One of the favorite arguments from scientists is their need to develop new embryonic stem cell lines for research because the existing cell lines are contaminated with viruses from the mouse ‘feeder cells’ the embryonic stem cell lines are grown on.

A journal article just out states that the human embryonic stem cell lines are free from virus infection despite the close contact with the mice cells.

No Evidence for Infection of Human Embryonic Stem Cells by Feeder Cell-Derived Murine Leukemia Viruses
Michal Amita, Monica E. Winklerb, Sandra Menkeb, Eva Brüningb, Kristina Büscherc, Joachim Dennerc, Axel Haverichb, Joseph Itskovitz-Eldora, Ulrich Martinb
Stem Cells Vol. 23 No. 6 June 2005, pp. 761-771

a Department of Obstetrics and Gynecology, Rambam Medical Center, Faculty of Medicine, The Technion, Haifa, Israel; b Leibniz Research Laboratories for Biotechnology and Artificial Organs (LEBAO), Hannover Medical School, Hannover, Germany;
c Robert Koch Institute, Berlin, Germany

Correspondence: Ulrich Martin, Ph.D., Leibniz Research Laboratories for Biotechnology and Artificial Organs (LEBAO), Podbielskistr. 380, 30659 Hannover, Germany. Telephone: 49-511-906-3533; Fax: 49-511-906-3569; e-mail:

Until recently, culture and expansion of nondifferentiated human embryonic stem cells (hESCs) depended on coculture with murine embryonic fibroblasts. Because mice are known to harbor a variety of pathogens, such culture conditions implicate the risk of xenozoonoses. Among these pathogens, endogenous retroviruses, including murine leukemia viruses (MuLVs), are of special importance. It is well known that some strains cause pathogenic (e.g., leukemic) effects and that xenotropic, polytropic, and amphotropic MuLVs are able to infect human cells.

In view of potential clinical applications of hESC lines, it is therefore imperative to investigate potential infection of hESCs by mouse feeder cell-derived viruses. As a first step towards a comprehensive infection risk assessment, we have analyzed embryonic fibroblasts derived from different mouse strains for expression and release of xenotropic, polytropic, and amphotropic MuLVs. Moreover, several hESC lines have been investigated for expression of specific receptors for xenotropic/polytropic MuLVs, as well as for MuLV infection and expression.

Evidence for expression of humantropic MuLVs was found in cultures of mouse embryonic fibroblasts (MEFs). Moreover, expression of specific receptors for xenotropic/ polytropic MuLV on human HEK293 and hESC lines and infection after coculture with an MuLV-producing mink cell line could be demonstrated. In contrast, no evidence of MuLV transmission from MEFs to human HEK293 cells or to the hESC lines I-3, I-6, I-8, and H-9 has been obtained.

Our results suggest that recently established hESC lines are free of MuLV infections despite long-term close contact with MEFs.

Author Profile

Jennifer Lahl, CBC President
Jennifer Lahl, CBC President
Jennifer Lahl, MA, BSN, RN, is founder and president of The Center for Bioethics and Culture Network. Lahl couples her 25 years of experience as a pediatric critical care nurse, a hospital administrator, and a senior-level nursing manager with a deep passion to speak for those who have no voice. Lahl’s writings have appeared in various publications including Cambridge University Press, the San Francisco Chronicle, the Dallas Morning News, and the American Journal of Bioethics. As a field expert, she is routinely interviewed on radio and television including ABC, CBS, PBS, and NPR. She is also called upon to speak alongside lawmakers and members of the scientific community, even being invited to speak to members of the European Parliament in Brussels to address issues of egg trafficking; she has three times addressed the United Nations during the Commission on the Status of Women on egg and womb trafficking.