Vitamin D does not protect all babies against RS virus.jpg?n=8730" border="2" />Immunological research at UMC Utrecht has revealed why some babies become so ill after being infected with the RS virus that they end up in hospital. It was found that they are not helped by providing them vitamin D, which offers protection to most children. The results of the study were published this week in the Journal of Pathology.

Infection with the RS virus is the most common reason for hospital admissions of new-borns. This virus can cause severe lung infection if the baby’s immune response is too violent. Almost all babies are infected with the RS virus before the age of two, but about one in a hundred responds to it so violently that they have to be admitted to hospital.

Vitamin D protects against the RS virus

It is still unclear how the immune system can become so unhinged. But scientists have known for a long time that babies need vitamin D to protect them against the RS virus. Babies with insufficient levels of vitamin D in their blood are more susceptible to the virus. The nature of this relationship, however, was unclear. 

Medical biologist Dr Marianne Boes, PhD student Arie Jan Stoppelenburg and their colleagues at University Medical Center Utrecht (the Netherlands) have now connected the dots. It turns out that vitamin D dampens down the immune system. If a baby gets infected with the RS virus, its immune system launches a counter attack. If that immune response is excessive, lung cells are damaged and a kind of pneumonia develops. Vitamin D puts a brake on the immune response, so that the immune system’s attack on the infection has exactly the right strength.

Using genetic research, Marianne Boes and her colleagues found a number of people with the differently shaped vitamin D receptor. They discovered that in the cells of these healthy volunteers, vitamin D indeed does not act as a brake. The results are in line with previous genetic research showing that babies with a differently shaped vitamin D receptor have a 70 percent greater risk of contracting pneumonia due to the RS virus.

 “This means that taking sufficient vitamin D is not always sufficient to protect against the RS virus,” Boes explains. “In babies with a differently shaped receptor, vitamin D cannot ‘hit the brake’. These children could be given preventive treatment with a new but expensive drug. In theory, it would be very feasible to find these babies using genetic research.