Bacterial meningitis is a nasty thing to catch. The disease may hit only about 1,500 Americans per year, but those who fall victim may suffer brain damage, learning disabilities, limb loss or death.
The good news is that many strains of meningitis are preventable with bacterial vaccines that fight the various types of bugs that cause the disease. There are currently three such vaccines available in the United States: the Hib, for children younger than five; the MCV4, for people between two and 55 years of age; and the MPSV4, for those older than 55. All of these vaccines can inoculate us against most strains of the most common meningitis-causing bacteria circulating in the U.S.
The bad news is that “most” does not mean all, and the cases caused by the meningococcus B bacterium are some of the most difficult to prevent. That’s especially worrisome for two reasons: meningococcus B shows a particular affinity for infants; and it can also cause sepsis – a potentially life-threatening bacterial infection that overwhelms the bloodstream. Now, however, a team of researchers at Novartis Vaccines & Diagnostics in Siena, Italy, may have solved that problem, developing a vaccine with the power to knock meningococcus B back on its heels.
What makes this particular bacterium so slippery is that it actually comes in 300 varieties — all strains of the same bug, but each, in theory, requiring a separate vaccine. Making things a lot easier, all of the varieties are covered with one of three classes of protein that are essential for the bacteria to survive in our bodies. The protein itself can be used as the vaccine target – kind of like giving a bloodhound a scrap of a fugitive’s clothes to smell — but three different proteins can still require three different formulations.
“Even if you’re immune to [a bacterium coated with] one class, there are still two more classes you might not be immune to,” Columbia University associate professor of biochemistry Lawrence Shapiro said. “So what [the scientists] have done is … they’ve asked the question ‘Can we make a single immunogen that we could inject into people’s arms that would get all three classes?’ And they did.”
To come up with this hydra-headed vaccine, microbiologist Rino Rappuoli and his team engineered 54 immunogens — or resistance-provoking substances — composed of variations of the three proteins and introduced them into mice to see which would prompt the creation of antibodies to meningococcus B. Eight of these immunogen formulations were shortlisted for testing in further mice experiments, and from those a champion was chosen — one that was capable of inducing antibodies that would kill all 300 variants of meningococcus B. Because it covers all bases, the new immunogen may be the secret sauce for a broadly protective vaccine. If so, scientists hope that the same vaccine design strategy — in which protein coats of different strains are combined to produce a single uber-shot — can be used to fight other, similarly diverse pathogens.
“I’m not sure it’s the only way to get to a broad meningitis vaccine, but this is certainly a very scientifically elegant way to have done it,” says Shapiro. Still, he urges caution. “There have been no clinical trials in humans yet – it’s only been tested on animals. But the idea is right and it, in principle, should provide an effective meningitis vaccine.” With so many survivors left with disabilities or life-altering problems, it will be a good thing indeed when that principle becomes practice.