Mittwoch, 9. März 2016

Scientists are using human embryonic stem cells to provide evidence that Zika virus causes microcephaly


Dr. Edith Breburda

published in : FIAMC March 9, 2016
Scientists from Uganda were the first ones who isolated the Zika virus.  In April 1947 rhesus monkey 766 was part of a Yellow Fever study.  He lived in a cage near the little Zika Forest in Uganda.  However, instead of harvesting yellow fever from the animal and the trapped mosquitoes, scientists isolated a new kind of a “hitherto unrecorded virus,”which they named “Zika.”  For a long time the new member of the Flaviviridae family did not cause any serious complications.
In 1952, researchers from the Uganda Virus Research Institute in Entebbe started with more exhaustive studies, and inserted the virus in numerous monkeys, cotton rats, mice, guinea pigs and rabbits.  The Zika virus caused damage to the neurons only in mice.  No other evidence of a disease was shown.  One of the 24 papers, published in the following 30 years concluded: “The absence of recognition in humans, of a disease caused by Zika virus does not necessarily mean that the disease is either rare or unimportant.”
In 1964 David Simpson, a student of Zika co-discoverer George Dick, reported that he became ill when working with Zika strains isolated from mosquitos at the Entebbe lab that discovered the virus.  Simpson described his symptoms as “mild”. He wrote: “If this was a typical infection with Zika virus it is not surprising that under normal circumstance the virus is not isolated frequently from man.”
1973 C. Martins described the symptoms of another Zika infection in the Journal Archive. “The lab technician worked with the Portugal’s Institute of Hygiene and Tropical Medicine in Mozambique, when he developed fever accompanied with some pain in his joints.  He recovered completely after one week.” 
In the 70’s and 80’s, Zika antibodies where found in wild monkeys in Nigeria and Indonesia.  Documented cases of infected people remained scarce, until the New England Journal of Medicine reported 49 confirmed, and 59 probable, Zika cases in 2009.
The outbreak of the disease occurred two years earlier at Yap Island.  No one was hospitalized or died.  surprisingly no mosquitos with the virus were found.
Since then, Zika infections began to increase. In the US, one traveler infected his wife, presumably through sex.  Before Zika swept across the Caribbean and through Latin America, it had been recorded in French Polynesia in 2013.  In 19,000 suspected cases, 333 had been confirmed.  For the first time did the symptoms include neurological disorders (1).
Zika could cause congenital infections and microcephaly. so far, though, we have not seen numerous headlines reporting that people who encounter the virus can become temporarily paralyzed.
On Monday, March 7 2016, The Lancet medical journal provided evidence that the virus can also cause people to become temporarily immobile.  This was the first report of a possible link between the Zika virus and Guillain-Barré syndrome.  This condition, that contributed to several kinds of infections, was first described 1916 by French doctors Georges Guillain and Jean-Alexandre Barré.
Guillain-Barré syndrome develops when the body’s immune response to an infection attacks its own nervous system.  “It is an autoimmune attack that happens when part of a virus resembles part of human cell,” explained Hugh Willison, who studies the disease at the University in Glasgow in Scotland. He continued: “Like other viruses, the one that causes Zika hijacks a cell’s own replication machinery to make new copies of itself, which then break out of the dying cell and infect neighboring cells.”
Doctors treat such patients with a mix of antibodies made from healthy donors, or a plasma exchange is used, in which the body’s red cells are separated from the immune-cell-carrying plasma, and then returned to the body (2).
For researchers, the question remains how Zika-virus is causing such damage to the unborn.  Previously done scant research has resulted in few insights. It remains difficult to prove a link between the virus and the defects, because blood tests for Zika are only accurate for the first week after the infection.
Researchers at John Hopkins University in Baltimore, Maryland, and Florida State University in Tallahassee, conducted experiments to determine the virus’ possible effects on the developing brain.  Because the access to fetal human brain tissue is limited, induced pluripotent stem cells (iPS), (harvested adult cells that have been reprogrammed) have been deployed as an in-vitro model.  For control purposes, Zika was exposed to human embryonic stem cells, (obtained by the destruction of embryos)/(3).
The neuroscientists Dr. Hongjun Song and Guo-li Ming, and the virologist Hengli Tang, reported in a Cell Stem-Cell article, from March 2016, that 85% of the neuronal and immature brain cells cultures had been infected after three days; only 10% of fatal kidney cells, human embryonic stem cells, and undifferentiated iPS cells were infiltrated by the virus.
The two independent studies showed that the virus also “took the cells over.”
“The infected cells had not been killed right away.  Instead, the virus “hijacked the cells,” using the cellular machinery to replicate themselves.  The infected cells grew more slowly through cell population and interrupted cell division cycles, which could also contribute to microcephaly.  We still need to figure out how the virus crosses the placenta and infects the fetuses directly, something most viruses can’t do”, says Dr. Song.  He continued: “Plenty of questions about Zika virus and its apparent link to birth defects remain unanswered.”  The team will repeat its study with other flavi-viruses (4).
The first Zika studies where conducted with monkeys, cotton rats, mice, guinea pigs and rabbits.  The recently diseased First Lady Nancy Reagan was in favor of human embryonic stem cell research.  We might remember Nancy’s words in 2004.  It was before the President’s death when she said: “Ronnie’s long journey has finally taken him to a distant place where I can no longer reach him.  Because of this, I’m determined to do whatever I can to save other families from his pain.”
Many Republicans have been scandalized, when the beloved first Lady campaigned for broader human embryonic stem cell research in order to discover a cure for Alzheimer’s.  So far, the death of many unborn babies has not resulted in any remedy.
While Human Rights Commissioner’s call for abortion, and want to change the laws in developing countries with disabled unborn that show the sign of microcephaly, bishops explain that you cannot treat Zika virus infections by killing human beings.  The Holy See states that children with birth defects are to be protected and cared for throughout their lives, in accordance with our obligation to safeguard all human life, healthy and disabled, with equal commitment (5).

1) Cohen J.: Zika’s long, strange trip into the limelight. Science, February 8, 2016
2) Vogel G and McLaughlin K.: Why does Zika leave some patient paralyzed?  Science, March 3,  2016
3) Hengli Tang et al:. Zika Virus infects human cortical neural progenitors and attenuates their growth. Cell Stem Cell, in Press corrected proof, available online, March 4, 2016
4) Vogel G.: Zika virus kills developing brain cells. Science, March 4, 2016.
5) Wright W.: UN Human Rights Chief Scolded for denying rights to disabled Babies. C-Fam, Center for Family and Human Rights, February 18, 2016
Please see also: E. Breburda: Reproduktive Freiheit, free for what? 2015, ISBN-10: 0692447261, ISBN-13: 978-0692447260 / kindle e-book.

Keine Kommentare:

Kommentar veröffentlichen

Translate