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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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Timescale showing BCG persistence in the ears and LNs of id-injected mice up to 12 weeks post immunization.Log BCG CFU in the ears (estimated by culture) are shown for (a) the high dose group (7000 CFU id); and (b) the low dose group (60 CFU id). Log BCG CFU in the auricular LNs are shown in (c) the high dose group (7000 CFU id); and (d) the mid dose group (60 CFU id). Datasets include individual data points for each mouse; the bars represent the median per group in (a) and (b), and a line connects the means for each group in (c) and (d). * indicates P<0.05. Both ears and LNs were homogenized and plated onto 7H11 Middlebrook agar. Log BCG CFU in the ears estimated by culture (e) and BCG genome copies/mHPRT copies estimated by PCR (f) are shown in a timescale for the high dose group, up to 12 weeks post BCG immunization. Quantitative PCR was performed with BCG-specific primers. Individual data points are shown for each mouse with a line connecting the means for each group.
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pone-0019840-g001: Timescale showing BCG persistence in the ears and LNs of id-injected mice up to 12 weeks post immunization.Log BCG CFU in the ears (estimated by culture) are shown for (a) the high dose group (7000 CFU id); and (b) the low dose group (60 CFU id). Log BCG CFU in the auricular LNs are shown in (c) the high dose group (7000 CFU id); and (d) the mid dose group (60 CFU id). Datasets include individual data points for each mouse; the bars represent the median per group in (a) and (b), and a line connects the means for each group in (c) and (d). * indicates P<0.05. Both ears and LNs were homogenized and plated onto 7H11 Middlebrook agar. Log BCG CFU in the ears estimated by culture (e) and BCG genome copies/mHPRT copies estimated by PCR (f) are shown in a timescale for the high dose group, up to 12 weeks post BCG immunization. Quantitative PCR was performed with BCG-specific primers. Individual data points are shown for each mouse with a line connecting the means for each group.

Mentions: A time-course experiment, measuring out to 12 weeks post vaccination, described the replication kinetics of BCG in the ears, local draining (auricular) LNs and spleen following id BCG immunization. Three different doses of BCG were used: 7000, 60 and 1 CFU. The culture data for the high dose (7000 CFU) and mid dose (60 CFU) groups are shown (Fig. 1a and 1b). Live BCG CFU persisted for 4 weeks, after which there was a significant decline in CFU counts (P = 0.04). Animals vaccinated with the mid dose (60 CFU) showed significantly diminished levels of BCG throughout the time-course, the levels falling to almost zero after week 4. No CFU were detected at any time-point in animals vaccinated with just 1 CFU of BCG (data not shown). The PCR data are shown for ear CFU in the high dose group (Fig. 1f) and show a comparable kinetic to culture (1e), with a significant reduction in CFU between day 0 and week 6 (P = 0.03) and again between weeks 6 and 8 (P = 0.009). There was a strong positive correlation between the levels of BCG estimated by the two quantification methods across both high and mid doses (R = 0.77, P<0.0001, Spearman).


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)

Timescale showing BCG persistence in the ears and LNs of id-injected mice up to 12 weeks post immunization.Log BCG CFU in the ears (estimated by culture) are shown for (a) the high dose group (7000 CFU id); and (b) the low dose group (60 CFU id). Log BCG CFU in the auricular LNs are shown in (c) the high dose group (7000 CFU id); and (d) the mid dose group (60 CFU id). Datasets include individual data points for each mouse; the bars represent the median per group in (a) and (b), and a line connects the means for each group in (c) and (d). * indicates P<0.05. Both ears and LNs were homogenized and plated onto 7H11 Middlebrook agar. Log BCG CFU in the ears estimated by culture (e) and BCG genome copies/mHPRT copies estimated by PCR (f) are shown in a timescale for the high dose group, up to 12 weeks post BCG immunization. Quantitative PCR was performed with BCG-specific primers. Individual data points are shown for each mouse with a line connecting the means for each group.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3101220&req=5

pone-0019840-g001: Timescale showing BCG persistence in the ears and LNs of id-injected mice up to 12 weeks post immunization.Log BCG CFU in the ears (estimated by culture) are shown for (a) the high dose group (7000 CFU id); and (b) the low dose group (60 CFU id). Log BCG CFU in the auricular LNs are shown in (c) the high dose group (7000 CFU id); and (d) the mid dose group (60 CFU id). Datasets include individual data points for each mouse; the bars represent the median per group in (a) and (b), and a line connects the means for each group in (c) and (d). * indicates P<0.05. Both ears and LNs were homogenized and plated onto 7H11 Middlebrook agar. Log BCG CFU in the ears estimated by culture (e) and BCG genome copies/mHPRT copies estimated by PCR (f) are shown in a timescale for the high dose group, up to 12 weeks post BCG immunization. Quantitative PCR was performed with BCG-specific primers. Individual data points are shown for each mouse with a line connecting the means for each group.
Mentions: A time-course experiment, measuring out to 12 weeks post vaccination, described the replication kinetics of BCG in the ears, local draining (auricular) LNs and spleen following id BCG immunization. Three different doses of BCG were used: 7000, 60 and 1 CFU. The culture data for the high dose (7000 CFU) and mid dose (60 CFU) groups are shown (Fig. 1a and 1b). Live BCG CFU persisted for 4 weeks, after which there was a significant decline in CFU counts (P = 0.04). Animals vaccinated with the mid dose (60 CFU) showed significantly diminished levels of BCG throughout the time-course, the levels falling to almost zero after week 4. No CFU were detected at any time-point in animals vaccinated with just 1 CFU of BCG (data not shown). The PCR data are shown for ear CFU in the high dose group (Fig. 1f) and show a comparable kinetic to culture (1e), with a significant reduction in CFU between day 0 and week 6 (P = 0.03) and again between weeks 6 and 8 (P = 0.009). There was a strong positive correlation between the levels of BCG estimated by the two quantification methods across both high and mid doses (R = 0.77, P<0.0001, Spearman).

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