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HIV-1

HIV encephalitis. Nongranulomatous infiltrates centered loosely about blood vessels in the cerebral white matter (shown here) or basal ganglia and dominated by macrophages, including multinucleated forms resulting from retrovirally mediated cell fusion, characterize infection of the CNS by this agent. The associated astrogliosis and spongy rarefaction are common accompanying features.

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Definition

HIV cause leukoencephalopathy characterized by microglial nodules, patchy demyelination and multinucleated giant cells.

Pathogenesis

Retroviral infection1,2
No particular tropism for neuroectodermal cell types
Replication largely within;
- marrow-derived macrophages
- microglia

Histopathology

Unique neuropathologic alterations
Loosely arrayed, vasocentric, or paravascular inflammatory infiltrates (Fig. 1
Fig. 1: HIV encephalitis. Nongranulomatous infiltrates centered loosely about blood vessels in the cerebral white matter (shown here) or basal ganglia and dominated by macrophages, including multinucleated forms resulting from retrovirally mediated cell fusion, characterize infection of the CNS by this agent. The associated astrogliosis and spongy rarefaction are common accompanying features.
):
- concentrated in:
  - cerebral hemispheric white matter
  - basal ganglia
  - rostral brainstem
- dominated by:
  - mononucleated macrophages:
  - multinucleated macrophages:
    - reflecting virally mediated cell fusion:
      - the characteristic cytopathic effect of this and other members of the lentivirus subfamily of retroviruses
Accompanying changes3 include:
- diffuse astrogliosis
- microglial activation
- generalized pallor of cerebral white matter
- brain atrophy
Electron microscopy:
- fully formed virions:
  - harbored and released by mononucleated and multinucleated macrophages
  - found:
    - budding from plasmalemma
    - aggregated in membrane-delimited intracytoplasmic vacuoles
    - lying free in cytoplasm
- mature particle:
  - spherical
  - average 100–120mm diameter
  - cylindrical or bar-shaped nucleoid:
    - usually:
      - eccentric location
      - enclosed by limiting membrane

Differential Diagnosis

Select up to 2 differential diagnoses to compare with HIV-1

References

1 Rosenblum MK. Human immunodeficiency virus lesions of the central nervous system. Connor DH, Chandler FW, Schwartz DA, Manz HJ, Lack EE editor. In: Pathology of infectious diseases. vol. 1:Stamford: Appleton and Lange; 1997.

2 Sharer LR. Pathology of HIV–1 infection of the central nervous system. A review. J Neuropathol Exp Neurol. 1992;51:3–11.

3 Sotrel A, Dal Canto MC. HIV–1 and its causal relationship to immunosuppression and nervous system disease in AIDS. A review. Hum Pathol. 2000;31:1274–1298.

Last updated: 30 Dec 2006