Human Immunodeficiency Virus Overview
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Questions and Answers

Which of the following accurately describes the morphology of HIV?

  • Helical, non-enveloped virus
  • Brick-shaped, enveloped virus
  • Spherical, enveloped virus (correct)
  • Rod-shaped, non-enveloped virus

    • HIV-1 is the only known strain of the virus.

    False (B)

    What is the name of the protein that acts as the group-specific antigen for HIV?

    p24

    The HIV genome is composed of two identical copies of _______ RNA.

    <p>single-stranded positive-sense</p> Signup and view all the answers

    Match the following HIV genes with their encoded proteins:

    <p>gag = Internal capsid and matrix proteins pol = Reverse transcriptase, integrase, and protease env = Envelope glycoproteins gp120 and gp41</p> Signup and view all the answers

    Which of the following proteins mediates fusion of the viral envelope with the cell membrane during infection?

    <p>gp41 (A)</p> Signup and view all the answers

    Antibodies against the p24 antigen are highly effective in preventing HIV infection.

    <p>False (B)</p> Signup and view all the answers

    What is the function of the enzyme reverse transcriptase in the HIV lifecycle?

    <p>Reverse transcriptase transcribes the viral RNA genome into DNA, which is then integrated into the host cell's genome.</p> Signup and view all the answers

    What is the primary method of HIV transmission through blood?

    <p>Transmission by blood transfusion (B)</p> Signup and view all the answers

    The window period for antibody appearance in HIV infection is typically 1 to 2 weeks.

    <p>False (B)</p> Signup and view all the answers

    What are the main goals of antiretroviral therapy in HIV treatment?

    <p>Inhibit replication of HIV and reduce morbidity and death.</p> Signup and view all the answers

    Mother-to-child transmission of HIV can occur by _____ or by perinatal transmission.

    <p>vertical transmission</p> Signup and view all the answers

    Match the type of drug with its function in HIV treatment:

    <p>NRTIs = Inhibit reverse transcriptase and cause chain termination NNRTIs = Block the morphogenesis of the virion Protease inhibitors = Prevent maturation of viral particles</p> Signup and view all the answers

    During the window period, the serum of the patient is:

    <p>Negative for serum antibodies and positive for viral antigens (A)</p> Signup and view all the answers

    Identify one type of test used for laboratory diagnosis of HIV infection.

    <p>ELISA, Western blot, or antigen p24.</p> Signup and view all the answers

    Acute infection of HIV is indicated by a negative result for antibody tests.

    <p>True (A)</p> Signup and view all the answers

    Which class of antiretroviral drugs does Zidovudine (AZT) belong to?

    <p>Nucleoside reverse transcriptase inhibitors (NRTIs) (B)</p> Signup and view all the answers

    A safe and effective vaccine against HIV is currently available.

    <p>False (B)</p> Signup and view all the answers

    What is a significant scientific obstacle to the development of an AIDS vaccine?

    <p>Antigenic diversity</p> Signup and view all the answers

    The class of drugs that includes Ritonavir is called __________.

    <p>Protease inhibitors</p> Signup and view all the answers

    Match the following antiretroviral drugs with their respective categories:

    <p>Tenofovir = Nucleotide reverse transcriptase inhibitor Enfuvirtide = Fusion transcriptase inhibitor Efavirenz = Non-nucleoside reverse transcriptase inhibitor Abacavir = Nucleoside reverse transcriptase inhibitor</p> Signup and view all the answers

    Which of the following is NOT a step in the prevention and control of HIV?

    <p>Routine vaccinations for the general population (D)</p> Signup and view all the answers

    Secretory antibodies are crucial for preventing sexual transmission of HIV.

    <p>True (A)</p> Signup and view all the answers

    What is the role of matrix protein in the HIV replication cycle?

    <p>Structural support and organization of the viral envelope</p> Signup and view all the answers

    What is the primary function of integrase in the HIV replication process?

    <p>Facilitates integration of proviral DNA (A)</p> Signup and view all the answers

    HIV can integrate its DNA with the host cell DNA, leading to a persistent infection.

    <p>True (A)</p> Signup and view all the answers

    What is the typical course duration of untreated HIV infection before it progresses to AIDS?

    <p>10 years</p> Signup and view all the answers

    HIV is transmitted primarily through __________ contact, accounting for over 70% of transmission cases.

    <p>sexual</p> Signup and view all the answers

    Match the following HIV proteins with their roles:

    <p>Tat = Regulates viral transcription Nef = Down-regulates class I MHC proteins Gag = Forms the structural proteins Protease = Splits precursor polyproteins into functional units</p> Signup and view all the answers

    What happens to the CD4 T cell count when a patient develops full-blown AIDS?

    <p>Falls below 200/µL (D)</p> Signup and view all the answers

    HIV can kill CD4 helper T cells as part of its immune evasion strategy.

    <p>True (A)</p> Signup and view all the answers

    Name one protein produced by HIV that helps in down-regulating class I MHC proteins.

    <p>Nef</p> Signup and view all the answers

    Flashcards

    Ribonuclease H activity

    Enzyme that degrades RNA in RNA-DNA hybrids.

    Integrase

    Facilitates the integration of proviral DNA into host DNA.

    Protease

    Enzyme that splits polyproteins into functional viral proteins.

    HIV replication cycle

    Process from HIV attachment to budding and release.

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    Tat and Nef proteins

    Proteins that down-regulate MHC class I molecules.

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    Full-blown AIDS

    Advanced HIV infection with CD4 count below 200/μL.

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    HIV transmission

    Spread of HIV primarily through sexual contact.

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    Clinical latency

    Stage after initial infection where the virus is less active.

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    HIV

    Human Immunodeficiency Virus, a retrovirus that causes AIDS.

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    Lentivirus

    A subfamily of retroviruses, including HIV.

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    HIV-1 vs HIV-2

    HIV-1 is the most common type linked to AIDS; HIV-2 primarily found in West Africa.

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    Viral genome

    HIV's genome is diploid with two identical RNA copies.

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    gag gene

    Gene encoding internal capsid and core proteins in HIV.

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    pol gene

    Gene encoding enzymes like reverse transcriptase, crucial for HIV replication.

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    env gene

    Gene coding for envelope glycoproteins gp120 and gp41, essential for cell entry.

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    p24 antigen

    Group-specific antigen used as a serological marker for HIV diagnosis.

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    Transmission by blood transfusion

    Infectious transmission via transfusion of blood products from HIV-positive individuals.

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    Parenteral transmission

    Transmission of HIV predominantly among IV drug users.

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    Mother-to-child transmission

    HIV can be transmitted from mother to infant either vertically or perinatally.

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    Window period

    Time before antibodies appear in serum, usually 3 to 4 weeks.

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    ELISA test

    Screening test used to detect HIV antibodies in the blood.

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    Antiretroviral treatment

    Main treatment for HIV, aims to inhibit virus replication and reduce health risks.

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    NRTIs

    Nucleoside analogs that inhibit reverse transcriptase, causing DNA chain termination.

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    Protease inhibitors

    Class of HIV drugs that prevent maturation of viral particles during replication.

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    Tenofovir

    A nucleotide reverse transcriptase inhibitor effective against HIV.

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    Enfuvirtide

    A fusion inhibitor that prevents HIV from entering host cells.

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    Vaccine development challenges

    Obstacles in creating an effective HIV vaccine due to the virus's complexities.

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    Antigenic diversity

    The rapid mutation of HIV that alters its antigenic structure, complicating vaccine design.

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    Mucosal transmission

    HIV spreads through mucosal surfaces requiring specific immune responses for prevention.

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    Study Notes

    Human Immunodeficiency Virus (HIV)

    • HIV is a lentivirus, a subfamily of Lentiviridae in the retrovirus family.

    • HIV-1 was first isolated from AIDS cases.

    • HIV-2 was isolated from some AIDS cases in West Africa.

    • HIV is spherical and enveloped, measuring up to 120nm in diameter.

    • It has a unique three-layered structure:

      • Innermost genome layer
      • Middle cone-shaped nucleocapsid
      • Outer membrane of glycoprotein surrounded by a lipoprotein envelope

    • The genome is diploid and consists of two identical copies of single-stranded positive-sense RNA.

    • The gag gene encodes the internal capsid and matrix "core" proteins (p15, p18, and p24).

    • The pol gene encodes reverse transcriptase, integrase, and protease enzymes.

    • The env gene codes for gp160 (a precursor glycoprotein) which splits to form gp120 and gp41, forming surface spikes and transmembrane tissue proteins.

    • p24 is a group-specific antigen, important for HIV diagnosis, but serum antibodies against it are not protective.

    • gp120 combines with CD4 receptors and chemokine receptors on CD4 cells, neutralizing infectivity.

    • gp41 is embedded in the envelope and mediates fusion of the viral envelope with the cell membrane at infection time.

    • Reverse transcriptase transcribes RNA into proviral DNA, and also has ribonuclease H activity to degrade the RNA in RNA-DNA hybrids.

    • Integrase facilitates integration of proviral DNA into host cell DNA.

    • Protease splits precursor polyproteins into functional viral polypeptides.

    • The course of untreated HIV infection is typically 10 years or more.

    • HIV progresses through stages including primary infection, dissemination to lymphoid organs, clinical latency, and a late stage of profound immunosuppression (full-blown AIDS).

    • Full-blown AIDS is characterized by a CD4 count below 200/µL, elevated virus levels, and the presence of p24 antigen in the blood (CD4 count below 450/µL).

    • HIV transmission occurs through:

      • Sexual contact (over 70% of cases)
      • Blood or blood products (transfusion of infectious blood/products from HIV-positive individuals)
      • Parenteral transmission (especially among IV drug users)
      • Mother-to-child transmission (vertical or perinatal)

    • Laboratory diagnosis of HIV infection is crucial for confirming AIDS, detecting HIV, identifying carriers, and for seroepidemiological studies.

    • The "window period" is the time before antibody appears in the serum (3-4 weeks).

      • During this period, serum is negative for antibodies but positive for viral antigens.

    • Antiretroviral treatment is the primary HIV treatment approach.

    • Goals of antiretroviral therapy are to inhibit HIV replication and reduce morbidity/mortality.

    • Anti-HIV drugs include:

      • Nucleoside analog reverse transcriptase inhibitors (NRTIs)
      • Non-nucleoside reverse transcriptase inhibitors (NNRTIs)
      • Protease inhibitors (Specific drug names included in separate section).

    • HIV escapes the immune system by integrating viral DNA with the host cell DNA, high mutation rate of the env gene, down-regulating class I MHC proteins via Tat and Nef proteins, and infecting/killing CD4 helper T-cells. HIV persists in an immune-privileged state in macrophages and CD4 T cells.

    • Vaccine development is still underway, facing challenges like: Antigenic diversity/hypervariability changes in virus, mucosal transmission requiring secretory antibodies, virus spread via infected syncytia, and virus latency, integration into host chromosome, and high error rate of reverse transcriptase leading to continuous mutations.

    Specific Anti-HIV Drugs

    • Zidovudine (AZT)
    • Didanosine (ddI)
    • Zalcitabine (ddC)
    • Lamivudine (3TC)
    • Stavudine (d4T)
    • Abacavir (1592)
    • Nevirapine (NVP)
    • Delaviridine
    • Efavirenz
    • Ritonavir
    • Indinavir
    • Saquinavir
    • Nelfinavir
    • Amprenavir
    • Tenofovir
    • Enfuvirtide

    Assignment Questions

    • Difference between viral load and CD4 count: Viral load quantifies the amount of HIV in the blood, while CD4 count measures the number of helper T-cells. Lower CD4 counts and higher viral loads indicate worse disease progression.
    • Elaborate on HIV replication cycle: The replication cycle is a complex process with contributing molecules such as reverse transcriptase, integrase, and protease, along with specific viral proteins like those in the capsid, core, or envelope.

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    Description

    This quiz explores the key features of the Human Immunodeficiency Virus (HIV), including its structure, genome, and important genes. Gain insights into the differences between HIV-1 and HIV-2, and the significance of the p24 antigen. Perfect for students studying virology and infectious diseases.

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