With new strains of HIV appearing in patients in the U.S., following not far behind is the need for new tests that can not only detect the virus, but also quantify viral load to determine how well drugs to treat the disease may be working.

For example, of 3,000 blood samples from HIV patients from 11 U.S. states, more than 5% of those samples were non-traditional, non-subtype B samples, or "samples other than the traditional strain of the virus we used to find here in the U.S."

That data is from a Centers for Disease Control and Prevention poster presented in February at the Conference on Retroviruses and Opportunistic Infections, according to Chris Jowett, director of marketing for Abbott Molecular (Des Plaines, Illinois). And the company reported FDA clearance for a real-time assay to perform viral load testing on these various new HIV-1 subtypes at the American Association for Clinical Chemistry (AACC; Washington) annual meeting last month in San Diego.

The test was FDA-approved in May.

"These states — these were not New York and California; these were the middle-of-the country kind of states …," Jowett told Medical Device Daily , suggesting the geographical incursion of these infection subtypes that may be seen first on distant parts of the planet.

Jowett said that non-B subtypes of HIV have been on the rise in recent years, not only in the U.S. but also in Western Europe, where non-traditional subtypes comprise 25% to 40% of new HIV infections, hence complicating the issues of accurate identification, viral load assessment and the drugs to be used, in what dosages.

Abbott said that according to some studies, these infections, found mainly in immigrant populations from Africa and Asia, may now represent up to 10% of HIV-1 infections in certain areas of the U.S.

One of the major challenges of HIV viral load testing is having tests that can recognize various strains of the disease, which mutate and change over time. And Jowett said that the Abbott test was developed "with these constant changes in mind. The assay was truly designed to have a broader reach, so to speak — a wider net; it was designed with all of that current data from all around the world in mind, so that we could actually detect all known strains today, and we would be able to continue to detect those strains."

The test has been available outside the U.S. since June 2005, having both the CE mark and individual approval in other countries.

Abbott Molecular said that with the U.S. launch of its RealTime HIV-1 viral load test, the test is capable of "detecting and precisely measuring group M, N and O strains of HIV-1, as well as all known group M non-B subtypes."

Abbott said HIV-1 can be divided into groups M (major), O (outlier) and N (new). While the company said that the "vast majority of isolates cluster in the M group," the high mutation rate and rapid evolution of the virus has resulted in the emergency of different group M subtypes, designated A through K, and circulating recombinant forms.

Linqi Zhang, PhD, associate professor and staff investigator at the Aaron Diamond AIDS Research Center (New York), and his colleagues conducted a study focusing on the genetic characterization of HIV-1 strains circulating in immigrant populations in New York. These study results were published in the Journal of Acquired Immune Deficiency Syndrome in 2006.

"It is generally assumed that infections in the U.S. are exclusively with the B ([subtype] and that this situation is going to continue into the foreseeable future," the authors wrote, but the study concluded that this was not the case.

Jowett said Abbott Molecular's approach to developing its test was "very novel."

"We worked in concert with our key research group at Abbott Diagnostics, and they have an HIV Global Surveillance program, in existence for over 10 years, and, indeed, they stay in touch with key HIV researchers around the world so that they can obtain samples and understand and track as new strains are identified, or as the virus mutates and changes," Jowett told MDD.

The test has been developed for use on Abbott's automated molecular diagnostics m2000 system, based on real-time polymerase chain reaction (PCR) technology.

Abbott said the viral load test is capable of quantitating HIV-1 in plasma down to as few as 40 RNA copies per milliliter (mL) and up to as many as 10 million copies per mL. Abbott currently markets the m2000 system and a menu of tests in countries throughout the world as part of a strategic alliance with Celera (Rockville, Maryland).

Abbott said the test is intended for use in conjunction with clinical presentation and other laboratory markers as an indicator of disease prognosis and for use as an aid in assessing viral response to antiretrovial treatment. The assay is not intended for use as a donor-screening test for HIV-1 or as a diagnostic test to confirm the presence of HIV-1 infection.

Abbott's only competitor for a real-time assay for viral load testing in HIV-1 at this point is Roche Diagnostics (Indianapolis).

Roche at AACC noted that one-third of its molecular customers had already purchased or ordered the COBAS AmpliPrep/COBAS TaqMan HIV-1 assay in a matter of eight weeks following the test's FDA approval.

"This is the most successful launch of a new molecular test at Roche Diagnostics," said Susan Zienowicz, VP of Molecular Diagnostics at Roche Diagnostics, in a company statement.

Roche's test offers what it called "standard of care sensitivity," or 50 copies/mL and quantitation between 48 copies and to 10 million copies.