Better TB vaccine in the pipeline

Oct 20 2008

Scientists in the U.S. believe they have a vaccine in the pipeline that offers better protection from tuberculosis (TB).

A team at Saint Louis University say an investigational vaccine for TB which they have tested appears to offer significantly better protection against the potentially fatal disease than the one in current use.

According to Dr. Daniel Hoft, director of immunobiology at the University's School of Medicine and lead author of the study, not only is it as safe as the standard vaccine, it induced a better immune response, which suggests it will be more effective at protecting against tuberculosis.

The new "recombinant" vaccine is made from a weakened TB germ from one of the strains of the current tuberculosis vaccine, which was created more than 75 years ago, and uses an antigen - a secreted protein from a virulent strain of tuberculosis - to help focus the immune system on blocking aggressive and deadly TB organisms.

Phase I clinical trials were conducted where the researchers vaccinated a total of 35 study participants - 17 with the standard TB vaccine -- called Bacille Calmette-Guérin (BCG) - while the other 18 received the investigational recombinant BCG vaccine.

When the researchers compared the five immune functions induced by the vaccines, the investigational vaccine was found to have induced more powerful responses important for protection against tuberculosis and was also safe and well tolerated.

The researchers say the trial demonstrated that the concept of using a recombinant vaccine holds promise in being able to better protect people from tuberculosis.

The new vaccine will not be subjected to further testing because it uses an antibiotic resistant gene that scientists want to keep out of the environment.

However Dr. Hoft says this area of research will continue as scientists test a similar recombinant BCG vaccine that expresses the same and additional key TB antigens that is expected to be even more potent than the one just studied and does not include the antibiotic resistant gene.

Dr. Hoft says a new vaccine theoretically could not only protect against the overwhelming growth of TB organisms, but could kill residual organisms after a person has become infected.

Dr. Hoft says finding a better vaccine is critical because 8 million new cases of TB develop each year, 2 million die from the infectious disease and developing nations are the hardest hit.

He says these staggering statistics persist despite the availability of a tuberculosis vaccine and new vaccines are urgently needed to reduce the immense burden of TB.

The World Health Organization recommends the current BCG vaccine for infants in developing countries shortly after they are born and while the vaccine induces only partial protection, vaccinated children who contract a tuberculosis infection have a less severe illness.

The current vaccine is about 70% protective against deaths or meningitis from tuberculosis and about 50% protective against pulmonary tuberculosis.

The research was published in an online edition of the Journal of Infectious Diseases and was funded by the Aeras Global TB Vaccine Foundation and National Institutes of Health.