Leishmania infantum and dog: immunological and epidemiological studies about infection and disease

Lobjectiu daquesta tesi va ser obtenir nous coneixements sobre la immunologia i epidemiologia de la infeccio per Leishmania en gossos que viuen en zones endemiques. El capitol 2 descriu lexpressio danticossos anti-Leishmania IgG, IgG1 i IgG2 en una poblacio de gossos. Els nivells dimmunoglobulines en gossos asimptomatics van ser molt variables i menors que els dels animals malalts. En els animals malalts, els nivells de IgG i IgG2 van ser molt alts pero els nivells d IgG1 molt variables. Els resultats van mostrar la gran variacio en lexpressio de IgG1 tant en gossos asimptomatics com en simptomatics, aixi com la baixa correlacio de la IgG1 amb la IgG o IgG2. El capitol 3 descriu lavaluacio i comparacio de leficacia de dues preparacions de leishmanines en la deteccio de la resposta cel·lular davant de Leishmania en el gos. El capitol 4 mostra lestudi de la resposta humoral i cel·lular en una poblacio de gossos. El 77% dels gossos va mostrar una resposta immunitaria especifica davant de Leishmania, ja fos humoral o cel·lular. El 80% dels cans eivissencs i el 48% dels gossos daltres races van presentar resposta cel·lular. Els resultats van mostrar que la taxa dinfeccio era molt alta, i que els gossos presentaven un ampli ventall de respostes inmunitaries, des de gossos resistents fins a gossos malalts. El ca eivissenc va manifestar mes uniformement resposta cel·lular. El capitol 5 descriu lestudi de la prevalenca de la malaltia, la seroprevalenca i la prevalenca de la infeccio. Es va analitzar el quadre clinic, la serologia i la presencia dADN de Leishmania en diferents teixits. La prevalenca de la malaltia i seroprevalenca van ser, respectivament, dun 13% i dun 26%. Els resultats de PCR positives en moll dos, conjuntiva i pell van ser respectivament, dun 18%, 32% i 51%. La prevalenca de la infeccio va ser dun 67%. La majoria de gossos de zona endemica ha estat infectat pel parasit. El capitol 6 descriu lestudi de parametres immunologics (serologia, test intradermic amb leishmanina, assaig de proliferacio de limfocits i deteccio dIFN-g i TNF-a) en lavaluacio de gossos infectats amb Leishmania. La majoria dels animals infectats sense simptomatologia clinica presentava nivells variables danticossos, reaccio positiva al test intradermic, bona resposta proliferativa al antigen de Leishmania i produccio dIFN-g. La resta va mostrar nivells variables danticossos pero absencia de reaccio al test intradermic. Abans del tractament, els animals malalts presentaven alts nivells danticossos, test intradermic negatiu, no produccio dIFN-g i produccio de TNF-a. La millora clinica es va associar amb la disminucio dels anticossos i amb laugment del diametre del test intradermic. La combinacio de la serologia, el test intradermic i la medicio de citocines constitueixen tecniques utils i dalta rellevancia clinica en lavaluacio de la resposta inmunitaria dun pacient individual. The objective of this thesis was to obtain new knowledge about the immunology and epidemiology of Leishmania infection in dogs living in endemic regions in the Mediterranean basin. Chapter 2 describes the expression of IgG, IgG1 and IgG2 specific antibodies to L. infantum in a wide population of dogs. The levels of immunoglobulins in asymptomatic dogs were highly variable and lower than those found in ill dogs. In ill dogs, the levels of IgG and IgG2 were very high but the levels of IgG1 were extremely variable. Overall results showed a large variation in the IgG1 expression in asymptomatic and symptomatic dogs and a low IgG1 correlation with IgG or IgG2. Chapter 3 describes the evaluation and comparison of the efficacy of two leishmanins for detection dog Leishmania cellular immune response. Chapter 4 describes the study of humoral and cellular responses in a population of dogs. Seventy-seven percent of the dogs demonstrated a specific Leishmania response either humoral or cellular. Eighty percent of ibizian hounds and 48% of dogs of other breeds presented a cellular response. The results showed that the rate of infection was high and that dogs presented a broad range of immune responses from resistant to ill dogs. The Ibizian hound manifested a more uniform cellular response. Chapter 5 describes the study of the prevalence of Leishmania infection, the seroprevalence and the prevalence of canine leishmaniosis. Clinical exploration for the presence of clinical signs compatible with leishmaniosis, the titre of anti-Leishmania antibodies, and the presence of Leishmania DNA by PCR on several tissues were assessed. The prevalence of the disease was 13% and the seroprevalence was 26%. The results of positive PCR in the bone marrow, the conjunctiva and the skin were 18%, 32% and 51%, respectively. The prevalence of the infection was 67%. The results showed that Leishmania infects the majority of dogs living in an endemic area. Chapter 6 describes the study of immunological parameters (anti-Leishmania IgG1, IgG2, total IgG antibodies, LST, LPA, and production of IFN-g and TNF-a) in the evaluation of dogs infected by Leishmania. The majority of infected animals without clinically patent disease showed variable titres of anti-Leishmania antibodies, a positive LST, a strong Leishmania antigenic proliferative response, and a high production of IFN-g. The remainder showed positive titres of anti-Leishmania antibodies with a negative positive LST. Before treatment, ill dogs presented high levels of anti-Leishmania antibodies, negative LST, no production of IFN-g but a production of TNF-a. Clinical recovery was associated with a decrease in the titre of antibodies and an increase of the diameter of the LST. The combination of serology, LST, and measurement of cytokines constitutes a useful, clinically relevant method to evaluate the immune response to Leishmania in a single patient.