New Vaccine Protects Against Multiple Strains of H7N9 Bird Flu Virus

As the H7N9 virus outbreak gets worse and spreads worldwide to other humans, research is under way to develop a comprehensive vaccine against a bunch of strains.

The World Health Organization (WHO) experts warn that the H7N9 virus outbreak is one of the most fatal seen in recent years. As of May 10, 2013, China National Health and Family Planning Commission reported a total of 131 confirmed cases of human infection with avian influenza A(H7N9) virus and the Taipei Centers for Disease Control (Taipei CDC) one case. Middle-aged and older men were especially affected. Thirty-five people have died.

In addition to the case reported by Taipei CDC (with a history of recent travel from Jiangsu), cases have been reported from Anhui, Fujian, Henan, Hunan, Jiangsu, Jiangxi, Shandong and Zhejiang, and the municipalities of Beijing and Shanghai.

"This is the first time human infection with the avian influenza A(H7N9) subtype has been detected," says WHO. "Previously, sporadic cases of human infection with other influenza A(H7) viruses have been reported which were associated with outbreaks of infection in poultry. The few A(H7) human infections that have occurred generally resulted in mild illness and conjunctivitis, with the exception of one death".

The avian influenza A(H7N9) virus isolated from humans contains a group of influenza virus genes from multiple origins, with some genetic changes. The amino acid substitutions associated with increased affinity to certain receptors (alpha 2-6), indicate that H7N9 may have greater ability to infect mammals, including humans, than other avian influenza viruses. Genetically, these viruses are expected to be sensitive to drugs called neuraminidase inhibitors oseltamivir and zanamivir, but resistant to the antiviral drugs amantadine and rimantadine, according to the WHO report.

Suresh Mittal, professor of comparative pathobiology in Purdue's College of Veterinary Medicine, has created a vaccine that includes genes from multiple strains of the H7N9 virus and offers protection that could continue to exist through different mutations.

"Avian influenza viruses are moving targets that rapidly evolve and evade vaccines that are specific to a predicted strain. We need a vaccine that protects against a spectrum of strains to prepare for a potential pandemic. Such a vaccine may not offer full protection from the strain that pops up, but even partial protection could save lives and buy time to create a more effective vaccine," says Mittal.

The strain behind the present outbreak does not seem to be easily transmitted from human to human, Mittal pointed out, something which happens in pandemic circumstances.  As the WHO report notes, "human infection appears to be related to exposure to live poultry or contaminated environments," due to genetic similarity between the human virus and the animal counterpart. Most human transmissions to date have occurred from exposure to animals, mostly chickens. "The number of human cases appears to have decreased after closure of live animal markets.Whether other potential reservoirs of this virus may exist, including in other domestic and wild bird species, and mammalian species, has not yet been determined."

"Fortunately, avian influenza in humans tends to replicate deep in the lungs where it can't easily get out through coughing. However, the more people this virus infects, the more chances it has to evolve. It is important to keep a close watch on this outbreak," says Mittal.

Mittal used a safe adenovirus vector to transport the flu virus genes into the body, and trigger a two-fold immune response including antibody and cell-based protection. As human cells are infected with the adenovirus vector, they churn out influenza proteins that stimulate production of antibodies and special T-cells designed to destroy the virus and any infected cells. Genes underlying protection against the avian influenza virus can be incorporated inside the adenovirus vector. The immune system can respond to the surface as well as the internal components of the virus.

"This method works beyond that of the current vaccine, in which the body responds to inactivated virus proteins injected into a muscle," Mittal said. "Getting the influenza virus genes inside the cells better mimics an infection and leads to a more powerful and multifaceted immune response, so we are better prepared to fend off a true infection."

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