Human trials are still a few years away, but the unconventional methods the researchers used to create immunity in mice could hold key to HIV and TB vaccines as well.
Scientists have developed a new, counterintuitive vaccine to prevent the spread of herpes – the most common sexually transmitted infection with over 500 million suffers. Researchers at the Albert Einstein College of Medicine at Yeshiva University published their findings of experiments conducted on lab mice in eLife.
“Developing a herpes vaccine is one of the holy grails of infectious disease research,” said Dr. William Jacobs, Jr., co-study leader.
The scientists were able to create the vaccine by taking a new approach to vaccine development. It had been assumed that the way to fight the virus was to stimulate production of neutralizing antibodies against a specific viral surface protein (glycoprotein-2) the herpes simplex virus-2 (genital herpes) uses invade cells. Researchers spent decades trying to stimulate antigens against gD-2 – but these versions of the vaccine were unable to prevent infection.
“We decided to take an approach that runs counter to most of the tactics used by other scientists – and we seem to have cracked the code,” said Dr. Jacobs. This, according to Dr. Betsy Harold co-study leader, suggested that previous vaccine strategies were stimulating the wrong antibodies.
Instead the Einstein group used genetic manipulation to remove the gD-2 gene from HSV-2 DNA to design a live vaccine. This weakened the virus and made it unable to infect cells in lab mice that were given the live vaccine.
The vaccinated mice showed low levels of neutralizing antibodies but high levels antibodies associated with a different immune response called antibody-dependent cell-mediated cytotoxicity (ADCC). A blood serum from these vaccinated mice was then used in other mice who showed signs of passive protection against HSV-2, showing that ADCC protects against HSV-2.
“We had a hunch that gD-2 might be masking other viral antigens,” said Dr. Jacobs. “And that by removing this dominant protein we would expose those previously masked antigens to the immune system.”
Tests also suggest that the virus offers some protection against HSV-1 (oral herpes) but further testing is needed. The vaccine design also opens up possibilities for other vaccines against viruses, including HIV and tuberculosis.
“Genital herpes infections can not only be seriously in and of themselves, but they also play a major role in fueling the HIV epidemic,” said Dr. Herold, who explained that people infected with HSV-2 are more likely to get and transmit HIV.
The team hopes to begin human trials in the next few years.