A virus that infects pigs in China appears in humans in Brazil

A virus that infects the Ascaris suum worm in the intestine of pigs in China has been discovered in Brazil. It has been discovered in the feces of a child with gastroenteritis and has been described by scientists from various Brazilian and American institutions. An article about it has been published in the journal Virus Genes.

This research does not allow us to conclude that the virus in question – called WLPRV / human / BRA / TO-34/201 – arrived in Brazil from China with a person who ate infected pork. Or that this virus has been the cause of gastroenteritis.

"We analyzed a stool sample of a child with diarrhea whose pathogen had not been identified and we discovered a virus that had only been sequenced for the first time. only once in China, but it is too early to say that the virus has arrived in Brazil from China, and as we have described, it is possible – and it is very likely – that with the time, it is also found in other places, and maybe it will establish a propagation sequence, but for the moment, we do not know if the virus came from China. what we have are two similar genomic sequences, "said study coordinator Ester Cerdeira Sabino, director of the Institute of Tropical Medicine (IMT) in São Paulo, Brazil, and a professor. at the Department of Infectious Diseases of the Faculty of Medicine of the University of São Paulo.

This study was funded by FAPESP under the projects entitled "Study of the evolution of animal strains of rotavirus infecting humans" and "Viral metagenomics of Dengue, Chikungunya and Zika: follow, explain and predict spatio-temporal transmission and distribution in Brazil ".

According to Antonio Charlys da Costa, a postdoctoral researcher, there is a huge amount of active viruses in the world that have not yet been described.

Pig farm (Photo: UCM)

"Given the number of eukaryotic organisms present on Earth, the number of viruses to be described is estimated at about 87. Currently, the International Committee on Viral Taxonomy (ICTV) recognizes 4,404 species of viruses in eukaryotes. which means that more than 99.99% of the viruses are still unknown or have not been classified.Although this is only an estimate, we think that this percentage is valid because of the great viral diversity that we found in the sequenced samples so far, "said Da Costa, IMT's postdoctoral fellow with a grant from FAPESP.

One of Da Costa's approaches to research is to identify and sequence viruses not yet described. The epidemiological study – which includes the distribution of viruses, frequency of occurrence in the population, associated diseases, etc. – is a little later.

"What we did was to investigate human faeces samples taken during episodes of gastroenteritis whose pathogens had not been identified." We found countless agents present and We now describe these results.The methodology used is viral metagenomics, which allows the identification of any infectious agent.This does not mean that the found agents are responsible for gastroenteritis, but this mapping allows us to establish a correlation with the goal of future studies, "explained Cerdeira Sabino.

The viruses being investigated, several steps must be taken during the investigation. The first step is to filter the sample at the micrometric scale in order to block and reject cells, parasites, fungi and bacteria.

Nevertheless, fragments of DNA and free RNA manage to pass through the filter. And you have to eliminate them. For this, we use nucleases, which are enzymes that digest DNA and RNA. The nucleic acid of the virus (DNA or RNA) is not digested because it is protected inside the viral capsid. But the free nucleic acid is. After all this, the viral particle undergoes the process of cellular lysis, destruction or dissolution of the cell caused by rupture of the plasma membrane. Finally, the genetic material is released and sequenced.

"This produces billions of small sequences that must be aligned to try to reconstruct the viral genomes.Once the major sequences obtained, the next step is to look, through bioinformatics, for something similar in the database, which generally requires a lot of processing time and computing power.We sequence all the possible viruses in the samples.And then we try to see if the sequences obtained coincide with those of known viruses ", said Cerdeira Sabino.

According to the authors of the research, rotavirus was the main viral agent of diarrhea in Brazil. But since rotavirus disease has become preventable by vaccination, it is possible that other viral agents may be the cause of gastroenteritis.

Cerdeira Sabino comments that it may happen that two non-pathogenic viruses produce a pathogenic virus by recombination, for example. During recombination, a fragment of virus joins a fragment of another virus to form a third.

"We do not know the etiology of many human diseases.As for diarrhea, for example, the cause is unknown in more than 50% of cases.This is why many agents must be discovered. Before we could go looking for these agents, it was very difficult and expensive to sequence them, but with the next-generation sequencer it became easy, but there is a big distance between finding an agent and proving that's the cause of the disease, "said the researcher.

Adriana Luchs, Elcio de Souza Leal, Shirley Vasconcelos Komninakis, Flavio Augusto of Padua Milagres, Rafael Brustulin, Maria of Aparecida Rodrigues Teles, Danielle Elise Gill, Xutao Deng and Eric Delwart also participated in the preparation of the event. article. (Source: AGENCIA FAPESP / DICYT)