HUMAN IMMUNODEFICIENCY VIRUS (HIV)

OVERVIEW

• HIV stand for human immunodeficiency virus.

• HIV is causative agent of AIDS.

• Virus that commonly attack immune system, specially CD4 cells (T cells) which help the body fight against infection.

• HIV can lead to the disease Acquired Immunodeficiency Syndrome (AIDS

• HIV is categorized into two main types: HIV-1 and HIV-2.

• HIV-1 is most common & widespread, while HIV-2 commonly seen in Africa.

• p24 antigen is the earliest viral marker appear in the blood.

MORPHOLOGY

• Shape: Spherical shape.

• Size: 90 to 150 nanometers (nm).

• Symmetry: Icosahedral symmetry

• Envelope: Enveloped present.

• Single stranded RNA virus.

• Capsid: A cylindrical protein shell composed of p24 proteins, which contains the genetic material of the virus.

• HIV virus has a unique replication process, when HIV entering in human body it uses reverse transcription to convert its RNA genome into DNA.

VIRAL GENES & ANTIGENIC STRUCTURE

• HIV Contain three structure gene –

a. Gag gene:

o code for the core & shell of the virus

o Precursor protein P55

o P17 constituent the matrix shell antigen

o P24 & P15 constitute the core antigen

b. Pol gene:

o Code for viral enzyme such as reverse transcriptase protease & integrase P32, P51 & P66.

c. Env gene:

o Code for envelop glycoprotein(gp160).

• Non-structural gene –

o Tat- Transactivator gene

o Nef- Negative factor gene

o Rev- Regulator of virus gene

o Vif- Viral infectivity gene

o Ltr- Long terminal repeat

PATHOGENESIS

1. Source of infection:

   The primary sources of Human Immunodeficiency Virus (HIV) infection include:

   • Blood

   • Semen

   • Saliva

   • Urine

   • Tears

   • Breast milk

2. Mode of infection:

• Sexual contact –

  • Due to unprotected sexual contact.

  • Risk increase in those individual who have more than one sexual partner.

  • Transmission occurs in both homosexual & heterosexual individual.

• Parenteral transmission –

  • It occurs after receiving infected blood

  • Blood transfusion

  • Contaminated syringes & needles.

• Perinatal transmission –

  • Infection transmitted to child through transpalcentally.

  • During birth

  • During breast-feeding

3. Incubation period:

• The incubation period for HIV is around 2 to 6 weeks(average 3 week).

4. Stages of HIV infection:

• Acute HIV Infection:

  • Characterized byacute onset of fever, fatigue, malaise, sore throat, skin rashes, swollen lymph node, fatigue, etc.

  • The virus is highly transmissible during this stage.

• Asymptomatic stage:

  • After the acute stage, the virus enters in asymptomatic stage where the individual are usually well but show positive HIV antibody test.

• Symptomatic HIV Infection:

  • CD4+ T lymphocytes count falls below 400/mm³

  • Some patient may develop symptoms like fever, weight loss, diarrhea, night seating, & opportunistic infection.

• AIDS (Acquired Immunodeficiency Syndrome):

  • AIDS is the end stage of HIV infection

  • Occurs when the immune system is totally damaged.

  • In AIDS the CD4+ cells number is remains only 200/mm³

LABORATORY DIAGNOSIS

• Laboratory diagnosis for HIV infection include various test.

# Specific test for HIV infection

1. Antigen detection: Virus antigen (P24) & reverse transcriptase may be detected in blood after two week.

2. Virus isolation: Isolated from CD4 lymphocytes of pheripheral blood, bone marrow & serum.

3. Detection of viral nucleic acid: It can detected through polymerase chain reaction(PCR).

4. Antibody detection: Most common technique for diagnosis.

5. Screening test: ELISA

6. Supplement test: Western blot test

# Non-specific test

1. Total leucocyte count: less than 4000 cell/microliter

2. Platelet count: Thrombocytopenia

3. Tuberculin test

# Test for opportunistic pathogen

1. Opportunistic pathogen: Most of these infection are diagnosis by direct microscopy.

2. Tumor: malignant tumor are more frequently associated in homosexual who having AIDS.

PROPHYLAXIS

• Pre-Exposure Prophylaxis

  • Pre-Exposure Prophylaxisinvolves taking medications before potential exposure to HIV to reduce the risk of infection.

• Post-Exposure Prophylaxis (PEP):

  • post exposure prophylaxisinvolves taking medications after a potential exposure to HIV to prevent infection. PEP is typically recommended for situations such as unprotected sexual intercourse with a partner of unknown HIV status, needlestick injuries, or other occupational exposures.

PREVENTION

1. Sexual contact: Use of Condom can prevent transmission of the virus

2. Contaminated syringes or needles should not share

3. During blood transfusion screening of blood is necessary

4. Isolation of AIDS patient