by Sean Elliott, MD

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    00:01 The paramyxoviridae viruses.

    00:04 The paramyxoviridae are very important viruses.

    00:08 They are large, enveloped, with a helical capsule, and they have a linear, single-stranded, negative-sense RNA genome.

    00:15 So again, if you remember anything about this particular family of virus, this is a negative-sense RNA virus, which means that it must carry, and it does, its own RNA-dependent RNA polymerase, the RDRP.

    00:29 You can see in a transmission electron micrograph in front of you a picture of one of the paramyxoviruses, and it's a very large shaped organism.

    00:39 There are many medically relevant species in this family, the paramyxoviridae.

    00:44 Measles virus, mumps virus, the human parainfluenza virus, cause of croup.

    00:49 Respiratory syncytial virus, a huge cause of bronchiolitis in children, and then the human metapneumovirus, which is very much -- almost like a combination of parainfluenza and respiratory syncytial virus.

    01:02 So, a whole bunch of nasties in this particular family.

    01:05 So, all of these viruses, the paramyxoviruses, have the same pathogenesis.

    01:11 . So they start with a two-step binding process.

    01:15 The first is attaching to their target salvia, a fusion protein, the F protein.

    01:21 And then there's a secondary fusion with the envelope of the virus and the cell membrane of the target cell.

    01:29 And then the capsid itself is released into the cell.

    01:32 Now, importantly, 1 cell can be be infected with or attacked by multiple of the paramyxoviruses, giving it the appearance of a multinucleated cell.

    01:43 It's just a whole bunch of viral capsids inside that cell.

    01:48 As that primary infection occurs, it's occurring with the epithelial cells of the upper respiratory tract.

    01:55 Kind of makes sense because all these have a respiratory droplet transmission, and so one breathes in the virus, they attack the upper respiratory tract, and one gets these viruses bound to the airway respiratory epithelium.

    02:09 In the case of measles and mumps, the first 2 that we'll talk about, there is then a secondary viremic spread, which accounts for the systemic manifestations of those 2 viruses.

    02:21 In the case of the parainfluenza, RSV, and human metapneumovirus, there is not a viremia.

    02:27 So they account for primarily respiratory symptoms.

    02:31 Here, we see an image of a multinucleated cell.

    02:36 This is an epithelial cell with the green arrow to make sure you can't miss it.

    02:39 But it has multiple capsids, multiple virion capsids inserted into its cytoplasm.

    02:46 Now, importantly, this whole family of cells are both sensitive to and inducers of interferon.

    02:54 So they almost self-stimulate to create even further impact through the effects of interferon.

    About the Lecture

    The lecture Paramyxoviruses by Sean Elliott, MD is from the course Viruses.

    Included Quiz Questions

    1. Human parainfluenza virus
    2. Measles virus
    3. Mumps virus
    4. Respiratory syncytial virus
    5. Human metapneumovirus
    1. RNA-dependent RNA polymerase
    2. RNA-independent RNA polymerase
    3. DNA-dependent RNA polymerase
    4. DNA-dependent DNA polymerase
    5. DNA-dependent RNA transcriptase

    Author of lecture Paramyxoviruses

     Sean Elliott, MD

    Sean Elliott, MD

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