Abstract:

To explore the pathogenicity and immunogenicity of chimeric porcine circovirus (PCV1-2) to piglets, several healthy conventional piglets were inoculated with PCV1-2, the clinical evaluation, gross pathology and histopathology, virus load in sera and tissues, and serology were determined. The results showed that there were no significant differences in the average gains and feed conversion efficiency of piglets between the PCV1-2-inoculation and the control, and there were not visible clinical signs and gross lesions in PCV1-2-inoculated piglets, although slight microscopic lesions were observed. The antibodies against porcine circovirus type 2 (PCV2) ORF2 protein in sera began to converse to positive on 14 days post inoculation (DPI), and were 100% positive on 28 DPI, which revealed that the PCV1-2 induced a quick specific antibody response to the PCV2 ORF2 protein antigen in piglets. The results of real-time PCR showed that the DNA loads of PCV1-2 in sera increased gradually and peaked on 28 DPI, declined quickly thereafter. The DNA load of PCV1-2 in tissues was the highest in lung lymph node and lowest in heart on 35 DPI, when the piglets were slaughtered. However, it was difficult to detect the PCV1-2 DNA in sera and tissues with conventional PCR, which suggested that the inoculation with PCV1-2 could only cause a slight infection of piglets. These data indicated that the chimeric PCV1-2 was with good immunogenicity to piglets but was attenuated obviously.