Coexpression of Flt3 ligand and GM-CSF genes modulates immune responses induced by HER2/neu DNA vaccine

Abstract

DNA vaccine and dendritic cells (DCs)-based vaccine have emerged as promising strategies for cancer immunotherapy. Fms-like tyrosine kinase 3-ligand (Flt3L) and granulocyte-macrophage-colony-stimulating factor (GM-CSF) have been exploited for the expansion of DC. It was reported previously that combination of plasmid encoding GM-CSF with HER2/neu DNA vaccine induced predominantly CD4þ T-cell-mediated antitumor immune response. In this study, we investigated the modulation of immune responses by murine Flt3L and GM-CSF, which acted as genetic adjuvants in the forms of bicistronic (pFLAG) and monocistronic (pFL and pGM) plasmids for HER2/neu DNA vaccine (pN-neu). Coexpression of Flt3L and GM-CSF significantly enhanced maturation and antigen-presentation abilities of splenic DC. Increased numbers of infiltrating DC at the immunization site, higher interferon-g production, and enhanced cytolytic activities by splenocytes were prominent in mice vaccinated with pN-neu in conjunction with pFLAG. Importantly, a potent CD8 þ T-cell-mediated antitumor immunity against bladder tumors naturally overexpressing HER2/neu was induced in the vaccinated mice. Collectively, our results indicate that murine Flt3L and GM-CSF genes coexpressed by a bicistronic plasmid modulate the class of immune responses and may be superior to those codelivered by two separate monocistronic plasmids as the genetic adjuvants for HER2/neu DNA vaccine.

Modulation of Immunogenicity and Immunoprotection of Mucosal Vaccine Against Coxsackievirus B3 by Optimizing the Coadministration Mode ofLymphotactinAdjuvant

“…The third reason may be that VP1 antigen could be better processed in antigen-presenting cells (APCs) when DNA plasmids are administered separately. Herein, our observation was not in agreement with previous studies showing that intramuscular injection of bicistronic plasmid provoked more potential systemic immune responses than the mixture of two monocistronic plasmids encoding antigen and adjuvant (Yo et al, 2007;Tang et al, 2008). However, there is also a lot of evidence indicating that simultaneous delivery of antigens and adjuvants in nanoparticles ensures that both agents can be efficiently expressed and delivered into the same APC or T cell population and the maximal adjuvant effects could be achieved (Singh et al, 2001;Vajdy et al, 2004).…”

“…Previous studies have suggested that the temporal and spatial coexpression of antigens and adjuvants seems to be critical for optimal immune priming. Yo et al (2007) found that compared with two monocistronic plasmids, coexpression of FMS (colony stimulating factor 1 receptor)-like tyrosine kinase 3 receptor ligand and granulocyte-macrophage colony-stimulating factor genes in a bicistronic plasmid could promote a potent CD8 + T cell immunity induced by human epidermal growth factor 2 (HER2)/neu DNA vaccine against bladder tumors. Fusion plasmid encoding human papillomavirus L1 protein with regulated upon activation normal T cell expressed and secreted (RANTES) generated higher frequency of specific splenic T cells than the combination of plasmids encoding L1 and RANTES separately (Kim et al, 2003).…”

Route of Vaccine Administration Influences the Impact of Fms-Like Tyrosine Kinase 3 Ligand (Flt3L) on Chlamydial-Specific Protective Immune Responses

“…The mechanism of immune enhancement by FL appears to be due to its ability to increase the number of DC recruited to the immunization site to elicit robust antigen-specific cellular responses (45, 46). Moreover, another study demonstrated that co-expression of FL and GM-CSF considerably improved the ability of splenic DC to mature and present antigen to T cells, which was associated with an increase in the number of DC recruited to the immunization site, production of higher levels of IFN-γ and increased cytotoxicity of splenocytes in vaccinated mice (28). This study, which employed HER2/neu (a target antigen for anticancer therapy) as a DNA vaccine to study the adjuvant effect of murine Flt3L and GM-CSF in different forms of plasmid construction further demonstrated that FL targets DCs that constitutively express the receptor CD135.…”

“…It binds to the fms-like tyrosine kinase receptor Flt3/Flk2 (CD135) and in collaboration with other growth factors, stimulates the proliferation and differentiation of various blood cell progenitors. For example, it dramatically increases immune cell number and has been exploited for dendritic cell (DC) expansion (28). Intranasal administration of Flt3L with P6 protein of non-typeable Haemophilus influenzae (NTHi) to mice increased dendritic cell number in the nasal-associated lymphoid tissue, significantly elevated P6-specific nasal mucosal IgA and serum IgG titers and boosted nasopharyngeal NTHi clearance (29).…”

“…A combination of Flt3L and CpG oligodeoxynucleotide adjuvants elicited secretory-IgA immune responses that protected aged mice against Streptococcus pneumoniae infection (30). A mixture of Flt3L and Granulocyte macrophage-colony stimulating factor (GM-CSF) considerably enhanced the maturation of splenic DC and their ability to present antigen to immune T cells (28) and elicited mucosal immunity to influenza in aging (31).…”