Human herpesvirus 6 impairs differentiation of monocytes to dendritic cells.

OBJECTIVE: Monocyte-derived dendritic cells (DCs) play important roles in the immune response against infections and malignancies. Human herpesvirus 6 (HHV-6) infects monocytes and is reactivated in immunodeficient patients. To clarify the mechanisms of HHV-6-induced immunodeficiency, we investigated the effect of HHV-6 infection on differentiation of monocytes to DCs. METHODS: Monocytes were inoculated with or without HHV-6 and then allowed to differentiate to myeloid DCs in culture medium containing granulocyte-macrophage colony-stimulating factor and interleukin (IL)-4. The expression of cell surface molecules on DCs and the capacity of the DCs for antigen capture were examined by flow cytometric analysis. Alteration of antigen-presenting capacity induced by HHV-6 infection was examined. RESULTS: The morphology of HHV-6-infected monocyte-derived DCs was distinctly different from that of the DCs derived from mock-infected monocytes. Although expression levels of DC-associated surface antigens, including CD80, CD83, and CD86, were significantly higher on HHV-6-infected monocyte-derived DCs than on DCs derived from mock-infected monocytes, antigen-presenting capacity was significantly lower in the former group. Addition of culture supernatant of HHV-6-infected monocytes resulted in suppression of the T-lymphocyte proliferative response, and anti-IL-10 neutralizing antibody partly inhibited this suppressive effect. The antigen-presenting capacity of DCs generated from a patient with severe HHV-6 reactivation was significantly lower than that of DCs generated from the same patient in the recovery phase. CONCLUSIONS: HHV-6 infection induces immunodeficiency via impaired differentiation of DCs. These results present a new concept for the pathogenesis of HHV-6-induced immunodeficiency.

Differential regulation of perforin expression in human CD4+ and CD8+ cytotoxic T lymphocytes.

OBJECTIVE: Because perforin is an essential cytolytic mediator of cytotoxic T lymphocytes (CTLs), it is important to understand the regulatory mechanisms of perforin expression in CTLs. In the present study, we investigated the relationship between cytotoxic activity, perforin expression, and cell-activated status of CD4(+) and CD8(+) CTLs. METHODS: Herpes simplex virus-specific CD4(+) CTL clones and Epstein-Barr virus-specific CD8(+) CTL clones were established, and their cytotoxic activities were examined in both the activated and resting phases. Perforin mRNA expression was examined by reverse transcriptase polymerase chain reaction quantitatively. Transcriptional regulation of perforin was examined by electrophoretic mobility shift assay. RESULTS: The degrees of cytotoxic activity of CD8(+) CTLs did not differ significantly between the two phases; however, CD4(+) CTLs in the activated phase appeared to be significantly more cytotoxic than those in the resting phase. Similarly, expression levels of perforin mRNA in activated and resting CD8(+) CTLs did not differ significantly, but activated CD4(+) CTLs appeared to express perforin more abundantly than resting CD4(+) CTLs. In addition, it appeared that binding of STAT5 to the perforin gene promoter was increased in activated CD4(+) CTLs compared to resting CD4(+) CTLs; however, there was no significant detectable difference of STAT5 binding activity to the perforin gene promoter between activated and resting CD8(+) CTLs. CONCLUSIONS: The present study has revealed a difference in the control of perforin expression between CD4(+) and CD8(+) CTLs; that is, perforin is expressed constitutively in memory CD8(+) CTLs, but is dependent on cell activation in memory CD4(+) CTLs.

Response-oriented preemptive therapy against cytomegalovirus disease with low-dose ganciclovir: a prospective evaluation.

BACKGROUND: Preemptive therapy against cytomegalovirus (CMV) disease has succeeded in reducing the incidence of CMV disease, but the toxicity of ganciclovir remains problematic. METHODS: We prospectively evaluated the efficacy and toxicity of a preemptive protocol with ganciclovir at a reduced initial dose in 40 patients who achieved engraftment after allogeneic hematopoietic stem cell transplantation. RESULTS: Twenty-three (58%) patients had high-risk features, including transplant from an HLA-mismatched or unrelated donor, or associated acute graft-versus-host disease. CMV antigenemia assay was performed weekly, and ganciclovir was started in a risk-adapted manner, in which the initial dose of ganciclovir was fixed at 5 mg/kg/d and then adjusted based on the results of a weekly CMV antigenemia assay. In this protocol, 23 (58%) patients demonstrated positive antigenemia, and 19 (48%) received a preemptive administration of ganciclovir. Only one patient had CMV disease in the gastrointestinal system, which was successfully treated with a regular therapeutic dose of ganciclovir. Consequently, the total dose of ganciclovir was significantly less than that in a previous protocol using the conventional double dose (5 mg/kg twice daily) of ganciclovir (134 mg/kg vs. 190 mg/kg on average, P=0.046). There were no significant toxicities attributed to ganciclovir, except for neutropenia <0.5 x 109/L, which developed in three patients for 3, 4, and 14 days, respectively, with granulocyte colony-stimulating factor support. CONCLUSION: Preemptive therapy with a low initial dose of ganciclovir appeared to be effective even in high-risk patients. Further randomized controlled trial is warranted.

Limited efficacy of lamivudine against hepatitis B virus infection in allogeneic hematopoietic stem cell transplant recipients.

BACKGROUND: Reactivation of chronic hepatitis B virus (HBV) infection is a major complication when HBV carriers receive immunosuppressive therapy. Recipients of allogeneic hematopoietic stem cell transplantation (HSCT) carry the highest risk of fatal HBV disease (up to 12%). METHODS: In an attempt to identify a suitable procedure for the prevention and management of HBV reactivation, the administration of lamivudine over the course was tested in two patients. RESULTS: Generally, the patients transplant courses were successfully managed despite their difficult clinical situations: a high HBV load before transplant in one patient and intense steroid therapy for complicated acute graft-versus-host disease (GVHD) in the other patient. However, one patient showed a reactivation of HBV after discontinuing lamivudine and the other showed persistently high DNA polymerase activity despite prolonged administration of lamivudine. CONCLUSIONS: We concluded that lamivudine could have a place in the management of patients who suffer from chronic HBV infection and who are undergoing allogeneic HSCT. However, the efficacy of lamivudine seemed to be limited compared with other settings, including solid organ transplantation and autologous HSCT.

Direct recognition and lysis of leukemia cells by WT1-specific CD4+ T lymphocytes in an HLA class II-restricted manner.

Wilms tumor gene 1 product (WT1) has been recognized as an attractive target antigen of immunotherapy for various malignancies including leukemia. Because tumor-associated antigen-specific CD4+ T lymphocytes undoubtedly play an important role in the induction of an antitumor immune response, we attempted to generate WT1-specific CD4+ T lymphocytes in vitro and examined their antileukemia functions. A CD4+ T-cell line, designated NIK-1, which proliferated and produced Th1 cytokines specifically in response to stimulation with the WT1-derived peptide, WT1(337-347) LSHLQMHSRKH, in an HLA-DP5-restricted manner was established. NIK-1 exhibited cytotoxicity against HLA-DP5-positive, WT1-expressing leukemia cells but did not lyse HLA-DP5-negative, WT1-expressing leukemia cells or HLA-DP5-positive, WT1-negative cells. NIK-1 did not inhibit colony formation by normal bone marrow cells of HLA-DP5-positive individuals. This is the first report to describe WT1-specific and HLA class II-restricted CD4+ T lymphocytes possessing direct cytotoxic activity against leukemia cells.

Generation of tumor-specific, HLA class I-restricted human Th1 and Tc1 cells by cell engineering with tumor peptide-specific T-cell receptor genes.

Tumor antigen-specific CD4+ and CD8+ T lymphocytes, especially interferon-gamma (IFN-gamma)-producing type-1 helper T (Th1) and type-1 cytotoxic T (Tc1) cells, play a crucial role in tumor eradication. Adoptive transfer using tumor-specific Th1 and Tc1 cells is a promising therapeutic strategy for tumor immunotherapy. However, its clinical application has been hampered because of difficulties in generating tumor-specific Th1 cells from patients with tumors. To overcome this problem, we have developed an efficient method to prepare tumor-specific Th1 and Tc1 cells. T-cell receptor (TCR) alpha and beta genes obtained from an HLA-A24-restricted, Wilms tumor 1 (WT1) peptide-specific Tc clone were lentivirally transduced to polyclonally activated Th1 and Tc1 cells. As expected, TCR gene-modified Tc1 cells showed cytotoxicity and IFN-gamma production in response to peptide-loaded lymphoblastoid cell lines, WT1 gene-transduced cells, and freshly isolated leukemia cells expressing both WT1 and HLA-A24. Surprisingly, we further demonstrated that Th1 cells transduced with HLA-class I-restricted TCR genes also showed both cytotoxicity and cytokine production in an HLA-A24-restricted manner. In contrast to gene-modified Tc1 cells, Th1 cells produced high amounts of interleukin-2 (IL-2) in addition to IFN-gamma, which is beneficial for induction of antitumor cellular immunity. Thus, TCR gene-modified HLA-class I-restricted Th1 and Tc1 cells are a powerful strategy for the application to adoptive immunotherapy of human cancer.

Munchausen syndrome with foreign-body granuloma mimicking rheumatic diseases.

A 37-year-old man was admitted to our hospital because of fever, polyarthralgia, and subcutaneous tumors. There was swelling of the bilateral wrists and ankles, and subcutaneous tumors over the bilateral elbow joints. Despite his complaints of multiple symptoms, clinical investigations failed to reveal any abnormality. Although laboratory parameters improved rapidly after steroid therapy, the symptoms remained unchanged, and there was an enormous discrepancy between the laboratory data and his symptoms. A biopsy specimen from one of the subcutaneous tumors revealed foreign-body granuloma associated with a foreign body fragment. Because the nursing staff later discovered that the patient had been carrying out self-injection, a diagnosis of Munchausen syndrome was made. Munchausen syndrome should be included in the differential diagnosis of rheumatic diseases.

Transcriptional downregulation of DC-SIGN in human herpesvirus 6-infected dendritic cells.

DC-SIGN expressed on dendritic cells (DCs) efficiently binds and transmits various pathogens, including human immunodeficiency virus, to lymphoid tissues and permissive cells. Consequently, alteration of DC-SIGN expression may affect susceptibility and resistance to pathogens. The present study shows that infection with human herpesvirus 6 (HHV-6) induces downregulation of DC-SIGN expression on immature DCs. Expression levels of DC-SIGN mRNA and intracellular protein appeared to decrease following infection with HHV-6, indicating that downregulation of surface DC-SIGN occurs at the transcriptional level. Downregulation of DC-SIGN was not induced by inoculation of UV-inactivated HHV-6 or culture supernatant of HHV-6-infected DCs, indicating that replication of HHV-6 in DCs is required for downregulation of DC-SIGN. The present study demonstrates for the first time that expression of DC-SIGN is altered at the transcriptional level by virus infection.

Impact of stem cell source and conditioning regimen on erythrocyte recovery kinetics after allogeneic haematopoietic stem cell transplantation from an ABO-incompatible donor.

We evaluated erythrocyte recovery in 121 allogeneic haematopoietic stem cell transplantation (HSCT) recipients. There were 35 major and minor ABO-incompatible transplants, respectively, including 10 bi-directionally ABO-incompatible transplants. The use of peripheral blood stem cells facilitated erythrocyte recovery, regardless of the presence or absence of major ABO-incompatibility, and was associated with a frequent detection of anti-host isohaemagglutin early after minor ABO-incompatible transplantation, which was not associated with clinically relevant haemolysis. The use of a reduced-intensity regimen combining a purine analogue and busulphan did not delay erythrocyte recovery after major ABO-incompatible transplantation, suggesting this regimen had a strong activity against host plasma cell.