Adaptative immune responses in the respiratory tract of FMD-vaccinated cattle after oronasal infection

PEGA, JUAN FRANCO; BUCAFUSCO, DANILO; DI GIACOMO, SEBASTIÁN; SCHAMMAS, JUAN MANUEL; MALACARI, DARIO; CAPOZZO, ALEJANDRA; RODRÍGUEZ, LUIS; BORCA, MANUEL VÍCTOR; PÉREZ FILGUEIRA, MARIANO

Jerez de la Frontera

Congreso; Appliance of science in the progressive control of FMD; 2012

The European Commission for the control of Foot-and-Mouth disease (EuFMD)

Introduction: FMDV aerosol-infection in naïve cattle induced a rapid and vigorous genuine local antibody secretion, showing a time-course and isotype profile consistent with an efficient T-independent antibody response. Here, we report the kinetics of appearance of specific antibody-secreting cells (ASC) in lymphoid organs along the respiratory tract induced in vaccinated cattle following aerogenous administration of FMDV. Materials and methods: Animals (n=16) were intramuscularly vaccinated in the neck with a high-payload O1 Campos FMD oil vaccine, and FMDV-specific ASC were studied at 7 and 29 days post-vaccination (dpv) and 1 to 6 days post-oronasal homologous challenge (at 30 dpv, n=2 each time). Mononuclear cells were obtained from prescapular (PSL) and mandibular lymph nodes (ML), pharyngeal tonsil, lateral and medial retropharyngeal lymph nodes (MRL), tracheobronchial lymph nodes (TBL) and spleen, and studied using a FMDV-ASC ELISPOT previously developed. Results: Antibody responses induced by vaccination were found in the PSL draining the inoculation site and followed a maturation process throughout 29 dpv. Nevertheless, a modest though consistent IgM-mediated stimulation was detected at 29 dpv in all mucosal-related lymphoid tissues. None of the animals showed clinical symptoms after infection, and mucosal responses remained low at 2-3 dpi. However, class-switch was observed in the most stimulated organs, TBL and MRL, where IgG1- ASC were detected at 3 and 4 dpi. Naïve- infected animals showed responses starting at 4 dpi, being almost exclusively IgM-ASC and class-switch to IgG1 was only observed from 6 dpi in ML. The early class-switch in vaccinated-infected cattle augmented at 5 and 6 dpi to include all analyzed tissues. Discussion: Systemic vaccination may induce a basal stimulation in lymphoid tissues associated to the cattle respiratory tract, showing an IgM-mediated pattern even at late times post-vaccination (29 dpv). Further oronasal infection did not produce clinical symptoms in none of the animals, while promoting an early class switch and rapid response compatible to a secondary response.