The story of how a Chilean scientist managed to clone an avian virus

There Avian infectious laryngotracheitis (ILT) is one of the deadliest poultry diseases. He has 100% morbidity that is, all birds in a building exposed to the virus that produces it become ill, and between 30 and 70% of sick birds die depending on the degree of virulence of the virus and the immune response generated by the host.

The disease has catastrophic consequences for the poultry industry. Signs seen in sick birds include decreased egg production, sneezing, conjunctivitis, dyspnea (difficulty breathing), and bloody productive cough in more severe cases .

Therefore, any discovery on this virus is highly appreciated. And that is precisely what Dr. Carlos Loncoman, an academic at the University Faculty of Sciences of the Austral University of Chile (UACh) , who succeeded in genetically cloning the virus responsible for infectious laryngotracheitis in poultry.

Loncoman participated in an investigation published in an international magazine Journal of Virology , in which the results obtained after the cloning process are explained. According to research, the reconstituted viruses were able to cause clinical disease in laboratory animals, similar to what is seen in birds naturally infected with field virus (uncloned virus), demonstrating that the reconstituted viruses fully recover their ability to cause disease.

In this context, the study conducted opens the door to the development of vaccines with higher standards of safety and efficacy also allowing a better understanding of the function of each of the genes present in the viral genome, favoring the development of vaccines.

In the study, Three viruses were reconstituted in chicken kidney cells, similar to the ILT reference strain in a cloning system known as cosmid/yeast centromeric plasmid (YCp). . Subsequently, a viable virus was reconstituted, which means that this platform can be used to develop new, safer vaccines against this disease.

The interesting thing about the research is that previous attempts to clone the full genome of the virus were unsuccessful. . “Previously, bacterial artificial chromosomes were used to clone this virus, and once the genome was cloned in this system, the viral genome became unstable and it was not possible to reconstitute the viable virus after its cloning”, explains the scientist.

Not in vain it took more than a decade . “This survey is the result of several years of work in which I have been participating for eight years. However, the project has been around for years and includes researchers from the United States, Australia, Europe, Asia and Latin America,” he explains.

The size of a genome to clone it is an important factor, the larger it is, the more complex it is. “THE herpes virus they have a genome considered “large” of about 150,000 base pairs of double-stranded DNA. Once a viral genome is cloned, the most relevant thing is to be able to reconstitute the virus, that is to say to recover it completely. , as well as its ability to replicate, which causes cytopathic effect in vitro (cell damage) and disease in its host in vivo. This last part is essential to determine that the cloning system is working properly,” says Loncoman.

Loncoman explains that althoughIt is possible that, like avian flu, this virus can be transmitted to humans, there is no proof that they took place. “However, this virus belongs to the taxonomic classification of the subfamily Alphaherpesvirinae, which includes viruses that affect people, such as those that cause oral or labial herpes, genital herpes and herpes. Shingles (varicella). Viruses that belong to this group are considered host-specific, that is, they are viruses that have co-evolved with their hosts to have a stable, predictable, and stable virus-host relationship. specific.

“The vaccines that currently exist and are marketed around the world, including in Chile, are mainly live attenuated vaccines that contain the complete virus and have the disadvantage of reversing its virulence. That is, once the vaccine is applied to an animal, the virus in the vaccine replicates and spreads to other unvaccinated chickens causing the disease. These reversal events have been a problem and with this new cloning platform, new strategies could be evaluated to produce new, safer vaccines capable of generating an immune response, but not reversing.

In the United States, there are vectorized vaccines. These vaccines are made with pieces of the virus that causes ILT. . However, these vaccines do not offer the same degree of protection against the disease. It is therefore essential to identify the role of each of the genes present in the virus genome and to precisely determine their role in the host’s immune response and in the infectious cycle.

Infectious laryngotracheitis is a disease which is currently widespread throughout the world, and in Chile its notification is mandatory.

Although our country is characterized by the sale of vaccines produced in the United States and Europe, these are not considered safe since the virus for these vaccines has been detected in backyard birds from small producers who had never been inoculated.

“Similarly, other UACh researchers have detected the presence of the genetic material of this virus in wild birds. This evidence allows us to take preventive measures and of course to contribute to the development of safer vaccines for veterinary use. whether or not they have an economic impact on the animal sector”, underlines the academic.