Abstract
This study characterized the immune responses in early Mycobacterium tuberculosis (Mtb) H37Ra infection of human peripheral blood mononuclear cell (PBMC)-collagen matrix culture and the impact of Bacille Calmette-Guérin (BCG) vaccination history of donor PBMCs on the immune responses to Mtb infection. Aggregates of PBMCs were initially observed on day 3 and the size of aggregates continued to increase on day 8 post-infection, where macrophages and T cell subsets were identified to be present. Similarly, mycobacterial load progressively increased in infected PBMCs during the 8 days of culture but were significantly lower in infected PBMCs from BCG vaccinated (BCG+) donors compared to unvaccinated (BCG-) donors. The levels of INF-γ, TNF-α, IL-4, IL-6, IL-10 and IL-17 in the supernatants of Mtb-infected PBMCs peaked at day 3 and decreased on days 5 and 8. The levels of these cytokines except IL-10 were significantly lower in Mtb-infected PBMCs from BCG+ donors compared to infected PBMCs from BCG- donors. The percentages of activated naïve Th cells, activated effector memory Th cells and activated central memory Tc cells were significantly higher in Mtb-infected PBMCs compared to uninfected PBMCs at day 8 post-infection. Further, the proportion of activated central memory Tc cells was significantly higher in infected PBMCs from BCG+ donors compared to the BCG- donors. This study highlights the possibility that BCG vaccination may confound results that utilize human PBMCs to study Mtb infection.
Highlights
Tuberculosis (TB) infection affects approximately one in three people in the world and causes approximately 1.5 million deaths worldwide each year [1]
Mycobacterium tuberculosis (Mtb) growth was the one infection outcome that was most stably confounded by peripheral blood mononuclear cell (PBMC) donor Bacille Calmette-Guerin (BCG) vaccination status at multiple time points over the 8 days infection period
Cytokine expression may be another infection outcome to assess for perturbation by PBMC donor BCG vaccination status; in our experiments, cytokine expression was generally more transient
Summary
Tuberculosis (TB) infection affects approximately one in three people in the world and causes approximately 1.5 million deaths worldwide each year [1]. BCG vaccination history and immune responses in PBMC model of M. tuberculosis infection. We used the three-dimensional in vitro granuloma model of Mtb infection and characterized the human immune response to attenuated Mtb H37Ra. use of attenuated strains in infection models may not mirror infection with wild-type virulent strains, use of attenuated strains allow us to assess the impact of potential confounders on experimental models using tools that are outside of a Biosafety Level 3 laboratory [24]. The second aim was to determine the impact of BCG vaccination history of PBMC donors on the immune and bacterial responses in three dimensional in vitro granuloma model of Mtb infection
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