They say the hybrid embryos will be used purely for research and would never be allowed to develop beyond 14 days when they are still smaller than a pinhead.

This is first for British science and the team from Newcastle University say they hope the research will lead to new stem-cell treatments for disorders such as Parkinson's disease, stroke and diabetes.

The hybrid embryos were created by merging human genetic material with cow egg cells which had most of their own genetic material removed and the result produced hybrid embryos which were genetically 99.9 per cent human and 0.1 per cent cow.

While the research is still very much at a preliminary stage and has not yet been verified in a peer-reviewed scientific journal, the scientists say the results were valid, and the hybrid embryos survived for a three day period in the test tube.

The researchers hope that eventually such embryos will survive for up to six days - this would allow time for embryonic stem cells to be taken and grown into mature tissue.

Lead researcher Professor John Burn says the research was licensed in January and some progress has already been made and the research is entirely ethical.

The scientists believe that the work is essential despite critics labeling it as monstrous and immoral; medical bodies and patient groups say such research is vital to achieve a better understanding of disease.

The Newcastle team were issued with a research licence from the Human Fertilisation and Embryology Authority with approval from the Government and the British government is proposing to update current legislation to specifically permit such research.

Experts say the approach is likely to provide stem cells for research without the use of human eggs or normal human embryos and the new legislation will confirm the arrangements for regulation in this area of research.

Mike McCune, M.D., Ph.D., Chief of the Division of Experimental Medicine at the University of California, San Francisco, hailed the study as one with potentially important practical applications. By showing that the same genetic makeup increases susceptibility to immune depletion and impaired immune recovery, the authors provide novel tools that may allow us to predict both those who will progress faster after HIV infection as well as those who might benefit from earlier initiation of HAART, he said.

The study suggests the need for new thinking in HIV-1 management. The current debate about when to initiate antiretroviral therapy might need to be redirected toward first assessing who should be considered for therapy, on the basis of the host genetic endowment, Dr. Ahuja said.

Capt. Gregory Martin, M.D., U.S.N., program director for the Infectious Diseases Clinical Research Program at the Uniformed Services University, said, The finding that CCL3L1-CCR5 genetic makeup has its greatest impact on immune recovery when persons were started on therapy with CD4+ counts of less than 350 cells/mm3 highlights the importance of starting persons on therapy earlier rather than later.

Joel Kupersmith, M.D., chief research and development officer for the Veterans Health Administration, said, Dr. Ahuja's groundbreaking research is in line with the VA's mission of providing personalized medicine for veterans. We look forward to the translation of these findings into improved care for HIV-infected veterans and HIV patients worldwide. The Veterans Health Administration is a part of the U.S. Department of Veterans Affairs and in part funded this work.

The CD4+ restoration was more closely associated with number of copies of CCL3L1 than with CCR5 status. This suggests that drugs that mimic or amplify the activity of CCL3L1 could be effective for HIV treatment, Dr. Dolan said.

The University of Texas Health Science Center at San Antonio is the leading research institution in South Texas and one of the major health sciences universities in the world. With an operating budget of $576 million, the Health Science Center is the chief catalyst for the $15.3 billion biosciences and health care sector in San Antonio's economy. The Health Science Center has had an estimated $35 billion impact on the region since inception and has expanded to seven campuses in San Antonio, Laredo, Harlingen and Edinburg. More than 23,000 graduates (physicians, dentists, nurses, scientists and allied health professionals) serve in their fields, including many in Texas. Health Science Center faculty are international leaders in cancer, cardiovascular disease, diabetes, aging, stroke prevention, kidney disease, orthopaedics, research imaging, transplant surgery, psychiatry and clinical neurosciences, pain management, genetics, nursing, allied health, dentistry and many other fields.

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