表达PCV2 ORF2的重组T7噬菌体在猪体内的存留分析OA北大核心

To investigate the persistence of recombinant T7 phage(T7-ORF2)expressing the capsid protein(ORF2)of porcine circovirus type 2(PCV2)in pigs after intramuscular injection into the neck,a study was conducted using 20-day-old piglets negative for PCV2 antigen and antibodies.The piglets were randomly divided into Experimental and Control groups,each containing five pigs.The Experimental group received 1.5 mL of proliferated T7-ORF2 by intramuscular injection in the neck,while the Control group received the same volume of eluent via the same route.Body temperature,clinical symptoms,and mortality were monitored one day before injection and at 10 hours,and 1 to 7 days post-injection.Blood and fecal samples were collected at 1 hour,3 hours,5 hours,10 hours,1 day,3 days,5 days,and 7 days post-injection,and liver,spleen,and inguinal lymph node samples were collected at 10 hours,1 day,3 days,5 days,and 7 days post-injection.Samples were mixed with host bacteria(Escherichia coli strain BLT5403)for plaque assays to analyze the infectivity of T7-ORF2.PCR was performed on genomic DNA extracted from bacterial lysates to detect the ORF2 gene.Immunohistochemistry was used to detect the distribution and persistence of T7-ORF2 in liver,spleen,and inguinal lymph nodes.The results showed that the Experimental group pigs maintained normal body temperature,appetite,water intake,and mental state with no adverse symptoms or mortality during the trial period.Infectious T7-ORF2 was detectable in serum and feces within 5 days post-injection and in liver,spleen,and inguinal lymph nodes within 3 days post-injection.PCV2 ORF2 gene fragments were amplified from bacterial lysates.Immunohistochemistry indicated that T7-ORF2 was gradually cleared from the body,persisting in the spleen for at least 5 days and in the liver and inguinal lymph nodes for at least 7 days.The study demonstrates that T7-ORF2 can enter the bloodstream,liver,spleen,and inguinal lymph nodes of pigs and be excreted in feces,providing data support for the further development of a novel PCV2 vaccine using T7-ORF2.