Viruses

Question 1

RSV General Characteristics

Answer 1

• Paramyxoviridae Pneumovirus
• negative ssRNA
• Helical
• Enveloped

Question 2

RSV - how does it replicate?

Answer 2

Since it is a negative ssRNA virus, RSV must bring its own RNA-dependent RNA polymerase (this is not found in host cells).

It must then transcribe its genome to mRNA for viral protein synthesis and to positive strands to serve as template for genome replication (i.e., creation of more negative strands).

Question 3

RSV - how does it cause wheezing?

Answer 3

RSV has a tropism for bronchial epithelial cells.

RSV is cytotoxic for ciliated epithelial cells → necrosis and edema in cilitated epithelial cells → collapse and blockage of small diameter bronchioles, w/ air trapping distally → wheezing

Question 4

HIV General Characteristics

Answer 4

• Retroviridae lentivirus
• +ss diploid RNA virus
• Icosehedral nucleocapsid
• Enveloped

Question 5

HIV life cycle

Answer 5

gp120 binds CD4 receptor on CD4+ T cells → conformational change → gp41 binding CCR-5 → gp41 mb penetration → HIV virion and host cell membrane fusion → entry of viral genome into host cell cytoplasm → viral RNA reverse transcribed to viral ds DNA (reverse transcriptase = RNA-dependent DNA polymerase)** → viral DNA incorporation into host DNA → activation of viral DNA replication (or latency) → new capsid formation/mature virion assembly → budding and/or release**

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Question 6

Influenza** **General Characteristics

Answer 6

• Orthroxymyxoviridae
• negative ssRNA
• Helical nucleocapsid
• Enveloped
• Spherical & Segmented genome (8 segments)