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Researchers knock down to stop HIV in its tracks

Last month, San Francisco officials granted a Mighty marrow instead. So June and his colleagues are also city proclamation to Gero Hütter for his 2007 The approach, however, offers only a developing zinc finger nucleases that target discovery that a transplant could, treatment—not a cure. So other researchers CXCR4. However, some scientists have it seems, cure a person of HIV. The German are focusing instead on altering bone marrow increased concerns about this approach’s safety, hematologist’s findings raised hopes for a new stem cells to provide an everlasting resistance because the receptor may have an important therapeutic treatment, but the shortage of to HIV. Last year, CIRM funded a team led role in healthy cells to attract white cells tissue-matched donors has prompted some by John Zaia at the City of Hope in Duarte, to sites of or injury. “The problem researchers to apply the lessons learned to new California, in collaboration with Sangamo, to is that [CXCR4] may be more important to the techniques. start pursuing preclinical research applying the cell for its normal functions than CCR5,” says The HIV-resistant bone marrow donor in same tactic in bone marrow. Ramesh Akkina, who studies HIV gene therapy Hütter’s study carried a rare in the Jerome Zack of the University of California- at Colorado State University in Fort Collins. gene encoding C-C receptor type 5, Los Angeles AIDS Institute notes that bone What’s more, even strains that normally rely on or CCR5, a surface essential for helping marrow therapy has the advantage CCR5 can evolve to use CXCR4 instead. HIV attach and infect healthy cells (N. Engl. of potentially lasting a lifetime, unlike gene Instead of focusing solely on these receptors, J. Med. 360, 692–698, 2009). The absence of therapy aimed at T cells, which must be Zaia also recently completed a phase 1 trial of this molecular portal makes nearly repeated over and over again after the mature an HIV gene therapy technique involving three impossible. However, individuals with the immune cells die out. What’s more, says Zack, —two that interfere with CCR5 mutation are rare, and their bone who is not involved in these studies, bone and one that blocks CCR5. Reporting last marrow is not always a good match for all marrow transplants should help achieve higher month, Zaia’s team showed that patients recipients. To emulate the protection of this cell counts. with AIDS-related expressed the mutation, several research teams are devising “We do not lack ways to attack HIV,” says modified genes in their blood and showed no ways to downregulate the expression of CCR5 David Strayer, a virologist at Thomas Jefferson signs of short-term toxicity (Sci. Trans. Med. so that HIV does not recognize and invade University in Philadelphia. “We lack ways to 2, 36ra43). sensitive cells in susceptible individuals. deliver genes adequately.” Gene therapy against HIV “is now within One line of attack involves RNA interference. A potential obstacle to CCR5-based gene the of feasibility,” says Zaia. “Now we Last month, for example, Irvin Chen and his therapy is that the protein is not the only can design larger studies and figure out ways colleagues at the University of California–Los receptor recognized by the —some viral to improve it.” Angeles School of Medicine reported that strains bind the CXCR4 Janelle Weaver, San Francisco short hairpin RNA could successfully knock down CCR5 expression in human induced pluripotent stem cells (Hum. Gene Ther. doi:10.1089/hum.2010.050, 2010). Chen, Canadian beacon Dilantin (anticonvulsant) backed by a $20 million grant from the California Institute for Regenerative Medicine Each year, around a million Americans purchase Synthroid (thyroid problems)

© 2010 Nature America, Inc. All rights reserved. All rights Inc. America, Nature © 2010 (CIRM), has now partnered with the Tuscon, cheap medicines from online Canadian pharmacies Arizona–based biotech startup Calimmune to to help make ends meet. According to the Canadian International Pharmacy Association (CIPA), which develop therapies based on the approach. Advair (treats asthma) Another strategy takes advantage of a newly surveyed its 14 member pharmacies for the 15 best developed technology based on zinc finger sellers to US consumers in 2009, most people nucleases. With this approach, pioneered by who turn to Internet drugstores north of the Plavix (anticoagulant) Sangamo Biosciences of Richmond, California, border are buying everyday prescriptions to treat common chronic conditions, such as engineered make precise cuts in the Nexium (antacid) to disrupt gene function. In 2008, Carl heart disease, diabetes and arthritis. June’s team at the University of Pennsylvania “This is the mainstay of our business,” says Celebrex in Philadelphia used zinc finger nucleases to Tim Smith, CIPA’s general manager. “The bulk of our patients are people who are living on (anti-inflammatory, disrupt CCR5 expression in human T cells, arthritis) which they injected into HIV-infected mice. fixed income; they’re concerned about the high The gene therapy lowered viral loads and cost of drugs, and they have concerns about increased T cell counts in the mice (Nat. their ongoing medical conditions.” Flomax Biotech. 26, 808–816, 2008). Here, in no particular order, are the top (muscle relaxant) Sangamo, in collaboration with June, has selling drugs: since started extracting mature T cells from Zetia, Lipitor, Crestor (cholesterol lowering) HIV-positive individuals, knocking down Asacol (anti-inflammatory, expression of the CCR5 gene with zinc fingers, Actos, Januvia, Prandin (control blood sugar) irritable bowel disease) and then re-infusing the cells back into the blood. Preliminary results from their first Premarin (female hormone replacement therapy) patient indicate that the modified cells are tolerated and persist at stable levels.

nature medicine volume 16 | number 7 | july 2010 731