Assessing cumulative exposure to maintenance immunosuppressive drugs: Metrics, outcomes, and implications for transplant patients

Immunosuppressive drugs are used in the management of transplant patients to prevent organ rejection. However, immunosuppression can be associated with adverse effects such as infections and cancers. This study aimed to characterize the measures of cumulative immunosuppressive drug exposure (CIDE) used in the literature and their associated outcomes in transplant patients. A literature search was conducted in Ovid MEDLINE, Ovid EMBASE, Cochrane CENTRAL, and Cochrane Database of Systematic Reviews using search terms related to maintenance immunosuppressants and CIDE. Study risk of bias was assessed using the Quality in Prognostic Studies tool. Thirty-one articles were included in this qualitative synthesis. Sixteen articles (52 %) calculated the total dose of immunosuppression over the treatment period, while eight (26 %) used area-under-the-curve of trough level concentrations to quantify CIDE. Five (16 %) articles investigated time-weighted metrics of calcineurin inhibitors and four (13 %) used other metrics that could not be categorized into the previous groups. Most studies investigated CIDE with calcineurin inhibitors and used additive dosing methods. This approach was also popular with corticosteroids and multi-drug exposures. The variety of metrics used in the literature reveals a lack of standardization in the evaluation of CIDE and long-term outcomes. Future studies should validate these metrics for clinical application, especially pertaining to infectious outcomes.

Effects of methoxypoly (Ethylene glycol) mediated immunocamouflage on leukocyte surface marker detection, cell conjugation, activation and alloproliferation

Tissue rejection occurs subsequent to the recognition of foreign antigens via receptor-ligand contacts between APC (antigen presenting cells) and T cells, resulting in initialization of signaling cascades and T cell proliferation. Bioengineering of donor cells by the covalent attachment of methoxypolyethylene glycol (mPEG) to membrane proteins (PEGylation) provides a novel means to attenuate these interactions consequent to mPEG-induced charge and steric camouflage. While previous studies demonstrated that polymer-mediated immunocamouflage decreased immune recognition both in vitro and in vivo, these studies monitored late events in immune recognition and activation such as T cell proliferation. Consequently little information has been provided concerning the early cellular events governing this response. Therefore, the effect of PEGylation was assessed by examining initial cell-cell interactions, changes to activation pathways, and apoptosis to understand the role that each may play in the decreased proliferative response observed in modified cells during the course of a mixed lymphocyte reaction (MLR). The mPEG-modified T cells resulted in significant immunocamouflage of lymphocyte surface proteins and decreased interactions with APC. Furthermore, mPEG-MLR exhibited decreased NFκB pathway activation, while exhibiting no significant differences in degree of cell death compared to the control MLR. These results suggest that PEGylation may prevent the direct recognition of foreign alloantigens by decreasing the stability and duration of initial cell-cell interactions.

Minimization of steroids in liver transplantation

Because of the markedly improved short-term results of liver transplantation (LT) and persistently high number of long-term complications, the attention of transplant physicians should be focused on minimizing immunosuppressive therapy as much as possible. Steroid-based immunosuppression is responsible for a substantial post-LT morbidity and mortality, hence, minimization of its use is of utmost importance to improve the quality of life of the successfully transplanted liver recipient. This literature review shows that LT can be performed safely with steroid-minimal immunosuppression without compromising graft and patient survival. The tendency in clinical practice is to move more and more from steroid withdrawal to steroid avoidance protocols.