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      Further evidence associating IgG1, but not IgG2, with susceptibility to canine visceral leishmaniasis caused by Leishmania (L.) infantum chagasi-infection Translated title: Preuves supplémentaires associant les IgG1, mais pas les IgG2, à la susceptibilité à la leishmaniose viscérale canine causée par l'infection à Leishmania (L.) infantum chagasi

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          We present here a cross-sectional study analyzing the IgG1 and IgG2 immune responses to natural canine Leishmania (L.) infantum chagasi-infection and their relationships with delayed-type hypersensitivity (DTH) in 50 mongrel dogs with previous positive serodiagnoses (IFAT-IgG) (56% with subclinical status [= apparently healthy] and 44% clinically sick), living in endemic areas for visceral leishmaniasis in the Brazilian Amazon. IgG1 and IgG2 responses were measured using commercial polyclonal antibodies in ELISA, while DTH was elicited by intradermal skin test using cultured promastigotes L. (L.) i. chagasi-antigen. Data analyses used Chi-square and Pearson's r coefficient (95% confidence interval). Regarding DTH and the clinical statuses of dogs, it was noted that 100% of the animals showing positive DTH ( n = 8) were from the subclinical group, while 100% showing negative DTH were from the clinically sick group; higher IgG2 than IgG1 responses were observed in both clinical groups. However, when this comparison was made between the subclinical and sick groups, higher IgG1 responses were noted in the dogs from the sick rather than the subclinical group, while no differences were noted between the IgG2 responses in the dogs from both clinical groups. Additionally, we found lower IgG1 responses in dogs from the subclinical group showing positive DTH than in the dogs from the subclinical or sick groups with negative DTH; no differences were found between the IgG2 responses of these two clinical groups. These findings suggest that the IgG1, but not the IgG2, response is associated with susceptibility to canine visceral leishmaniasis (CVL).

          Translated abstract

          Nous présentons ici une étude transversale analysant les réponses immunitaires IgG1 et IgG2 à l'infection canine naturelle par Leishmania (L.) infantum chagasi et leurs relations avec une hypersensibilité retardée (HR) chez 50 chiens errants avec des sérologies positives antérieures (IFAT-IgG) (56 % avec statut sous-clinique [= apparemment en bonne santé] et 44 % malades cliniquement) vivant dans une zone endémique de leishmaniose viscérale dans l'Amazonie brésilienne. Les réponses IgG1 et IgG2 ont été mesurées en utilisant des anticorps polyclonaux commerciaux en ELISA, tandis que l'HR a été provoquée par un test cutané intradermique utilisant un antigène de promastigotes cultivés de L. (L.) i. chagasi. Les analyses de données ont utilisé le coefficient de Chi-carré et Pearson (intervalle de confiance de 95 %). En ce qui concerne l'HR et les états cliniques des chiens, on a noté que 100 % ( n = 8) des animaux présentant une HR positive provenaient du groupe sous-clinique, tandis que 100 % montrant une HR négative provenaient du groupe cliniquement malade. Des réponses IgG2 supérieures aux IgG1 ont été observées dans les deux groupes cliniques. Cependant, lorsque cette comparaison a été faite entre les groupes sous-clinique et malade, des réponses IgG1 plus élevées ont été observées chez les chiens du groupe malade que chez le groupe sous-clinique, alors qu'aucune différence n'a été notée entre les réponses IgG2 chez les chiens des deux groupes cliniques. En outre, nous avons trouvé des réponses IgG1 plus faibles chez les chiens du groupe sous-clinique présentant une HR positive que chez les chiens des groupes sous-cliniques ou malades avec HR négative. Aucune différence n'a été trouvée entre les réponses IgG2 de ces deux groupes cliniques. Ces résultats suggèrent fortement que la réponse IgG1, mais pas IgG2, est associée à une susceptibilité à la leishmaniose viscérale canine.

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          Most cited references 30

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          Directions for the diagnosis, clinical staging, treatment and prevention of canine leishmaniosis.

          Canine leishmaniosis (CanL) due to Leishmania infantum is a life threatening zoonotic disease with a wide distribution in four continents and importance also in non-endemic regions. The purpose of this report is to present a consensus of opinions on the diagnosis, treatment, prognosis and prevention of CanL in order to standardize the management of this infection. CanL is a disease in which infection does not equal clinical illness due to the high prevalence of subclinical infection among endemic canine populations. The most useful diagnostic approaches include serology by quantitative techniques and PCR. High antibody levels are associated with severe parasitism and disease and are diagnostic of clinical leishmaniosis. However, the presence of lower antibody levels is not necessarily indicative of disease and further work-up is necessary to confirm CanL by other diagnostic methods such as cytology, histopathology and PCR. We propose a system of four clinical stages, based on clinical signs, clinicopathological abnormalities and serological status. Suitable therapy and expected prognosis are presented for each of the stages. The combination of meglumine antimoniate and allopurinol constitutes the first line pharmaceutical protocol. However, although most dogs recover clinically after therapy, complete elimination of the parasite is usually not achieved and infected dogs may eventually relapse. Follow-up of treated dogs with blood counts, serum biochemistry, urinalysis, serology and PCR is essential for prevention of relapses. Protection against sand fly bites by topical insecticides is effective in reducing infection, and recent development of vaccines has indicated that prevention by vaccination is feasible.
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            Cellular and humoral immune responses in dogs experimentally and naturally infected with Leishmania infantum.

            In this paper we describe a number of immunological parameters for dogs with a chronic Leishmania infantum infection which exhibit patterns of progressive disease or apparent resistance. The outcome of infection was assessed by isolation of parasites, serum antibody titers to Leishmania antigen, and development of clinical signs of leishmaniasis. Our studies show that 3 years after experimental infection, asymptomatic or resistant dogs responded to L. infantum antigen both in lymphocyte proliferation assays in vitro and in delayed-type hypersensitivity reaction, whereas no serum antibodies to parasite antigen were shown. In contrast, symptomatic or susceptible animals failed to respond to parasite antigen in cell-mediated assays both in vitro and in vivo and showed considerably higher serum antibodies to leishmanial antigens. In addition, significantly higher level of interleukin 2 (IL-2) and tumor necrosis factor were found in supernatants from stimulated peripheral mononuclear cells from asymptomatic dogs compared with those from symptomatic and control uninfected dogs. IL-6 production did not vary significantly among the groups studied. Finally, we observed similar results with a group of mixed-breed dogs with natural Leishmania infections also grouped as asymptomatic or symptomatic on the basis of clinical signs of canine visceral leishmaniasis. These results demonstrate that serum antibody titers, antigen-specific proliferative responses, delayed-type hypersensitivity skin reactions, and IL-2 and tumor necrosis factor production by peripheral mononuclear cells can be used as markers of disease progression.
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              Systemic and compartmentalized immune response in canine visceral leishmaniasis.

              Human visceral leishmaniasis (VL) and canine visceral leishmaniasis (CVL) are the most important emerging diseases with high prevalence in Latin American countries and are mainly caused by Leishmania (L.) chagasi (Syn=L. infantum). CVL has a great impact on Brazilian public health because domestic dogs are the most important VL peri-domicile reservoirs in both urban and peri-urban areas. Our findings highlight the complexity of cellular immunological events related to the natural infection from dogs by L. chagasi, additionally correlating major peripheral blood phenotypic markers with clinical status and tissues parasite density. Our main results demonstrated that lower frequency of circulating B cells and monocytes are important markers of severe CVL, whereas increased levels of CD8+ lymphocytes appear to be the major phenotypic feature of asymptomatic disease. Determination of the isotypes patterns during CVL demonstrated that asymptomatic dogs and those with low parasitism are associated with an increase of IgG1, while the symptomatic dogs and those with high parasitism are associated with an increase of IgG, IgG2, IgM, IgA and IgE immunoglobulins. Pioneer findings obtained by our group showed a correlation between clinical status of CVL with degree of tissue parasite density. This data demonstrated that asymptomatic dogs presented low parasitism while symptomatic dogs are associated with high parasite load in various tissues such as skin, bone marrow and spleen. We have also investigated the association between tissue parasitism and CVL clinical forms. Regardless of clinical status, skin and spleen are the major sites of high parasite density during ongoing CVL. Furthermore, we demonstrated that bone marrow and spleen parasite density are the most reliable parasitological markers to decode the clinical status of CVL. In this article, we have reviewed some aspects of the histopathological and immunological events occurring in natural and experimental L. chagasi/L. infantum infection, pointing out the main L. chagasi-parasitized tissue. We have discussed the importance of the association between parasite density, immunological/histopathological aspects and clinical status of the CVL, their current applications, challenges for the future and potential opportunities in CVL research.

                Author and article information

                EDP Sciences
                13 October 2017
                : 24
                : ( publisher-idID: parasite/2017/01 )
                [1 ] Parasitology Department, Evandro Chagas Institute (Surveillance Secretary of Health, Ministry of Health), Ananindeua, Pará State Brazil
                [2 ] National Center of Primates (Surveillance Secretary of Health, Ministry of Health), Ananindeua, Pará state Brazil
                [3 ] Pathology Department, Medical School of São Paulo University São Paulo, São Paulo State Brazil
                [4 ] Tropical Medicine Nucleus, Federal University of Pará, Belém, Pará State Brazil
                Author notes
                [* ]Corresponding author: fernandotobias@ 123456iec.pa.gov.br
                parasite170041 10.1051/parasite/2017039
                © L.V.d.R. Lima et al., published by EDP Sciences, 2017

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                Page count
                Figures: 5, Tables: 2, Equations: 0, References: 33, Pages: 11
                Research Article


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