When a virus infects a human cell it takes over the cell’s machinery and uses it to produce many more copies of the virus. Eventually, the newly made viruses burst out of the infected cell, and go on to infect other cells in the neighborhood. We have already discussed some of the weapons the innate system can use to defend against viruses while they are outside of cells. For example, proteins of the complement system can opsonize viruses for phagocytosis by macrophages and neutrophils, and complement proteins can destroy some viruses. However, once a virus has entered a cell to begin its reproductive cycle, these weapons are ineffective.
When a virus infects a human cell it takes over the cell’s machinery and uses it to produce many more copies of the virus. Eventually, the newly made viruses burst out of the infected cell, and go on to infect other cells in the neighborhood. We have already discussed some of the weapons the innate system can use to defend against viruses while they are outside of cells. For example, proteins of the complement system can opsonize viruses for phagocytosis by macrophages and neutrophils, and complement proteins can destroy some viruses. However, once a virus has entered a cell to begin its reproductive cycle, these weapons are ineffective.
There are many layers of interrelated defenses. I'm going to name as a starting point for your study: Protein Kinase R, RNA interference, TRIMs, antigen presentation by TAP / MHC, Rig-I and endosomal TLR.
Immune system deal with viruses as internal invaders by use the cellular immunity through T cytotoxic cells and effector cells, while it deal with it as external invader when it come out of the cells through humeral immunity by plasma cells and Abs.
The immune system will use the most effective mechanisms depending on the characteristics of the infectious agents. Different actions take place during viral infections, both towards free viral particles as well as towards infected cells.
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http://apps.sanidadanimal.info/cursos/immunology-old/septimo3.htm
In most viral infections, the immune system has the opportunity of attacking viral particles in some stages of the infection (before viruses enter cells or when they are liberated after their replication). It may also take place in infected cells during the protein production or viral assembling phase. During these stages, antigens that appear in the membrane of the infected cell can activate the immune response.. In some cases, such as endogen porcine retroviruses (three different types have been described: A, B, B1 and C) or herpes viruses (Aujeszky´s disease), infection can last for long periods of time without the presence of any viral particles or surface antigens being expressed in the membrane of infected cells. When this happens, the immune system is unable to fight the infection, because there are not viral peptides to flag its presence. But eventually infection is reactivated (causes are not yet well known) and new infectious virions are liberated.
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