Rederivation of inbred strains of mice by means of embryo transfer.

Embryo transfers were performed to rederive six inbred strains of mice, A/He, BALB/cByJ, BALB/c Lac, B10.BR/SgSnJ, C57BL/6J and DBA/2J. The aim was to determine whether it is possible to eliminate pathogens like mouse hepatitis virus (MHV) and Pasteurella pneumotropica (P.p.). The embryos were collected, handled and transferred into the oviduct of day one pseudopregnant SPF surrogate mothers under aseptic conditions. In 40.5% of the transfers, embryos developed to term. With respect to surrogate mothers delivering viable litters, 47.9% of the transferred embryos were born alive. Out of these 93.5% were reared. Virological and bacteriological examination of embryo donors verified the presence of P.p. and of antibodies against MHV in all strains. In some embryo donors P.p. could be isolated even from the uterine mucosa. However, neither in the surrogate mothers nor in the offspring could P.p. and antibodies against MHV be detected. Further bacteriological examination revealed that the offspring carried only the microbial flora received from the surrogate mother. The results indicate that embryo transfer is an appropriate tool to rederive mouse strains. In contrast to hysterectomy rederivation, embryo transfer has the advantage of avoiding postimplantational vertical transmissions of infections.