Lipopolysaccharide Inhibits FI-RSV Vaccine-enhanced Inflammation Through Regulating Th Responses.

Respiratory syncytial virus (RSV) infection is the primary cause of respiratory disease in infants. The formalin-inactivated RSV (FI-RSV) vaccine resulted in an enhanced respiratory disease (ERD) in infants upon natural RSV infection, which is a major obstacle for development of safe and efficacious vaccines. Excessive and uncontrolled Th immune responses could be involved in the ERD. Agonists of TLRs are used as adjuvants to guide the type of immune response induced by vaccines. We evaluated the impact of lipopolysaccharide (LPS), the agonist of TLR4, on ERD as the adjuvant of FI-RSV. The results showed that LPS remarkably inhibited FI-RSV-enhanced lung inflammation, mucus production, airway inflammatory cell infiltration, and inflammatory cytokines following RSV challenge. Interestingly, LPS inhibited both Th2 and Th17 type cytokines in lungs of FI-RSV-immunized mice following RSV challenge, without an increase in the Th1 type cytokines, suggesting a controlled immune response. In contrast, Pam3Cys and Poly(I:C), the agonist of TLR1/2 or TLR3, partly inhibited FI-RSV-enhanced lung inflammation. Pam3Cys inhibited Th17 type cytokine IL-17, but promoted both Th1 and Th2 type cytokines. Poly(I:C) inhibited Th2 and Th17 type cytokines, but promoted Th1 type cytokines. In addition, LPS promoted IgG and IgG2a antibody production, which might provide protection from RSV challenge. These results suggest that LPS inhibits ERD without impairment in antibody production and protection, and the mechanism appears to be related with regulation of Th responses induced by FI-RSV.

Similar ability of FbaA with M protein to elicit protective immunity against group A streptococcus challenge in mice.

Group A streptococcus (GAS), an important human pathogen, can cause various kinds of infections including superficial infections and potentially lethal infections, and the search for an effective vaccine to prevent GAS infections has been ongoing for many years. This paper compares the immunogenicity and immunoprotection of FbaA (an Fn-binding protein expressed on the surface of GAS) with that of M protein, the best immunogen of GAS. Assay for immune response showed that FbaA, similar to M protein, could induce protein-specific high IgG titer in BALB/c mice. Furthermore, following GAS challenge, the mice immunized with FbaA showed the same protective rate as those with M protein. These results indicate that FbaA is similar in ability to M protein in inducing protective immunity against GAS challenge in mice.

Induction of balanced immunity in BALB/c mice by vaccination with a recombinant fusion protein containing a respiratory syncytial virus G protein fragment and a CTL epitope.

Respiratory syncytial virus (RSV), an important pathogen of the lower respiratory tract, is responsible for severe illness both in new born and young children and in elderly people. However, development of a RSV vaccine has been hampered by the outcome of the infant trials in the 1960s with a formalin-inactivated RSV (FI-RSV) preparation. Previous studies in mice indicated that G protein immunization resulted in antibody and Th2-type response and failed to induce MHC I-restricted CD8(+) T-cell response. Vaccines designed to induce CD8(+) T-cell along with antibody response might be ideal. In the present report, a fusion protein G1F/M2 containing a RSV-G protein fragment (G: 125-225 amino acid) and a CD8(+) T-cell epitope from RSV-M2 protein was investigated. G1F/M2 was cloned, expressed in E. coli, purified and renaturated. In BALB/c mice, G1F/M2 induced not only humoral immunity but also cellular immunity. In addition, interestedly, G1F/M2 elicited balanced IgG1/IgG2a response. These results suggest that the fusion protein G1F/M2 is potential as a RSV subunit vaccine.

[Plasmid construction, expression, immunogenicity and protective efficacy of recombinant protein candidate vaccine of respiratory syncytial virus].

To construct plasmid of recombinant protein candidate vaccine of respiratory syncytial virus, express it in E. coli, and to investigate its immunogenicity and protective efficacy. A CD8+ T cell epitope from respiratory syncytial virus (RSV) M2 protein F/M2:81 - 95 and the G:125-225 (G1) gene fragments from RSV-G protein containing B cell epitopes were amplified by PCR method and then inserted into the prokaryotic expression vector pET-DsbA after bonding to a linker. The fusion protein DsbA-G1-Linker-F/M2:81-95 (D-G1LF/M2) was expressed successfully in E. coli BL21 (DE3). The product was proved to be RSV-specific by Western-blot. After purified by affinity chromatography on Ni+ Sepharose and renatured by gradient dialysis. D-G1LF/M2 was used to immune BALB/c mice. D-G1LF/M2 induced high anti-D-G1LF/M2 IgG, anti-RSV IgG and neutralizing antibody titers in serum and lung of BALB/c mice, and elicied RSV-specific CTL responses. The IgG subclass distribution revealed that IgG1/IgG2a ratio was 2.66. Viral titration indicated that D-G1LF/M2 could protect BALB/c mice against RSV challenge in lung.

Fusion of DsbA to the N-terminus of CTL chimeric epitope, F/M2:81-95, of respiratory syncytial virus prolongs protein- and virus-specific CTL responses in Balb/c mice.

In an effort to seek a means of inducing long lasting respiratory syncytial virus-specific CTL responses in mice, we constructed a new recombinant protein, DsbA-F/M2:81-95, by fusing carrier protein DsbA (disulfide bond isomerase) to the N-terminus of CTL chimeric epitope F/M2:81-95 of this virus. DsbA-F/M2:81-95 can induce effectively virus-specific CTL responses as well as protective immunity without association with enhanced disease. Furthermore, compared with F/M2:81-95 alone, it increases the longevity of CTL responses in vivo up to 2.93 folds. Our study emphasizes that appropriate stimulation of non-antigen-specific T helper cells is essential to induce long lasting CD8+ CTL, and also implies DsbA-F/M2:81-95 may be a promising candidate for RSV vaccine development since it is an efficacious and safe immunogen.