Science Bite (3 minute oral presentation with PPT in live session and poster) - Students and ECRs only Lorne Infection and Immunity 2023

Otitis-Prone children have reduced Haemophilus influenzae protein D-specific memory B-cells compared to non-otitis-prone children but no reduction in overall T follicular helper cell proportions. (#51)

Sharon L Clark 1 2 , Elke Seppanen 2 , Christian Tjiam 2 3 , Lauren Bakaletz 4 , Allan Cripps 5 , Harvey Coates 1 2 , Shyan Vijayasekaran 1 6 , Peter Richmond 1 2 7 , Ruth Thornton 2 3
  1. School of Medicine, The University of Western Australia, Perth, WA, Australia
  2. Wesfarmers Centre of Vaccines & Infectious Disease, Telethon Kids Institute, Perth, WA, Australia
  3. Centre for Child Health Research, The University of Western Australia, Perth, WA, Australia
  4. Centre for Microbial Pathogenesis, Abigail Wexner Research Institute at Nationwide Children’s Hospital & the Ohio State University College of Medicine, Columbus, Ohio, USA
  5. School of Medicine & Menzies Health Institute, Griffith University, Gold Coast, Queensland, Australia
  6. Otolaryngology Head and Neck Surgery , Perth Children's Hospital, Perth, Western Australia, Australia
  7. Departments of Immunology and General Paediatrics, Perth Children's Hospital, Perth, Western Australia, Australia

Chronic and recurrent middle ear infections (otitis media-OM) are predominantly caused by persistence of nontypeable Haemophilus influenzae (NTHi) biofilms and often result in children undergoing surgery. These children are considered otitis-prone and, in Australia, are more likely to be Aboriginal. Previously we have shown that Aboriginal otitis-prone children have reduced serum IgG titres specific for NTHi adhesin/biofilm antigens, Protein D (PD), rsPilA and ChimV4, compared to non-Aboriginal otitis-prone and non-otitis-prone children, which could contribute to OM susceptibility. We aimed to determine whether lower NTHi specific IgG levels were related to frequencies of global and/or antigen-specific B-cells and circulating follicular helper T (cTfh) cells.

Peripheral blood mononuclear cells (PBMC) from Aboriginal otitis-prone (n=15), non-Aboriginal otitis-prone (n=15) and non-otitis-prone (n=15) children were assessed using memory B cell ELISpot for numbers of spot forming cells against PD, rsPilA, ChimV4 and OMP26 (per 2x105 PBMCS), following 5-day stimulation with R-848 and IL-2. Proportions of circulating sub-populations of B-cells (CD3-CD19+CD27±IgD±) and cTfh (Tfh; CD4+CD45RA-CCR7+CXCR5+PD-1+ICOS±) were assessed using flow cytometry. Group comparisons were made using Kruskal–Wallis tests.

Aboriginal and non-Aboriginal otitis-prone children had lower PD-specific memory B-cell numbers (median=29 vs 18, respectively) compared to non-otitis-prone children (median=67;P<0.006) and a trend towards lower memory B-cell numbers for rsPilA and ChimV4 (medians: Aboriginal otitis-prone =6.5, 8.5; non-Aboriginal otitis-prone=19, 27; non-otitis-prone=31.5, 36.5;P=0.099; P=0.078, respectively). No differences were observed between groups for OMP26-specific memory B-cells (median=164.9-182.5). Overall proportions of switched-memory (IgD-CD27+; median=8.03%-12.06%), unswitched-memory (IgD+CD27+; median=4.88%-7.47%) and naïve (IgD+CD27-; median=71.52%-78.54%) B-cells were not different between groups. Aboriginal (ICOS+=0.15%, ICOS-=0.1%) and non-Aboriginal otitis-prone children (ICOS+=0.16%, ICOS-=0.08%) had higher proportions of cTfh cells compared to non-otitis-prone children (ICOS+=0.05%, ICOS-=0.04%;P<0.047).

Otitis-prone children had lower numbers of NTHi adhesin/biofilm antigen-specific memory B-cells, consistent with previously observed differences in IgG titres. Proportions of circulating B-cell and cTfh cell populations were similar across groups. Further investigation is needed to examine proportions of antigen specific cTfh cells or perturbation in alternate pathways. Better understanding of drivers for the development of long-lived memory B-cells to NTHi antigens is needed for the rational design the antigenic composition of NTHi vaccines most likely able to prevent chronic otitis media.