Elsevier

Vaccine

Volume 33, Issue 17, 21 April 2015, Pages 2056-2065
Vaccine

Variation of growth in the production of the BCG vaccine and the association with the immune response. An observational study within a randomised trial

https://doi.org/10.1016/j.vaccine.2015.02.056Get rights and content

Highlights

Abstract

Introduction

Bacille Calmette–Guérin (BCG) vaccine has beneficial non-specific effects on overall survival. After BCG vaccination, positive PPD response and scar formation are associated with increased survival. During a trial randomising low-birth-weight neonates to BCG at birth or the usual delayed BCG, the manufacturer of the BCG vaccine experienced a period with relatively slow growth rate of the BCG. We investigated the association between growth rate of BCG when manufacturing the vaccine and its capability to induce immune responses in vivo and in vitro.

Methods

1633 neonates were randomised to BCG at birth and examined for scar at 12 months; a subgroup was tested for PPD response at 2 and 6 months. The BCG batches from the Slow growth period were compared with the precedent and subsequent Normal growth batches with regard to prevalence and size of BCG scar and PPD response. We also tested the effect of batches on in vitro cytokine responses.

Results

At 12 months, the Slow growth batches were associated with higher BCG scar prevalence (98.2%) than the precedent batches (92.3%, p = 0.01) but the prevalence remained high after return to normal growth (98.8%, p = 0.52). The Slow growth batches were associated with larger scar size (5.0 mm) than precedent (4.4 mm, p < 0.01) and subsequent batches (4.8 mm, p = 0.03). Compared with Normal growth batches, the Slow growth batches were associated with a higher prevalence of positive PPD responses, and among PPD positive children, a larger PPD reaction (geometric mean ratio: 1.40 (1.20–1.63)) at 2 months. In response to secondary heterologous stimulation, monocytes primed with Slow growth batches induced higher IL-6 (p = 0.03) and TNF-α responses (p = 0.03) compared with Normal growth batches.

Conclusion

The study indicates that variations in the production of BCG vaccine may influence important immunological effects of the vaccine.

Trial registration

clinicaltrials.gov (NCT00625482).

Section snippets

Background

The Bacille Calmette–Guérin (BCG) vaccine against tuberculosis is given to millions of children every year [1]. Observational and randomised-controlled trials (RCT) suggest that BCG reduces mortality more than can be explained by prevention of tuberculosis [2], [3], [4], [5], [6], [7], [8], [9], [10], [11]. These effects are called non-specific effects (NSE) of BCG. In a recent review commissioned by WHO, the effect were estimated to halve the mortality risk, and this effect was not likely to

Setting

The BHP maintains a Health and Demographic Surveillance System (HDSS) in suburban Bissau, the capital of Guinea-Bissau. Furthermore, BHP follows a cohort of LBW children from the entire area of Bissau and suburbs. All newborn children weighing <2500 g at discharge from the maternity ward of the main national public hospital and two private hospitals are invited to participate in the cohort. In addition, children weighing <2500 g born at home are invited when presenting for their first vaccination

Results

Among the 1633 children randomised to early BCG, two children were excluded due to major malformations discovered after randomisation and 24 had no information on BCG batch number (Fig. 1). Due to the later inclusion of males, there were significantly more males among children vaccinated with the Slow growth and the Normal growth after batches, contributing to a higher inclusion weight in these two groups. Otherwise there were no differences among the three groups (Table 2).

Discussion

We report that growth rate of BCG bacteria during the production was associated with differences in scar development and PPD responses. The Slow growth batches were associated with more and larger scars, and a higher frequency and magnitude of the in vivo responses to PPD. Moreover, we found indications that the Slow growth batches induced higher cytokine responses in monocytes.

Author contributions

KRH, SHA, CSB, SBS conceived the study. PA, CSB conceived and designed the BCG trial. SBS and IM supervised the field data collection. SHA supervised the data collection on BCG growth. SBS and KJJ analysed the data. AA supervised the data analysis. BB performed the in vitro experiments. MGN supervised the in vitro experiments. SBS and KJJ wrote the first draft of the manuscript. All contributed to the final version of the manuscript.

Funding

This work was supported by The Novo Nordisk Foundation and The European Research Council. KJJ was supported by a grant from University of Southern Denmark and by a Female Research Leader grant [grant number 09-066317] from the Danish Council of Independent Research to CSB. PA holds a research professorship grant from the Novo Nordisk Foundation. CSB was funded by an ERC Starting Grant [grant number ERC-2009-StG-243149] that also funds SBS. MGN was supported by a Vici grant of the Netherlands

Conflict of interest

SHA and KRH are employed by SSI, the producer of the SSI BCG vaccine used in the present study. The salaries of SBS, KJJ, AA, IM, PA and CSB are administered, but not financed by SSI. BB and MGN declare no conflict of interest.

Acknowledgements

We thank the staff of SSI's Pharmacovigilance Unit for supplying information and advice on adverse reactions to BCG Danish SSI.

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