Lecture 8 9

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Questions and Answers

What is the primary mode of human-to-human transmission of HIV?

Perinatal transmission

Transfusion of blood products

Sexual contact (correct)

Sharing needles

What CD4 cell count indicates a high risk of developing serious illnesses in individuals living with HIV?

Below 200 cells/ml (correct)

Above 500 cells/ml

Between 200 and 400 cells/ml

Below 500 cells/ml

During which time frame does a high virus titer in blood typically occur after HIV infection?

1-3 months

1-3 weeks (correct)

1-3 days

1-3 years

What is the term used to describe the enlargement of lymph nodes in advanced HIV infection?

Lymphadenopathy Signup and view all the answers

What does the acronym 'U=U' represent in the context of HIV?

Undetectable=Untransmittable Signup and view all the answers

Which type of therapy has been shown to lower the viral load and reduce HIV transmission risk?

Triple-drug antiretroviral therapy Signup and view all the answers

What is considered a long asymptomatic period for individuals infected with HIV?

1-15 years Signup and view all the answers

Which of the following is NOT a method of human-to-human transmission of HIV?

Airborne transmission Signup and view all the answers

What environmental factor is suggested to influence the pathogenesis of retroviruses like HIV?

Stress Signup and view all the answers

What is the percentage of new HIV infections attributed to blood transfusions?

3-5% Signup and view all the answers

What is the primary route of transmission for Hepatitis B?

Vertical transmission Signup and view all the answers

Which factor correlates with a high level of viral replication in Hepatitis B infections?

Presence of HBeAg Signup and view all the answers

What proportion of hepatitis B patients are undiagnosed in Malaysia?

9 out of 10 Signup and view all the answers

What is the minimum duration for which a person must have an undetectable viral load to be considered 'durably undetectable'?

Six months Signup and view all the answers

What does the presence of HBsAg indicate?

Current infection with Hepatitis B Signup and view all the answers

What type of genetic material does the Hepatitis B virus (HBV) contain?

Partially closed double-stranded DNA Signup and view all the answers

What is the likely outcome for babies born to HBsAg positive mothers if they receive appropriate treatment?

Reduction in vertical transmission risk Signup and view all the answers

What percentage of chronic hepatitis B patients are typically HBeAg negative?

Over 90% Signup and view all the answers

Which of the following transmission methods is NOT associated with the spread of Hepatitis B virus?

Insect bites Signup and view all the answers

What is indicated by the presence of Anti-HBc IgM antibody?

Infection within the last 6 months Signup and view all the answers

Which of the following is a soluble early antigen used in acute HBV detection?

HBeAg Signup and view all the answers

What percentage of acutely infected adults with Hepatitis B may become persistently infected?

10% Signup and view all the answers

What type of infection is characterized by asymptomatic subclinical infection in 70% of cases?

Chronic hepatitis B Signup and view all the answers

What is the implication of a Hep B DNA level greater than $10^5$ copies/mL?

Rapid viral replication and active infection Signup and view all the answers

What are the potential serious complications of chronic Hepatitis B infection?

Hepatocellular carcinoma and liver cirrhosis Signup and view all the answers

How does the presence of non-infectious particles of HBV affect the immune response?

Act as decoys for antibodies Signup and view all the answers

How many deaths annually are caused by chronic Hepatitis B infections globally?

500,000 Signup and view all the answers

Which of the following factors significantly increases the risk of perinatal transmission of Hepatitis B?

Mother is HBeAg positive Signup and view all the answers

Which marker indicates immunity acquired through natural infection or immunization?

Anti-HBs antibody Signup and view all the answers

What is the primary method through which liver damage occurs in HBV infection?

Immune clearance of infected hepatocytes by CD8+ T cells Signup and view all the answers

What role do viral reservoirs play in the context of HIV?

They allow the virus to remain dormant despite an undetectable viral load. Signup and view all the answers

What is the recommended vaccination schedule for the hepatitis B vaccine in Malaysia?

At birth, 2, 3, 5 months, and a booster at 18 months Signup and view all the answers

In viral replication, what intermediate does HBV utilize?

An RNA intermediate Signup and view all the answers

What is the worldwide prevalence of chronic Hepatitis B infection?

400 million Signup and view all the answers

Which of the following describes the hepatitis B vaccine?

Considered the first 'anti-cancer' vaccine Signup and view all the answers

Which is a key preventive measure against Hepatitis B infection?

Vaccination Signup and view all the answers

Which population groups are particularly recommended to receive the hepatitis B vaccine?

Adults living with diabetes and those at high risk Signup and view all the answers

Which treatment is known to reduce vireamia in HBV infection?

IFN-α Signup and view all the answers

What is often a consequence of the immune clearance of HBV-infected hepatocytes?

Liver damage due to inflammatory response Signup and view all the answers

How is perinatal transmission risk affected if the mother is HBsAg positive?

It increases to 90% if HBeAg positive Signup and view all the answers

Study Notes

Retroviruses

Retroviruses, like HIV, are characterized by their RNA genome, which is reverse transcribed into DNA before integration into the host cell's genome.
HIV-1 is more prevalent than HIV-2, which is primarily found in West Africa.
5 million new HIV infections occur annually.
HIV damages the immune system causing secondary infections and cancer. This is often referred to as Acquired Immunodeficiency Syndrome (AIDS).
A person's CD4 cell count, typically between 500 and 1500 cells/mL, drops in HIV positive individuals, placing them at a higher risk of developing severe illnesses.

Retrovirus Structure

Retroviruses have a core containing viral RNA.
They also have proteins, lipids, and an envelope.
A vital enzyme, reverse transcriptase, is crucial in the retroviral life cycle. Viral transcriptase plays a role in converting RNA into DNA.
Viral integration into the host cell's DNA is a critical part of the lifecycle. After the genetic material of this virus has been transcribed into a complimentary DNA sequence, a new enzyme known as integrase is used to integrate this sequence into the host's genome.

HIV Transmission

HIV is primarily transmitted through sexual contact (about 80%).
Perinatal transmission (10%), involving transmission from mother to child during pregnancy, childbirth, or through breastfeeding, is significant.
Blood and blood product transfusions (3-5%) can also transmit HIV.

HIV Pathogenesis

Infected CD4+ T cells and macrophages migrate to lymph nodes, where high viral replication occurs.
The initial infection is followed by a period of high viral load in the blood.
This is often followed by a period of no apparent symptoms.
Then, progressively, the CD4+ T cell count can decrease gradually.
If the CD4+ cell count falls below 200/μL, this is often referred to as AIDS.

Undetectable = Untransmittable (U=U)

Maintaining an undetectable viral load through consistent antiretroviral therapy (ART) prevents sexual transmission.
Observational studies since 1996 show a clear link between reduced viral loads and reduced transmission risk.
To ensure undetectable viral load, daily ART is essential.

Hepadnaviruses

Hepadnaviruses, the group including hepatitis B virus (HBV), affect humans and some animals (including birds and mammals).
Globally, over 400 million people are chronic carriers of HBV.
HBV carries a partially closed double-stranded DNA genome, and replicates via an RNA intermediate.

HBV Infection

Transmission occurs primarily through blood and semen (including sexual contact and drug abuse).
Acute HBV infections are often mild to asymptomatic in children, but can progress to chronic infection in a proportion of adults.
Chronic HBV infections result in over 500,000 deaths annually, often from complications like cirrhosis or liver cancer (hepatocellular carcinoma). Progression can occur in 15-40% of individuals with chronic infection.
The incubation period is typically 2-3 months.

Hepatitis B in Malaysia

Approximately 400,000 Malaysians live with chronic HBV, with a seroprevalence between 1.5-9.8%.
Urban areas in Malaysia tend to have more undiagnosed cases than rural areas.
Vertical transmission (from mother to child) is the primary method of transmission.
Infants of HBsAg positive mothers must receive HBV immunoglobulin and vaccine within 12 hours of birth to reduce risk of transmission.

Non-Infectious HBV Particles

These particles are produced by infected liver cells and released into the blood.
They contain proteins that form the HBV surface, and they are used in some vaccines.
Their shapes include spheres and filaments.

HBV Markers

HBeAg: A soluble early antigen, present in acute HBV infections, but less common in chronic. Used for detecting acute HBV.
HBsAg : Is crucial in diagnosing HBV infection, as it's a marker for surface antigen of the virus.
Anti-HBc IgM/IgG antibodies: Represent an immune response to the core antigen. IgM antibodies are typically present during acute infection, while IgG antibodies indicate previous or chronic infection.
Anti-HBs: Indicates immunity after infection or vaccination.

HBV Immunopathology

HBV progeny bud out from hepatocytes, initiating a response.
Cell-mediated immune responses, primarily CD8+ T cells, clear virus infections, but lead to liver damage during acute and chronic infections.
Preventive measures include vaccination, safe practices, and avoiding drug/needle sharing.
Treatment options like interferon-α (IFN-α) and nucleoside analogues may reduce viral load.

HBV Prevention

Vaccination is available in two forms: stand-alone HBV vaccine and combined hexavalent vaccine (includes other childhood antigens).
Vaccination can be administered to infants during the first few months of life, as well adults.
This is a primary prevention method and is crucial in decreasing the incidence of chronic hepatitis B.

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Explore the fascinating world of retroviruses, particularly HIV, through this engaging quiz. Learn about their structures, life cycles, and the critical impact they have on the immune system. Test your knowledge on how these viruses operate and affect human health.