A single genetic mutation contributes to the appearance of microcephaly and the increased lethality of the virus.
The study published in Science provides a first explanation as to why modern Zika strains cause a smaller head size than thousands of newborns.
Zika was the last illness described by the World Health Organization as a “health emergency”. No wonder: Between 2013 and 2016, when the virus began to wreak havoc in French Polynesia and arrived in America, thousands of cases of a disease were detected that usually occurred with mild symptoms such as fever, muscle aches or headaches.
But the really serious signs appeared in newborns, whose mothers had been infected during pregnancy. The children came to the world with a head much smaller than normal, a problem called microcephaly, in addition to suffering in many cases a neurological disorder known as Guillain-Barré syndrome.
Zika was known since the 1950s, and it was only between 1950 and 1981 that the virus was capable of attacking humans. However, studies in Asia and several African countries pointed out that the virus was “harmless”. Years later, when the zika hit the American continent, especially Brazil and Colombia, the researchers saw that the virus was far more dangerous than it appeared to cause devastating consequences on the nervous system. A study published today in the journal Science explores for the first time why the Zika became so dangerous.
A single change in your genetic material
Research to date has failed to determine how zika went from being a mild disease to becoming a real public health problem. The team of scientists from the United States and China decided to compare current strains of the virus, involved in the American epidemics of 2015 and 2016, with a virus that circulated in Cambodia in 2010. Their analysis has revealed the existence of a “critical mutation” that contributed to the ability of the Zika to produce a significant reduction in the diameter of the heads of the newborns.
According to their results, a variation in the genetic material of the virus produced a change in a protein that is part of the protective envelope of the pathogen. In particular, the modification caused the replacement of one of the components of said protein – the amino acid serine by an arginine – at position 139. The group led by Cheng Feng Qin explains in his study in Science that the substitution “increases significantly the infectivity of Zika “in the experiments performed.
Since the virus accumulated numerous changes between 2010 and 2016, the researchers also checked the degree of lethality of the different mutations. His work determined that the observed change in genetic material caused microcephaly and embryonic lethality much more severe in mouse models. In addition, according to their findings, the critical mutation would have appeared in May 2013, months before the outbreak appeared in French Polynesia, and was subsequently maintained in the strain that attacked the American continent.
Finally, the team of Cheng Feng Qin performed a modeling of the virus comparing the Zika with dengue. The objective was to analyze both structures in order to understand what function could be the prM protein, affected by the critical mutation. According to the first results, the change in the genetic material of the virus could directly affect the maturation, exit and secretion of new viral particles. The researchers suggest that such variation would be related to a modification of Zika’s ‘capabilities’, contributing to his neurovirulence.
Sources consulted by Hipertextual explain that the work predicts “the most probable time in which the phenotype change occurred and coincides with the appearance of that mutation at that time according to the phylogeny.” The results presented in Science do not imply that there is a single genetic change that produces harmful effects in newborns, but they offer a hypothesis about how the more modern virus strains increase the probability of microcephaly. According to the authors, the work shows “an explanation for the unexpected causal relationship between zika and microcephaly,” in addition to helping to understand how a simple apparently innocuous virus,