• Journal of Microbiology and Biotechnology
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• v.18 no.3
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• pp.585-590
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• 2008

Human tropic Porcine Endogenous Retroviruses (PERVs) are the major concern in zoonosis for xenotransplantation because PERVs cannot be eliminated by specific pathogen-free breeding. Recently, a PERV A/C recombinant with PERV-C bearing PERV-A gp70 showed a higher infectivity (approximately 500-fold) to human cells than PERV-A. Additionally, the chance of recombination between PERVs and HERVs is frequently stated as another risk of xenografting. Overcoming zoonotic barriers in xenotransplantation is more complicated by recombination. To achieve successful xenotransplantation, studies on the recombination in PERVs are important. Here, we cloned and sequenced proviral PERV env sequences from pig gDNAs to analyze natural recombination. The envelope is the most important element in retroviruses as a pivotal determinant of host tropisms. As a result, a total of 164 PERV envelope genes were cloned from pigs (four conventional pigs and two miniature pigs). Distribution analysis and recombination analysis of PERVs were performed. Among them, five A/B recombinant clones were identified. Based on our analysis, we determined the minimum natural recombination frequency among PERVs to be 3%. Although a functional recombinant envelope clone was not found, our data evidently show that the recombination event among PERVs may occur naturally in pigs with a rather high possibility.

• Journal of Embryo Transfer
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• v.25 no.4
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• pp.221-227
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• 2010

Early cleavage is a reliable prognostic tool for successful embryo transfer in assisted reproduction because early cleaved embryo show better pregnancy rate after transfer. There for, preparation of good embryo recipient is important factor to optimize efficiency of pig cloning. The present study was performed to evaluate the effect of early cleavage on the in vivo development of cloned embryos and to analyze breed, parity and estrous synchrony to optimize recipient for pig cloning. In vitro matured porcine oocytes derived from local slaughterhouse and fibroblasts derived from miniature pig fetuses were used for somatic cell nuclear transfer (SCNT). Reconstructed embryos were transferred to recipient pigs on the same day of SCNT or after 1~2 days of in vitro culture for selecting early cleaved embryos. Breed, parity and date of standing estrous of recipients were recorded for analysis. After 25~35 days after embryo transfer pregnancy was diagnosed using ultrasonography, and pregnant recipients were monitored till delivery. Between purebred and crossbred, no significant difference was founded in both pregnancy and delivery rates. However, early cleaved embryos showed significantly higher pregnancy (46.2%) and delivery (12.8%) rates compared to non-selectively transferred group (24.8% and 4.5%, respectively). The results also showed that the recipients showing standing estrous on the same day of SCNT and less than 4 parities were most suitable for pig cloning.