Pogranichnyy R M, Yoon K J, Harms P A, Swenson S L, Zimmerman J J, Sorden S D
Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames 50011, USA.
Viral Immunol. 2000;13(2):143-53. doi: 10.1089/vim.2000.13.143.
A longitudinal study was conducted to characterize the immune response of young swine to infection with porcine circovirus type 2 (PCV-2). Five 8-week-old cesarean-derived, colostrum-deprived pigs were inoculated intranasally and intramuscularly with a field isolate of PCV-2 at a concentration of 10(4) TCID50/mL. Along with monitoring for clinical signs and viremia, serum samples were collected from all pigs at day 0 and thereafter every 7 days postinoculation (PI) until the termination of the study on day 35 PI. No clinical signs were observed in any of the animals during the study period. In all pigs, PCV-2 was detected by polymerase chain reaction (PCR) in serum samples collected on days 7, 14, and 21 PI. Viral DNA and antigens were detected by in situ hybridization and immunohistochemistry in tonsil, spleen, medial iliac lymph nodes, and ileum collected from each pig at the end of the study. Collectively, naïve young swine were shown to be susceptible to PCV-2. Virus-specific antibody was detected by an indirect fluorescent antibody (IFA) assay on day 14 PI, but virus-neutralizing antibody was not detected until day 28 PI. As neutralizing antibodies developed, cross-reactivity with PCV type 1 (PCV-1) also developed on the IFA test. Western immunoblot analysis revealed three PCV-2 proteins with molecular masses of 28 kd, 28.5 kd, and 35 kd. The 35-kd protein was also demonstrated in PCV-1, suggesting that this protein induced the cross-reactivity between PCV types 1 and 2. Antibody to the 28-kd protein was detected on day 14 PI and later, indicating that this protein was the most immunogenic. Because of its immunogenicity and specificity to PCV-2, and 28-kd protein might provide the antigenic basis for the development of diagnostic tests for detection of PCV-2 antibody.
开展了一项纵向研究，以表征幼猪对2型猪圆环病毒（PCV-2）感染的免疫反应。五头8周龄剖腹产、未摄入初乳的仔猪经鼻内和肌肉内接种浓度为10(4) TCID50/mL的PCV-2田间分离株。在监测临床症状和病毒血症的同时，于接种后第0天以及此后接种后（PI）每7天从所有仔猪采集血清样本，直至在接种后第35天研究结束。在研究期间，未在任何动物中观察到临床症状。在所有仔猪中，于接种后第7、14和21天采集的血清样本中通过聚合酶链反应（PCR）检测到PCV-2。在研究结束时，从每头仔猪采集的扁桃体、脾脏、髂内侧淋巴结和回肠中，通过原位杂交和免疫组织化学检测到病毒DNA和抗原。总体而言，未接触过病原体的幼猪显示对PCV-2易感。在接种后第14天通过间接荧光抗体（IFA）试验检测到病毒特异性抗体，但直到接种后第28天才检测到病毒中和抗体。随着中和抗体的产生，在IFA试验中也出现了与1型猪圆环病毒（PCV-1）的交叉反应。蛋白质免疫印迹分析显示三种分子量分别为28 kd、28.5 kd和35 kd的PCV-2蛋白。35-kd蛋白在PCV-1中也有显示，表明该蛋白诱导了1型和2型猪圆环病毒之间的交叉反应。在接种后第14天及之后检测到针对28-kd蛋白的抗体，表明该蛋白免疫原性最强。由于其免疫原性和对PCV-2的特异性，28-kd蛋白可能为开发检测PCV-2抗体的诊断试验提供抗原基础。
