Current Status of Epidemiology of Leishmaniases. In: Farrell JP, editor. Leishmania. Boston: Springer US; 2002. pp. 1-10. [DOI: 10.1007/978-1-4615-0955-4_1]

Alternative hosts of Leishmania infantum: a neglected parasite in Europe

Multi-host pathogens that infect various animal species and humans are considered of great importance for public and animal health. Leishmania spp. parasites are a characteristic example of such pathogens. Although leishmaniosis in humans is endemic for about 100 countries around the world it is classified as a neglected tropical disease. There are three main forms of leishmaniosis in humans: cutaneous (CL), visceral (VL) and mucocutaneous leishmaniosis (MCL). Each year, about 30,000 new cases of VL and more than 1 million new cases of CL are recorded. In Europe L. infantum is the dominant species with dogs being reservoir hosts. Apart from dogs, infection has been recorded in various animals, which suggests that other species could play a role in the maintenance of the parasite in nature. Herein we provide an in-depth review of the literature with respect to studies that deal with Leishmania infantum infections in domestic and wild animal species in Europe. Given the fact that domesticated and wild animals could contribute to the incidences of leishmaniosis in humans, the aim of this paper is to provide a comprehensive review which could potentially be used for the development of measures when it comes to the control of the Leishmania infantum parasite.

Effects of Leishmania major infection on the gut microbiome of resistant and susceptible mice

Cutaneous leishmaniasis, a parasitic disease caused by Leishmania major, is a widely frequent form in humans. To explore the importance of the host gut microbiota and to investigate its changes during L. major infection, two different groups of mouse models were assessed. The microbiome of two parts of the host gut-ileum and colon-from infected and non-infected mice were characterised by sequencing of 16S rDNA using an Ion Torrent PGM platform. Microbiome analysis was performed to reveal changes related to the susceptibility and the genetics of mice strains in two different gut compartments and to compare the results between infected and non-infected mice. The results showed that Leishmania infection affects mainly the ileum microbiota, whereas the colon bacterial community was more stable. Different biomarkers were determined in the gut microbiota of infected resistant mice and infected susceptible mice using LEfSe analysis. Lactobacillaceae was associated with resistance in the colon microbiota of all resistant mice strains infected with L. major. Genes related to xenobiotic biodegradation and metabolism and amino acid metabolism were primarily enriched in the small intestine microbiome of resistant strains, while genes associated with carbohydrate metabolism and glycan biosynthesis and metabolism were most abundant in the gut microbiome of the infected susceptible mice. These results should improve our understanding of host-parasite interaction and provide important insights into the effect of leishmaniasis on the gut microbiota. Also, this study highlights the role of host genetic variation in shaping the diversity and composition of the gut microbiome. KEY POINTS: • Leishmaniasis may affect mainly the ileum microbiota while colon microbiota was more stable. • Biomarkers related with resistance or susceptibility were determined in the gut microbiota of mice. • Several pathways were predicted to be upregulated in the gut microbiota of resistant or susceptible mice.

Guanylate Binding Proteins Restrict Leishmania donovani Growth in Nonphagocytic Cells Independent of Parasitophorous Vacuolar Targeting

Interferon (IFN)-inducible guanylate binding proteins (GBPs) play important roles in host defense against many intracellular pathogens that reside within pathogen-containing vacuoles (PVs). For instance, members of the GBP family translocate to PVs occupied by the protozoan pathogen Toxoplasma and facilitate PV disruption and lytic parasite killing. While the GBP defense program targeting Toxoplasma has been studied in some detail, the role of GBPs in host defense to other protozoan pathogens is poorly characterized. Here, we report a critical role for both mouse and human GBPs in the cell-autonomous immune response against the vector-borne parasite Leishmania donovani Although L. donovani can infect both phagocytic and nonphagocytic cells, it predominantly replicates inside professional phagocytes. The underlying basis for this cell type tropism is unclear. Here, we demonstrate that GBPs restrict growth of L. donovani in both mouse and human nonphagocytic cells. GBP-mediated restriction of L. donovani replication occurs via a noncanonical pathway that operates independent of detectable translocation of GBPs to L. donovan-containing vacuoles (LCVs). Instead of promoting the lytic destruction of PVs, as reported for GBP-mediated killing of Toxoplasma in phagocytic cells, GBPs facilitate the delivery of L. donovani into autolysosomal-marker-positive compartments in mouse embryonic fibroblasts as well as the human epithelial cell line A549. Together our results show that GBPs control a novel cell-autonomous host defense program, which renders nonphagocytic cells nonpermissible for efficient Leishmania replication.IMPORTANCE The obligate intracellular parasite Leishmania causes the disease leishmaniasis, which is transmitted to mammalian hosts, including humans, via the sandfly vector. Following the bite-induced breach of the skin barrier, Leishmania is known to live and replicate predominantly inside professional phagocytes. Although Leishmania is also able to infect nonphagocytic cells, nonphagocytic cells support limited parasitic replication for unknown reasons. In this study, we show that nonphagocytic cells possess an intrinsic property to restrict Leishmania growth. Our study defines a novel role for a family of host defense proteins, the guanylate binding proteins (GBPs), in antileishmanial immunity. Mechanistically, our data indicate that GBPs facilitate the delivery of Leishmania into antimicrobial autolysosomes, thereby enhancing parasite clearance in nonphagocytic cells. We propose that this GBP-dependent host defense program makes nonphagocytic cells an inhospitable host cell type for Leishmania growth.

Genetic Regulation of Guanylate-Binding Proteins 2b and 5 during Leishmaniasis in Mice

Interferon-induced GTPases [guanylate-binding proteins (GBPs)] play an important role in inflammasome activation and mediate innate resistance to many intracellular pathogens, but little is known about their role in leishmaniasis. We therefore studied expression of Gbp2b/Gbp1 and Gbp5 mRNA in skin, inguinal lymph nodes, spleen, and liver after Leishmania major infection and in uninfected controls. We used two different groups of related mouse strains: BALB/c, STS, and CcS-5, CcS-16, and CcS-20 that carry different combinations of BALB/c and STS genomes, and strains O20, C57BL/10 (B10) and B10.O20, OcB-9, and OcB-43 carrying different combinations of O20 and B10 genomes. The strains were classified on the basis of size and number of infection-induced skin lesions as highly susceptible (BALB/c, CcS-16), susceptible (B10.O20), intermediate (CcS-20), and resistant (STS, O20, B10, OcB-9, OcB-43). Some uninfected strains differed in expression of Gbp2b/Gbp1 and Gbp5, especially of Gbp2b/Gbp1 in skin. Uninfected BALB/c and STS did not differ in their expression, but in CcS-5, CcS-16, and CcS-20, which all carry BALB/c-derived Gbp gene-cluster, expression of Gbp2b/Gbp1 exceeds that of both parents. These data indicate trans-regulation of Gbps. Infection resulted in approximately 10× upregulation of Gbp2b/Gbp1 and Gbp5 mRNAs in organs of both susceptible and resistant strains, which was most pronounced in skin. CcS-20 expressed higher level of Gbp2b/Gbp1 than both parental strains in skin, whereas CcS-16 expressed higher level of Gbp2b/Gbp1 than both parental strains in skin and liver. This indicates a trans-regulation present in infected mice CcS-16 and CcS-20. Immunostaining of skin of five strains revealed in resistant and intermediate strains STS, CcS-5, O20, and CcS-20 tight co-localization of Gbp2b/Gbp1 protein with most L. major parasites, whereas in the highly susceptible strain, BALB/c most parasites did not associate with Gbp2b/Gbp1. In conclusion, expression of Gbp2b/Gbp1 and Gbp5 was increased even in organs of clinically asymptomatic resistant mice. It suggests a hidden inflammation, which might contribute to control of persisting parasites. This is supported by the co-localization of Gbpb2/Gbp1 protein and L. major parasites in skin of resistant and intermediate but not highly susceptible mice.

Identification of substrates of an S-phase cell cycle kinase from Leishmania donovani

Despite the importance of cyclin-Cdk related kinases (CRK) in regulation of cell and life cycle of kinetoplastida parasites, only limited knowledge about their substrates are presently available. Here, the potential substrates were searched for an S-phase LdCyc1-CRK3 complex from Leishmania donovani based on the presence of Cdk target phosphorylation site together with the cyclin interacting Cy-motif in genome-derived putative protein sequences. Three substrates could be identified with one of them being a unique protein with no known homologues. Another identified substrate is similar to MYST family of histone acetyl transferase and the third one contains Ku-70 related conserved domains. All the substrates interact directly with LdCyc1 and are phosphorylated in a Cy-motif dependent manner suggesting the importance of Cy-motif for their functions.

Genetic susceptibility to infectious disease: lessons from mouse models of leishmaniasis

Susceptibility to infectious disease is influenced by multiple host genes, most of which are low penetrance QTLs that are difficult to map in humans. Leishmaniasis is a well-studied infectious disease with a variety of symptoms and well-defined immunological features. Mouse models of this disease have revealed more than 20 QTLs as being susceptibility genes, studies of which have made important contributions to our understanding of the host response to infection. The functional effects of individual QTLs differ widely, indicating a networked regulation of these effects. Several of these QTLs probably also influence susceptibility to other infections, indicating that their characterization will contribute to our understanding of susceptibility to infectious disease in general.