May 3-9 2021
CRISPR-Cas technology: a new tool in the fight against COVID-19?
The scale of the COVID-19 epidemic has shown clearly the extent to which we were ill-prepared for it. Making diagnostic tests quickly available to large numbers of people and developing new treatments against a new virus are not easy given our current methods. Without the means of detecting emerging or re- emerging viruses at an earlier stage of an epidemic, and without effective anti-viral tools, viruses will continue to threaten human health. The techniques used today for diagnosing viral infections, whether PCR or antigen tests, are specific to this virus. And the development of treatments requires a good knowledge of the viral proteins and the proteins of the targeted host. CRISPR-Cas technology, which has been shown to be effective in the treatment of genetic illnesses, may be a useful supplementary tool in the fight against viral illness.
The CRISPR-Cas system is present in most species, but it was first discovered in bacteria, as a system of protection against pathogens, allowing detection of a foreign nucleic acid (DNA or RNA) and its destruction. The system is made up of a repeated sequence (the CRISPR array, called crRNA) and associated proteins (Cas). There are several types of associated proteins: Cas9, 12 or 13, for example, for those used in the detection of viral nucleic acids or in the treatment of viral infections.
Concretely, the CRISPR repeats allow the detection of a genome-target and the associated proteins cut it so as to destroy it. It is for this reason that this system is also called “molecular scissors”. The Cas9 and Cas12 proteins target the DNA sequences while the Cas13 protein, discovered more recently, allows the single-strand RNA to be targeted (as with the SARS-CoV-2 genome).
As regards the diagnosis of viral infections, the best method today is PCR testing, which requires costly equipment. CRIPR-Cas technology is also highly specific and sensitive, but does not require specialist equipment. Development of this technology for use with RNA and DNA viruses is underway, highlighting the versatility of this method which can be automated to provide a high-throughput diagnostic solution, advantageous in the context of an epidemic.
This method has already been successful against other viruses, for example, in the detection of Ebola and of Zika. When SARS-CoV-2 emerged at the end of 2019, virus detection methods based on CRISPR-Cas technology were tested soon after publication of the first viral genome sequences (see News-COVID-19.info letter, 21-27th December 2020). More tests and checks need to take place before it can be used routinely.
In addition, CRISPR-Cas technology may have an antiviral action, already shown with certain viruses such as HIV or Chikungunya. This possibility was rapidly investigated for use against SARS-CoV-2 and the technology seems to be a potentially useful antiviral therapy, in particular to avoid resistance to treatment. However, its effectiveness and its safety need to be further explored before clinical trials can begin.