Corporate Banner
Satellite Banner
Genotyping & Gene Expression
Scientific Community
Become a Member | Sign in
Home>News>This Article

HIV Genotypic Sequencing Test Comparable to Standard Phenotypic Test in Predicting Antiretroviral Response

Published: Wednesday, October 03, 2012
Last Updated: Wednesday, October 03, 2012
Bookmark and Share
Genotypic HIV tropism laboratory-developed testing service now available nationally for HIV-infected patients.

A laboratory-developed blood test that uses deep-sequencing technology performed comparably to the industry's standard phenotypic test in helping to predict potential clinical response to HIV-1 antiretroviral CCR5-antagonist therapy, according to a new study from researchers at Quest Diagnostics and Pfizer. The findings underscore the potential of advanced sequencing technologies to aid in the cost-effective management of patients infected with HIV using CCR5 antagonists.

The study, "A Genotypic Test for HIV-1 Tropism Combining Sanger Sequencing with Ultradeep Sequencing Predicts Virologic Response in Treatment-Experienced Patients," was published online September 27 in the peer-reviewed, open-access journal PLOS ONE:

"Phenotyping to identify HIV tropism has played a critical role for the past five years in disease management for thousands of HIV-infected patients in the United States," said study investigator Rick L. Pesano, M.D., Ph.D., medical director, infectious diseases, Quest Diagnostics. "By demonstrating that faster, more cost-effective viral-genomic sequencing performs comparably to phenotypic testing, our study suggests another option for determining HIV tropism, an essential step in determining if a CCR5 antagonist therapy is a potential treatment option."

The study compared the performance of a genotypic laboratory-developed test from Quest Diagnostics to a widely offered phenotypic laboratory test in the United States to determine HIV-1 tropism on patient samples. Tropism refers to the type of cellular co-receptor, CCR5 or CXCR4, through which HIV-1 infects human cells. Viruses that use CCR5 are called R5-tropic ("R5") and those that use CXCR4 are called X4-tropic ("X4").  CCR5 antagonists can reduce HIV-1 viral loads in patients with only R5 virus, but are not recommended in patients with X4 virus or a dual-mixed combination of R5/X4.

Tropism varies by patient, and X4 virus may emerge over time in patients initially infected with R5 virus. Phenotyping examines the ability of the patient's cloned virus to infect cells, while genotypic tests examine the genetic sequence of the patient's virus. Although phenotyping has been the standard tropism detection method in the United States, genotypic tropism tests are widely used and supported by medical guidelines in Europe.

The Quest Diagnostics laboratory-developed test used in the study employed triplicate population sequencing (TPS), which involves genotyping the third variable (V3) loop, a region of the virus that binds to the CCR5 or CXCR4 co-receptor, and bioinformatics, to infer tropism in patients harboring R5, X4 or dual-mixed virus. A highly sensitive test is required to ensure the detection of X4 virus and exclude patients with low levels of X4 virus from receiving CCR5 antagonist therapy. For this reason, if TPS only detected R5 virus, highly sensitive ultradeep sequencing (UDS), which is able to detect minority X4 HIV-1 variants, was performed as a "reflex" test.

Researchers found that the genotypic and phenotypic tests performed comparably at predicting response in patients undergoing therapy with maraviroc. At week eight, the positive predictive value was 66% for the phenotypic test and 65% for the genotypic test, and negative predictive values were 59% for phenotyping and 58% for genotyping.

Quest Diagnostics launched the Quest Diagnostics HIV-1 Tropism with Reflex to Ultradeep sequencing (UDS) laboratory-developed testing service, based on the genotypic-tropism testing technique used in the study, in June 2012. It is the first genotypic-tropism testing service available to physicians in the United States to demonstrate comparable performance to phenotyping in aiding the selection of patients for potential treatment with CCR5 antagonists. The company's laboratory in San Juan Capistrano, California, developed, validated and performs the testing service for clinicians nationally.

Quest Diagnostics can provide results from the testing service in approximately a week for samples with a TPS result of X4 and in as little as 10 days for samples reflexed to UDS, compared to reported turnaround times of approximately 14 days for the phenotyping test used in the study.

"It is gratifying that sequencing has advanced to a level of sophistication that now enables it to perform comparably to phenotyping," said study investigator Ron M. Kagan Ph.D., director of Bioinformatics, Infectious Diseases, for the Quest Diagnostics Nichols Institute, an advanced test research and development center. "Quest Diagnostics has a strong record of innovation in HIV testing, and we look forward to exploring further the potential of genetic sequencing, and UDS in particular, as tools for helping to manage HIV disease in other applications."

Study Strengths and Limitations

The study's strengths include its use of 327 de-identified samples from the MOTIVATE and A4001029 clinical trials, including clinical outcome data, that were part of the data submitted to the FDA for market approval of maraviroc. Although the study was retrospective, its inclusion of de-identified samples from patients from both studies helped to ensure that patients were included in the study who received maraviroc regardless of their viral tropism status, reducing the bias from using samples previously screened with the first commercial phenotyping laboratory test in the U.S.  Limitations include the use of specimens from only treatment-experienced patients, although prior studies demonstrate that UDS effectively detects tropism in treatment-naive patients, and the use of algorithms focused on HIV-1 subtype B, which, while found in the vast majority of U.S. HIV-1 infected patients, is less common outside the U.S.

The MOTIVATE and A4001029 protocols were multi-center, multi-investigator studies, approved by institutional review board or independent ethics committee at each study center. Written informed consent was obtained from all participants.

Further Information
Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,800+ scientific posters on ePosters
  • More than 4,000+ scientific videos on LabTube
  • 35 community eNewsletters

Sign In

Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Related Content

Federal Guidelines Recommend New HIV Testing Method
U.S. Department of Health and Human Services issues medical guidelines recommending genotypic testing to aid HIV therapy selection.
Thursday, March 28, 2013
Quest Diagnostics Launches First Molecular Test for Kidney Organ Transplant Rejection
The Renal Transplant Monitoring laboratory-developed test is designed to help physicians detect kidney failure weeks before conventional tests or clinical symptoms signify damage.
Monday, March 19, 2012
New York State Approves Quest Diagnostics' Fragile X Syndrome Test
XSense® is said to be the first laboratory test that may be suitable for population-based screening for Fragile X Syndrome.
Friday, July 30, 2010
Quest Diagnostics to Provide Diagnostic Testing Services for the Women of Ireland
Quest to provide screening services intended to improve medical outcomes for women who participate in Ireland's first nationwide cytology-screening program.
Monday, June 23, 2008
Quest Diagnostics Licenses Technology Underlying SensiTrop™ HIV Co-Receptor Tropism Test from Pathway Diagnostics
Quest Diagnostics licenses the heteroduplex tracking technology underlying Pathway's SensiTrop™ HIV co-receptor tropism test.
Tuesday, October 30, 2007
Quest Introduces ClariSure™ Test for Identifying Chromosome Abnormalities in Children
The molecular diagnostic test is designed to detect chromosome abnormalities associated with 85 developmental disorders affecting children.
Monday, September 03, 2007
Quest Diagnostics Launches Test to Predict Risk of Breast Cancer Recurrence in Women
Quest Diagnostics has introduced a test which can help physicians to predict the risk of disease recurrence in women with ER-positive, lymph node-negative breast cancer.
Tuesday, December 19, 2006
Scientific News
NIH Supports New Studies to Find Alzheimer’s Biomarkers in Down Syndrome
Initiative will track dementia onset, progress in Down syndrome volunteers.
New Gene Map Reveals Cancer’s Achilles’ Heel
Team of researchers switches off almost 18,000 genes
Genetic Basis of Fatal Flu Side Effect Discovered
A group of people with fatal H1N1 flu died after their viral infections triggered a deadly hyperinflammatory disorder in susceptible individuals with gene mutations linked to the overactive immune response, according to a recent study.
New Class of RNA Tumor Suppressors Identified
Two short, “housekeeping” RNA molecules block cancer growth by binding to an important cancer-associated protein called KRAS. More than a quarter of all human cancers are missing these RNAs.
Mathematical Model Forecasts the Path of Breast Cancer
Chances of survival depend on which organs breast cancer tumors colonize first.
Ancient Viral Molecules Essential for Human Development
Genetic material from ancient viral infections is critical to human development, according to researchers at the Stanford University School of Medicine.
Measuring microRNAs in Blood to Speed Cancer Detection
A simple, ultrasensitive microRNA sensor holds promise for the design of new diagnostic strategies and, potentially, for the prognosis and treatment of pancreatic and other cancers.
Personalized Drug Screening for Multiple Myeloma Patients
A personalized method for testing the effectiveness of drugs that treat multiple myeloma may predict quickly and more accurately the best treatments for individual patients with the bone marrow cancer.
Metabolic Profiles Distinguish Early Stage Ovarian Cancer with Unprecedented Accuracy
Studying blood serum compounds of different molecular weights has led scientists to a set of biomarkers that may enable development of a highly accurate screening test for early-stage ovarian cancer.
New Way to Force Stem Cells to Become Bone Cells
Potential therapies based on this discovery could help people heal bone injuries or set hardware, such as replacement knees and hips.
Skyscraper Banner

SELECTBIO Market Reports
Go to LabTube
Go to eposters
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,800+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
4,000+ scientific videos