AIDS — Revision Notes

⚡ 30-Second Revision

Causative Agent: — HIV (Human Immunodeficiency Virus), a retrovirus.
Genetic Material: — Two identical single-stranded RNA molecules.
Key Enzymes: — Reverse transcriptase, Integrase, Protease.
Target Cells: — CD4+ T-lymphocytes (Helper T-cells).
Mechanism: — HIV RNA $xrightarrow{\text{Reverse Transcriptase}}$ Viral DNA $xrightarrow{\text{Integrase}}$ Host DNA (Provirus) $ightarrow$ Viral replication $ightarrow$ CD4+ T-cell destruction.
AIDS Diagnosis: — CD4+ T-cell count < $200,\text{cells/mm}^3$ or presence of AIDS-defining opportunistic infections/cancers.
Transmission: — Unprotected sexual contact, contaminated needles, mother-to-child (pregnancy, birth, breastfeeding).
NO Transmission: — Casual contact, insect bites, sharing food.
Diagnosis: — ELISA (screening), Western Blot/NAT (confirmatory).
Treatment: — ART (Antiretroviral Therapy) - combination of drugs targeting different viral life cycle stages (e.g., NRTIs, NNRTIs, PIs, INSTIs). Not a cure, but suppresses viral load.

2-Minute Revision

AIDS is the severe stage of infection by HIV, a retrovirus. HIV's unique feature is its reverse transcriptase enzyme, which converts its RNA genome into DNA. This viral DNA then integrates into the host's CD4+ T-lymphocyte DNA, turning the cell into a virus factory.

The progressive destruction of these crucial immune cells leads to immunodeficiency, making the body vulnerable to opportunistic infections like *Pneumocystis* pneumonia or Kaposi's sarcoma, which define AIDS.

Transmission occurs through specific bodily fluids via unprotected sex, shared needles, or from mother to child. Casual contact is not a risk. Diagnosis involves screening (ELISA) followed by confirmation (Western Blot or NAT).

While there's no cure, Antiretroviral Therapy (ART) effectively suppresses viral replication, allowing the immune system to recover, preventing AIDS, and enabling individuals to live healthy lives. Prevention focuses on safe practices and pre/post-exposure prophylaxis.

5-Minute Revision

AIDS, or Acquired Immunodeficiency Syndrome, is the final, most severe manifestation of infection with the Human Immunodeficiency Virus (HIV). HIV is a retrovirus, meaning it carries its genetic information as RNA and uses a unique enzyme, reverse transcriptase, to convert this RNA into DNA.

This viral DNA then integrates into the host cell's genome, primarily in CD4+ T-lymphocytes, which are critical 'helper' cells of the immune system. The virus then hijacks the cell's machinery to produce more viral particles, ultimately destroying the infected CD4+ T-cell.

This continuous destruction leads to a progressive decline in CD4+ T-cell count, severely compromising the immune system's ability to fight off pathogens. When the CD4+ count drops below 200 cells/mm³ or specific opportunistic infections (e.

g., *Pneumocystis jirovecii* pneumonia, candidiasis, Kaposi's sarcoma) appear, the individual is diagnosed with AIDS.

HIV is transmitted through specific bodily fluids: blood, semen, vaginal fluids, rectal fluids, and breast milk. Key transmission routes include unprotected sexual intercourse, sharing contaminated needles, and mother-to-child transmission during pregnancy, childbirth, or breastfeeding.

It is crucial to remember that HIV is NOT transmitted through casual contact like hugging, kissing, sharing food, or mosquito bites. Diagnosis typically involves an initial screening test like ELISA (detecting antibodies or antigens), followed by a confirmatory test such as Western Blot or Nucleic Acid Test (NAT).

There is currently no cure for HIV, but Antiretroviral Therapy (ART) has revolutionized its management. ART involves a combination of drugs from different classes (e.g., NRTIs, NNRTIs, PIs, INSTIs), each targeting a specific stage of the HIV life cycle (e.

g., reverse transcription, integration, protease activity). This multi-drug approach effectively suppresses viral replication to undetectable levels, allowing the immune system to recover, preventing progression to AIDS, and significantly improving the life expectancy and quality of life for people living with HIV.

Prevention strategies include safe sexual practices, avoiding needle sharing, and pre-exposure prophylaxis (PrEP) for high-risk individuals.

Prelims Revision Notes

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HIV (Human Immunodeficiency Virus): — Causative agent of AIDS. A retrovirus.
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Retrovirus: — Contains RNA genome. Uses reverse transcriptase to synthesize DNA from RNA.
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HIV Structure: — Envelope (gp120, gp41), capsid (p24), two RNA strands, enzymes (reverse transcriptase, integrase, protease).
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Key Enzymes & Functions:

* Reverse Transcriptase: RNA $ightarrow$ DNA synthesis. * Integrase: Integrates viral DNA into host DNA (provirus). * Protease: Cleaves viral polyproteins for virion maturation.

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Target Cells: — Primarily CD4+ T-lymphocytes (Helper T-cells). Also macrophages, dendritic cells.
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Pathogenesis: — HIV binds to CD4 receptor + co-receptor (CCR5/CXCR4) $ightarrow$ Entry $ightarrow$ Reverse transcription $ightarrow$ Integration $ightarrow$ Replication $ightarrow$ Budding $ightarrow$ CD4+ T-cell destruction $ightarrow$ Immunodeficiency.
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AIDS (Acquired Immunodeficiency Syndrome): — Final stage of HIV infection.

* Diagnosis: CD4+ T-cell count < $200,\text{cells/mm}^3$ OR presence of AIDS-defining opportunistic infections/cancers.

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Opportunistic Infections: — Occur due to weakened immune system.

* Examples: *Pneumocystis jirovecii* pneumonia (fungal), Candidiasis (fungal), Toxoplasmosis (parasitic), Cytomegalovirus (viral), Tuberculosis (bacterial), Kaposi's sarcoma (cancer, viral).

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Transmission Routes:

* Unprotected sexual contact (vaginal, anal, oral). * Sharing contaminated needles/syringes. * Mother-to-child (pregnancy, childbirth, breastfeeding). * Contaminated blood transfusions (rare due to screening).

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NO Transmission: — Casual contact (hugging, kissing, sharing food), insect bites, toilet seats.
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Diagnosis:

* Screening: ELISA (detects antibodies/antigens). * Confirmatory: Western Blot (detects specific antibodies to viral proteins), Nucleic Acid Tests (NAT/PCR - detects viral RNA/DNA).

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Treatment: — Antiretroviral Therapy (ART).

* Goal: Suppress viral replication, reduce viral load, increase CD4+ count, prevent AIDS progression. * Mechanism: Combination of drugs targeting different life cycle stages (e.g., NRTIs, NNRTIs, PIs, INSTIs). * Note: ART is not a cure, but a highly effective management.

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Prevention: — Safe sex (condoms), needle exchange programs, PrEP (Pre-exposure prophylaxis), PEP (Post-exposure prophylaxis), screening pregnant women, blood product screening.

Vyyuha Quick Recall

To remember the key enzymes of HIV and their functions, think of R.I.P. HIV:

R — Reverse Transcriptase: Converts RNA to DNA.
I — Integrase: Integrates viral DNA into host DNA.
P — Protease: Processes viral proteins for assembly.

This mnemonic helps recall the three critical viral enzymes that are also targets for antiretroviral drugs.