American researchers have successfully created immune cells resistant to HIV (human immunodeficiency virus). T cells, which are the main target of HIV, were isolated from six HIV positive patients and genetically manipulated to confer resistance. The cells were injected back into the same patients and were able to survive and multiply. The results of the phase I clinical trial do not provide a cure, but suggest gene therapy may be a viable treatment in the future.
'This is the first successful example of targeted genetic modification of the DNA code in patients, and therefore this has implications for the development of corrective gene therapy for a number of monogenic gene disorders of the bone marrow, such as sickle cell anemia, that are currently incurable', said Dr Carl June, lead researcher and director of translational research at the Abramson Cancer Centre at the University of Pennsylvania.
The trial was based on the case of the 'Berlin patient', a patient with AIDS (acquired immunodeficiency syndrome) living in Germany who received a blood transfusion from an individual with natural resistance to HIV. The patient was 'functionally cured', as the virus could no longer be detected even after four years. Natural resistance to HIV, such as that of the blood donor in the case of the 'Berlin patient', occurs in a small percentage of people who lack the CCR5 gene. CCR5 is a cell surface receptor present on T cells, which HIV commandeers to infect the cells.
Researchers at the biotechnology company, Sangamo BioSciences in California, genetically manipulated T cells of HIV infected patients, using zinc finger technology. The CCR5 gene was permanently removed from the T cells, before reintroducing the cells back into the bloodstream of the patients. The cells were able to survive for at least three months, as well as increase in number.
'The procedure is safe so far and feasible, in that all patients can be treated i.e. no manufacturing failures, and thus the phase I protocol has met its objectives and can be deemed 'successful'', said Dr June.
Experts in the field point out that the results are far from a cure for HIV. 'If successful, this probably could have wide application, but going from six patients to an entire epidemic is a ways to go', said Dr Michael Horberg, vice chair of the HIV Medicine Association.
The results of the trial were presented at the 18th Conference on Retroviruses and Opportunistic Infections in Boston, which took place from 27 February to 2 March 2011.
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