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 3

Rh108-deficient RhCMV/SIV induces SIV-specific T cell responses at high dose in the absence of vector shedding in urine.

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Rh108-deficient RhCMV/SIV induces SIV-specific T cell responses at high ...
(A) Two RhCMV-seropositive RMs were sequentially inoculated with increasing doses of 68-1 RhCMV/FKBP-Rh108/SIVrtni until the onset of detectable SIV-specific CD4+ and CD8+ T cell responses in peripheral blood, as measured by intracellular cytokine staining (ICS) for IFN-γ and TNF-α using pools of 15 mer peptides overlapping by 11 amino acids (AA) corresponding to SIV Rev, Tat, and Nef (without Int) (10). The frequency of IFN-γ+and/or TNF-α+ memory T cells is shown for each of the indicated postinoculation time points. (B) Three additional RhCMV-seropositive RMs were inoculated with 1 × 107 PFU of the same vector with longitudinal SIV Rev/Tat/Nef–specific T cell responses determined as described in A (left panels). Urine was collected from these 3 RMs at the indicated time points and, after concentration, cocultured with rhesus fibroblasts in the presence of Shield-1 for 42 days. Cells were then lysed and analyzed by immunoblot for the presence of the SIV Rev/Tat/Nef/Int fusion protein using antibodies to the V5 epitope tag (Thermo Fisher Scientific) as described (23). The 68-1 RhCMV/SIVrtni lysates were used as positive controls. SIV Rev/Tat/Nef–specific T cell responses were also measured longitudinally in BAL fluid for RMs 1–5 (Supplemental Figure 3).