Real-Time Immuno-PCR has the ability to detect HIV infection earlier than all current methods

Jun 15 2004

Researchers at the Institute of Human Virology have developed an ultra-sensitive testing technique that has shown the ability to detect HIV infection earlier than all current methods. This new diagnostic approach combines two existing models and is 25 times more sensitive than the best technology currently available.

“This new ultra-sensitive testing method, known as Real-Time Immuno-PCR, will allow us to detect HIV earlier and at much lower levels,” says Dr. Niel Constantine, a researcher at the IHV who has pioneered diagnostic research for more than two decades.

He currently heads the Laboratory of Viral Diagnostics at the IHV, a center devoted to viral research, most specifically HIV/AIDS and headed by world-renowned Dr. Robert C. Gallo, co-discoverer of the virus that causes AIDS.

Constantine also is Director of the Clinical Immunology Laboratory at the University of Maryland Medical Center and is a professor in the Department of Pathology at the University of Maryland School of Medicine.

Findings will be published in the July issue of the American Journal of Clinical Pathology in an article co-authored by Janet M. Barletta, Ph.D., and Daniel C. Edelman, MS. The Institute of Human Virology (IHV) is a center of the University of Maryland Biotechnology Institute and is affiliated with the University of Maryland School of Medicine and University of Maryland Medical Center.

Utilizing Existing Technology in New Ways

Real-Time Immuno-PCR, a novel method that detects ultra-low levels of proteins, has been applied for the detection of the AIDS virus. Specifically, it detects an inner protein of the virus known as p24, rather than detecting antibodies or viral nucleic acids. “Each virus particle contains about 3,000 molecules of p24 as compared with only two copies of nucleic acid. So there’s a greater amount of target to detect,” says Constantine of the new testing method, which combines the traditional ELISA approach with another method known as PCR (polymerase chain reaction). “It’s an advance over current methods in that we can detect down to the equivalent of two copies of RNA as compared with current methods which have been validated to only 50 copies,” says Dr. Barletta.

The new approach has important implications for both HIV identification and treatment. Traditional testing methods detect HIV about 12 days after infection. Earlier detection could result not only in earlier diagnosis, but in an improved protection of the blood supply and more effective treatment options for patients. “Monitoring HIV infection during anti-retroviral treatment is the standard of care, and better monitoring of virus in the blood can more effectively address the growing trend of drug resistance,” says Dr. Constantine.

In the U.S., HIV patients are living longer and better lives since the introduction of effective antiretroviral therapy. It is estimated, however, that as many as half of all HIV-infected patients in care has treatment complicated by antiretroviral drug resistance, drastically reducing their odds of long-term success.

Simpler is sometimes essential

Constantine’s laboratory also is making strides in developing and maximizing HIV monitoring efforts that can be effectively utilized around the world, even in the most resource-constrained developing nations.

In a $200,000 project funded by the Doris Duke Foundation, Constantines’s team is utilizing a portable, battery-operated HIV monitoring system that weighs less than 5 pounds and can be powered by an automotive battery to address the critical issues of unstable electricity and high temperatures that often occur in most of the world’s laboratories. “The unit also contains a light that allows for testing at night when temperatures are cooler,” says Constantine.

Some 90 percent of all HIV infections occur in the developing world. However, few can afford therapeutics needed for the masses and, in those areas where even emergency aid is available, therapeutics often come in the absence of effective treatment monitoring.

“Monitoring the response of HIV-infected persons to drugs is essential for managing care and increasing life expectancy,” says Constantine. “Drug regimens must often be changed in response to resurgence of virus in blood, and thus, viral levels need to be monitored at regular intervals. Currently, the tests used to monitor active replication of the virus (viral load tests) are expensive and rigorous to perform; thus, these tests cannot be easily used in resource-limited countries and in laboratories that lack sufficient technical capability or infrastructure.”

The portable battery-operated tests are simple to perform with fast results. “The proposed method incorporates a magnetic bead support and an antigen-antibody reaction that will be visualized by color production after the initial signal has been multiplied many times by using a special reagent. This “boosted” method allows a simple test to compete with more sophisticated technologies for detecting low levels of virus.

“The test will be much less expensive than current viral load tests,” says Constantine, “much simpler to perform, portable, and will address a current and important void in the ability of developing country laboratories to assist health care professionals in determining if drug therapy for HIV infection is effective.”