Effect of lipoarabinomannan from Mycobacterium avium subsp avium in Freund's incomplete adjuvant on the immune response of cattle

Identification of immunogenic outer membrane proteins and evaluation of their protective efficacy against Stenotrophomonas maltophilia

Background

Stenotrophomonas maltophilia (S. maltophilia) is an emerging global multiple-drug-resistant organism. It becomes increasingly challenging to treat S. maltophilia infection effectively. Novel therapeutic and preventive approaches targeting S. maltophilia infection are still lacking. This study aims to isolate outer membrane proteins (Omps) from S. maltophilia and use immunoproteomic technology to identify potential vaccine candidates of Omps against S. maltophilia infections.

Methods

Omps from S. maltophilia culture were separated by two-dimensional electrophoresis and identified by matrix-assisted laser desorption/ionization time of flight mass spectrometry and nano liquid chromatography coupled fourier transform ion cyclotron resonance tandem mass spectrometry. Recombinant Omps were prepared and used to immunize mice, and the potency of mouse anti-Omp serum was tested in opsonophagocytic killing assay (OPKA). The effects of immunization with recombinant Omp on blood and tissue bacterial loads in a mouse model of S. maltophilia-induced infection were analyzed.

Results

Outer membrane protein A (OmpA) and Smlt4123 were identified by mass spectrometry. Mouse anti-Smlt4123 serum significantly reduced the bacterial counts in healthy individuals’ blood in OPKA (P < 0.05) but mouse anti-OmpA serum did not. Enzyme-linked immunosorbent assay revealed that the antibody subtype of mouse anti-Smlt4123 antibody was IgG1. Eight hours after an intraperitoneal challenge with S. maltophilia, the bacterial loads in mouse blood were significantly lower in the mice receiving immunization with recombinant Smlt4123 than in the control mice receiving no immunization (P < 0.05), whereas the bacterial loads in other organs, such as the liver, spleen, lung, and kidney were similar in the two groups.

Conclusions

The results revealed that the immunoproteomic approach was an efficient way to screen the immunogenic protein of Stenotrophomonas maltophilia. Moreover, the recombinant Smlt4123 had potential to protect mice from bacteremia caused by S. maltophilia in the early stages.

Electronic supplementary material

The online version of this article (10.1186/s12879-018-3258-7) contains supplementary material, which is available to authorized users.

Innate signaling by mycobacterial cell wall components and relevance for development of adjuvants for subunit vaccines

INTRODUCTION

Pathogen recognition receptors (PRRs) recognize pathogen-associated molecular patterns, triggering the induction of inflammatory innate responses and contributing to the development of specific adaptive immune responses. Novel adjuvants have been developed based on agonists of PRRs. Areas covered: Lipid pathogen-associated molecular patterns (PAMPs) present in the cell wall of mycobacteria are revised, with emphasis on agonists of C-type lectin receptors, signaling pathways, and preclinical data supporting their use as novel adjuvants inducing cell-mediated immune responses. Their potential use as lipid antigens in novel tuberculosis subunit vaccines is also discussed. Expert commentary: Few adjuvants are licensed for human use and mainly favour antibody-mediated protective immunity. Use of lipid PAMPs that trigger cell-mediated immune responses could lead to the development of adjuvants for vaccines against intracellular pathogens and cancer.

Sweeten PAMPs: Role of Sugar Complexed PAMPs in Innate Immunity and Vaccine Biology

Innate sensors play a critical role in the early innate immune responses to invading pathogens through sensing of diverse biochemical signatures also known as pathogen associated molecular patterns (PAMPs). These biochemical signatures primarily consist of a major family of biomolecules such as proteins, lipids, nitrogen bases, and sugar and its complexes, which are distinct from host molecules and exclusively expressed in pathogens and essential to their survival. The family of sensors known as pattern recognition receptors (PRRs) are germ-line encoded, evolutionarily conserved molecules, and consist of Toll-like receptors (TLRs), RIG-I-like receptors (RLRs), NOD-like receptors (NLRs), C-type lectin-like receptors (CLRs), and DNA sensors. Sensing of PAMP by PRR initiates the cascade of signaling leading to the activation of transcription factors, such as NF-κB and interferon regulatory factors (IRFs), resulting in a variety of cellular responses, including the production of interferons (IFNs) and pro-inflammatory cytokines. In this review, we discuss sensing of different types of glycosylated PAMPs such as β-glucan (a polymeric sugar) or lipopolysaccharides, nucleic acid, and so on (sugar complex PAMPs) by different families of sensors, its role in pathogenesis, and its application in development of potential vaccine and vaccine adjuvants.