Researchers have successfully developed a new model of human Strep A challenge, paving the way for vaccine testing against common deadly bacteria that cause sore throats, scarlet fever, and skin sores.
The collaborative research effort, led by the Murdoch Children’s Research Institute (MCRI) and published in The Lancet microbe, found that the model, which deliberately infected healthy adult volunteers with the bacteria in a controlled environment, was safe and would now be used to test candidate Strep A.
Strep A infections affect an estimated 750 million people and kill more than 500,000 worldwide each year – more than the flu, typhoid or whooping cough. Streptococcus A can also cause serious, life-threatening infections such as toxic shock syndrome and flesh-eating disease and post-infectious diseases such as rheumatic fever, rheumatic heart disease, and kidney disease.
Strep A infections disproportionately affect young children, the elderly, pregnant women and Indigenous Australians. There is currently no vaccine available to prevent Streptococcus A and can only potentially be treated with antibiotics.
MCRI’s Dr Josh Osowicki said that since Strep A is only infected naturally, researchers are limited in what they can learn in the lab and using animal models.
“Human challenge models can be used to test vaccines, drugs and diagnostic tests, as well as to conduct all kinds of wonderful scientific collaborations to better understand how diseases work and how to stop them,” he said. declared.
“We have developed the only current model of controlled human Strep A infection, ready to be used as a platform to evaluate new vaccine candidates and therapeutics.
Dr Osowicki said the research team tested a strain of Strep A that they believed would cause strep throat and was unlikely to cause acute or chronic health problems.
The study involved 25 volunteers, aged 18 to 40, who stayed at the Nucleus Network, a Melbourne-based Phase 1 clinical trials unit for up to six days with blood tests and saliva samples and throat regularly collected.
Dr Osowicki said that 85% of the participants developed a convincing case of strep throat, well above the at least 60% expected.
“Starting with a tenth of the dose used in old studies from the 1970s, we applied our special strain Strep A to the back of each participant’s throat,” he said. “To our surprise, from the very first participant in the low starting dose, our strain caused strep throat in most of the participants.”
The volunteers developed mild to moderate symptoms, including sore throat, sweating, fever, and headache. All recovered quickly and were followed for six months after being sent home, according to the study.
Eden, the daughter of Melbourne resident Tania O’Meara, was only 11 months old when she nearly lost her leg due to a carnivorous bacterial infection caused by Strep A.
“We put our daughter to bed with what appeared to be a cold, but the next morning she woke up with a fever and was very pale and limp and dehydrated,” she said.
“We took her to the hospital but the doctor couldn’t get the intravenous drip because Eden was so dehydrated and they were forced to pierce her in her leg. They also noticed that the skin on his leg seemed to change color. “
Ms O’Meara said Eden needed surgery on her right calf to remove the dead flesh.
“We were told she could die and we prepared, so it’s a miracle they were able to save her leg and even her calf,” she said.
Eden, now three, needed three more surgeries and has since made a full recovery.
Ms O’Meara said she was relieved that a vaccine for Stage A might not be too far away.
“I don’t want another family to go through what we’ve been through. It’s an absolute tragedy that this bacteria is cutting so many lives,” she said.
MCRI’s Professor Andrew Steer said the team is expected to start testing candidate Strep A vaccines developed by researchers in Australia and abroad before the end of the year.
The trials, to be conducted in Melbourne, would involve around 50 participants receiving a candidate vaccine or a placebo and having the Strep A challenge strain applied to their throats.
“The global burden of strep A is an unresolved public health challenge. We hope this research will speed up vaccine development and move things forward towards larger field trials, ”said Prof Steer.
“A vaccine against Streptococcus A will save hundreds of thousands of lives each year and prevent millions of infections that send children and adults to hospitals and doctors.”