Category:Hepatitis C
From Hepatitis C Resource Centre
Various viruses are specific to particular species and hepatitis C is a human only virus classified as a separate genus (hepacivirus) within the flaviviridae family that includes yellow fever and dengue fever. It infects liver cells.
Recent research indicates that the virus infects some other cells, notably a category of white blood cells (peripheral blood mononuclear cells) and the lymphatic system as a whole. It may also infect bone marrow cells, precursors of the affected white blood cells, and kidney cells.
It is an RNA virus which means that the core of genetic material is ribonucleic acid rather than deoxyribonucleic acid (DNA). RNA viruses are not as genetically stable as DNA viruses and tend to mutate rapidly.
There is little doubt that the virus prefers liver cells and no absolute proof that it can replicate elsewhere in the body – although the degree of mutation-induced variation in different locations suggests that it might. Anyway, these other sites likely serve as a reservoir for reinfection and may well explain the resurgence of the virus after unsuccessful medical treatment and successful liver transplant.
Hepatitis C virus is exceptionally small, measuring just 50 - 65 nanometres in diameter. If you laid 200,000 virions out in a straight line, that line would be only one centimetre long. The outer envelope has a number of protrusions so that the viron looks a little like a koosh ball. It uses these protrusions to attach itself to cell walls thus beginning the process of invasion of the host cell.
As the virus replicates, it evolves over time, persisting as a collection of closely related but non-identical strains known as viral quasispecies. Mutations tend to occur in certain proteins in the outer viral envelope. This process assists the virus to elude immune surveillance by the host’s antibodies, which are programmed to recognise the original, infecting organisms.
The production and deployment of antibodies targeted against specific invading organisms is part of our adaptive immune response to infection. That is one of the reasons why so many hepatitis C-positive people develop chronic infection. It is also a major problem for researchers trying to develop vaccines against hepatitis C.
Hepatitis C virus also appears to interfere with the innate immune response – the body’s first line of defence against unwanted bodily intruders. All cells produce interferon (a protein important in the innate immune response) in response to infection. Hepatitis C virus is believed to inhibit the production of natural interferon. Synthetic interferons, which boost the immune response against the virus, are fundamental to current medical treatment of hepatitis C.
Viruses can damage the body in two ways:
- They may damage and destroy host cells directly. This process is referred to as ‘cytopathic’.
- They may provoke an immune system response that causes host cell injury and death as well as other bodily ill-effects. This process is referred to as ‘immunopathic’.
Hepatitis C virus is now thought to be largely immunopathic, both in terms of liver cell injury and the induction of immune system disorders. However, cytopathic mechanisms of liver injury have not been entirely excluded. It may be that both processes are involved.
Articles in category "Hepatitis C"
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