Viruses have a simple structure, consisting of genetic material contained with a protein shell known as a capsid. In some viruses, an envelope surrounds the capsid. The envelope is typically derived from the host cell membrane, and usually contains viral glycoproteins. Viral genomes are composed of DNA or RNA, which can be single- or double-stranded, circular or linear, and can vary in terms of length and the number of DNA or RNA molecules.
Viruses can only replicate within a living host organism. This process begins with attachment to the cell wall or cell membrane, following which the viral genome is injected into the host cell. Here, the virus hijacks the host’s cellular processes, forcing it to replicate the viral genome and synthesise new viral proteins. These components are assembled into new viruses, which leave the host cell via lysis and can go on to infect further organisms.
Viruses as causative agents of disease
Viruses which cause disease in humans include chicken pox, the common cold, Ebola, HIV, influenza and rabies. Several viruses have been linked to cancer, including human papilloma virus, Epstein-Barr virus, and hepatitis B. New and re-emerging viral diseases include severe acute respiratory syndrome (SARS), Dengue fever and Zika. To better understand viral pathology and tackle the spread of disease, virologists study many aspects of viral infection, replication and mutation.
Viruses as tools for research
Viruses are widely-used as vectors for both in vitro and in vivo gene delivery. Common viral vectors include adenovirus, adeno-associated virus, lentivirus, herpes simplex virus and retrovirus. To minimise risk, these vectors are modified, often through deletion of genes essential to replication. Selectable markers allow easy identification of transfected cells. Integration of virally-encoded genes into the host genome allows for stable protein expression.
A key clinical application of viruses is their use as vaccines. The MMR and chickenpox vaccines are based upon attenuated viruses, while the vaccines for polio and hepatitis A are instead inactivated. Viruses are also used as vectors for gene therapy. Viral-based gene therapy drugs which have received regulatory approval include Gendicine™ for treatment of cancers with mutated p53, and Glybera for lipoprotein lipase deficiency. Many other viral-based gene therapy drugs are currently in development.
High-quality virology reagents
Reagents for virus research include viral vectors, viral expression systems, recombinant viral proteins, quantitative assay kits, and antibodies against key viral components. Our virology product portfolio also includes FISH probes, kits for qPCR and RT-qPCR, and slides on which virus-infected cell cultures have been grown.