Chicken dendritic cell-targeting nanobodies mediated improved protective effects against H9N2 influenza virus challenge in a homologous sequential immunization study

Screening optimal DC-targeting peptide to enhance the immune efficacy of recombinant Lactobacillus expressing RHDV VP60

Dendritic cells (DCs) present an ideal target for delivering immunogenic cargo due to their potent antigen-presenting capabilities. This targeting approach holds promise in vaccine development by enhancing the efficiency of antigen recognition and capture by DCs. To identify a high-affinity targeting peptide binding to rabbit DCs, rabbit monocyte-derived DCs (raMoDCs) were isolated and cultured, and a novel peptide, HS (HSLRHDYGYPGH), was identified using a phage-displayed peptide library. Alongside HS, two other DC-targeting peptides, KC1 and MY, previously validated in our laboratory, were employed to construct recombinant Lactgobacillus reuteri fusion-expressed rabbit hemorrhagic disease virus (RHDV) capsid protein VP60. These recombinant Lactobacillus strains were named HS-VP60/L. reuteri, KC1-VP60/L. reuteri, and MY-VP60/L. reuteri. The ability of these recombinant Lactobacillus to bind rabbit DCs was evaluated both in vivo and in vitro. Results demonstrated that the DC-targeting peptide KC1 significantly enhanced the capture efficiency of recombinant Lactobacillus by raMoDCs, promoted DC maturation, and increased cytokine secretion. Furthermore, oral administration of KC1-VP60/L. reuteri effectively induced SIgA and IgG production in rabbits, prolonged rabbit survival post-challenge, and reduced RHDV copies in organs. In summary, the DC-targeting peptide KC1 exhibited robust binding to raMoDCs, and recombinant Lactobacillus expressing KC1-VP60 protein antigens efficiently induced systemic and mucosal immune responses in rabbits, conferring protective efficacy against RHDV. This study offers valuable insights for the development of novel RHDV vaccines.

Cistanche deserticola polysaccharide-functionalized dendritic fibrous nano-silica as oral vaccine adjuvant delivery enhancing both the mucosal and systemic immunity

Oral vaccines are a safe and convenient alternative to injected vaccines and have great potential to prevent major infectious diseases. However, the harsh gastrointestinal (GI) environment, mucus barriers, low immunogenicity, and lack of effective and safe mucosal adjuvants are the major challenges for oral vaccine delivery. In recent years, nanoparticle-based strategies have become attractive for improving oral vaccine delivery. Here, the dendritic fibrous nano-silica (DFNS) grafted with Cistanche deserticola polysaccharide (CDP) nanoparticles (CDP-DFNS) were prepared and investigated how to impact the immune responses. CDP-DFNS facilitated the antigen uptake in mouse bone marrow-derived dendritic cells (BMDCs), and induce the activation of DCs in vitro. Furthermore, in vivo experiments, the result showed that the uptake efficiency by Peyer's patches (PPs) of CDP-DFNS/BSA was the best. And CDP-DFNS/BSA then significantly activated the DCs in lamina propria (LP), and T/B cells in PPs and mesenteric lymph nodes (MLNs). Moreover, the memory T cell responses in later period of vaccination was stronger than other groups. In addition, CDP-DFNS/BSA enhanced BSA-specific antibody IgG, IgA production, and SIgA secretion, was effective at inducing a strong mixed Th1/Th2 response and mucosal antibody responses. These results indicated that CDP-DFNS deserves further consideration as an oral vaccine adjuvant delivery system.

Salmonella enterica serovar Choleraesuis vector outperforms alum as an adjuvant, increasing a cross-protective immune response against Glaesserella parasuis

The adjuvant and/or vector significantly affect a vaccine's efficacy. Although traditional adjuvants such as alum have contributed to vaccine development, deficiencies in the induction of cellular and mucosal immunity have limited their further promotion. Salmonella vectors have unique advantages for establishing cellular and mucosal immunity due to mucosal pathways of invasion and intracellular parasitism. In addition, Salmonella vectors can activate multiple innate immune pathways, thereby promoting adaptive immune responses. In this work, the attenuated Salmonella enterica serovar Choleraesuis (S. Choleraesuis) vector rSC0016 was used to deliver the conserved protective antigen HPS_06257 of Glaesserella parasuis (G. parasuis), generating a novel recombinant strain rSC0016(pS-HPS_06257). The rSC0016(pS-HPS_06257) can express and deliver the HPS_06257 protein to the lymphatic system of the host. In comparison to HPS_06257 adjuvanted with alum, rSC0016(pS-HPS_06257) significantly increased TLR4 and TLR5 activation in mice as well as the levels of proinflammatory cytokines. In addition, rSC0016 promoted a greater degree of maturation in bone marrow-derived dendritic cells (BMDCs) than alum. The specific humoral, mucosal, and cellular immune responses against HPS_06257 in mice immunized with rSC0016(pS-HPS_06257) were significantly higher than those of HPS_06257 adjuvanted with alum. HPS_06257 delivered by the S. Choleraesuis vector induces a Th1-biased Th1/Th2 mixed immune response, while HPS adjuvanted with alum can only induce a Th2-biased immune response. HPS_06257 adjuvanted with alum only causes opsonophagocytic activity (OPA) responses against a homologous strain (G. parasuis serotype 5, GPS5), whereas rSC0016(pS-HPS_06257) could generate cross-OPA responses against a homologous strain and a heterologous strain (G. parasuis serotype 12, GPS12). Ultimately, HPS_06257 adjuvanted with alum protected mice against lethal doses of GPS5 challenge by 60 % but failed to protect mice against lethal doses of GPS12. In contrast, mice immunized with rSC0016(pS-HPS_06257) had 100 % or 80 % survival when challenged with lethal doses of GPS5 or GPS12, respectively. Altogether, the S. Choleraesuis vector rSC0016 could potentially generate an improved innate immune response and an improved adaptive immunological response compared to the traditional alum adjuvant, offering a novel concept for the development of a universal G. parasuis vaccine.