Two interesting papers from PNAS were published online today, showing a potential role for microbes in two vastly different diseases: prostate cancer and Kawasaki disease.

Many of you are probably well aware of prostate cancer, the second leading cause of death of men in the US. It is typically diagnosed in older men, and an estimated 1 in 7 men will diagnosed with prostate cancer in their lifetime.

Kawasaki disease is a rarer affliction in children, resulting in inflammation of important organs such as the heart. While the incidence is highest in Japan and several other Asian countries, it is increasing in the US, with thousands of hospitalized children each year. Most children recover, but serious complications of the heart can result in death.

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In the prostate cancer study, researchers found that the STD, Trichomonas vaginalis, can secrete a mimic of a human protein, MIF, that can activate the immune system and cause inflammation. While one would think immune activation is good, chronic inflammation can actually promote tumor development through driving growth and invasive capability of the tumor.

In the Kawasaki disease study, the researchers looked at the wind patterns associated with large outbreaks in Japan to look for windborne disease factors. They were able to pinpoint it to a northeastern region of China, where they found a high incidence of Candida fungus. Due to the short period of time between exposure and symptoms, the researchers postulate that a fungal component is triggering an immune response, resulting in disease.

I want to stress that both studies show correlative data that makes for a compelling hypothesis, but further studies need to be completed to prove that these bugs are contributing/causing disease. While very different diseases and pathogens, both cases have a similar hypothesis, where exposure to microbes can elicit an immune response which hurts your own body. The immune system is a carefully balanced system, and sometimes germs can throw that balance off, resulting in disease. It's part of the reason why I'm so fascinated with the immune system, and I hope that we can learn to control this balance.