1. Investigación

Leishmaniasis is a zoonotic parasitic disease, and the main reservoir of the parasite is the dog, although recent years have seen an increase in other mammalian species. In the Mediterranean region, where it is an endemic disease, it is caused by the species Leishmania infantum. The Ibizan hound, an autochthonous breed of this region, appears to have a genetic resistance to parasitic infection, whereas other canine breeds, such as the Boxer, are susceptible to infection. These differences are related to the differentiated activation of the immune response, with the Ibizan hound activating the Th1 immune response, whereas the Boxer breed triggers the Th2 immune response. Cytokine levels and genomic haplotypes of several genes involved in the immune response were analysed in twenty-eight Ibizan hound (resistant canine breed model) and twenty-four Boxer (susceptible canine breed) without clinical signs in the Mediterranean region. Cytokine levels were analysed by ELISA commercial kits and haplotypes were studied using CanineHD DNA Analysis BeadChip including 165,480 mapped positions. The results show 126 haplotypes associated with differential immune response in dogs. Specifically, haplotypes in IL12RB1, IL6R, CIITA, THEMIS, NOXA1, HEY2, RAB38, SLC35D2, SLC28A3, RASEF and DAPK1 genes are associated with serum levels of IFN-γ, IL-2, IL-8, and IL-18. These results suggest that the resistance or susceptibility to Leishmania infantum infection could be a consequence of haplotypes in several genes related to immune response. Future studies are needed to elucidate the relationship of these haplotypes with immune response and gene expression regulation.

Background The Ibizan Hound is a canine breed native to the Mediterranean region, where leishmaniasis is an endemic zoonosis. Several studies indicate a low prevalence of this disease in Ibizan Hound dogs, whereas other canine breeds present a high prevalence. However, the underlying molecular mechanisms still remain unknown. The aim of this work is to analyse the relationship between serum levels of cytokines and the genomic profiles in two canine breeds, Ibizan Hound (resistant canine breed model) and Boxer (susceptible canine breed model). Methods In this study, we analyse the haplotypes of genes encoding cytokines related to immune response of Leishmania infantum infection in twenty-four Boxers and twenty-eight Ibizan Hounds apparently healthy using CanineHD DNA Analysis BeadChip including 165,480 mapped positions. The haplo.glm extension of haplo.score was used to perform a General Linear Model (GLM) regression to estimate the magnitude of individual haplotype effects within each cytokine. Results Mean levels of interferon gamma (IFN-γ), interleukin 2 (IL-2) and IL-18 in Boxer dogs were 0.19 ± 0.05 ng/ml, 46.70 ± 4.54 ng/ml, and 36.37 ± 30.59 pg/ml, whereas Ibizan Hound dogs present 0.49 ± 0.05 ng/ml, 64.55 ± 4.54 ng/ ml, and 492.10 ± 31.18 pg/ml, respectively. The GLM regression shows fifteen haplotypes with statistically significant effect on the cytokine serum levels (P < 0.05). The more relevant are IL6-CGAAG and IFNG-GCA haplotypes, which increase and decrease the IL-2, IL-8 and IFN-γ serum levels, respectively. Conclusions Haplotypes in the IFNG and IL6 genes have been correlated to serum levels of IFN-γ, IL-2 and IL-18, and a moderate effect has been found on IL8 haplotype correlated to IL-8 and IL-18 serum levels. The results indicate that the resistance to L. infantum infection could be a consequence of certain haplotypes with a high frequency in the Ibizan Hound dog breed, while susceptibility to the disease would be related to other specific haplotypes, with high frequency in Boxer. Future studies are needed to elucidate whether these differences and haplotypes are related to different phenotypes in immune response and expression gene regulation to L. infantum infections in dogs and their possible application in new treatments and vaccines.

Background: The Ibizan Hound is a canine breed native to the Mediterranean region, where leishmaniosis is an endemic zoonosis. Several studies indicate low prevalence of this disease in these dogs but the underlying molecular mechanism remains unknown. Methods: In this study, qualitative immunological and genomic profiles of this breed have been analyzed. Results: Our analysis shows relevant differences between the cytokine serum profile of Ibizan Hound dogs and previously published data from other canine strains. Additionally, several genetic risk variants related to the immune response, regulation of the immune system, and genes encoding cytokines and their receptors have been studied. The most relevant genes that presented such fixed polymorphisms were IFNG and IL6R. Other variants with frequencies ≥ 0.7 were found in the genes ARHGAP18, DAPK1, GNAI2, MITF, IL12RB1, LTBP1, SCL28A3, SCL35D2, PTPN22, CIITA, THEMIS, and CD180. Epigenetic regulatory genes such as HEY2 and L3MBTL3 showed also intronic polymorphisms. Conclusions: Our analysis and results indicate that the regulation of immune responses is different in Ibizan Hounds compared to other breeds. Future studies are needed to elucidate whether these differences are related to the low prevalence of L. infantum infection in the Ibizan Hound.

Leishmaniosis, one of themost important zoonoses in Europe, is caused by Leishmania infantum, an intracellular protozoan parasite. This disease is endemic in theMediterranean area, where the main reservoir is the dog. Several studies indicate a possible susceptibility to L. infantum infection with clinical signs in some canine breeds. One of them is the boxer breed, which shows a high prevalence of disease. In this study, immunological and genomic characterization of serum samples from boxer dogs living in theMediterranean area were evaluated to analyze the immune response and the possible genetic explanation for this susceptibility. Serum levels of cytokines IFN- , IL-2, IL-6, IL-8, and IL-18 were determined by ELISA commercial tests, while the genotyping study was performed using the CanineHD DNA Analysis BeadChip. The results show relevant differences in the serum levels of cytokines compared to published data on other canine breeds, as well as sequence changes that could explain the high susceptibility of the boxer breed to the disease. Concretely, polymorphic variants in the CIITA, HSF2BP, LTBP1,MITF, NOXA1, PKIB, RAB38, RASEF, TLE1, and TLR4 genes were found, which could explain the susceptibility of this breed to L. infantum infection.