Hep B vaccination Flashcards
1
Q
What is HBV?
A
- Hepatitis B Virus (HBV) is a DNA virus that primary infects the liver.
- Can lead to acute or chronic hepatitis, cirrhosis, and hepatocellular carcinoma.
2
Q
What is the primary target cell of HBV?
A
Hepatocytes.
3
Q
How is HBV transmitted?
A
- Contact with the blood, semen, or other body fluids of an infected person.
- Common routes include mother to child during birth, unsafe injections, and sexual contact.
4
Q
How does HBV enter a hepatocyte?
A
- First low affinity binding with heparan sulfate proteoglycans (HSPGs), bringing it closer to the hepatocyte cell.
- Then high affinity binding to NTCP receptor, and is endocytosed into the cell.
5
Q
What happens to the HBV envelope post-endocytosis?
A
- It merges with endosomal membrane, releasing the nucleocapsid into the cytoplasm.
6
Q
What is a capsid or nucleocapsid in the context of HBV?
A
A protein shell that encloses the viral DNA, made up of multiple core antigens.
7
Q
What type of DNA does HBV have?
A
Relaxed circular DNA (rcDNA) that is partially double-stranded.
8
Q
How does the HBV rcDNA get into the hepatocyte nucleus?
A
The nucleocapsid docks at the nuclear pore complex and releases the rcDNA into the nucleus.
9
Q
Why is it called “relaxed circular DNA”?
A
- It’s a covalently closed loop that doesn’t form a tight circle but has relaxed structure.
- Also partially double-stranded, with one complete strand and one incomplete strand.
10
Q
What is the different between endosomes and endocytotic vesicles?
A
- Endosome is a membrame bound compartment inside eukaryotic cells - involved in sorting, recycling, and degradation of endocytosed material.
- Endocytotic vesicles are the initial vesicles that form when material is endocytosed, which later fuse with or mature into endosomes.
11
Q
How do ALT and AST levels relate to liver damage?
A
- ALT (alanine aminotransferase) - predominantly in the liver.
- AST (aspartate aminotransferase) - found in the liver and other organs, like the heart, muscles and kidneys.
- Elevated levels in the blood suggest hepatocyte injury or damage, as they leak into the bloodstream when hepatocytes are damaged.
12
Q
Describe the structure of the HBV?
A
- Outermost envelope - a lipid bilayer associated proteins include Large (L), M and S proteins, giving rise to the Hepatitis B surface antigen (HBsAg).
- Nucleocapsid - made up of Hepatitis B core antigens (HBcAg). Inside is the HBV genome.
- Contains a relaxed circular DNA (rcDNA)
Hbe antigens in-between the envelope and nuclecapsid also. - Codes for an X protein (HBx) - initiates and maintaines HBV replication and modulates pathways to enhance viral transcription.
13
Q
Why are multiple shots given for the HBV vaccine?
A
- First short is a primer.
- Second is form memory cells.
- Third and fourth ensure there is wide pool of immune cells and memory cells to fight off and infection robustly.
14
Q
What is a chronic carrier of HBV?
A
- Infected for more than 6 months is a chronic carrier.
- Posing transmission risks.
- At risk for liver complications.
15
Q
After HBV’s entry into hepatocytes, what genetic material is released?
A
Relaxed circular DNA (rcDNA).
16
Q
What does rcDNA convert into within the hepatocyte nucleus?
A
Covalently closed circular DNA (cccDNA).
17
Q
What role does cccDNA play in the HBV life cycle?
A
Serves as a template for viral mRNA synthesis.
18
Q
How does HBV replicate its genome?
A
Pregenomic RNA (pgRNA) is reverse transcribed into rcDNA using the viral reverse transcriptase enzyme.
19
Q
How are mature HBV virions released from the cell?
A
Virions are enveloped by budding into the ER, transported, and then released from the cell.
19
Q
Describe the assembly and maturation of HBV.
A
- PgRNA and reverse transcriptase are packaged into viral core particles.
- Inside, pgRNA is reverse transcribed to mature the virion.
20
Q
What makes HBV eradication challenging in chronic infections?
A
The persistence of cccDNA in the nucleus serves as a long-lasting reservoir.
21
Q
Key risks for dental teams regarding HBV?
A
- Contaminated sharps
- Blood and saliva contamination of open wounds.
- Spraying of blood and saliva onto open wounds or mucuous membranes.
*
22
Q
What can increase the risk of HBV transmission during dental procedures?
A
*Not adhering to strict infection control (Sterilisation and disinfection guidelines).
*Needlestick injuries - accidental punctures with needles or sharp instruments.
*Improper handling of sharps.
*Not using PPE.
*Not being vaccinated.
*Treating patients with high HBV levels without realising.
*Cross contamination risk of using the same vials for multiple patients.
23
Q
What does innoculation refer to?
A
- Refers to the introduction of a substance, especially antigens like vaccines or pathogens.
24
How can dental professionals prevent HBV transmission?
* Vaccination against HBV
* Proper use of PPE (gloves, masks, eyewear, gowns)
* Adherence to hand hygiene protocols
* Safe handling and disposal of sharps
* Strict sterilization and disinfection procedures.
25
What are the methods by which the antigenicity (or the ability of HBV to evoke an immune response) can be neutralized or eliminated?
i.e. What methods or processes can reduce or eliminate the ability of the Hepatitis B virus (HBV) to stimulate an immune response?
Definition: The ability of HBV to provoke an immune response.
Methods of Destruction:
* Dry heat: Expose to 160°C-170°C for an hour.
* Chemicals: Formaldehyde can denature viral proteins.
* pH: Extreme levels denature viral proteins.
Note: These methods primarily affect the virus's ability to be recognized by the immune system.
*Autoclaving uses high temperature (around 120 degrees celsius) and high pressure (about above 15-20psi above atmospheric pressure) for sterilisation.
26
What are the ways in which infectivity are destroyed of HBV?
Which methods are effective in deactivating the Hepatitis B virus, preventing it from causing infection?
Definition: The ability of HBV to infect host cells.
Methods of Destruction:
** Heat:
* Autoclaving: High-pressure steam at 121°C for 15-20 mins.
* Boiling: Prolonged boiling.
**Chemicals:
* Bleach (Sodium Hypochlorite)
* Glutaraldehyde
* Alcohol (Ethanol or Isopropanol)
* Hydrogen Peroxide
**Radiation: Ultraviolet (UV) light damages viral nucleic acids.
**Desiccation: Drying out (Note: HBV can remain viable for up to a week in certain conditions).
27
What is the most effective way to prevent the transmission of HBV?
* Vaccination: HBV vaccine provides over 90% protection to individuals who complete the series of shots.
28
What are the two methods used to produce the surface antigen of HBV (HBsAg)?
**Plasma derived vaccines (for HbsAG production):
*Derived from plasma of donors with high HBsAg levels.
* Plasma is treated and purified.
* Ensures removal/inactivation of live HBV and contaminants.
* 22nm particles purified to be used as immunoglobulin which are non-infectious.
**Recombinant DNA Technology (for HBsAg production):
* Uses genetically modified yeast cells.
* DNA segment for HBsAg is inserted into yeast.
* Yeast produces HBsAg, harvested and purified.
* No risk of contamination with live HBV or other pathogens.
* 22nm particles formed to stimulate an immune response without causing an infection.
29
Acute Infection Markers?
* HBsAg: Positive
* Anti-HBs: Negative
* Anti-HBc IgM: Positive
* Anti-HBc IgG: May or may not be present
* HBeAg: Positive (high infectivity)
* Anti-HBe: Negative
30
Window Period (infection is resolving) Markers?
* HBsAg: Becomes negative
* Anti-HBs: Not yet detectable
* Anti-HBc IgM: Decreasing
* Anti-HBc IgG: Increasing
* HBeAg: Becomes negative
* Anti-HBe: Appears and increases
31
Markers for Immunity due to Past Infection?
* HBsAg: Negative
* Anti-HBs: Positive
* Anti-HBc IgM: Negative
* Anti-HBc IgG: Positive
* HBeAg: Negative
* Anti-HBe: Positive
32
Markers for Vaccinated Immunity?
* HBsAg: Negative
* Anti-HBs: Positive
* Anti-HBc (both IgM and IgG): Negative
* HBeAg: Negative
* Anti-HBe: Negative
33
Markers for Chronic HBV Infection?
* HBsAg: Positive (for more than 6 months)
* Anti-HBs: Negative
* Anti-HBc IgG: Positive
* HBeAg: Can be positive or negative
* Anti-HBe: Depends on HBeAg status
34
What are the symptoms of hepatitis B?
a. Asymptomatic
b. Nausea
c. Vomiting
d. Anorexia
e. Diarrhoea
f. Headache
g. Jaundice
35
What are the acute complications of hepatitis B and what does it mean about the patient in terms of risk level?
* Fulminant Hep B
* Death (rare)
* Most adults will clear the HBV after an acute infection. A small percentage (less than 5%) will not clear the infection and develop chronic Hep B.
* Chronic risk is higher for children.
36
When does chronic infection occur for hepatitis B and what is the incubation period?
a. Newborns/infants – Babies infected at birth or during early childhood are at highest risk for developing hep B. Around 90% of infected infants (those infected from their mothers around the time of birth) will develop a chronic infection.
b. Children (1-5 years old) - About 20-50% of children infected between the ages of 1 to 5 years will progress to chronic infection.
c. Adults - only about 5% of newly infected adults developing chronic hepatitis B. (approximately 95%) of adults will clear the infection on their own and become immune to future hepatitis B infections.
d. Incubation period – Refers to the time from exposure to the virus until symptoms begin.
i. Typically 1.5-6months (45-180 days), with an average of 60-90 days.
37
What is the different ways virus can enter your body to cause a disease?
* Respiratory transmission.
* Direct contact
* Blood-borne transmission – By parenteral (blood-to-blood) exposure to blood or other infected fluids.
* Sexual contact
* Vertical transmission – transmission from mother to child during childbirth (perinatal).
* Horizontal transmission – transmission from children, typically through blood or bodily fluids.
38
What is tropism?
a. It refers to the specificity of a virus to a particular host cell.
b. For example, HBV virus has tropism to hepatocytes, by binding to a specific NTCP receptor on the membrane of hepatocyte cells.
39
What does lysis cause to the liver?
**Lysis of liver due to HBV can lead to:
b. Release of enzymes – AST (Aspartate transaminase), ALT (alanine transaminase), elevated levels indicate liver damage.
c. Impaired liver function - Hepatocyte lysis can lead to jaundice, coagulation issues, and metabolic imbalances due to compromised liver functions.
d. Inflammation and scarring - Liver cell lysis triggers inflammation, leading to fibrosis and potentially progressing to cirrhosis, which severely affects liver function.
e. Potential liver failure - Significant liver cell damage and inability to regenerate can lead to acute liver failure, a life-threatening condition.
f. Increased risk for liver cancer - Chronic inflammation and regeneration due to hepatocyte lysis elevate the risk for hepatocellular carcinoma.
40
How long can HBV last on a surface for?
Stable on environmental surfaces for at least 7 days.
41
What is the nomenclature of the antigens when describing?
HbsAg (virus, region of virus, type of molecule)
42
What are the specific hepatitis B core antibodies called?
**Referred to as anti-HBc antibodies. There are two main types:
b. IgM anti-HBc – first antibody to appear after infection. Indicates recent or acute HBV infection.
c. IgG anti-HBc – After initial period IgM decrease and IgG is detectable.
* Presence of IgG and absence of IgM typically indicates past HBV infection.
* If present with other markers like HBsAG, can indicate chronic infection.
43
Following an HBV vaccination course, what would be done?
a. Sereological tests for HBV immunity are to be carried out.
b. Occupational health visit >6 months after vaccination course finishes.
44
What are serological tests?
They are the measurement of several HBV-specific antigens and antibodies.
45
What is ELISA and how does it work?
Enzyme linked immunosorbent Assay – uses enzymes to detect the presence of antigens or antibodies in a sample.
46
What is sequencing?
Refers to the process of determining the precise order of nucleotides within a DNA molecule of a virus.
47
What antibody levels are considered protective and non-protective?
a. Protective - Antibody levels >= 10 international units/litre.
b. Not protective – antibody levels < 10 IU/L.
