Arginase I induction during Leishmania major infection mediates the development of disease

In a previous work, we demonstrated that the induction of arginase I favored the replication of Leishmania inside macrophages. Now we have analyzed the differential expression of this enzyme in the mouse model of L. major infection. Ours results show that arginase I is induced in both susceptible and resistant mice during the development of the disease. However, in BALB/c-infected tissues, the induction of this protein parallels the time of infection, while in C57BL/6 mice, the enzyme is upregulated only during footpad swelling. The induction of the host arginase in both strains is mediated by the balance between interleukin-4 (IL-4) and IL-12 and opposite to nitric oxide synthase II expression. Moreover, inhibition of arginase reduces the number of parasites and delays disease outcome in BALB/c mice, while treatment with l-ornithine increases the susceptibility of C57BL/6 mice. Therefore, arginase I induction could be considered a marker of disease in leishmaniasis.

Meningeal leishmaniosis induced by Leishmania infantum in naturally infected dogs

We report two cases of meningitis caused by Leishmania infantum in naturally infected dogs. In both of these dogs the typical phenotypic features of granulomatous meningitis were observed with important lympho-plasma-cellular infiltrates and the presence of large numbers of parasites inside and outside macrophages. The immunological study of the cerebrospinal fluid of both animals showed that a large number of protein bands were recognized by those fluids and that they were similar to the ones recognized by the sera from the same animals. To our knowledge, this is the first description of meningitis associated to leishmaniosis.

Antigenicity of the Leishmania infantum histones H2B and H4 during canine viscerocutaneous leishmaniasis

In this study we show that sera from dogs naturally infected with Leishmania infantum contain antibodies that specifically react against the parasite H2B and H4 histones. The Leishmania H2B and the amino-terminal region of the histone H4, expressed as fusion proteins, when confronted with sera from canine viscerocutaneous leishmaniasis (VCL) dogs, were recognized by 63% and 47%, respectively. No reactivity was detected when sera from dogs naturally infected with pathogens other than Leishmania were used. Using a collection of synthetic peptides covering the complete sequence of both proteins, we have determined that the main linear antigenic determinants are located in the amino-terminal domains of these histones. The humoral response against histones H2B and H4 induced during canine leishmaniasis was found to be specific for Leishmania histones, since no cross-reactivity of the VCL sera with mammal histones was observed. Also, a comparative study of the prevalence of antibodies among VCL sera against the four core histones of L. infantum was performed. Although a large heterogeneity of the humoral responses against these proteins was found, histones H2A and H3 seem to be more prevalent immunogens than histones H2B and H4 during canine natural leishmaniasis. The origin of the anti-histone humoral response and its possible implications in the pathogenesis of Leishmania infection are discussed.

Analysis of the humoral immune response against total and recombinant antigens of Leishmania infantum: correlation with disease progression in canine experimental leishmaniasis

Leishmaniasis by Leishmania infantum in the Mediterranean Basin constitutes an important problem in both human and veterinary medicine. Based in both the importance of canids as reservoirs for the human disease and the fact that the canine disease may be an excellent model for the human condition, the present work has been conducted to analyze clinical and immune mechanisms associated with canine experimental leishmaniasis. Six-month-old mixed-breed dogs were intravenously infected with L. infantum promastigotes and the infection course was monitored along a 343 days-period. On day 75 post-infection (p.i.), amastigotes were observed in the lymph nodes of all dogs. The analysis of the humoral response against total L. infantum antigens by both ELISA and Western blotting evidenced a correlation between the levels of IgG isotypes (IgG1 and IgG2) and disease progression. It was observed that in those animals showing either a regressive or an oligosymptomatic form of the disease, the anti-Leishmania IgG1 antibodies were undetectable whereas those animals developing active disease showed high levels of anti-Leishmania IgG1 antibodies. Additionally, the time-course of antibody production against L. infantum recombinant antigens in the experimentally infected dogs has been analyzed. The present data suggest that reactivity against the heat-shock protein 70 (HSP70) may be used as diagnostic marker of early steps of infection, and that the appearance of anti-histone antibodies is associated with progression of infection to disease status.

Immunopathology of the uveitis in canine leishmaniasis

Particular immunopathological features and their effects on the vascular permeability of different ocular structures were analysed in two dogs naturally infected by Leishmania infantum. The existence of specific anti-Leishmania immunoglobulin G (IgG) in the aqueous humour was confirmed by the ELISA technique. There was no correlation between antibody levels in the aqueous humour and the related serum. The histopathological study of the eyes showed the existence of lesions in various ocular structures. The ciliary processes, ciliary body, sclerocorneal limbus, iris and lacrimal duct showed intense inflammatory zones with lymphocyte infiltrates, plasmatic cells and macrophages with amastigote forms of Leishmania. In addition vasculitis with dilation and thrombi were also detected in both cases, with consequent oedema and hyalinization. The immunohistochemistry analysis revealed the presence of granular and diffuse IgG deposits in the ciliary body, ciliary processes, sclerocorneal limbus and iris. Furthermore, numerous thrombosed vessels were observed in the sclerocorneal zone and iris. Complement 3 (C3) fraction deposits were not present in the ocular structures. The present data suggest that the ocular lesions may have an immunopathological origin.

Presence of antibodies in the aqueous humour and cerebrospinal fluid during Leishmania infections in dogs. Pathological features at the central nervous system

In the present paper we show that in dogs, naturally infected with Leishmania infantum, the aqueous humour and the cerebrospinal fluid contain anti-Leishmania IgGs and that the specificity of antigen recognition of these fluids is similar to that of the sera. We also show that in the encephalon and cerebellum of these dogs there is a pathological sponge-like reaction accompanied by neuronal degeneration, mobilization of glial cells together with accumulation of amyloid deposits. The interstitial and intravascular deposition of IgGs and Leishmania antigens in choroid plexus suggest that in these animals there is a failure of the blood-cerebrospinal and ciliary bodies filtration barriers which may allow the transfer of anti-Leishmania IgGs from the blood stream to these fluids. We suggest that the failure of the blood-cerebrospinal barrier and the in situ concentration of anti-Leishmania IgGs and antigens in brain tissues may predispose to the pathological features detected in this compartment.

An indirect fluorescent antibody technique for detection of anti-Dermatophilus congolensis antibodies in sheep

An indirect fluorescent antibody (IFA) technique has been developed for detection of anti-Dermatophilus antibodies in sheep. Sera from 25 bacteriologically confirmed clinically affected sheep and from 10 negative non affected lambs were used. Whole cell antigen from brain heart infusion cultures of D. congolensis was used and all sera were tested in the same way for cross-reactivity against antigens obtained from cultures of Actinomyces viscosus, Micrococcus luteus, Nocardia asteroides, and Corynebacterium pseudotuberculosis. Sera from Dermatophilus-infected sheep gave positive results with D. congolensis antigen and negative results with the antigens from other bacteria. The whole cell antigens employed were simple to prepare and easy to recognise by microscopy. Cross-reactivity was further tested using the D. congolensis culture whole cell antigen and 3 sera from sheep with bacteriologically confirmed natural infections due to Corynebacterium pseudotuberculosis, Actinomyces pyogenes and Nocardia asteroides. None of these sera showed positive reactions. The authors recommend this technique for serological surveys and research on dermatophilosis.

Pathological changes in kidneys of dogs with natural Leishmania infection

A study was made of the nephropathy in canine leishmaniasis produced in ten adult dogs naturally infected with Leishmania infantum. Renal function analyses were performed (uraemia, creatinaemia, plasma proteins, biochemistry and urinary sediment), the humoral immune response (fluorescent antibodies and levels of serum IgG, IgM and IgA) was assessed and histopathological studies were carried out. Correlation of the results showed acute renal insufficiency which was reversible in two animals (endotheliomesangial glomerulonephritis) and irreversible in four cases corresponding to glomerulonephritis in its Type I and Type II proliferative forms; extensive increase in the glomerular basal membrane, proliferation of mesangial cells and growth of the mesangial matrix were observed, as was a widespread incidence of immune complex deposits. Two animals showed chronic renal insufficiency. Lack of renal changes (minimal-changes glomerulonephritis) in two dogs was accounted for in one animal by an almost complete absence of symptoms and in the other by chronic viscerocutaneous symptoms; neither showed more than a slight immunoglobulin response.

Changes in the plasma concentrations of lipids and lipoprotein fractions in dogs infected with Leishmania infantum

A study was made of serum concentrations of cholesterol, phospholipids, triglycerides, cholesterol bound to high-density lipoproteins (HDL), HDL1-cholesterol, HDL2-cholesterol and cholesterol bound to low-density lipoproteins (LDL) in 16 dogs naturally infected with Leishmania infantum (ZMON-1) taken from an endemic focus. Results were compared with those of a control group of ten healthy dogs. Statistically significant increases in cholesterol, triglyceride and LDL-cholesterol levels were observed. There was, however, a statistically significant decrease in HDL-cholesterol level, mainly at the expense of the HDL2-cholesterol subfraction. Cholesterol transport is therefore shown to undergo changes which may be attributed to the consumptive evolution of the disease, immunocomplex deposits in cells, hepatic disorders and interactions between the parasite and the normal cholesterol metabolism of the host.