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    Protecting against MRSA

    The human immune system might provide protection from recurrent bacterial skin infections caused by Staphylococcus aureus (staph), thus leading the way to effective vaccines, according to recent findings in The Journal of Clinical Investigation, which examines both an animal (mouse) and human study.

    A vaccine to combat methicillin-resistant staph aureus (MRSA) is desperately needed because of declining antibiotic development and rising drug resistance.

    “Immunocompromised mice that had an impaired immune response against an initial exposure to MRSA in the skin were surprisingly completely protected against a second skin exposure to MRSA,” says senior author Lloyd Miller, M.D., Ph.D., an associate professor of dermatology at the Johns Hopkins University School of Medicine. “However, it took us a while to figure out how this occurred because the protection was not mediated by typical antibody responses that most vaccines against MRSA are targeting.”

    Rather, the investigators found that a single population of T cells (so-called γδ T cells) had a massive expansion in the skin-draining lymph nodes, increasing from less than 1% to more than 20% of the T cells present.

    “These cells then migrated to the skin and protected the mice against a second exposure to MRSA,” Dr. Miller tells The Aesthetic Channel.

    Separately, in collaboration with the National Institutes of Health (NIH), the investigators discovered that adult humans with a rare condition making them highly susceptible to MRSA skin infections in childhood had a similar expansion of these T cells in their blood when they became adults and were no longer predisposed to infection.

    “This suggests that a similar protective response that we found in mice might also occur in humans,” Dr. Miller says.

    Dr. Miller notes there are several pharmaceutical companies in FDA Phase II studies evaluating passive and active vaccines against certain types of MRSA infections in humans, including postsurgical MRSA infections and protection against MRSA pneumonia that can be life-threatening for ventilated patients in hospital intensive care units.

    “Hopefully, such vaccines will promote protection in these specific infections,” Dr. Miller says. “The use of vaccines could also be expanded to protect people from MRSA skin infections and other types of infections like skin abscesses, sepsis and osteomyelitis.”

    The published article suggests that in addition to antibodies, “T cell responses should be looked at in human vaccine trials against MRSA,” Dr. Miller concludes.


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