New tuberculosis vaccine safer, more effective than BCG vaccine for HIV-positive people

A new tuberculosis vaccine could be safer and more effective than the currently available BCG vaccine, particularly for HIV-positive people, according to a study to be published in the November issue of Infection and Immunity, IANS/Times of India reports (IANS/Times of India, 10/24).

For the NIH-funded study, Marcus Horwitz, a microbiologist at University of California-Los Angeles' David Geffen School of Medicine, and colleagues created a recombinant BCG vaccine, called rBCG(mbtB)30. The researchers increased the BCG vaccine's potency and immune response strength by altering it to produce large amounts of the protein mycolyl transferase. The researchers also made the vaccine safer by ensuring that it could only replicate a few times after immunization. To achieve this, the researchers blocked the vaccine's ability to obtain iron, which is an essential ingredient for bacterial replication, from the host. "This is one of the first vaccines developed to replicate only a few times in the host and the first to do so by eliminating the vaccine's ability to acquire iron in the host," Michael Tullius, assistant researcher at UCLA Department of Medicine's Division of Infectious Diseases, said. Horwitz added, "Preloading the vaccine with a specific amount of iron allows us control over the vaccine's safety and effectiveness in the host" (UCLA release, 10/23).

The study found that the new vaccine protected guinea pigs from TB more effectively than the BCG vaccine. In addition, the new vaccine is safer than the BCG vaccine when administered to mice with severely compromised immune systems. Although the new vaccine can be administered to anyone, it is specifically designed for HIV-positive infants and HIV-positive adults with relatively intact immune systems, including people receiving antiretroviral treatment, IANS/Times reports. According to Horwitz, HIV/TB co-epidemics "are now so intertwined in many parts of the world that we can't win the fight against one of these diseases without also taking on the other."

According to the researchers, the next step will be to conduct vaccine trials among humans, but the vaccine might not be available for several years (IANS/Times, 10/24). Ulrich Fruth of the World Health Organization's Initiative for Vaccine Research added that although TB is a major concern for HIV-positive people, the existing BCG vaccine is problematic because "it poses a health risk by itself" when administered to HIV-positive people. Fruth said it would be "wonderful news" if the new vaccine is "shown to be safe and efficacious in people with HIV" (UCLA release, 10/23).

A Voice of America interview with Horwitz is available online.

An abstract of the study is available online.