Chromosomal segments may explain the antibody response cooperation for canine leishmaniasis pathogenesis

Understanding hypergammaglobulinemia in experimental or natural visceral leishmaniasis

Nonspecific hypergammaglobulinemia (HGG) occurs in symptomatic human visceral leishmaniasis (VL) caused by L. L. infantum. This study assessed this finding in experimental infection in hamsters and natural infection in dogs. The serum concentration of proteins, albumin and globulins was determined through the biuret and bromocresol green reaction, where the HGG was better expressed through the albumin/globulin (A/G) ratio. HGG was associated with a higher concentration of specific anti-glycan antibodies (BSA-G)/promastigote soluble extract (PSE) and the presence of circulating immune complexes (IC) by dissociative enzyme-linked immunoassay (ELISA). The study found monovalent IC in 37.9% (PSE) and 50% (BSA-G) of sera from infected hamsters, with increased frequency as the disease progressed. HGG was found in >60% of the samples in dogs with VL, associated with higher levels of specific immunoglobulin (Ig)A and IgM, but not IgG, determined using the PSE and BSA-G ELISA. HGG was associated with the presence of monovalent IC in 58.9% (PSE) and 63.4% (BSA-G) positive dog samples. HGG may result not only from the nonspecific activation of B cells, with greater production of specific and nonspecific antibodies, but also due to lower IgG excretion due to the presence of soluble monovalent IC. HGG correlates to the progression of VL and may be a marker for manifested disease.

Immune and Genomic Analysis of Boxer Dog Breed and Its Relationship with Leishmania infantum Infection

Simple Summary

Leishmaniosis is a zoonotic disease, endemic in 88 countries, including those from the Mediterranean region. Several authors indicate differences in susceptibility and resistance to leishmaniosis in different canine breeds, with boxer being one of the breeds with a higher prevalence of the disease. This study analyzes the serum profiles of cytokines related to the immune response, together with the screening of genomic variants fixed in boxer breed samples, to understand their differential susceptibility to L. infantum infection. The results of this study indicate new pathways related to L. infantum infection and immune response in boxers, involving genes related to interleukin and toll-like receptors, as well as to the immune system and the regulation of expression. Future studies are required to elucidate the role of specific genes in the L. infantum infection mechanism in this canine breed.

Abstract

Leishmaniosis, one of the most important zoonoses in Europe, is caused by Leishmania infantum, an intracellular protozoan parasite. This disease is endemic in the Mediterranean 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 the Mediterranean area were evaluated to analyze the immune response and the possible genetic explanation for this susceptibility. Serum levels of cytokines IFN-γ, 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.

Serum antibodies blocked by glycan antigens in canine visceral leishmaniasis serology are mostly IgA immune complexes

Immune complexes (ICs) are found in canine visceral leishmaniasis (CVL) and interfere with the serum detection of antibodies. Dissociation of these monovalent complexes by dissociative enzyme-linked immunosorbent assay (ELISA) removes false-negative results and allows some characterization of antibodies and antigens. We studied the serology of dogs with suspected CVL in an endemic area, testing two Leishmania (Leishmania) [L. (L.)] infantum antigens. We analysed the presence of immunoglobulin G (IgG), immunoglobulin A (IgA) and immunoglobulin M (IgM) antibodies specific to promastigote soluble extract (PSE) and low-molecular weight glycans (glycan–bovine serum albumin (BSA) complex – GBC) by conventional and dissociative ELISA. Our results showed a significant fraction of IgA ICs (46.5% for PSE and 47.6% for GBC), followed by IgG ICs (10% for PSE and 23.5% for GBC). IgM ICs were more frequent for PSE (22.7%). Hypergammaglobulinaemia in CVL would be related to the presence of IgA and IgG ICs, resulting in deficient elimination of these antibodies. Our data confirmed the presence of ICs that can generate false-negative results in conventional serology. The production of IgA antibodies and the high frequency of blockade by glycan antigens suggest the active participation of this immunoglobulin and its ICs in the immunopathology of CVL, indicating a new path for further research.

Is the Prevalence of Leishmania infantum Linked to Breeds in Dogs? Characterization of Seropositive Dogs in Ibiza

Simple Summary

Leishmaniosis is an important zoonotic protozoan disease. Leishmania infantum is a protozoan species that accounts for the majority of cases in the Mediterranean. In this study, we analyzed the prevalence of infection in different dog breeds from Ibizan Island. Our results showed that the Doberman Pinscher and Boxer breeds present a higher prevalence of infection, and the relationship between antibodies’ serum titer and staging of disease was confirmed. Differences between age and sex were not found.

Abstract

Leishmaniosis is an important zoonotic protozoan disease primarily spread to the Mediterranean region by Leishmania infantum, the predominant protozoan species, which accounts for the majority of cases. Development of disease depends on the immune response of the definitive host and, predictably, their genetic background. Recent studies have revealed breed-typical haplotypes that are susceptible to the spread of the protozoan parasite. The objective of this study was to analyze the prevalence of leishmaniosis on a Mediterranean island and determine the relationship between disease prevalence and breed. In addition, information on seropositive animals was recorded to characterize animals affected by the disease. To study the prevalence, a total of 3141 dogs were analyzed. Of these, the 149 infected animals were examined for age, sex, antibody titer, and disease stage. We observed a prevalence of 4.74%, which varied between breeds (p < 0.05). The Doberman Pinscher and Boxer breeds had the highest prevalence of leishmaniosis. Significant differences were observed between breeds with common ancestors, emphasizing the important genetic component. Finally, regarding the characterization of seropositive animals, the distribution is similar to other studies. We discovered a relationship (p < 0.05) between the number of antibody titers and the clinical disease stage, which was also present in Leishmania infantum, suggesting that the development of the disease depends on the humoral or Th2 immune response with ineffective antibodies.

Emergent canine visceral leishmaniasis in Argentina: Comparative diagnostics and relevance to proliferation of human disease

BACKGROUND

Visceral leishmaniasis (VL) is a zoonotic protozoal vector-borne disease that is a major public health challenge. In Argentina, canine (CVL) and human visceral leishmaniasis (HVL) have recently emerged. There is a lack of standardised diagnostic tests for CVL, which hinders control of CVL and HVL.

METHODOLOGY/PRINCIPAL FINDINGS

Sampling was carried out in Puerto Iguazú, Argentina, comprising 190 asymptomatic, oligosymptomatic and polysymptomatic dogs. The following diagnostics were applied: microscopy of lymph node aspirate (LNA); three immunochromatographic rapid diagnostic tests (RDTs), prototype rK28-ICT, rK39-ICT (both Coris BioConcept), commercial rK39 (InBios); ELISA for IgG, IgG1 and IgG2, against rK28, rK39 or crude lysate antigen. DNA detection and analysis, with 30 dogs, was of the ITS1 region using skin samples, and loop-mediated isothermal amplification (LAMP; Eiken Loopamp) of buffy coat, skin scrape or LNA. 15.4% of dogs were positive by LNA microscopy. The rK28 RDT had higher seropositivity rate (61%) than either a prototype rK39 RDT (31.4%) or commercial rK39 RDT (18.8%), without cross-reactivity with six other pathogens. IgG anti-rK39 ELISA antibody titres, but not IgG2, were positively correlated with number of clinical signs. LAMP with LNA had a higher positivity rate than PCR; buffy coat sampling was more sensitive than skin scrape. ITS1 confirmed Leishmania (Leishmania) infantum as the agent of CVL. Leishmania (Viannia) spp. was detected in skin samples from two dogs, compatible with Leishmania (Viannia) braziliensis.

CONCLUSIONS/SIGNIFICANCE

Seroprevalence confirmed rapid increase in CVL in Puerto Iguazú. The rK28 RDT test potentially has great value for improved point-of-care diagnosis. Given cost reduction and accessibility, commercial LAMP may be applicable to buffy coat. RDT biomarkers of CVL clinical status are required to combat spread of CVL and HVL. The presence of Viannia, perhaps as an agent of human mucocutaneous leishmaniasis (MCL), highlights the need for vigilance and surveillance.