The virus is a set of gene. Typical viruses multiplication cycle is divided into six phases: 1. Absorption to the human cell, which is referred to as host cell; 2. Penetration or entry to the human cell; 3. Uncoating to release the genomes; 4. Viruses or virion components production; 5. Assembly; and 6. Released from the human cell.
This series of events, sometimes with a slightly variation. The viral infection of the cells may be productive (lytic response) or nonproductive (no response).
The outcome of an infection depends on the particular virus-host combination. This means, it depends on the relationship, the viruses have with our body cells.
The viruses need to undergo only one stage between the productive and nonproductive. This kind of viruses are called virulent virus or angry virus.
Those viruses that can undergoes both productive and nonproductive, are referred to as temperate viruses. Some of the temperate viruses can be reactivated or induced to leave a latent state (sleeping state), and they enter to a productive state or virulent stage.
The remainder of this article is concerned with the details of the steps of the virulence state. The next article will jump to routes of infectious diseases transmission.
The first steps for viruses to multiply in any viral infections is the attachment known as adsorption of the infecting particles to the surfaces of the cell.
The prerequisites for this interaction is a collision between the virus and the human cell. Only a small fraction of the collisions between a virus and its host cell lead to a successful infections.
The viruses need to have attachment proteins known as receptors. These receptors are more similar to human fingers and hands for grabbing. This is because the virus uses these receptors to attach on human cell.
You still remember enveloped and naked viruses http://drjiyanemedicalhelp.com/genomic-structures-viruses-causing-infection-and-diseases/?
All enveloped viruses that are causing diseases in humans, contain the attachment proteins which are receptors. Some of the viral receptors are also found on human red blood cells of certain species. Such receptors are responsible for hemagglutination.
The particular kind of a virus is capable of inflecting only a limited spectrum of of cell types called its host range. This kind of cell host range is very important in determining the pathology of the infection ( the steps in which the virus under go in order to cause an infection).
The entry and uncoating
Once the virus has attached on the human cell, penetration which is the entry into the inside of the cell, the virus is no hidden from the immune system.
The uncoating stage happens simultaneously with the entry or may happened in series of steps. Here we will discuss two type of viral entry and uncoating.
1. The enveloped human viruses
Two basic mechanisms for the entry of an enveloped human viruses into the cell. Both of the mechanisms involve fusion of the viral envelope with a cellular membrane, and the release of the free nucleic capsid into the cytoplasm.
The envelopes of these viruses contain protein spikes (hands finger like) that promote fusion of viral envelopes with the plasma membrane of the cell, releasing e nucleic capsid directly into the cytoplasm.
2. The naked capsid human viruses
Viruses may undergoes dissolution, getting dissolved by binding on the human cell membrane or skin. The nuclei acid is directly deposited to the targeted sites. Now let get to refresh our understand, that viruses are separated into RNA viruses and DNA viruses.
So, most RNA viruses replicate or multiply on the cytoplasm, with the exception of influenza virus (flue) and the retrovirus (HIV). Influenza virus, retrovirus, and other DNA viruses except poxvirus replicate or multiply in the nucleus of the human cell.
Genomic structures replication (multiplying)
The human cells obviously contain the enzymes and tons of protein accessories required for the replication of the DNA.
The smallest DNA viruses like parvovirus, they depends on the infected human cell so that if that infected cell divide thus the virus divide too.
This also occurs with some of RNA viruses, the good example of this kind is HIV. That is the reason why it is not easy to clear or eliminate it. Topic on HIV will be discussed in depth later.
Assembly of viral particles
Remember that we said one human cell is infected by a virus and human cells are naturally multiplying by division. So now the virus is inside the cell that is prone to multiply by division.
The genomes of the viruses and that of the human cell are now one (integrated), the first thing to divide is the cytoplasm, which is a fluid inside the cell. Followed by the nucleus inside the cell. Once all of this is done.
The overall cell divides with the the virus in it. So now more of the infected human cells are thus produced.
Assembly stage the place when each of the new cell’s proteins are coming together to make new infected cells. Note: it is not simple as in this generalization to describe this phenomenon.
Release of new viruses
Once the viral particles have been assembly, now new baby viruses causing infection and diseases are ready to be released from the mother host cell.
This all happens by escape from the infected cell through coding for enzymes that lysis the cell. These enzymes weaken the cell wall by cleaving specific bonds in peptidoglycan layer. The weakened cells burst as a result of the osmotic pressure.
Human viruses are furthermore released as follows:
1. Cell death
The mother infected cell or host infected cell dies after giving birth to the new infected cells or viruses.
Presumably because the viral genetic program is dominant and precludes the continuation of normal cell functions required for survival.
The naked capsid human viruses lack specific mechanisms for lysing the infected cell and apparently are released into the extracellular milieus simply as a consequence of cell death.
With the exception of other viruses, all enveloped human viruses acquire their membrane by budding either through the plasma membranes. In the case of herpes viruses, ultimately escape from the cell after budding through nuclear membrane is unclear (more research is required).
For viruses that bud, it is important to note that the plasma membranes of the infected cells contains virus-specific glycoproteins that represent foreign antigens. This means your infected cells become the target of your own immune system.
Protection from viral infection is to be accomplished at the level of antibodies binding to the viruses, it must occur before adsorption and prevent viruses from attaching to and penetrating our cells.
Most enveloped viruses acquire an envelope during released by budding. Retroviruses except HIV reproduce without cell death.