Veterinary Researcher Assists in Fight Versus Avian Flu

The spectre of a highly pathogenic strain of avian influenza mutating, jumping to humans, and causing a worldwide flu pandemic has public health agencies, medical researchers, and agricultural officials scrambling to prepare. An avian virologist in Penn State’s College of Agricultural Sciences is in the thick of the action.

(Inset) With Huaguang Lu’s rapid dot-ELISA test, swabs or tissue samples from potentially infected birds are placed on membrane strips. After antibodies are applied to the strips, colored dots indicate the presence of avian influenza virus.

“The same-day results can help to nip an avian flu outbreak in the bud, before it has a chance to become an epidemic,” says Lu. “Rapid detection is especially critical in outbreaks of subtypes H5 and H7, which can mutate to highly pathogenic strains for poultry, and in rare cases, such as the H5N1 virus that has infected millions of birds and killed more than 60 people in Southeast Asia, can infect humans.”

A patent is being sought for the test, called a dot-enzyme-linked immunosorbent assay, or dot-ELISA. The university hopes to license the technology for commercial use.

In simplified terms, to screen for avian influenza virus with the dot-ELISA, a swab or tissue sample from a bird is processed and applied to paper-mounted strips of nitrocellulose membrane. Avian flu–specific monoclonal antibodies produced in a Penn State research laboratory then are applied to the strips. If an antigen—a live or dead virus—is present, a reaction occurs and the antigen and antibody link up. After additional processing of the strips, the antigen-antibody complex turns color, giving a visible
indication that the virus is present in the sample.

Lu says the test offers several advantages over other diagnostic measures. “Although conventional virus isolation, which is considered the ‘gold standard,’ can detect lower levels of virus, it is time consuming and labor intensive,” he explains. “Other, molecular-based tests that detect avian flu RNA sequences are quick and accurate, but they require expensive laboratory equipment and a high level of user expertise and sophistication. The dot-ELISA test is easier to perform, portable to the field, and very inexpensive.”

In a study reported in a recent issue of the journal Avian Diseases, Lu compared his dot-ELISA to a similar, commercially available test that was originally developed for use with humans but also has been used for detecting avian influenza virus. He found that the two tests were comparable in their sensitivity and specificity for detecting avian flu. However, the commercial test costs $18 per sample to run, compared to about 50 cents per sample for the Penn State test. In addition, the commercial test can process only 10 to 20 samples per run, but up to 100 samples can be processed in one run of the Penn State dot-ELISA.

Huaguang Lu (right) trains Cambodian laboratory technicians in the use of his rapid dot-ELISA test for avian flu virus at the diagnostic lab he helped to establish in Phnom Penh.

Lu’s test already has proven its mettle in a real-world situation. During a 2001 Pennsylvania outbreak of low-pathogenic H7N2 avian flu, the test—then in an early stage of development— enabled a quick diagnosis, which helped state agriculture officials to contain the outbreak and limit losses to 140,000 birds and about $350,000 in direct costs. An outbreak of the same virus a few months later in Virginia took about seven days to diagnose with a different test, giving the virus more time to spread. As a result, poultry producers in that state lost almost 5 million birds at a cost of more than $100 million.

The human health implications of bird flu stem from the virus’ ability to “reassort” and mutate
over time. The recent human deaths caused by a highly pathogenic strain of subtype H5N1 in Southeast Asia are believed to have been the result of people coming into close contact with infected birds. While officials say that strain does not appear to spread from person to person, health organizations worry that a highly pathogenic strain could combine with a strain of human influenza that’s easily passed between people, potentially causing a flu pandemic.

As a result of his expertise, Lu has been in demand internationally to assist in preparing for and managing avian flu outbreaks. At the request of the Food and Agriculture Organization (FAO) of the United Nations, he has traveled to Laos and Cambodia several times since 2004 to help establish virology laboratories and train scientists in detection and diagnosis.

In addition, the FAO is working with Lu to establish a training program that would bring scientists from around the world to Penn State’s Animal Diagnostic Laboratory to learn avian influenza diagnostic and surveillance techniques.

“Virology surveillance is the most important method to monitor avian flu virus in domestic poultry so as to effectively prevent and control outbreaks,” says Lu. “Combined with proper biosecurity, this technology can help to reduce the risk of a localized outbreak becoming a dangerous pandemic.”