Potentiation of Recombinant NP and M1-Induced Cellular Immune Responses and Protection by Physical Radiofrequency Adjuvant

Abstract

Nucleoprotein (NP) and matrix protein 1 (M1) are highly conserved among influenza A viruses and have been attractive targets to develop vaccines to elicit cross-reactive cytotoxic T lymphocytes (CTLs). Yet, external antigens are often presented on major histocompatibility complex class II molecules and elicit humoral immune responses. In this study, we present a physical radiofrequency adjuvant (RFA) to assist recombinant NP and M1 to elicit potent CTL responses. We found recombinant NP/M1 immunization in the presence of RFA could elicit potent anti-NP CTLs and confer significant protection against homologous viral challenges, while NP/M1 immunization alone failed to elicit significant CTL responses or confer significant protection. Interestingly, RFA failed to elicit potent anti-M1 CTL responses or anti-NP or anti-M1 antibody responses. Different from RFA, AddaVax adjuvant was found to significantly increase NP-specific antibody responses but not CTLs. NP/M1 immunization in the presence of RFA or AddaVax similarly reduced body weight loss, while only the former significantly increased the survival. We further found NP/M1 immunization in the presence of RFA did not significantly increase serum IL-6 release (a systemic inflammatory mediator) and rather reduced serum IL-6 release after boost immunization. NP/M1 immunization in the presence of RFA did not induce significant local reactions or increase body temperature of mice. The high potency and safety strongly support further development of RFA-based recombinant NP/M1 vaccine to elicit cross-protective immunity.

Effective adjuvantation of nanograms of influenza vaccine and induction of cross-protective immunity by physical radiofrequency adjuvant

“…Regarding cross-protective mechanisms, it might be due to the induction of cross-reactive cytotoxic T lymphocyte (CTL) responses in the absence of significant HI titers elicited against heterologous or heterosubtypic viral strains (data not shown). In support, our prior studies found RFA could elicit potent CTL responses against OVA, rHA, and NP/M1 18,20 .…”

“…RFA boosts seasonal influenza vaccination. Our previous studies found the physical RFA could enhance the efficacy of influenza pandemic 2009 H1N1 vaccine, split virion H5N1 vaccine, and intracellular NP/M1 vaccine [18][19][20] . It remained to be explored whether RFA was also effective to boost seasonal influenza vaccination.…”

“…Hair on the lateral back skin of mice was removed one day before experiment by clipping and application of hair-removal lotion. Next day, hair-removed skin was exposed to RF or sham treatment followed by ID injection of vaccine into RF-or sham-treated skin as in our previous reports [18][19][20] . In chemical adjuvant groups, mice were intramuscularly injected with the same amount of vaccine in the presence of AddaVax (50%, vol/vol) except otherwise specified.…”

Physical radiofrequency adjuvant enhances immune responses to influenza H5N1 vaccination

“…We further found RFA showed a similar or better adjuvant effect than MF59‐like AddaVax adjuvant to boost pdm09 vaccination depending on vaccine doses 22 . Recently, we found RFA could also significantly enhance recombinant nucleoprotein (NP)‐induced cellular immune responses and confer significant protection against lethal viral challenges in murine models 23 . Physical RFA has the advantage that it does not need to be mixed with vaccines and it can be stored at room temperature and conveniently used to boost vaccination.…”

“…22 Recently, we found RFA could also significantly enhance recombinant nucleoprotein (NP)-induced cellular immune responses and confer significant protection against lethal viral challenges in murine models. 23 Physical RFA has the advantage that it does not need to be mixed with vaccines and it can be stored at room temperature and conveniently used to boost vaccination. This study explored whether the physical RFA could significantly enhance H5N1 vaccine immunogenicity and protective efficacy in murine models.…”