The world at large has benefited from the wide range of applications in Computer Science and Biology that improved the quality of life in the past 50 years. In both these branches the terms virus and antivirus are well-known, and used similarly, although the computer scientists may be baffled at statements from (micro) biologists like “the bacteria multiply by division”!
Understanding the terms “viral” and “antiviral” attains significance when the whole world is optimistically looking for a quick solution to the Covid-19 pandemic. It must be noted that nowadays, the term ‘viral’ is employed more frequently to refer to social posts that circulate rapidly!
The installation of antivirus software (akin to vaccination given to the kids with a set of vaccines to protect against different diseases) to detect/protect against the viruses requires a regular upgradation of the software, as there is a constant emergence of new viruses. The appearance of new viruses that corrupt software (like the new viruses that cause diseases) is more routine in computer science. Many things will come to a standstill if the computers stop functioning, a situation similar to the current one with Covid-19. To understand how it is difficult to control viruses, we need to understand the uniqueness of viruses as infectious agents.
The virus in computer science and biology
Covid-19 has forced the common person to develop a deeper understanding of the meaning of virus and antivirus, since with this, real lives are under threat.
The term virus has become more popular in the computer era, referring to the frequent troubles in using the computer when the software is corrupted. The computers either stop working or slow down and do something unexpected. The computers which are loaded with a specific software and received the virus through email or through virus-infected external devices like the pen drive, external disk, compact disc, etc. Antivirus refers to the software package(s) that get rid of the viruses infecting any software-driven gadgets. Dealing with the virus or antivirus on inanimate computers has not bothered many.
Viruses that infect the animate objects (living things) are obligate parasites (very high degree of specificity) which require a living host for their multiplication. Viruses are nanoparticles (the smallest could be ~17 nm with about 1700 nucleotides of genome while the largest virus is close to the size of a small bacterium with about 30,00,000 nucleotides) which cannot replicate outside a living host. A virus that infects humans is usually different from one that infect animals, plants, bacteria, algae, fungi etc.
Viruses contain either a single stranded or double stranded nucleic acid like deoxyribose nucleic acid (DNA) or ribose nucleic acid (RNA), as their genetic material (that codes for different genes). They have a coat that covers the nucleic acid and which is made up of protein. Some of them also have an envelope outside the protein coat. The multiplication of the virus, inside a living host, leads to the development of disease in the host. Infection occurs when the virus finds a way to enter the host’s cell, passing through the cell membrane guided by a specialised recognition mechanism involving a specific receptor of the host. The process of viral multiplication requires several energetic metabolites drawn from the host. The increase in viral particles in the host, therefore, is at the cost of several molecules, including energetic metabolites and the enzymes involved in synthesis of DNA/RNA or protein, produced by the host for its own routine functions including protein and nucleic acid synthesis. The more the virus replicates and spreads in the body, more of the host’s energy is drained.
A computer virus also finds a way to integrate itself into the software – the more we use the system, the more it spreads in the system). The computer comes to a standstill when the first alert is ignored about the infection and if used continuously without using an appropriate version of the antivirus software. Advanced versions of software often build layers of protection against viruses (a form of immunity).
In living hosts, especially those with different layers of innate immunity, not all viral infections can debilitate the host, since the chances of the host immunity suppressing the virus are very high. For instance, the common cold (caused by viruses), as the saying goes, “cured by doctor in 7 seven days and without doctor in one week”! But we have several forms of viruses, including newly evolved ones like Covid-19, which are not recognised easily by the host. By the time the hosts understand the severity of the virus, most of the damage would have already occurred – for instance, the loss of more than 2.6 lakh lives in just five months due to Covid-19.
Handling viruses is challenging
People wonder as to why is it difficult to control the viruses. The real problem in controlling viral infections comes from a seemingly simple scientific issue – the pool of metabolites and biopolymer synthesising machinery that the viruses draw from the host. Bacteria also draw the energetic metabolites for synthesis of DNA/RNA or protein from the host, but they use bacterial-genome encoded enzymes for DNA/RNA and protein synthesis. So, the enzymes and processes for the synthesis of DNA/RNA or protein by the bacteria, inside the host, occur independent of the host machinery for nucleic acid/protein synthesis. About a dozen crucial steps involved in the synthesis of the components in the DNA/RNA or protein in bacteria are identified as drug targets to cure several of the bacterial diseases. It is therefore possible to target the crucial steps required for bacteria to synthesise these biopolymers to selectively eliminate the bacterial pathogens without affecting the hosts.
In case of viral diseases, the synthesis of biopolymers cannot be used as a target because the virus-debilitated host will not be able to perform its own basic functions if the nucleic acid and/or protein synthesis of the host becomes the drug target. The viral infections thus become difficult to treat with our common drugs as the virus-specific targets inside the host are not too many. It necessitates a thorough understanding of the virus genome and the proteins that are crucial for the virus to replicate. Similarly, for preventive measures like vaccine development, the potential epitopes (candidate vaccines) to be recognised by the host to produce antibodies, should not share a similarity with the molecules of host origin.
The option for virologists and immunologists to find remedy for viruses, therefore, has always been a challenging task.
Prof. Appa Rao Podile
Vice Chancellor, University of Hyderabad
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