Journal of Vaccines & Vaccination

Development and evaluation of Staphylococcus epidermidis DNA, mRNA and protein vaccines

4^th International Conference on Vaccines & Vaccination

September 24-26, 2014 Valencia Convention Centre, Spain

Lin Yan

Accepted Abstracts: J Vaccines Vaccin

Abstract:

Objectives: The traditional antibiotic and drug-release treatments are ineffective against biomaterial infections due to the inherent resistance of bacterial biofilms to antibiotics and host defense. A long-term immune response to specific bacterial colonization may hold the promise for life-time prevention of biomaterial infections. In this study, we targeted Staphylococcus epidermidis (S. epidermidis)- one of the leading nosocomial pathogens, and developed the DNA, mRNA and protein vaccines expressingthe Accumulation Associated Protein (AAP)- a S. epidermidis protein employed to form biofilms on the first stage of S. epidermidis infection, and investigated the potential of these vaccines against biomaterial associated infections in vitro and in vivo. Methods: The gene fragment encoding a 128 aa G5 domain of AAP was cloned into the plasmidsp VAX1, pGEM4z-A64and pET21, yielding pVAX/aap as the DNA vaccine; pGEM/aap, the precursor for the mRNA vaccine; and pET21/aap to express AAP as the protein vaccine. C57B/6 mice were divided into six groups, and subcutaneously injected with 25 μg naked DNAaap, 25μg DNAaap+PEI, 5μg naked mRNAaap, 5μg mRNA aap+PEI, 100 μg protein AAP, or 100μg protein OVA as a control at week 0, 2 and 3. Serum was collected for IgG, IgG1 and IgG2a antibody analysis by ELISA, as well for biofilm inhibition assays. Splenocytes were isolated for AAP-specific IFN ELISA and flow cytometry analysis. Results: Strong anti-S. epidermidis antibody response were developed in protein AAP-immunized mice. Mice immunized with the AAP protein vaccine developed dramatically highest anti-S. epidermidis IgG antibody response compared to other groups of mice. Biofilm inhibition assays further indicated that the high levels of antibodies could inhibit S. epidermidis RP62A biofilm formation in a dose-dependent pattern (Fig.1). We observed a relative weak anti-AAP and S. epidermidis IgG responses in Nucleic Acid vaccine groups, while the naked DNAaap induced slightly higher antibodies. IgG1 and IgG2a antibody ratio analysis indicated that the protein vaccine induced Th2 immune responses, whereas the pDNA/mRNA vaccines promoted Th1-biased immunity. Significant AAP-specific IFNg responses were induced in DNA- and mRNA-aap immunized mice. Though relative weak antibody responses in nucleic acid vaccine groups, mice received either DNA- or mRNA-aap vaccines, whether naked or complexed with PEI, developed strong antigen-specific IFNg responses in spenocytes. Though there were no significant difference between the naked DNA and the DNA+PEI vaccines, we observed a significant higher IFNg response in the mRNA+PEI group of mice compared to the naked mRNA group. These results were consistent with the data obtained from flow cytometry analysis of AAP-activated CD4 + IFNg+ and CD8 + IFNg+spelnocytes. Conclusions: Our study validated the potential of S. epidermidis DNA/mRNA/protein vaccines in developing both antibody and cellular immune responses against S. epidermidis biofilm formation