A new approach to a Covid-19 nasal vaccine shows early promise
Scientists in Germany say they’ve been able to make a nasal vaccine that can shut down a Covid-19 infection in the nose and throat, where
Scientists in Germany say they’ve been able to make a nasal vaccine that can shut down a Covid-19 infection in the nose and throat, where the virus gets its first foothold in the body. In experiments in hamsters, two doses of the vaccine – which is made with a live but weakened form of the coronavirus that causes Covid-19 – blocked the virus from copying itself in the animals’ upper airways, achieving “sterilizing immunity” and preventing illness, a long-sought goal of the pandemic. Although this vaccine has several more hurdles to clear before it gets to a doctor’s office or drug store, other nasal vaccines are in use or are nearing the finish line in clinical trials. China and India both rolled out vaccines given through the nasal tissues last fall, though it’s not clear how well they may be working. Studies on the effectiveness of these vaccines have yet to be published, leaving much of the world to wonder whether this approach to protection really works in people. Halting progress on next-generation Covid-19 vaccines The US has reached something of a stalemate with Covid-19. Even with the darkest days of the pandemic behind us, hundreds of Americans are still dying daily as the infection continues to simmer in the background of our return to normal life. As long as the virus continues to spread among people and animals, there’s always the potential for it mutate into a more contagious or more damaging version of itself. And while Covid infections have become manageable for most healthy people, they may still pose a danger to vulnerable groups such as the elderly and immunocompromised. Researchers hope next-generation Covid-19 vaccines, which aim to shut down the virus before it ever gets a chance to make us sick and ultimately prevent the spread of infection, could make our newest resident respiratory infection less of a threat. One way scientists are trying to do that is by boosting mucosal immunity, beefing up immune defenses in the tissues that line the upper airways, right where the virus would land and begin to infect our cells. It’s a bit like stationing firefighters underneath the smoke alarm in your house, says study author Emanuel Wyler, a scientist at the Max Delbruck Center for Molecular Medicine in the Helmholtz Association in Berlin.
The immunity that’s created by shots works throughout the body, but it resides primarily in the blood. That means it may take longer to mount a response. “If they are already on site, they can immediately eliminate the fire, but if they’re like 2 miles away, they first need to drive there, and by that time, one-third of the house is already in full flames,” Wyler said. Mucosal vaccines are also better at priming a different kind of first responder than injections do. They do a better job of summoning IgA antibodies, which have four arms to grab onto invaders instead of the two arms that the y-shaped IgG antibodies have. Some scientists think IgA antibodies may be less picky about their targets than IgG antibodies, which makes them better equipped to deal with new variants. The new nasal vaccine takes a new approach to a very old idea: weakening a virus so it’s no longer a threat and then giving it to people so their immune systems can learn to recognize and fight it off. The first vaccines using this approach date to the 1870s, against anthrax and rabies. Back then, scientists weakened the agents they were using with heat and chemicals. The researchers manipulated the genetic material in the virus to make it harder for cells to translate. This technique, called codon pair deoptimization, hobbles the virus so it can be shown to the immune system without making the body sick. “You could imagine reading a text … and every letter is a different font, or every letter is a different size, then the text is much harder to read. And this is basically what we do in codon pair deoptimization,” Wyler said. Promising results in animal studies In the hamster studies, which were published Monday in the journal Nature Microbiology, two doses of the live but weakened nasal vaccine created a much stronger immune response than either two doses of an mRNA-based vaccine or one that uses an adenovirus to ferry the vaccine instructions into cells. The researchers think the live weakened vaccine probably worked better because it closely mimics the process of a natural infection.
The BriefWire