Long-Term Central and Effector SHIV-Specific Memory T Cell Responses Elicited after a Single Immunization with a Novel Lentivector DNA Vaccine

Chebloune Y (2014) Long-Term Central and Effector SHIV-Specific Memory T Cell Responses Elicited after a Single Immunization with a Novel Lentivector DNA Vaccine. PLoS ONE 9(10): e110883. doi:10.1371/journal.pone.0110883 Long-Term Central and Effector SHIV-Specific Memory T Cell Responses Elicited after a Single Immunization with a Novel Lentivector DNA Vaccine Ge raldine Arrode-Bruse s 0 Maha Moussa 0 Monique Baccard-Longere 0 Franc ois Villinger 0 Yahia Chebloune 0 J. Gerardo Garcia-Lerma, Centers for Disease Control and Prevention, United States of America 0 1 INRA, ANRS, Universite Joseph Fourier, PAVAL Lab./Nanobio 2, UJF Grenoble, Grenoble, France, 2 Institut de Biologie et Pathologie, Centre Hospitalo-Universitaire de Grenoble, Grenoble, France, 3 Division of Pathology, Yerkes National Primate Research Center, Emory University , Atlanta, Georgia , United States of America Prevention of HIV acquisition and replication requires long lasting and effective immunity. Given the state of HIV vaccine development, innovative vectors and immunization strategies are urgently needed to generate safe and efficacious HIV vaccines. Here, we developed a novel lentivirus-based DNA vector that does not integrate in the host genome and undergoes a single-cycle of replication. Viral proteins are constitutively expressed under the control of Tat-independent LTR promoter from goat lentivirus. We immunized six macaques once only with CAL-SHIV-IN2 DNA using combined intramuscular and intradermal injections plus electroporation. Antigen-specific T cell responses were monitored for 47 weeks post-immunization (PI). PBMCs were assessed directly ex vivo or after 6 and 12 days of in vitro culture using antigenic and/or homeostatic proliferation. IFN-c ELISPOT was used to measure immediate cytokine secretion from antigen specific effector cells and from memory precursors with high proliferative capacity (PHPC). The memory phenotype and functions (proliferation, cytokine expression, lytic content) of specific T cells were tested using multiparametric FACS-based assays. All immunized macaques developed lasting peripheral CD8+ and CD4+ T cell responses mainly against Gag and Nef antigens. During the primary expansion phase, immediate effector cells as well as increasing numbers of proliferating cells with limited effector functions were detected which expressed markers of effector (EM) and central (CM) memory phenotypes. These responses contracted but then reemerged later in absence of antigen boost. Strong PHPC responses comprising vaccine-specific CM and EM T cells that readily expanded and acquired immediate effector functions were detected at 40/47 weeks PI. Altogether, our study demonstrated that a single immunization with a replication-limited DNA vaccine elicited persistent vaccine-specific CM and EM CD8+ and CD4+ T cells with immediate and readily inducible effector functions, in the absence of ongoing antigen expression. - Data Availability: The authors confirm that all data underlying the findings are fully available without restriction. All relevant data are within the paper and its Supporting Information files. Funding: The work was supported by grants from Agence Nationale de Recherche sur le SIDA (ANRS, RA0000640), Institut National de Recherche Agronomique (INRA, 2012-2013-YC-DC) and Universite Joseph Fourier (UJF, AGIR 13CSV13) to YC. GAB was financially supported by a postdoctoral fellowship from ANRS (2011022) and Marie Curie International Reintegration Grant (IRG) program from European Commission (Nu 276828- HIVNONILV, FP7-PEOPLE-2010-RG). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. More than three decades after the discovery of HIV, the development of a safe and efficacious vaccine that can induce protective immunity in humans against HIV/AIDS remains an unfulfilled priority. The classical vectors and strategies for vaccine development, efficient for acute infectious diseases, have failed to prevent acquisition and/or control of acquired HIV-1 infection. These results indicate that novel vectors/strategies need to be explored and developed to induce protective immunity against this type of persistent infection. One significant hurdle to this progress is the fact that correlates of protection are not fully elucidated [1]. Among naturally infected HIV-1 patients, few individuals such as Long-Term Non-progressors (LTNP), Elite suppressors (ES) and recently the Berlin patient have shown successful control of replication of their lentiviral infection [24]. However, in some of these patients, HIV-1 variants naturally attenuated by mutation in the nef gene (Live-attenuated) were isolated [58]. This observation provided a rationale for testing live-attenuated (LAV) SIV and SHIV vaccines in non-human primate (NHP) models. LAV especially those with the least attenuated design, remain the only vaccines found to be able to achieve reproducible protection in macaques challenged with highly pathogenic viruses [912]. One salient safety issue associated with these vaccines, is the fact that they cause a persistent infection associated with integration of the provirus into the genome of the host, leading to potential mutations and gain of virulence especially in infants and in some adult macaques [1316]. Nevertheless, the protective responses afforded by LAV warrant additional investigation into mechanisms of protection [17] and similar approaches with hopefully better safety profiles, i.e. viral vectors that will mimic natural exposure to the virus but without integration into the genome and self-limited replication. Thus, genetic systems were developed to produce strains of SIV whose replications were limited to a singlecycle, leading to the production of virus proteins or virus like particles (VLPs). In particular, macaques repeatedly immunized with single-cycle SIV particles mounted potent virus specific T cell responses which did not prevent infection but significantly contained SIV replication after challenge [18,19], but to a lesser extent than persisting live-attenuated vaccine [17]. These results suggested that the ongoing stimulation of virus-specific immune responses might be essential to achieve long-term protection. The correlates of protection upon continuous antigen expression for the maintenance of vaccine-specific T cells associated with immediate antiviral effector functions have recently been highlighted in LAVmediated protection in an NHP study [17]. In addition, persistent and replication-competent recombinant viruses, such as cytomegalovirus vector expressing SIV antigens, provided complete protection in a subset of vaccinated monkeys, demonstrating that the continuous presence of vaccine-specific effector memory (EM) T cells can lead to complete control of SIV [20,21]. Interestingly, in a mouse mo (...truncated)