New Delhi: The Zika virus can become even more dangerous with a small mutation, a new study has found. The mutation will make it more infective, as a result of which it may break through pre-existing immunity.
The study describing the findings was recently published in the journal Cell Reports.
What Is Zika Virus Disease?
Zika virus disease is caused by a virus transmitted primarily by Aedes mosquitoes. The symptoms of Zika virus disease are usually mild and include fever, rash, conjunctivitis, muscle and joint pain, and headache, among others.
The virus was first identified in Uganda in 1947 in monkeys, and was later identified in humans in 1952 in Uganda and the United Republic of Tanzania.
According to the World Health Organization (WHO), Zika virus infection during pregnancy can cause infants to be born with microcephaly, which is a condition wherein a baby's head is much smaller than expected. The infants may also be born with other congenital malformations.
In many countries, the Zika virus and dengue virus overlap. Both Zika and dengue viruses are mosquito-borne flaviviruses. These are positive-strand RNA viruses known for their ability to infect humans through various arthropod vectors. Flaviviruses are known to cause widespread morbidity (consequences and complications, other than death, that result from a disease) and mortality throughout the world.
Similarities Between Zika And Dengue Viruses
Zika and dengue viruses share many biological properties, and are similar enough that the immune response sparked by prior dengue exposure can confer protection against Zika.
Sujan Shresta, a professor at La Jolla Institute for Immunology (LJI) in California, who co-led the study with Professor Pei-Yong Shi from the University of Texas Medical Branch, said that the world should monitor the emergence of this Zika virus variant, according to a statement issued by LJI.
She also said that a vast majority of people have already been exposed to the dengue virus, in areas where Zika is prevalent. They have both T cells and antibodies that cross-react.
However, an unfortunate aspect is that both the viruses are quick to mutate. Shresta explained that dengue and Zika are RNA viruses, which means they can change their genome.
The viruses are constantly moving back and forth and evolving since there are so many mosquitoes and so many human hosts.
How Did The Team Study Zika’s Evolution?
The researchers recreated infection cycles that repeatedly switched back and forth between mosquito cells and mice, in order to study Zika's fast-paced evolution. As a result, the researchers obtained clues about how Zika virus naturally evolves as it encounters more hosts.
The Zika virus finds it relatively easy to acquire a single amino acid change that allows the virus to make more copies of itself, according to the study. As a result, infections can occur more easily.
How Is The Zika Variant Harmful?
The mutation is called NS2B I39V/I39T mutation. It increases the Zika virus's ability to replicate in both mice and mosquitoes. The Zika variant also showed increased replication in human cells, the study found.
Jose Angel Regla-Nava, the first author of the study, said that this single mutation is sufficient to enhance Zika virus virulence. He explained that a high replication rate in either a mosquito or human host could increase viral transmission or pathogenicity, and cause an outbreak.
Shresta further said that the Zika variant that the team identified had evolved to the point where the cross-protective immunity afforded by prior dengue infection was no longer effective in mice. She said if the variant becomes prevalent for humans, they will have the same issues in real life.
How Can Humans Prepare For This Kind Of Variant?
The scientists are trying to figure out ways to tailor Zika vaccines and treatments that counteract the dangerous mutation, and are trying to understand how exactly the mutation helps Zika replicate more efficiently.
The researchers want to understand at what point in the viral life cycle the mutation makes a difference.