Mycobacterial Purified Protein Derivatives Stimulate Innate Immunity: Malawians Show Enhanced Tumor Necrosis Factor Alpha, Interleukin-1β (IL-1β), and IL-10 Responses Compared to Those of Adolescents in the United Kingdom

Abstract

To investigate the role of innate immunity in variable efficacy of Mycobacterium bovis BCG vaccination in Malawi and the United Kingdom, we examined 24-h tumor necrosis factor alpha, interleukin-1␤ (IL-1␤), and IL-10 responses to mycobacterial purified protein derivatives (PPDs). The rank order in stimulatory potency for different PPDs was the same for all three cytokines. Before vaccination Malawians made higher pro-and anti-inflammatory responses than did United Kingdom subjects. Fewer than 5% of United Kingdom subjects made IL-10 in response to any PPD, compared to 19 to 57% responders among Malawians. Priming for regulatory IL-10 may contribute to the smaller increase in gamma interferon responses in Malawians compared to United Kingdom subjects following BCG vaccination.The efficacy of vaccination against tuberculosis with Mycobacterium bovis bacillus Calmette-Guérin (BCG) varies geographically (reviewed in reference 10), one reason for which relates to differences in exposure to environmental mycobacteria (3). This is reflected in (i) higher prevaccination gamma interferon (IFN-␥) responses to environmental mycobacterial antigens in Malawi than in the United Kingdom (5), (ii) greater BCG-attributable increases in IFN-␥ responses in the United Kingdom than in Malawi (5), and (iii) greater BCGattributable increases in IFN-␥ response to M. tuberculosis purified protein derivative (PPD) in Malawians with low initial responsiveness to PPDs of M. avium, M. intracellulare, and M. scrofulaceum (the MAIS complex) than in those with high initial responses (3). The higher prevalence of IFN-␥ responsiveness to PPDs of the environmental MAIS complex than to PPDs of M. tuberculosis, M. bovis, or the more distantly related fast-growing species M. vaccae and M. fortuitum in Malawi (3) might relate to both relative exposure to these different species and the composition of cross-reacting T-cell peptide epitopes in the preparations. Alternatively, or in addition, they could reflect the ability of PPDs to induce proinflammatory (e.g., tumor necrosis factor alpha [TNF-␣] and interleukin-1␤ [IL-1␤]) or anti-inflammatory (e.g., IL-10) cytokine responses that regulate the adaptive immune response. To address this, we here examine 24-h TNF-␣, IL-1␤, and IL-10 responses in stimulated whole-blood cultures. This reveals differences in the magnitude of responsiveness to different mycobacterial PPDs as well as apparent in vivo priming for higher prevaccination responses in Malawian than in United Kingdom subjects.Study design. Recruitment and study design are described in detail elsewhere (4,5,23). In Malawi 633 young adults were recruited: of 562 eligible for BCG vaccination, 378 received BCG vaccine and 184 were given placebo. One year later, 329 of 378 vaccinees and 154 of 184 from the placebo group were retested for cytokine responses. In the United Kingdom (5, 23), 424 children were recruited: of those eligible for BCG vaccination, 282 received BCG vaccine and 115 controls received no injection. One year later 246 of 282 vaccinee...

Neutrophil-mediated innate immune resistance to mycobacteria

“…Interestingly, we did not observe statistically significant ethnic variation in BCG-lux assay luminescence ratios in this study. The antigen-stimulated whole blood of black Africans living in Malawi has previously been shown to secrete higher levels of TNF and IFN-γ than that of white individuals living in the United Kingdom (30,31), and we also found that BCG-stimulated TNF and IFN-γ secretion was higher for black African participants than for south Asian and white participants. These are 2 of the best-characterized cytokines necessary for protection against TB (32), and it may be that the more pronounced BCG-stimulated TNF and IFN-γ responses we observed in whole blood of black Africans represent compensatory mechanisms to restrict mycobacterial luminescence when neutrophil numbers are low.…”

Correlates of Immune Protection from Tuberculosis

“…Black et al found that the magnitude of the IFN-γ response was greater in BCG vaccinated UK teenagers when compared to BCG vaccinated teenagers in Malawi [41]. Weir et al later showed that innate immune responses to PPD prior to BCG vaccination in teenagers from Malawi were greater than those in the UK [39]. The stronger innate Two studies with culture filtrate protein (CFP) and one study with live M.tb used long-term culture (cells cultured for >5 days) to assess immune responses.…”

“…Control populations in these studies also vary, being sometimes defined as mycobacterially naïve (PPD negative) or PPD positive or latently infected or non-TB infected respiratory patients. Stimulation with PPD has been used in several studies to assess immune responses [37][38][39][40][41]. Black et al found that the magnitude of the IFN-γ response was greater in BCG vaccinated UK teenagers when compared to BCG vaccinated teenagers in Malawi [41].…”

Exogenous Re-infection by Multiple Exposures to Mycobacterium tuberculosis Contributes to Subsequent Development of Active Tuberculosis

“…Mantoux negative individuals can receive up to 4-5 BCG vaccinations in their lifetime even though multiple BGC vaccination has been associated with development of Th2 dominated responses [42][43][44][45][46][47] . In high TB burdened Malawi, environmental mycobacteria and subsequent BCG vaccination results in proinflammatory TNF-and IL-1 and anti-inflammatory IL-10 production [48] . Endemic TB countries have increased parisitic/helminth infections, may contribute to the induction of Th2 responses [49] .…”