Skipping the Immune System

Could bypassing the body's immune system be the best approach for a preventive vaccine? Absolutely, say researchers at the Children's Hospital of Philadelphia (CHOP). Whereas most attempts at developing an HIV vaccine have aimed at stimulating the body's immune system to produce HIV-neutralizing antibodies or killer cells, the CHOP researchers write in the journal Nature Medicine that they designed a vaccine candidate that "leapfrogged" the immune system. Instead, their approach encouraged other cells in the body to produce molecules designed to bind to and disable invading virus. Lab and animal experiments showed that using an engineered adenovirus to carry DNA coding into the body for the construction of immunoadhesin proteins resulted in rapid production of the molecules and high concentrations of them in the bloodstream. The majority of monkeys who were vaccinated and then exposed to the simian version of HIV were completely protected against infection, and even those animals that did contract SIV never progressed to AIDS. By contrast, all unvaccinated animals were infected with SIV and two thirds died. High concentrations of the immunoadhesins remained in the blood of vaccinated animals for more than a year. The researchers are calling for further studies to determine if their vaccine approach is effective in preventing HIV infection in humans. They also believe additional tests may prove their approach useful in developing preventive and therapeutic vaccines for other infectious diseases like malaria.