According to the CDC, the respiratory syncytial virus (RSV)—a bug responsible for infections in the lungs and respiratory tract—is the most common cause of bronchiolitis and pneumonia among infants and children under 1 year of age.
The CDC states that from 25% to 40% of those infected have signs or symptoms of bronchiolitis or pneumonia during the initial RSV infection, with up to 2% requiring hospitalization.
Diagnosis of RSV infection is made primarily through antigen or genetic detection assays. San Diego, Calif-based Nanogen Inc produces reagents that can be used to develop genetic assays.
- NanoChip 400 System
“We currently offer multiplexed ASR products for developing assays to detect genetic sequences associated with human parainfluenza virus 1, 2, and 3; influenza virus A and B; and respiratory syncytial virus A and B,” says Suzanne Clancy, PhD, senior manager of corporate communications for Nanogen. The company also offers the NanoChip 400 System, a micro array multiplexing instrument. Clancy says one of the features that distinguishes the system is the NanoChip 400 Cartridge, which is reusable. There are 400 sites that can be filled in the cartridge; if the lab runs only a few samples of the tests and doesn’t use all of the sites, they can store the cartridge and integrate later with additional samples.
The system is also highly automated. Except for amplification of the sample, all other processes are completed inside the machine.
“That is very beneficial in terms of laboratory workflow, because they can walk away from the machine once they’ve programmed it,” says Clancy. “It also eliminates opportunity for handler error and contamination.”
On the horizon for Nanogen is completion of phase 2 of the development of a unique multianalyte point-of-care diagnostic assay. The work was funded through a grant from the CDC, which was awarded as part of the government’s efforts to strengthen its readiness for a possible flu outbreak.
“We plan to finish phase 2 and submit the results to the CDC this summer. That will be a different kind of test; it is an immunoassay designed to be very adaptable,” says Clancy.
The resulting product will be marketed by HX Diagnostics, Menlo Park, Calif, Nanogen’s partner on this project. “It is an antibody-based test, so you can vary the panel of antibodies depending on which strains are dominant in any given season. It will also include avian flu, in preparation for a potential pandemic.”
The test will provide results in about 15 minutes, and because it is intended for use by people with minimum training, it will be portable and easy to administer. After phase 2 results are submitted, the CDC will review the data and determine a timeline to move forward with development.
- Luminex 200-004 System
Through collaborations with partners EraGen Biosciences and Qiagen (Genaco), the Austin, Texas-based Luminex Corp produces multiple respiratory virus panel (RVP) assays for laboratory use.
From EraGen Biosciences is the MultiCode-PLx Respiratory Virus Panel, which includes 17 viral targets. Qiagen’s ResPlex II Panel features 12 viral targets, and Luminex Molecular Diagnostics (LMD) has 20 (19 in the United States).
The ID-Tag panel available from LMD (formerly Tm Bioscience) covers more than 95% of circulating viral pathogens; it is currently in submission with the FDA, pending 510(k) approval.
“All three of these market-leading organizations have identified a need for a more comprehensive approach toward generating better patient diagnoses,” says Darin Leigh, senior director of diagnostics sales and marketing for Luminex. “These panels have been designed with the intent of meeting a clear need in our clinical and public health laboratories that legacy technologies were unable to meet—namely, timely and reliable results.”
This approach is particularly effective for patients who simultaneously carry more than one virus. Multiplexing means that identifying this type of co-infection is not only easier, but also faster. In addition, it shortens the time required to identify the specific cause of infection, which speeds determination of the appropriate course of treatment for the patient. Not only does this provide better overall care, but it helps eliminate the use of incorrect therapies, such as the prescription of unnecessary antibiotics.
“If you are doing real-time PCR, each would cover typically, at most, three targets,” Leigh says. “So, to get the same coverage as a single RVP assay, you would need to do between six and 20 PCRs, which could cost many hundreds of dollars per patient for the same answers.”
The RSPs manufactured by Luminex also contribute to speeding the microbiology lab’s slow evolution toward embracing automation—a change these facilities are often hesitant to make.
“An additional consideration is the strain performing older testing methods like DFA and culture place on labs today,” Leigh says. “Perform- ing these tests requires a highly trained technician, and with fewer individuals entering the field and more nearing retirement, labs are looking to solutions like multiplexing to reduce the workload on their staff.”
At the other end of the spectrum is the need to test for very particular diseases. Rather than multiplexing the patient sample, The Binding Site’s specialized IVD assays are tailored to identify very specific antibodies. Based in Birmingham, UK, and San Diego, the company manufactures and distributes tests that fall into two distinct categories. The autoimmune vasculitis panel includes three different assays that are collectively grouped as antineutrophil cytoplasmic antibody.
The assays—anti-PR3, anti-MPO, and anti- GBM—help to differentiate Wegener’s granulomatosis, Churg-Strauss Syndrome (CSS), and Goodpasture’s Syndrome. While rare, these diseases are similar in nature in that they involve circulating antibodies in the blood that cause inflammation of the small blood vessels responsible for bringing blood to organs, including the lungs.
“What complicates testing for these diseases is they are very similar in presentation,” says Gary Tremain, the marketing manager of Autoimmune and Infectious Disease for The Binding Site. “There is not one marker that is necessarily associated with one disease, so you are better off to screen for all three results by running these as a panel. Some markers have a higher percentage of positivity in certain diseases than others, but there is so much overlap in the antibody of the disease, as well as in the clinical symptoms, [that] it is best to look at the bigger picture, as opposed to trying to zero in on one marker or one disease.”
Infectious disease is also an area of focus for The Binding Site. Offered through the Trinity Biotech brand, the Trinity Infectious Disease Assays are run individually to identify either Legionnaires’ disease or mycoplasma pneumonia, two rare forms of pneumonia. Different environmental exposures and transmission modes for the two diseases assist clinicians in identifying exactly the illness for which they want to screen.
The ELISA microplate products from The Binding Site can be run on any microplate system or as part of the menu on the company’s DSX 4 Plate ELISA processor. Allowing for continuous sample and test loading, the DSX is an open system, which allows facilities to program it to accommodate an unlimited number of assays.
“All of our reagent kits are in basic microplate, 96-test format and have dating that allows them to be stored for about a year,” says Tremain, noting that the exact shelf life varies slightly with each test. “Our testing systems are very cost-effective, which has allowed smaller hospitals and laboratories previously forced to send tests out to bring some of that business back in-house.”
Treating Airborne Threats
Recent events have put tuberculosis in the spotlight, but the disease does not require prime-time news reports to have an impact. In 2006, the World Health Organization (WHO) reported that nearly 2 million deaths are caused by TB around the globe each year. The HIV epidemic in the late 1980s and early 1990s helped fuel an increase in TB cases, as did outbreaks in third-world countries, correctional facilities, and homeless shelters.
Fortunately, the trend is reversing. TB cases reported to CDC in 2005 indicated a 47% decrease from 1992, when cases in the United States were peaking. Part of the credit for the decrease can be attributed to improved TB-control programs.
Cellestis Inc, Valencia, Calif, is working to improve the way those programs operate. The company’s QuantiFERON-TB Gold uses whole blood, eliminating the need for cell isolation and fractionation, making the test inexpensive and fast. This ELISA-based assay marks the first viable alternative to the current go-to: the Mantoux test.
“That has been the only test in use since the 1930s, and the method itself was actually discovered in the 1890s,” says Mark Boyle, senior vice president of sales and marketing for Cellestis. “Our goal is to introduce QuantiFERON into TB-control programs across the world.”
While many of the test’s qualities make it an appealing replacement for the skin test, one of the most notable is its turnaround time. The Mantoux test requires an inspection of the injection site after 48 to 72 hours. The QuantiFERON produces a result in 24 hours.
When there is an active infection, TB produces a range of symptoms such as a persistent cough, fever, and exhaustion. However, there are 2 billion people—about one third of the world’s total population—who are infected with TB bacilli and unaware they are carrying the microbes. WHO estimates that “one in 10 people infected with TB bacilli will become sick with active TB in their lifetime.” QuantiFERON®-TB is capable of detecting the virus even when the disease is dormant.
The next generation of the QuantiFERON product—QuantiFERON-TB Gold In-Tube—is making its way through the final stages of the FDA approval process. The product’s most notable improvement is a simplified blood stimulation step that allows the test to be performed in any location. It is available in Europe, Australia, Canada, Africa, the Middle East, and Asia.
“The tubes contain TB antigens ESAT-6 and CFP-10. After you draw the blood into the tube and mix vigorously, you can incubate it onsite,” says Boyle. This is particularly important because the disease is one of poverty, most often affecting the poor and malnourished. “The test can be done in the field, which has been a limitation up to now, because previously you had to draw the blood and then send it to the lab,” Boyle adds. “Now we can do this procedure anywhere.”
Dana Hinesly is a contributing writer for CLP.