Session 8 - Blood Borne Infections (HIV and Hepatitis) Flashcards
What are some examples of blood borne infections?
- HIV
- Hepatitis B
- Hepatitis C
What is the viral structure of HIV?
It is a retrovirus.
A retrovirus converts ssRNA into ssDNA in the host, but then converts it back to ssRNA again.
What does the HIV virus do?
Infects cells with the CD4 surface receptor.
What cells have CD4 surface receptors?
- T-helper lymphocytes
- Monocytes and macrophages
What does HIV do inside the host cells?
Replicates inside the cell, leading to:
- destruction of the cell
- activation of the inflammation response around the cells
- the spread and infection of more cells
How does HIV replicate inside the host cell?
Virus binds to the cell and fuses to it.
It’s genetic contents are emptied into the cell where the ssRNA is converted into dsDNA.
The dsDNA is integrated into the genetic material of the cell, where they can be replicated and transcribed in newer cells.
Viral protein chains come together and bud off the cell, forming an immature virus that then matures into a full fledged HIV.
How is HIV transmitted?
Transmitted from the contact of infected bodily fluids with mucosal tisues/ blood/ broken skin.
How can HIV be spread from person to person?
- Sexual contact
- Transfusion of bodily fluids (blood)
- Contaminated needles
- Perinatal transmission
- transplacental
- during delivery through an infected birth canal
- as a result of ingestion of breast milk carrying virus
What is the progression of infection of HIV?
- Primary infection
- Latent infection
- Symptomatic infection
- Severe infection (AIDS)
What is the primary infection of HIV and it’s affects on viral load and CD4 count?
Initial introduction to HIV where the viral load goes up dramatically.
Virus makes it home in the lymph nodes where it can then access the bloodstream.
Patient will feel unwell at this point.
CD4 count will temporarily drop, but shall recover in the primary phase.
What is the latent infection of HIV?
Can last from months to years.
Virus starts out at a very low point and begins to replicate, evading the immune system.
CD4 count will gradually start to fall.
What is the symptomatic infection of HIV?
Where patients start to notice problems.
May get presistent infections but not take much notice of it.
CD4 count is approximately <350 cells/µL and decreasing.
What is the severe infection of HIV?
Becomes at risk of severe, life-threatening infections.
Patient also becomes severe risk for the development of AIDS.
CD4 count in <200 cells/µL.
What are the main symptoms of an acute HIV infection?
- Fever
- Weight loss
- Skin rash
- Mouth sores/ thrush
- Nausea and vomiting
What diagnostic tests are used to identify HIV?
- Blood tests
- Serology
- PCR
- Rapid testing
How does serology test for HIV?
Tests for HIV antigen and antibodies.
Can receive results on the same day.
Test can give out false negatives (if taken too early).
How does PCR test for HIV?
Detects HIV nucleic acid and is highly sensitive.
Is expensive and can take longer for results (1 week).
Highly accurate.
How does rapid testing test for HIV?
Low cost testing that takes under an hour.
Uses a finger-prick or oral in home tests.
Detects the HIV antibody.
May get false positive result, but if negative, it is accurate.
What are some infections patients may present with that may be indicative of HIV?
Resp: bacterial pneumonia/ TB
Neuro: meningitis
Derm: psoriasis/ recurrent or multi-dermal shingles
Gastro: chronic diarrhoea
Gynae: cervical intrapithelial neoplasia (CIN)
Any STI/ Hep B/ Hep C
Whar are the aims of HIV treatment?
- Undetectable HIV viral load
- Increase CD4 count
- Reduce general inflammation
- Reduce risk of transmission
- Improve quality of life
What drugs can be used to treat HIV?
Anti-retroviral drugs (ARVs)
How do ARVs work and what mechanisms do they inhibit?
ARVs target enzymes that are vital in HIV’s movement into the cell and replication. These drugs inhibit the following mechanisms:
- Inhibition of reverse transcriptase enzyme, preventing ssRNA from being converted to dsDNA
- Inhibition of integrase enzyme, preventing dsDNA from integrating with cell DNA
- Inhibition of protease enzyme to stop protein chains from becoming a functioning virus
How many and which ARVs are used?
Normally 3 ARV drugs are used.
2 nucleoside reverse transcriptase inhibitors (NRTIs)
And 1 of the following:
- NRTI
- Protease inhibitor
- Integrase inhibitor
Why are 3 ARV drugs used?
Virus replicates very quickly (millions of rounds of replication each day).
The virus can therefore mutate and may develop a resistance to a singular drug.
Using 3 drugs, it makes it harder for the virus to develop resistance.
How can HIV be prevented?
- Increase condom usage
- ARV treatment as prevention
- Post-exposure prophylaxis (giving an HIV -ve person drugs if they think they’ve been exposed to HIV)
- Pre-exposure prophylaxis (giving an HIV -ve person drugs to protect themselves - done if person is in a relationship with someone who is HIV +ve)
What is the hepatitis virus?
Hepatitis = inflammation of the liver.
Replication occurs specifically in hepatocytes, which can lead to fibrosis, leading to cirrhosis and liver cancer.
Causes the destruction of hepatocytes.
What is the viral structure of Hepatitis B?
Enveloped dsDNA virus.
What is the viral structure of Hepatitis C?
Enveloped ssRNA virus.
What are some symptoms of acute Hepatitis B?
- Jaundice
- Fatigue
- Abdominal pain
- Anorexia/ Nausea/ Vomiting
- Arthralgia (pain in a joint)
How is hepatitis B transmitted?
- Vertical transmission
- Sexual contact
- Contaminated needles
Is hepatitis B chronic or acute?
90% of Hepatitis B is acute, with the infection clearing in about 6 months.
<10% of Hepatitis B is chronic.
Chances of it becoming chronic increases if infected as a child.
How is hepatitis B tested for in a patient?
Using serology of the following antigens and antibodies:
- surface antigen and antibody (on the cell wall) HBsAg and HBsAb
- e-antigen and antibody HBeAg and HBeAb
- core antigen and antibody HBcAg and HBcAb
(all of these appear at different times during the course of the infection)
HBV DNA (PCR) is also tested.
What are the serological patterns of hepatitis B antigens and antibodies over the course of infection?
- Within 6 weeks: HBsAg is detected
- After 6 weeks: HBeAg (means Hep. B is highly infectious)
- After 2 months: HBcAb (IgM) is detected
- After 4 months: HBeAg is detected
- 6 months: HBsAb is detected (indicates recovery)
Core antibody: IgG persists for life and indicates previous hepatitis infection.
How does hepatits B become chronic?
Persistance of HBsAg after 6 months.
More likely to cause liver cirrhosis or hepatocellular carcinoma.
What is the treatment for chronic hepatitis B?
There is no cure.
Life long anti-virals are taken to suppress viral replication.
*Not required for everyone (‘inactive carriers’), this can be due to low viral load or lack of liver damage.
What measures are taken to prevent hepatitis B?
3 doses of a vaccine are given.
Boosters can also be given if required.
How does the hepatitis B vaccination work?
It is a vaccine of genetically engineered surface antigen (HBsAg) that gives you an artificial infection.
This encourages the surface antibody response (HBsAb) and allows for long-term protection.
What is the disease progression of hepatitis C?
Approximately 80% become chronically infected.
These patients are more likely to develop chronic liver disease/ cirrhosis, leading to:
- decompensated liver disease
- primary liver cancer
What are the symptoms of hepatitis C?
Majority of patients have no symptoms (asymptomatic.
Vague symptom may include:
- fatigue
- anorexia
- nausea
- abdominal pain
How is hepatitis C tested for in patients?
Serology:
- Anti-hep C antibody
Viral PCR:
- if positive, confirms an on-going or chronic infection
Is the anti-Hep C antibody only present during the course of infection?
No.
It is always present even if cured of infection.
And it is not protective, patients can get re-infected.
What is the treatment for hepatitis C?
Anti-viral drugs used.
Patients take them for 8-12 weeks.
90% success rate.
However, very expensive and patient can be re-infected.
What is the prevention method for hepatitis C?
There is no way to prevent hepatitis C, it should just be avoided.
