Viral Structure and Replication

Viral Structure and Replication

• Viruses are not made of cells and can't sustain themselves or replicate independently.
• Composed of nucleic acids (genome) and proteins.
• Viral life cycles vary, with examples being the lytic and lysogenic cycles.

Lytic Cycle

• The virus injects its genome, hijacking host cell machinery for replication.
• New viruses assemble and are released when the host cell bursts.

Lysogenic Cycle

• Viral DNA integrates with host DNA, replicating along with the host's DNA.
• This cycle can be dormant for extended periods.

Viral Outcomes

• Lytic cycle (cell death)
• Persistent infection (continuous viral release)
• Latent infection (dormant virus)
• Transformation (cancer due to viral integration)

Viral Titer

• Plaque assays to measure viral concentration.
• Each plaque arises from a single virus and cell.

Viral Classification

• Viruses classified by their genetic material.
  • dsDNA (double-stranded DNA)
  • ssDNA (single-stranded DNA)
  • dsRNA (double-stranded RNA)
  • ssRNA (single-stranded RNA)

HIV/AIDS

• HIV (Human Immunodeficiency Virus) is not the same as AIDS (Acquired Immune Deficiency Syndrome).
• HIV is the infectious virus, and AIDS is the late-stage disease.
• Early HIV infections may have gone undiagnosed until the disease spread to the point that it became an epidemic.
• Discovery traced back to researchers in France and the U.S.
• HIV-1 (most common type) originated in chimpanzees and likely transferred to humans through bushmeat consumption.

HIV Transmission

• Transmission through bodily fluids (blood, semen, vaginal secretions, breast milk)
• Transmitted horizontally (sexual contact, sharing needles)
• Transmitted vertically (mother to child during pregnancy, birth, or breastfeeding.)

HIV Biology and Structure

• HIV is a retrovirus (RNA genome converted to DNA) and a lentivirus (slow progression).
• HIV contains a capsid, envelope, RNA, enzymes (Reverse Transcriptase), and glycoproteins.

HIV Epidemiology

• Over 36 million people globally live with HIV (2023).
• New HIV infections and AIDS-related deaths show a significant reduction.
• Africa has the highest prevalence.

HIV Progression and Opportunistic Infections

• HIV weakens the immune system, making the body vulnerable to secondary infections (Opportunistic infections).
  • Examples include Tuberculosis, Cryptococcal meningitis, Karposi's sarcoma, Pneumocystis pneumonia and Toxoplasmosis.

HIV Diagnosis and Treatment

• Diagnosis utilizes antibody tests and nucleic acid tests.
• Treatment involves antiretroviral therapy (ART) which prevents a cure but decreases viral load.

HIV Prevention

• Pre-exposure prophylaxis (PrEP)
• Post-exposure prophylaxis (PEP)
• Screening for HIV
• Use of condoms
• Prevention of Mother-to-Child Transmission (PMTCT)

Future HIV Treatments

• Research efforts focus on preventative measures, such as vaccines and potential cures.
• Significant breakthroughs in individual treatment, such as the Timothy Ray Brown case.