An experimental protocol for the establishment of dogs with long-term cellular immune reactions to Leishmania antigens

Domestic dogs are considered to be the main reservoirs of zoonotic visceral leishmaniasis. In this work, we evaluated a protocol to induce Leishmania infantum/Leishmania chagasi-specific cellular and humoral immune responses in dogs, which consisted of two injections of Leishmania promastigote lysate followed by a subcutaneous inoculation of viable promastigotes. The primary objective was to establish a canine experimental model to provide positive controls for testing immune responses to Leishmania in laboratory conditions. After inoculation of viable promastigotes, specific proliferative responses of peripheral blood mononuclear cells (PBMCs) to either Leishmania lysate or recombinant proteins, the in vitro production of interferon-γ by antigen-stimulated PBMCs and a significant increase in circulating levels of anti-Leishmania antibodies were observed. The immunized dogs also displayed positive delayed-type hypersensitivity reactions to Leishmania crude antigens and to purified recombinant proteins. An important finding that supports the suitability of the dogs as positive controls is that they remained healthy for the entire observation period, i.e., more than seven years after infection. Following the Leishmania antigen lysate injections, the infection of dogs by the subcutaneous route appears to induce a sustained cellular immune response, leading to an asymptomatic infection. This provides a useful model for both the selection of immunogenic Leishmania antigens and for immunobiological studies on their possible immunoprotective activities.

Frequência de anticorpos anti-Neospora caninum em cães nos municípios de Salvador e Lauro de Freitas, Estado da Bahia - Brasil / Frequency of antibodies anti-Neospora caninum on dogs from Salvador and Lauro de Freitas, Bahia state - Brasil

A freqüência de anticorpos IgG anti-Neospora caninum foi estudada em 415 amostras séricas de cães domiciliados e errantes, procedentes dos municípios baianos de Salvador e Lauro de Freitas, utilizando-se a técnica de imunofluorescência indireta, com ponto de corte igual a 1:50. Anticorpos da classe IgG anti-N. caninum foram detectados em 13,3% (22/165) dos cães domiciliados e em 11,2% (28/250) dos errantes. As freqüências de soropositivos machos e fêmeas foram 8,0% (6/75) e 18,4% (14/76) nos cães domiciliados e 12,6% (17/135) e 9,6% (11/115) nos errantes, respectivamente. Não houve diferenças estatisticamente significativas entre sexo, idade, raça e a freqüência de soropositividade ao N. caninum dos cães domiciliados e errantes.

The frequency of anti-Neospora caninum IgG antibodies was studied in 415 serum samples from owned and stray dogs from Salvador and Lauro de Freitas counties. The Indirect immunofluorescence was performed using a cut-off of 1:50. Anti-N. caninum IgG antibodies were detected in 13.3% (22/165) owned dogs and in 11.2% (28/250) stray dogs. The frequencies of males and females seropositivity were 8.0% (6/75) and 18.4% (14/76) for owned dogs and 12.6 % (17/ 135) and 9.6% (11/115) in the stray dogs population, respectively. There were not a statistical significant difference between sex, age, breed and the dogs anti-N. caninum IgG antibodies incidence.