Late gene expression–deficient cytomegalovirus vectors elicit conventional T cells that do not protect against SIV
Scott G. Hansen, Jennie L. Womack, Wilma Perez, Kimberli A. Schmidt, Emily Marshall, Ravi F. Iyer, Hillary Cleveland Rubeor, Claire E. Otero, Husam Taher, Nathan H. Vande Burgt, Richard Barfield, Kurt T. Randall, David Morrow, Colette M. Hughes, Andrea N. Selseth, Roxanne M. Gilbride, Julia C. Ford, Patrizia Caposio, Alice F. Tarantal, Cliburn Chan, Daniel Malouli, Peter A. Barry, Sallie R. Permar, Louis J. Picker, Klaus Früh
Scott G. Hansen, Jennie L. Womack, Wilma Perez, Kimberli A. Schmidt, Emily Marshall, Ravi F. Iyer, Hillary Cleveland Rubeor, Claire E. Otero, Husam Taher, Nathan H. Vande Burgt, Richard Barfield, Kurt T. Randall, David Morrow, Colette M. Hughes, Andrea N. Selseth, Roxanne M. Gilbride, Julia C. Ford, Patrizia Caposio, Alice F. Tarantal, Cliburn Chan, Daniel Malouli, Peter A. Barry, Sallie R. Permar, Louis J. Picker, Klaus Früh
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Research Article AIDS/HIV Virology

Late gene expression–deficient cytomegalovirus vectors elicit conventional T cells that do not protect against SIV

Abstract

Rhesus cytomegalovirus–based (RhCMV-based) vaccine vectors induce immune responses that protect ~60% of rhesus macaques (RMs) from SIVmac239 challenge. This efficacy depends on induction of effector memory–based (EM-biased) CD8+ T cells recognizing SIV peptides presented by major histocompatibility complex-E (MHC-E) instead of MHC-Ia. The phenotype, durability, and efficacy of RhCMV/SIV-elicited cellular immune responses were maintained when vector spread was severely reduced by deleting the antihost intrinsic immunity factor phosphoprotein 71 (pp71). Here, we examined the impact of an even more stringent attenuation strategy on vector-induced immune protection against SIV. Fusion of the FK506-binding protein (FKBP) degradation domain to Rh108, the orthologue of the essential human CMV (HCMV) late gene transcription factor UL79, generated RhCMV/SIV vectors that conditionally replicate only when the FK506 analog Shield-1 is present. Despite lacking in vivo dissemination and reduced innate and B cell responses to vaccination, Rh108-deficient 68-1 RhCMV/SIV vectors elicited high-frequency, durable, EM-biased, SIV-specific T cell responses in RhCMV-seropositive RMs at doses of ≥ 1 × 106 PFU. Strikingly, elicited CD8+ T cells exclusively targeted MHC-Ia–restricted epitopes and failed to protect against SIVmac239 challenge. Thus, Rh108-dependent late gene expression is required for both induction of MHC-E–restricted T cells and protection against SIV.

Authors

Scott G. Hansen, Jennie L. Womack, Wilma Perez, Kimberli A. Schmidt, Emily Marshall, Ravi F. Iyer, Hillary Cleveland Rubeor, Claire E. Otero, Husam Taher, Nathan H. Vande Burgt, Richard Barfield, Kurt T. Randall, David Morrow, Colette M. Hughes, Andrea N. Selseth, Roxanne M. Gilbride, Julia C. Ford, Patrizia Caposio, Alice F. Tarantal, Cliburn Chan, Daniel Malouli, Peter A. Barry, Sallie R. Permar, Louis J. Picker, Klaus Früh

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Figure 4

SIV-specific CD8+ T cells elicited by Rh108-deficient 68-1 RhCMV/SIVgag are similar in magnitude and functional phenotype to 68-1 RhCMV/SIVgag but differ in MHC restriction.

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SIV-specific CD8+ T cells elicited by Rh108-deficient 68-1 RhCMV/SIVgag ...
(A) Mean (±SEM) CD8+ T cell frequencies as determined by ICS to overlapping (by 11 amino acids) SIV Gag 15mer peptides. Differences were NS between the 2 groups (Wilcoxon Rank Sum test of the AUC for each RM). (B) Box plots compare the memory differentiation phenotype of CD8+ T cells in blood during plateau phase (>60 weeks). Memory differentiation state (percentage of each subset within the total response) based on CD28 and CCR7 delineates central memory (TCM), transitional effector-memory (TTrEM), and effector-memory (TEM). Wilcoxon Rank Sum test was used to compare Gag-specific T cells within each subset (P > 0.05 for all comparisons). (C) Box plots compare blood CD8+ memory T cell frequencies responding to Gag 15mer peptides with TNF-α, IFN-γ, IL-2, and MIP-1β production, alone and in all combinations. Results were grouped according to the number of cytokines secreted. Wilcoxon Rank Sum test with multiple testing correction was used to compare Gag-specific T cells expressing 1, 2, 3, or 4 cytokines (P > 0.05 for all comparisons). (D) Plateau phase of blood CD8+ T cell responses to individual MHC-E– and MHC-II–restricted Gag supertopes (19). Box plots in B–D show jittered points and a box from first to third quartiles and a line at the median, with whiskers extending to the farthest data point within 1.5× IQR above and below the box. (E) Plateau phase blood CD8+ T cells from RMs inoculated with 68-1 RhCMV/FKBP-Rh108/SIVgag were assessed by ICS for each of 125 consecutive Gag peptides. Responses > 0.05% (after background subtraction) are indicated by a box. Colors reflect MHC restriction based on response inhibition with MHC-E blocking peptide, MHC-II blocking mAb, and/or pan-MHC-I blocking mAb.