microbio 2125 unit 6 part 20 - HIV Infection and Acquired Immunodeficiency Syndrome (AIDS)

Etiological Agent:

Human Immunodeficiency Virus (HIV-1 and HIV-2)
genus: Lentivirus

Distinguishing characteristics of etiological agent:

• Retrovirus, genus Lentivirus

• Contains single-stranded RNA (ssRNA)

• Uses reverse transcriptase to create double-stranded DNA from ssRNA

• Viral DNA permanently integrates into host genome

• Infects cells with CD4 receptor and co-receptor

Virulence Factor(s):

• Reverse transcriptase enzyme

• Ability to integrate into host DNA (latency or lytic infection)

• Direct cell-to-cell fusion via syncytia formation

• Persistent infection of macrophages and T helper cells

• Progressive immune system depletion

Predisposing Factors:

• Unprotected sex (especially anal)

• Intravenous (IV) drug use

• Multiple sexual partners

• Blood transfusions (rare today due to screening)

• Perinatal transmission (birth/breastfeeding)

• Co-infection with other STDs

Transmission:

• Direct contact with infected blood, semen, vaginal secretions

• Sexual intercourse

• Sharing contaminated needles/syringes

• From mother to child during childbirth or breastfeeding

• Not spread by saliva or casual contact

• Virus is fragile outside the body and sensitive to heat/disinfectants

Syndrome (signs + symptoms):

• Initial infection: mononucleosis-like symptoms (fever, fatigue, swollen glands)

• Asymptomatic phase: 2–15 years (average ~10 years)

• AIDS phase: occurs when CD4 count < 200 cells/μL

  • Fever, chronic diarrhea, weight loss

  • Swollen lymph nodes

  • Neurological symptoms

  • Opportunistic infections (e.g., Pneumocystis pneumonia, TB)

  • Malignancies (e.g., Kaposi's sarcoma)

Affected body region/system:

• Immune system, especially CD4+ T cells

• Central nervous system (via infected macrophages)

• Systemic spread to multiple organs

Treatment:

• No cure

• HAART (Highly Active Antiretroviral Therapy):

  • Combines 2 reverse transcriptase inhibitors + 1 protease inhibitor

  • Can include integrase and fusion inhibitors

• Goal: suppress viral load, preserve immune function

• PrEP for high-risk individuals as preventative measure

• Post-exposure prophylaxis (PEP) for recent exposure

Prevention:

• No vaccine

• Behavioral modifications (monogamy, safe sex practices, condom use)

• Routine testing and early treatment

• Needle exchange programs

• Pre-exposure prophylaxis (PrEP) reduces infection risk by ~92%

• Universal precautions in healthcare settings

Other notes:

• First case recognized in 1981; retroactively traced to 1959

• Still a major global health issue with ~37 million infected worldwide (as of 2017)

• Major cause of death in 25–44 y.o. population before antiretroviral therapy

• Diagnosis confirmed through serological testing (ELISA, Western blot) and clinical criteria (CD4 count, AIDS-defining illnesses)

diagnosis that must be memorized

• Diagnosis of AIDS is made when person meets following criteria:

1. Positive for virus

2. They fulfill one of additional criteria:

   1. CD4 count of fewer than 200 cells/μl of blood

   2. CD4 cells account for fewer than 14% of all lymphocytes

   3. Experience one or more of CDC-provided list of AIDS-defining illnesses