Immune Responses Following BCG Immunization of Infants in Uganda and United Kingdom Are Similar for Purified Protein Derivative but Differ for Secretory Proteins of Mycobacterium tuberculosis

Introduction: The immunogenicity of BCG vaccination in infants differs between populations. We hypothesized that prenatal exposure to mycobacterial antigens might explain the differences in immune responses to BCG seen in other studies of infants in Africa and the United Kingdom (UK) and we explored this in birth cohorts in Uganda and the UK. Materials and Methods: Blood samples were obtained from BCG-immunized infants of mothers with (n = 110) and without (n = 121) latent Mycobacterium tuberculosis infection (LTBI) in Uganda and BCG-immunized infants of mothers without LTBI (n = 25) in the UK at 10 and 52 weeks after birth. Cytokine and chemokine responses to PPD were measured to assess responses to BCG immunization, and to ESAT6/CFP10 to assess exposure to or infection with M. tuberculosis or non-tuberculous mycobacteria (NTM) in 6-day whole blood culture supernatants by a 17-plex Luminex assay. Median responses were compared between Ugandan infants (together, and separated by maternal LTBI status) and UK infants. Results: The IFN-γ response to BCG vaccination was similar between Ugandan and UK infants at 10 and 52 weeks. At week 52, TNF production was marginally higher in Ugandan infants, but after adjusting for multiple comparisons this difference was not significant. At weeks 10 and 52, stimulation of blood with ESAT6/CFP10 produced significantly higher IFN-γ, TNF, IL-12p40, IL-1α, IL-1β, IL-1Ra, IP-10, MIP-1α, MIP-1β, and GM-CSF in Ugandan compared to UK infants. Stimulation of blood with ESAT6/CFP10 produced significantly higher amounts of IL-8 (p = 0.0001), IL-10 (p = 0.0022), and IL-13 (p = 0.0020) in the UK than in Ugandan infants of mothers without LTBI at week 10, but not at week 52. Conclusions: Immune responses to mycobacterial antigens following BCG immunization are similar for PPD, but differ for ESAT6/CFP10, between infants in Uganda and the UK. Neither maternal LTBI nor infant exposure to or infection with mycobacteria impacts the response to BCG. The observed global differences in immune response to BCG immunization are likely to be due to other causes.UK Medical Research Council

Maternal Latent Mycobacterium tuberculosis Does Not Affect the Infant Immune Response Following BCG at Birth: An Observational Longitudinal Study in Uganda

Background: BCG has low efficacy in tropical countries. We hypothesized that maternal latent Mycobacterium tuberculosis (M.tb) infection (LTBI) results in fetal tolerance to mycobacterial antigens and impaired responses to BCG immunization. Methods: We enrolled 132 LTBI-positive and 150 LTBI-negative mothers and their babies in Entebbe, Uganda. Infants were BCG-immunized at birth. Cord blood and samples at weeks 1, 4, 6, 10, 14, 24, and 52 were analyzed for cytokine/chemokine responses to M.tb antigens by Luminex 17-plex assay in 6-day whole blood cultures and antibody responses by ELISA. Of the 17 Luminex analytes, seven (IL-2, IL-5, IL-10, IL-13, IL-17A, TNF, and IFN-γ) were included in the main analysis as they were considered most likely to represent T cell responses. Immune sensitization was defined as a detectable cord blood cytokine response to PPD for any of the seven cytokines. Patterns of cytokine and antibody responses were compared between infants of mothers with and without LTBI using linear mixed models adjusting for confounders. Results: Most infants (73%) were sensitized in utero to M.tb antigens, with no overall difference seen between infants born to mothers with or without LTBI. Patterns of post-BCG cytokine and antibody responses to mycobacterial antigens were similar between the two infant groups. Conclusions: Our data do not support the hypothesis that maternal LTBI results in an impaired response to BCG immunization, in Ugandan infants. BCG vaccination at or shortly after birth is likely to be beneficial to all infants, irrespective of maternal LTBI status.UK Medical Research Council; DELTAS Africa Initiative SSACAB; DELTAS Initiative MUIIplus; Commonwealth Scholarships Commission; MRC/UVRI and LSHTM Uganda Research Unit; EU Horizon 2020 programme; MRC London Intercollegiate Doctoral Training Partnership; MRC; UK Medical Research Council (MRC); UK Department for International Development (DFID)

Characterising the Coffee-Banana Agroforestry Systems: an Entry Point for Promoting Coffee and Banana Growing in mid-Northern Uganda

This study was conducted in the mid-Northern Ugandan districts of Nwoya, Gulu, Lira, Apach and Oyam to characterise the coffee-banana agroforestry systems. Thirty fields with coffee-banana agroforestry systems were selected and the level of field and crop management determined. Additionally, five coffee and banana plants were randomly selected and assessed for pests and diseases. All fields had Robusta coffee type whereas cooking bananas were the dominant clone (45%). Field management was limited. More than 80% of the fields had no bands, trenches or cover-crops. Most of the fields were lowly weeded (46.7%) and mulched (60%). Intercropping was low with 20% having maize or cassava. Similarly, most fields were lowly inter-planted with trees (40%) with only 28 tree/shrub species and dominated by fruit trees; namely oranges (70%), mangoes (63.3%) and pawpaw (56.7%) of the total number of tree species observed in the systems. Generally, 40% of coffee fields had not been de-suckered, pruned or changed cycle. However, at least 35% of the coffee fields were highly pruned and their cycle changed. For bananas, more than 70% of the fields were not de-suckered, propped or their corms removed, but 63% of them had been de-leafed and de-budded at a low to moderate level. Leaf skeletonisers and coffee leaf rust were the most observed pest (77.3%) and disease (15.3%) respectively. Pest damage was limited in bananas, though black Sigatoka was the commonest disease observed (56%). It is concluded that the region has embraced the systems but there is need for farmers to be provided with the right species of coffee, banana and trees.Keywords: Agroforestry-systems, cooking-bananas, Robusta-coffee