Genes and Susceptibility to Leishmaniasis

Polygenic TB control and the sequence of innate/adaptive immune responses to infection: MHC-II alleles determine the size of the S100A8/9-producing neutrophil population

Among several quantitative trait loci involved in tuberculosis (TB) control in mice, one was mapped within the chromosome 17 segment occupied by the H2 complex and another within the chromosome 3 segment comprising the S100A8/9 genes, which encode neutrophil inflammatory factor S100A8/9. Previously, we developed a panel of H2-congenic mouse strains differing by small segments of the major histocompatibility complex Class II (MHC-II) region from TB-susceptible H2j mice transferred onto the genetic background of the TB-resistant C57BL/6 (H2b) strain. Susceptible B6.I-9.3 mice differ from B6 progenitors by the alleles of their only classical MHC-II H2-Aβ gene. The goals of the present study were to: (i) comprehensively characterise the differences in TB-related phenotypes between mice of the two strains and (ii) decipher interactions between the H2-Aβ and S100A8/9 genes. Here, we describe the dynamics of TB-related phenotypes differentiating B6.I-9.3 and B6 mice (colony forming units counts, histopathology, lung immune cell infiltration and cytokine profiles). We show that disproportionally diminished CD4+ T-cell population, an enlarged S100A8/9-positive neutrophil population and higher S100A8/9 serum levels in B6.I-9.3 mice collectively form the 'susceptible' phenotype before infection. An increase in IL-17 and a decrease in intrferon-gamma production by CD4+ T-cells in these mice provide a mechanistic explanation of this phenotype. Using F2 segregation analysis, we show that the number of S100A8/9-producing neutrophils in lungs and spleens and the proportion of Th17 CD4+ T-cells in lungs are significantly lower in the presence of the MHC-II dominant 'resistant' b allele compared to the recessive 'susceptible' j/j genotype. This provides direct genetic evidence that MHC-II-regulated CD4+ T-cell landscapes determine neutrophil abundance before infection, an important pathogenic factor in TB immunity.

The role of cytotoxic T-Lymphocyte antigen-4+49A/G gene polymorphism in cutaneous leishmaniasis

BACKGROUND

Cutaneous Leishmaniasis (CL) is a parasitic disease caused by intracellular protozoa belonging to the Leishmania genus. In endemic areas, only a proportion of exposed subjects develop the disease under almost similar circumstances, reflecting the role of genetic inheritance in resistance and susceptibility to infection. This study aimed To evaluate the association of cytotoxic T-lymphocyte antigen-4 (CTLA-4)+49G/A single nucleotide polymorphism (SNP) with incidence and severity of CL.

METHODS

This cross-sectional study includes 110 patients with confirmed CL (60 newly diagnosed and 50 patients undergoing treatment) and 60 healthy subjects of similar age and sex. The CTLA-4 gene fragment corresponding to CTLA-4+49G/A polymorphism was amplified and genotyped using tetra primer amplification refractory mutation- polymerase chain reaction system (TARMS-PCR) methods. Soluble CTLA-4 (sCTLA-4) was estimated in the serum using an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The GG genotype of CTLA-4+49G/A polymorphism was significantly more common in controls than in patients (OR = 0.11, 95% CI = 0.02-0.58, p = 0.009). At allelic level, G allele was much more common in controls than in patients (30.83% vs. 17.73%) with a significant difference (OR = 2.07, 95% CI = 1.23-3.48, p = 0.006). However, there was no significant difference in the frequency of genotypes and alleles between newly diagnosed and treated patients. Median serum concentration of sCTLA-4 in newly diagnosed patients was 72.6 pg/ml (range 15.6-127 pg/ml) which was higher than either controls (median = 16.3 pg/ml, range 0.8-48.5 pg/ml) or treated patients (median = 17.9 pg/ml, range 2.9-74.7 pg/ml) with highly significant differences, while there was no significant difference between controls and treated patients. The median sCTLA-4 level was comparable across genotypes of the CTLA-4+49G/A polymorphism, with no significant difference.

CONCLUSIONS

Collectively, these results show the protective role of allele G of the SNP CTLA-4+49G/A against CL and increased serum sCTLA-4 in newly diagnosed CL patients, which may be used as an additional diagnostic tool. Different genotypes of the CTLA-4+49G/A polymorphism have no effect on sCLTA-4 serum levels.

Genomic Analysis of Colombian Leishmania panamensis strains with different level of virulence

The establishment of Leishmania infection in mammalian hosts and the subsequent manifestation of clinical symptoms require internalization into macrophages, immune evasion and parasite survival and replication. Although many of the genes involved in these processes have been described, the genetic and genomic variability associated to differences in virulence is largely unknown. Here we present the genomic variation of four Leishmania (Viannia) panamensis strains exhibiting different levels of virulence in BALB/c mice and its application to predict novel genes related to virulence. De novo DNA sequencing and assembly of the most virulent strain allowed comparative genomics analysis with sequenced L. (Viannia) panamensis and L. (Viannia) braziliensis strains, and showed important variations at intra and interspecific levels. Moreover, the mutation detection and a CNV search revealed both base and structural genomic variation within the species. Interestingly, we found differences in the copy number and protein diversity of some genes previously related to virulence. Several machine-learning approaches were applied to combine previous knowledge with features derived from genomic variation and predict a curated set of 66 novel genes related to virulence. These genes can be prioritized for validation experiments and could potentially become promising drug and immune targets for the development of novel prophylactic and therapeutic interventions.

Human leishmaniasis in Brazil: A general review

Leishmaniasis is a disease with ample clinical spectrum and epidemiological diversity and is considered a major public health problem. This article presents an overview of the transmission cycles, host-parasite interactions, clinical, histological and immunological aspects, diagnosis and treatment of various forms of the human disease.

SLC11A1 polymorphisms and host susceptibility to cutaneous leishmaniasis in Pakistan

Background

The vector-borne cutaneous leishmaniasis (CL) is endemic in several regions of Pakistan mainly affecting poor populations. Host genetic factors, particularly SLC11A1 (solute carrier transmembrane protein) within macrophages, play a crucial role in disease pathology and susceptibility. Association of SLC11A1 with cutaneous leishmaniasis, a neglected tropical disease, is not well established. Inconsistencies have been observed within different populations worldwide with respect to genetic susceptibility. This study was designed to investigate genetic variation(s) in SLC11A1 and to assess possible association with cutaneous leishmaniasis in Pakistan.

Results

Eight polymorphisms (rs2276631, rs3731864, rs2290708, rs2695342, rs201565523, rs17215556, rs17235409, rs17235416) were genotyped across SLC11A1 in 274 patients and 119 healthy controls. Six polymorphisms were studied by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and sequencing. Two single nucleotide polymorphisms were analyzed with newly designed semi-nested PCR assays. Case-control analysis showed no association between selected polymorphisms in SLC11A1 and cutaneous leishmaniasis. No significant difference was observed in the distribution of alleles between leishmaniasis patients and healthy individuals. Strong pairwise linkage disequilibrium was observed between rs2276631 and rs2290708 (r² = 64); and rs17235409 and rs17235416 (r² = 78).

Conclusions

This study shows that genetic variations in the candidate gene SLC11A1 do not affect susceptibility to cutaneous leishmaniasis in the sample population from Pakistan.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1934-2) contains supplementary material, which is available to authorized users.

Molecular identification of Leishmania spp. clinical isolates from Colombia based on hsp70 gene

INTRODUCTION

Leishmaniasis is highly prevalent in Colombia, where at least six different species can cause disease of varying clinical presentations in humans. The identification of the infecting species is quite important for prognosis, therapeutics and epidemiology. Different techniques with variable discriminatory power have been used for the identification. 

OBJECTIVE

To carry out the molecular identification of Leishmania species through the amplification of a fragment of the hsp70 gene. 

MATERIALS AND METHODS

Molecular amplification of the hsp70 gene fragment (PCR-hsp70) followed by restriction fragment length polymorphism analysis (RFLP) was done for identification purposes using DNA from 81 clinical isolates of Leishmania. 

RESULTS

A single amplicon was obtained for all samples analyzed. The enzymatic restrictions of the 81 PCR products identified 70 with a banding pattern corresponding to L. braziliensis with two different patterns (62 and eight isolates, respectively), nine isolates compatible with L. panamensis and two with L. guyanensis. The geographical origin of the isolates is consistent with previous reports about the distribution of the corresponding species in Colombia. 

CONCLUSIONS

The PCR-hsp70/RFLP technique used is a valid tool for the identification of Leishmania species isolated from clinical samples of patients in Colombia, which may also be applicable to the study of strains obtained from vectors and reservoirs with epidemiological significance.

Functional variations in MBL2 gene are associated with cutaneous leishmaniasis in the Amazonas state of Brazil

Functional variations in the mannose-binding lectin (MBL2) gene causing low levels of serum MBL are associated with susceptibility to numerous infectious diseases. We investigated whether there is genetic association of MBL2 variant alleles with cutaneous leishmaniasis (CL) caused by Leishmania guyanensis. We used PCR-restriction fragment length polymorphism to genotype six MBL2 variants, three in the promoter region and three in the exon 1. An association was noted between the single nucleotide polymorphism -221X/Y of the MBL2 gene and CL (P=2.9 × 10(-6); odds ratio (OR)=1.9 (1.4-2.5) consistent with the hypothesis that the -221X allele confers high risk to development of CL among L. guyanensis-infected individuals. Furthermore, L. guyanensis-infected individuals bearing the codon 57 allele C had a higher risk of developing CL (P=5 × 10(-5); OR=1.9 (1.4-2.6)). The low MBL expressor haplotype LXPB was also associated to CL (P=6 × 10(-4)). This study raises the possibility that functional polymorphisms in MBL2 gene play a role in clinical outcome of Leishmania infection.

Association between HLA genes and American cutaneous leishmaniasis in endemic regions of Southern Brazil

BACKGROUND

The present study sought to investigate the association between HLA-A, HLA-B and HLA-DRB1 genes and susceptibility or resistance to the different clinical manifestations of American cutaneous leishmaniasis (ACL) in southern Brazil.

METHODS

The sample consisted of 169 patients with a diagnosis of ACL and 270 healthy subjects for comparison. HLA-A, HLA-B and HLA-DRB1 were typed by PCR-SSO reverse dot blot.

RESULTS

Results showed a trend towards susceptibility to cutaneous lesions for alleles HLA-DRB1*13 (P=0.0228; Pc=0.3420; OR=1.66; 95%CI=1.08 - 2.56), HLA-B*35 (P=0.0218; Pc=0.6758; OR=1.67; 95%CI=1.08 - 2.29) and HLA-B*44 (P=0.0290; Pc=0.8990; OR=1.67; 95%CI=1.05 - 2.64). Subjects with allele HLA-B*27 (P=0.0180; Pc=0.5580; OR=7.1111; 95%CI=1.7850 - 28.3286) tended towards susceptibility to mucocutaneous lesions, those with HLA-B*49 (P=0.0101; Pc=0.3131; OR=6.4000; 95%CI=1.8472 - 22.1743) to recurrent ACL, and HLA-B*52 (P=0.0044; Pc=0.1360; OR=12.61; 95%CI=3.08 - 51.66), to re-infection. Presence of HLA-B*45 (P=0.0107; Pc=0.3317) tended to provide protection against the cutaneous form of ACL. The most frequent haplotypes that may be associated with susceptibility to ACL were A*02 B*44 DRB1*07 (P = 0.0236) and A*24 B*35 DRB1*01 (P = 0.0236).

CONCLUSION

Some Class I and Class II HLA genes appear to contribute towards susceptibility to and protection against different clinical manifestations of ACL. Other genetic marker studies may contribute toward future prophylactic and therapeutic interventions in ACL.

Pharmacogenomics and Personalized Medicine for Infectious Diseases

Humans have been plagued by the scourge of invasion by pathogens leading to infectious diseases from the time in memoriam and are still the cause of morbidity and mortality among millions of individuals. Trying to understand the disease mechanisms and finding the remedial measures have been the quest of humankind. The susceptibility to disease of an individual in a given population is determined by ones genetic buildup. Response to treatment and the disease prognosis also depends upon individual’s genetic predisposition. The environmental stress induces mutations and is leading to the emergence of ever-increasing more dreaded infectious pathogens, and now we are in the era of increasing antibiotic resistance that has thrown up a challenge to find new treatment regimes. Discoveries in the science of high-throughput sequencing and array technologies have shown new hope and are bringing a revolution in human health. The information gained from sequencing of both human and pathogen genomes is a way forward in deciphering host-pathogen interactions. Deciphering the pathogen virulence factors, host susceptibility genes, and the molecular programs involved in the pathogenesis of disease has paved the way for discovery of new molecular targets for drugs, diagnostic markers, and vaccines. The genomic diversity in the human population leads to differences in host responses to drugs and vaccines and is the cause of poor response to treatment as well as adverse reactions. The study of pharmacogenomics of infectious diseases is still at an early stage of development, and many intricacies of the host-pathogen interaction are yet to be understood in full measure. However, progress has been made over the decades of research in some of the important infectious diseases revealing how the host genetic polymorphisms of drug-metabolizing enzymes and transporters affect the bioavailability of the drugs which further determine the efficacy and toxicology of the drugs used for treatment. Further, the field of structural biology and chemistry has intertwined to give rise to medical structural genomics leading the way to the discovery of new drug targets against infectious diseases. This chapter explores how the advent of “omics” technologies is making a beginning in bringing about a change in the prevention, diagnosis, and treatments of the infectious diseases and hence paving way for personalized medicine.

Single dose novel Salmonella vaccine enhances resistance against visceralizing L. major and L. donovani infection in susceptible BALB/c mice

Visceral leishmaniasis is a major neglected tropical disease, with an estimated 500,000 new cases and more than 50,000 deaths attributable to this disease every year. Drug therapy is available but costly and resistance against several drug classes has evolved. Despite all efforts, no commercial, let alone affordable, vaccine is available to date. Thus, the development of cost effective, needle-independent vaccines is a high priority. Here, we have continued efforts to develop live vaccine carriers based on recombinant Salmonella. We used an in silico approach to select novel Leishmania parasite antigens from proteomic data sets, with selection criteria based on protein abundance, conservation across Leishmania species and low homology to host species. Five chosen antigens were differentially expressed on the surface or in the cytosol of Salmonella typhimurium SL3261. A two-step procedure was developed to select optimal Salmonella vaccine strains for each antigen, based on bacterial fitness and antigen expression levels. We show that vaccine strains of Salmonella expressing the novel Leishmania antigens LinJ08.1190 and LinJ23.0410 significantly reduced visceralisation of L. major and enhanced systemic resistance against L. donovani in susceptible BALB/c mice. The results show that Salmonella are valid vaccine carriers for inducing resistance against visceral leishmaniasis but that their use may not be suitable for all antigens.

Fine mapping of Leishmania major susceptibility Locus lmr2 and evidence of a role for Fli1 in disease and wound healing

Genetic linkage studies of the host response to Leishmania major, the causative agent of cutaneous leishmaniasis, have identified significant genetic complexity in humans and mice. In the mouse model, multiple loci have been implicated in susceptibility to infection, but to date, the genes underlying these loci have not been identified. We now describe the contribution of a novel candidate gene, Fli1, to both L. major resistance and enhanced wound healing. We have previously mapped the L. major response locus, lmr2, to proximal chromosome 9 in a genetic cross between the resistant C57BL/6 strain and the susceptible BALB/c strain. We now show that the presence of the resistant C57BL/6 lmr2 allele in susceptible BALB/c mice confers an enhanced L. major resistance and wound healing phenotype. Fine mapping of the lmr2 locus permitted the localization of the lmr2 quantitative trait locus to a 5-Mb interval comprising 21 genes, of which microarray analysis was able to identify differential expression in 1 gene-Fli1. Analysis of Fli1 expression in wounded and L. major-infected skin and naïve and infected lymph nodes validated the importance of Fli1 in lesion resolution and wound healing and identified 3 polymorphisms in the Fli1 promoter, among which a GA repeat element may be the important contributor.

Candidate gene study of susceptibility to cutaneous leishmaniasis in Sri Lanka

OBJECTIVES

To investigate the association between selected single nucleotide polymorphisms (SNPs) in TNF, LTA and SLC11A1 genes and risk of endemic cutaneous leishmaniasis (CL) in Sri Lanka through a case-control disease association study.

METHODS

An anonymized DNA resource representative of the Sri Lankan population was genotyped initially to establish baseline parameters. This was followed up by genotyping 200 patients and 200 matched controls. Published or modified PCR/RFLP methods were employed for genotyping.

RESULTS

Comparison of the different ethnic groups showed the distribution of alleles of LTA +252 A>G to differ significantly in Tamils and Moors when compared with Sinhalese. The differences seen at allele level were also reflected in the haplotypes defined by these SNPs at the TNF locus. The case-control analysis did not show an association between the SNPs or the haplotypes investigated and CL. The distribution of these variant alleles in other populations, where they are positively associated with leishmaniasis, differed significantly from the Sri Lankan study cohort.

CONCLUSIONS

The selected polymorphisms do not predispose to CL in the Sri Lankan population. The study of extended haplotypes at these loci using a sufficiently powered sample collection would elaborate the findings of this study. In the face of an evolving disease pattern in the country with other forms of leishmaniasis now being reported, prevalence of polymorphisms predisposing to these forms calls for heightened surveillance and preparedness.

The role of host genetics in leishmaniasis

Leishmaniasis is one of the world's important infectious diseases. It is prevalent in tropical and subtropical regions of the world and endemic in 88 countries, with two million new cases of leishmaniasis reported annually. As a complex disease, the pathology of leishmaniasis varies and is determined by factors such as the environment, the insect vector, and parasite and host genetics. The contributing host genetics involve multiple genes; thus, the mouse model of leishmaniasis has been exploited extensively in an attempt to identify and dissect the contribution of disease modifier genes to pathogenesis. This review summarizes recent advances in the identification of genetic loci involved in the host response to Leishmania spp. in the mouse model and in the human situation.

Cutaneous leishmaniasis: disease susceptibility and pharmacogenetic implications

Cutaneous leishmaniasis is a major tropical infection of public health importance caused by a number of vector-borne Leishmania protozoa species. Evidence supports a highly complex etiology. Environmental, parasite and host factors determine pathogenesis, and result in a diverse clinical spectrum of disease. Disease susceptibility, clinical course, prognosis and therapy response are highly variable, suggesting a genetic basis. Epidemiological studies have demonstrated familial aggregation, and family and association studies have identified HLA and non-HLA gene associations. Further progress in susceptibility gene identification for leishmaniasis would require genome-wide scans and candidate gene-association studies in large cohorts. Correlation between host genotype and therapy response has important pharmacogenetic implications, especially as current therapies for leishmaniasis are inadequate and progress in new drug development has been poor.

The first case of isolated facial cutanenous leishmaniasis in a Down syndrome infant: a case report and review of the literature

Background

Cutaneous leishmaniasis can be caused by several Leishmania species and is transmitted to human beings and animals by sand flies, Down syndrome is known to cause immunodeficiency that might lead to increase the susceptibility to infection with Leishmania.

Up to our knowledge this is the first case of isolated facial cutaneous leshmaniasis in association with Down syndrome.

Case presentation

A 2 month old Saudi Arabian male infant was admitted in the pediatric ward of maternity and children's hospital, Buraidah, Kingdom of Saudi Arabia for the management of multiple ulcers on his face, two ulcers were big and were surrounded by edema, causing severe disfigurement. This disfigurement caused difficulty in recognizing the facial feature of Down syndrome. The presence of hypotonia, microcephaly, low set ears, bilateral simian creases and wide separation between big toe and other toes directed us to request karyotyping. The result of karyotyping confirmed the diagnosis of Down syndrome.

Conclusion

Children with Down syndrome are immunodeficient, they have been reported to have a complex of immunological alterations which might lead to increased susceptibility to infection.

Fishing for anti-leishmania drugs: principles and problems

To date, there are no vaccines against any of the major parasitic diseases including leishmaniasis, and chemotherapy is the main weapon in our arsenal. Current drugs are toxic and expensive, and are losing their effectiveness due to parasite resistance. The availability of the genome sequence of two species of Leishmania, Leishmania major and Leishmania infantum, as well as that of Trypanosoma brucei and Trypanosoma cruzi should provide a cornucopia of potential new drug targets. Their exploitation will require a multi-disciplinary approach that includes protein structure and function and high throughput screening of random and directed chemical libraries, followed by in vivo testing in animals and humans. We outline the opportunities that are made possible by recent technologies, and potential problems that need to be overcome.

Cutaneous leishmaniasis

Cutaneous leishmaniasis is endemic in the tropics and neotropics. It is often referred to as a group of diseases because of the varied spectrum of clinical manifestations, which range from small cutaneous nodules to gross mucosal tissue destruction. Cutaneous leishmaniasis can be caused by several Leishmania spp and is transmitted to human beings and animals by sandflies. Despite its increasing worldwide incidence, but because it is rarely fatal, cutaneous leishmaniasis has become one of the so-called neglected diseases, with little interest by financial donors, public-health authorities, and professionals to implement activities to research, prevent, or control the disease. In endemic countries, diagnosis is often made clinically and, if possible, by microscopic examination of lesion biopsy smears to visually confirm leishmania parasites as the cause. The use of more sophisticated diagnostic techniques that allow for species identification is usually restricted to research or clinical settings in non-endemic countries. The mainstays of cutaneous leishmaniasis treatment are pentavalent antimonials, with new oral and topical treatment alternatives only becoming available within the past few years; a vaccine currently does not exist. Disease prevention and control are difficult because of the complexity of cutaneous leishmaniasis epizoology, and the few options available for effective vector control.

Leishmania isoenzyme polymorphisms in Ecuador: relationships with geographic distribution and clinical presentation

Background

Determinants of the clinical presentation of the leishmaniases are poorly understood but Leishmania species and strain differences are important. To examine the relationship between clinical presentation, species and isoenzyme polymorphisms, 56 Leishmania isolates from distinct presentations of American tegumentary leishmaniasis (ATL) from Ecuador were analyzed.

Methods

Isolates were characterized by multilocus enzyme electrophoresis for polymorphisms of 11 isoenzymes. Patients were infected in four different ecologic regions: highland and lowland jungle of the Pacific coast, Amazonian lowlands and Andean highlands.

Results

Six Leishmania species constituting 21 zymodemes were identified: L. (Viannia) panamensis (21 isolates, 7 zymodemes), L. (V.) guyanensis (7 isolates, 4 zymodemes), L. (V.) braziliensis (5 isolates, 3 zymodemes), L. (Leishmania) mexicana (11 isolates, 4 zymodemes), L. (L.) amazonensis (10 isolates, 2 zymodemes) and L. (L.) major (2 isolates, 1 zymodeme). L. panamensis was the species most frequently identified in the Pacific region and was associated with several clinical variants of cutaneous disease (CL); eight cases of leishmaniasis recidiva cutis (LRC) found in the Pacific highlands were associated with 3 zymodemes of this species. Mucocutaneous leishmaniasis found only in the Amazonian focus was associated with 3 zymodemes of L. braziliensis. The papular variant of CL, Uta, found in the Andean highlands was related predominantly with a single zymodeme of L. mexicana.

Conclusion

Our data show a high degree of phenotypic variation within species, and some evidence for associations between specific variants of ATL (i.e. Uta and LRC) and specific Leishmania zymodemes. This study further defines the geographic distribution of Leishmania species and clinical variants of ATL in Ecuador.