Antigen Localization Influences the Magnitude and Kinetics of Endogenous Adaptive Immune Response to Recombinant Salmonella Vaccines

The Trimeric Autotransporter Adhesin SadA from Salmonella spp. as a Novel Bacterial Surface Display System

Bacterial surface display platforms have been developed for applications such as vaccine delivery and peptide library screening. The type V secretion system is an attractive anchoring motif for the surface expression of foreign proteins in gram-negative bacteria. SadA belongs to subtype C of the type V secretion system derived from Salmonella spp. and promotes biofilm formation and host cell adherence. The inner membrane lipoprotein SadB is important for SadA translocation. In this study, SadA was used as an anchoring motif to expose heterologous proteins in Salmonella typhimurium using SadB. The ability of SadA to display heterologous proteins on the S. typhimurium surface in the presence of SadB was approximately three-fold higher than that in its absence of SadB. Compared to full-length SadA, truncated SadAs (SadA877 and SadA269) showed similar display capacities when exposing the B-cell epitopes of urease B from Helicobacter pylori (UreB158-172aa and UreB349-363aa). We grafted different protein domains, including mScarlet (red fluorescent protein), the urease B fragment (UreBm) from H. pylori SS1, and/or protective antigen domain 4 from Bacillus anthracis A16R (PAD4), onto SadA877 or SadA1292. Whole-cell dot blotting, immunofluorescence, and flow cytometric analyses confirmed the localization of Flag×3-mScarlet (~30 kDa) and Flag×3-UreBm-mScarlet (~58 kDa) to the S. typhimurium surface using truncated SadA877 or SadA1292 as an anchoring motif. However, Flag×3-UreBm-PAD4-mScarlet (~75 kDa) was displayed on S. typhimurium using SadA1292. The oral administrated pSadBA1292-FUM/StmΔygeAΔmurI and pSadBA877-FUM/StmΔygeAΔmurI could elicit a significant mucosal and humoral immunity response. SadA could thus be used as an anchoring motif for the surface expression of large heterologous proteins as a potential strategy for attenuated bacterial vaccine development.

Can Breast Implants Induce Breast Cancer Immunosurveillance? An Analysis of Antibody Response to Breast Cancer Antigen following Implant Placement

BACKGROUND

Women with cosmetic breast implants have significantly lower rates of subsequent breast cancer than the general population (relative risk, 0.63; 95 percent CI, 0.56 to 0.71). The authors hypothesize that breast implant-induced local inflammation stimulates immunosurveillance recognition of breast tumor antigen.

METHODS

Sera were collected from two cohorts of healthy women: women with long-term breast implants (i.e., breast implants for >6 months) and breast implant-naive women. Antibody responses to breast tumor antigens were tested by enzyme-linked immunosorbent assay and compared between cohorts by unpaired t test. Of the implant-naive cohort, nine women underwent breast augmentation, and antibody responses before and after implant placement were compared by paired t test.

RESULTS

Sera were collected from 104 women: 36 (34.6 percent) long-term breast implants and 68 (65.4 percent) implant-naive women. Women with long-term breast implants had higher antibody responses than implant-naive women to mammaglobin-A (optical density at 450 nm, 0.33 versus 0.22; p = 0.003) and mucin-1 (optical density at 450 nm, 0.42 versus 0.34; p = 0.02). There was no difference in antibody responses to breast cancer susceptibility gene 2, carcinoembryonic antigen, human epidermal growth factor receptor-2, or tetanus. Nine women with longitudinal samples preoperatively and 1 month postoperatively demonstrated significantly elevated antibody responses following implant placement to mammaglobin-A (mean difference, 0.13; p = 0.0002) and mucin-1 (mean difference 0.08; p = 0.02). There was no difference in postimplant responses to other breast tumor antigens, or tetanus.

CONCLUSIONS

Women with long-term breast implants have higher antibody recognition of mammaglobin-A and mucin-1. This study provides the first evidence of implant-related immune responses to breast cancer antigens.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Mice Deficient in T-bet Form Inducible NO Synthase-Positive Granulomas That Fail to Constrain Salmonella

Clearance of intracellular infections caused by Salmonella Typhimurium (STm) requires IFN-γ and the Th1-associated transcription factor T-bet. Nevertheless, whereas IFN-γ^-/- mice succumb rapidly to STm infections, T-bet^-/- mice do not. In this study, we assess the anatomy of immune responses and the relationship with bacterial localization in the spleens and livers of STm-infected IFN-γ^-/- and T-bet^-/- mice. In IFN-γ^-/- mice, there is deficient granuloma formation and inducible NO synthase (iNOS) induction, increased dissemination of bacteria throughout the organs, and rapid death. The provision of a source of IFN-γ reverses this, coincident with subsequent granuloma formation and substantially extends survival when compared with mice deficient in all sources of IFN-γ. T-bet^-/- mice induce significant levels of IFN-γ^- after challenge. Moreover, T-bet^-/- mice have augmented IL-17 and neutrophil numbers, and neutralizing IL-17 reduces the neutrophilia but does not affect numbers of bacteria detected. Surprisingly, T-bet^-/- mice exhibit surprisingly wild-type-like immune cell organization postinfection, including extensive iNOS⁺ granuloma formation. In wild-type mice, most bacteria are within iNOS⁺ granulomas, but in T-bet^-/- mice, most bacteria are outside these sites. Therefore, Th1 cells act to restrict bacteria within IFN-γ-dependent iNOS⁺ granulomas and prevent dissemination.

Complete genome sequence of Helicobacter pylori B128 7.13 and a single-step method for the generation of unmarked mutations

BACKGROUND

Helicobacter pylori represents an interesting model of bacterial pathogenesis given that most infections are asymptomatic, while a minority of infections cause severe gastric disease. H pylori strain B128 7.13 is used extensively to understand H pylori pathophysiology. Due to extensive restriction-modification systems, the fact that only some H pylori strains are naturally transformable, the inability of common plasmid and transposon vectors to replicate in this bacterium, as well as the limited number of antibiotic cassettes that are functional in H pylori, there are relatively few genetic tools for the mutagenesis of this bacterium.

MATERIALS AND METHODS

Here, we use PacBio and Illumina sequencing to reveal the complete genome sequence of H pylori B128 7.13. Furthermore, we describe a system to generate markerless and scarless mutations on the H pylori chromosome using the counter-selection marker, galactokinase from Escherichia coli.

RESULTS

We show that this mutagenesis strategy can be used to generate in-frame insertions, gene deletions, and multiple independent mutations in B128 7.13. Using the closed genome as a reference, we also report the absence of second site chromosomal mutations and/or rearrangements in our mutagenized strains. We compare the genome sequence of H pylori B128 7.13 with a closely related strain, H pylori B8, and reveal one notable region of difference, which is a 1430 bp insertion encoding a H pylori-specific DUF874 family protein of unknown function.

CONCLUSIONS

This article reports the closed genome of the important H pylori B128 7.13 strain and a mutagenesis method that can be adopted by researchers as an alternative strategy to generate isogenic mutants of H pylori in order to further our understanding of this bacterium.

Evaluation of the Effect of Promoter Type on the Immunogenicity of the Live Recombinant Salmonella Vaccines Expressing Escherichia Coli Heat-labile Enterotoxins (LTB)

Enterotoxigenic Escherichia coli (ETEC)-induced diarrhoea is the second most common cause of death in children in the developing countries. Heat labile toxin (LT) is responsible for ETEC-induced diarrhoea. In the present study, a novel live ETEC vaccine based on subunit B of LT (LTB) expression in attenuated PhoP^c Salmonella strain was developed. Herein, we aimed to compare the in-vitro activity of promoters including constitutive tac, IPTG inducible trc, and in-vivo-inducible (nirB and nirB78-23) in PhoP^c. Additionally, the ability of these recombinant PhoP^c/pLTBs to induce LTB-specific antibody responses in BALB/c mice after nasal immunization was evaluated. In-vitro studies demonstrated that PhoP^c has the ability to produce rLTB. Furthermore, nirB promoter directed significantly more LTB expression in PhoP^c/pnirBLTB under anaerobic condition without induction compared to the amount of rLTB secreted by PhoP^c/ptrcLTB in bacterial soup under uninduced condition (6.06 ± 0.05 vs. 1.4 ± 0.46 μg/10⁹ cfu, p < 0.01). In addition, the constitutive rLTB expression from tac promoter was more than its expression from uninduced trc promoter in bacterial soup (4.2 ± 0.92 vs. 1.4 ± 0.46 (μg/10⁹ cfu)) and pellet (27.4 ± 0.89 vs. 13.4 ± 1.42 (μg/10⁹ cfu), p < 0.0001). However, the mice immunized with PhoP^c/ptrcLTB elicited the superior anti-LTB responses among the PhoP^c containing the examined prompters, which were significantly higher than those induced by PhoP^c/pnirB78-23LTB and PhoP^c/pnirB, 6 weeks after the first immunization. Totally, it could be concluded that in-vitro analysis of promoters for LTB expression in PhoP^c may not necessarily predict the recombinant PhoP^c immunogenicity.