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Preclinical development of an in vivo BCG challenge model for testing candidate TB vaccine efficacy.

Minassian AM, Ronan EO, Poyntz H, Hill AV, McShane H - PLoS ONE (2011)

Bottom Line: Culture and quantitative PCR methods have been developed to quantify BCG in the skin, using the mouse ear as a surrogate for human skin.Candidate TB vaccines have been evaluated for their ability to protect against a BCG skin challenge, using this model, and the results indicate that protection against a BCG skin challenge is predictive of BCG vaccine efficacy against aerosol M.tb challenge.Translation of these findings to a human BCG challenge model could enable more rapid assessment and down selection of candidate TB vaccines and ultimately the identification of an immune correlate of protection.

View Article: PubMed Central - PubMed

Affiliation: The Jenner Institute, University of Oxford, Oxford, United Kingdom. minassian.angela@gmail.com

ABSTRACT
There is an urgent need for an immunological correlate of protection against tuberculosis (TB) with which to evaluate candidate TB vaccines in clinical trials. Development of a human challenge model of Mycobacterium tuberculosis (M.tb) could facilitate the detection of such correlate(s). Here we propose a novel in vivo Bacille Calmette-Guérin (BCG) challenge model using BCG immunization as a surrogate for M.tb infection. Culture and quantitative PCR methods have been developed to quantify BCG in the skin, using the mouse ear as a surrogate for human skin. Candidate TB vaccines have been evaluated for their ability to protect against a BCG skin challenge, using this model, and the results indicate that protection against a BCG skin challenge is predictive of BCG vaccine efficacy against aerosol M.tb challenge. Translation of these findings to a human BCG challenge model could enable more rapid assessment and down selection of candidate TB vaccines and ultimately the identification of an immune correlate of protection.

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Effect of BCG, BCG-MVA85A (B–M), and BCG-Ad85A (B-Ad) prime-boost regimes on an id BCG challenge.Timeline shown in (a): BALB/c mice were immunized with 104 CFU BCG id and then boosted after 13 weeks with either 1×106 pfu MVA85A id or 2×109 vp Ad85A id. All animals were challenged 4 weeks later with 6×103 CFU of BCG id. Organs were harvested 4 weeks after challenge. Log10 BCG CFU of challenge are shown in (c) Ears (***P<0.001, **P<0.01, n = 8); and (d) LNs (***P<0.001, **P<0.01, n = 8, “NS” = no significant difference). **/*** indicate significance of immunization regimes over naïve mice. (b) Pre-challenge immunogenicity as measured in the blood by ELISpot. IFN-γ responses were assessed after stimulation with PPD, a H-2d CD4+ T cell epitope, and a H-2d CD8+ T cell epitope present in the M.tb antigen 85A, on blood samples taken one day pre- BCG challenge. IFN-γ responses within all three vaccinated groups (BCG (B), BCG-MVA85A (B-M), and BCG-Ad85A, (B-Ad), n = 10) are shown. Whiskers represent minimum to maximum values, boxes the interquartile range, and bars the median values for each group. Correlations between LN cfu and pre-challenge blood ELISpot responses to (e) PPD; (f) CD4+ epitope; and (g) CD8+ epitope. Spearman correlation analysis (with individual data-points for all 30 mice in the three vaccination groups) is shown.
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pone-0019840-g006: Effect of BCG, BCG-MVA85A (B–M), and BCG-Ad85A (B-Ad) prime-boost regimes on an id BCG challenge.Timeline shown in (a): BALB/c mice were immunized with 104 CFU BCG id and then boosted after 13 weeks with either 1×106 pfu MVA85A id or 2×109 vp Ad85A id. All animals were challenged 4 weeks later with 6×103 CFU of BCG id. Organs were harvested 4 weeks after challenge. Log10 BCG CFU of challenge are shown in (c) Ears (***P<0.001, **P<0.01, n = 8); and (d) LNs (***P<0.001, **P<0.01, n = 8, “NS” = no significant difference). **/*** indicate significance of immunization regimes over naïve mice. (b) Pre-challenge immunogenicity as measured in the blood by ELISpot. IFN-γ responses were assessed after stimulation with PPD, a H-2d CD4+ T cell epitope, and a H-2d CD8+ T cell epitope present in the M.tb antigen 85A, on blood samples taken one day pre- BCG challenge. IFN-γ responses within all three vaccinated groups (BCG (B), BCG-MVA85A (B-M), and BCG-Ad85A, (B-Ad), n = 10) are shown. Whiskers represent minimum to maximum values, boxes the interquartile range, and bars the median values for each group. Correlations between LN cfu and pre-challenge blood ELISpot responses to (e) PPD; (f) CD4+ epitope; and (g) CD8+ epitope. Spearman correlation analysis (with individual data-points for all 30 mice in the three vaccination groups) is shown.

Mentions: The hypothesis that the protective effect of BCG could be boosted by a candidate subunit vaccine was subsequently tested using this challenge model. The effect of prime-boost regimes BCGid-MVA85Aid (B–M) and BCGid-Ad85Aid (B-Ad) on BCG challenge, in comparison to BCG alone (BCG), is shown in Fig. 6. All three regimes achieved comparable reduction in BCG CFU counts in the skin and LNs. (Fig. 6c: Ear CFU: BCG, (P = 0.0004), B–M, (P = 0.0014) and B-Ad, (P = 0.0008); LN CFU: BCG, (P = 0.001), B–M, (P = 0.0008, P = 0.001).


Preclinical development of an in vivo BCG challenge model for testing candidate TB vaccine efficacy.

Minassian AM, Ronan EO, Poyntz H, Hill AV, McShane H - PLoS ONE (2011)

Effect of BCG, BCG-MVA85A (B–M), and BCG-Ad85A (B-Ad) prime-boost regimes on an id BCG challenge.Timeline shown in (a): BALB/c mice were immunized with 104 CFU BCG id and then boosted after 13 weeks with either 1×106 pfu MVA85A id or 2×109 vp Ad85A id. All animals were challenged 4 weeks later with 6×103 CFU of BCG id. Organs were harvested 4 weeks after challenge. Log10 BCG CFU of challenge are shown in (c) Ears (***P<0.001, **P<0.01, n = 8); and (d) LNs (***P<0.001, **P<0.01, n = 8, “NS” = no significant difference). **/*** indicate significance of immunization regimes over naïve mice. (b) Pre-challenge immunogenicity as measured in the blood by ELISpot. IFN-γ responses were assessed after stimulation with PPD, a H-2d CD4+ T cell epitope, and a H-2d CD8+ T cell epitope present in the M.tb antigen 85A, on blood samples taken one day pre- BCG challenge. IFN-γ responses within all three vaccinated groups (BCG (B), BCG-MVA85A (B-M), and BCG-Ad85A, (B-Ad), n = 10) are shown. Whiskers represent minimum to maximum values, boxes the interquartile range, and bars the median values for each group. Correlations between LN cfu and pre-challenge blood ELISpot responses to (e) PPD; (f) CD4+ epitope; and (g) CD8+ epitope. Spearman correlation analysis (with individual data-points for all 30 mice in the three vaccination groups) is shown.
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pone-0019840-g006: Effect of BCG, BCG-MVA85A (B–M), and BCG-Ad85A (B-Ad) prime-boost regimes on an id BCG challenge.Timeline shown in (a): BALB/c mice were immunized with 104 CFU BCG id and then boosted after 13 weeks with either 1×106 pfu MVA85A id or 2×109 vp Ad85A id. All animals were challenged 4 weeks later with 6×103 CFU of BCG id. Organs were harvested 4 weeks after challenge. Log10 BCG CFU of challenge are shown in (c) Ears (***P<0.001, **P<0.01, n = 8); and (d) LNs (***P<0.001, **P<0.01, n = 8, “NS” = no significant difference). **/*** indicate significance of immunization regimes over naïve mice. (b) Pre-challenge immunogenicity as measured in the blood by ELISpot. IFN-γ responses were assessed after stimulation with PPD, a H-2d CD4+ T cell epitope, and a H-2d CD8+ T cell epitope present in the M.tb antigen 85A, on blood samples taken one day pre- BCG challenge. IFN-γ responses within all three vaccinated groups (BCG (B), BCG-MVA85A (B-M), and BCG-Ad85A, (B-Ad), n = 10) are shown. Whiskers represent minimum to maximum values, boxes the interquartile range, and bars the median values for each group. Correlations between LN cfu and pre-challenge blood ELISpot responses to (e) PPD; (f) CD4+ epitope; and (g) CD8+ epitope. Spearman correlation analysis (with individual data-points for all 30 mice in the three vaccination groups) is shown.
Mentions: The hypothesis that the protective effect of BCG could be boosted by a candidate subunit vaccine was subsequently tested using this challenge model. The effect of prime-boost regimes BCGid-MVA85Aid (B–M) and BCGid-Ad85Aid (B-Ad) on BCG challenge, in comparison to BCG alone (BCG), is shown in Fig. 6. All three regimes achieved comparable reduction in BCG CFU counts in the skin and LNs. (Fig. 6c: Ear CFU: BCG, (P = 0.0004), B–M, (P = 0.0014) and B-Ad, (P = 0.0008); LN CFU: BCG, (P = 0.001), B–M, (P = 0.0008, P = 0.001).

Bottom Line: Culture and quantitative PCR methods have been developed to quantify BCG in the skin, using the mouse ear as a surrogate for human skin.Candidate TB vaccines have been evaluated for their ability to protect against a BCG skin challenge, using this model, and the results indicate that protection against a BCG skin challenge is predictive of BCG vaccine efficacy against aerosol M.tb challenge.Translation of these findings to a human BCG challenge model could enable more rapid assessment and down selection of candidate TB vaccines and ultimately the identification of an immune correlate of protection.

View Article: PubMed Central - PubMed

Affiliation: The Jenner Institute, University of Oxford, Oxford, United Kingdom. minassian.angela@gmail.com

ABSTRACT
There is an urgent need for an immunological correlate of protection against tuberculosis (TB) with which to evaluate candidate TB vaccines in clinical trials. Development of a human challenge model of Mycobacterium tuberculosis (M.tb) could facilitate the detection of such correlate(s). Here we propose a novel in vivo Bacille Calmette-Guérin (BCG) challenge model using BCG immunization as a surrogate for M.tb infection. Culture and quantitative PCR methods have been developed to quantify BCG in the skin, using the mouse ear as a surrogate for human skin. Candidate TB vaccines have been evaluated for their ability to protect against a BCG skin challenge, using this model, and the results indicate that protection against a BCG skin challenge is predictive of BCG vaccine efficacy against aerosol M.tb challenge. Translation of these findings to a human BCG challenge model could enable more rapid assessment and down selection of candidate TB vaccines and ultimately the identification of an immune correlate of protection.

Show MeSH
Related in: MedlinePlus