Key Notes on Adsorption in Viruses

Adsorption is a process by which a substance (solid, liquid, or gas) adheres to the surface of a substrate (solid) with the help of physical attraction. It is not the same as the absorption process because one substance’s molecules permeate into the substrate and fill up the pores. Adsorption plays a vital role in biology and physical chemistry. Out of several applications, adsorption in virus replication is considered the crucial form of study. It determines the virus’s life cycle, the cell substrates that allow replication, uncoating, synthesis, and more. This is why appropriate measures are taken for determining the rate of adsorption of a viral cell to the host cell and the implications.

What is a virus and its cell structure?

The virus is a microorganism that will stay as a non-living being when present in the air, water, or anywhere. It starts showing life activities only when the cells enter a host organism. It can be a bacterium, a plant body, an animal, or a human. To understand the concept of adsorption in virus replication, first, it is important to understand the cell structure.

When the viral cells adhere to the host cell, it completes the growth and becomes a virion. There are two prime components in a virion – an outer protein coat made from lipoproteins, glycoproteins, and more; and a genetic material that can be either the DNA or RNA. Unlike the eukaryotic cell, a virion does not have any well-defined nucleus. Only the DNA or RNA strands are present, floating in the cytoplasm.

The genetic material is responsible for replication, while the protein coat, also termed the capsid, is important for attachment with the host cell via the surface receptors. This is where the concept of adsorption of viruses to cells is considered.

Adsorption of the viral cells to the host cells

Most host cells have receptors in the cell membrane. These receptors act as anchor points for the virions (fully developed viruses). When a viral cell comes in contact with the host cell, its capsid has adsorption property owing to which it adheres to the physical receptors of the host cells. Here, adsorption can be successful only when:

1. There are cell receptors around the cell membrane of the host cell.
2. The component of the viral cell’s protein coat and that of the receptors need to be compatible for adherence.

For the adsorption of viruses to cells, their membranes need to have specific components. For example, the HIV envelope must have GP120 glycoprotein, while the host cell membrane should have the CD4 receptor cells. Only then will the virions be able to adhere to the host cell through the process of adsorption. There is no chemical interaction between the glycoproteins and the CD4 cells. Rather, they behave like a lock and key and attach physically.

Replication of the virus-cell post adsorption

Once the adsorption in virus replication is complete, different steps will be carried out till the infection is complete.

1. The first step is the penetration of the host cell membrane, and the virion cell membrane fuses through a process known as endocytosis.
2. Secondly, the uncoating of viruses occurs where the capsid or the protein layer will be dissolved automatically. Simultaneously, the genetic material of the virus, be it the RNA or DNA, will be released into the cytoplasm of the host cell.
3. The genetic material starts replicating inside the host cell. The replication process will depend on the type of material present in the cell.
4. After the replication is complete, a phenomenon, also known as lysis, takes place. Here, the viral genomes consume the cell, and hence, they burst out, releasing the viral RNA or DNA into the host body.

Can the adsorption of viral cells to the host cell be stopped?

The study of adsorption in virus replication is important in formulating drugs and vaccines that can stop the spread of infection by rendering the virions infertile. Several chemicals and drugs inhibit the adsorption process and prevent the interaction of the capsid proteins with the receptors present in the cell membrane. Therefore, the virions fail to push the genetic material into the cytoplasm, and eventually, they die out. This way, the infection rate can be reduced easily.

What is another major application of viral cell adsorption?

The adsorption technology is not only concerned with the viral replication method but is also used in water purification. Viruses in water bodies can cause waterborne diseases, like diarrhoea, botulism, and more. Since you cannot use any chemical to remove the microorganisms, a special technique of viral adsorption over a CO2 substrate is implemented.

An adsorbent made from metallic oxides or sand is used in this case. When the water is allowed to pass through, the viral particles will adhere to these filter surfaces. Repeated layers of filters ensure that the water can be purified and made free from microorganisms.

Conclusion

Virology is one of the most important parts of both chemistry and science. The adsorption in virus replication helps understand how the infection starts or how the microbe behaves with the host cell. Based on these studies inhibiting drugs and vaccines are formulated. Since the virus becomes inert outside the host body, it is the only method through which the activities can be known and verified.