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Why some children may get strep throat more often than others

Tonsil tissue from kids with recurring infections have smaller key immune structures

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2:16pm, February 6, 2019
a microscopic image showing differences in immune structure in tonsils between kids with and without repeat strep throat infections

SMALLER CENTERS  Certain important immune structures (brown) in the tonsils of children who had recurrent strep throat infections (left in these microscope images) were smaller than those in tonsils from kids who hadn’t had repeat infections (right).

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For kids, getting strep throat again and again is a pain. It’s also a problem little understood by scientists. Now a study that analyzed kids’ tonsils hints at why such repeat infections may happen.

Children with recurrent strep infections had smaller immune structures crucial to the development of antibodies in their tonsils than kids who hadn’t had repeated infections, researchers found. The frequently sore-of-throat were also more susceptible to a protein, deployed by the bacteria that cause the infection, that disrupts the body’s immune response, the team reports online February 6 in Science Translational Medicine.

Globally each year, there are an estimated 600 million cases of strep throat, which commonly produces a sore throat and fever. Doctors treat the illness with antibiotics, especially in children, who are at highest risk of developing rheumatic fever and heart problems from a strep infection. But some kids, even though they get treatment, repeatedly develop new cases of strep throat.

In the study, immunologist Shane Crotty of the La Jolla Institute for Immunology in California and colleagues examined tonsils, the immune tissue found at the back of the throat, that had been removed from 5- to 18-year-olds. Some of the children had their tonsils taken out because of recurrent strep infections. Others had their tonsils removed to resolve sleep apnea caused by enlarged tonsils; this group was a proxy for kids not plagued by repeated bouts of strep.

The team looked at sections of tissue under a microscope and found that kids with recurring strep had smaller immune structures called germinal centers, and the centers had fewer of a particular kind of immune cell, a type of T cell. Those T cells help other immune cells, known as B cells, make antibodies that help the body fight an infection.

The kids with recurring strep also had fewer antibodies to a protein, used by the bacteria called group A Streptococcus, that interferes with the immune response to the pathogen. That may make the children more susceptible to infections, Crotty says.

The research is elegant and intriguing, says pediatrician Stanford Shulman, who specializes in infectious disease at the Ann & Robert H. Lurie Children’s Hospital of Chicago and was not involved in the study.

But one caveat, he says, is that sometimes kids classified as having recurrent strep infections are actually carriers of group A Streptococcus, meaning the bacteria is latent in their tonsils but not causing symptoms. In those cases, a sore throat due to a viral infection would still come up as strep in a test. It’s estimated that roughly 20 percent of school-aged children are chronic carriers of group A Streptococcus.

It’s possible the seemingly defective immune response towards strep that the study reports could be due to some of those kids being carriers of the bacteria rather than having active strep infections, Shulman says. In future work, it would be helpful to determine which kids have true recurrent infections and which kids are strep carriers, he says.

Citations

J.M. Dan et al. Recurrent group A Streptococcus tonsillitis is an immunosusceptibility disease involving antibody deficiency and aberrant TFH cells. Science Translational Medicine. Published online February 6, 2019. doi:10.1126/scitranslmed.aau3776.

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