Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Jul 3;14(7):1820-1831.
doi: 10.1080/21645515.2018.1448328. Epub 2018 Apr 12.

Therapeutic conserved elements (CE) DNA vaccine induces strong T-cell responses against highly conserved viral sequences during simian-human immunodeficiency virus infection

Paul Munson  1   2 , Yi Liu  1 , Debra Bratt  2 , James T Fuller  1 , Xintao Hu  3 , George N Pavlakis  4 , Barbara K Felber  3 , James I Mullins  1   5   6   7 , Deborah Heydenburg Fuller  1   2
Affiliations

Therapeutic conserved elements (CE) DNA vaccine induces strong T-cell responses against highly conserved viral sequences during simian-human immunodeficiency virus infection

Paul Munson et al. Hum Vaccin Immunother. .

Abstract

HIV-specific T-cell responses play a key role in controlling HIV infection, and therapeutic vaccines for HIV that aim to improve viral control will likely need to improve on the T-cell responses induced by infection. However, in the setting of chronic infection, an effective therapeutic vaccine must overcome the enormous viral genetic diversity and the presence of pre-existing T-cell responses that are biased toward immunodominant T-cell epitopes that can readily mutate to evade host immunity and thus potentially provide inferior protection. To address these issues, we investigated a novel, epidermally administered DNA vaccine expressing SIV capsid (p27Gag) homologues of highly conserved elements (CE) of the HIV proteome in macaques experiencing chronic but controlled SHIV infection. We assessed the ability to boost or induce de novo T-cell responses against the conserved but immunologically subdominant CE epitopes. Two groups of animals were immunized with either the CE DNA vaccine or a full-length SIV p57gag DNA vaccine. Prior to vaccination, CE responses were similar in both groups. The full-length p57gag DNA vaccine, which contains the CE, increased overall Gag-specific responses but did not increase CE responses in any animals (0/4). In contrast, the CE DNA vaccine increased CE responses in all (4/4) vaccinated macaques. In SIV infected but unvaccinated macaques, those that developed stronger CE-specific responses during acute infection exhibited lower viral loads. We conclude that CE DNA vaccination can re-direct the immunodominance hierarchy towards CE in the setting of attenuated chronic infection and that induction of these responses by therapeutic vaccination may improve immune control of HIV.

Keywords: DNA vaccines; HIV; SHIV; SIV; conserved elements vaccine; gag; therapeutic vaccination.

PubMed Disclaimer

Figures

Figure 1.
Figure 1.
DNA vaccines and vaccine study design. (A) DNA vaccines. The CE DNA vaccine consists of two plasmids encoding seven different conserved sequences connected by optimized linker sequences. CE2, CE3, CE4, and CE5 differ by toggled amino acids analogous to the an HIV p24CE vaccine previously described (see Methods). The FL DNA vaccine expresses the p57 gag coding sequence from p57Gag from SIV17E-Fr. A genetic adjuvant plasmid expressing the heat-labile E. coli enterotoxin (LT) was co-delivered with both DNA vaccines (CE and FL) at each dose. (B) Comparison of p27Gag CE in HIV and SIV strains, adapted from Hu et al. SIV p27Gag sequences from SIVmac (macaque origin) and SIVsmm (sooty mangabey), were compared to reported HIV Gag p24 CE sequences. The SIV p27CE1 and p27CE2 toggled amino acids are indicated in red. Blue amino acids indicate SIV sequences that are dissimilar from HIV sequences. (C) The number of CE amino acids (AA) that are common in both SIV and the HIV-1 M group (see panel B), including toggle AA, for each CE is shown along with percent match between the HIV-1 p24CE and the SIV homologues. (D) Study Design. Macaques were stratified into either the CE (conserved elements) or FL (full length) DNA vaccine groups based on plasma viral load, MHC class I genotype, prior vaccination, and sex. The CE + LT DNA vaccinated animals (blue) received three doses of the CE + LT DNA vaccine administered into the epidermis of the skin by PMED at weeks 0, 4, and 8 followed by a single boost of the FL + LT DNA vaccine at week 12. The FL DNA vaccinated animals (red) received four doses of the FL SIV Gag DNA vaccine at weeks 0, 4, 8 and 12.
Figure 2.
Figure 2.
CE-specific IFN-γ T-cell responses in the blood. T-cell responses in Spot Forming Cells (SFC) per on million PBMC were measured before and after vaccination by IFN-γ ELISpot following stimulation with SIV CE or p57 Gag peptide pools. Shown are the mean spot forming cells (SFC) per 106 PBMC corresponding to (A) Gag-specific and (B) CE-specific SFC measured at baseline (week 0) and 2 weeks after the final DNA vaccine dose (week 14) in the CE group (left panels) and FL group (middle panels). (C) The specificities of the CE-specific responses in each animal in the CE group (left panel) and the FL group (right panel) at week 14 were measured against each separate CE peptide pool. (D) Shown are the breadth of CE-specific responses (number of positive CE peptide pools) at week 14 (left panel) and the change of the CE breadth at week 14 versus week 0 (right panel). (E) Analysis of the correlation between the magnitude of Gag-specific SFC prior to vaccination (Week 0) versus the increase in CE breadth post-vaccination (Week 14) was determined by Spearman Rank correlation test. Median values are indicated. P-values were determined by non-parametric Mann-Whitney T tests. P values ≤ 0.05 were considered significant.
Figure 3.
Figure 3.
CE-specific IFN-γ T-cell responses in tissues. (A) The total magnitude of Gag-specific IFN-γ T-cell responses as Spot Forming Cells (SFC) were determined by IFN-γ ELISpot at Week 14 following stimulation with pools of Gag peptides at Week 14 in the axillary (left panel) and mesenteric (right panel) lymph nodes (LN). (B) CE-specific T-cell responses are shown as cumulative number of SFC against each CE peptide pool and was determined by summing the responses against each individual CE (1-7) peptide pool in the axillary (left panel) and mesenteric (middle panel) lymph nodes and the jejunum (right panel). (C) The breadth of CE-specific IFN-γ T-cell responses was determined by measuring spot forming cells (SFC) against each individual CE peptide pool in the axillary (left panel) and mesenteric (right panel) lymph nodes. The dotted line at seven indicates the maximum number of CE that can be recognized. (D) The specificity of the CE responses was mapped in the axillary (left two panels) and mesenteric (right two panels) lymph nodes by ELISpot at week 14. Shown are responses against each peptide pool in animals immunized with either the CE or FL DNA vaccines. Median values are indicated in panels A-C with red horizontal lines and p-values were determined by non-parametric Mann-Whitney T test. P values ≤ 0.05 were considered significant.
Figure 4.
Figure 4.
Multifunctional and cytolytic CE-specific CD8+ T-cell responses. The frequency of CE-specific CD8+ T-cells expressing the cytokines IFN-γ, IL-2, and/or TNF-⍺ and/or CD107a, a marker of cytolytic effector function, was determined two weeks after the final DNA vaccine dose (week 14) using cryopreserved PBMC stimulated overnight with CE peptide pools. (A-D) Shown are the frequencies of CE-specific CD8+ T-cells expressing the indicated cytokine or cytolytic functions. (E) The relative proportion of CE-specific CD8+ T-cells that are expressing the cytolytic degranulation marker, CD107a. The difference in mean response between the two groups was analyzed by a non-parametric Mann-Whitney T test. Median values are indicated with black horizontal lines and a p-value ≤ 0.05 was considered significant.
Figure 5.
Figure 5.
Plasma viral RNA load in SHIV infected macaques. Plasma viral RNA levels before and after vaccination were determined by a nucleic acid sequence-based amplification technique (NASBA) with a limit of detection of 50 copies per 1 mL of plasma.
Figure 6.
Figure 6.
Higher CE-specific T-cells responses correlate with lower viral set point during acute SIV infection. CE-specific T-cell responses in rhesus macaques acutely infected with SIVΔB670 were measured six weeks following intravenous infection using (A) IFN-γ ELISpot against individual CE peptides and (B) IFN-γ ICS against a pool of all seven CE peptides. CE responders were defined as having a detectable CE response measured by ELISpot and/or ICS. (C) Viral loads were measured in the plasma by quantitative RT-PCR. (D) Mean viral set point was determined by averaging the viral loads measured at weeks 4, 5, and 6 and compared between CE responders (animals with detectable CE responses) and CE non-responders (animals with undetectable CE responses) by non-parametric Mann-Whitney T test. Horizontal lines indicate median values. Correlation between the breadth of (E) CE and (F) Gag-specific T-cell responses and mean set point plasma viral load was determined by a Spearman Rank correlation. A p value ≤ 0.05 was considered significant.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Schackman BR, Fleishman JA, Su AE, Berkowitz BK, Moore RD, Walensky RP, Becker JE, Voss C, Paltiel AD, Weinstein MC, et al. The Lifetime Medical Cost Savings from Preventing HIV in the United States. Med Care. 2015;53:293-301. PMID:25710311. - PMC - PubMed
    1. Brenchley JM, Price DA, Schacker TW, Asher TE, Silvestri G, Rao S, Kazzaz Z, Bornstein E, Lambotte O, Altmann D, et al. Microbial translocation is a cause of systemic immune activation in chronic HIV infection. Nat Med. 2006;12:1365-71. doi:10.1038/nm1511. PMID:17115046. - DOI - PubMed
    1. Gupta RK, Jordan MR, Sultan BJ, Hill A, Davis DH, Gregson J, Sawyer AW, Hamers RL, Ndembi N, Pillay D, et al Global trends in antiretroviral resistance in treatment-naive individuals with HIV after rollout of antiretroviral treatment in resource-limited settings: a global collaborative study and meta-regression analysis. The Lancet. 2012;380:1250-8. doi:10.1016/S0140-6736(12)61038-1. - DOI - PMC - PubMed
    1. Chun TW, Carruth L, Finzi D, Shen X, DiGiuseppe JA, Taylor H, Hermankova M, Chadwick K, Margolick J, Quinn TC, et al. Quantification of latent tissue reservoirs and total body viral load in HIV-1 infection. Nature. 1997;387:183-8. doi:10.1038/387183a0. PMID:9144289. - DOI - PubMed
    1. Butler KM, Gavin P, Coughlan S, Rochford A, Donagh SM, Cunningham O, Poulsom H, Watters S, Klein N. Rapid Viral Rebound after 4 Years of Suppressive Therapy in a Seronegative HIV-1 Infected Infant Treated from Birth. Pediatr Infect Dis J. 2014; PMID:25144802. - PubMed

Publication types

MeSH terms

LinkOut - more resources