Viral deoxyribonucleic acid

Virases are much simpler organisms than bacteria, and they are made from protein substances and nucleic acid. A single nucleoprotein molecule formed from molecules of nucleic acid that are chemically bound to a bulky protein molecule can be considered a simple viral particle. The protein molecule plays the role of a protective membrane. Thus the virus can be schematically described as a nucleic acid insert that is protected by a protein covering. A virus can contain either ribonucleic acid or deoxyribonucleic acid, but it never contains both of them together. The type of nucleic acid is the basis of one of the classifications of viruses. Viruses are obligatory intracellular parasites, which, upon entering a cell (i.e. after being infected) use many biochemical systems of the host cell. 

Walsh (2003) defined biopharmaceuticals as therapeutic protein or nucleic acid preparations made by techniques involving recombinant deoxyribonucleic acid (DNA) technology. Therapeutic proteins include blood clotting factors and plasminogen activators, hemopoietic factors, hormones, interferons and interleukins, and monoclonal antibodies (LeVine, 2006). Over time, the term biopharmaceutical has broadened, and, in addition to proteins and nucleic acids, now includes bacteriophages, viral and bacterial vaccines, vectors for gene therapy, and cells for cell therapy (Primrose and Twyman, 2004). Attention here focuses on proteins, since the majority of approved biopharmaceuticals are proteins. 

A virus is a submicroscopic agent of infectious disease that requires a living cell for its multiplication. The two essential components of a virus are protein and nucleic acid. Whereas normal cells contain both RNA (ribonucleic acid) and DNA (deoxyribonucleic acid), a given virus contains only one, not both. A virus cannot multiply on its own as a normal cell does. It has no metabolic enzymes, uses no nutrients, and produces no energy. It is just a particle of protein and nucleic acid. A viral particle is tightly packed inside a protein coat that protects it. This unit is called a virion. 

Viruses are one of the smallest biological entities (except viroids and prions) that carry all the information necessary for their own reproduction. They are unique, differing from procaryotes and eucaryotes in that they carry only one type of nucleic acid as genetic material, which can be transported by the vims from one cell to another. Viruses are composed of a shell of protein enclosing a core of nucleic acid, either ribonucleic acid (RNA) or deoxyribonucleic acid (DNA), that codes for viral reproduction. The outer shell serves as a protective coat to keep the nucleic acid intact and safe from enzymatic destruction. In addition to their protein coat, some viruses contain an outer covering known as an outer envelope. This outer envelope consists of a lipid or polysaccharide material. 

The progression of viral mRNA production during the infection cycle was characterized by means of qPCR measurements. MDCK cells infected with influenza A/PR/8 virus (multiplicity of infection = 100 one cell is virtually infected by 100 virus particles) were harvested at various points post infection. Noninfected cells were collected for control experiments. The total RNA was isolated and purified by using commercially available kits. The optical density (OD) of isolated RNA was measured and aliquots were subjected to in vitro transcription. After quantification (by OD measurements), the resulting complementary deoxyribonucleic acid (cDNA) was analyzed in qPCR experiments. 

O Callaghan, D. J., Hyde, J. M., Gentry, G. A., and Randall, C. C., 1968, Kinetics of viral deoxyribonucleic acid, protein and infectious particle production and alterations in host macromolecular syntheses in equine abortion (herpes) virus-infected cells, J. Virol. 2 793. 

Hand, R., and Tamm, I., 1973, Reovirus Effect of noninfective viral components on cellular deoxyribonucleic acid synthesis, J. Virol. 11 223. 

Rose, J. A., Koczot, F. Adenovirus-associated virus multiplication. VII. Helper requirement for viral deoxyribonucleic acid and ribonucleic acid synthesis. J. Virol. 

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