Pathogenesis and Pathology of HIV/AIDS

Molecular Mechanisms of HIV Infection

HIV (Human Immunodeficiency Virus) is a retrovirus that targets the human immune system, specifically CD4+ T cells, leading to progressive immune dysfunction and AIDS (Acquired Immunodeficiency Syndrome). The infection follows several key stages:

1. Viral Entry

HIV primarily infects CD4+ T cells by attaching to the CD4 receptor and co-receptors (CCR5 or CXCR4) on the host cell membrane.

• The viral envelope glycoproteins (gp120 and gp41) facilitate fusion with the host cell.
• Once attached, the viral RNA enters the cytoplasm.

2. Reverse Transcription

HIV carries the enzyme reverse transcriptase, which converts its single-stranded RNA genome into complementary DNA (cDNA).

• Reverse transcriptase lacks proofreading ability, leading to mutations that promote viral diversity.

3. Integration into Host Genome

The cDNA is transported into the nucleus and integrated into the host genome using the viral enzyme integrase.

• Integration allows HIV to persist within host cells indefinitely.

4. Replication and Assembly

Once integrated, HIV hijacks the host’s cellular machinery to produce viral RNA and proteins.

• New virions assemble and bud off from the host cell.

5. Pathogenesis

The destruction of CD4+ T cells leads to immune system collapse, increasing susceptibility to opportunistic infections.

• Clinical manifestations include opportunistic infections (e.g., tuberculosis, candidiasis) and malignancies (e.g., Kaposi's sarcoma).