VANCOUVER, B.C. _ The Centers for Disease Control andPrevention (CDC) has found several rare HIV strains in people whohave lived in a borough of New York for years. The finding followsby less than a month the government disclosure that a West Africanwoman infected with the rare group O strain of the AIDS virus hasturned up in Los Angeles.
The new report, delivered at the XI International Conference OnAIDS, compounds concerns that the genetic diversity of HIV in theU.S. may be increasing, which would have key implications for themanufacturers of nearly all commercially available HIV tests,including those used for diagnosis and for screening the nation'sblood supply.
The presence of these strains also presents a daunting new challengefor investigators trying to develop an HIV vaccine. It may force themto shift their efforts from trying to find a vaccine that protects againstthe group-M, clad-B viruses found in North America to one that willprotect against many strains previously thought to exist only inunderdeveloped nations.
Kathleen Irwin, a medical epidemiologist at the CDC, in Atlanta, andthe study's lead investigator, said these rare infections are the "first tobe reported for a well-characterized population of U.S. residents." Inaddition, she said, this serologic diversity is "far greater" than theresearchers had expected to find within the borders of the U.S.
Scientists have known for years that the global HIV pandemic is inreality made up of at least five distinct major epidemics caused bydifferent variants of HIV. One of the nation's leading experts on HIVdiversity _ Francine McCutcheon, director of global molecularepidemiology at the Henry M. Jackson Foundation and Walter ReedArmy Institute of Research, in Rockville, Md. _ had previouslypostulated that each of these variants remained confined to "adifferent geographic locale."
Her research has indicated that the B genotype was confined to theU.S. and Europe, the A and D genotypes to East Africa, the Cgenotype to Southern Africa and the E type to Southeast Asia.Contrary to these assumptions, the new study has identified serotypesA, C, Thailand B and a novel strain that could not be typed in eightpatients at a single hospital, Bronx Lebanon Hospital, in New York.
"This community has one of the highest prevalences of HIV infectionand AIDS in North America," she noted, in part because intravenousdrug abuse and high-risk heterosexual sex are more common in theBronx than virtually any other community on the continent.
None of the patients were known to be infected when they visited thehospital's emergency room and outpatient clinics. They were foundto be infected in a confidential HIV serosurvey of 828 BronxLebanon patients.
Those who agreed to take part also agreed to participate in pre- andpost-test interviews.
The researchers found that 5.2 percent of the patients tested positivefor HIV, Irwin said. Specimens from those 48 patients _ five ofwhom had borderline tests _ were sent to the CDC for additionaltesting, using methods that are highly sensitive for unusual subtypesof HIV-1 and HIV-2.
Irwin said the tests confirmed that 43 of the patients were HIVpositive.
Thirty-five of the patients were found to have HIV-1 infectionsconsistent with the North American subtype, B. The atypical strainswere genotyped using DNA from peripheral mononuclear cells. ThisDNA was then amplified so that the sequences could be analyzed andcharted in a phylogenetic family tree. The CDC tests confirmed thateight patients _ 20 percent of those found to be infected _ harboredHIV-1 genotypes never before seen in people residing in the U.S.,Irwin said.
When the investigators examined the answers these patients hadgiven to the pre- and post-test interviews they found:
* Four of the eight patients infected with unusual HIV strains wereborn outside the continental U.S., but two of them had lived in theBronx for at least 10 years.
* All but one of the six people in that group who provided residenceinformation had lived in the Bronx for at least six years.
* Three of six patients who provided travel histories had spent morethan 30 days outside of the U.S. since 1982.
Six of the eight patients, however, reported having a sex partner since1982 who had previously spent time in Africa, Latin America or theCaribbean. Seven of them _ patients two through eight _ mighthave contracted their infections from sex partners who had traveledabroad or while traveling abroad themselves. One of the seven alsomight have been exposed to HIV through intravenous drug abuse.
"Patient number one was unique," Irwin said.
This was a woman who was born in the U.S. and who had lived in theBronx for eight years. She admitted to injecting drugs and to havingone or more sexual partners who she believed had injected drugs.Among these were at least one partner she believed was HIV positiveand one _ possibly the same person _ who had had a bloodtransfusion.
"If this patient's self-reported behaviors are accurate," Irwin asserted,"she would have acquired her serotype A infection through sex orsharing injection equipment with local residents," indicating that shehad picked up an unusual HIV strain that was circulating in thecommunity and rather than one that was imported from an endemicregion outside the country.
Jerome Ernst, a doctor at the hospital who had called for the study,said the study suggested that public health efforts to identify unusualHIV strains were misdirected.
Rather than looking for these strains abroad, he said, "they shouldlook for them here, to find out whether we have strains in the U.S.that aren't being picked up by conventional testing." n
-- Steve Sternberg Special To BioWorld Today
(c) 1997 American Health Consultants. All rights reserved.