Co-existence of multiple strains of porcine circovirus type 2 in the same pig from China.

Pigs are often co-infected by different viral strains from the same virus. Up to now, there are few reports about co-existence of different porcine circovirus type 2 (PCV2) strains in China. The aim of this study was to evaluate it in Chinese swine herds. 118 PCV2 positive DNAs isolated from diseased pigs identified by classic PCR were re-detected using a modified differential PCR assay. The results indicated that co-existence rates of PCV2 were 32.2% (38/118) in diseased pigs and 0% (0/41) in asymptomatic pigs. Four PCV2 complete genomes were cloned from two co-infected samples and their nucleotide (nt) identities were 95%-97.3%. The phylogenetic analysis showed that four PCV2 strains were divided into different genotypes, PCV2a, PCV2b, PCV2d and PCV2e, respectively. In addition, co-existence were not detected in 41 serum samples from healthy pigs but PCV2 single infection (31.7%, 13/41) existed. These data revealed that the co-existence of different strains of PCV2 might contribute to the development of more severe clinical symptoms for pigs. This is the first report confirming the co-existence of different PCV2 strains in Chinese swine herds. Meanwhile, this study could help us to understand new infection and prevalence forms of PCV2 clinically.

An easy-to-use site-directed mutagenesis method with a designed restriction site for convenient and reliable mutant screening.

Site-directed mutagenesis (SDM) has been a very important method to probe the function-structure relationship of proteins. In this study, we introduced an easy-to-use, polymerase chain reaction (PCR)-based SDM method for double-stranded plasmid DNA, with a designed restriction site to ensure simple and efficient mutant screening. The DNA sequence to be mutated was first translated into amino acid sequence and then the amino acid sequence was reversely translated into DNA sequence with degenerate codons, resulting in a large number of sequences with silent mutations, which contained various restriction endonuclease (RE) sites. Certain mutated sequence with an appropriate RE site was selected as the target DNA sequence for designing a pair of mutation primers to amplify the full-length plasmid via inverse PCR. The amplified product was 5'-phosphorylated, circularized, and transformed into an Escherichia coli host. The transformants were screened by digesting with the designed RE. This protocol uses only one pair of primers and only one PCR is conducted, without the need for hybridization with hazardous isotope for mutant screening or subcloning step.

[Preparation and primary analysis of monoclonal antibodies against VP5 protein of chicken infectious bursal disease virus].

Infectious bursal disease virus (IBDV), the causative agent of a highly contagious disease in chickens, carries a small nonstructural protein (NS). In this study, vvIBDV Gx-VP5 genes were cloned into plasmid pET30a( + ) and expressed in E. coli with IPTG inducing. BALB/c mice were immunized with the purified recombinant fusion protein. SP2/0 myeloma cells and spleen cells of BALB/c mice were fused by PEG(MW1500), three hybridoma cell lines were examined by indirect ELISA and clone for three times by limited dilution, and were named as 4B4, 6D12, 3E8. The subtype of the monoclonal antibodies were IgG1 with a subtype identified ELISA kit, and light chains were kappa. The ascites titers of monoclonal antibodies were 5 x 10(4), 3.5 x 10(4), 3 x 10(4) by indirect ELISA, respectively. Indirect ELISA and Western blot results showed that the monoclonal antibodies only acted with VP5 protein, IF analysis indicated that three monoclonal antibodies acted with IBDV Gt. There were specific fluorescence in detected Vero E6 cells which transient expressed VP5 protein by IFA. Therefore, monoclonal antibodies specific to IBDV VP5 proteins are specific method for detected VP5 proteins, and base on establish stabilize expressed VP5 protein Vero cell lines to research IBDV VP5 protein function.

[Molecular detection of specific HPV types in Condylomata acuminata].

To detect HPV in genital warts (Condylomata acuminata, CA) for infection rate and association of specific HPV types between males and females, and to provide support for the development of HPV vaccines, we designed HPV type-specific oligonucleotide primers to amplify DNA fragments encoding L1 viral capsule protein. SSP-PCR was conducted in duplication for each CA sample from male and female patients. DNA of TA-cloned HPV was used as positive control, and deionized H2O was used as negative control. A total of 22 clinical samples, 13 from males and 9 from females, was collected from patients diagnosed with CA at hospitals in Beijing and Handan. HPV viral DNA was amplified in all 22 samples analyzed, with 100% detection rate. TA-cloning and sequencing of the PCR products confirmed correct amplification of HPV type-specific fragments. Of the 13 samples from males, 5 were infected with HPV6, 6 with HPV11, and 2 with HPV6 + HPV11. Of the 9 samples from females, 3 were infected with HPV6, 2 with HPV11, and 4 with both HPV6 and HPV11 infection. In addition, high-risk types HPV16, HPV18, HPV33, HPV35, HPV45, HPV54, HPV56 and HPV58 were also detected in 4 female samples that were mixed with cervical cell debris during sample collection. However, no HPV types other than HPV6 and HPV11was detected in all CA-only samples in this study. We have established a sensitive and reliable laboratory procedure for HPV detection and classification. Using the method, we reached 100% detection rate of HPV in the CA samples. Our results confirm that HPV6 and HPV11 are primarily responsible for CA, and there is no specific association of HPV types between warts in males and females.