Proteasome activity is required for T lymphocyte aggregation after mitogen activation

Evaluation of a routine screening program with tuberculin skin testing on rates of detection of latent tuberculosis infection and prevention of active tuberculosis in patients with multiple myeloma at a Canadian cancer centre

Background

Chemotherapy-induced T cell dysfunction, resulting from treatment of multiple myeloma (mm), enhances the risk for reactivation of latent tuberculous infection (ltbi). However, routine screening for ltbi has its limitations. The objective of the present study was to assess the number of patients treated for ltbi both before and after the introduction of a consistent tuberculin skin test (tst) screening program for patients with mm at our cancer centre.

Methods

This retrospective observational study analyzed adult patients with mm treated with autologous hematopoietic stem-cell transplantation from 1 January 2013 to 31 December 2014, for whom tst was consistently performed at our cancer facility. Baseline demographic characteristics of patients who received tst testing and ltbi therapy were compared with those of a pre-intervention cohort of patients (1 January 2008 to 31 December 2009) who were not tested.

Results

During the post-intervention period, 170 patients with mm had a tst. In 14 patients (8.2%) results were positive, and 11 of the 14 received ltbi therapy. Of another 12 patients with radiographic imaging changes consistent with prior granulomatous disease and negative tst results, 2 were treated. No cases of tuberculosis (tb) reactivation were noted in individuals who completed ltbi therapy. One case of active tb was diagnosed in a patient with a negative tst. In contrast, in the pre-intervention matched cohort of 170 patients, no tsts were performed, and no cases of active tb were documented.

Conclusions

Patients with mm could benefit from a consistent tst testing policy coupled with subsequent ltbi therapy. However, universal testing might not be required. A targeted program combining evaluation of host risk factors, imaging findings, and screening tests might optimize ltbi diagnosis and management, and thus be effective in preventing the development of active tb in at-risk patients with mm.

Efficacy of continuous, daily, oral, ultra-low-dose 200 mg acyclovir to prevent herpes zoster events among bortezomib-treated patients: a report from retrospective study

OBJECTIVE

Herpes zoster is the most common infection in patients treated with bortezomib-containing regimens for multiple myeloma. Some clinical trials have reported on the use of acyclovir prophylaxis to decrease the incidence of herpes zoster. However, the appropriate acyclovir dose and duration of prophylaxis remain unclear. The primary objective of this study was to evaluate the efficacy of continuous oral 200 mg/day acyclovir prophylaxis and the secondary objective was to determine the risk factors for developing herpes zoster.

METHODS

We collected medical information from consecutive patients who received bortezomib with or without acyclovir prophylaxis for relapsed or refractory multiple myeloma at our hospital and retrospectively analyzed the efficacy of acyclovir prophylaxis and the parameters for predicting the risk factors for developing herpes zoster. The definition of acyclovir prophylaxis was oral continuous administration of 200 mg of once daily, without cessation, during the entire period of bortezomib treatment.

RESULTS

Six of the 33 patients in the study developed herpes zoster during bortezomib treatment. No varicella-zoster virus reactivation was observed in the 19 patients in the acyclovir prophylaxis group. The incidence of herpes zoster was significantly higher in the group that did not receive acyclovir prophylaxis (43%, 6 of 14 patients) than in the group that did (0%, 0 of 19; P = 0.003). The predictive factors for varicella-zoster virus reactivation were male sex (P = 0.035) and the use of acyclovir (P = 0.003).

CONCLUSIONS

Continuous prophylaxis by oral 200 mg/day acyclovir in multiple myeloma patients receiving bortezomib treatment is effective and sufficient in preventing herpes zoster.

Epigallocatechin-3-gallate directly suppresses T cell proliferation through impaired IL-2 utilization and cell cycle progression

Previously, we demonstrated that in vitro epigallocatechin-3-gallate (EGCG) supplementation inhibited T cell response in mouse spleen cells. In this study, we confirmed this effect of EGCG in mice fed 0.3% EGCG for 6 wk. A coculture with all the combinations of preincubating antigen-presenting cells and T cells with or without EGCG showed that EGCG suppressed antigen-induced T cell proliferation, mainly through a direct effect on T cells. To determine the mechanisms for this effect of EGCG, we stimulated purified mouse T cells with anti-CD3/CD28 in the presence of EGCG (2.5-15 micromol/L) and found that EGCG dose-dependently inhibited cell division and cell cycle progression and this effect of EGCG was more pronounced in CD4(+) than in CD8(+) T cells. Interleukin (IL)-2 concentrations in EGCG-treated cell cultures showed no difference up to 24 h but were higher in the cultures at 48 h compared with the untreated control cells. However, intracellular staining showed no difference between EGCG-treated and untreated control cells in IL-2 synthesis, but EGCG-treated cells expressed less IL-2 receptor (IL-2R) compared with untreated control cells. EGCG did not affect mRNA expression of IL-2 and IL-2R. These results indicate that EGCG-induced IL-2 accumulation in 48 h cultures is due to its reduced utilization. In summary, EGCG directly inhibits T cell proliferative response to both polyclonal and antigen-specific stimulation. CD4(+) cells are more responsive to EGCG than CD8(+) cells. Future studies should determine the effect of EGCG on CD4(+) cell subsets to assess its application in T cell-mediated autoimmune diseases.

Protein expression of lymphocytes in HLA-DR transgenic pigs by a proteomic approach

Matching donor and recipient human leucocyte antigen (HLA-II) could conquer cell-mediated rejection following transplantation. Transgenic pigs carrying HLA genes that "humanize" porcine organs, tissues, and cells were successfully generated. This study further clarifies the effect of HLA-DR transgenes on lymphocyte protein expression, via a proteomic approach. Lymphocytes were isolated from two HLA-DR transgenic pigs and three nontransgenic littermates on 157 d after birth. Soluble protein of 1x10(7) cells was separated using 2-DE. In total, 301 colloidal CBB-stained protein spots detected on all five 2-D gels were quantified. Thirty-three proteins were differentially expressed by a factor of 1.5. These proteins were subsequently identified by MALDI-TOF MS and MALDI-TOF/TOF MS/MS. These proteins were sorted into the following categories: chaperones, T-lymphocyte function, DNA/RNA processing, cytoskeleton-associated proteins, signal transduction, enzymes, and unknown. Previous studies have suggested that some of the identified proteins are associated with lymphocyte activation/proliferation. The identities of the unidentified spots and the systematic effect of these up- and down-regulated proteins on T-cell function in HLA-DR transgenic pigs require further exploration.

On the role of proteasomes in cell biology and proteasome inhibition as a novel frontier in the development of immunosuppressants

The proteasome, a large protease complex in cells, is the major machinery for protein degradation. It was previously considered a humble garbage collector, performing housekeeping duties to remove misfolded or spent proteins. Until recently, the interests of immunologists in proteasomes were focused largely on its role in antigen processing. Its real importance in cell biology has only been revealed contemporarily due to the availability of relatively specific inhibitors. It has now become increasingly clear that many aspects of immune responses highly depend on proper proteasome activity. Recently, a proteasome inhibitor has been successfully used to prevent acute as well as ongoing heart allograft rejection in mice. Such inhibitors are also efficacious in treating several autoimmune diseases, such as arthritis, psoriasis, and probably type I diabetes, in animal models. Phase II and III clinical trials of proteasome inhibitors in treating various tumors have shown promising results, and the side-effects of these drugs are tolerable. Therefore, proteasome inhibition represents a new and promising frontier in immunosuppressant development.

Global and specific translational control by rapamycin in T cells uncovered by microarrays and proteomics

Rapamycin has been shown to affect translation. We have utilized two complementary approaches to identify genes that are predominantly affected by rapamycin in Jurkat T cells. One was to compare levels of polysome-bound and total RNA using oligonucleotide microarrays complementary to 6,300 human genes. Another was to determine protein synthesis levels using two-dimensional PAGE. Analysis of expression changes at the polysome-bound RNA levels showed that translation of most of the expressed genes was partially reduced following rapamycin treatment. However, translation of 136 genes (6% of the expressed genes) was totally inhibited. This group included genes encoding RNA-binding proteins and several proteasome subunit members. Translation of a set of 159 genes (7%) was largely unaffected by rapamycin treatment. These genes included transcription factors, kinases, phosphatases, and members of the RAS superfamily. Analysis of [(35)S]methionine-labeled proteins from the same cell populations using two-dimensional PAGE showed that the integrated intensity of 111 of 830 protein spots changed in rapamycin-treated cells by at least 3-fold (70 increased, 41 decreased). We identified 22 affected protein spots representing protein products of 16 genes. The combined microarray and proteomic approach has uncovered novel genes affected by rapamycin that may be involved in its immunosuppressive effect and other genes that are not affected at the level of translation in a context of general inhibition of cap-dependent translation.