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Resumen de Seguimiento de la respuesta inmune generada tras la administración de varias proteínas de Leishmania infantum en ratones BALB/c. Análisis de la diversidad generada en el repertorio CDR3 y su relación con la inmunización y el desarrollo de la patología inducida por Leishmania

Lina Jimena Cortés Salinas

  • Cutaneous leishmaniasis is a common tropical disease and at present it is considered a worldwide health problem. As deduced from a large number of publications the understanding of the components involved in susceptibility or disease control has substantially increased. They have provided, moreover, clues to design effective vaccines against this fastidious pathogen. Until now a large number of vaccines have been tested. Although some of them can generate a robust response to control the disease in animal models, only one is in phase 1 trial in humans. Thus, further research is needed to have a deeper understanding of the infection and the disease. The use of vaccine subunits composed by characterized antigens could be an effective solution to control Leishmaniasis. Actually there is no vaccine developed for humans. Therefore intense studies in heterologous system are crucial to understand the mechanisms of the immune response against the pathogen.

    In the present work the protective and immunogenic capacity of the Q Protein was evaluated in a L. major-susceptible BALB/c mouse model. The Protein Q is a molecule formed by the genetic fusion of fragments from the acidic ribosomal proteins LiP2a, LiP2b and LiP0 and the histone H2A (Soto, Requena et al. 1998). Due to the importance of the formulations for the effectiveness of any vaccine or pharmacological agent five different presentations of Q were used to inoculate the animals. The cellular response was evaluated measuring the expression levels of cytokine involved in Th1 or Th2 responses. Moreover, the production of different antibodies types (IgM, IgG, IgG1 and IgG2a) was used to determine the humoral response against the Q protein and its components, individually. All tested formulations induce a mixed Th1/Th2 response characterized by INF-¿, IL-10 e IL-13 expression combined with production of IgG1 and IgG2 antibodies. At the same time, we found that the immunogenic potential of the chimeric Q Protein was mainly due, in our assays, to the LiP2a and LiP2b determinants.

    Another relevant approach of this work was the analysis of the diversity of the TCR repertoire triggered after the immunization with Q as a recombinant protein and as a DNA vaccine. Here, we analyzed the TCRVß repertoire by complementarity-determining region 3 (CDR3) length spectratyping. After the stimulation with the Q protein, the mice inoculated with the pcDNA3Q (DNA vaccine) showed significant differences in the TCR repertoire relative to the mice inoculated with the Q recombinant protein. T Vß9, Vß12, Vß16 and Vß18 were the populations that mostly varied in this TCR-analysis comparison.

    After the evaluation of the humoral and cellular responses against the Q, we challenge the mice inoculated with the five different formulations using L. major parasites as the infection agent. Only two out of the five formulations tested generated a delay in the appearance of the footpad inflammation. Interestingly, this delay was only observed in 50% of the infected animals. The infected animals generated mixed Th1/Th2 responses against SLA. However when the spleen cells of these animals were stimulated with SLA they produced INF-¿ and iNOS.

    The TCR repertoire was also evaluated in the challenged animals. Similarities in the spectratype profiles were found in the mice that showed a delay in the development of footpad inflammation. Splenocytes of the infected animals stimulated with the Q protein presented changes in the same families (Vß9, Vß12, Vß16 and Vß18) that the animals that had been immunized but not challenged. Animals in which a delay in footpad inflammation was not detected showed significant differences in the T Vß2 and Vß12 families relative to the animals in which such delay was not observed, suggesting that these populations may be involved in the protective response against L. major.

    Soto, M., J. M. Requena, et al. (1998). "Multicomponent chimeric antigen for serodiagnosis of canine visceral leishmaniasis." J Clin Microbiol 36(1): 58-63.

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