Presence of effector CD8+ T cells in hepatitis C virus-exposed healthy seronegative donors

Paola Scognamiglio, Daniele Accapezzato, Marco Antonio Casciaro, Antonella Cacciani, Marco Artini, Guglielmo Bruno, Maria Lucia Chircu, John Sidney, Scott Southwood, Sergio Abrignani, Alessandro Sette, Vincenzo Barnaba

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CTL responses against multiple hepatitis C virus (HCV) epitopes were detected in 7 of 29 (24.1%) healthy family members (HFM) persistently exposed to chronically HCV-infected patients (HCV-HFM). These precursor CTL were at very low or undetectable frequencies, as determined by limiting dilution analysis. However, when HCV-specific effector CD8+ T cells, freshly isolated from PBMC of HCV-HFM, were assessed by a sensitive enzyme-linked immunospot assay, their frequencies were several-fold higher than those of precursor CTL. These results indicate that the two assays detect two functionally distinct T cell populations and that the effector cells are not assayed by the 51Cr-release assay. Furthermore, the combination of cell depletion and enzyme-linked immunospot analyses showed that the effector cells were confined into a CD8+ CD45RO+ CD28- population. The persistence of effector CD8+ T cells specific for both the structural and nonstructural viral proteins in uninfected HCV-HFM, suggest that: 1) an immunological memory is established upon a subclinical infection without any evidence of hepatitis, in a large cohort of HCV-exposed individuals; 2) because these cells required neither restimulation nor the addition of particular cytokines in vitro for differentiating in effectors, they should be capable of prompt HCV-specific effector function in vivo, possibly providing antiviral protection; and 3) the maintenance of effector T cell responses may be sustained by persisting low-level stimulation induced by inapparent infections.

Original languageEnglish
Pages (from-to)6681-6689
Number of pages9
JournalJournal of Immunology
Issue number11
Publication statusPublished - Jun 1 1999

ASJC Scopus subject areas

  • Immunology

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    Scognamiglio, P., Accapezzato, D., Casciaro, M. A., Cacciani, A., Artini, M., Bruno, G., Chircu, M. L., Sidney, J., Southwood, S., Abrignani, S., Sette, A., & Barnaba, V. (1999). Presence of effector CD8+ T cells in hepatitis C virus-exposed healthy seronegative donors. Journal of Immunology, 162(11), 6681-6689.