Comparative evaluation of PRRS in vaccinated and naïve pigs

Researchers from the Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia-Romagna (IZSLER) in Italy evaluated the time-course of the immune response to a field Porcine Respiratory and Reproductive Syndrome virus (PRRSV) strain in PRRS-naïve, untreated pigs and in vaccinated pigs.

The vaccinated pigs (four groups) were treated with an attenuated PRRS vaccine, its adjuvant, an inactivated PRRS vaccine and an irrelevant, inactivated Porcine Circovirus type 2 (PCV2) vaccine, respectively.
PRRSV infection was confirmed in all groups by PCR and antibody assays. The antibody response measured by ELISA took place earlier in pigs injected with the live attenuated vaccine, which also developed a much stronger serum-neutralizing antibody response to the vaccine strain. Yet, no clear protection was evidenced in terms of viremia against the field virus strain, which showed 11.1% nucleotide divergence in ORF7 from the vaccine strain.
In vitro, the interferon (IFN)-gamma response to PRRSV was almost absent on PVD 60 in all groups under study, whereas the prevalence of interleukin (IL)-10 responses to PRRSV was fairly high in PCV2-vaccinated animals, only.
Results indicate that distinct patterns of immune response to a field PRRSV strain can be recognized in PRRS-vaccinated and naïve pigs, which probably underlies fundamental differences in the development and differentiation of PRRSV-specific immune effector cells.
This study has been published in Res Vet Sci. 2010.
[Source: Elsevier Science]

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