Vet. Res. 35 (2004) 83-90
DOI: 10.1051/vetres:2003039

Lack of an effect of a commercial vaccine adjuvant on the development of postweaning multisystemic wasting syndrome (PMWS) in porcine circovirus type 2 (PCV2) experimentally infected conventional pigs

Ana Resendes^a, Joaquim Segalés^a, Mònica Balasch^b, Maria Calsamiglia^a, Marina Sibila^a, Heinz Ellerbrok^c, Enric Mateu^a, Joan Plana-Durán^b, Annette Mankertz^d and Mariano Domingo<sup>a

a</sup>  Centre de Recerca en Sanitat Animals (CReSA), Departament de Sanitat i d'Anatomia Animals, Facultat de Veterinària, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
^b  Fort Dodge Veterinaria S.A., Carretera Camprodon s/n, La Riba, 17813 Vall Bianya (Girona), Spain
^c  Robert Koch Institut, P22 Virology, Nordufer 20, 13353 Berlin, Germany
^d  Robert Koch Institut, P24 Xenotransplantation, Nordufer 20, 13353 Berlin, Germany

(Received 25 March 2003; accepted 17 July 2003)

Abstract - The objective of this study was to evaluate the effect of a commercial vaccine adjuvant on the clinical and pathological outcome of PCV2 experimentally infected 8 to 9-week-old conventional pigs. Forty-four pigs were divided into four groups: non-infected control pigs, pigs that received a vaccine adjuvant, pigs inoculated with PCV2, and pigs inoculated with PCV2 together with the vaccine adjuvant. Infection was monitored until 69 days post-inoculation (PI). Some PCV2 inoculated pigs had hyperthermia, but no other clinical signs were recorded. No characteristic PMWS gross or microscopic lesions were observed in any of the pigs. PCV2 DNA was detected in lymphoid tissues by in situ hybridisation in 6 PCV2 inoculated pigs on day 69 PI. All PCV2 inoculated pigs seroconverted between days 21 and 49 PI, shortly after viremia detection. Moreover, viremia was detected between days 7 and 69 PI using PCR. A peak of the virus load was detected by real-time quantitative PCR between days 14 and 21 PI. There were no significant differences in the proportion of PCV2 positive serum and in the viral load between PCV2 and PCV2 + adjuvant inoculated pigs. Although PMWS was not reproduced in neither PCV2 nor PCV2 + adjuvant inoculated pigs, viremia detection and seroconversion indicated that all PCV2 inoculated pigs developed a chronic long-term asymptomatic infection. An increase of PCV2 replication was not observed in pigs inoculated with the adjuvant. These results indicate that the principle of immunostimulation may not be applicable under the experimental conditions used, suggesting that not all adjuvants used in commercial vaccines are capable of triggering mechanisms for PMWS development.

Key words: porcine circovirus type 2 (PCV2) / pigs / vaccine adjuvant / real-time quantitative PCR / in situ hybridisation

Corresponding author: Joaquim Segalés joaquim.segales@uab.es

© INRA, EDP Sciences 2004