The Effect of a BSA Conjugate of a Synthetic Hexasaccharide Related to the Fragment of Capsular Polysaccharide of Streptococcus pneumoniae Type 14 on the Activation of Innate and Adaptive Immune Responses.

Nelli K Akhmatova,Elvin A Akhmatov,Yury E Tsvetkov,Dmitry V Yashunsky,Marina L Gening,Ekaterina A Kurbatova,Nadezhda B Egorova,Elena V Sukhova,Nikolay E Nifantiev,Denis Yu Logunov

doi:10.3389/fimmu.2016.00248

Abstract

We report the effect of a bovine serum albumin (BSA) conjugate of a synthetic hexasaccharide (HS) related to the fragment of the capsular polysaccharide (PS) of Streptococcus pneumoniae type 14 on the stimulation of innate immune system and the subsequent development of a PS-specific antibody response. Glycoconjugate (GC) in the presence (GC + AL) or absence of aluminum hydroxide was administered to mice twice. GC increased the number of TLR2-expressing cells and induced the maturation of dendritic cells (CD11c+, CD80+ and, MHCII+), which secreted IL-1β, IL-6, and TNFα into the culture medium. The level of IL-1β, IL-10, IFNγ, and TNFα in the blood increased within 24 h after the single GC administration to mice. On day 7, the numbers of splenic CD4+ and CD8+ T lymphocytes and B lymphocytes increased. After the second immunization, the levels of CD4+ and CD8+ T lymphocytes were lower than in the control, whereas the B cell, NK cell, and MHC class II-expressing cell numbers remained enhanced. However, of the presence of anti-PS, IgG antibodies were not detected. The addition of aluminum hydroxide to GC stimulated the production of GM-CSF, IL-1β, IL-5, IL-6, IL-10, IL-17, IFNγ, and TNFα. Anti-PS IgG1 antibody titers 7 days after the second immunization were high. During that period, normal levels of splenic CD4+ T lymphocytes were maintained, whereas reduced CD8+ T lymphocyte numbers and increased levels of B lymphocytes, NK cells, and MHC class II-expressing cell numbers were observed. Anti-PS IgG levels diminished until day 92. A booster immunization with GC + AL stimulated the production of anti-PS IgG memory antibodies, which were determined within 97 days. The elucidation of specific features of the effect of the synthetic HS conjugate on the stimulation of innate, cell-mediated immunity, and antibody response can favor the optimization of GC vaccine design.

Highlights

Streptococcus pneumoniae is one of the major etiological factors of bacterial pneumonia, bacteremia, meningitis, otitis media, and other serious pneumococcal childhood and adult diseases [1,2,3,4,5] and has a high death rate [6,7,8]
Hexasaccharide enhanced secreted embryonic alkaline phosphatase (SEAP) activity compared to the negative control (p = 0.049535), GC (20 μg based on HS), and bovine serum albumin (BSA) (Figure 2A)
LPS, CBLB 502, and C12-iE-DAP, which are ligands for TLR4, TLR5, and NOD1, respectively, and served as positive control for evaluation of THP1-XBlue-CD14 NF-kB reporter cells activation, increased SEAP activity when used at a concentration that was 100 times lower (1 μg/mL)

Summary

Introduction

Streptococcus pneumoniae is one of the major etiological factors of bacterial pneumonia, bacteremia, meningitis, otitis media, and other serious pneumococcal childhood and adult diseases [1,2,3,4,5] and has a high death rate [6,7,8]. According to the chemical structure of the capsule, more than 90 serotypes of S. pneumoniae were identified [5, 9]. 20 serotypes of S. pneumoniae cause approximately 80% of diseases [7, 10, 11]. One of the mechanisms for the induction of the T-dependent IgG immune response to capsular PSs or oligosaccharides is their conjugation with a carrier protein [12, 16,17,18]. Some oligosaccharides that are conjugated with protein induce the formation of antibodies to capsular PSs at a higher level than that of traditional PS conjugate vaccines [19]

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Discussion

Conclusion