Viral Pathogenicity Flashcards
Outcomes of virus infection of cell
Cell Death
- Cytolytic or cytocidal infection
Chronic Infection
- Continuous replication within cell but cell survives
Latency
- Virus is present but does not replicate or produce viral proteins. Infected virus always infected. Virus replication can be reactivated (e.g. herpes)
Transformation
- As virus infects cell, it disrupts reproduction and immortalises host cells; causes cancer (Epstein-barr virus)
How to identify rhinovirus-infected lung fibroblasts
Instead of a clean consistent sheet, there are shriveled up cells which make holes
How to identify syncitial virus infection
Infected cell sheets have giant multinucleate cells (syncitia)
How to identify influenza infected exfoliated/shedded respiratory epithelial cells
The cells have lost their cuboidal shape and look a lot more shrivelled up, dead or close to being dead
Cytolytic Infection
Viruses that kill the host cell
Housekeeping and Luxury functions of cells and how this is affected by chronic viruses
Housekeeping - Functions that are necessary for survival
Not affected by chronic viral infection
Luxury - Specialist functions of a cell
Affected by chronic viral infection
Primary and Secondary Viral infection (latency)
Primary infection is the first exposure to a latent virus
Infection usually has full body response (fever, etc.) Can last a few weeks
Secondary is the reactivation and replication in the host
Much more minor immune response, usually just cold sores on lips (herpes)
Lasts about a week
How does chicken pox work in latency
Stays in spinal cord; can reactivate as shingles (herpes zoster)
Cancers caused by different viruses
EBV - Lymphomas, nasopharyngeal carcinoma
Hep B, C - Hepatocellular carcinoma
HPV - Cancer of uterine cervix
How viruses can enter into host
Skin (Resistant if intact)
Mucosal surfaces (oro-, naso-pharynx, conjunctivae, genital tract) - [HIV]
Respiratory Tract
Gastrointestinal Tract (non-enveloped)
Placenta (from maternal bloodstream; causes congenital infection, might severely affect development)
How viruses spread within host
Local (cell-cell)
Lymphatics
Bloodstream (viraemia); HIV, Hep
Axonal Pathways (Herpies, Rabies)
Methods of viral shedding
Skin - vesicles Respiratory tract - Droplets GI Tract - saliva, faeces Urogenital tract - Urine, semen, female genital secretions Blood - HIV Breast Milk - HIV
Cytopathic Infection
Viruses that cause structural changes in host cells
