Virology Overview.docx

- **Virology: General Info** - **Virology** is the study of viruses and viral diseases. - A **virologists** is someone who studies viruses. - **Zoonosis** is a viral disease that can be transmitted from animals and birds to humans. - **Veterinary virology** is t...

- **Virology: General Info** - **Virology** is the study of viruses and viral diseases. - A **virologists** is someone who studies viruses. - **Zoonosis** is a viral disease that can be transmitted from animals and birds to humans. - **Veterinary virology** is the study of viruses in animals, birds, and marine species. - Veterinary virology is important because: - Viral diseases cause high rates of mortality and morbidity in animals and birds. - Viral disease have a large impact on food safety and security. - Rinderpest depleting cattle as a food supply and causing famine is an example of viral impact on food safety and security. - Viral diseases cause tremendous economic losses, and are expensive to control and prevent. - **Pleomorphism** is the ability of (some) viruses to alter their shape or size. - Pleomorphism is very common within enveloped viruses. - Veterinarians are the first line of defense against the animal-human interface with zoonotic diseases. - **Viral: Structure** - **Viruses** are non-living organisms that do not possess standard cellular organelles (such as a mitochondria, golgi apparatus, chloroplast, and an endoplasmic reticulum with its associated ribosomes.) - Viruses only contain a nucleic acid genomes (such as DNA or RNA) that is surrounded by a capsid (protein coat), and in some cases, may have an additional layer of a lipid **envelope** which covers the capsid. - Due to the lack of certain organelles, viruses must rely on a host for protein or energy synthesis, causing all viruses to act like **obligate intracellular parasites.** - Outside of the host, viruses are dormant particles. - Inside of the host, viruses hijack the host's machinery to aid in protein and nucleic acid production to be utilized by the next generation of viruses. - Viruses do not have the genetic capacity to multiply by division (outside of the cell), such as binary fission. - **Viral replication** resembles an assembly line where various parts of the virus come together from different parts of the host cell to form new viral particles. - A **capsid** is a protein shell of the virus which encases/envelopes the viral nucleic acid or genome. - Capsids are composed of **capsomeres** which are held together by non-covalent bonds. - The word capsid originated from Latin Capsa "box". - A **nucleocapsid** is composed of a capsid and viral nucleic acid (DNA/RNA)/Genome. - The viral **envelope** is usually a lipid bilayer derived from/ stolen from the host cell. - Glycoproteins are present on the surface of the envelope and may appear as spikes. - Naked or non-enveloped viruses only contain a protein capsid enclosing the viral nucleic acid. - Enveloped viruses have an additional lipid layer enclosing the protein capsid enclosing the viral nucleic acid. - The **virus nucleic acid** is the most important part of the virus, as it contains all of the viral genetic information (DNA or RNA). - Both DNA and RNA can be either single or double stranded. - **Viral Replication: Steps** - Step 1: Attachment - Attachment is when the virus binds to specific host cell (surface) receptors, similarly to a lock and key model. - Step 2: Penetration - Penetration is when the virus enters the host cell. - Step 3: Uncoating - Uncoating is when the viral protein coat is removed and either DNA or RNA is released into the host cell. - Step 4: Synthesis of viral nucleic acid and protein - During the synthesis of viral nucleic acid and protein, the viral DNA/RNA will hijack the host cell and begin replicating within the cell, causing host cell damage. - Step 5: (Viral) Assembly and Maturation - Step 6: (Viral) Release in large numbers - **Viral Replication: Impacts on the Host Cell** - Viral replication can cause: - (Host) Cell death - Host cell death can be due to lysis, apoptosis, or alterations in the cell membrane. - Apoptosis is cellular suicide to prevent the completion of viral replication. - Cellular lysis is the rupture of the cell after viral replication has been completed. - Alterations within the cell membrane can be due to the virus poking holes in the lipid membrane (as part of the viral replication cycle). - Host cell transformation into a malignant cell. - Viruses that cause the host cell to transform into a malignant cell are known as oncogenic viruses, such as HPV. - Oncogenic viruses cause cancer. - No apparent change to the host cell - No apparent changes are common in latent, chronic, or persistent infections. - Multinucleation or fusion of (host) cells. - **Viral: Classification/Taxonomy** - The **ICTV (International Committee on Taxonomy of Viruses)** is the only body (appointed by the International Union of Microbiological Societies) in charge of developing, refining, and maintaining the universal viral taxonomy. - The ICTV takes into account the: - Viral morphology - Viral replication strategies - Nature of virus genome and virus genetic diversity - **Viral: Diagnosis/Detection** - Viral infections can be diagnosed using: - **Gross evaluation and histopathology**. - When diagnosing a viral infection, it is important to take into account the patient\'s clinical signs, any necropsy findings, and any histopathology findings. - **Histopathology** will indicate any characteristic changes in cells/tissues. - **Cultivation/isolation** of viruses within cell/tissue cultures or inoculation within eggs. - Cultivation involves growing cells outside of the host to see the viral impacts. - This practice is most common in research facility labs rather than clinical labs. - The **electron microscope** - The electron microscope can be used to identify and study viral morphology. - **Serology** - Serology is utilized for detecting viral antigens or host antibodies against a virus. - **ELISA (enzyme-linked immunosorbent assay)** is an example of serology test that can be used for viral detection. - The **detection of viral nucleic acids/molecular biology** - **RT-PCR** (reverse transcription polymerase chain reaction) and **PCR** (polymerase chain reaction) are examples of ways the viral infections can be diagnosed using the detection of viral molecular biology. - **Viral: Treatment** - Viruses can be treated with: - **Antiviral drugs** - The issue is that antiviral drugs are in very low supply. - **Immune system stimulation** - Interferon therapy is an example of immune system stimulation. - Interferons are glycoproteins with antibody properties. - Synthesized antibodies or administration of **natural antiserum** (antibodies) - Natural antiserum involves taking plasma from an infected individual and injecting that plasma into someone else to help boost the amount of antibodies in the injected individual. - **Viral: Prevention** - Viruses can be prevented with: - **Vaccinations** - Vaccines are the most common way to prevent viral infections. - A con for vaccine use is that the immune response produced by vaccines is delayed. - **Proper hygiene and sanitation** - Proper hygiene and sanitation are prevention methods best used for food born illnesses. - **Elimination of arthropod vectors** - Asfarviridae and Zika are examples of viruses that utilize vectors. - Mosquitoes are an example of a vector. - **Quarantine and culling** - **Culling** involves killing the infected animals and burning them. - Culling was the only solution in preventing the spread of African Swine Fever.