Antibody response in dogs experimentally infected with Leishmania infantum: infection course antigen markers.

Five-month-old beagle dogs were experimentally infected with amastigotes of Leishmania infantum and kept for 14 months. Infection course was monitored by clinical examination, serum protein variations, and levels of specific antibodies against Leishmania estimated by indirect immunofluorescence test and Western blotting (WB). Infected animals developed notable changes in serum protein levels reaching maximum protein concentrations 2-3 months postinfection (p.i.) related to the gamma-globulin fraction. Specific antibody titers were in good agreement with the serum protein rise, reaching immunofluorescence values of over 1:800 3 months p.i. Serial Western blotting analysis with L. infantum promastigotes protein showed a strong response against immunodominant antigens of 50-57, 42, and 29 kDa during most of the studied period with immunofluorescence titers of over 1:100 and in addition the response was remarkably homogeneous among the infected dogs. Immunoreactivity patterns displayed time-related variations; the response against 29 and 50-57 kDa was seen very early, followed by the reaction around 42, 76, and 86 kDa. In addition the recognition of peptides around 34-35.4 and 26 kDa was restricted to the acute phase of the experimental infection. Preliminary results obtained in naturally infected dogs seem to support the predictive value of the WB.