Li Yibo, Li Zhuofan, Zhao Yiwen, Chen Xinyuan
Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, Kingston, RI 02881, USA.
Vaccines (Basel). 2021 Nov 24;9(12):1382. doi: 10.3390/vaccines9121382.
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.
核蛋白（NP）和基质蛋白1（M1）在甲型流感病毒中高度保守，一直是开发能引发交叉反应性细胞毒性T淋巴细胞（CTL）疫苗的诱人靶点。然而，外部抗原通常呈递于主要组织相容性复合体II类分子上并引发体液免疫反应。在本研究中，我们展示了一种物理射频佐剂（RFA），以协助重组NP和M1引发强效CTL反应。我们发现，在RFA存在的情况下进行重组NP/M1免疫接种能够引发强效抗NP CTL，并对同源病毒攻击提供显著保护，而单独进行NP/M1免疫接种则无法引发显著的CTL反应或提供显著保护。有趣的是，RFA未能引发强效抗M1 CTL反应或抗NP或抗M1抗体反应。与RFA不同，发现AddaVax佐剂可显著增加NP特异性抗体反应，但不能增加CTL反应。在RFA或AddaVax存在的情况下进行NP/M1免疫接种同样可减轻体重减轻，而只有前者能显著提高生存率。我们进一步发现，在RFA存在的情况下进行NP/M1免疫接种不会显著增加血清IL-6释放（一种全身炎症介质），反而在加强免疫后降低了血清IL-6释放。在RFA存在的情况下进行NP/M1免疫接种不会引发显著的局部反应，也不会升高小鼠体温。RFA的高效性和安全性有力地支持了基于RFA的重组NP/M1疫苗的进一步开发，以引发交叉保护性免疫。
