Viruses are small infectious particles consist of nucleic acid (DNA or RNA), an outer coat called capsid and sometimes a glycoprotein envelope. While some viruses have RNA as a genetic material such as hepatitis C virus, others have DNA such as poxviruses. Some studies consider viruses as a non-living organisms because of the fact that they cannot reproduce and synthesize their essential materials independently (NCBI, 2004). Viruses can infect bacteria, animals and plants (UXL Encyclopedia of Science, 2002). As they lack many structures that are needed for growth and replication like ribosomes, they are an obligatory intracellular parasites and need to invade living cells to produce their basic materials like proteins, amino acids and fats. Viruses invade living cells and use their machinery to produce specific proteins and synthesise their own genetic materials by integrating their DNA into host cells genome (Molecular Expressions, 2005). To achieve this, viruses need to be capable of recognising specific receptors on host cell surface which is the first step of viral invasion and pathogenesis. This recognition permits viral attachment to take place and facilitate viral entry into the host cell. This attachment occur between viral specific fusion proteins (ligands) ,such as M2 pore proteins on Influenza viruses and the trimeric rabies virus glycoprotein (RVG) on rabies virus, and the host cellular surface proteins (receptors) such as CD4 and CCR5 proteins on T helper cells.
Once the virus is inside the host cell, it starts to alter the cellular reproductive machinery and produce new virus particles. This alteration in the cell machinery and the reproduction of new viruses can cause the immune response to be activated against the virus. However, some viruses infect immune cells such as T helper cells, which are a type of white blood cells, and weaken the host immune system. This essay will consider the role of virus receptor recognition in the determination of pathogenesis.
The pathogenesis of any virus depends totally on the virus ability to enter the host cell. That is because of the fact that outside a living cell the virus is inactive as a grain of sand (UXL Encyclopedia of Science, 2002). So, the virus needs to be able to distinguish a specific host cell to invade and stick to it. The cell entry is mediated by specific viral fusion proteins. There are two main classes of these proteins. Those which contain two prominent alpha helices are called class I fusion proteins and the other class is the flaviviruses envelope glycoprotein (E) and called class II fusion proteins (Hrobowski et al, 2005). These fusion proteins are of a significant role in the virus entry to the host cell. Measles virus (MV) will be a good example to define the role of virus receptor recognition in the determination of pathogenesis.
Measles virus (MV) or rubeola virus is a transmittable RNA virus that leads to about 1 million deaths annually. These deaths are...