Saporin-conjugated tetramers identify efficacious anti-HIV CD8+ T-cell specificities.

Ellen M Leitman,Paul Klenerman,Søren Buus,Marcus Altfeld,Christine D Palmer,Lynn Riddell,Asier Sáez-Cirión,Philip J R Goulder,Fabian Chen,Paul R Hess,Bruce D Walker,Stuart Sims,Philippa C Matthews

doi:10.1371/journal.pone.0184496

Abstract

Antigen-specific T-cells are highly variable, spanning potent antiviral efficacy and damaging auto-reactivity. In virus infections, identifying the most efficacious responses is critical to vaccine design. However, current methods depend on indirect measures or on ex vivo expanded CTL clones. We here describe a novel application of cytotoxic saporin-conjugated tetramers to kill antigen-specific T-cells without significant off-target effects. The relative efficacy of distinct antiviral CD8+ T-cell specificity can be directly assessed via antigen-specific CD8+ T-cell depletion. The utility of these reagents is demonstrated here in identifying the CD8+ T-cell specificity most effective in preventing HIV progression in HIV-infected HLA-B*27-positive immune controllers.

Highlights

The notion of selective T-cell depletion, most frequently aiming to purge autoreactivity, has recently gained substantial traction in the immunological field [1,2,3,4,5,6,7,8]
The development of fluorescently-labeled tetrameric peptide-MHC complexes allowed binding and visualisation of antigen-specific T-cells [9,10,11] and has led to the generation of modified tetramers that are coupled to a toxin, such as a ribosome inactivating protein saporin (SAP), that can selectively kill antigen-specific cells of interest
Target cells makes SAP-conjugated tetramers a powerful tool to eliminate auto-reactive T-cells causing disease and by which to identify antiviral T-cell specificities that are effective in preventing disease [4]

Summary

Introduction

The notion of selective T-cell depletion, most frequently aiming to purge autoreactivity, has recently gained substantial traction in the immunological field [1,2,3,4,5,6,7,8]. Being highly specific for their cognate T-cells and rapidly internalised upon engagement of the TCR, peptide-MHC tetramers can deliver any coupled moiety in a very selective manner [12]. An elegant proof-of-concept study in the mouse-LCMV model exploited the idea of SAPconjugated tetramers and demonstrated tetramer-mediated selective depletion of certain CD8 + T-cells in vitro and in vivo [4]. These cytotoxic tetramers were later used in vivo in further murine studies to delete diabetogenic T-cells [6], encephalopathogenic T-cells [5], minor histocompatibility HY-specific T-cells to prevent organ rejection [7], or to study ‘memory inflation’ [13]

Methods

Results

Conclusion