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New scientific classification will help to better understand the EBV virus

The Epstein-Barr virus (EBV), also known as human herpesvirus 4, is one of the most effective viruses in evolving, surviving and spreading in the world population. This virus is responsible for various diseases, such as, infectious mononucleosis, Hodgkin lymphoma, Burkitt lymphoma, nasopharyngeal cancer, and lately it has been linked to gastric cancer, which is very common in Chile. Researchers from Universidad Autónoma de Chile in Temuco and Universidad de la Frontera published a study in Scientific Reports – Nature journal, where they analyzed 188 genomes (set of genes) of EBV based on samples obtained from patients between 1970 and 2017. The authors propose a new classification that allows to better understand the evolution and geographical origin of the virus, as well as it will help to understand its biology and how it avoids the immune system in the host cell and triggers several related diseases.

  
María Paz Ilabaca
By María Paz Ilabaca
Periodista Científica

7, August 2019

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Dr. Ismael Riquelme, researcher at the Universidad Autónoma de Chile and one author of the article says: "Defining which virus subtypes relate to certain diseases will allow us to move forward in treatment development, diagnostic tools and make epidemiological surveillance more effective. Overcoming the classic classification of EBV will allow an in-depth understanding of how the different virus subtypes relate to several diseases,”

EBV is one of the most widely spread viruses in the world and affects over 90% of the human population, playing a key role in the origin and progression of some diseases. People infected with the virus commonly acquire it during childhood and keep it for life without adverse health consequences. However, people infected for the first time during or after adolescence have at least a 50% chance of contracting infectious mononucleosis, whose symptoms are like those of a common cold, flu or pharyngitis.

Sometimes, EBV can stimulate cell proliferation and act as a biological type carcinogen. There is an estimate of over 200,000 cases of cancer diagnosed annually (over 1% of human cancers worldwide) and around 150,000 cancer-related deaths are attributable to EBV. The virus could even increase the risk of developing other diseases such as multiple sclerosis, lupus, or type 1 diabetes. Unfortunately, so far there is no cure or vaccine to eradicate it. "Viruses evolve quickly, they have a high variability and heterogeneity in their genome, this often makes both their classification and the possibility to infer the relationship between subtypes or viral variants and associated diseases difficult", Dr. Ismael Riquelme says.

The new sequencing technologies have allowed increasing the number of genomes of EBV which are completely sequenced, coming from both different geographical regions and pathologies. With this information, the authors of the article have established a new phylogenetic classification or evolutionary relationship between different strains of EBV that is more reliable

The new classification presented by the researchers at Universidad Autónoma de Chile and Universidad de la Frontera will allow to improve the research of the biogeographic components related to different EBV infections types and human diseases related to it. According to Riquelme the new classification "Could also be useful for a new diagnostic application development or to define which strains need epidemiological surveillance. For example, gastric cancer is the leading cause of death linked with malignant tumors in Chile, around 20% of these cases are related an EBV infection. As it happened with the human papillomavirus (HPV), where the development of the vaccine used nowadays to prevent this type of cancer was possible when scientist were able to the determined that variants 16 and 18 were the subtypes most associated with cervical cancer, by studying more cases of gastric cancer and relating them to some of the 12 subtypes of EBV found in our research, we could define which of the variants is the underlying cause of the cancer."

In deep…
Genetic variation


EBV is generally classified into two major strains, type 1 and 2, based on differences between small groups of viral genes; However, the study presented in Scientific Report - Nature analyzes the whole virus genome, identifying mutations and describing multiple processes of recombination in viral DNA. Genetic variation can occur by two mechanisms, a spontaneously random mutation, a change in the DNA or RNA sequence, or through recombination, when two different viruses infect the same cell at the same time and exchange pieces of their genetic material (DNA or RNA). The authors of the article determined that recombination events occur 2.5 times more often than mutation events, suggesting that recombination has a much stronger impact than mutation on EBV genomic diversity.

María Paz Ilabaca
By María Paz Ilabaca
Periodista Científica

7, August 2019