The Magnitude and IgG Subclass of Antibodies Elicited by Targeted DNA Vaccines Are Influenced by Specificity for APC Surface Molecules

Abstract

Upon APC-targeted DNA vaccination, transfected cells secrete fusion proteins with targeting units specific for surface molecules on APC. In this study, we have tested several different targeting units for their ability to influence the magnitude and subclass of Ab responses to hemagglutinin from influenza A virus. The experiments employed bivalent homodimeric Ig-based molecules (vaccibodies). The overall efficiency in BALB/c mice depended on the targeting units in the following order: αMHC class II > αCD11c > αCD40 > Xcl-1 = MIP-1α > FliC > GM-CSF > Flt-3L > αDEC205. GM-CSF induced mainly IgG1, whereas Xcl1, MIP-1α, αCD40, and αDEC205 induced predominantly IgG2a. A more balanced mixture of IgG1 and IgG2a was observed with αCD11c, αMHC class II, Flt-3L, and FliC. Similar results of IgG subclass–skewing were obtained in Th1-prone C57BL/6 mice with a more limited panel of vaccines. IgG1 responses in BALB/c occurred early after immunization but declined relatively rapidly over time. IgG2a responses appeared later but lasted longer (>252 d) than IgG1 responses. The most efficient targeting units elicited short- and long-term protection against PR8 influenza (H1N1) virus in BALB/c mice. The results suggest that targeting of Xcr1+ conventional type 1 dendritic cells preferentially induces IgG2a responses, whereas simultaneous targeting of several dendritic cell subtypes also induces IgG1 responses. The induction of distinct subclass profiles by different surface molecules supports the APC–B cell synapse hypothesis. The results may contribute to generation of more potent DNA vaccines that elicit high levels of Abs with desired biologic effector functions.

Enhanced germinal center reaction by targeting vaccine antigen to major histocompatibility complex class II molecules

“…Our side-by-side analysis of nine different APC targets for vaccines has demonstrated that MHCII-targeting was the most efficient for induction of antibodies. 17 This result is in agreement with our previous studies demonstrating that MHCII-targeted antigen could induce protective antibody responses, both in mice 10 and larger animals. 18 In mice, MHCII-targeted hemagglutinin (HA) induced complete antibody-mediated protection within 8 days against challenge with influenza virus, and protective immunity was maintained for at least 10 months.…”

“…DNA vaccines encoding fusion proteins that target antigens to MHC class II molecules elicit increased antibody responses. 10,17–19 To understand the mechanistic basis for these observations, we have here studied vaccine proteins in models with traceable T and B cells of known specificity. Protein delivery was chosen over DNA vaccination since the dose of administered protein could then be directly controlled.…”

DAMP-Inducing Adjuvant and PAMP Adjuvants Parallelly Enhance Protective Type-2 and Type-1 Immune Responses to Influenza Split Vaccination

“…Another type-2 adjuvant, Alum, is also an effective adjuvant for the influenza SV vaccine ( 41 ). In contrast, previous studies indicated that antibody-mediated responses such as antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) via Th1-related antibodies are also important for the elimination of influenza virus ( 16 – 19 ). Indeed, CpG-ODN is reported to enhance vaccine-induced type-1 (Th1) immune responses and protect the mice from lethal viral infections such as influenza ( 42 , 43 ).…”

“…HP-β-CyD and K3 CpG-ODN-adjuvanted influenza SV protected against challenge with a high dose of influenza virus, which the single adjuvant vaccines could not protect against (Figure 2 ), suggesting that the anti-viral immune response generated by this combination of adjuvants is very strong. Notably, this adjuvant combination greatly induced IgG2c production, which is reported to be correlated with anti-viral immunity including ADCC and CDC ( 15 – 19 ). In contrast, the production of IgE by the combined adjuvant was lower than that of HP-β-CyD alone, and the biocompatibility of these adjuvants is expected to be high because they have already been used in the clinic.…”

“…In contrast, type-1 adjuvants such as poly I:C and CpG-ODN enhance cellular immunity, including the induction of Th1 cells and the activation of cytotoxic T lymphocytes, NK cells and phagocytes ( 10 – 14 ). Moreover, Th1 cells induce Th1-related immunoglobulins which also contributes to the elimination of pathogens ( 15 – 19 ). Thus, type-2 type and type-1 type immune responses have different functions in the defense against infection, and the development of an adjuvant capable of inducing both immune responses may be preferable.…”