IL-17A Secreted by Th17 Cells Is Essential for the Host against Streptococcus agalactiae Infections.

Streptococcus agalactiae is an important bacterial pathogen and causative agent of diseases including neonatal sepsis and meningitis, as well as infections in healthy adults and pregnant women. Although antibiotic treatments effectively relieve symptoms, the emergence and transmission of multidrug-resistant strains indicate the need for an effective immunotherapy. Effector T helper (Th) 17 cells are a relatively newly discovered subpopulation of helper CD4+ T lymphocytes, and which, by expressing interleukin (IL)-17A, play crucial roles in host defenses against a variety of pathogens, including bacteria and viruses. However, whether S. agalactiae infection can induce the differentiation of CD4+ T cells into Th17 cells, and whether IL-17A can play an effective role against S. agalactiae infections, are still unclear. In this study, we analyzed the responses of CD4+ T cells and their defensive effects after S. agalactiae infection. The results showed that S. agalactiae infection induces not only the formation of Th1 cells expressing interferon (IFN)-γ, but also the differentiation of mouse splenic CD4+ T cells into Th17 cells, which highly express IL-17A. In addition, the bacterial load of S. agalactiae was significantly increased and decreased in organs as determined by antibody neutralization and IL-17A addition experiments, respectively. The results confirmed that IL-17A is required by the host to defend against S. agalactiae and that it plays an important role in effectively eliminating S. agalactiae. Our findings therefore prompt us to adopt effective methods to regulate the expression of IL-17A as a potent strategy for the prevention and treatment of S. agalactiae infection.

Immunogenicity of multi-epitope vaccines composed of epitopes from Streptococcus dysgalactiae GapC.

Glyceraldehyde-3-phosphate dehydrogenase C (GapC) of Streptococcus dysgalactiae (S. dysgalactiae) is a highly conserved surface protein that can induce a protective immune response against S. dysgalactiae infection. To investigate the immune response and protective efficacy induced by epitope-vaccines against S. dysgalactiae infection, we constructed epitope-vaccines GTB1, GB1B2, and GTB1B2 using a T cell epitope (GapC63-77, abbreviated as GT) and two B cell epitopes (GapC30-36, abbreviated as GB1, and GapC97-103, abbreviated as GB2), which were identified in GapC1-150 of S. dysgalactiae in tandem by a GSGSGS linker. BALB/c mice were immunized via an intramuscular injection with the epitope vaccines. The levels of the cytokines, IFN-γ, IL-4, and IL-17, secreted by splenic lymphocytes and the antibody levels in the sera of the immunized mice were detected by ELISA. The immunized mice were subsequently challenged with S. dysgalactiae, and the bacterial colonization in the immunized-mouse organs was examined using the plate counting method. The results showed that the level of the cytokines induced by GTB1B2 was lower than that induced by GapC1-150, but higher than that induced by other epitope vaccines. The level of IgG induced by GTB1B2 was lower than that induced by GapC1-150, but higher than the levels induced by other epitope vaccines. The bacterial colonization numbers in the organs of the mice immunized with GTB1B2 were higher those of the mice immunized with GapC1-150, but significantly lower than those from the mice immunized with other epitope-vaccines. Our results demonstrated that the T cell and B cell epitopes in the epitope-vaccines worked synergistically against bacterial challenge. The multi-epitope vaccine, GTB1B2, could induce stronger cellular and humoral immune responses, and provide a better protective effect against S. dysgalactiae infection.

A Putative Efflux Transporter of the ABC Family, YbhFSR, in Escherichia coli Functions in Tetracycline Efflux and Na+(Li+)/H+ Transport.

ATP-binding cassette transporters are ubiquitous in almost all organisms. The Escherichia coli genome is predicted to encode 69 ABC transporters. Eleven of the ABC transporters are presumed to be exporters, of which seven are possible drug export transporters. There has been minimal research on the function of YbhFSR, which is one of the putative drug resistance exporters. In this study, the ybhF gene of this transporter was characterized. Overexpression and knockout strains of ybhF were constructed. The ATPase activity of YbhF was studied using the malachite green assay, and the efflux abilities of knockout strains were demonstrated by using ethidium bromide (EB) as a substrate. The substrates of YbhFSR efflux, examined with the minimum inhibitory concentration (MIC), were determined to be tetracycline, oxytetracycline, chlortetracycline, doxycycline, EB, and Hoechst33342. Furthermore, tetracycline and EB efflux and accumulation experiments confirmed that the substrates of YbhFSR were tetracyclines and EB. The MIC assay and the fluorescence test results showed that tetracyclines are likely to be the major antibiotic substrate of YbhFSR. The existence of the signature NatA motif suggested that YbhFSR may also function as a Na+/H+ transporter. Overexpression of YbhF in E. coli KNabc lacking crucial Na+/H+ transporters conferred tolerance to NaCl, LiCl, and an alkaline pH. Together, the results showed that YbhFSR exhibited dual functions as a drug efflux pump and a Na+ (Li+)/H+ antiporter.

Identification of CD4+ T cell epitopes on glyceraldehyde-3-phosphate dehydrogenase-C of Staphylococcus aureus in Babl/c mice.

Glyceraldehyde-3-phosphate dehydrogenase-C (GapC) is a highly conserved surface protein of Staphylococcus aureus, with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity, which represents an excellent vaccine candidate antigen. It can induce protective immune responses to S. aureus infections. However, CD4+ T cell epitopes of GapC that induce CD4+ T cell immune responses are currently unclear. In this study, we used bioinformatics prediction algorithms to predict CD4+ T cell epitopes of GapC. Ten peptides were synthesized to investigate the candidate epitopes. Our results showed that the peptides, G4 (GapC 104-123) and G10 (GapC 314-333) were able to induce proliferation of CD4+ T cells and secrete high levels of interferon (IFN)-γ, respectively. In addition, they significantly reduced bacterial loads in tissue and induced immunoprotective effects. It is suggested that G4 and G10 are Th1-type epitopes of S. aureus GapC. This study provides the potential development of the design of epitope-based vaccine against S. aureus.