PARAMYXOVIRIDAE

• STRUCTURE: ss (-) RNA, enveloped.

  • Fusion Protein (F): Responsible for forming syncytia, multi-nucleated cells.

  • Hemagglutinin-Neuraminidase (HN): Single protein.

  • Has a Transcriptase, RNA-dependent RNA-Polymerase.

• REPLICATION: Entirely cytoplasmic.

  • Primary Transcription occurs, and the RNA genome is replicated.

  • Syncytia (via F-Protein) allow for cell-to-cell infections. Virion doesn't need to go outside of cell to infect neighboring cells.

• DETECTION: You can use hemadsorption (hemagglutination) to detect the cells, as they have the HN-Protein on their surface.

• GENERAL PATHOGENESIS:

  • Infection by respiratory tract. Mucosal IgA is more important than serum IgG in preventing infection.

  • Infection occur in late winter, early spring.

• PARAINFLUENZA VIRUS: (PARAMYXOVIRUS).

  • STRUCTURE: Four human serotypes. Types 1 and 3 are within the Paramyxovirus family, while types 2 and 4 are within the Rubivirus family.

    • Sendai Virus = Parainfluenza Type 1.

  • DIAGNOSIS: Culture. Detect by FA. Respiratory Panel available commercially can identify seven common respiratory viral pathogens.

  • MANIFESTATIONS: Infection often occurs in autumn.

    • Croup (Types 1 & 2): Laryngotracheobronchitis in young children is the Croup. Fever, cough, and respiratory distress due to bronchial obstruction.

      • Barking cough is seen.

      • Crop = obstruction of larynx in young children.

    • Type-3: Bronchiolitis in infants. Severity correlates to IgE levels, indicating an immunopathogenesis for the disease.

    • Parainfluenza may also be the cause of the common cold.

    • Only short-term immunity is acquired.

• MUMPS VIRUS: (PARAMYXOVIRUS).

  • STRUCTURE: Only one major serotype.

  • DIAGNOSIS: Culture, demonstrate hemadsorption, look for syncytia.

    • Will see multinucleated cells on cell culture.

  • MANIFESTATIONS: Generalized infection, with incubation period of 1-3 weeks.

    • Lifelong immunity is acquired.

    • Symptoms: Parotitis (parotid gland inflammation), Orchitis.

      • Infants may be subclinical due to maternal antibodies.

    • Complications:

      • Use to be most common cause of viral meningitis -- seen in the Winter and Spring (not Summer and Fall like Coxsackie A Virus).

      • May see pancreatitis or encephalitis.

• MEASLES VIRUS: (MORBILLIVIRUS).

  • STRUCTURE: Only one major serotype.

  • Related Diseases: Distemper in dogs, Rinderpest in cattle are also a part of this family.

  • DIAGNOSIS: Culture, serology.

    • Koplik's Spots on buccal mucosa.

    • Will see multinucleated cells on cell culture

  • MANIFESTATIONS: Generalized infection, with incubation period of 1-3 weeks.

    • Lifelong immunity is acquired.

    • Symptoms:

      • Early Symptoms: Fever, cough, coryza, conjunctivitis.

      • Late Symptoms: maculopapular rash.

      • Flat macules that coalesce to form large blotches, and fade in 5-6 days. Rash spreads from head, down to rest of body.

    • Severe Complications: Otitis media, viral or bacteria pneumonia which is possibly fatal.

      • Post-Infectious Encephalomyelitis: 1:1000 cases. 15% fatality rate. Appears to be an autoimmune pathogenesis. This is the most important complication.

      • Subacute Sclerosing Panencephalitis (SSPE): 1:1 million cases. Follows the acute measles by several years.

        • Patients afflicted with this lack antibodies against the measles-virus M-Protein. The virus is being produced without an envelope in these cases, and that results in this fatal complication.

      • Pneumonia occurs especially in developing countries where malnutrition is common. It can be fatal.

  • TREATMENT: Vitamin-A for infants. Passive immunity.

  • MMR VACCINE: Live-attenuated vaccine.

    • Primary dose at 12-15 months.

    • Booster shot in elementary school.

    • Vaccine should not be given to immunodeficient children -- except for HIV children, for which it is recommended.

• RESPIRATORY SYNCYTIAL VIRUS (RSV): (PNEUMOVIRUS)

  • STRUCTURE: Has a G-Protein and F-Protein, but lacks NA and HA activity.

  • DIAGNOSIS: FA, Respiratory Panel of viruses.

    • Will see multinucleated cells on cell culture.

  • MANIFESTATIONS: Acute infection, with incubation period of 3-5 days.

    • Only short-term immunity is acquired.

    • Serious respiratory infection in neonates (0 - 6 months). Only mild disease in older folks.

  • TREATMENT: Ribavirin, aerosolized, may have limited effectiveness, for hospitalized babies.

  • VACCINE: Passive immunization is available for infants at high risk.

• Newcastle Disease Virus (NDV): Avian virus, can produce conjunctivitis in humans.

• VESICULAR STOMATITIS VIRUS (VSV): Arbovirus causes disease in cattle and horses. Can cause mild disease in humans. Has been utilized as a model virus in research.

Category: Microbiology Notes