THURSDAY, March 6 (HealthDay News) -- A stabilized form of a protein found on streptococcus bacteria may provide protection against strep infections, a new study suggests.

A team led by University of California, San Diego (UCSD), researchers developed the first detailed description of the structure of the streptococcal M protein, which plays a critical role in the virulence of Group A Streptococcus (GAS), which causes a number of diseases, including strep throat, rheumatic fever and necrotizing fasciitis ("flesh-eating" disease).

The researchers conducted tests using M1 protein, the version of the M protein present on the most common disease-associated GAS strains. They also produced a variant of M1 that stimulates the immune system in mice, without causing any of the negative health effects of the natural M1 protein.

These investigations, described in the March 7 issue of Science, may help scientists develop M1 protein-based vaccines against GAS, the researchers said.

"Using X-ray crystallography, we determined that M1 protein has an irregular, unstable structure. We created a modified version of M1 with a more stable structure, and found that it is just as effective at eliciting an immune reaction, but safer than the original version of M1, which has serious drawbacks to its use as a vaccine," Partho Ghosh, a professor of chemistry and biochemistry in UCSD's Division of Physical Sciences, said in a prepared statement.

"Certain antibodies that are produced by the immune system against M1 protein have been shown to cross-react with normal human tissues, including heart muscle, potentially triggering the serious autoimmune disease known as rheumatic fever," said Victor Nizet, a professor of pediatrics and pharmacy at the UCSD School of Medicine and the Skaggs School of Pharmacy and Pharmaceutical Sciences.

"M1 protein can also act as a toxin, producing clotting abnormalities and lung injury when injected into mice. Therefore, our results with modified M1 provide very novel insight about the role of M proteins in invasive GAS disease and rheumatic heart disease," Nizet said in a prepared statement.

Each year, strep infections afflict more than 600 million people worldwide and kill 400,000, according to background information in a news release about the research.

More information

The U.S. Centers for Disease Control and Prevention has more about Group A Strep.

WEDNESDAY, March 26 (HealthDay News) -- A study showing the rapid weakening of unused breathing muscles during mechanical respiration could lead to improved survival for people who are put on ventilators in intensive care units, researchers say.

"What we think our work does is open the possibility of pharmacologically blocking the signaling pathways that mediate atrophy of these fibers," said study author Dr. Sanford Levine, a professor of surgery at the University of Pennsylvania. He is the lead author of a report on the finding, published in the March 27 issue of the New England Journal of Medicine.

Levine and his colleagues looked at the microscopic condition of muscle fibers from the diaphragms of 14 brain-dead organ donors placed on mechanical ventilation for 18 hours or more and similar fibers from eight people who had mechanical ventilation for two to three hours because of lung surgery.

Earlier work in rats by another member of the research team, Scott K. Powers of the University of Florida, showed rapid breakdown of diaphragm muscle fibers during prolonged mechanical ventilation, Levine said. In the human studies, he said, "the results were pretty much what we saw in the animal studies, a 57 percent decrease in the cross-section of slow fibers, a 53 percent decrease in the fast fibers."

"We were quite amazed at the rapidity with which atrophy developed," Levine said.

About one-third of patients in intensive care are mechanically ventilated, with a machine generating a controlled flow of air to the respiratory system. There has been a running controversy about how much rest the diaphragm muscles should get, Levine said: "If you rest these muscles completely, are you going to get into trouble?"

At least one study has shown that periodically stopping mechanical ventilation, a "wake-up-and-breathe" protocol, improves results. The detailed results of the new study give molecular backing to that idea.

The findings also raise the possibility of blocking the pathways that cause muscle degeneration, Levine said. "There are more than one pathways, which probably are not completely separate," he said. "These pathways signal reactive oxygen species to set off this signaling. There could be pharmacological agents we could give to patients who go onto mechanical ventilation and hopefully have a major impact on getting them off the ventilator."

It is "quite an important study," said Gary C. Sieck, chairman of the department of physiology and biomedical engineering at the Mayo Clinic, and co-author of an accompanying editorial. "There have been studies in animals in the past," he said. "This is the first study to actually show in humans how sharply mechanical ventilation can lead to decrease in the strength of respiratory muscles."

In terms of medial practice, "this may call for a change, to get patients off mechanical ventilators as early as possible," Sieck said.

What the study shows is that too much inactivity can be bad for respiratory muscles, he said. "Resting these muscles could be comparable to bed rest for patients," he said. "You get weaker with bed rest. And astronauts in space come back with weakened muscles."

More information

Learn about mechanical ventilation from the American Thoracic Society  .

(HealthDay News) - Allergic reactions can range from very mild to life-threatening. Severe allergic reactions require immediate medical attention, but even reactions that are milder should be checked out by a doctor.

Here are warning signs of a mild allergic reaction, courtesy of the U.S. National Library of Medicine:

• Skin rash.
• Hives, especially on the neck or the face.
• Itchy skin.
• Red or watery eyes.
• Nasal congestion.

If you have more serious symptoms of an allergic reaction, including difficulty breathing, swelling, dizziness, chest discomfort, abdominal pain, or feelings of apprehension and anxiety, seek medical attention as soon as possible.