Blood Borne Viruses Flashcards
What are the three main blood bourne viruses?
Hepatitis B, Hepatitis C, and HIV
What type of virus is HBV?
Hepatitis B virus is a DNA virus from the family hepdnavirus (‘hep’ ‘dna’)
What type of virus is HCV?
Hepatitis C virus is an RNA virus, from the family flavivirus
What type of virus is HIV?
Retrovirus and is in the lentivirus sumfamily
What morphological feature do HBC, HCV, and HIV have in common?
All are enveloped viruses with a lipid outer surface (do not survive well in the environment or stresses such as desiccation)
What are the three methods of transmission for HBV, HCV, and HIV?
- Penetrative intercourse
- Contaminated blood from needles
- Vertical (including breast feeding)
NB all 3 viruses can transmit by any of these routes, lots of local variation in epidemiology
What is principal mode of transmission for HIV?
Sexual intercourse
What is principal mode of transmission for HCV?
Contaminated blood especially IV drug use
What is principal mode of transmission for HBV?
Vertical including breastfeeding
What blood component is tested for a BBV?
Serum, therefore send a clotted sample to the virology lab
What can the virology lab test for in a suspected BBV? (4)
Type of infection
Past or current
Acute or chronic
How much virus is circulating (infectivity)
What are theranostics?
Tests specifically done to guide treatment (monitor response to treatment, or drug resistance, or can look at genotype of hep C)
Which cells are damaged by HBV?
Hepatocytes (damage done by immune reaction not the virus)
ie if someone is immunosuppressed they will not have disease
What is the incubation period of HBV?
6 weeks to 6 months
Initial symptoms of HBV
Nonspecific fever and malaise (only half of acute infections cause symptoms)
Long term effects of chronic HBV infection?
Chronic active hepatitis
Cirrhosis
Hepatocellular carcinoma
What is HBsAg? What is it used for?
Hepatitis B surface antigen, used as diagnostic test for the virus as it is grossly over-produced
What is HBeAg?
E antigen is a soluble form of the core antigen of hepatitis B, the part of the virus that is inside the
surface antigen coat. And e antigen is important because it has a tolerogen effect
What is the toleragen effect of HBeAg?
The E antigen is a soluble form of the HBV core antigen
It can cross the placenta, causing teh foetus to recognise the e antigen as SELF.
Results in a clonal deletion of lymphocytes that recognise this antigen
Therefore, removes immune response to HBV and the baby gets a chronic infection
Chance of HBV being transmitted to baby if mother is +ve for HBsAg and not HBeAg?
<10%
Chance of HBV being transmitted to baby if mother is +ve for HBsAg AND HBeAg?
70-90% due to toleragen effect
What does HBsAg indicate?
Current infection
What does HB core antibody (IgG) indicate?
Past or present infection
if you’ve had Hep B, you’ll ALWAYS have IgG
What does HB core antigen (IgM) indicate
Infection in the past 6 months. Disappears after 6 months.
What does HB e antigen indicate?
HIGH INFECTIVITY and high grade infection.
What does anti-HbsAg indicate?
Immunity to infection (>10 MIU) either naturally or via vaccine
What does HBV DNA (quantitative) indicate?
Load test that determines response to treatment.
Difference between e antigen positive and e antigen negative infection?
e positive: very infectious and high grade, likely to develop chronic active hepatitis and HCC
e negative: low grade infection and low risk of transmission, not likely to develop symptoms. WILL MOST LIKELY HAVE e ANTIBODY PRESENT.
What vaccine is used for HBV?
Genetically modifed vaccine
Uses recombinent portein expressed in yeast and is the surface antigen protein
What groups are targeted for HBV vaccine in UK?
Neonates with HBV positive mums
Healthcare workers
Dialysis patients
Contacts of HBV cases
What treatment options are there for HBV? (3)
Lamivudine (aim is suppression of the virus not cure)
Interferon (aim is cure of high grade infection)
Liver transplant
What are the thernostic tests for HBV?
Lamivudine resistence
Viral load (HBV DNA)
What cells are damaged by HCV?
Hepatocytes by BOTH direct viral effects and immune reaction
How many genotypes does HCV have? Which ones are hard and easy to treat?
6 genotypes
Genotype 1 common in NI, poor response to treatment
Genotype 3, easier to treat
What are the symptoms of HCV in acute phase?
Asymptomatic (only 10% get symptoms in acute stage)
How many HCV cases become chronic?
70%!!
Health effects of chronic HCV
50% chronic active hepatitis
20% cirrhosis (decades after infection)
Around 2% a year get HCC
What does the HCV antibody indicate?
Past or present infection
What does HCV RNA (by PCR) indicate?
CURRENT infection
What does the HCV genotype marker indicate?
Guides treatment duration
Type 1=12 months
Type 3=6 months
What does it mean if patient is HCV antibody positive but HCV PCR negative?
Past infection
What does it mean if patient is HCV antibody positive and HCV PCR
Current infection
Treatments for HCV? (3)
Ribavirin (aim is cure)
Interferon (aim is cure)
Transplant (but it recurs in nearly 100% of cases)
What virus is treated with Ribavirn?
HCV
What virus is treated with Lamivudine?
HBV
What can theronostic assays be used for in HCV?
Genotype detection to guide treatment length
HCV RNA detection by PCR to guide response to treamtment
Which cells are infected by HIV?
Retrovirus which affects immune cells:
CD4 lymphocytes (T helpers) Macrophages
Two main subtypes of HIV?
HIV1 (most cases) and HIV2
How many cases of HIV in NI?
400 at the RVH
80 new cases a year
What two diseases are caused by HIV?
Primary HIV infection
AIDS
How long does it take to see a primary HIV infection post exposure?
10-25 days
Symptoms of primary HIV infection?
Glandular fever, lymphadenopathy, rash
Opportunistic infections in AIDS? (9)
Retinitis Encephalopathy Lymphoma TB CNS infection Bloody diarrhoea Oesophageal infection Pneumonia Meningitis
What opportunistic infection is caused by JC polyvirus?
Encephalopathy
What opportunistic infection is caused by EBV?
Lymphoma
What opportunistic infection is caused by Mycobacteria?
TB
What opportunistic infection is caused by Toxoplasma?
CNS infection
What opportunistic infection is caused by Cryptosporidia? (protozoa)
Bloody diarrhoea
What opportunistic infection is caused by Candida?
Oesophageal infection
What opportunistic infection is caused by pneumocystis? (fungi)
Pneumonia
What opportunistic infection is caused by Cryptococcus? (fungi)
Meningitis
What is the key test for HIV?
HIV antibody test
What approach is used for HIV testing?
4 assay approach to reduce risk of false positive
Therapy for HIV?
Anti-retroviral therapy (ART)
Aim is suppression not cure
What 3 drug classes are used together to treat HIV?
- Nucleoside reverse transcriptase inhibitors
- Non-nucleoside reverse transcriptase inhibitors
- Protease inhibitors
How can vertical HIV transmission be prevented? (3)
C-section
Anti retroviral therapy to mother and baby
Avoid breast feeding
Reduces transmission from 16% to 1%
3 theranostic assays used for HIV?
Viral load (response to treatment)
CD4 lymphocyte count (response to treatment)
Mutational analysis for drug resistance (sequencing viral genome)
Which BBVs have vaccine?
HBV only
Which BBVS have curative treatment?
HBV and HCV
Which BBVs have suppressive treatments?
HBV and HIV
For HCV, aim is cure
Post exposure prophylaxis for HBV?
Vaccine and IgG
Post exposure prophylaxis for HIV?
ART drugs for 6 weeks
Post-exposure prophylaxis for HCV?
None
What is the window period in virus diagnostic testing?
Period in which patient is infected but no antibodies have developed yet- risk of false negative
