Strong donor mononuclear cell reactivity for herpes simplex virus (HSV) antigen in HSV immune donors combined with recipient seropositivity for HSV is associated with acute graft-versus-host disease

Alloreactivity across HLA barriers is mediated by both naïve and antigen-experienced T cells

T cell responses to allogeneic targets arise predominantly from the naïve pool. However, in humans, the risk of graft-versus-host disease is increased if the donor has circulating T cells recognizing multiple persistent DNA viruses, suggesting that memory T cells also contribute to the alloresponse. To examine HLA alloreactivity, we used flow cytometry-based proliferation and cytokine production assays. We identified the clonal identity of virus-specific T cells cross-reacting with HLA-disparate targets by sequencing the T cell receptor β chains in virus-specific T cell lines restimulated with cognate and HLA-disparate targets and sorting these chains according to cytokine response. We confirmed that naïve T cells from cord blood and adult individuals responded to HLA-mismatched target cells. In addition, in adults, we identified memory T cells responding by cytokine release to HLA-mismatched targets both in direct assays and after 8 days of culture with allogeneic stimulator cells. Epstein-Barr virus-specific and cytomegalovirus-specific T cells, tested against a panel of 30 T cell antigen-presenting cells with a broad coverage of the most prominent HLA types, displayed specificity for certain mismatched HLA alleles. Sequencing of the T cell receptor β chain demonstrated a clonotypic identity of cells that responded to both viral and allogeneic stimulation. These findings show conclusively that alloresponses in humans are not confined to the naïve T cell subset, and that memory viral antigen-specific T cells can cross-react with specific mismatched HLA-peptide complexes not presenting with cytomegalovirus or Epstein-Barr virus peptides.

Risk assessment in haematopoietic stem cell transplantation: viral status

Viral infections have been important complications in the transplant procedure from the early days of stem-cell transplantation, causing significant morbidity and mortality. It is important for the management of patients to assess the risk for viral infections that might develop after the stem-cell transplantation. This can be exemplified by cytomegalovirus (CMV) and other herpesviruses, but risk assessment is also important for other viral infections. The aim of this review is to describe current knowledge regarding recipient and donor serological status for viral infections.

Poor immune reconstitution after four or five major HLA antigens mismatched T cell-depleted allogeneic and autologous stem cell transplantation

Two adults with primary liver cancer underwent liver transplantation from 5/6 and 4/6 major HLA-antigen mismatched unrelated donors. They were then conditioned with 4 x 2 Gy of total lymphoid irradiation, 120 mg/kg cyclophosphamide, 7.5 Gy total body irradiation and anti-T cell antibodies. Thereafter, the patients received T cell-depleted autologous: unrelated mismatched bone marrow in a proportion of 0.5:3.0 and 0.35:1.1 x 10(6) CD34+ cells/kg, respectively. After allogeneic stem cell transplantation (ASCT), both became mixed chimeras, as determined with polymerase chain reaction amplification of variable number tandem repeats from DNA obtained from CD3+, CD19+ and CD45+ magnetic bead-separated cells. Due to a reduction in donor T cells, the first patient was given 10(5) donor T cells/kg and became a complete donor chimera within 3 months. The second patient rejected all donor cells within 1 month after ASCT. Leucocytes normalized in both patients within 1 month. CD8+ cells normalized after 4 and 2 months in the two patients, respectively. However, CD4+, CD56+ and CD19+ cells remained low, except for a transient increase in patient 2. Lymphocyte responses to mitogens were negative in patient 1 from 1 to 5 months after ASCT. This patient also showed an oligoclonal pattern of the B cell repertoire, performed by CDR3 spectratyping. Epstein-Barr virus DNA in lymphocytes increased by 4-5 log in both patients. Prior to ASCT, recipients and donors were mutually reactive in mixed lymphocyte cultures (MLC). In the first patient, who became a complete donor chimera, the chimera cells showed no response to recipient or donor, but a positive response to third party. In the other patient, recipient cells reacted vigorously against donor lymphocytes at the time of rejection. Both patients suffered from overwhelming bacterial, fungal and viral infections, and died of pneumonia 5 and 3 months after ASCT, respectively. To conclude, with a major HLA-mismatch barrier, stable mixed chimerism seems difficult to achieve. The first patient became a full donor chimera and the second one rejected the graft. Both suffered from immune incompetence.

Acyclovir prophylaxis of oral herpes virus during bone marrow transplantation

Oropharyngeal shedding of herpes viruses (herpes simplex, cytomegalovirus) was assessed in patients on standard acyclovir prophylaxis during bone marrow transplantation (BMT) to determine the frequency of viral shedding and to assess possible oropharyngeal complications that may be associated with viral reactivation in these patients. We conducted a prospective assessment of 83 patients receiving BMT. Patients were evaluated weekly and oral surveillance cultures were completed. Shedding of herpes simplex virus (HSV) was detected in the oropharynx of 2.9% of seropositive patients on prophylactic acyclovir, and only one case of clinical oral herpetic infection was seen. Cytomegalovirus (CMV) was cultured from the oropharynx in 13.3% of CMV seropositive patients provided with prophylactic acyclovir, but no oropharyngeal lesions were attributed to CMV reactivation. No correlation was seen between HSV and CMV pretransplant serology and severity of oral mucositis and acute graft versus host disease. No effect on time to engraftment was detected. This study supports the continuing use of acyclovir prophylaxis in HSV seropositive patients receiving BMT. Acyclovir prophylaxis was effective in preventing viral shedding in all but 2.9% of patients, and only one case of clinical infection was diagnosed. The frequency of CMV shedding was approximately four times that of HSV; however, no oral lesions were attributed to CMV.

Current thoughts on the pathogenesis of graft versus host disease

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Acyclovir influence on graft versus host disease

Allogeneic bone marrow transplantation has been used for over two decades as a therapy to treat patients with malignant disease [Thomas et al., 1977; Geller et al., 1989; Clift et al., 1987; Gratwohl et al., 1990; Goldman et al., 1986; Thomas et al., 1986]. High doses of chemotherapy are administered either alone or in combination with total body irradiation in an attempt to eradicate malignant cells. The treatment may be lethal to normal bone marrow function, but this toxicity is overcome by providing bone marrow from an external source. In allogeneic bone marrow transplantation, bone marrow is obtained from an HLA identical family member or unrelated donor. In recent years the use of less well-matched donors has increased, thus expanding the use of this strategy to a larger patient population. The success rate of allogeneic bone marrow transplantation has been greatest in the treatment of haematopoietic malignancies. Patients with acute or chronic leukaemia have a 30-80 percent likelihood of being free of disease at 5 years following transplantation. The success rate depends on the stage of disease at the time of transplantation. Certain nonmalignant diseases have also been treated successfully with allogeneic bone marrow transplantation. These include severe aplastic anaemia, inborn errors of metabolism, and other genetically determined diseases [Storb et al., 1986a, 1991; Lucarelli et al., 1990; Kirkpatrick et al., 1991]. With the availability of effective antiviral therapy, treatment and prophylaxis are available for HSV, CMV, and VZV. Acyclovir has been shown to be effective in treating established infections with HSV and VZV, and in the prophylaxis against HSV, severe CMV infections, and VZV.(ABSTRACT TRUNCATED AT 250 WORDS)

Intensification of GVHD prophylaxis interferes with the effects of pretransplant herpes virus serology on the occurrence of grades II-IV acute graft-versus-host disease

The effects of pretransplant herpes virus serology on the occurrence of grades II-IV acute graft-versus-host disease (GVHD) were studied in 262 recipients and their HLA-identical family donors. In 131 recipients on standard GVHD prophylaxis (either methotrexate or cyclosporin A) significant effects were observed for donor HSV serology (seropositivity associated with increased risk for GVHD) and donor EBV serology (seronegativity associated with increased risk). However, these effects were nonsignificant in the other 131 recipients on intensified GVHD prophylaxis (i.e., methotrexate combined with cyclosporin A, in vivo anti-T-cell monoclonal antibodies, or various procedures to reduce the T-cell numbers in the transplants.