JC virus-specific cytotoxic T lymphocytes in individuals with progressive multifocal leukoencephalopathy

Abstract

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by a reactivation of the polyomavirus JC (JCV) within a setting of immunosuppression. The nature of the immune response that contains replication of this virus is unknown. We have explored JCV-specific cellular immune responses in patients with PML and control subjects. JCV antigen-stimulated peripheral blood mononuclear cells (PBMC) of four human immunodeficiency virus (HIV)-infected patients who were survivors of PML and one HIV-uninfected patient recently diagnosed with PML lysed autologous B-lymphoblastoid cell lines expressing either the JCV T regulatory protein or the VP1 major capsid protein. This lysis was mediated by CD8(+) T lymphocytes and was major histocompatibility complex class I restricted. These cells were therefore cytotoxic T lymphocytes (CTL). JCV-specific CTL could not be detected in PBMC of three HIV-infected PML patients who had progressive neurologic disease and an eventual fatal outcome. These data suggest that the JCV-specific cellular immune response may play a crucial role in the containment of PML. This finding may also prove useful as a favorable prognostic marker in the clinical management of these patients.

FIG. 1

Radioimmunoprecipitation of the JCV VP1 and T proteins expressed by recombinant vaccinia viruses. B-LCL from an HIV-negative patient with PML were infected at an MOI of 10 PFU/cell for 16 h with either the recombinant vaccinia virus containing the VP1 (vVP1) or T (vT) genes, or the wild-type vaccinia virus (wt). Uninfected cells served as controls (ctrl). The monoclonal antibodies NCL-JC, specific for the VP1 protein, and SV40 T, which cross-reacts with the T protein of JCV, were used for the immunoprecipitations. Protein products of approximately 43 and 86 kDa were identified, corresponding to the expected size of the JCV VP1 and T proteins, respectively.

FIG. 2

PBMC from HIV type 1 (HIV-1)-infected survivors of PML (HIV+/PML S # 1 to 4) have cytolytic activity specific for the JCV T and VP1 proteins. T- and VP1-specific effector cells could be detected in three of four and four of four HIV-positive PML survivors, respectively. PBMC from one recently diagnosed HIV-negative PML patient who showed clinical improvement had cytolytic activity against the VP1 protein. PBMC were stimulated with autologous, fixed B-LCL expressing the T or VP1 protein in interleukin-2-containing medium and assessed for effector function using autologous target cells infected with recombinant vaccinia virus-T, -VP1, or the wild-type vaccinia virus. The percent specific lysis indicates the difference in specific ⁵¹Cr release between cells infected with the T- or VP1-expressing vaccinia virus and those infected with the wild-type vaccinia virus. E:T ratios are shown in the box in the upper left panel.

FIG. 3

PBMC of an HIV-negative PML patient stimulated with autologous fixed B-LCL infected with a recombinant vaccinia virus expressing the JCV VP1 protein (filled squares), but not with the wild-type vaccinia virus (open circles), mediated cytolytic activity specific for the JCV VP1 protein.

FIG. 4

PBMC from an HIV-1-infected survivor of PML mediated cytolytic activity specific for the JCV T and VP1 proteins detectable in three successive assays. The average percentage of specific lysis and standard deviation at an E:T ratio of 20:1 was 19% ± 6% for JCV T protein and 16% ± 4.6% for the VP1 protein.

FIG. 5

Unfractionated and CD4⁺ T lymphocyte-depleted but not CD8⁺ T lymphocyte-depleted PBMC of an HIV-1-infected survivor of PML mediated cytolytic activity specific for the JCV T and VP1 proteins.

FIG. 6

PBMC of an HIV-1-infected survivor of PML lysed autologous target cells but not fully MHC class I-mismatched target cells infected with recombinant vaccinia viruses expressing the JCV protein T or VP1.