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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 single dose vaccines (subunits MVA85A and Ad85A, and BCG) on an id BCG challenge.(a) BALB/c mice were immunized id with 1×106 pfu MVA85A or 2×109 vp Ad85A. Control mice (Naïve) received no immunization. Four weeks later all mice were challenged id with 1×105 CFU BCG, contralaterally to the site of vaccination. Ears and LNs were harvested 4 weeks after BCG challenge and processed for CFU quantification. (*P<0.05, n = 10 except naïves, n = 5). (b) Corresponding intracellular cytokine staining (ICS) of the local draining LNs. Red bars represent the proportion of IFN-γ-secreting CD4+ T cells in response to 85A, blue bars represent the same for CD8+ T cells (M, n = 4; Naïve, n = 3; Ad, n = 4. *P<0.05). (c) Effect of BCG vaccine compared to subunit MVA85A on an id BCG challenge. BALB/c mice were immunized id with either 1×106 pfu MVA85A or 2.2×104 cfu BCG. “Naïve” and antibiotic-treated (I+R) mice received no immunization. Four weeks later all mice were challenged with 6×103 CFU BCG, except the BCG control group who received no challenge. In the I+R group, challenge was followed by 4 weeks treatment with isoniazid and rifampicin. Ears and LNs were harvested 4 weeks after BCG challenge and processed for CFU quantification. Log10 BCG CFU individual data points for each mouse are shown. Bars represent the median per group. (c) Ears (**P<0.01, “non-significant, ND”, n = 10); (d) LNs (**P<0.01, “non-significant, ND”, n = 10).
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pone-0019840-g003: Effect of single dose vaccines (subunits MVA85A and Ad85A, and BCG) on an id BCG challenge.(a) BALB/c mice were immunized id with 1×106 pfu MVA85A or 2×109 vp Ad85A. Control mice (Naïve) received no immunization. Four weeks later all mice were challenged id with 1×105 CFU BCG, contralaterally to the site of vaccination. Ears and LNs were harvested 4 weeks after BCG challenge and processed for CFU quantification. (*P<0.05, n = 10 except naïves, n = 5). (b) Corresponding intracellular cytokine staining (ICS) of the local draining LNs. Red bars represent the proportion of IFN-γ-secreting CD4+ T cells in response to 85A, blue bars represent the same for CD8+ T cells (M, n = 4; Naïve, n = 3; Ad, n = 4. *P<0.05). (c) Effect of BCG vaccine compared to subunit MVA85A on an id BCG challenge. BALB/c mice were immunized id with either 1×106 pfu MVA85A or 2.2×104 cfu BCG. “Naïve” and antibiotic-treated (I+R) mice received no immunization. Four weeks later all mice were challenged with 6×103 CFU BCG, except the BCG control group who received no challenge. In the I+R group, challenge was followed by 4 weeks treatment with isoniazid and rifampicin. Ears and LNs were harvested 4 weeks after BCG challenge and processed for CFU quantification. Log10 BCG CFU individual data points for each mouse are shown. Bars represent the median per group. (c) Ears (**P<0.01, “non-significant, ND”, n = 10); (d) LNs (**P<0.01, “non-significant, ND”, n = 10).

Mentions: Mice were immunized id with a viral vectored candidate TB vaccine (MVA85A-Modified vaccina virus Ankara expressing mycobacterial antigen 85A [16]-or Ad85A-recombinant E1/E3-deleted adenovirus human serotype 5, AdHu5, expressing antigen 85A [17]), and then challenged four weeks later with BCG. The amount of BCG in the ears of mice four weeks after BCG challenge was then quantified (Fig. 3a). There was a trend for a reduction in CFU counts between naïve animals and those vaccinated with MVA85A and Ad85A, but this did not reach statistical significance (P = 0.11 and P = 0.16, respectively). Intracellular cytokine staining (ICS) of the local draining LNs showed that the CD8+ T cell response to antigen 85A (% of IFN-γ-secreting CD8+ T cells) was higher for the Ad85A group than MVA85A or naïve groups (Ad85A vs naïve, P = 0.02; Ad85A vs MVA85A, P = 0.035). The 85A-specific CD4+ T cell responses were similar across both MVA85A/Ad85A groups (Fig. 3b). There was a strong positive correlation between the lymph node ICS and spleen ELISpot responses to 85A (R = 0.86, P = 0.01, Spearman, data not shown). However, there was no correlation between these LN/spleen ex-vivo responses and BCG CFU measured in the ear post challenge (data not shown).


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 single dose vaccines (subunits MVA85A and Ad85A, and BCG) on an id BCG challenge.(a) BALB/c mice were immunized id with 1×106 pfu MVA85A or 2×109 vp Ad85A. Control mice (Naïve) received no immunization. Four weeks later all mice were challenged id with 1×105 CFU BCG, contralaterally to the site of vaccination. Ears and LNs were harvested 4 weeks after BCG challenge and processed for CFU quantification. (*P<0.05, n = 10 except naïves, n = 5). (b) Corresponding intracellular cytokine staining (ICS) of the local draining LNs. Red bars represent the proportion of IFN-γ-secreting CD4+ T cells in response to 85A, blue bars represent the same for CD8+ T cells (M, n = 4; Naïve, n = 3; Ad, n = 4. *P<0.05). (c) Effect of BCG vaccine compared to subunit MVA85A on an id BCG challenge. BALB/c mice were immunized id with either 1×106 pfu MVA85A or 2.2×104 cfu BCG. “Naïve” and antibiotic-treated (I+R) mice received no immunization. Four weeks later all mice were challenged with 6×103 CFU BCG, except the BCG control group who received no challenge. In the I+R group, challenge was followed by 4 weeks treatment with isoniazid and rifampicin. Ears and LNs were harvested 4 weeks after BCG challenge and processed for CFU quantification. Log10 BCG CFU individual data points for each mouse are shown. Bars represent the median per group. (c) Ears (**P<0.01, “non-significant, ND”, n = 10); (d) LNs (**P<0.01, “non-significant, ND”, n = 10).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3101220&req=5

pone-0019840-g003: Effect of single dose vaccines (subunits MVA85A and Ad85A, and BCG) on an id BCG challenge.(a) BALB/c mice were immunized id with 1×106 pfu MVA85A or 2×109 vp Ad85A. Control mice (Naïve) received no immunization. Four weeks later all mice were challenged id with 1×105 CFU BCG, contralaterally to the site of vaccination. Ears and LNs were harvested 4 weeks after BCG challenge and processed for CFU quantification. (*P<0.05, n = 10 except naïves, n = 5). (b) Corresponding intracellular cytokine staining (ICS) of the local draining LNs. Red bars represent the proportion of IFN-γ-secreting CD4+ T cells in response to 85A, blue bars represent the same for CD8+ T cells (M, n = 4; Naïve, n = 3; Ad, n = 4. *P<0.05). (c) Effect of BCG vaccine compared to subunit MVA85A on an id BCG challenge. BALB/c mice were immunized id with either 1×106 pfu MVA85A or 2.2×104 cfu BCG. “Naïve” and antibiotic-treated (I+R) mice received no immunization. Four weeks later all mice were challenged with 6×103 CFU BCG, except the BCG control group who received no challenge. In the I+R group, challenge was followed by 4 weeks treatment with isoniazid and rifampicin. Ears and LNs were harvested 4 weeks after BCG challenge and processed for CFU quantification. Log10 BCG CFU individual data points for each mouse are shown. Bars represent the median per group. (c) Ears (**P<0.01, “non-significant, ND”, n = 10); (d) LNs (**P<0.01, “non-significant, ND”, n = 10).
Mentions: Mice were immunized id with a viral vectored candidate TB vaccine (MVA85A-Modified vaccina virus Ankara expressing mycobacterial antigen 85A [16]-or Ad85A-recombinant E1/E3-deleted adenovirus human serotype 5, AdHu5, expressing antigen 85A [17]), and then challenged four weeks later with BCG. The amount of BCG in the ears of mice four weeks after BCG challenge was then quantified (Fig. 3a). There was a trend for a reduction in CFU counts between naïve animals and those vaccinated with MVA85A and Ad85A, but this did not reach statistical significance (P = 0.11 and P = 0.16, respectively). Intracellular cytokine staining (ICS) of the local draining LNs showed that the CD8+ T cell response to antigen 85A (% of IFN-γ-secreting CD8+ T cells) was higher for the Ad85A group than MVA85A or naïve groups (Ad85A vs naïve, P = 0.02; Ad85A vs MVA85A, P = 0.035). The 85A-specific CD4+ T cell responses were similar across both MVA85A/Ad85A groups (Fig. 3b). There was a strong positive correlation between the lymph node ICS and spleen ELISpot responses to 85A (R = 0.86, P = 0.01, Spearman, data not shown). However, there was no correlation between these LN/spleen ex-vivo responses and BCG CFU measured in the ear post challenge (data not shown).

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