Association of bovine viral diarrhea virus with day-7 bovine embryos produced under differente culture conditions = Asociación del virus de la diarrea viral bovina con embriones bovinos de 7 días producidos bajo diferentes condiciones de cultivo
Bovine viral diarrhea virus (BVDV) is an important pathogen of cattle that has been frequently associated with in vitro produced (IVP) embryos. The zona pellucida (ZP) of IVP embryos shows higher affinity for BVDV than the ZP of in vivo produced embryos and treatments that can eliminate BVDV from in vivo produced embryos are unsuccessful in the case of the IVP embryos. The aim of the present study was to investigate whether different culture conditions change the affinity of the ZP of day-7 IVP bovine embryos to BVDV. Morula and blastocysts were produced under four different culture systems: 1) in vitro culture in Menezo's B2 media and coculture with bovine oviductal epithelial cells (B2-BOEC culture); 2) in vitro culture in modified synthetic oviductai fluid with aminoacids (mSOFaa culture); 3) in vivo culture in ligated oviducts of synchronized sheep; and 4) in vivo produced embryos flushed from superovulated cows seven days after breeding. The embryos were exposed to BVDV for 24 hours, and washed 10 times and treated with trypsin, according to the recommendations of the international Embryo Transfer Society. After pooling the embryos in groups of five, the samples were homogenized and tested for the presence of BVDV by indirect immimoperoxidase assay (IIP) or reverse transcription-polymerase chah reaction (RT-PCR). No significant differences were found between the two detection systems but the IIP assay tended to detect a higher number of positive sarnples. According to the IIP assay, the mSOFaa group had a significantliy higher number of positive findings (78.6%) followed by the B2-BOEC group (32.1%), and the oviductal culture group (7.1%). None of the in vivo embryos tested positive for BVDV. These results show that different culture conditions in which embryos develop alter the way the ZP interacts with pathogens. The oviductal culture of in vitro produced zygotes seems to be beneficial in reducing the affinity of the ZP to BVDV and the washes and trypsin treatments applied to these embryos after culture appear to be more effective than in embryos completely produced in vitro.
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