PMB: Virology 13 Flashcards
Describe the functioning requirements of viruses
Viruses are incapable of independent metabolism. They require a host to grow.
Although they have their own set of genes the enzymes required for proper metabolic functioning are not encoded in them. Instead they require the hosts enzymes for profileration/ functioning
What is the size of viruses genomes?
Small. there physical size is small too
What is the genome composition of viruses like?
- Different bacteria have different genetic material. Some have:
- Double stranded DNA
- Double stranded RNA
- Single stranded DNA
- Single stranded RNA
- The genetic material is contained in the virus and there is surrounding material to keep everything together: a protein coat and outer lipid membrane
- Where do viral energy sources come from and what might the energy be required for?
- What is the appearance of bacteria?
- What genes do viruses require?
- The host organism for processed e.g. replication
- Symmetrical
- Although the majority of the genes required fo replication are contained within the hosts genome, the virus contains some specific genes too/ E.g. Reverse transcriptase in HIV requied to prodcue DNA from an RNA template
What are host organisms for viruses? Explain
- Viruses have limited range of host organisms and often only one species can be infected.
- This is because they have a limited number of genes which reduces potenital for diversity
What are potential routes of infection and examples of viruses that infect in these ways?
Viruses have specific means of infection. Generally linked to site of infection and where the virus proliferates. Knowledge of this can be used to control the virus
- Areosal e.g Measles
- Direct contact e.g. STI (HIV)
- Oral-faecal route e.g. GI tract viruses (norovirus)
- Blood e.g. Hepatisis B and Rabies
- Insect bites e.g. Dengue fever
What factors are required for viral infection?
- Corrcet mode of infection
- Correct biotic conditions e.g.
- Temperature range
- Humidity levels
- Sunlight (UV) levels
- Contact with the host is required
- Contact must also be with the correct tissue e.g. Influenza A needs to contact with epithelial tissue
- Recoginition of the host by the virus must also occur. This is usually through glycoproteins recognizing cell surface receptors on the host organism
Describe the steps that take place in viral repliacation
- Mechanism of viral replication wil vary depending on the virus involved (e.g. DNA vs RNA virus)
- Once the virus comes into contact with the host cell it is engulfed into the cell
- The viral coat (capsid) is removed
- The genome/ viral genetic material can then be transported to the nucleus -certainly for DNA virsues, however this may have the reverse transcription step in RNA viruses
- Expression of viral genes can begin
- Viral genome is replicated
- Release of genome from the nucleus
- Coating of virla genome tp form new mature virus
- Release of viral particle out of host cell
- This may be non-fatal or the virus may cause cell lysis of the host cell killing it
What is virus taxonomy?
What does it do?
- Helps identify relationships between different viruses
- Classes virsues
- Viruses not just classed on DNA/RNA and single/ double stranded but also associated with plants, animals, fungi, bacteria. Groups are split into further classes
- What is an example of a non-tissue specific virus?
- What are tissues which can be infected?
- What is common in this virus
- What are the symptoms?
- Human Cytomegalosvirus (HMCV)
- Mainly the salivary glands and leucocytes
- Long latent period as with all herpesviridae
- Most healthy individuals are asymptomatic. People who are imunocompromised are more likely have problems:
- Colitis
- Increased susceptibility to other symptoms
What can HMCV cause?
- HMCV is the most common cause for retinitis and blindness in those with HIV
In neotates is can cause cogenital abnormalities
What is the treatment for HMCV?
- No vaccine available
- Antiviral medication e.g. ganciclovir
Describe the treatment using ganciclovir
- It is a nuceloside analogue of 2–deoxyuanosine
- Using an analouge of dGTP causes competivie inhibition of the hosts DNA ploymerase. This in turn inhibits viral DNA repliacation
What can viruses cause incread suspetibility too?
Some virsues are associated with cancer. Increases likelyhood of getting it
- Epstein-Barr Virus (EBV) nasopharyngeal carcinoma
- Hepatitis B (Hep B)
- hepatocellular carcinoma
- Hepatitis C (Hep C)
- hepatocellular carcinoma
- Human Papillomavirus (HPV)
- cervical cancer
- Herpes virus
- Kaposi’s sarcoma
- Human T-lymphotropic virus Type 1 (HTLV-1)
- adult T cell leukaemia
- Merkel cell polyomavirus (MCPyV)
- Merkel cell carcinoma (skin)
- What causes the spread of ZIKA
- How long last for?
- What else does this species spread?
- What are symptoms/ problemS?
- aedes aegypti mosquito
- 2-7 days
- Yellow fever virus, dengue fever, Chikungunya, mayaro virus
- neonatal malformations e.g. small head size at birth
- Learning difficulties, hearing and visual problems
