Experimental Anti-Tick Vaccine Aims to Stop Bites That Could Spread Lyme

Female Ixodes pacificus tick, one of the two primary species that spread Lyme disease in the United States.  Lyme is caused by the bacterium Borrelia burgdorferi.

Ino Ixodes pacificus tick, one of the two primary species that spread Lyme disease in the United States. Lyme is caused by the bacteria Borrelia burgdorferi.
Photo: James Gathany; William L. Nicholson / CDC

In the not-so-distant future, campers and migrants may be able to receive a shot that not only protects them from Lyme disease but also of the blood-sucking ticks that spread it — at least if Yale led research on tick-borne vaccine continues to show promise. In a new study involving guinea pigs, an an experimental mRNA-based vaccine induced an immune response to tick bites that made it difficult for insects to finish eating. hosts and infect them with Lyme bacteria.

Tick-borne diseases are the most common diseases spread by insects or arachnids in the United States annually, where Lyme disease is number one. More than 30,000 cases of Lyme are diagnosed each year, although the true number is likely to be 10. times higher, according to the Centers for Disease Control and Prevention. Although these infections are mostly treatable with antibiotics, undiagnosed cases can lead to serious complications such as chronic joint inflammation and nerve damage. Longer summers and warmer winters fueled by climate change also have expanded the range and survivability of disease-carrying ticks, leading to more cases over time.

As with most infectious diseases, a vaccine would be the largest a practical way to deal with Lyme’s threat. There is a vaccine available for dogs, and for some time during the early 2000s, there was one for humans as well. But by 2002, the human vaccine, called LYMERix, had been taken off the market by its manufacturers, who cited “insufficient consumer demand.” The lack of popularity of the vaccine was largely nourished by members of the modern anti-vaccination movement, who later spread denied claims about its lack of safety.

There are other Lyme vaccines now being developed, with the furthest from Pfizer reached Phase II trials this year. But researchers at Yale University School of Medicine and elsewhere are working on a new kind of vaccine that could go beyond just preventing Lyme. Instead of training the immune system to simply recognize Lyme bacteria, their vaccine is intended to make the immune system improve its source of transmission: the bite of a female tick.

“All human vaccines directly target pathogens. This would be the first vaccine that does not target the pathogen. Rather targeting the tick, you prevent the transmission of a pathogen. In this case, the agent of Lyme disease,” he told Gizmodo in an email Erol Fikrig, an epidemiologist and specialist in vector-borne diseases at Yale. It would also ideally prevent the transmission of other tick-borne bacteria and viruses, of which there is many.

The vaccine is thought to work by immunizing the body against the saliva of an unhealthy tick. To do this, the vaccine uses mRNA-based delivery system – the same type used for the Pfizer and Modern vaccines against COVID-19. The mRNA delivers instructions to cells to produce several of the antigens (proteins) found in ticks that most likely receive the attention of the immune system. These antigens will then induce immune cells into a short-lived battle, one that will leave a lasting memory.

After a tick tries to bite a vaccinated person, the hope is that its saliva will trigger an almost immediate immune response. This reaction should then make it difficult for the tick to naturally finish its meal, which can last up to three days, and also alert the person. to the presence of persistent blood theft so that they can safely remove the tick. Usually, it takes for a day or longer for a bite to get past Lyme, so interrupting the tick’s dinner should also protect against infection. The immune reaction would most clearly be felt as noticeable inflammation and redness at the bite site.

In their latest study, published On Wednesday at Science Translational Medicine, Fikrig and his team injected guinea pigs with the experimental vaccine, then introduced them to hungry and sometimes Lyme-carrying ticks. As expected, the skin of these vaccinated pigs reacted to the ticks shortly after they ate. And compared to control ticks, the ticks on the vaccinated animals could barely eat, and many soon detach themselves. Most importantly, when infected ticks were removed from pigs as soon as the reaction was apparent, they prevented Lyme infection.

“We have shown that by changing the ability of a tick to take blood food, you can prevent an animal from being infected by the Lyme disease agent,” Fikrig said.

Because guinea pigs, like humans, are not natural hosts of the ticks that spread Lyme, it is hoped that the group’s vaccine would create a similar immune response to tick bites in humans (natural hosts tend not to produce much immune response to bites. of the complex gift dance between parasite and host). But there is still more to do before we can wait for a vaccine to be available at a doctor.

Some of the saliva proteins the group tested here did not generate much immune response in this study, for example, so there may be room for improvement. And even before human testing could begin, the team is looking for evidence that the vaccine will work reliably in humans. The safety of any experimental medication or vaccine should also be monitored as much as possible. But the team is moving full steam ahead with their work.

“We’re testing the vaccine in other animals,” Fikrig said, “and to determine whether people with Lyme disease and other signs of tick exposure have antibodies to any of the targets in the vaccine.. ”

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