A Virus Lies in You
Amanda Fierro (12:00 Micro) sent me this summary from Science Daily on the viral microbiome, which is something that scientists have begun to characterize only very recently. Identification of the bacterial flora is relatively straightforward–collect samples from people, and culture the organisms on microbiological media. The challenge with this approach is with organisms that might be present, but present in relatively small proportions, become difficulty to characterize; kind of like looking for a needle in a haystack. Viruses add another level of complexity since they are not able to be directly grown on microbiological media (you have to have the host cell that they infect), and as a result if you are trying to find them, it is kind of like looking for hay-colored needles in a haystack. It really ONLY became possible to do this type of experiment with the advent of cutting-edge DNA sequencing techniques. Here is Amanda’s summary:
The following summary is about an article found on Science Daily concerning viruses. We’ve learned about the bacterial flora of the human body in class but there also is a viral flora. The article is about the findings of a study researching the various viruses that may reside in the human body. The research was performed at the Washington University School of Medicine as part of the Human Microbiome Project. The study is the first comprehensive analysis to describe the variety of viruses in healthy people.
According to the researchers, healthy individuals on average harbor about five types of viruses. Researchers have discovered the standard viral flora to be rich and complex. The study performed consisted of 102 healthy adults between the ages of 18 and 40. Each volunteer was carefully screened to confirm health and the absence of symptoms of acute infection. The volunteers could not have been diagnosed with an HPV infection within the last two years or have an active genital herpes infection. Researchers split the human subjects as evenly as possible by gender. Researchers sampled five body habitats: nose, skin, mouth, stool and vagina. The results indicated an impressive number of viruses found in the sampled body habitats of the subjects. As one can guess, many more would have been discovered if the entire human body had been sampled.
In 92% of the subjects, at least one virus was found. Some of the individuals sampled were home to 10-15 viruses. Half of the subjects were sampled two or three times during the course of the study. Researchers observed some of the viruses created stable low-level infections in those individuals. While analyzing all of the collected samples, the researchers discovered seven families of viruses. Herpesvirus 6 and Herpesvirus 7, strains of the herpesvirus not sexually transmitted, were found in 98% of the mouth samples. Seventy-five percent of the skin samples and 50% of the nose samples harbored some strains of the papillomavirus. The researchers encountered novel strains of the virus present in both the skin and the nose habitats. The vagina was dominated by the papillomavirus—38% of the female subjects carried strains. Some of the women possessed high-risk strains that increase the risk of cervical cancer. The high-risk strains were more common in women whose vaginal bacteria had low levels of Lactobacillus and high levels of Gardnerella. Lactobacillus is a good bacteria for humans that helps protect against bad bacteria. Gardnerella is the bacteria that produces bacterial vaginosis. Adenoviruses also were found in the various body habitats sampled. The common cold and pneumonia are caused by adenoviruses. In addition, the researchers had scientists at the university’s Genome Institute sequence the viral DNA of what was discovered by the study. They concluded each volunteer subject had a distinct viral fingerprint.
The study’s researchers admit they do not know whether the viruses have a positive or a negative effect on the overall health of the human body. They do hypothesize some viruses may keep the immune system prepared to respond to dangerous pathogens while other viruses may increase the risk of illness. The researchers also admit to the possibility the viruses discovered could have been latent viruses the subjects acquired years earlier, but they do not believe that is the case. They believe the viruses found to be active. Many of the viruses found during the study were discovered in body secretions where the presence of a virus is an indicator of an active infection. Latent viruses hide within cells and not in body fluids such as saliva and nasal secretions. The researchers plan to continue their research by distinguishing between the active viral infections not causing symptoms or illness and the active viruses that are.