Viruses Flashcards
What is the structure of a virus? Size?
Viral genome enclosed in capsid - protein shell
Capsomere - viral genome + capsid
10-300nm in size
What are the stages of viral replication
Adsorption - attachement of virus to cell by random collision, host cell receptors or eletrostatic
Penetration - fusion of the viral envelope and cell membrane
Capsid removal - capsid removed by host cell enzymes
Nucleic acid replication - most DNA viruses replicate in the nucleus by host cell enzymes to make mRNA and to replicate DNA
- DNA viruses produce intranuclear inclusions
Where do RNA viruses replicate?
Cytoplasm
Use reverse transcriptase to make DNA from RNA
How can vertical viral transmission occur
Mother to offspring
CMV
Rubella transplacental
What is the cellular response to virus infection
Cell shrinking
Rounding
Inclusion bodies
Formation of giant multi-nucleate cells
CEll death due to cytolysis or inhibtion of metabolism
What is latency?
Viral genome integrated into host DNA - does not replicat until a trigger occurs - e.g. HSV
What is persistence?
Virus replicates at very low rate
What is transofrmatoin
Virus initiates new cell properties which lead to teratogenic change
What is antigenic drift? Shift?
Drift - Minor changes in antigenic surface of viruses due to point mutation in viral genome
Antigenic shift - virus swaps whole segments of genome with reservoirs of different virus
What is seen in CMV on microscopy?
Cytoplasmic inclusions
Owl eye nuclear inclusion bodies
How can viral infection be diagnosed
Direct viral isolation
Serology - detection of antigen or antibody - compelemtn fixation measures reaction between viral antigen and specific antibody
ELISA
Radioimmunoassay
Reverse passive haemagglutination
Organ specific humoral responses detected in ocular fluid
PCR to detect genetic material via analysis of intraocular fluid or tissue
