Cytokine response in cerebrospinal fluid of meningitis patients and outcome associated with pneumococcal serotype

Abstract

Streptococcus pneumoniae causes life-threatening meningitis. Its capsular polysaccharide determines the serotype and influences disease severity but the mechanism is largely unknown. Due to evidence of elevated cytokines levels in the meningeal inflammatory response, we measured 41 cytokines/chemokines and growth factors in cerebrospinal fluid (CSF) samples from 57 South African meningitis patients (collected in the period 2018–2019), with confirmed S. pneumoniae serotypes, using a multiplexed bead-based immunoassay. Based on multivariable Bayesian regression, using serotype 10A as a reference and after adjusting for HIV and age, we found IL-6 concentrations significantly lower in patients infected with serotypes 6D (undetectable) and 23A (1601 pg/ml), IL-8 concentrations significantly higher in those infected with 22A (40,459 pg/ml), 7F (32,400 pg/ml) and 15B/C (6845 pg/ml), and TNFα concentration significantly higher in those infected with serotype 18A (33,097 pg/ml). Although a relatively small number of clinical samples were available for this study and 28% of samples could not be assigned to a definitive serotype, our data suggests 15B/C worthy of monitoring during surveillance as it is associated with in-hospital case fatality and not included in the 13-valent polysaccharide conjugate vaccine, PCV13. Our data provides average CSF concentrations of a range of cytokines and growth factors for 18 different serotypes (14, 19F, 3, 6A, 7F, 19A, 8, 9N, 10A, 12F, 15B/C, 22F, 16F, 23A, 31, 18A, 6D, 22A) to serve as a basis for future studies investigating host–pathogen interaction during pneumococcal meningitis. We note that differences in induction of IL-8 between serotypes may be particularly worthy of future study.

Meningitis-associated pneumococcal serotype 8, ST 53, strain is hypervirulent in a rat model and has non-haemolytic pneumolysin which can be attenuated by liposomes

“…Serotype for all strains was confirmed by the Quellung reaction method (Statens Serum Institute, Copenhagen, Denmark) and whole genome sequencing. Additionally, the CSF of the patients infected with these isolates was collected as part of a larger study analyzing the severity of disease caused by different pneumococcal serotypes in the vaccine era (Müller et al, 2021). Therefore, basic patient data such as in-hospital outcome, status of human immunodeficiency virus (HIV) infection, age, and gender as well as the concentrations of the cytokines IL-6, IL-8, TNFa, IFN-g, IL-10, IL-1b in patient CSF were known.…”

“…A serotype 8 strain (58941) was chosen because it was found to be the most common serotype in IPD patients in South Africa in the vaccine era (Müller et al, 2022). The other two serotypes were chosen due to available CSF data and their association with mortality compared to serotype 8 (15B, strain 58331, significantly associated with higher mortality and serotype 14, strain 55927, associated with lower mortality) (Müller et al, 2021).…”

“…Cytokines in human CSF were measured using a 39-plex microsphere based multiplex assays (Human Custom ProcartaPlex 39-plex cat. number PPX-39-MX9HJM4 Thermo Fisher Scientific, Waltham, MA, USA) including IL-6, IL-8, TNFa, IFN-g, IL-10 and IL-1b as we have described previously (Müller et al, 2021). The assay was run according to the manufacturer's instructions.…”

“…Capsule thickness, differences in growth and possible associations of serotypes with inflammatory profile could all be reasons for differences in serotype related disease severity (Hathaway et al, 2012;Muller et al, 2020;Müller et al, 2021). Additionally, pneumococci also express pneumolysin (Ply), a cholesterol-dependent cytolysin, which triggers the host inflammatory response (Cockeran et al, 2002;Malley et al, 2003;Jefferies et al, 2007;Matthias et al, 2008;McNeela et al, 2010;Gonzaĺez-Juarbe et al, 2017;Subramanian et al, 2019;Hupp et al, 2022).…”

“…We chose three clinical isolates of different serotypes, isolated from South African meningitis patients. Serotype 8 was chosen, because it is the most common serotype in the vaccine era (Müller et al, 2022), serotype 15B because we previously found that it was associated with increased mortality, while serotype 14 was less frequently associated with mortality than the two other serotypes in our previous study (Müller et al, 2021). For these strains, clinical data and the patient CSF inflammatory profile was available.…”