HIV Primer Quiz by Dr. Vishy Venkataraman

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Questions and Answers

Which process primarily occurs as the immature virion buds from the cell membrane?

Transcription of viral mRNA

Cleavage of precursor polyproteins by viral protease (correct)

Replication of host cell DNA

Integration of viral DNA into the host DNA

What occurs first after the initial infection of HIV in the genital tract?

Presence of HIV in the blood

Infection of CD8 T cells

Infection of helper T cells (CD4-positive cells) (correct)

Shift from Th1 to Th2 responses

What is the role of CD8 T cells in the context of HIV infection?

To initiate the lytic cycle of the virus

To help in controlling HIV infection (correct)

To produce antibodies against the virus

To express MHC class II molecules

What change occurs in CD4 T cell responses as a result of HIV infection?

Shift from Th1 to Th2 cytokines Signup and view all the answers

What function do CD4 T cells primarily serve in the immune response?

Enhance the immune response and aid other cells Signup and view all the answers

Which of the following best describes the initial detection of HIV in the body?

Detected in blood 4 to 11 days post-infection Signup and view all the answers

Which statement regarding the integration of viral DNA is accurate?

Multiple copies of viral DNA can integrate into host DNA Signup and view all the answers

What type of T cells recognize processed antigen peptides on APC associated with MHC class II?

CD4 T cells Signup and view all the answers

What is the primary function of CD8 T cells in the immune response?

To produce antimicrobial proteins that kill host cells and viruses Signup and view all the answers

Which cytokine is primarily responsible for the differentiation of CD4 T cells into the Th1 subset?

Interleukin-12 (IL-12) Signup and view all the answers

What role does IFN-γ play in the immune response?

It enhances the effector functions of macrophages and neutrophils Signup and view all the answers

Which subset of CD4 T cells produces IL-5 for B cell differentiation?

Th2 cells Signup and view all the answers

What is the significance of IL-17 produced by Th17 cells?

It attracts neutrophils to sites of bacterial infection Signup and view all the answers

How does IL-2 contribute to T cell responses?

It promotes the proliferation of both CD4 and CD8 T cells Signup and view all the answers

Which cytokines are produced by Th2 cells to induce B cell differentiation?

IL-4 and IL-5 Signup and view all the answers

What effect does IFN-γ have on the Th2 response?

It suppresses the Th2 response Signup and view all the answers

What type of immune response is typically utilized to control intracellular infections under normal conditions?

Th1 subset response Signup and view all the answers

What is the effect of HIV infection on Th1 and Th2 cytokine levels in individuals?

Increase in Th2 cytokines, decrease in Th1 cytokines Signup and view all the answers

Which cytokine is notably elevated in HIV seropositive individuals, contributing to the Th2 response?

IL-4 Signup and view all the answers

What role do CD8 T cells play in response to HIV infection?

Kills host cells and intracellular viruses Signup and view all the answers

How do mutant strains of HIV affect the ability of cytotoxic T cells?

They reduce cytotoxic T cell recognition and effectiveness Signup and view all the answers

What happens to the immune system as a result of the shift from a Th1 response to a Th2 response in HIV infection?

Loss of immunity and increased susceptibility to infections Signup and view all the answers

What proteins do CD8 T cells produce to induce apoptosis in infected host cells?

Perforin and granzymes Signup and view all the answers

What is the consequence of cytotoxic T cell failure in controlling HIV infection?

Transition to a chronic HIV infection Signup and view all the answers

What does the 2016 WHO report recommend regarding the initiation of ART?

ART should start immediately, regardless of CD4 count. Signup and view all the answers

Which cell type is primarily targeted and depleted by HIV leading to immune deficiency?

CD4 T cells Signup and view all the answers

What is the role of opportunistic infections in individuals with AIDS?

They significantly increase morbidity and mortality. Signup and view all the answers

Which of the following is NOT considered an opportunistic infection associated with AIDS?

Streptococcus pneumoniae Signup and view all the answers

In the context of HIV infection, what shift occurs in CD4 T cell responses?

From Th1 to Th2 dominance. Signup and view all the answers

What is the primary function of reverse transcriptase in HIV?

To replicate viral RNA into DNA. Signup and view all the answers

Which CD4 T cell subset is particularly depleted in the context of HIV infection?

Th17 cells Signup and view all the answers

What is the general purpose of ART in the treatment of HIV?

To suppress viral load and prevent disease progression. Signup and view all the answers

What is a significant consequence of the loss of Th1 CD4 helper T cells during HIV infection?

Decreased viability of cytotoxic T cells due to insufficient lymphokines Signup and view all the answers

During which stage of HIV infection do antibodies to HIV typically appear?

Within 2 to 4 weeks after initial infection Signup and view all the answers

Which symptom is NOT typically observed during the acute stage of HIV infection?

Persistent night sweats Signup and view all the answers

What is the primary reason for the potential for false-negative serologic tests during the acute stage of HIV infection?

The body has too few antibodies to detect Signup and view all the answers

What happens to the level of viremia after the resolution of the acute stage in HIV infection?

Viremia decreases significantly Signup and view all the answers

Which characteristic is true regarding the acute stage of HIV infection?

It usually resolves spontaneously in about 2 weeks Signup and view all the answers

What should be done if HIV infection is suspected but antibody tests return negative?

Use a polymerase chain reaction (PCR) assay for viral RNA Signup and view all the answers

Which immune component is primarily responsible for combating HIV during the acute stage?

CD8-positive T cells Signup and view all the answers

What does ART stand for in the context of HIV treatment?

Antiretroviral Therapy Signup and view all the answers

When should ART treatment be initiated according to the latest WHO recommendations?

Immediately, regardless of CD4 count Signup and view all the answers

What is a key reason for combining therapy with ART in HIV treatment?

To prevent opportunistic infections Signup and view all the answers

Which of the following is NOT classified as an opportunistic infection associated with AIDS?

Malaria Signup and view all the answers

What role do CD4 T cells primarily serve in the immune response against HIV?

They mediate host immune responses Signup and view all the answers

How many individuals worldwide were estimated to be living with HIV or AIDS as of 2015?

37 million Signup and view all the answers

What happens to CD4 T cell responses in individuals infected with HIV?

They shift from Th1 to Th2 responses Signup and view all the answers

What is the role of the CD8 T cells in relation to HIV infection?

They exhibit ineffective responses against HIV Signup and view all the answers

What is the primary reason individuals with AIDS become susceptible to opportunistic infections?

Decreased levels of cytokines such as IL-2, IFN-γ, and IL-17 Signup and view all the answers

Which population is most affected by HIV infections worldwide?

Sub-Saharan Africa Signup and view all the answers

What characteristic distinguishes HIV-1 from HIV-2?

HIV-1 is found worldwide while HIV-2 is mainly in West Africa Signup and view all the answers

What role does reverse transcriptase play in the HIV life cycle?

Converts RNA to cDNA Signup and view all the answers

What is the normal range of CD4 T cell counts in healthy individuals?

500-1500/mm3 Signup and view all the answers

Which of the following is NOT a cell type infected by HIV?

B lymphocytes Signup and view all the answers

How many copies of RNA are contained within the HIV genome?

Two Signup and view all the answers

What is the fourth leading cause of death worldwide?

AIDS Signup and view all the answers

What is formed after the cleaving of the Pol polyprotein during the maturation of the virion?

Mature infectious virion Signup and view all the answers

Which cells act as the initial site of HIV infection in the genital tract?

Dendritic cells Signup and view all the answers

What type of immune response do CD4 T cells primarily enhance?

Cell-mediated immunity Signup and view all the answers

During HIV infection, which cytokine shift occurs in CD4 T cells?

Th1 to Th2 Signup and view all the answers

What enables the replication of viral mRNA from proviral DNA?

Host cell RNA polymerase Signup and view all the answers

How does HIV affect the Th1 and Th2 balance within the immune system?

It causes Th2 responses to dominate. Signup and view all the answers

What role do CD8 T cells play in the context of HIV infection?

They help control HIV infection. Signup and view all the answers

What is a direct consequence of CD4 T cell depletion due to HIV infection?

Higher risk of opportunistic infections Signup and view all the answers

What typically characterizes the latent stage of HIV infection?

The patient is asymptomatic with low or absent viral production Signup and view all the answers

What is the most characteristic manifestation of AIDS?

Pneumonia caused by Pneumocystis jiroveci Signup and view all the answers

Which symptom is commonly associated with AIDS-related complex (ARC)?

Persistent fevers and fatigue Signup and view all the answers

During which stage do individuals typically become symptomatic after HIV infection?

During the acute infection stage Signup and view all the answers

What typically occurs in untreated patients during the latent stage of HIV infection?

A long period without symptoms for 7 to 11 years Signup and view all the answers

What typically occurs during the acute stage of HIV infection?

A high-level viremia occurs, making the infection highly transmissible. Signup and view all the answers

What change occurs in CD8 T cells during the resolution of HIV acute stage?

Their levels typically rise in response to the viral infection. Signup and view all the answers

Why can false-negative serologic tests occur during the acute stage of HIV infection?

Antibodies to HIV take longer to appear than the infection itself. Signup and view all the answers

What is the initial clinical signs of HIV infection in the acute stage?

An infectious mononucleosis-like picture with a rash. Signup and view all the answers

What implication does the inability to detect antibodies at the time of testing have?

HIV may be transmitted to others despite negative test results. Signup and view all the answers

What is a significant consequence of the death of Th1 CD4 helper T cells in HIV infection?

Insufficient production of lymphokines necessary for cytotoxic T cell viability. Signup and view all the answers

Which assay should be done if a person is suspected to be infected with HIV but antibody tests are negative?

A PCR-based assay for viral RNA in the plasma. Signup and view all the answers

What happens to the level of viremia following the acute stage of HIV infection?

It decreases to a low but detectable amount. Signup and view all the answers

Study Notes

Immune Response to HIV

CD8 T cells, also known as cytotoxic T cells, are crucial for combating viral infections and cancer by producing perforin, granulysin, and granzymes.
CD4 T cells differentiate into subsets (Th1, Th2, Th17) based on polarizing cytokines from antigen-presenting cells (APCs).
Interleukin-12 (IL-12) leads to differentiation of CD4 T cells into Th1 cells, which secrete IL-2 and interferon-gamma (IFN-γ).
IL-2 promotes proliferation of CD4 and CD8 T cells, enhancing immune responses.
IFN-γ amplifies the Th1 response, enhances macrophage and neutrophil functions, and is vital for activating cytotoxic T cells.
IL-10 and IL-4 encourage differentiation into Th2 cells, which secrete cytokines that promote B cell functions but are less effective against intracellular pathogens.
IL-23 causes differentiation into Th17 cells, producing IL-17 to recruit neutrophils during bacterial infections.

HIV Life Cycle

HIV RNA is transcribed into double-stranded DNA by DNA polymerase before integrating into host DNA.
Integration can occur at various host DNA sites, allowing for multiple copies of viral DNA.
Viral mRNA is synthesized from proviral DNA and translated into polyproteins, forming immature virions that mature through proteolytic cleavage.

Immunopathogenesis of HIV

HIV infects CD4 T cells, leading to their depletion and resulting in weakened immunity and susceptibility to opportunistic infections.
Initial infection predominantly occurs in dendritic cells and spreads to local CD4 T cells, with HIV detectable in the blood 4-11 days post-infection.
CD8 T cells play a key role in controlling HIV, but the effectiveness declines as HIV mutations arise.

Clinical Stages of HIV Infection

Acute Stage: Occurs 2-4 weeks post-infection; characterized by fever, sore throat, lymphadenopathy, and a maculopapular rash. High-level viremia and detectable HIV antibodies typically develop within 3-4 weeks.
Latent Stage: Immune response begins to control the virus; however, HIV remains present at low levels.
Late Immunodeficiency Stage: Progressive depletion of CD4 cells leads to AIDS.

Treatment and Prevention Strategies

Antiretroviral therapy (ART) is a lifelong treatment that helps manage HIV but does not cure it. WHO now recommends immediate ART initiation regardless of CD4 counts.
As of 2015, an estimated 37 million individuals worldwide are living with HIV or AIDS, with 17 million on ART.
Importance of preventing opportunistic infections in HIV/AIDS patients is critical in management.

Opportunistic Infections Associated with AIDS

Common infections include Pneumocystis jirovecii pneumonia, herpes simplex virus, cytomegalovirus, and various fungal infections like candidiasis and cryptococcosis.

Retrovirus, Lentivirus, gp120, gp41, p24, integrase, reverse transcriptase, protease, CXCR4, and CCR5 are vital components in HIV infection and replication.
The shift from a Th1 to a Th2 response in HIV infections contributes to reduced effectiveness against viruses and higher vulnerability to opportunistic infections.

HIV Overview

HIV (Human Immunodeficiency Virus) is a retrovirus from the lentivirus subgroup, leading to AIDS (Acquired Immunodeficiency Syndrome).
The WHO recommended initiating Antiretroviral Therapy (ART) when CD4+ T cell counts fall below 500 cells/mm³, but current guidelines advocate starting ART immediately regardless of CD4 count.
37 million individuals globally have HIV/AIDS, with 17 million receiving ART.

Immune Response and HIV Transmission

HIV primarily infects and depletes CD4+ T lymphocytes and macrophages, compromising immune function and increasing susceptibility to opportunistic infections.
Two-thirds of the 36.9 million HIV-infected individuals reside in sub-Saharan Africa, where healthcare access is limited.
HIV transmission occurs mainly through sexual contact and infected blood transfer.

Cytokine Involvement in HIV

Healthy individuals normally have CD4 T cell counts between 500-1500/mm³; counts drop below 200/mm³ in AIDS, linked to reduced cytokines IL-2, IFN-γ, and IL-17.
IL-2 supports the viability of T cells; IFN-γ enhances immune responses; IL-17 provides mucosal immunity.

Stages of HIV Infection

Acute Stage: Begins 2-4 weeks post-infection, presenting as infectious mononucleosis-like symptoms. High-level viremia makes it highly transmissible. Antibodies typically develop 10-14 days post-infection.
Latent Stage: Can last 7-11 years in untreated patients, asymptomatic but with ongoing viral replication in lymph nodes. May present with AIDS-related complex (ARC) symptoms.
Late Stage (AIDS): Characterized by CD4 cell counts below 200/μL, leading to frequent opportunistic infections.

Opportunistic Infections in AIDS

The most common opportunistic infection in AIDS is pneumonia caused by Pneumocystis jirovecii.
Other infections include Herpes simplex, cytomegalovirus, Candida albicans, and Mycobacterium tuberculosis, resulting from weakened immunity.

HIV Genetic Structure and Replication

HIV contains two identical RNA copies and reverse transcriptase, allowing conversion of RNA to complementary DNA (cDNA).
Viral DNA can integrate into host DNA, leading to multiple copies and subsequent production of viral proteins.

Clinical Management and Monitoring

Continuous lifelong ART is critical for managing HIV as there is currently no cure.
Monitoring includes tracking CD4 counts and assessing for opportunistic infections to provide timely interventions.

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Description

Test your knowledge on the roles of CD8 T cells in viral infections and cancer with this quiz designed by Professor Vishy Venkataraman. Understand the key functions of cytotoxic T cells and their importance in the immune response against pathogens.