Ex vivo expansion of human cytomegalovirus‐specific cytotoxic T cells by recombinant polyepitope: implications for HCMV immunotherapy

Abstract

Stem cell transplantation (SCT) remains the most effective curative therapy for the majority of hematopoietic malignancies. Unfortunately, SCT is limited by its toxicity and infectious complications that result from profound immunosuppression. In particular, acquisition of exogenous or reactivation of endogenous human cytomegalovirus (HCMV) is common after SCT. More recently, reconstitution of host immunity through augmentation of anti-HCMV T cell responses has been proposed as an exciting candidate therapy to avoid the requirement for antiviral drug use. Here we have developed a novel antigen presentation system based on a replication-deficient adenovirus that encodes multiple HLA class I-restricted epitopes from eight different antigens of HCMV as a polyepitope (referred to as AdCMVpoly). Ex vivo stimulation of peripheral blood mononuclear cells with AdCMVpoly consistently showed rapid stimulation and expansion of multiple epitope-specific T cells that recognized endogenously processed epitopes presented on virus-infected cells. Interestingly, the AdCMVpoly expression system is capable of expanding antigen-specific T cells even in the absence of CD4 + T cells. These studies show the effectiveness of a polyepitope antigen presentation system for reproducible expansion of antigen-specific T cells from immunocompetent and immunocompromised settings.

Immunobiology of Human Cytomegalovirus: from Bench to Bedside

“…7). This strategy dramatically increased the precursor frequency of antigen-specific T cells; however, the infusion of virus-specific T cells with single-epitope specificity may allow variants to (47,66,173,194,216,217,276). PE, phycoerythrin; PBMC, peripheral blood mononuclear cells.…”

“…22,2009 IMMUNE RESPONSE TO HCMV 89 escape and also limit the use of this technology to patients who carry a single HLA allele. More recently, the use of replication-deficient adenoviral vectors encoding multiple epitopes from HCMV have been used to expand specific T cells that recognize virally encoded antigens expressed at different stages of infection (e.g., early, IE, and late) (217,288) (Fig. 7).…”

Delineating the role of CD4+ T cells in the activation of human cytomegalovirus-specific immune responses following immunization with Ad-gBCMVpoly vaccine: implications for vaccination of immunocompromised individuals

“…The construction of the recombinant Ad5F35-based adenovirus has been described in our previous work (Rist et al, 2005). This vector expresses the CMV gB sequence from the alanine residue at position 31 to valine at position 700 with deletion of the signal sequence, and 46 contiguous HLA class I-and class II-restricted T-cell epitopes as a fusion protein (AdgBCMVpoly).…”

“…Ad-gBCMVpoly is a novel chimeric vaccine based on a replication-deficient adenovirus that encodes a truncated form of CMV-encoded gB antigen and multiple CMV Tcell epitopes from eight different CMV antigens, restricted through multiple human leukocyte antigen (HLA) class I and class II alleles, as a single fusion protein (Rist et al, 2005). Our most recent studies have demonstrated that immunization of an immunocompetent host with this chimeric vaccine consistently generated a pluripotent CMV antigen-specific cellular and antibody response, which provided protection against viral infection .…”

The immunological burden of human cytomegalovirus infection

“…Research has shifted to development of subunit vaccines that contain the most important antigens and induce responses that will be protective in vivo. This can be designed to target specific T cell epitopes by using recombinant viruses containing minimal CMV epitopes linked together, such as the poly-epitope-based recombinant adenovirus vaccine [72]. This constitutes over 30 different immunogenic peptides derived from eight CMV antigens, restricted by 16 HLA types covering >90% of the population.…”