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Papers by Antonio Callen

Delayed-type hypersensitivity (DTH) is revealing cellular mediated immunity towards an antigen an... more Delayed-type hypersensitivity (DTH) is revealing cellular mediated immunity towards an antigen and can be adapted for vaccine compliance tests. This study aimed to confirm this potential for PCV2 vaccination under Italian field conditions. First farm: thirty three-week-old just-weaned piglets born from unvaccinated sows were either vaccinated (n=15) with CIRCOVAC IM 0.5mL or left unvaccinated (n=15). Five weeks later, the pigs were intradermally inoculated with 0.1-0.2mL of CIRCOVAC antigen solution in the lower abdomen area. The diameter of skin reaction (erythema) at the point of inoculation was visually inspected 24h post-inoculation. Second farm: 30 five-week-old piglets born from CIRCOVAC-routinely-vaccinated sows were either vaccinated with CIRCOVAC or left unvaccinated. The DTH reaction was analogously assessed, both before vaccination and 5 weeks post-vaccination. Piglets born from vaccinated sows were bled at weaning and all experimental animals at 5 weeks post-vaccination . Antibodies were titrated using an in-house ELISA or a seroneutralization technique. First farm: only 33% of vaccinated piglets showed high anti-PCV2 ELISA titres following vaccination. Vaccinated pigs exhibited consistent and significantly higher seroneutralizing titres than unvaccinated pigs indicating a proper vaccine take. The proportion of pigs showing erythema (100% vs. 33%) and the average diameter (25\ub115 mm vs. 4\ub17 mm) was significantly higher (p<0.01) for the vaccinated animals. Second farm: piglets born from vaccinated sows consistently displayed high ELISA titres and a mild reaction (9\ub14mm) to the DTH test before vaccination. Five weeks later, ELISA titres were significantly decreased (p<0.01) in unvaccinated pigs compared to vaccinated ones. The diameter of the skin reaction strongly increased (p<0.01) in vaccinated pigs (24\ub14mm) whereas it tended to decrease in unvaccinated ones (8\ub12mm). These results confirmed the potential of intradermal application of PCV2 antigen as a CIRCOVAC vaccination compliance test

BMC Veterinary Research, Apr 16, 2018

Veterinary Microbiology, May 1, 2011

Post-weaning multisystemic wasting syndrome (PMWS) clinical expression under field conditions is ... more Post-weaning multisystemic wasting syndrome (PMWS) clinical expression under field conditions is modulated by the pig genetic background

Veterinary Research, 2016

This study aimed to determine the porcine circovirus type 2 (PCV2) serological and virological dy... more This study aimed to determine the porcine circovirus type 2 (PCV2) serological and virological dynamics in piglets vaccinated at different ages in a PCV2 subclinical infection (PCV2-SI) scenario. Six hundred and forty-four 2 weekold healthy piglets were selected and distributed into four treatment groups: vaccination at 3, 6 or 10 weeks of age (3W-VAC, 6W-VAC and 10W-VAC groups, respectively) and unvaccinated pigs (NON-VAC group). Blood (n = 112 pigs) and oral fluid (OF) (n = 40 pens) samples were taken throughout the study to assess PCV2 load, humoral immunity and viral genotyping. Percentage of PCV2-DNA positive sera mainly raised by 10 weeks of age, being maximum at 14 weeks of age, and then started to decrease at 18 and 25 weeks of age. Specifically, PCV2 vaccination at 3 or 6 weeks of age yielded similar results, since they produced an earlier seroconversion and reduced, at different sampling points, the proportion of viremic animals in comparison to the unvaccinated group. In contrast, PCV2 vaccination at 10 weeks of age only achieved such reduction at 25 weeks of age; in this case, vaccination coincided with the increase of the percentage of viremic pigs in the population. Both serological techniques used in sera and OF offered similar results with a high and statistically significant correlation. In contrast, a higher percentage of PCV2 DNA positivity was detected in OF in comparison with sera. In conclusion, under the present study conditions, the optimal time for PCV2 piglet vaccination was at either 3 or 6 weeks of age.

Porcine Health Management, 2015

The present work describes the serum haptoglobin (Hp) dynamics in piglets vaccinated and non-vacc... more The present work describes the serum haptoglobin (Hp) dynamics in piglets vaccinated and non-vaccinated with a commercial porcine circovirus type 2 (PCV2) vaccine at 3 weeks of age, and its relationship with the average daily weight gain (ADWG). The field study was carried out on two farms (A and B) with a previous clinical history of PCV2-systemic disease (PCV2-SD). The aim of the study was to assess whether Hp could be used as a surrogate marker of PCV2 vaccine efficacy. PCV2 infection was confirmed by quantitative real time PCR (qPCR) in pigs from both farms, but PCV2-SD was only diagnosed in farm A. No statistically significant relation was found between serum Hp concentration and the percentage of qPCR positive animals and the treatment applied (PCV2 vaccination) in both farms. On the other hand, using linear regression analysis, a significant negative correlation between the area under the curve of Hp (AUC Hp) and ADWG was observed for farm A (p < 0.00001) and B (p = 0.01). Based on the obtained determination coefficient (R 2) values, AUC Hp explained 20.0 and 11.6% of the observed ADWG for farms A and B, respectively. The present study supports that the measurement of acute phase proteins may be an indicator of ADWG in pig farms, but it was not apparently feasible to use the serum Hp concentration as a surrogate marker of PCV2 vaccine efficacy.

The Veterinary Journal, 2013

Anaporc Revista De La Asociacion De Porcinocultura Cientifica, 2012