Biotechnology Forums

Full Version: Virus - Types, Diseases and Applications
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
Viruses are smaller in size to bacteria and can also be described as nano particle stating its small size. Viruses are parasitic in nature as they always depend on a host cell or organism for replication. Viruses are known for its infectious nature, infecting right from bacteria to humans.

Virus grouping: Viruses are divided and grouped into various types using the key factors like morphology (structure), biological role, type of genetic material and mode of multiplication. The unique feature of virus is that their genetic material is covered by a protective layer termed as capsid made up of units of protein encoded by the virus itself. The association of the capsid and the genetic material (nucleocapsid) describes the structure of the virus. The viral structure has an outer envelope made up of lipoproteins and the space between the capsid and the envelope is called as Matrix which acts as a bridge between the inner nucleocapsid and the outer envelope. The matrix region is composed of proteins again.

Viruses are classified based on the type of genetic material present into DNA virus and RNA virus. DNA virus, as the name indicates have DNA as their genetic material and the DNA is either linear or circular and double stranded or single stranded. Based on the length of the genetic material present, these viruses are again divided into big and small DNA viruses. Herpes virus and pox virus are examples of double stranded DNA virus and parvo virus is single stranded DNA virus. The virus with RNA as genetic material are grouped under RNA viruses and the RNA present may be double stranded or single stranded. Also the single stranded RNA virus may have either cationic or anionic strand. Reo virus is an example of double stranded RNA virus and picorna virus is a positive single stranded RNA virus and Rhabdo virus falls under the group of negative single stranded RNA virus.

Viral Life Cycle: Virus is host specific and this nature enables them to bind themselves to the host cell. Once attached it penetrates and enters the host cell environment. The outer envelope is shed inside the host cell and mRNA is synthesized through transcription which is followed by translation into proteins. Following this is the glycosylation process and the replication begins resulting in multiple viral copies, which then assemble and exits the host cell as mature viruses.

Viral Infections: The potential of a virus to cause infection to the host cell is termed as virulence. Viruses infect bacteria, plants, animals and humans causing various reversible and irreversible diseases.
Humans: Eye infection caused by Herpes simplex virus, cytomegalo virus, encephalitis by LCM virus, Rabies virus and the occurrence of common cold is due to para influenza virus, respiratory syncytial virus. The Hepatitis virus of different groups A, B, C, D & E in causing hepatitis, a liver disease and Coxsackie B virus is identified in pancreatitis. Infection by rota virus, adeno virus and corona virus causes GI tract related diseases. HIV, Herpes simplex 2 and Human Papilloma virus are the major causative agents for the sexually transmitted diseases.

Plants: Plant viruses have different shapes like icosahedral, rod, filament or isometric. Some of the plant viruses are Tobacco Mosaic virus, cucumber mosaic virus, Lettuce mosaic virus and citrus psorosis virus. The viruses are named based on the type of disease they cause in plants.

Birds and Animals: The H1N1 episode due to the infection of birds by Influenza virus A and the infection of pigs by influenza virus (B or C) spreading swine flu are the classic examples of bird and animal viruses and their transmission to humans.

Bacteria: virus with a potential to infect bacteria is called as a bacteriophage. T4, T5, T7 phages, MS2 phage and Qβ phage are examples of the bacteriophages. The structure of a bactriophage is unique with three regions like icosahedral shape as head with shaft like middle region and tail like structures at the base.

Cancer and virus: Few viruses are detected with their ability to cause cancer in humans. The cancer causing oncogenes were first identified and studied in retrovirus. The human Papilloma virus causes cervical cancer and the chronic liver disease due to the infection by Hepatitis B virus activates the liver cells to become cancerous.

The structure, function and mode of replication enabled scientists to make use of viruses in different field of biological science. The ability of the virus to deliver the genetic material into host made them as suitable vectors in genetic engineering. The association of the virus with the immune system enabled to develop vaccines for various viral diseases. The use of virus in the field of nanotechnology is cited by the use of cowpea mosaic virus as signal amplifiers in DNA microarray technique by the researchers of Naval Research laboratory, Washington, D.C. The different perspective on virus as a tool in cancer therapy and gene therapy will be beneficial. The ability of the virus to infect bacterial cell is used to kill pathogenic bacteria (Phage therapy). Besides all this beneficial applications of virus, the threat lies in the fact that they can be used as bioweapons.
Cancer diseases are caused by some virus only, which is most harmful diseases. With that viruses that person will become total unhealthy and faces lot of problems. But we are lucky to have great clinics and doctors here.