Lecture 7.2 - Blood borne viruses - Human Immunodeficiency Virus (HIV)

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Questions and Answers

What is the estimated number of people living with HIV in the African region in 2022?

35.6 million

25.6 million (correct)

20.6 million

30.6 million

What percentage of people living with HIV in the UK in 2022 were infected through IV drug use?

1.2%

1.5%

2.2%

1.8% (correct)

What is the primary mechanism of HIV transmission?

Airborne transmission

Vector-borne transmission

Vertical transmission from mother to baby

Contact of infected bodily fluids with mucosal tissue/blood (correct)

What is the term for when a person with HIV has a sustained undetectable viral load for 6 months, making HIV untransmittable?

U=U Signup and view all the answers

What is the primary component of the HIV virus that is detected in diagnostic tests?

HIV antigen (Ag) - viral capsid protein p24 Signup and view all the answers

What is the estimated percentage of people over 65 years old who were detected with HIV late in the UK?

66% Signup and view all the answers

What is the primary consequence of late detection of HIV infection?

Worse prognosis (x10 risk of death in 1st year) Signup and view all the answers

What is the primary factor affecting HIV transmission during sexual intercourse?

Viral level (viral load) in blood Signup and view all the answers

What is the primary benefit of using PCR blood tests in HIV diagnosis?

High sensitivity and detection of very early infection Signup and view all the answers

Which of the following is NOT a reason to offer HIV testing to a patient?

Routine health checkup Signup and view all the answers

What is the primary goal of HIV therapy?

Achieve undetectable HIV viral load Signup and view all the answers

Why is it recommended to use three or more antiretroviral therapy (ART) drugs in HIV treatment?

To prevent the development of resistance to individual drugs Signup and view all the answers

What is the purpose of post-exposure prophylaxis (PEP)?

To prevent HIV infection after potential exposure Signup and view all the answers

What is a strategy for preventing the transmission of HIV from mother to child?

Testing and treatment of the mother Signup and view all the answers

What is the purpose of male circumcision in HIV prevention?

To reduce the risk of HIV transmission during sexual intercourse Signup and view all the answers

What is the benefit of using pre-exposure prophylaxis (PrEP) in HIV prevention?

Reduces the risk of HIV transmission during sexual intercourse Signup and view all the answers

What is a potential ethical dilemma in HIV care?

Maintaining patient confidentiality vs. protecting the health of sexual contacts Signup and view all the answers

What is a future direction in HIV therapy?

Use of haematopoietic stem cell transplantation (HSCT) to cure HIV Signup and view all the answers

Study Notes

HIV Diagnosis and Testing

Appear at 3-12 weeks and persist for life
Current tests detect both Ag and Ab, with results available on the same day, but may yield false negative results
Blood tests (PCR) detect HIV nucleic acid, are highly sensitive, and detect very early infection (few days), used for follow-up/treatment response
"Rapid" tests are low-cost, take < 1 hour, and detect HIV antibody, with options for blood (finger-prick), oral (saliva), in-home, and postal testing

Who Should be Tested?

Patients presenting with:
- Respiratory: bacterial pneumonia/TB
- Neurology: meningitis/dementia
- Dermatology: severe psoriasis, recurrent/multi-dermal shingles
- Gastroenterology: Chronic diarrhoea/weight loss
- Haematology: any unexplained blood abnormality
- Oncology: lymphoma, anal cancer
- Gynaecology: cervical intraepithelial neoplasia (CIN)
- Sexually transmitted diseases: Hep B/Hep C

HIV Therapy

Aims:
- Undetectable HIV viral load
- Reconstitute CD4 count/immune system
- Reduce risk of transmission
- Good quality of life (low side effects, compliance)
- Normalise lifespan
Targets:
- Post-attachment inhibitors
- Fusion inhibitors
- Reverse transcriptase inhibitors
- Integrase inhibitors
- Protease inhibitors

Why Give 3 or More ART?

Millions of rounds of viral replication each day
Virus mutates (changes/adapts) every 2-3 rounds
Resistance to drugs can develop in days
1 drug - resistance develops quickly
3 drugs - harder to develop resistance
Patient must keep taking drugs

Considerations for Exposure to HIV

Emergency anti-HIV medicine called post-exposure prophylaxis (PAP) may stop individuals becoming infected if started within 72 hours of possible exposure
An early diagnosis means treatment can start sooner, improving the chances of controlling the virus, reducing the risk of becoming unwell, and reducing the chance of passing the virus on to others
Both positive and negative HIV tests may need to be repeated 1 to 3 months after potential exposure to HIV infection (window period)

Strategies for Prevention of HIV

Education (understanding of spread/control, reduce stigma)
Increase condom usage
Prevention of mother-to-child transmission (testing)
Increase testing
Needle and syringe programme (IV drug users)
Male circumcision
Post-exposure prophylaxis (PEP)
Pre-exposure prophylaxis (PrEP) for people at high risk of HIV infection
Development of vaccine(s)

The Good News

Decline in new diagnoses in homosexual men
Decline in new diagnoses in Black African heterosexuals in the UK
Decline in new HIV diagnoses, AIDS, and deaths
Reduction in time to start treatment

Future Therapies

Use of haematopoietic stem cell transplantation (HSCT) with absence of surface expression of the CCR5

Ethical Dilemmas in HIV

Psychological impact of diagnosis
Dealing with stigma
Patient confidentiality vs. health of mother, unborn child, sexual contact, older child, and patients/staff at workplace

Global Distribution of HIV

The vast majority of people with HIV are in low and middle-income countries
In 2022, there were 25.6 million people with HIV in the African region, 3.8 million in the Americas, 3.9 million in the South East Asian region, and 3.0 million in the European region

Prevalence of HIV in the UK

An estimated 102,168 people were living with HIV in the UK in 2022, including undiagnosed cases
Breakdown by transmission route:
- Homosexual men: 46.9%
- Heterosexuals: 48.6%
- IV drug use: 1.8%
- Vertical transmission: 1.8%

Human Immunodeficiency Virus (HIV)

Human immunodeficiency virus (HIV-1 and HIV-2)
Has its own reverse transcriptase to convert RNA into DNA
Retrovirus ("backwards") with ssRNA, DNA, ssRNA
Infects cells with CD4
Surface receptor: T-helper lymphocytes, monocytes/macrophages
HIV replicates inside cells, spreading to/infecting more cells

Replication of HIV

HIV replicates inside cells, spreading to/infecting more cells

Transmission

Contact of infected bodily fluids with mucosal tissue/blood:
- Unprotected sexual intercourse (anal/vaginal)
- IV drug users (sharing needles)
Medical procedures:
- Blood/blood-products transfusion
- Surgery
- Needlestick injury
- Skin grafts, organ transplant
Vertical transmission:
- Mother to baby (during pregnancy, at the time of birth, breast milk)

Factors Affecting HIV Transmission

Type of exposure:
- Type of sexual act (use of condoms)
- Transfusion, needlestick, mucous membrane
- Other STI (inflammation of genital tract)
- Sexual assault
Viral level (viral load) in blood:
- U=U -> sustained undetectable viral load (VL) for 6/12 means that HIV is untransmittable

Living with HIV in the UK

Life expectancy and quality of life now excellent with:
- Early detection and treatment
- Adherence to treatment
- Healthy living (avoiding smoking, alcohol, and metabolic problems)
Late detection = worse prognosis (x10 risk of death in 1st year)
66% of over 65-year-olds detected late

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Description

This quiz covers the different types of tests used to detect HIV, including current tests, blood tests, and rapid tests. Understand the differences and limitations of each test.