Modification of PCV-2 virulence by substitution of the genogroup motif of the capsid protein

Allemandou, Aude; Grasland, Béatrice; Hernandez-Nignol, Anne-Cécile; Kéranflec'h, André; Cariolet, Roland; Jestin, André

The first porcine circovirus (PCV) was discovered in a pig kidney cell line (PK15 ATCC-CCL33) and was called porcine circovirus type 1 (PCV-1) [1] . Experimental infections have shown that PCV-1 is non-pathogenic for pigs [2] . In the 1990s, a new disease called post-weaning multisystemic wasting syndrome (PMWS) emerged in Europe and North America. PMWS-affected animals exhibit growth retardation, pallor and dyspnea. At necropsy, lymph nodes are enlarged and the main histological lesions are lymphocyte depletion with histiocytic inflammatory infiltration of lymphoid tissues [3] . A new circovirus was identified from diseased pigs and was named porcine circovirus type 2 (PCV-2) [4] . Now PCV-2 is recognized as the etiological agent of PMWS and is associated with several diseases designated by the abbreviation PCVD (porcine circovirus-associated diseases) [3] . To diagnose typical PMWS, specific clinical signs and lesions have to be observed together with the detection of PCV-2 antigen or nucleic acid in the lesions [5] . Pigs infected experimentally often developed sub-clinical infection and typical PMWS is hard to reproduce. Most experimental models used PCV-2 infection combined with co-factors such as bacteria, virus or immunostimulation to increase the severity of the clinical signs and the incidence of PMWS [3] . Hence, to qualify the PCV-2 virulence, the virulence definition described by Casadevall et al. can be used [6] . The virulence definition considered lesions and symptoms but also which mechanism or step of viral life cycle is implicated in the expression of virulence as ability to infect the host or ability to replicate.