 |
|
|
|
|
By John S. James
AIDS Treatment News
Researchers have learned important details of how the
immune system first controls HIV, and how the virus evades
it, through a study in monkeys published two weeks ago in
NATURE.(1,2)
For some time it has been widely believed that a kind of T cell called cytotoxic T lymphocyte (CTL) is particularly important in controlling HIV. The new study investigated how this works by infecting monkeys with a precisely known strain of SIV, a virus which causes an infection in monkeys comparable in many ways to AIDS in humans. Because the infecting virus was well known, changes in the virus during infection could be observed. The researchers found that most of the SIV-specific CTLs, which the monkeys produced in response to the infection, recognized peptides (short sequences of amino acids) from either the Tat or Gag "regulatory" proteins of the virus. And after 8 weeks, all of the original virus was gone-- showing the effect of the immune response. But the original virus had been replaced by SIV with small changes, usually in Tat. So apparently the body is able to control the virus through Tat-specific CTLs--but the virus can mutate and change its Tat, getting around this immune control.
And the immune escape found in this study may be less of an issue with a preventive vaccine, since there is much less viral variation and less chance to produce new mutations. And in any case, the new vaccine ideas suggested by this study are readily testable. Other research groups have already been working on a Tat- based vaccine. Anthony Fauci, M.D., director of the U.S. National Institute of Allergy and Infectious Diseases (NIAID), which funded the research, said: "These animal studies open the window on immune events in early HIV infection and provide a rationale for exploring a new approach to designing HIV vaccines. The results suggest that using vaccines that stimulate immune responses against virus proteins produced within a few hours after infection, such as Tat, may help to control HIV." A separate in-depth explanation of the results and their significance was published in the same issue of the journal.(2) References 1. Allen TM, O'Connor DH, Jing P and others. Tat-specific cytotoxic T lymphocytes select for SIV escape variants during resolution of primary viraemia. NATURE. September 21, 2000; volume 407, pages 386-390. 2. Walker BD and Goulder PJR. Escape from the immune system. NATURE. September 21, 2000; volume 407, pages 313- 314. AIDS Treatment News Published twice monthly Subscription and Editorial Office: P.O. Box 411256 San Francisco, CA 94141 800/TREAT-1-2 toll-free U.S. and Canada 415/255-0588 regular office number Fax: 415/255-4659 E-mail: aidsnews@aidsnews.org
Editor and Publisher: John S. James Associate Editor: Tadd T. Tobias Reader Services: Tom Fontaine and Denny Smith Operations Manager: Danalan Richard Copeland Statement of Purpose: AIDS Treatment News reports on experimental and standard treatments, especially those available now. We interview physicians, scientists, other health professionals, and persons with AIDS or HIV; we also collect information from meetings and conferences, medical journals, and computer databases. Long-term survivors have usually tried many different treatments, and found combinations which work for them. AIDS Treatment News does not recommend particular therapies, but seeks to increase the options available. Subscription Information: Call 800/TREAT-1-2 Businesses, Institutions, Professionals: $270/year. Includes early delivery of an extra copy by email. Nonprofit organizations: $135/year. Includes early delivery of an extra copy by email. Individuals: $120/year, or $70 for six months. Special discount for persons with financial difficulties: $54/year, or $30 for six months. If you cannot afford a subscription, please write or call. Outside North, Central, or South America, add air mail postage: $20/year, $10 for six months. Back issues available. Fax subscriptions, bulk rates, and multiple subscriptions are available; contact our office for details. Please send U.S. funds: personal check or bank draft, international postal money order, or travelers checks. ISSN # 1052-4207 Copyright 2000 by John S. James. |
© 1997-2000 BEI