Abstract

Lentiviral Envelope (Env) antigenic variation and related immune evasion present major hurdles to effective vaccine development. Centralized Env immunogens that minimize the genetic distance between vaccine proteins and circulating viral isolates are an area of increasing study in HIV vaccinology. To date, the efficacy of centralized immunogens has not been evaluated in the context of an animal model that could provide both immunogenicity and protective efficacy data. We previously reported on a live-attenuated (attenuated) equine infectious anemia (EIAV) virus vaccine, which provides 100% protection from disease after virulent, homologous, virus challenge. Further, protective efficacy demonstrated a significant, inverse, linear relationship between EIAV Env divergence and protection from disease when vaccinates were challenged with viral strains of increasing Env divergence from the vaccine strain Env. Here, we sought to comprehensively examine the protective efficacy of centralized immunogens in our attenuated vaccine platform. We developed, constructed, and extensively tested a consensus Env, which in a virulent proviral backbone generated a fully replication-competent pathogenic virus, and compared this consensus Env to an ancestral Env in our attenuated proviral backbone. A polyvalent attenuated vaccine was established for comparison to the centralized vaccines. Additionally, an engineered quasispecies challenge model was created for rigorous assessment of protective efficacy. Twenty-four EIAV-naïve animals were vaccinated and challenged along with six-control animals six months post-second inoculation. Pre-challenge data indicated the consensus Env was more broadly immunogenic than the Env of the other attenuated vaccines. However, challenge data demonstrated a significant increase in protective efficacy of the polyvalent vaccine. These findings reveal, for the first time, a consensus Env immunogen that generated a fully-functional, replication-competent lentivirus, which when experimentally evaluated, demonstrated broader immunogenicity that does not equate to higher protective efficacy.

Document Type

Article

Publication Date

1-8-2015

Notes/Citation Information

Published in PLOS Pathogens, v. 11, no. 1, article e1004610, p. 1-14.

© 2015 Craigo et al.

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Digital Object Identifier (DOI)

http://dx.doi.org/10.1371/journal.ppat.1004610

Funding Information

This work was supported by NIH/NIAID (http://www.niaid.nih.gov) grant RO1 AI25850. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

S1_Fig.tif (637 kB)
S1 Fig. Day of challenge humoral immune responses in protected versus unprotected vaccinates.

journal.ppat.1004610.g001.png (323 kB)
Figure 1 (PNG). Phylogenetic analyses of the ConEnv, all consensus Envs, and the longitudinal isolates derived from experimental infection utilized in consensus gene development.

journal.ppat.1004610.g001.ppt (74 kB)
Figure 1 (PPT). Phylogenetic analyses of the ConEnv, all consensus Envs, and the longitudinal isolates derived from experimental infection utilized in consensus gene development.

journal.ppat.1004610.g001.TIF (776 kB)
Figure 1 (TIFF). Phylogenetic analyses of the ConEnv, all consensus Envs, and the longitudinal isolates derived from experimental infection utilized in consensus gene development.

journal.ppat.1004610.g002.png (382 kB)
Figure 2 (PNG). Comparison of deduced amino acid gp90 variable region sequences from EIAV variant Envs (used in attenuated and challenge strain construction) and ConEnv.

journal.ppat.1004610.g002.ppt (118 kB)
Figure 2 (PPT). Comparison of deduced amino acid gp90 variable region sequences from EIAV variant Envs (used in attenuated and challenge strain construction) and ConEnv.

journal.ppat.1004610.g002.TIF (733 kB)
Figure 2 (TIFF). Comparison of deduced amino acid gp90 variable region sequences from EIAV variant Envs (used in attenuated and challenge strain construction) and ConEnv.

journal.ppat.1004610.g003.png (728 kB)
Figure 3 (PNG). Clinical and virological profiles of ponies inoculated with the consensus Env in attenuated (ConD9) and pathogenic (EVCon) EIAV viral backbones.

journal.ppat.1004610.g003.ppt (168 kB)
Figure 3 (PPT). Clinical and virological profiles of ponies inoculated with the consensus Env in attenuated (ConD9) and pathogenic (EVCon) EIAV viral backbones.

journal.ppat.1004610.g003.TIF (1310 kB)
Figure 3 (TIFF). Clinical and virological profiles of ponies inoculated with the consensus Env in attenuated (ConD9) and pathogenic (EVCon) EIAV viral backbones.

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Figure 4 (PNG). Neutralization profiles of proviral variant strains with serum from animals experimentally infected with EV0, EV6, EV13, or EVCon.

journal.ppat.1004610.g004.ppt (71 kB)
Figure 4 (PPT). Neutralization profiles of proviral variant strains with serum from animals experimentally infected with EV0, EV6, EV13, or EVCon.

journal.ppat.1004610.g004.TIF (1007 kB)
Figure 4 (TIFF). Neutralization profiles of proviral variant strains with serum from animals experimentally infected with EV0, EV6, EV13, or EVCon.

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Figure 5 (PNG). Clinical and virological profiles of D9 vaccine trial group.

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Figure 5 (PPT). Clinical and virological profiles of D9 vaccine trial group.

journal.ppat.1004610.g005.TIF (1755 kB)
Figure 5 (TIFF). Clinical and virological profiles of D9 vaccine trial group.

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Figure 6 (PNG). Clinical and virological profiles of ConD9 vaccine trial group.

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Figure 6 (PPT). Clinical and virological profiles of ConD9 vaccine trial group.

journal.ppat.1004610.g006.TIF (1769 kB)
Figure 6 (TIFF). Clinical and virological profiles of ConD9 vaccine trial group.

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Figure 7 (PNG). Clinical and virological profiles of TriD9 vaccine trial group.

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Figure 7 (PPT). Clinical and virological profiles of TriD9 vaccine trial group.

journal.ppat.1004610.g007.TIF (1628 kB)
Figure 7 (TIFF). Clinical and virological profiles of TriD9 vaccine trial group.

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Figure 8 (PNG). Protection from disease is associated with complexity of immunogen.

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Figure 8 (PPT). Protection from disease is associated with complexity of immunogen.

journal.ppat.1004610.g008.TIF (576 kB)
Figure 8 (TIFF). Protection from disease is associated with complexity of immunogen.

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Table 1 (PNG). Characterization of vaccine Env-specific antibody prior to challenge.

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Table 1 (PPT). Characterization of vaccine Env-specific antibody prior to challenge.

journal.ppat.1004610.t001.TIF (193 kB)
Table 1 (TIFF). Characterization of vaccine Env-specific antibody prior to challenge.

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Table 2 (PNG). Characterization of vaccine immune responses prior to challenge.

journal.ppat.1004610.t002.ppt (41 kB)
Table 2 (PPT). Characterization of vaccine immune responses prior to challenge.

journal.ppat.1004610.t002.TIF (188 kB)
Table 2 (TIFF). Characterization of vaccine immune responses prior to challenge.

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