The fight against the coronavirus has been led by the development of vaccines , since they represent a preventive therapy that protects us from infection, serious symptoms and even death. However, due to limitations in access to the vaccine, complementary therapies, such as the use of shark antibodies, have also been studied.
What are shark antibodies like?
Sharks have a developed immune system similar to ours. The antibodies in this species have the function of going through the organism and detecting dangers to eliminate them before they invade the cells.
Although they perform the same function as our antibodies, they have some differences. For example, shark antibodies are much smaller and have more parts capable of detecting antigens, especially in areas difficult to access for our larger and more rigid antibodies.
This type of antibodies, called VNAR , also have certain advantages in the development and optimization as treatments for different diseases, because they can be adapted to the needs in formulation and preparation.
Two studies published at the end of last year in the scientific journals Nature communications and in the FASEB Journal by two independent research groups have shown that these VNAR antibodies can neutralize the entry and potency of SARS-CoV-2 infection .
Why shark antibodies?
The reason why these researchers decided to check whether shark antibodies could be an additional therapy against COVID-19 is because studies had already been carried out on this type of antibody and its potential “tailor-made” development against different antigens.
Building on previous analyzes and a series of models to confirm that the generated VNAR antibodies bound to the coronavirus molecules , the researchers focused on two molecules out of all those they developed:
- 3B4 antibody
- 2C02 antibody
Both antibodies are capable of binding to the protein S (spike) of the coronavirus, which is responsible for recognizing the surface of our cells and starting the infection. However, the 3B4 and 2C02 antibodies block different regions .
Analyzing the results, the researchers suggest that the combined use of both VNARs could be the optimal option to neutralize the entry of the coronavirus into our cells by disabling protein S on both fronts.
Furthermore, it is believed that this potent efficacy may be due to its size. Being much smaller and more flexible than our antibodies , it is possible that they are able to “sneak” between the gaps in the S protein that cannot be blocked by our immune system.
Antibodies effective against different variants
One of the great concerns about the pandemic continues to be the appearance of new variants and the risk of loss of immunity achieved with vaccines against the original variant.
For this reason, the researchers also tested the efficacy of VNARs against the variants available to date. The results confirmed that these shark antibodies maintained their ability to neutralize the Alpha, Beta and Delta variants of the coronavirus.
A therapy for other coronaviruses
Some of the additional experiments carried out in this study were based on testing whether these VNARs could block other types of coronavirus found in bats. The results were very positive against SARS-CoV-1 and MERS-CoV , since they share some molecules with SARS-CoV-2.
It was even tested whether it was capable of neutralizing another coronavirus that is present in bat populations and is capable of infecting human cells but has not yet caused an outbreak in our population: WIV1. One of the VNAR antibodies was also able to neutralize this virus .
A project still in progress
These studies have been carried out in laboratory models using cell lines as artificial infection systems. These experiments are very useful to analyze the neutralizing capacity against infection , but they have obvious limitations.
Until these antibodies become a therapy available to health professionals, it is necessary to carry out studies in animal models and clinical trials in humans , which could take several years .
In the case of proving its efficacy in humans, this antibody therapy could be used not only against COVID-19 but also against other types of coronaviruses that have a similar structure, and that could pose a risk to humans in the future.
The probability of this happening seems higher than was believed a few years ago, so having complementary treatments already developed and tested in animal models would represent a great advance and save time if they were needed . In science, what is invested is reaped years from now, and it is preferable to be prepared than to go against the clock, especially in a pandemic.
References:
Gauhar et al. 2021. Single domain shark VNAR antibodies neutralize SARS-CoV-2 infection in vitro. FASEB J. doi: 0.1096/fj.202100986RR
Ubah et al. 2021. Mechanisms of SARS-CoV-2 neutralization by shark variable new antigen receptors elucidated through X-ray crystallography. Nat Commun. doi: 10.1038/s41467-021-27611-y
