SYDNEY, Aug. 14 (Xinhua) -- Exposure to a mild or symptom-free strain of Streptococcus pyogenes (Strep A) can trigger the body's immune response and build natural protection, potentially solving a nearly 100-year-old mystery of immunity, new research reveals.
The study by Australia's Griffith University, in collaboration with the Murdoch Children's Research Institute, investigated how immunity developed over time as infection rates declined with age, suggesting progressive immune protection, according to a university statement released on Thursday.
The findings, published in Nature Communications, may help explain why most people develop immunity to Strep A by adulthood despite having had only a few bouts of tonsillitis.
Strep A can cause tonsillitis and school sores and, if untreated, can lead to rheumatic fever, rheumatic heart disease and kidney disease, which disproportionately affect Australia's First Nations peoples.
Researchers found that both symptomatic and asymptomatic participants developed robust immune responses after exposure to a Strep A strain. Antibodies from the asymptomatic participants were able to bind strongly to the exposed strain and kill the Strep A germ in a mouse model of tonsillitis.
"While a person may not feel sick, their body can still learn how to fight the bacteria and remember it from childhood into adulthood," said Ailin Lepletier, the study's lead author from Griffith University.
Up to 30 percent of people are known to carry Strep A in their throats without getting sick, suggesting such "silent infections" may help people gradually build immunity to most strains, Lepletier said. ■
