ALL ABOUT ZIKA VIRUS
Zika virus is a mosquito bourne flavivirus transmitted primarily by day time active Aedes mousquitos Family Flaviviridae, first identified in Uganda in 1947 in monkeys through a yellow fever later identified in humans in 1952 in Uganda and the United Republic of Tanzania . outbreaks of Zika virus disease have been recorded in Asia ,Africa America and Pacific.human infections were found across Asia and Africa with mild mild weekness during 1960s to 1980s. The first large outbreak of disease caused by Zika infection was reported from the Island of Yap (Federated States of Micronesia) in 2007. In July 2015 Brazil reported an association between Zika virus infection and Guillain-Barré syndrome. In October 2015 Brazil reported an association between Zika virus infection and microcephaly.
Signs and Symptoms:
Most individuals infected with Zika virus experience mild or no symptoms. About 25% of infected people develop symptoms 2-10 days after infection, including rash, fever, joint pain, red eyes, and headache. Recovery is usually complete and fatalities are rare.
Two conditions associated with Zika virus infection have made the outbreak potentially more serious. The first is development of Guillain-Barré syndrome, which is progressive muscle weakness due to damage of the peripheral nervous system. The association of Guillain-Barré was first noted in French Polynesia during a 2013 outbreak.
Congenital microcephaly has been associated with Zika virus infection in Brazil. Given the serious nature of Guillain-Barré and microcephaly, it is prudent for pregnant women to either avoid travel to areas that are endemic for Zika virus infection, or to take measures to reduce exposure to mosquitoes.
Zika virus is a member of the flavivirus family, which also includes yellow fever virus, dengue virus, Japanese encephalitis virus, and West Nile virus. The genome is a ~10.8 kilobase, positive strand RNA enclosed in a capsid and surrounded by a membrane (illustrated; image copyright ASM Press, 2015). The envelope (E) glycoprotein, embedded in the membrane, allows attachment of the virus particle to the host cell receptor to initiate infection. As for other flaviviruses, antibodies against the E glycoprotein are likely important for protection against infection.
Zika Virus maturation:
Before an immature Zika virus becomes infectious, it does some major remodeling.In a fledgling virus particle, the inner protein and RNA core forms bridges to the membrane layer that surrounds it. As the virus matures, the core shuffles around and the bridges melt away .
It’s the first time scientists have seen such rearrangement in the core of a flavivirus, the group that also includes the viruses that cause dengue, West Nile and yellow fever, says virologist Richard Kuhn of Purdue University in West Lafayette, Ind.
Scientists don’t know why the immature Zika virus reshuffles its insides, Kuhn says — perhaps it helps the maturing virus become infectious. But that’s the next big question to answer, he says.
If blocking the reorganization somehow made mature viruses harmless, scientists would have a new clue about preventing Zika infection. Kuhn and colleagues’ map of the immature virus’s structure , published online January 9 in Nature Structural & Molecular Biology, could offer other hints for thwarting Zika.
With a technique called cryo-electron microscopy, the team could see three-headed protein spikes (shown in red) studding the surface like some kind of medieval weapon, and could even distinguish the separate layers of the membrane (aqua) that encloses the core. (The maps are radially colored; colors change as distance from the core increases.) Outside the membrane lie surface proteins called envelope, or E, proteins (green and yellow) that help the virus sneak into cells.
Last year, Kuhn’s team reported the structure of the mature Zika virus .
Link between infection with the virus during pregnancy and infant microcephaly:
When the Zika virus enters neural stem cells, a protein called Musashi-1 (MSI1) latches on to the virus’s RNA genome, somehow promoting viral replication. Blocking the cells’ ability to produce MSI1 significantly inhibits Zika’s ability to reproduce, according to an in vitro study published today in Science.
The interaction between the virus and the human protein appears to make the neural stem cells more vulnerable to cell death. Moreover, by binding to the Zika genome, MSI1 was less likely to bind its natural targets within the neural stem cells to properly direct brain development, as evidenced by differences in the cells’ gene expression.
The results provide clues as to how Zika causes microcephaly in fetuses whose mothers were infected while pregnant. Indeed, the team also found that a rare type of inherited microcephaly called autosomal recessive primary microcephaly is associated with mutations in MSI1.
“We’ve shown for the first time this interaction between Zika and MSI1—with MSI1 getting exploited by the virus for its own destructive life cycle, turning MSI1 into the enemy within,” coauthor Fanni Gergely from the University of Cambridge says in a press release .
“This is the first study to show a clear link between a specific protein, the Zika virus, and microcephaly,” adds Mike Turner, head of Infection and Immunobiology at the Wellcome Trust, which partly funded the study. “This new finding really helps to explain why neural stem cells are so vulnerable to Zika infection and I hope this can be a first step in determining how we could stop this interaction and disease.”
There are currently no antiviral drugs or vaccines that can be used to treat or prevent infection with Zika virus. We do have a safe and effective vaccine against another flavivirus, yellow fever virus. Substituting the gene encoding the yellow fever E glycoprotein with that from Zika virus might be a good approach to quickly making a Zika vaccine. However testing of such a vaccine candidate might require several years.
Mosquito control is the only option for restricting Zika virus infection. Measures such as wearing clothes that cover much of the body, sleeping under a bed net, and making sure that breeding sites for mosquitoes (standing water in pots and used tires) are eliminated are examples. Reducing mosquito populations with insecticides may also help to reduce the risk of infection.
Ms Neha Ravindra Sakdeo,
Yadavrao Tasgaonkar College of Pharmacy,
Final year B.Pharmacy