Human CCL27 mRNA

The rapid approval of SARS-CoV-2 mRNA lipid nanoparticle (LNP) vaccines demonstrates the broad potential of mRNA LNPs for urgent vaccine needs. Here, to improve the cross-protection of mRNA vaccines, researchers designed an advanced mRNA LNP that encapsulated mRNA constructs encoding cytokine adjuvants and influenza A hemagglutinin (HA) antigens for intradermal administration. The adjuvant mRNA encodes a novel fusion cytokine, GIFT4, composed of granulocyte colony-stimulating factor (GM-CSF) and interleukin (IL-4). The adjuvanted mRNA LNP vaccine was able to induce high levels of humoral antibodies and systemic T cell responses against heterologous influenza antigens and protected immunized mice from influenza A virus infection. In addition, the adjuvanted mRNA LNP vaccine elicited early germinal center responses in draining lymph nodes and promoted antibody-secreting B cell responses. The researchers also constructed another adjuvant mRNA encoding CCL27, which enhanced systemic immune responses. Both adjuvanted mRNAs showed potent adjuvant effects, enhancing humoral and cellular immune responses in mice. Notably, intradermal immunization of mRNA LNP vaccines adjuvanted with GIFT4 or CCL27 mRNA induced significant lung tissue-resident T cells. These findings suggest that cytokine mRNA can serve as a promising adjuvant that can be flexibly formulated into mRNA LNP vaccines to stimulate robust immunity against viral variants.

To test the effectiveness of the cytokine mRNA adjuvant platform in enhancing the immune response to the mRNA LNP vaccine, an alternative cytokine mRNA construct encoding secreted CCL27 was constructed (Figure 1A). CCL27 expression was confirmed by CCL27 ELISA using cell lysates and supernatants from cells transfected with commercially available liposomes (Figure 1B) or CCL27 mRNA LNPs. In a Transwell cell migration assay, lymphocytes from the spleen and mesenteric lymph nodes (MLN) of unvaccinated mice were cultured with supernatants from CCL27 mRNA-transfected cells. A significant increase in lymphocyte migration was observed after stimulation with CCL27 mRNA-expressing supernatants (Figure 1C), with cells cultured in medium containing soluble CCL27 as a positive control. These results indicate that CCL27 mRNA was successfully expressed in vitro and that the expressed CCL27 retained biological activity and promoted the migration of primary cells. In addition, the mRNA LNP vaccine adjuvanted with CCL27 mRNA induced a significant increase in Phi-specific IgG antibodies (Figure 1D). CCL27 mRNA adjuvant also promoted the production of Aichi virus-specific cytokines (IFN-γ and IL-6) in lymph nodes (Figure 1E-F) and triggered stronger cytokine (IFN-γ and IL-4) secreting T cell responses after stimulation with inactivated Aichi virus or A/Wis peptide (Figure 1G-J). Similar to the adjuvant effect of GIFT4 mRNA in mRNA LNP immunization, the data suggest that the addition of CCL27 mRNA adjuvant to mRNA LNP formulations can enhance humoral and cellular immune responses and improve cross-binding with heterologous viral antigens.

Figure 1. Characterization of CCL27 mRNA and humoral and cellular immune responses induced by CCL27 mRNA-adjuvanted LNP. (Wei L, et al., 2025)