Friday, December 14, 2007

The New Influenza Vaccine

A new vaccine that protects monkeys against the avian influenza virus strain has been developed by researchers at the National Institute of Health and the University of Maryland. It has worked on African monkeys and is now ready for clinical trial on humans. In the past decade or so, transmission rate of this highly pathogenic avian influenza virus from birds to humans has rapidly increased resulting in 278 human infections and 168 deaths. Fear of a possible pandemic outbreak emphasizes the need for an effective vaccine. Development of the vaccine has been hindered by factors like poor immunogenicity, biosafety concerns, and risk of genetic exchange with circulating influenza virus strains. The research involved the creation of a live vaccine which included the avian Newcastle Disease Virus which contains a common gene found in the avian influenza virus. Given both intranasally and through the respiratory tract in two doses with a 28-day interval, the vaccine response showed low amounts of virus shedding indicating protection. After the second dose, high levels of neutralizing antibodies were present in the immunized systems. A substantial response to either dosage was noted in the respiratory tract indicating a likely reduction in transmission in the event of an outbreak.

Influenza is a serious infection, sometimes deadly, where the enveloped Influenzavirus binds itself to the surface of the cell. Typically, influenza is transmitted from infected mammals through air by coughs or sneezes, creating aerosols containing the virus, and from infected birds through their droppings. It can also be transmitted by saliva, nasal secretions, feces and blood. Infections occur through contact with these bodily fluids or with contaminated surfaces. Flu viruses can remain infectious for about one week at human body temperature, over 30 days at 0 °C (32 °F), and indefinitely at very low temperatures (such as lakes in northeast Siberia). They can be inactivated easily by disinfectants and detergents.

The flu vaccine external structure mutates all the time resulting in changes to the flu strain. Each year the influenza virus changes and different strains become dominant. Due to the high mutability of the virus a particular vaccine formulation usually works for only about a year. This requires the vaccine strain to be changed each year. One method of making flu vaccines involves the incubation of the three strains (A, B, & C) that are most expected to spread in a given year into millions of chicken eggs to multiply. This method is labor-intensive, time consuming and takes too long to produce vaccine in the case of another worldwide pandemic.

A new procedure involves the spraying of viral genes directly through the skin in a technique that turns infinitesimal amounts of DNA into an effective vaccine. The infectious disease specialist takes out a few genes from the DNA of the influenza virus and shoots it at a very fast speed into the person’s skin using ‘a new needle-free device (CDC)’. The DNA enters the cell and produces a very strong immune response. If approved for use in humans, the new procedure could save many lives in case of a flu pandemic, by skipping the current, time-consuming production of vaccines in chicken eggs.


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