Viruses:a major driver of human evolution

"The constant battle between pathogens and their hosts has long been recognized as a key driver of evolution, but until now scientists have not had the tools to look at these patterns globally across species and genomes. In a new study, researchers apply big-data analysis to reveal the full extent of viruses' impact on the evolution of humans and other mammals.

Their findings suggest an astonishing 30 percent of all protein adaptations since humans' divergence with chimpanzees have been driven by viruses.

"When you have a pandemic or an epidemic at some point in evolution, the population that is targeted by the virus either adapts, or goes extinct. We knew that, but what really surprised us is the strength and clarity of the pattern we found," said David Enard, Ph.D., a postdoctoral fellow at Stanford University and the study's first author. "This is the first time that viruses have been shown to have such a strong impact on adaptation."

The study was recently published in the journal eLife and will be presented at The Allied Genetics Conference, a meeting hosted by the Genetics Society of America, on July 14.

Proteins perform a vast array of functions that keep our cells ticking. By revealing how small tweaks in protein shape and composition have helped humans and other mammals respond to viruses, the study could help researchers find new therapeutic leads against today's viral threats..."

Learn more:

http://phys.org/news/2016-07-viruses-revealed-major-driver-human.html

Obscure virus found in women with unexplained infertility

via wikipedia

Source: HHV-6 Foundation | Summary: The little-known member of the human herpesvirus family called HHV-6A infects the lining of the uterus in 43 percent of women with unexplained infertility but cannot be found in that of fertile women, researchers have discovered. The study also reported that the infection is exacerbated by hormone estradiol. Estradiol fluctuates with the menstrual cycle. High levels may trigger an active infection localized in the uterus.

"A new study has found that the little-known member of the human herpesvirus family called HHV-6A infects the lining of the uterus in 43% of women with unexplained infertility but cannot be found in uterine lining of fertile women. The study was conducted by investigators at the University of Ferrara, Italy.

The study also found that the response of the immune system to the virus may contribute to making the uterus less hospitable to a fertilized egg. The virus seems to activate immune cells called natural killer cells in the uterus, and lead those cells to produce chemicals called cytokines. Cytokines are tools the immune system uses to orchestrate an attack on a foreign invader, like a virus. However, the activated immune system cells and abnormal levels of certain cytokines may make it harder for a fertilized egg to lodge in the uterus, and grow into a baby.

Infertility affects approximately 6% of 15-44 year old women or 1.5 million women in the US, according to the CDC. Approximately 25% of female infertility cases are unexplained, leaving women with few options other than expensive fertility treatments. "This is a surprising and potentially important discovery," said Anthony Komaroff, a professor at Harvard Medical School who has studied HHV-6. "If confirmed, the finding may lead to treatments that improve the outcome for a large subset of infertile women."

Little is known about HHV-6A, which was discovered in 1986 and is one of nine human herpesviruses. Others include Epstein Barr virus, varicella-zoster virus, cytomegalovirus, and herpes simplex types 1 and 2. Since HHV-6A is typically not detectable in the blood or saliva, its true prevalence is unknown. A closely related virus, HHV6-B, is acquired by nearly 100% of the population in early childhood and is spread through exposure to saliva..."

Learn more:

https://www.sciencedaily.com/releases/2016/07/160707100736.htm

Viruses For Healthy Pregnancy?

via hubpages.com

"Sequences of DNA in the human genome that originated from ancient viral infections have some surprising effects on our bodies and are even essential for a healthy pregnancy, according to an article in the February issue of Microbiology Today.

Retrovirus infections represent the most intimate host-pathogen relationship. The virus inserts a copy of its genome into the DNA of the host cell, resulting in an irreversible, stable and sometimes lifelong infection. If a sperm or egg cell is infected, the virus DNA can be passed down generations, permanently fixed in the germ line. As a result, an endogenous retrovirus (ERV) can exist for millions of years.

“Over the course of evolution, retroviruses have invaded the germ-line of our ancestors on numerous occasions. Now, human ERVs (HERVs) make up around 8% of our genome,” say Dr David Griffiths from the Moredun Research Institute and Cécile Voisset from the Faculté de Médecine et des Sciences de la Santé in France.

Although there are no viruses similar to these ancient pathogens currently infecting humans, there are some related viruses in animals. For a retrovirus to become part of the host genome it is usually inactivated by mutation or silencing so it does not express any proteins. An epidemic of neoplastic disease in Australian koalas is giving researchers the rare opportunity to study this process..."

Read more here:

http://phys.org/news/2008-01-viruses-healthy-pregnancy.html