PARIS, March 18 (AFP) - A genetic study of a strain of AIDS virus that triggered a health alert in New York describes the pathogen as unique, resistant to almost every class of HIV drug and apparently able to wreck the immune system with unprecedented speed.
US researchers unravelled the DNA identity of the mutated virus after it was found in a New York man who is believed to have progressed to full-blown AIDS just months after becoming infected, rather than years, as is usually the case.
The unidentified man, aged in his late 40s, had had unprotected anal sex with multiple male partners and regularly took methamphetamine, or "ice" -- an outlawed stimulant that heightens sexual appetite and lowers inhibitions.
In a study published on Saturday in The Lancet, a team led by Martin Markowitz of the Aaron Diamond AIDS Research Center in New York, identify the 3-DCR virus as a mutated strain of the B subtype of HIV-1, the most widespread of the two main branches of AIDS virus.
Its genetic map shows it to have, unusually, a double option for penetrating human immune cells, able to latch onto its target via two docking points, called receptors, on the cell surface.
In addition, the virus' mutated shape means it is impervious to the three of the four classes of anti-retroviral drugs designed to stop the virus from replicating in the immune cell.
The other class of drug, a small and very expensive category of treatments called fusion inhibitors, which are designed to prevent the virus from docking to the cell, may make headway against it, according to the DNA analysis.
The patient went to his doctor on December 16, complaining of a sore throat and fatigue, the study says.
An HIV test was conducted, and it was positive. However, he had had five previous tests, between September 2000 and May 2003, and all were negative.
At a follow-up examination on January 13, he bore the hallmarks of full-blown AIDS -- severe weight loss, with the shedding of four kilos (8.8 pounds) in just three weeks, a sense of sickness, anorexia, sore throat and difficulty in swallowing.
Comparing his test results and record of sexual activities, the researchers believe the patient progressed from infection to AIDS in a timeframe of four to 20 months, a speed that has no parallel in the known history of the disease.
The virus was first reported at an AIDS conference in New York in February.
Its discovery was considered so important that the team alerted the city authorities, who began to trace the man's sex partners and held a press conference to urge the public to practice safe sex.
The emergence of a new, resistant strain of virus is a nightmare for AIDS campaigners, who worry it could negate the precious antiretroviral drugs that have turned HIV into a manageable if still incurable disease.
But the discovery also ignited controversy.
Other researchers blasted the alert as premature and some gay activists branded it hype.
Drug-resistant strains have sporadically popped up in the long history of AIDS, as have strains that swiftly cause transition to full-blown AIDS.
In addition, some people are highly susceptible to HIV while others can live almost problem-free for a decade or more before their immune system is compromised.
Markowitz's team stress it remains unclear how widespread 3-DCR virus is, how easily it can be transmitted, and whether some people may be genetically more vulnerable to it others.
But they also say the new virus is exceptional.
Normally, drug-resistant strains are less virulent -- they gain their resistance at the cost of their ability to replicate.
In this case, though, the agent -- but in laboratory conditions -- replicated as easily as non-resistant types.
"This case serves a reminder that HIV remains a frighteningly versatile foe, one that can mutate to escape immune attack or to acquire drug resistance with surprising speed," The Lancet said in an editorial.
"(...) Despite all the progress that has been made in developing new drugs, prevention remains the most effective strategy to combat HIV, especially efforts that target high-risk groups."
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