2. Human immunodeficiency virus (HIV) is the
causative agent for AIDS.
HIV is a retrovirus that contains only RNA. HIV
is a sexually transmitted disease.
Infection is aided by Langerhans cells in
mucosal epithelial surfaces, which can
become infected.
Infection is also aided by the presence of
other sexually transmitted diseases that can
produce mucosal ulceration and
inflammation.
3. The CD4+ T-lymphocytes have surface
receptors to which HIV can attach to promote
entry into the cell. The infection extends to
lymphoid tissues which contain follicular
dendritic cells that can become infected and
provide a reservoir for continuing infection of
CD4+ T- lymphocytes.
HIV can also be spread via blood or blood
products, most commonly with shared
contaminated needles used by persons
engaging in intravenous drug use.
Mothers who are HIV infected can pass the
virus on to their fetuses in utero or to infants
via breast milk.
4. The source of HIV is a sick person or a virus
carrier. The patients are infective during all
the life.
When HIV infects a cell, it must use its reverse
transcriptase enzyme to transcribe its RNA to
host cell proviral DNA. It is this proviral DNA
that directs the cell to produce additional HIV
virions, which are released.
When the CD-4 lymphocyte count drops
below 200/microliter, then the stage of
clinical AIDS has been reached. This is the
point at which the characteristic opportunistic
infections and neoplasms of AIDS appear.
5. The clinical spectrum of HIV infection is now
recognized to comprise
1. Acute viral infection sometimes associated with
immune complex disease.
2. Persistent generalized lymphadenopathy.
3. Chronic active viral infection with constitutional
symptoms or AIDS related complex.
4. Immunodeficiency leading to opportunistic
infections or tumors (AIDS).
5. Chronic encephalopathy caused by HIV
6. Chronic active viral infection with
immunocomplex disease (such as
thrombocytopenic purpura).
6. Prolonged fever of unclear origin.
Chronic diarrhea (not less than 2 months).
Unexplainable body weight loss (by 10% or
more).
Pneumonia of unclear origin resistant to
standard therapy.
Lymphopenia.
7.
8. At autopsy the gross pathology of AIDS can
be split into three general categories as
follows:
1. The morphologic manifestations of
profound lymphoid depletion.
2. Infections caused by opportunistic
pathogens.
3. Unusual neoplasms such as Kaposi’s
sarcoma and high-grade lymphoma.
9. The early stage of HIV is characterized by
enlarged lymph nodes and the follicular
hyperplasia.
With disease progression, the frenzy of B-cell
proliferation subsides and gives way to a pattern
of severe follicular involution. The follicles are
depleted of cells; and the organized network of
follicular dendritic cells is disrupted. The
germinal centres may even become hyalinised.
These “burnt-out” lymph nodes are atrophic and
small and may harbor numerous opportunistic
pathogens. In the empty-looking lymph nodes
and in other organs, the presence of infectious
agents may not be readily apparent without the
application of special stains.
10. In later stages of AIDS, spleen and thymus
also appear to be “wastelands”.
Non-Hodgkin’s lymphomas, involving the
nodes as well as extranodular sites, such as
the liver, gastrointestinal tract, and bone
marrow, are primarily high-grade diffuse B-
cell neoplasms.
Neurologic complications, especially the
AIDS-dementia is an important cause of
morbidity in patients in advanced stages of
infection. The pathologic abnormalities in
patients with AIDS-dementia complex are
variable. Multinucleated cells in the brain are
found in a subgroup of patients with severe
disease.
11. These cells are derived from macrophages
and support viral replication. These are thus
markers of productive infection. All
histopathlogic abnormalities are most
prominent in the subcortical structures, and
besides multinucleated cells they include
diffuse pallor of the white matter and
vacuolar myelopathy.
Lymphocytic meningitis is seen in patients
around the time of seroconversion and is
defined as occurring in the absence of any
demonstrable opportunistic pathogens.
12. HIV encephalitis is a multifocal process
characterized by inflammatory foci including
multinucleated giant cells, mainly seen in
white matter, basal ganglia and brain stem.
Diffuse poliodystrophy is the term applied to
neuronal loss, microglial activation and
gliosis in CNS grey matter.
Cerebral vasculitis is seen most prominently
in childhood HIV disease of the brain.
