Suppressive Effects on the Immune Response and Protective Immunity to a JEV DNA Vaccine by Co-administration of a GM-CSF-Expressing Plasmid in Mice

Abstract

As a potential cytokine adjuvant of DNA vaccines, granulocyte-macrophage colony–stimulating factor (GM-CSF) has received considerable attention due to its essential role in the recruitment of antigen-presenting cells, differentiation and maturation of dendritic cells. However, in our recent study of a Japanese encephalitis virus (JEV) DNA vaccine, co-inoculation of a GM-CSF plasmid dramatically suppressed the specific IgG response and resulted in decreased protection against JEV challenge. It is known that GM-CSF has been used in clinic to treat neutropenia for repopulating myeloid cells, and as an adjuvant in vaccine studies; it has shown various effects on the immune response. Therefore, in this study, we characterized the suppressive effects on the immune response to a JEV DNA vaccine by the co-administration of the GM-CSF-expressing plasmid and clarified the underlying mechanisms of the suppression in mice. Our results demonstrated that co-immunization with GM-CSF caused a substantial dampening of the vaccine-induced antibody responses. The suppressive effect was dose- and timing-dependent and likely related to the immunogenicity of the antigen. The suppression was associated with the induction of immature dendritic cells and the expansion of regulatory T cells but not myeloid-derived suppressor cells. Collectively, our findings not only provide valuable information for the application of GM-CSF in clinic and using as a vaccine adjuvant but also offer further insight into the understanding of the complex roles of GM-CSF.

Cross-protection induced by Japanese encephalitis vaccines against different genotypes of Dengue viruses in mice

“…The mouse serum samples were collected three weeks after the final immunization and then analyzed for the presence of cross-reactive antibodies to DENVs by ELISA, as previously described 39 40 . Briefly, the concentrated viral particles of DENV1-4 were diluted and 96-well plates were coated with 10 μg of the concentrated DENV1, 2, 3 or 4 in each well in 100 μl of carbonate-bicarbonate buffer (NaHCO 3 , 18.2 mMNa 2 CO 3 , pH 9.6) at 4 °C overnight.…”

Inactivated genotype 1 Japanese encephalitis vaccine for swine

“…In order to increase the immunogenicity of the vaccine, an alternative approach is to co-deliver adjuvants with antigens to up-regulate the immune response of vaccine, and to include interleukin-2, flagellin and granulocyte monocyte-colony stimulating factor (GM-CSF) [6,13,14]. GM-CSF is a pleiotropic cytokine and has been used as adjuvant to enhance immune response of many vaccine antigens [13].…”

Immunization with E Plus NS1-2a Enhanced Protection against Dengue Virus Serotype 2 in Mice

“…The genes were constructed in the vector pReceiverM01 and were named pRe/E and pRe/NS1-2a. The recombinant plasmids were identified by sequence analysis (Sangon Biotech Co., Ltd., Shanghai, China) and the expression of the proteins was confirmed by indirect immunofluorescence (IFA) [19]. In brief, plasmids were transfected into Vero cells by Lipofectamine 2000 (Invitrogen, California, USA).…”

“…Mouse serum samples were collected by tail-bleeding three weeks after the final immunization, and the antibodies against DENV2 were evaluated using ELISA as described previously [19].…”