Imagine your young son has a rare disease that makes him susceptible to infections. If he catches the measles, will he be able to successfully fight it off? A researcher at Université de Montréal has discovered how to ensure he will—by getting him vaccinated.

For people generally, vaccination is an effective way to fight infections, noted Sylvie Lesage, a professor of immunology at UdeM and researcher at the Maisonneuve-Rosemont Hospital Research Centre. And it seems that vaccination also works in the context of certain rare diseases, she found. Since rare diseases are little studied, this solution is very promising.

“Vaccines do work, that's undeniable," said the researcher, whose study on the subject is published today in PLOS ONE. “What's significant is that even in patients with a rare disease, measles vaccination, for example, could significantly help them get through an infection that would normally be very harmful to their health and require medical intervention.”

Thanks to the support of the Fondation du Grand Défi Pierre Lavoie, and in collaboration with other Quebec specialists, Lesage is conducting a research project on congenital lactic acidosis, a very rare mitochondrial disease. Quebec has more cases than any other jurisdiction: there are less than 15 people with the disease here, making it one of the rarest diseases in the world.

Particular to three Quebec regions

Congenital lactic acidosis is one of the hereditary recessive diseases most common in certain regions of Quebec: Saguenay-Lac-Saint-Jean, Charlevoix and the Haute-Côte-Nord. The disease is caused by the malfunctioning of an enzyme called cytochrome-c-oxidase which produces the energy the human body needs to function properly.

While their liver is particularly affected, people with the disease have high levels of lactic acid in their blood causing developmental delays, neurological disorders and a considerably reduced life expectancy. Nearly 85 per cent of affected children die before the age of 5 years; a few other patients are between 20 and 30 years of age, but have reduced autonomy.

In their study, Lesage and her team demonstrate that patients who have received the two recommended doses of the measles, mumps, and rubella vaccine are able to mount effective immune responses.

‘Good news for patients’

“This is good news for patients with lactic acidosis,” she said. “Knowing that infections significantly diminish their health, our work suggests that the administration of vaccines could be beneficial for patients with this disease, while respecting Health Canada's vaccination recommendations and, most importantly, those of their physicians.”

It remains to be seen whether the response to vaccines will also be strong in people with another type of rare disease. Nearly 500,000 Quebecers today suffer from some kind of rare disease.

As a follow-up to their study, Lesage's research group has developed an animal model that reproduces certain characteristics of lactic acidosis. Researchers will use this model to see if it is possible to predict what exactly triggers attacks of the disease.