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Lymphoid organs function as major reservoirs for human immunodeficiency virus
G Pantaleo1, C Graziosi, L Butini
1Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
Summary
Lymphoid organs harbor a significantly higher human immunodeficiency virus type 1 (HIV-1) viral load than peripheral blood. This explains immune dysfunction and CD4+ T cell depletion during early HIV infection.
Area of Science:
- Virology
- Immunology
- Infectious Diseases
Background:
- Circulating CD4+ T lymphocytes are traditionally used to assess human immunodeficiency virus type 1 (HIV-1) burden.
- Early HIV infection presents low plasma viremia and CD4+ T cell counts, which do not fully explain progressive immune dysfunction.
- The discrepancy suggests that circulating cells may not accurately reflect the total HIV-1 infected cell pool.
Purpose of the Study:
- To determine if circulating CD4+ T lymphocytes accurately reflect the total HIV-1 burden.
- To comparatively analyze HIV-1 burden in peripheral blood and lymphoid tissues (lymph nodes, adenoids, tonsils) from the same patients.
- To investigate the role of lymphoid organs as potential reservoirs for HIV-1.
Main Methods:
- Collected peripheral blood and lymphoid tissue samples simultaneously from HIV-1 seropositive patients.
- Isolated mononuclear cells and sorted CD4+ T cell populations.
- Quantified HIV-1 DNA presence using polymerase chain reaction (PCR) amplification.
Main Results:
- HIV-1 infected cell frequency was significantly higher (0.5-1 log10 unit) in lymphoid tissues compared to peripheral blood.
- This finding was consistent across patients in early disease stages and one patient with AIDS.
- Lymphoid organs harbor a substantial viral load, indicating their role as major HIV-1 reservoirs.
Conclusions:
- Lymphoid organs serve as significant reservoirs for HIV-1, harboring a heavier viral load than previously indicated by peripheral blood analysis.
- The substantial viral load in lymphoid organs during early HIV infection likely contributes to progressive CD4+ T lymphocyte depletion and immune dysfunction.
- Rethinking HIV burden assessment to include lymphoid tissue analysis is crucial for understanding disease progression and developing effective therapies.