The genetic sequence of a virus that caused the morbidity and mortality of tilapia fish is not similar to any known genetic sequence
Viruses are built from an accumulation of biological molecules that include hereditary material (DNA or RNA) and proteins; And they need a host cell (human or animal) to reproduce. Once they enter the cell, they multiply and can cause disease. RNA viruses are characterized by genetic material that is more diverse in its forms. These viruses are genetically less stable and tend to mutate more rapidly, which dictates different culture, spread and coping strategies. For example, the genome of the influenza virus contains eight segments and its strains can swap between them and create new variants relatively quickly.
Prof. Eran Bacharach from the Faculty of Life Sciences at Tel Aviv University and his team research RNA viruses and focus on viruses that cause diseases, mainly in the respiratory tract (such as influenza). Among other things, they examine their culture methods and their genome packaging in particles, along with proteins and fats; their interaction with the host cell for the purpose of culture (such as binding to its proteins); and the way in which they cause the immune system to activate - against them.
A few years ago, tilapia fish in the Sea of Galilee and in fish ponds in the north of the country began to get sick and die en masse. Dr. Avi Elder, director of the fish section and the laboratory for viral diagnostics at the Ministry of Agriculture, suspected that the source of this is a viral infection. He turned to Prof. Bacharach and together they decided to solve the mystery; They analyzed diseased tilapia fish (for example those with eye damage and encephalitis) and dead fish, isolated brain tissue from them, placed them with other fish cells in culture - and looked for signs of cell death. This is because when a virus infects cells, both in culture and in the body, it kills them. Indeed, the researchers found that many cells in the cultures became infected with the virus and died. They realized that it was a new virus that harms tilapia fish (and called it Tilapia Lake Virus and abbreviated TiLV). In the first step, they grew the virus in cultures, injected it into new fish - and these too got sick and died. Thus they proved that TiLV is indeed the factor that harms tilapia fish.
In their latest study, which won a grant from the National Science Foundation, the researchers sent material samples for deep genetic sequencing of pathogens (causing diseases). When the sequence was obtained, it turned out that it did not resemble any known RNA sequence, viral or cellular. This, in contrast to most of the new viruses that are discovered, which genetically can belong to known virus families. However, the new virus had similarities to the influenza virus, for example a genome that consists of many segments (but ten and not eight).
Following the discovery of the unique genetic sequence of the virus, the researchers tried to find out more information about it, for example how it penetrates the cell, what its proteins are (each of the genome segments contains a single gene that, according to the stored information, produces a protein), and what their role is in its reproduction. For example, they were able to identify the protein that binds to the genetic sequence of the virus (nucleoprotein), which is essential for its reproduction. It is possible that in the future they will be able to develop molecules that will bind to this protein and in this way stop the culture of the virus. These molecules could also help in the rapid identification of fish infected with the virus.
Prof. Bacharach: "It is important to regularly monitor and check which viruses are in our environment and how they work, even if they do not seem capable of infecting humans. It is possible, for example, that in the future another virus from their family will be discovered that attacks humans - then we will know how to deal with it faster. From a practical point of view, tilapia fish farming is the second largest in the world fish industry. Thus, as soon as we determined the genetic sequence of the virus that affects them and published it, it was possible to discover it in many parts of the world and reduce its spread. Following this, a diagnostic test was developed that allows it to be identified in schools of fish and prevent them from reaching ponds with healthy fish. It turned out that the virus caused a widespread epidemic in tilapia fish in many countries, mainly developing ones, thus damaging the protein supply of many populations. Following the study, the UN issued a warning that the virus could harm the food security of millions of people in the world."
Life itself:
Prof. Eran Bacharach, 58 years old, married with two daughters (30 and 27), lives in Tel Aviv, and likes to row kayaks in the sea.
