Week 6 - Blood Borne Viruses Flashcards
What cell does HIV infect?
-CD4+ T Lymphocyte
Where does HIV replicate?
-CD4+ T lymphocyte
Why does HIV cause immunosuppression?
-Destroys CD4+ t lymphocytes so the immune system is reduced
What is the average life expectancy of a person with HIV?
-77 years
How does the free virus infect cells?
- Free virus binds to CD4+ on Th lymphocyte and with the help of co-stimulatory molecules fuses with the cell
- Virus penetrates cell membrane and empties viral contents into cell
What happens once HIV has infected a cell to lead to replication?
- Reverse transcription of ssRNA to dsDNA by reverse transcriptase
- Viral DNA integrated with cellular DNA by integrase
- Infected cell division results in viral protein production
- Viral proteins come together and an immature virus pushes out of cell becoming enveloped in cell membrane
- Maturation and infection of new cell
How is HIV transmitted?
- Sexual -> vaginal, anal and oral
- Sharing injecting equiptment
- Vertical transmission
- Medical procedures
Explain the relationship between viral load and CD4+ cell count throughout the disease progression
1) Initially acute infection and seroconversion -> CD4+ count and viral count high -> body attempts ab response but it is not enough to clear the infection -> Viral load decreased but not cleared -> acute infection resolves
2) Latent infection lasts 2-10 years with a gradual decline of CD4+ and a slow rise of viral load
3) Symptomatic infection occurs as viral load rises
4) Severe infection/AIDs as CD4+ count diminished and viral load very high
How does the acute infection in HIV present?
- Flu-like illness
- Fever, malaise, vomiting, sores
How does the symptomatic infection of HIV present?
- Pneumonias and candida infections begin to appear
- Increased susceptibility to yeasts, mould and protozoa
Name some AIDs defining illnesses
- Kaposi’s sarcoma
- PCP
- TB
- Toxoplasmosis
- Cryptococcus
How is HIV diagnosed?
-Blood test subjected to HIV antigen/antibody tests 4-6 weeks after possible exposure
How is HIV treated?
- Highly active antiretroviral therapy -> combination of three drugs to prevent resistance developing to one drug and that virus replicating
- HAART drugs target budding, fusion or DNA rep
How is Hep B transmitted?
-Blood, sexual, vertical
What is the incubation for Hep B?
-6 weeks-6 months
What proportion of hep B infections develop into chronic disease?
-6-10%
What are common consequences of chronic hep B infections?
- Cirrhosis
- Hepatocellular carcinoma
How does acute Hep B infection present?
- Jaundice
- Fatigue
- Abdo pain, N+V
- Arthalgia
Describe the features of LFTs in hep B infections
-Increased AST and ALT
What proportion of Hep B infections go on to fulminant hepatic failure?
-1%
How is hep B prevented?
- Vaccination with Hep B surface antigen in 3 doses and boosters
- Check for hep B surface antibody
How is Hep B treated?
-Antiviral medication in chronic disease
How does hep C differ from hep B?
-8-% progress to chronic infections in hepatits C
Between HIC, Hep B and Hep C, which is the most prevalent world wide?
-Hep B
What does multiple infections at multiple sites indicate in a patient?
-Immuno suppression
How does TB present?
-Cough, weightloss, Fever, night sweats, haemoptysis, chest pain, fatigue
How is TB diagnosed?
- Tubercillin Skin test
- Interferon gamma release assays
What type of organism is pneumocystis jirovecii?
-Fungus
How does PJP present?
-Fever, dry cough, SoB and fatigue
How is PCP diagnosed?
-Broncholavage and staining
Persistence of what antigen after 6 months shows chronic hepatitis B infection?
-Surface antigen
Which antibody is present for life after a hepatitis infection?
-Core antibody IgG
Presence of which antigen in hepatits B is the infective stage?
-e-antigen
What type of virus is HIV?
-Retrovirus
