Early and sustained anti-Trypanosoma cruzi IgG reactivity in experimentally infected dogs detected with chimeric recombinant antigens

Chimeric recombinant antigens are used in canine Trypanosoma cruzi serology, but the timing of IgG reactivity against them after infection has not been described. We characterized the temporal profile of anti- T. cruzi IgG reactivity against four chimeric recombinant antigens (IBMP-8.1, IBMP-8.2, IBMP-8.3 and IBMP-8.4) in 36 mixed-breed dogs from a vaccine efficacy trial that were experimentally infected with T. cruzi . A total of 144 serum samples collected before infection and at 30, 60 and 180 days post-infection were tested by indirect ELISA. A previously established latent class analysis framework based on the four IBMP antigens was used to define the consensus serological status and as the comparator for a canine-adapted commercial Gold ELISA Chagas assay. All four IBMP antigens were non-reactive in every pre-infection sample. At 30 days post-infection, 35 of 36 (97.2%) animals were reactive with IBMP-8.2, 32 (91.4%) with IBMP-8.3 and 30 (85.7%) with IBMP-8.1 and IBMP-8.4. By 60 days, all 36 animals were reactive with three IBMP antigens and 34 (94.4%) with IBMP-8.1. The commercial comparator showed slower seroconversion kinetics, with 26 of 36 (74.3%) reactive animals at 30 days and all 36 only from 60 days onward. Reactivity against th IBMP antigens was detectable by 30 days and persisted through 180 days post-infection, spanning the acute phase and the onset of the chronic phase. Because the cohort was small and no parasitological reference test was applied, these results describe antibody reactivity and are not estimates of diagnostic accuracy.