This year’s flu season will go down as one of the most severe in nearly a decade, resulting in record hospitalization rates and many deaths, including nearly 100 children. One reason so many were stricken: the seasonal flu vaccine failed to protect a significant number of people against the virus.
Seasonal vaccines are often unreliable because they can only target specific strains of the flu virus. Each year, six months before flu season starts, scientists work with the World Health Organization to predict which strains are most likely to infect the public that year. They make their determination so early to give manufacturers the time they need to produce the vaccine.
That means the seasonal vaccine’s effectiveness depends entirely on the accuracy of the predictions used to develop it.
“We still use the traditional method to make the flu vaccine, and we face the same challenges year after year,” says Bao-Zhong Wang, associate professor in the Institute for Biomedical Sciences.
“[The WHO] prediction is not always correct,” says Sang-Moo Kang, professor in the Institute for Biomedical Sciences. “If there’s a mismatch, the vaccine’s efficacy is severely low.” The CDC estimates the 2017–18 seasonal flu vaccine was only 30 to 40 percent effective.
Wang and Kang are leading a group of scientists that are trying to fight the flu with a different approach: a universal vaccine that could potentially protect against any strain, eliminating the guesswork and gamble of the seasonal vaccine.
Wang and his team have made great strides toward the development of a “super vaccine” by targeting an interior part of the virus’ surface protein, called the hemagglutinin (HA) stalk. This interior part is the same in all influenza viruses, yet seasonal flu vaccines target the protein’s exterior head, which varies widely from strain to strain. Wang’s super vaccine would combine the interior parts of three surface proteins that can each induce an immune response from the human body.
In a paper published earlier this year in Nature Communications, Wang and his colleagues found the vaccine produced long-lasting immunity and fully protected mice against various influenza A viruses.
Meanwhile, Kang’s team is targeting an entirely different protein, the M2 protein, which is more constant across different strains of the flu compared to the HA surface protein. To do so, they’ve created particles that resemble the influenza virus and are around the same size — about 100 nanometers across — and contain the M2 protein. They then transmit the particles using the baculovirus, which can only replicate in insects, not mammals or humans.
“There’s no way for it to become infectious [in humans], but it mimics the size, structure and shape of the virus,” says Kang. “We are incorporating the M2 components from human, swine and avian flu strains, so we’re expecting it to cover the whole range of influenza viruses.”
In a recent study published in the journal Frontiers in Immunology, Kang and his colleagues demonstrated their vaccine worked better than the seasonal flu vaccine to induce effective cross-protection against several influenza viruses, including H1N1, which killed more than half a million people in 2009, H3N2 and H5N1, a strain of the avian flu.
Illustration by Alan Reid Schultz (B.A. ’18)
One weapon to fight the flu could be found in probiotics. Sang-Moo Kang has discovered that lactic acid bacteria, commonly used as probiotics to improve digestive health, can protect mice against different subtypes of influenza A.
In a recent study published in the journal Scientific Reports, Kang pretreated mice with a heat-killed strain of lactic acid bacteria and then infected them with lethal doses of influenza A virus. The mice had a 100 percent survival rate and didn’t lose weight. They were also equipped with cross-protective immunity against a second lethal infection with the flu virus.
The study provides evidence that heat-killed lactic acid bacteria could be potentially administered in the form of a nasal spray to protect against influenza virus infections.
A Better Flu Test
Methods of diagnosing the flu are often expensive, not sensitive enough and require trained personnel to administer them. Suri S. Iyer, associate professor in the Department of Chemistry, and his colleagues have designed a simple test to detect influenza viruses in 15 minutes.
The test requires only a nasal swab and detects a specific protein on the surface of the virus to identify the two major strains of the flu in humans: influenza A and influenza B. Funded by the National Institutes of Health, the research was recently licensed to a biotech firm, Pinnacle Bio, and could provide a faster, more cost-effective flu test.