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Questions and Answers
HIV enters the body and binds to CD4 T cells as its first receptor.
True
HIV directly causes tumors like Kaposi’s sarcoma and lymphoma.
False
Antibodies against various HIV proteins effectively neutralize the virus in vivo.
False
HIV infection leads to the suppression of cell-mediated immunity (CMI).
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HIV causes lytic infection of macrophage lineage cells.
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HIV can be transmitted through unprotected sexual intercourse.
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HIV is transmitted through casual contact like hugging and kissing.
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Sharing intravenous drug paraphernalia increases the risk of HIV transmission.
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Once infected, a person is considered to be infected with HIV for life.
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HIV can be transmitted through coughing and sneezing.
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Multiple sexual partners do not contribute to HIV risk.
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The production of Tat and Nef proteins helps HIV evade the host immune system.
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HIV undergoes antigenic drift of the env gene, contributing to its survival.
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A patient experiencing opportunistic infections typically has a CD4 count below 200 cells/mm3.
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High levels of HIV RNA are associated with a normal CD4 count.
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Patients may present with fever and generalized lymphadenopathy during the acute phase of HIV infection.
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Kaposi sarcoma and herpes zoster are both skin-related opportunistic infections in AIDS.
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CD4 counts are highest when HIV RNA levels are above 103 copies.
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Cervical cancer is categorized as a gastrointestinal opportunistic infection related to AIDS.
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An asymptomatic patient may have a CD4 count of 400 cells/mm3 or above.
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Cryptococcal meningitis is a CNS opportunistic infection associated with HIV.
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The HIV-1/2 Antigen/Antibody immunoassay is a screening assay/test.
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The Rapid HIV assay/test is only used for blood donors.
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The Western Blot test has a lower specificity compared to other tests.
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P24/p31 detection is not used in supplementary tests for HIV.
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Indirect fluorescent antibody (IFA) test is typically less expensive than the Western blot test.
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Proviral DNA PCR is primarily performed on adults.
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The HIV-1/HIV-2 differentiation assay can produce indeterminate results.
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The rapid test can distinguish between antibodies to HIV-1 and HIV-2.
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The presence of anti-CMV IgG indicates previous exposure to CMV.
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Purified protein derivative (PPD) testing is specific for evaluating HIV infection.
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Rapid Plasma Reagin (RPR) can yield false-positive results.
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The aims of HIV treatment are to improve immune function and lead to an increased viral load.
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Toxoplasmosis testing is done via the anti-Toxoplasma antibody test.
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CMV reactivation is a concern in patients with low CD4 counts.
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Antibody tests for Gonorrhea and Chlamydia are typically performed as part of an initial HIV workup.
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The treatment of HIV is uniform regardless of the stage of the disease.
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Study Notes
HIV: Risk Factors
- Unprotected sexual intercourse, especially receptive anal intercourse, increases the risk of HIV transmission.
- Sharing of intravenous drug paraphernalia, such as needles, can spread HIV.
- Multiple sexual partners increases the probability of contracting HIV.
- Individuals with sexually transmitted diseases (STDs), including gonorrhea, chlamydia infection, syphilis, and herpes genitalis, are at higher risk of HIV infection.
- Mucosal contact with infected blood or sharp injuries can lead to HIV transmission.
HIV: Transmission
- The primary modes of HIV transmission are sexual contact, including oral, anal, and vaginal intercourse.
- HIV can be transmitted through blood transfusions or direct contact with infected blood, such as through needle sticks.
- Mothers infected with HIV can transmit the virus to their infants during pregnancy, delivery, or breastfeeding.
- HIV is not transmitted through casual contact, such as touching, hugging, kissing, coughing, sneezing, or sharing glasses, plates, or utensils.
HIV: Immunity
- Once infected with HIV, an individual is considered infected for life due to the integration of viral DNA into the host's DNA.
- HIV evades the host's immune system through several mechanisms:
- Integration of viral DNA into host cell DNA: This allows HIV to persist within the host's cells.
- A high rate of mutation of the env gene: This constant genetic variation makes it difficult for the immune system to recognize and target the virus.
- Antigenic drift of gp120: This protein on the surface of HIV undergoes changes, evading antibodies produced by the immune system.
- Production of Tat and Nef proteins: These proteins downregulate class 1 MHC proteins, which are essential for cytotoxic T cells to recognize and kill infected cells.
- The main immune response to HIV infection involves cytotoxic CD8-positive lymphocytes, which control the virus for many years.
- When the number of CD4 helper T cells declines, cytotoxic T cells lose their effectiveness, as they rely on lymphokines produced by CD4 T cells.
- Antibodies against HIV proteins, such as p24, gp120, and gp41, are produced, but they are not very effective at neutralizing the virus in the body.
HIV: Pathogenesis
- HIV enters the body and binds to CD4 T cells, which are found on monocytes, macrophages, and dendritic cells.
- HIV subsequently binds to chemokine receptors on host cells, leading to entry and infection.
HIV: Effects
- HIV infects CD4-positive cells, including T cells and macrophages, and kills them, suppressing the immune system.
- This suppression increases the risk of opportunistic infections (OI) and certain cancers, such as Kaposi's sarcoma and lymphoma.
- HIV does not directly cause these cancers; its genes are not found in the cancer cells.
- HIV infection disrupts the normal functioning of the immune system, leading to dysregulation of immune functions and loss of B cell control.
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Effects of HIV Infection:
- Eye: Cytomegalovirus (CMV) retinitis.
- Gastrointestinal (GIT): Oral and esophageal candidiasis (thrush), Cryptosporidiosis.
- Skin: Kaposi's sarcoma, herpes zoster, molluscum-like lesions caused by T. marneffei.
- Respiratory (RESP): Pneumonia (e.g., caused by Mycobacterium tuberculosis/Mycobacterium avium complex, Streptococcus pneumoniae, CMV, Pneumocystis jirovecii).
- Central Nervous System (CNS): Herpes simplex virus (HSV) encephalitis, cryptococcal meningitis, toxoplasmosis.
- Genitourinary (GUI): Cervical cancer.
HIV Infection: Stages
- Primary/Acute Infection: This stage may resemble mononucleosis, with symptoms like fever, rash, and generalized lymphadenopathy. Viral load increases, while CD4 counts decrease.
- Asymptomatic: This stage may last for years, with patients experiencing no symptoms. CD4 counts remain above 400 cells/mm3, although they are reduced from their normal levels.
- Opportunistic Infection (OI)/AIDS: This stage occurs when CD4 counts fall below 200 cells/mm3, indicating severe immunosuppression. Patients may develop one or more opportunistic infections due to the weakened immune system.
HIV Infection: Lab Investigations
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Screening Tests:
- HIV-1/2 Antigen/Antibody immunoassay/Combo: This test detects both HIV-1 and HIV-2 antibodies and antigens.
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Supplementary/Secondary Tests:
- Detection of p24/p31 antigen and glycoproteins (gp120/160 and gp41): These tests can detect a greater number of recent infections before seroconversion.
- Qualitative HIV-1 Nucleic Acid (RNA) test: This test detects HIV-1 RNA, useful for early detection and monitoring viral load.
- Rapid HIV assay/test (e.g., Alere Determine HIV-1/2 Ag/Ab Combo test): These tests provide rapid results and are approved for use in serum, plasma, and whole blood.
- Western Blot: This test is highly specific and less likely to produce false-positive results.
- Indirect fluorescent antibody (IFA) test: This test is highly specific but more expensive than a Western blot.
- Proviral DNA PCR: This test is usually performed in newborns to distinguish maternal antibodies from actual infection.
HIV Infection: Initial Workup
- When a patient is diagnosed with HIV, a comprehensive initial workup should be performed to assess their overall health and identify potential risks. This workup includes:
- CMV: An anti-CMV IgG test to determine prior exposure to CMV and the risk of retinitis reactivation.
- Syphilis: An RPR (rapid plasma reagin) test to assess syphilis status, with confirmatory testing if positive.
- Gonorrhea and Chlamydial Infection: Rapid amplification testing (RPA) to screen for these infections.
- Hepatitis A, B, and C: Serology testing to assess the presence of these infections.
- Toxoplasmosis: An anti-toxoplasma antibody test to determine prior exposure and the risk of toxoplasmosis reactivation.
- Tuberculosis (TB): A purified protein derivative (PPD) skin test to evaluate for TB infection.
- Ophthalmological Examination: To assess for signs of CMV retinitis and other eye complications.
HIV Infection: Treatment
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Aims of Treatment:
- Prevent immune deterioration: To reduce the risk of opportunistic infections and malignancies.
- Reduce viral load: To minimize viral replication and slow disease progression.
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Treatment Considerations:
- Stage of disease: The treatment regimen depends on the progression of HIV infection.
- Concomitant opportunistic infections: Existing infections may require specific treatment considerations.
- CD4 counts: CD4 cell counts guide treatment decisions and monitor disease progression.
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Description
This quiz explores the various risk factors and transmission methods associated with HIV. It covers the importance of understanding unprotected sex, needle sharing, and the impact of sexually transmitted diseases on HIV risk. Join us to test your knowledge on how HIV is transmitted and the precautions needed to prevent infection.
