Pathogen reduction with riboflavin and ultraviolet light induces a quasi-apoptotic state in blood leukocytes

UV-stimulated riboflavin exerts immunosuppressive effects in BALB/c mice and human PBMCs

Riboflavin (RF) as a photosensitizer has been used in corneal surgery and the inactivation of blood products. However, the effect of RF on immune cells after ultraviolet (UV) light stimulation has not been investigated. This study pioneered a novel application method of RF. Firstly, UV-stimulated RF was co-cultured with human peripheral blood mononuclear cells in vitro, and the apoptosis rate of lymphocyte subsets, cell proliferation inhibition rate and concentrations of IL-1β, IL-6, IL-10, TNF-α were assessed. UV-stimulated RF was then administered intravenously to mice via the tail vein for a consecutive period of 5 days. The levels of immunoglobulin (IgG, IgM, IgA), complement (C3, C4) and cytokines (IFN-γ, IL-4, IL17, TGF-β) were detected by ELISA. Flow cytometry was employed to analyze the populations of CD3+T, CD4+T, CD8+T and CD4+T/CD8+T cells in spleen lymphocytes of mice. The data showed that UV-stimulated RF can effectively induce apoptosis in lymphocytes, and different lymphocyte subtypes exhibited varying degrees of treatment tolerance. Additionally, the proliferative capacity of lymphocytes was suppressed, while their cytokine secretion capability was augmented. The animal experiments demonstrated that UV-stimulated RF led to a significant reduction observed in serum immunoglobulin and complement levels, accompanied by an elevation in IFN-γ, IL-17 and TGF-β levels, as well as a decline in IL-4 level. In summary, the results of both in vitro and in vivo experiments have demonstrated that UV-stimulated RF, exhibits the ability to partially inhibit immune function. This novel approach utilizing RF may offer innovative perspectives for diseases requiring immunosuppressive treatment.

Polyinosinic: polycytidylic acid induced inflammation enhances while lipopolysaccharide diminishes alloimmunity to platelet transfusion in mice

Introduction

Alloimmune responses against platelet antigens, which dominantly target the major histocompatibility complex (MHC), can cause adverse reactions to subsequent platelet transfusions, platelet refractoriness, or rejection of future transplants. Platelet transfusion recipients include individuals experiencing severe bacterial or viral infections, and how their underlying health modulates platelet alloimmunity is not well understood.

Methods

This study investigated the effect of underlying inflammation on platelet alloimmunization by modelling viral-like inflammation with polyinosinic-polycytidylic acid (poly(I:C)) or gram-negative bacterial infection with lipopolysaccharide (LPS), hypothesizing that underlying inflammation enhances alloimmunization. Mice were pretreated with poly(I:C), LPS, or nothing, then transfused with non-leukoreduced or leukoreduced platelets. Alloantibodies and allogeneic MHC-specific B cell (allo-B cell) responses were evaluated two weeks later. Rare populations of allo-B cells were identified using MHC tetramers.

Results

Relative to platelet transfusion alone, prior exposure to poly(I:C) increased the alloantibody response to allogeneic platelet transfusion whereas prior exposure to LPS diminished responses. Prior exposure to poly(I:C) had equivalent, if not moderately diminished, allo-B cell responses relative to platelet transfusion alone and exhibited more robust allo-B cell memory development. Conversely, prior exposure to LPS resulted in diminished allo-B cell frequency, activation, antigen experience, and germinal center formation and altered memory B cell responses.

Discussion

In conclusion, not all inflammatory environments enhance bystander responses and prior inflammation mediated by LPS on gram-negative bacteria may in fact curtail platelet alloimmunization.

The promise of endogenous and exogenous riboflavin in anti-infection

To resolve the growing problem of drug resistance in the treatment of bacterial and fungal pathogens, specific cellular targets and pathways can be used as targets for new antimicrobial agents. Endogenous riboflavin biosynthesis is a conserved pathway that exists in most bacteria and fungi. In this review, the roles of endogenous and exogenous riboflavin in infectious disease as well as several antibacterial agents, which act as analogues of the riboflavin biosynthesis pathway, are summarized. In addition, the effects of exogenous riboflavin on immune cells, cytokines, and heat shock proteins are described. Moreover, the immune response of endogenous riboflavin metabolites in infectious diseases, recognized by MHC-related protein-1, and then presented to mucosal associated invariant T cells, is highlighted. This information will provide a strategy to identify novel drug targets as well as highlight the possible clinical use of riboflavin.

Pathogen-reduced PRP blocks T-cell activation, induces Treg cells, and promotes TGF-β expression by cDCs and monocytes in mice

Alloimmunization against platelet-rich plasma (PRP) transfusions can lead to complications such as platelet refractoriness or rejection of subsequent transfusions and transplants. In mice, pathogen reduction treatment of PRP with UVB light and riboflavin (UV+R) prevents alloimmunization and appears to induce partial antigen-specific tolerance to subsequent transfusions. Herein, the in vivo responses of antigen-presenting cells and T cells to transfusion with UV+R-treated allogeneic PRP were evaluated to understand the cellular immune responses leading to antigen-specific tolerance. Mice that received UV+R-treated PRP had significantly increased transforming growth factor β (TGF-β) expression by CD11b+ CD4+ CD11cHi conventional dendritic cells (cDCs) and CD11bHi monocytes (P < .05). While robust T-cell responses to transfusions with untreated allogeneic PRP were observed (P < .05), these were blocked by UV+R treatment. Mice given UV+R-treated PRP followed by untreated PRP showed an early significant (P < .01) enrichment in regulatory T (Treg) cells and associated TGF-β production as well as diminished effector T-cell responses. Adoptive transfer of T-cell-enriched splenocytes from mice given UV+R-treated PRP into naive recipients led to a small but significant reduction of CD8+ T-cell responses to subsequent allogeneic transfusion. These data demonstrate that pathogen reduction with UV+R induces a tolerogenic profile by way of CD11b+ CD4+ cDCs, monocytes, and induction of Treg cells, blocking T-cell activation and reducing secondary T-cell responses to untreated platelets in vivo.

A novel cancer immunotherapy utilizing autologous tumour tissue

BACKGROUND

With the recent interest in personalized medicine for cancer patients and immune therapy, the field of cancer vaccines has been resurrected. Previous autologous, whole cell tumour vaccine trials have not produced convincing results due, in part to poor patient selection and inactivation methos that are harsh on the cells. These methods can alter protein structure and antigenic profiles making vaccine candidates ineffective in stimulating immune response to autochthonous tumour cells.

MATERIALS AND METHODS

We investigated a novel method for inactivating tumour cells that uses UVA/UVB light and riboflavin (vitamin B2) (RF + UV). RF + UV inactivates the tumour cells' ability to replicate, yet preserves tumour cell integrity and antigenicity.

RESULTS

Our results demonstrate that proteins are preserved on the surface of RF + UV-inactivated tumour cells and that they are immunogenic via induction of dendritic cell maturation, increase in IFNγ production and generation of tumour cell-specific IgG. Moreover, when formulated with an adjuvant ('Innocell vaccine') and tested in different murine tumour primary and metastatic disease models, decreased tumour growth, decreased metastatic disease and prolonged survival were observed. In addition, immune cells obtained from tumour tissue following vaccination had decreased exhausted and regulatory T cells, suggesting that activation of intra-tumoural T cells may be playing a role leading to reduced tumour growth.

CONCLUSIONS

These data suggest that the RF + UV inactivation of tumour cells may provide an efficacious method for generating autologous whole tumour cell vaccines for use in cancer patients.

Photodynamic therapy regulates fate of cancer stem cells through reactive oxygen species

Photodynamic therapy (PDT) is an effective and promising cancer treatment. PDT directly generates reactive oxygen species (ROS) through photochemical reactions. This oxygen-dependent exogenous ROS has anti-cancer stem cell (CSC) effect. In addition, PDT may also increase ROS production by altering metabolism, endoplasmic reticulum stress, or potential of mitochondrial membrane. It is known that the half-life of ROS in PDT is short, with high reactivity and limited diffusion distance. Therefore, the main targeting position of PDT is often the subcellular localization of photosensitizers, which is helpful for us to explain how PDT affects CSC characteristics, including differentiation, self-renewal, apoptosis, autophagy, and immunogenicity. Broadly speaking, excess ROS will damage the redox system and cause oxidative damage to molecules such as DNA, change mitochondrial permeability, activate unfolded protein response, autophagy, and CSC resting state. Therefore, understanding the molecular mechanism by which ROS affect CSCs is beneficial to improve the efficiency of PDT and prevent tumor recurrence and metastasis. In this article, we review the effects of two types of photochemical reactions on PDT, the metabolic processes, and the biological effects of ROS in different subcellular locations on CSCs.

A small allelic variant in donor class I MHC is sufficient to induce alloantibodies following transfusion of standard or pathogen-reduced platelets in mice

BACKGROUND AND OBJECTIVES

Alloimmunization targeting major histocompatibility (MHC) antigens is common following platelet transfusion. Pathogen reduction of platelets can block alloimmunization to MHC in mice and induce partial antigen-specific tolerance to subsequent transfusions. This study utilized small allelic variants to evaluate the relative contributions of class I and class II MHC to the alloresponse against untreated or pathogen-reduced platelets.

MATERIALS AND METHODS

C57BL/6 (B6) K^bm1 and B6 IA^bm12 mice with small variants in the class I K^b and class II IA^b alleles, respectively, were used as platelet donors for wild-type B6 recipients. Both untreated and pathogen-reduced platelet-rich plasma (PRP) transfusions were evaluated for immunogenicity by measuring antibody responses and ex vivo cytokine production.

RESULTS

Both the K^bm1 and IA^bm12 alleles induced antibody responses, though the response to K^bm1 was greater. Pathogen reduction blocked the antibody responses to IA^bm12 , but not to K^bm1 . Both the K^bm1 and IA^bm12 alleles primed ex vivo cytokine responses that were blocked with pathogen reduction, though responses to IA^bm12 were broader and larger (K^bm1 responses: IFN-γ, TNFα, and MIP-1β; IA^bm12 responses: IFN-γ, TNFα, IL-1β, IL-10, IL-13, and GM-CSF). Pathogen-reduced K^bm1 PRP did not appear to induce any tolerance to subsequent untreated K^bm1 PRP transfusions.

CONCLUSION

Minor allelic variants in both the class I and class II MHC are capable of inducing an alloresponse to transfusion. The K^bm1 PRP induced alloantibodies even with pathogen reduction and did not show signs of inducing the partial tolerance to subsequent transfusions observed with a larger MHC mismatch.