Prevalence of human herpesvirus 6 antibodies and DNA in allogeneic stem cell transplant patients: two-year single centre experience

INTRODUCTION: Human herpesvirus 6 (HHV-6) has been recognized as a potentially significant pathogen in hemopoietic stem cell transplant (HSCT) recipients. Different clinical manifestations have been described, including fever, skin rash, bone marrow suppression, and encephalitis. MATERIALS AND METHODS: A retrospective review of a group of 26 adult recipients of allogeneic HSCTs was conducted. Serum samples taken before transplant were examined for the presence of specific anti-HHV-6 IgM and IgG antibodies. After transplantation, quantitative real-time PCR was used to determine viral load in plasma samples from days 0-180 post-transplant. RESULTS: HHV-6 DNA was detected in plasma samples in 8 (30%) of the 26 recipients between days 18 and 40 after transplantation. All of them developed fever of unknown origin and over 50% had graft-versus-host disease features. Three individuals from this group died during detectable HHV-6 viremia. Another two recipients showed a single positive PCR result at a later time. Infection with HHV-6 was thus confirmed in 10 (38.5%) of the 26 graft recipients. CONCLUSIONS: There is a high frequency of detectable HHV-6 viral load in stem cell transplant recipients in Poland. Further investigation to monitor HHV-6 reactivation in graft recipients will be important to improve outcome for these patients.     

Central and peripheral nervous system complications following allogeneic bone marrow transplantation

Although graft vs. host disease (GvHD) is a frequent complication of allogeneic bone marrow transplantation (BMT), involvement of the central and peripheral nervous systems (CNS and PNS, respectively) has not been demonstrated conclusively. Here, we report of a patient who, following allogeneic BMT for lymphoblastic T-cell lymphoma, suffered a syndrome characterized by self-remitting cerebellar and pyramidal signs associated with a progressive involvement of the peripheral nervous system (PNS). Clinical course and laboratory findings correlated with relapses of systemic GvDH, thus suggesting the possibility that involvement of CNS and PNS may be sustained by a similar pathogenic mechanism.     

High TCR diversity ensures optimal function and homeostasis of Foxp3+ regulatory T cells

Dominant tolerance to self-antigen requires the presence of sufficient numbers of CD4(+) Foxp3(+) Treg cells with matching antigen specificity. However, the size and role of TCR repertoire diversity for antigen-specific immuno-regulation through Treg cells is not clear. Here, we developed and applied a novel high-throughput (HT) TCR sequencing approach to analyze the TCR repertoire of Treg cells and revealed the importance of high diversity for Treg-cell homeostasis and function. We found that highly polyclonal Treg cells from WT mice vigorously expanded after adoptive transfer into non-lymphopenic TCR-transgenic recipients with low Treg-cell diversity. In that system, we identified specific Treg-cell TCR preferences in distinct anatomic locations such as the mesenteric LN indicating that Treg cells continuously compete for MHC class-II-presented self-, food-, or flora-antigen. Functionally, we showed that high TCR diversity was required for optimal suppressive function of Treg cells in experimental acute graft versus host disease (GvHD). In conclusion, we suggest that efficient immuno-regulation by Treg cells requires high TCR diversity. Thereby, continuous competition of peripheral Treg cells for limited self-antigen shapes an organ-optimized, yet highly diverse, local TCR repertoire.     

T(reg) cells: collection, processing, storage and clinical use

T regulatory cells are fundamental in the maintenance of immune homeostasis and self-tolerance. Experimental models suggest the existence of two functional types of T_reg cells designated naturally occurring and induced. Interest in T_reg cells increased with evidence from experimental mouse and human models demonstrating that the immunosuppressive potential of these cells can be utilized in the treatment of various pathological conditions. The existence of a subpopulation of suppressive T cells was the subject of significant controversy among immunologists for many years. T regulatory cells limit immune activation through a variety of direct and indirect interactions, many of which are yet to be determined. Fully understanding T_reg cells biology will lead us to harnessing the capacity of these cells in order to develop strategies to prevent autoimmune disorders and tolerance to transplantation. Efficient isolation, expansion and cryopreservation strategies that comply with Good Manufacturing Practice (GMP) guidelines are prerequisites for the clinical application of human CD4+ CD25+ CD127^low FOXP3+ regulatory T cells.     

Clinical and immunological manifestations of patients with atypical severe combined immunodeficiency

Hypomorphic mutations in genes associated with severe combined immunodeficiency (SCID) or Omenn syndrome can also cause milder immunodeficiencies. We report 10 new patients with such “atypical” SCID and summarize 63 patients from the literature. The patient groups with T^lowB^low (n = 28), T^lowB⁺ (n = 16) and ADA (n = 29) SCID variants had similar infection profiles but differed in the frequency of immune dysregulation, which was observed predominantly in patients with recombination defects. Most immunological parameters were remarkably similar in the three groups. Of note, 19/68 patients with “atypical” SCID had normal T cell counts, 48/68 had normal IgG and 23/46 had at least one normal specific antibody titer. Elevated IgE was a characteristic feature of ADA deficiency. This overview characterizes “atypical” SCID as a distinct disease with immune dysregulation in addition to infection susceptibility. Lymphopenia, reduced naïve T cells and elevated IgE are suggestive, but not consistent features of the disease.     

DIFFERENTIAL DIAGNOSIS OF CHOLESTASIS FOLLOWING ALLOGENEIC HEMATOPOIETIC STEM CELL TRANSPLANTATION IN CHILDRENThe Contribution of Serum Bile Acid Levels in Relation to Other Liver Function Tests

Hepatic complications associated with cholestasis occur frequently in hematopoietic stem cell transplant recipients. Since bile acid seems to be a sensitive indicator of beginning cholestasis, the authors monitored total serum bile acid levels in addition to the standard liver function tests in 23 recipients of allogeneic transplants between June 1999 and September 2000. The observations suggest that bile acid is an early and sensitive marker of hepatic GvHD but not as specific as bilirubin. For cholestasis in absence of hepatic GvHD bile acid seems to be more sensitive than bilirubin. Routinely monitoring of bile acid after hematopoietic stem cell transplantation is not indicated.     

A murine model of graft-vs-host disease after in utero hematopoietic cell transplantation

Purpose

Graft-vs-host disease (GvHD) is a known complication of in utero bone marrow transplantation. However, GvHD has been difficult to study owing to frequent fetal demise. We describe the first consistent murine model of GvHD with postnatal survival after in utero hematopoietic cell transplantation.

Methods

A 50/50 mixture of bone marrow and splenocytes (10⁶) from 6-week-old C57/BL6 (H2-b) mice was injected intraperitoneally into Balb/c (H2-d) fetuses at e14 to 16. Live born pups were followed for clinical GvHD. Peripheral blood and hematopoietic organ chimerism was confirmed by flow cytometry and polymerase chain reaction. Organ samples were isolated for histology.

Results

Twenty-seven (75%) of 36 surviving pups displayed clinical GvHD by 2 weeks compared with 9 developmentally normal pups. Mean difference in weight between the 2 groups was 2.9 g at 7 days and 5.2 g at 14 days of life (P < .0001). All 27 pups with clinical GvHD and 1 normal-appearing pup had blood chimerism ranging from 1.5% to 65%. Eight of the 9 normal-appearing pups had 0% chimerism. Histologic analysis revealed findings of GvHD in liver, spleen, small intestine, and skin specimens of only chimeric pups.

Conclusions

A consistent murine model of GvHD can be achieved after in utero transplantation of major histocompatibility complex-mismatched bone marrow and splenocytes. Future studies will use this model to examine approaches to prevent GvHD after in utero stem cell transplantation.