Acambis launches human trial of 'universal' flu vaccine

Jul 30, 2007 (CIDRAP News) – Acambis, a British biotechnology company, recently announced the launch of a phase 1 clinical trial of an influenza vaccine designed to provide a stable shield against seasonal and pandemic flu strains and eliminate the need to overhaul the flu vaccine each year.

Known as ACAM-FLU-A, the vaccine is designed to target all influenza A virus strains, Acambis said in a Jul 17 press release. If successful, the product will mark a major step toward a universal flu vaccine—one that would protect against all strains of both influenza A and B. The majority of laboratory-confirmed flu cases each year in the United States are type A.

The randomized, double-blind, placebo-controlled, multicenter trial will be conducted in the United States. Investigators will assess the vaccine's safety, tolerability, and ability to generate an immune response in up to 80 healthy volunteers between ages 18 and 40, the company said.

The trial will also assess the effectiveness of two adjuvants (immune-boosting chemicals): aluminum hydroxide, widely used in licensed vaccines, and QS-21 Stimulon, an investigational adjuvant licensed from Antigenics, Inc., according to Acambis.

Michael Watson, Acambis' executive vice-president for research and development, said in the press release that an effective universal vaccine will not require reengineering each time the virus mutates. Such a vaccine could be manufactured continuously, and people could be immunized any time of year.

"It could be stockpiled in advance of a pandemic or potentially used routinely to ensure population protection against future pandemics," Watson said, adding that Acambis hopes to see results of the study by the end of the year.

Frequent minor changes in flu viruses involve two surface proteins, hemagglutinin and neuraminidase, represented by the H and N in virus names, such as H3N2. The two proteins allow flu viruses to enter host cells and then exit them after replicating. Because the H and N components are highly mutable, vaccine makers must adjust the flu shot components every year to match circulating strains.

However, Acambis's vaccine involves a more stable viral protein called M2, the ion channel protein. The company said the key component in its flu vaccine is M2e, the extracellular domain of M2, which is specific to influenza A. The hope is that M2e will produce an immune response against all influenza A stains, according to Acambis.

ACAM-FLU-A is a recombinant vaccine that uses a hepatitis B virus core protein to deliver M2e, the company said.

Acambis also said it is searching for a similarly conserved region on influenza B virus strains so that it can offer a vaccine that protects against all human seasonal flu strains.

Universal influenza vaccines are under investigation by several other groups, including the Wistar Institute in Philadelphia and Dynavax Technologies in the San Francisco area, among others.

Walter Gerhard, professor of immunology at the Wistar Institute, and colleagues wrote in an April 2006 Emerging Infectious Diseases (EID) article that the hope is that universal vaccines can replace current vaccines. But they wrote that even if universal vaccines only reduce, without preventing, clinical disease, they will still be an important adjunct to conventional vaccines, particularly for high-risk groups.

Gerhard and colleagues wrote that, in the face of a major new flu variant, maternal antibodies generated by universal vaccines could give newborns some protection. Also, in elderly people a universal vaccine could induce memory B cells, which tend to be maintained into old age and can be recalled by booster vaccination, to generate protective antibodies. The article said the effectiveness of current vaccines depends heavily on "naïve" B cells, which frequently decrease as people age.

"When all factors are taken into account, protection against influenza virus infection likely can be improved by a universal vaccine," the authors wrote.

See also:

Aug 25, 2005, CIDRAP News story "Acambis hopes to build a flu vaccine that lasts"

Apr 2006 EID article on prospects for a universal influenza vaccine

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