Construction and evaluation of a Salmonella Paratyphi A vaccine candidate based on a poxA gene mutation.

Salmonella Paratyphi A, the pathogen of paratyphoid A accounts for an obviously growing proportion of cases in many areas. Therefore, development of specific paratyphoid A vaccines is needed. In the present study, the poxA gene of Salmonella Paratyphi A, encoding the aminoacyl-tRNA synthetase, was deleted successfully by the method of lambda Red recombination system, the resulting strain, ΔpoxA was characterized in respect of growth, adhesion and invasion, virulence, immunogenicity and protective efficacy. It was found that the growth of the ΔpoxA strain was significantly delayed compared with the wild type strain, the mutant ΔpoxA was less invasive to Caco-2 BBE epithelioid cells and THP-1 macrophages than the wild type strain, strain ΔpoxA was attenuated at least 1000-fold in mice, significant immune response and efficient protection were provided by the mutant ΔpoxA after oral immunization. It is concluded that the Salmonella Paratyphi A poxA deletion mutant ΔpoxA can be used as a live oral vaccine candidate against paratyphoid A.

Salmonella Pullorum lacking srfA is attenuated, immunogenic and protective in chickens.

Sallmonella Pullorum is a host-restricted pathogen for poultry and causes severe economic importance in many developing countries. The development of novel vaccines for Salmonella Pullorum is necessary to eradicate the prevalence of the pathogen. In our study, a srfA deletion mutant (C79-13ΔsrfA) of Salmonella Pullorum was constructed, and then the biological characteristics and protective efficacy of the mutant were evaluated. The mutant C79-13ΔsrfA was much less virulent than its parental strain C79-13 in one-day-old HY-line white chickens, immunization with C79-13ΔsrfA (4 × 107 CFU) through oral pathway induced highly specific humoral and cellular immune responses, the growth performance of vaccinated chickens was consistent with that of unvaccinated chickens. The survival percentages of vaccinated chickens reached 90% and 80%, after challenge with Salmonella Pullorum strain C79-13 and Salmonella Gallinarum strain SG9 at 10 days post-immunization (dpi), respectively. Collectively, our results indicate that C79-13ΔsrfA is a live attenuated vaccine candidate.

Characterization and protective efficacy of a sptP mutant of Salmonella Paratyphi A.

BACKGROUND: Salmonella Paratyphi A causes paratyphoid A, a severe systemic disease of people and remains a major public health problem in many parts of the world. In the interest of researching the roles of sptP on Salmonella Paratyphi A and developing a live-attenuated vaccine candidate, an sptP mutant of Salmonella Paratyphi A SPA017 (SPA017ΔsptP) was constructed, and then its characterization, immunogenicity, and protective ability were evaluated. RESULTS: The deletion of sptP had no effect on growth and biochemical properties. Adhesion and invasion assays showed that the lack of sptP did not affect the adhesion of Salmonella Paratyphi A, but the invasive ability of the mutant strain was significantly decreased, the half-lethal dose (LD50 ) of the mutant strain was 1.43 × 104 times of the parent strain in intraperitoneally injected mice. Single intraperitoneal vaccination with SPA017ΔsptP (1 × 105 CFU) in mice did not affect the body weight or elicit clinical symptoms relative to the control group, SPA017ΔsptP bacteria were isolated from livers and spleens of vaccinated mice at 14 days postvaccination. Notably, specific humoral and cellular immune responses were significantly induced. The protective assessment showed that the mutant strain could provide high-level protection against subsequent challenge with the wild-type SPA017 strain. CONCLUSIONS: These results demonstrated that SptP plays an essential role in the pathogenicity of Salmonella Paratyphi A, and Salmonella Paratyphi A lacking sptP is immunogenic and protective in mice.

Hsa_circ_0137008 suppresses the malignant phenotype in colorectal cancer by acting as a microRNA-338-5p sponge.

BACKGROUND: Circular RNAs (circRNAs) have been shown to play a crucial role in tumorigenesis. In this study, we investigated the function of hsa_circ_0137008 and its underlying molecular mechanism in colorectal cancer (CRC). METHODS: Gene expression was conducted by quantitative real-time PCR or western blot. Functional experiments were performed by cell count kit-8, colony formation assay, wound healing, and transwell assays. Luciferase reporter assay and RNA pull-down assay were performed to investigate the molecular mechanism of hsa_circ_0137008 in CRC. In addition, the xenograft tumor model was applied to determine the role of hsa_circ_0137008 in vivo. RESULTS: Downregulation of hsa_circ_0137008 was observed in CRC tissues and cell lines. Functionally, overexpression of hsa_circ_0137008 inhibited the proliferation of CRC cells, as indicated by the inhibition of proliferative protein expression (Ki67 and PCNA), reduced cell viability and colony formation ability. Upregulation of hsa_circ_0137008 suppressed the migration, invasion, and epithelial to mesenchymal transition (EMT) of CRC cells. Mechanically, hsa_circ_0137008 negatively regulated the expression of microRNA-338-5p (miR-338-5p). Furthermore, hsa_circ_0137008 abated the miR-338-5p mediated promotion on CRC cell progression. Tumor suppressive function of hsa_circ_0137008 was validated in vivo. CONCLUSION: These findings highlighted the fact that overexpression of hsa_circ_0137008 inhibited the progression of CRC via sponging miR-338-5p, suggesting that hsa_circ_0137008/miR-338-5p axis is a principal regulator of CRC tumorigenesis.

Characterization and protective efficacy of a Salmonella pathogenicity island 2 (SPI2) mutant of Salmonella Paratyphi A.

Paratyphoid fever caused by Salmonella Paratyphi A is a serious public health problem in many countries. In order to and develop a live attenuated candidate vaccine of Salmonella Paratyphi A, a Salmonella pathogenicity island 2 (SPI2, approximate 40 kb) deletion mutant of Salmonella Paratyphi A was constructed by lambda Red recombination, then the biological characteristics and protective ability of the Salmonella Paratyphi A SPI2 mutant were evaluated. Our results showed that the growth and biochemical properties of the SPI2 mutant were consistent with that of its parent strain, and the mutant was stable with the loss of SPI2. The mice lethal test showed that the virulence of the SPI2 mutant was significantly decreased, it can colonize and persistent more than 14 days in the liver and spleen of mice. Vaccination with the SPI2 mutant in mice revealed no significant effect on body weight and clinical symptoms compared to control animals, and specific humoral and cellular immune responses were also significantly induced. Immunization of mice offered efficient protection against Salmonella Paratyphi A strain challenge at 14 days post vaccination based on mortality and clinical symptoms relative to control group. Overall, these findings suggested that SPI2 plays an important role in pathogenicity of Salmonella Paratyphi A, and the SPI2 mutant showed its potential to develop a live attenuated vaccine candidate.