned to receive either parenteral Sb^v alone or parenteral Sb^v plus topically applied BC bio-curatives. CL patients treated with Sb^v + topical BC bio-curatives had a significantly higher cure rate at 60 days post initiation of treatment compared to CL patients treated with Sb^v alone (P=0.01). At day 90 post initiation of treatment, cure rate was similar in the two groups as was overall healing time. Adverse effects or local reactions to topical BC application were not observed. This pilot trial shows that the potential use of a combined therapy consisting of topical BC bio-curatives and parenteral Sb^v in favoring healing of CL lesions caused by L. braziliensis, at an early time point.

Visceral leishmaniasis and COVID-19 coinfection - A case report

As the COVID-19 pandemic spreads across the globe, it will undoubtedly cross paths with long endemic infectious diseases in different areas. Interactions between SARS-CoV2 and well-known pathogens will likely give rise to unfamiliar clinical presentations, depending on complex and as yet unknown immunological interactions. We present a case of coinfection with COVI19 and visceral leishmaniasis and discuss recent reports regarding coexistence of SARS-CoV2 and Leishmania spp. to date.

Developing, Modifying, and Validating a TaqMan Real-Time PCR Technique for Accurate Identification of Leishmania Parasites Causing Most Leishmaniasis in Iran

Many laboratory methods are used to diagnose leishmaniasis because it is characterized by varied symptoms and caused by different Leishmania species. A quantitative real-time PCR method based on a TaqMan probe was developed and modified for accurate identification of human cutaneous leishmaniasis (caused by Leishmania major or Leishmania tropica) from endemic areas of Iran. Two gene regions of amino acid permease 3 (AAP3) and cytochrome oxidase II (COII) were considered. Six new sets of species-specific primers and probes were designed. A total of 123 samples were examined and employed to evaluate and validate real-time PCR. According to parasitic load of the genesig^®Leishmania Advanced Standard Kit, a serial dilution of purified plasmid (2–2×10⁷ copies/reaction) was prepared under the same conditions for both genes. Specific primers and probes were able to detect three and six parasite copies in AAP3 and COII genes, respectively, and were able to detect three copies of parasites for L. major and L. tropica. The sensitivities of the reference kit and our method were 98.7 and 98.1%, respectively, and specificity was 100% for detecting parasite genomes in all assays. Designed primers and probes performed well in terms of efficiency and regression coefficient. For AAP3 and COII genes, respectively, the linear log range was 7 and the correlation coefficient (R²) was 0.749 and 0.996 for the reference kit using the standard generated curve and 0.98 and 0.96 with serial dilutions of parasite DNA. This research detected L. major and L. tropica definitely and opens the horizon for the other scientists in the multiplex reactions in designing and optimization of the conditions in silico and in vivo.

Development of Quantitative Rapid Isothermal Amplification Assay for Leishmania donovani

Quantification of pathogen load, although challenging, is of paramount importance for accurate diagnosis and clinical management of a range of infectious diseases in a point-of-need testing (PONT) scenario such as in resource-limited settings. We formulated a quantification approach to test the standard-curve based absolute quantification ability of isothermal recombinase polymerase amplification (RPA) assay. As a test of principle, a 10-fold dilution series of Leishmania donovani (LD) genomic DNA prepared in nuclease-free-water (NFW), and from culture-spiked-blood (CSB) were tested, and a 15 min assay was performed. A modified algorithm was formulated to derive the detection outcome. The threshold-record times (Tr) in seconds thus obtained were plotted against the initial load of parasite genomes for log-linear regression analysis. The quantitative RPA (Q-RPA) assay was further evaluated against a LD quantitative (q)-PCR assay with DNA extracted from visceral and post-Kala-azar dermal leishmaniasis case specimens and stratified into different ranges of threshold cycle (Ct). The best-fitted regression models were found linear with mean r²/root mean square error (RMSE) values of residual points (in seconds) estimated as 0.996/8.063 and 0.992/7.46 for replicated series of NFW and CSB, respectively. In both series, the lower limit of detection reached less than 0.1 parasite genome equivalent DNA. Absolute agreement between Q-RPA and LD-qPCR was found for test positivity, and strong positive correlations were observed between the Tr and Ct values (r = 0.89; p < 0.0001) as well as between the absolute parasite loads (r = 0.87; p < 0.0001) quantified by respective assays. The findings in this very first Q-RPA assay for leishmaniasis are suggestive of its potential in monitoring LD load in clinical specimens, and the development of rapid Q-RPA assays for other infectious diseases.

Impaired Th1 Response Is Associated With Therapeutic Failure in Patients With Cutaneous Leishmaniasis Caused by Leishmania braziliensis

BACKGROUND

Leishmania skin test (LST) evaluates the delayed type hypersensitivity to Leishmania antigens (LA) and has been used for diagnosis of cutaneous leishmaniasis (CL). In CL patients LST is usually positive but a small percentage have negative LST. The aim of this study was to determine the clinical and immunologic features and response to antimony therapy in LST-negative CL patients.

METHODS

We compare the clinical presentation, response to therapy, and immune response of CL patients with negative vs positive LST.

RESULTS

The clinical presentation was similar in both groups but LST-negative patients had a lower cure rate. In the lesions, LST-negative patients displayed less inflammation and necrosis, and higher frequency of CD8+ T cells. Mononuclear cells from LST-negative patients had a poor T helper 1 cell (Th1) response but levels of interleukin-1β (IL-1β), IL-6, IL-17, granzyme B, and metalloproteinase-9 (MMP-9) were similar to the LST-positive group upon stimulation with LA. Leishmania internalization and killing by macrophages were similar in both groups. Cure of disease was associated with restoration of Th1 response.

CONCLUSIONS

In LST-negative patients, impaired Th1 response is associated with therapeutic failure. Increased frequency of CD8+ T cells and high production of inflammatory cytokines, granzyme B, and MMP-9 contributes to immunopathology.

The Influence of Infection by Different Leishmania (Viannia) braziliensis Isolates on the Pathogenesis of Disseminated Leishmaniasis

Disseminated Leishmaniasis (DL) is an emerging and severe form of Leishmania (Viannia) braziliensis infection defined by the presence of 10 and up to more than 1,000 skin lesions. The mechanisms underlying parasite dissemination remain unknown. Genotypic differences among species of L. braziliensis have been associated with different clinical forms of disease. The present work compared the function of monocytes obtained from patients with cutaneous leishmaniasis (CL) and DL in response to infection with L. braziliensis isolates of both these two clinical forms of disease. Mononuclear cells obtained from DL and CL patients were infected with different L. braziliensis isolates, and numbers of infected cells, parasite load, respiratory burst, TLR2 and TLR4 expression and cytokine production were evaluated. DL isolates infected more monocytes, induced greater respiratory burst, and more cytokine production compared to isolates from CL patients regardless of the origin of monocytes (DL or CL). However, greater parasite multiplication and higher TLR2 and TLR4 expression were seen in monocytes from DL patients compared to CL following infection with DL isolates. Our results indicate the participation of both parasite genotype and host factors in the pathogenesis of DL.

Canine Leishmaniasis in Morocco: A Descriptive Prospective Clinical Study

Canine leishmaniasis (CanL) is a zoonotic vector-borne disease that is endemic in the Mediterranean Basin including Morocco. Dogs play a major epidemiological role in this zoonosis as reservoir hosts. This study investigated the clinical manifestations of CanL in dogs naturally infected with Leishmania infantum. A total of 96 dogs presented to the Small Animal Clinic of the Hassan II Agronomy and Veterinary Institute (IAV Hassan II) of Rabat, Morocco, and were tested by RT-PCR and/or serology. Among them, 32 (33.3%) were positive to Leishmania infantum infection. The majority of the positive dogs (93.7%) came from urban areas. Most of them were male (62.5%) and purebreds (65.6%), were aged between 3 and 7 years (71.8%), and had outside activities (guarding, hunting, livestock guarding, and service activities) (71.8%) and all of them were living exclusively outdoor or had free access to the outdoor environment. Lymphadenomegaly (81.2%), dermatological disorders (65.6%) (mostly exfoliative dermatitis), weight loss (59.3%), exercise intolerance (56.2%), anorexia (28.1%), hyporexia (15.6%), and ocular lesions (28.1%) were the most frequent clinical signs and complaints recorded. Anemia and hyperproteinemia due to hyperglobulinemia were observed in 68.7% and 72.7% of the cases, respectively. These results suggest that CanL leads to various nonspecific clinical signs as described previously, making the diagnosis challenging. Since CanL is endemic in Morocco, it should be recommended to systematically test dogs displaying clinical signs compatible with this disease and to regularly screen asymptomatic at-risk dogs. It is also crucial to educate dog owners about the zoonotic aspect of the disease and to encourage intersectorial collaboration following the “One Health” concept, in order to contribute to a more effective control/prevention of human and canine leishmaniasis.

Influence of Obesity on Clinical Manifestations and Response to Therapy in Cutaneous Leishmaniasis Caused by Leishmania braziliensis

BACKGROUND

Cutaneous leishmaniasis (CL) caused by Leishmania braziliensis is characterized by a single ulcer or multiple cutaneous lesions with raised borders. Cure rates <60% are observed in response to meglumine antimoniate therapy. We investigated the impact of obesity on CL clinical presentation and therapeutic response.

METHODS

A total of 90 age-matched patients with CL were included (30 obese, 30 overweight, and 30 with normal body mass index [BMI]). CL was diagnosed through documentation of L. braziliensis DNA by polymerase chain reaction or identification of amastigotes in biopsied skin-lesion samples. Serum cytokine levels were determined by chemiluminescence. Antimony therapy with Glucantime (Sanofi-Aventis; 20 mg/kg/day) was administered for 20 days.

RESULTS

Obese CL patients may present hypertrophic ulcers rather than typical oval, ulcerated lesions. A direct correlation between BMI and healing time was noted. After 1 course of antimony, cure was achieved in 73% of patients with normal BMI, 37% of overweight subjects, yet just 18% of obese CL patients (P < .01). Obese CL cases additionally presented higher leptin levels than overweight patients or those with normal BMI (P < .05).

CONCLUSIONS

Obesity modifies the clinical presentation of CL and host immune response and is associated with greater failure to therapy.

Influence of Intestinal Helminth Burden on Clinical Manifestations, Therapeutic Response, and Leishmania braziliensis Load in Patients with New World Cutaneous Leishmaniasis

Leishmania braziliensis is the most important cause of cutaneous leishmaniasis (CL) in the Americas. A Th1-type immune response is required to control Leishmania infection, but an exaggerated inflammatory response leads to the development of ulcers seen in CL. Infection with intestinal helminths has the potential to inhibit the Th1 response in a manner that depends both on the species of helminth present as well as the burden of helminthiasis. We conducted a prospective cohort study of CL patients from an endemic area between January and December 2017 with either negative or high intestinal helminth burden to characterize relationships between helminth burden, L. braziliensis quantification within CL lesions, clinical aspects of CL, and therapeutic response. Of 234 participants with leishmaniasis who underwent stool examination at the time of diagnosis, 45% had detectable helminth infection. The overall cure rate after 90 days was 66%, with a median time to resolution of disease of 40 days (interquartile range: 30-65 days). There was no significant association between the type of helminth infection or the magnitude of intestinal helminth burden at the time of diagnosis and L. braziliensis genomic DNA (gDNA) detected in biopsies from CL lesions. Likewise, there was no association between helminth burden and response to treatment after 90 days. Considering quantification of parasite DNA in CL lesions, participants who were cured at 90 days had a median of 0.017 ng/mg gDNA, and participants who failed therapy had a median of 0.091 ng/mg gDNA (P = 0.03). The results indicate that cutaneous Leishmania load may influence therapeutic response in CL.

The Leishmania antigen-specific pro-inflammatory response in cutaneous leishmaniasis is linked to disease progression but not to the therapeutic failure of pentavalent antimonials

High levels of pro-inflammatory cytokines in cutaneous leishmaniasis patients are associated with tissue damage and ulcer development. We found higher levels of TNF and IL-1β in peripheral blood mononuclear cell supernatants in response to soluble Leishmania antigen in individuals with a longer duration of disease. In addition, L. braziliensis-infected patients with a longer disease progression before treatment presented a shorter time to cure after treatment onset. No associations were found between the levels of the pro-inflammatory cytokines IL-6, TNF and IL-1-β and patients' response to pentavalent antimony treatment. Our data suggest that while the Leishmania antigen-specific pro-inflammatory cytokines investigated may lead to ulcer development, they do not influence therapeutic failure in cutaneous leishmaniasis patients.

The Inflammatory Effects of Dietary Lipids Regulate Growth of Parasites during Visceral Leishmaniasis

Visceral leishmaniasis is a potentially fatal disease caused by the protozoon Leishmania donovani or L. infantum (Li). Although previous studies revealed that high lipid intake reduces parasite burdens in Leishmania donovani-infected mice, the specific contributions of dietary lipids to Li-associated pathogenesis are not known. To address this, we evaluated parasite growth, liver pathology, and transcriptomic signatures in Li-infected BALB/c mice fed either a control, high-fat, high-cholesterol, or high-fat–high-cholesterol diet. Using quantitative PCR (qPCR), we observed significantly reduced liver parasite burdens in mice fed the high-fat–high-cholesterol diet compared to mice fed the control diet. In contrast to the liver, parasite expansion occurred earlier in the spleens of mice fed the experimental diets. Histological examination revealed an intense inflammatory cell infiltrate in livers predominantly composed of neutrophils caused by the high-fat–high-cholesterol diet specifically. After 8 weeks of infection (12 weeks of diet), Illumina microarrays revealed significantly increased expression of transcripts belonging to immune- and angiogenesis-related pathways in livers of both uninfected and Li-infected mice fed the high-fat–high-cholesterol diet. These data suggest that increased fat and cholesterol intake prior to Li infection leads to a hepatic inflammatory environment and thus reduces the parasite burden in the liver. Defining inflammatory signatures as well as pathology in the liver may reveal opportunities to modify the therapeutic approach to Li infection.

IMPORTANCE Leishmaniasis is a spectrum of diseases caused by Leishmania species protozoa that is most common in warm climates, coinciding with impoverished regions. Visceral leishmaniasis is a potentially fatal disease in which parasites infect reticuloendothelial organs and cause progressive wasting and immunocompromise. The distribution and demographics of visceral leishmaniasis have changed over recent years, coinciding with modernizing societies and the increased availability of Western diets rich in lipid content. We report here that increased dietary fat and cholesterol intake affected disease pathogenesis by increasing inflammation and reducing localized parasite burdens in the liver. These diet-induced changes in disease pathogenesis might explain in part the changing epidemiology of visceral leishmaniasis. A relationship between diet and inflammatory responses may occur in leishmaniasis and other microbial or immune-mediated diseases, possibly revealing opportunities to modify the therapeutic approach to microbial infections.

Molecular Diagnosis of Leishmaniasis: Quantification of Parasite Load by a Real-Time PCR Assay with High Sensitivity

Real-time PCR was developed to quantify Leishmania infantum kinetoplast DNA and optimized to achieve a sensitivity of 1 parasite/mL. For this purpose, we cloned the conserved kDNA fragment of 120 bp into competent cells and correlated them with serial dilutions of DNA extracted from reference parasite cultures calculating that a parasite cell contains approximately 36 molecules of kDNA. This assay was applied to estimate parasite load in clinical samples from visceral, cutaneous leishmaniasis patients and infected dogs and cats comparing with conventional diagnosis. The study aimed to propose a real-time PCR for the detection of Leishmania DNA from clinical samples trying to solve the diagnostic problems due to the low sensitivity of microscopic examination or the low predictive values of serology and resolve problems related to in vitro culture. The quantitative PCR assay in this study allowed detection of Leishmania DNA and quantification of considerably low parasite loads in samples that had been diagnosed negative by conventional techniques. In conclusion, this quantitative PCR can be used for the diagnosis of both human, canine and feline Leishmaniasis with high sensitivity and specificity, but also for evaluating treatment and the endpoint determination of leishmaniasis.

Diagnosis and Causative Species of Visceral Leishmaniasis in Southwest Saudi Arabia

Visceral leishmaniasis (VL) is the most severe clinical form of the disease and has been reported in the Jazan region of southwest Saudi Arabia. This study aimed to diagnose VL by real-time polymerase chain reaction (PCR) and the direct agglutination test (DAT) and to identify the causative Leishmania species. A total of 80 participants, including 30 suspected VL patients, 30 healthy endemic control individuals, and 20 malaria disease controls, were enrolled in this study. Blood samples were collected and tested for Leishmania DNA by real-time PCR and for antibody by the DAT. Sequencing of some amplified PCR products was used to identify the causative Leishmania species. The diagnosis of VL was successfully achieved by both real-time PCR and by DAT with 100% sensitivity. Leishmania donovani and Leishmania infantum species were detected by sequencing both by the kDNA and ITS1 target genes, followed a BLASTn search. The detection of VL antibody by the DAT followed by the confirmatory detection of Leishmania DNA in patient blood by PCR could promote the adoption of the much less invasive and more sensitive methods for the routine diagnosis of VL. Further study with high sample volume to evaluate the PCR and the DAT are needed, to generate more robust evidence. Based on the sequencing results, emerging studies on VL should focus on the causative Leishmania species, reservoirs, and vectors that are important in the study area.

Sand fly identification and screening for Leishmania spp. in six provinces of Thailand

Background

Phlebotomine sand flies are vectors of Leishmania spp. At least 27 species of sand flies have been recorded in Thailand. Although human leishmaniasis cases in Thailand are mainly imported, autochthonous leishmaniasis has been increasingly reported in several regions of the country since 1999. Few studies have detected Leishmania infection in wild-caught sand flies, although these studies were carried out only in those areas reporting human leishmaniasis cases. The aim of this study was therefore to identity sand fly species and to investigate Leishmania infection across six provinces of Thailand.

Methods

Species of wild-caught sand flies were initially identified based on morphological characters. However, problems identifying cryptic species complexes necessitated molecular identification using DNA barcoding in parallel with identification based on morphological characters. The wild-caught sand flies were pooled and the DNA isolated prior to the detection of Leishmania infection by a TaqMan real-time PCR assay.

Results

A total of 4498 sand flies (1158 males and 3340 females) were caught by trapping in six provinces in four regions of Thailand. The sand flies were morphologically classified into eight species belonging to three genera (Sergentomyia, Phlebotomus and Idiophlebotomus). Sergentomyia iyengari was found at all collection sites and was the dominant species at most of these, followed in frequency by Sergentomyia barraudi and Phlebotomus stantoni, respectively. DNA barcodes generated from 68 sand flies allowed sorting into 14 distinct species with 25 operational taxonomic units, indicating a higher diversity (by 75%) than that based on morphological identification. Twelve barcoding sequences could not be assigned to any species for which cytochrome c oxidase subunit I sequences are available. All tested sand flies were negative for Leishmania DNA.

Conclusions

Our results confirm the presence of several sand fly species in different provinces of Thailand, highlighting the importance of using DNA barcoding as a tool to study sand fly species diversity. While all female sand flies tested in this study were negative for Leishmania, the circulation of Leishmania spp. in the investigated areas cannot be ruled out.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04856-6.

High Anti-Leishmania IgG Antibody Levels Are Associated With Severity of Mucosal Leishmaniasis

Background

Mucosal leishmaniasis (ML), the most inflammatory form of tegumentary leishmaniasis, is predominantly caused by Leishmania braziliensis. The disease is characterized by the development of lesions, mainly in the nasal mucosa. An exacerbated inflammatory response has been associated with the presence of destructive and disfiguring lesions, with stages of severity ranging from small nodulations to the complete destruction of the nasal pyramid architecture. As Leishmania is an intracellular parasite, most immunological studies have emphasized the cell-mediated immune response, while relatively few studies aimed to investigate the role antibodies in protection against, or the pathology of ML.

Methods

Patients with a confirmed diagnosis of ML were classified according to clinical staging criteria. Serum levels of Leishmania-specific IgG, IgG1 and IgG2 antibodies were determined by ELISA before and after treatment with antimony or antimony plus pentoxifylline.

Results

Patients in stages IV and V produced higher concentrations of IgG and IgG1 antibodies when compared to those in stage I and II. Significant reductions were seen in the concentrations of IgG and IgG2 antibodies in most patients who responded well to treatment.

Conclusions

Our data demonstrate an association between IgG antibody titers and the severity of mucosal disease. The observed reduction in antibody production after successful treatment in most patients preliminarily indicates that these tests can be used to aid in the assessment of therapeutic response.

Epidemiological and pathological characteristics of Cutaneous Leishmaniasis from Baluchistan Province of Pakistan

Cutaneous Leishmaniasis (CL) is considered a neglected tropical disease which in Pakistan can now be considered as a growing public health problem. The exact figures on the magnitude of the disease are lacking both at the national and regional level and only a few health centres are available for diagnosis of CL. The present study was designed to identify the epidemiology of CL infection from August 2018 to December 2019 and to assess clinical aspects of CL in Baluchistan Province of Pakistan. A total of 4072 clinically suspected CL cases were analysed statistically. The highest number of CL cases were reported in May, followed by April, January and then July, February and June and the lowest number of cases were observed in March and November. The highest prevalence rate was found in males where 38% of reported cases were aged 0-9 years. The majority (24.4%) of lesions were found on the hands followed by the face in which cheeks, ears and nose were the effected organs. About 50% of the participants have single lesion while 14% of the participants had two and nearly 3% of the participants have six lesions. The atypical clinical presentations were observed in Baluchistan and common unusual presentations were lupus erythematosus. The study findings suggest that more epidemiological studies and health education campaigns are needed for the population awareness regarding CL in Baluchistan. It is recommended that risk factors should be evaluated to establish control and management strategies to prevent disease at the individual and community level.

Newly developed SYBR Green-based quantitative real-time PCRs revealed coinfection evidence of Angiostrongylus cantonensis and A. malaysiensis in Achatina fulica existing in Bangkok Metropolitan, Thailand

Angiostrongylus cantonensis is a well-known pathogen causing eosinophilic meningitis associated with angiostrongyliasis. Humans, as accidental hosts, are infected by consuming undercooked snails containing third-stage larvae. A. malaysiensis is closely related to A. cantonensis and has been described as a potential human pathogen. The two species distribution was recently reported to overlap in the same endemic area, particularly in the Indochina Peninsula. Similar morphological characteristics of the third-stage larva in the snail-intermediate host often lead to misidentification of the two species. Thus, we aimed to develop a sensitive and specific method to detect and discriminate Angiostrongylus third-stage larva by designing species-specific primers based on the mitochondrial cytochrome b gene. We developed the SYBR Green quantitative real-time PCR (qPCR) method for two species-specific detection assays, which could be conducted simultaneously. The method was subsequently employed to detect and identify third-stage larvae of Angiostrongylus isolated from infected Achatina fulica collected from six public parks in Bangkok Metropolitan, Thailand. The method was also a preliminary applied to detect parasite tissue debris in the patients' cerebrospinal fluid (CSF). SYBR Green qPCRs quantitatively detected approximately 10⁻⁴ ng of genomic DNA from one larva, facilitating species-specific detection. Based on the pools of third-stage larvae isolated individually from the tissue of each infected A. fulica collected from the public parks, the qPCR results revealed that A. malaysiensis was the predominant species infecting 5.26% of the collected snails. In comparison, coinfection between A. malaysiensis and A. cantonensis was 5.97%, and no single infection of A. cantonensis was detected in A. fulica. Our SYBR Green qPCR method is a useful and inexpensive technique for A. cantonensis and A. malaysiensis discrimination, and the method has sufficient sensitivity to detect isolated larvae from a snail-intermediate host. The ratio of A. cantonensis and A. malaysiensis larvae infecting the snails can also be estimated simultaneously. Our qPCRs can be employed in a molecular survey of A. cantonensis and A. malaysiensis within intermediate hosts and for clinical diagnosis of angiostrongyliasis with CSF specimens in future studies.

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The SYBR Green qPCRs were developed to detect and discriminate Angiostrongylus third-stage larvae by designing species-specific primers based on the mitochondrial cytochrome b gene.

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A. malaysiensis is the predominant species in Bangkok Metropolitan, Thailand.

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Coinfection between A. cantonensis and A. malaysiensis has occurred in the Achatina fulica population in Bangkok

Amentoflavone as an Ally in the Treatment of Cutaneous Leishmaniasis: Analysis of Its Antioxidant/Prooxidant Mechanisms

Treatment of leishmaniasis is a challenging subject. Although available, chemotherapy is limited, presenting toxicity and adverse effects. New drugs with antileishmanial activity are being investigated, such as antiparasitic compounds derived from plants. In this work, we investigated the antileishmanial activity of the biflavonoid amentoflavone on the protozoan Leishmania amazonensis. Although the antileishmanial activity of amentoflavone has already been reported in vitro, the mechanisms involved in the parasite death, as well as its action in vivo, remain unknown. Amentoflavone demonstrated activity on intracellular amastigotes in macrophages obtained from BALB/c mice (IC₅₀ 2.3 ± 0.93 μM). No cytotoxicity was observed and the selectivity index was estimated as greater than 10. Using BALB/c mice infected with L. amazonensis we verified the effect of an intralesional treatment with amentoflavone (0.05 mg/kg/dose, in a total of 5 doses every 4 days). Parasite quantification demonstrated that amentoflavone reduced the parasite load in treated footpads (46.3% reduction by limiting dilution assay and 56.5% reduction by Real Time Polymerase Chain Reaction). Amentoflavone decreased the nitric oxide production in peritoneal macrophages obtained from treated animals. The treatment also increased the expression of ferritin and decreased iNOS expression at the site of infection. Furthemore, it increased the production of ROS in peritoneal macrophages infected in vitro. The increase of ROS in vitro, associated with the reduction of NO and iNOS expression in vivo, points to the antioxidant/prooxidant potential of amentoflavone, which may play an important role in the balance between inflammatory and anti-inflammatory patterns at the infection site. Taken together these results suggest that amentoflavone has the potential to be used in the treatment of cutaneous leishmaniasis, working as an ally in the control and development of the lesion.

High resolution melting assay in discrimination of the main etiologic agents of leishmaniasis in Iran

Background and Objectives:

The three old world Leishmania species i.e., L. major, L. tropica, and L. infantum are considered as potential etiological agents of the various clinical forms of leishmaniasis in Iran. Different species co-exist in some areas. Accurate differentiation between the species is essential for choosing an appropriate therapy. Conventional and gold standard methods for the detection and characterization of parasites are time-consuming, laborious, and have low sensitivity. A polymerase chain reaction followed by high resolution melting (PCR-HRM) analysis has been employed for detection and species identification. Most of the studies suffer from the use of multiple targets and/or requiring more than one reaction to identify a single sample. The present study aimed to design a PCR method based on the amplification of kinetoplast DNA minicircles (kDNA) and HRM analysis of the amplicons for rapid discrimination of the three mentioned species.

Materials and Methods:

DNA from reference strains including L. major, L. tropica, and L. infantum and fifty-eight strains subjected to PCR-HRM analysis targeting kDNA. All the samples were also analyzed by conventional kDNA-PCR.

Results:

The PCR-HRM analysis allowed discrimination between the three Old World species. The normalized HRM curves for the amplicons of kDNA indicated a unique and repeatable melting plot for each species, even in combination with human and mouse genomic DNA. Conventional kDNA-PCR could not properly discriminate L. tropica from L. infantum.

Conclusion:

PCR-HRM analysis of kDNA proved to be fast and accurate for discrimination of L. major, L. tropica, and L. infantum.

Anti-Leishmania IgG is a marker of disseminated leishmaniasis caused by Leishmania braziliensis

BACKGROUND

In this study, we determined the accuracy of anti-Leishmania IgG and IgG subclasses to distinguish clinical forms of American tegumentary leishmaniasis (ATL) and and determined the relationship between antibodies levels with cytokine production and severity of ATL.

METHODS

Participants were 40 patients with cutaneous leishmaniasis (CL), 20 patients with mucosal leishmaniasis (ML), 20 patients with disseminated leishmaniasis (DL), and 20 individuals with subclinical Leishmania braziliensis infection (SC). Diagnosis was performed by DNA of L. braziliensis or IFN-γ production in SC. IgG and subclasses of IgG to soluble Leishmania antigen and cytokine levels in supernatants of mononuclear cells were detected by ELISA.

RESULTS

IgG was detected in 95%, 95%, and 100% of patients with CL, ML, and DL, respectively. Higher levels of anti-Leishmania IgG and IgG2 were seen in DL compared to CL, ML, and SC. ROC analysis confirmed the ability of IgG to distinguish DL from the other clinical forms. A direct correlation was observed between IgG titers and levels of IFN-γ and CXCL10 in CL and DL, and IgG2 antibodies were correlated with the number of lesions in DL.

CONCLUSIONS

High anti-Leishmania IgG and IgG2 levels are characteristic of DL, and while IgG was correlated with pro-inflammatory cytokines, IgG2 was direct correlated with the number of lesions.

Leishmania donovani infection suppresses Allograft Inflammatory Factor-1 in monocytes and macrophages to inhibit inflammatory responses

Macrophages and monocytes are important for clearance of Leishmania infections. However, immune evasion tactics employed by the parasite results in suppressed inflammatory responses, marked by deficient macrophage functions and increased accumulation of monocytes. This results in an ineffective ability to clear parasite loads. Allograft Inflammatory Factor-1 (AIF1) is expressed in myeloid cells and serves to promote immune responses. However, AIF1 involvement in monocyte and macrophage functions during parasitic infections has not been explored. This study now shows that Leishmania donovani inhibits AIF1 expression in macrophages to block pro-inflammatory responses. Mice challenged with the parasite had markedly reduced AIF1 expression in splenic macrophages. Follow-up studies using in vitro approaches confirmed that L. donovani infection in macrophages suppresses AIF1 expression, which correlated with reduction in pro-inflammatory cytokine production and increased parasite load. Ectopic overexpression of AIF1 in macrophages provided protection from infection, marked by robust pro-inflammatory cytokine production and efficient pathogen clearance. Further investigations found that inhibiting AIF1 expression in bone marrow cells or monocytes impaired differentiation into functional macrophages. Collectively, results show that AIF1 is a critical regulatory component governing monocyte and macrophage immune functions and that L. donovani infection can suppress the gene as an immune evasion tactic.

Evaluation of a kDNA-Based qPCR Assay for the Detection and Quantification of Old World Leishmania Species

The parasite protozoan Leishmania, the causative agent of leishmaniasis, includes two subgenera of medical interest: Leishmania (Leishmania) and Leishmania (Viannia). Parasite species detection and characterization is crucial to choose treatment protocols and to monitor the disease evolution. Molecular approaches can speed up and simplify the diagnostic process. In particular, several molecular assays target the mitochondrial DNA minicircle network (kDNA) that characterizes the Leishmania genus. We previously proposed a qPCR assay targeting kDNA, followed by high resolution melt (HRM) analysis (qPCR-ML) to distinguish L. (L.) infantum and L. (L.) amazonensis from L. Viannia species. Successively, this assay has been integrated with other qPCR assays, to differentiate L. (L.) infantum, L. (L.) amazonensis and L. (L.) mexicana. In this work, we tested the applicability of our qPCR-ML assay on L. (L.) donovani, L. (L.) major, L. (L.) tropica and L. (L.) aethiopica, showing that the qPCR-ML assay can also amplify Old World species, different from L. (L.) infantum, with good quantification limits (1 × 10^-4-1 × 10^-6 ng/pcr tube). Moreover, we evaluated 11 L. (L.) infantum strains/isolates, evidencing the variability of the kDNA minicircle target molecules among the strains/isolates of the same species, and pointing out the possibility of quantification using different strains as reference. Taken together, these data account for the consideration of qPCR-ML as a quantitative pan-Leishmania assay.

Diabetes Modifies the Clinic Presentation of Cutaneous Leishmaniasis

BACKGROUND

Cutaneous leishmaniasis (CL) caused by L. braziliensis is characterized by 1 or multiple well-limited ulcerated lesions. Diabetes mellitus (DM) impairs neutrophil and monocyte function, and there is a report of vegetative lesions in a patient with both diseases in Morocco. Here we evaluate the influence of DM on clinical manifestations, immune response, and in the treatment of CL.

METHODS

The participants were 36 DM patients with CL and 36 patients with CL without DM, matched by age and gender. The diagnosis of CL was performed by documentation of DNA of L. braziliensis by polymerase chain reaction in the lesion biopsy and histopathologic findings. All patients were treated with Glucantime (Sanofi-Aventis) 20 mg/kg of weight per day for 20 days.

RESULTS

There was no difference in the majority of the clinical variables between the groups, and the cure rate in patients with CL and DM (67%) was similar to that observed in CL patients (56%; P ˃ .05). The most important finding was the documentation that 36% of the patients with DM and CL had atypical cutaneous lesions characterized by large superficial ulcers without defined borders. High levels of interferon-γ, tumor necrosis facor, and interleukin-1β were detected in the supernatants of mononuclear cells stimulated with Leishmania antigen in patients with DM and atypical CL. Moreover, while cure was observed in only 33% of the patients with DM and atypical CL lesions, it was observed in 85% of patients with typical lesions (P < .05).

CONCLUSIONS

DM modifies the clinical presentation of CL, enhances pro-inflammatory cytokine production, and impairs response to antimony therapy.