The pandemic caused by the SARS-CoV-2 coronavirus that emerged in December 2019 has managed to focus on the development and use of vaccines. The undeniable success and beneficial effect of coronavirus vaccines has brought about a change in the pandemic in some countries. However, vaccines have a series of disadvantages, either due to the mechanism or the logistics involved in making them accessible to all parts of the planet. This is one of the reasons why, along with the development of vaccines, the use of antiviral treatments is being considered to control cases of COVID-19.
What happens when a virus infects our body?
When the coronavirus, or any virus capable of infecting humans, enters our body from the outside, a series of events takes place that allow it to lodge inside our cells to use our functioning machinery to reproduce. These processes may be somewhat different depending on the type of virus, but in general, the virus inserts its instruction manual (genetic material) into our cells and borrows structures that are responsible for multiplying this genetic information and synthesizing the necessary components to create a new virus. As a result, over time, our cells stop using their energy to make compounds for our body in favor of making hundreds of viruses. The new viruses, in turn, will be able to infect more and more cells and hijack their energy and machinery.
Two ways to curb viral infection
If we focus on one of the key elements in the virus replication process, we find polymerases. Polymerases are structures that are responsible for synthesizing a new copy of the genetic material. Some viruses carry specific polymerases, but others use the polymerases of the organism they are infecting. The coronavirus contains its genetic information in the form of RNA, and when it infects a human cell, it also introduces the RNA polymerase it carries. The antiviral molnupiravir is a specific inhibitor that acts directly on the viral RNA polymerase and whose use has been approved as a treatment for Covid-19.
Other types of antivirals target certain viral proteases. Proteases are virus molecules that are responsible for detecting specific elements within our cells and cut or degrade them. This process is necessary for the virus, since it is what allows it to enter our cells. Nirmatrelvir is the main compound of the antiviral paxlovid, which has also been approved as a treatment against SARS-CoV-2 and specifically inhibits a coronavirus protease.
In a study published in 2022 in the journal Cell Research, the possibility of using these antivirals to prevent infection by the Omicron variant is analyzed. This study carried out in cell cultures treated with different concentrations of molnupiravir, nirmatrelvir, or both, have shown that they would be effective against an Omicron infection. Some of these experiments were carried out in the presence of serum from vaccinated patients, to assess whether the antibodies generated by these individuals represented a barrier that would stop the Omicron infection. The results indicated that this variant was not affected by serum antibodies, but was affected by the presence of antivirals.
To increase the effectiveness of antivirals, it is very important at what point in the infection they are taken. If the virus has already entered a large number of cells, the effect of the antiviral would be limited. If taken in the first few days of infection, it would be possible to shorten the time of infection and also reduce the viral load accumulated within the body. All these factors would be a great advantage in terms of the risk of presenting severe symptoms and also in the window of risk of contagion to other people, since in both aspects the viral load is an essential factor.
Antivirals would help stop the replication of the virus within our body, giving our immune system an advantage to get rid of the threat more easily and quickly. Although this type of treatment would not have a preventive function as vaccines do, it would be an advantage due to its distribution and administration in remote countries with limited access to vaccines. Even in patients who present severe symptoms due to Covid-19 and who require hospitalization, treatment with these antivirals in the first days of admission could also help control symptoms and possible sequelae.
Vaccination against the coronavirus is the only option available today to stop the pandemic and to prevent the virus from continuing to spread among the population. However, providing vaccines in all parts of the world is a big problem. It is possible that a strategy that combines vaccines and antivirals will help us curb cases of infections and hospitalizations caused by severe symptoms.
Li et al. 2022. SARS-CoV-2 Omicron variant is highly sensitive to molnupiravir, nirmatrelvir, and the combination. Cell Research . doi: 10.1038/s41422-022-00618-w