PPT 15-16

• Spike (S) glycoprotein is a protein protruding in the viral surface and facilitates binding of envelope viruses to host cells by attraction with its receptors angiotensin-converting enzyme 2 (ACE2) expressed in LRT cells.
• Cytopathic effect and how it is used to presumptively identify viral agents should be defined.
• The clinical laboratory uses four major methods to diagnose viral infections: direct detection of the virus in clinical specimens, nucleic acid-based detection, isolation of viruses in cell cultures, and serologic assays to detect antibodies to virus.
• Viral isolation is the gold standard against which all other methods are compared and includes cell culture, animal inoculation, and embryonated eggs.
• There are three categories of cell culture: primary cell culture, low passage (or finite) cell culture, and continuous cell culture.
• Primary cell culture is obtained from tissue removed from an animal, such as HEK.
• If a delay is unavoidable, the specimen should be refrigerated, not frozen, until processing occurs.
• Viral isolation can be done through centrifugation techniques such as Enhanced Shell Vial Culture or Shell Vial Centrifugation Enhanced Culture
• Aspirates, or surface swabs, are usually appropriate for lesions.
• Serologic assays detect circulating antibodies to viruses after exposure.
• Specimens for the detection of virus should be collected as early as possible following the onset of symptomatic disease.
• Vero is derived from monkey kidney.
• Primary Monkey Kidney is commonly used primary cell culture
• Specimens for viral isolation should not be allowed to sit at room or higher temperature.
• Process the specimen within 12 to 24 hours of collection.
• Specimens should be placed in ice and transported to the laboratory at once.
• Secretions from the respiratory mucosa are most appropriate for viral diagnosis of respiratory infections.
• Intestinal mucosa - stool specimen is most appropriate.
• For storage up to 5 days, hold specimen at 4 ° C.
• Enteroviruses can cause respiratory infections and may be recovered from the stool after the respiratory shedding has ceased.
• HEp2 is derived from a human laryngeal epithelial carcinoma.
• Finite cell lines, like primary cell lines, are diploid; as the number of passages increases, these cells become more insensitive to viral infection.
• A549 is derived from a human lung carcinoma.
• Enteroviruses are a major cause of aseptic meningitis and can also be isolated from urine specimens.
• Finite cell cultures can divide, but passage is limited to about 50 generations.
• Paramyxoviruses primary cause of respiratory disease in young children.
• Orthomyxoviruses are distinguished by using two major structural proteins — matrix protein (M) and nucleoprotein (NP).
• Rhinoviruses are a family in the Picornaviridae genome, with a non-segmented single-stranded RNA genome, and a naked icosahedral morphology.
• Orthomyxoviruses are a family in the Orthomyxoviridae genome, with a segmented single-stranded RNA genome, and an enveloped helical morphology.
• Paramyxoviruses are a family in the Paramyxoviridae genome, with a non-segmented single-stranded RNA genome, and an enveloped helical morphology.
• Samples that should be collected without viral transport media include blood, bone marrow, CSF, amniotic fluid, urine, pericardial fluid, and pleural fluid.
• Lab diagnosis of rhinoviruses can be made by isolation from nasal secretions in cell culture, but this is not done routinely.
• Most transport media consist of a buffered isotonic solution with a protein such as albumin, gelatin, or serum to protect less stable viruses.
• Influenza A viruses are classified into subtypes using the two major surface glycoproteins hemagglutinin and neuraminidase
• H antigen is used to bind to host cells.
• The antiviral drugs amantadine and rimantadine can prevent infection or reduce the severity of symptoms if administered within 48 hours of onset.
• Antigenic drift is a minor change in antigenic structure as mutations accumulate.
• The transport container should also be unbreakable and able to withstand freezing and thawing.
• Samples that can be collected with viral transport media are respiratory, swab, and tissue samples.
• N antigen cleaves budding viruses from infected cells.