Acquired ImmunoDeficiency Syndrome
يقوزر رمع راشب رامع : نيبلاطلا دادعا

Acquired immunodeficiency syndrome: is an infectious secondary form of immunodeficiency caused by the retrovirus
HIV-1, resulting in a defect in cell-mediated immune response (therefore, leads to immune suppression) that is manifested by increased opportunistic infections and to certain rare cancers
HIV : A retrovirus that causes AIDS by infecting helper T cells of the immune system. The most common type, HIV-1, is distributed worldwide, while HIV-2 is primarily confined to West
.
Africa

• HIV virus can be classified into 2 groups on the basis of their ability to infect macrophages an Thelper cells into:
• 1. M-tropic which can infect both macrophages and freshly isolated peripheral T-cell.
• 2. T-tropic which can infect only activated T-cell.

Structure of the Human Immunodeficiency
Virus

Receptors and co-receptors on the cell surface of the target cell infected by HIV

• HIV is transmitted primarily via sexual intercourse, contaminated blood transfusions and hypodermic needles, and from mother to child during pregnancy
(vertical transmission), delivery, or breastfeeding

• Pathogenesis:
• The main targets for HIV virus :
• 1.immune system “immunopathogenesis”
• 2.C.N.S

1. immunopathogenesis : the HIV infect mainly cells which have CD4 receptor on their surface, which are:
1. T-helper cells
2. Macrophages
3. Dendritic cells
4. Microglial cells
5. other cells

Immunopathogenesis of HIV disease (continued)
• the main event that occur during the infection is the destruction of CD4+ cells by HIV.
• since the CD4+ cells are very crucial to the immune system ,it ’ s destruction leads to immune suppression
• Due to immune suppression , opportunistic infections occur and neoplasms develop

• The mechanism of CD+4 destruction or loss:
• A. Death of infected cell (cytopathic effect of the virus)
• B. Activation-induced cell death (apoptosis)
• C. Killing of the infected cells by virus specific cytotoxic T-cell

• Pathogenesis of C.N.S. involvement:
• Nervous system is a major target of HIV infection either directly or indirectly.
• Macrophages and microglial cells are the predominant cell type infected with HIV
• Infected macrophages can act as HIV reservoirs and as vehicles for viral transport especially to C.N.S.

• C.N.S. injury can occur directly by the infection of the virus itself
( the mechanism is obscure because the virus doesn ’ t attack the neurons ) or indirectly by the viral products & factors produced by macrohages /microglial cells e.g. IL1,TNF, &IL6

Life cycle of HIV

• Initially, HIV-1 infects T cells and macrophages directly or is carried to these cells by Langerhans cells.
Viral replication in the regional
• lymph nodes leads to viremia and widespread seeding of lymphoid tissue. The viremia is controlled by the host immune response and the patient then enters a phase of clinical latency
.

• During this phase, viral replication in both T cells and macrophages continues unabated
• There continues a gradual destruction of CD4+ cells by productive infection
Ultimately, CD4+ cell numbers decline, and the patient develops clinical symptoms of full-blown
AIDS.

• Syndromes associated with AIDS
A . Opportunistic infection
B . Neoplasms
A . Opportunistic infection:
• Candidiasis
• Toxoplasmosis
• Herpes simplex virus
• Pneumocystis jiruvechii (formerly P.carinii)
• Cytomegalovirus
• Mycobacteria
• and others

B.Neoplasms
• Kaposi sarcoma
• B-cell non-Hodgkin lymphomas
• Invasive cancer of uterine cervix
• Primary lymphoma of the brain
• others

Oral thrush
)candidiasis)