Chemically Synthesized Alcaligenes Lipid A Shows a Potent and Safe Nasal Vaccine Adjuvant Activity for the Induction of Streptococcus pneumoniae-Specific IgA and Th17 Mediated Protective Immunity

Abstract

Effective and safe vaccine adjuvants are needed to appropriately augment mucosal vaccine effects. Our previous study demonstrated that lipopolysaccharide (LPS) from Peyer’s patch resident Alcaligenes stimulated dendritic cells to promote the production of mucosal immunity-enhancing cytokines (e.g., IL-6 and BAFF), thus enhancing antigen-specific immune responses (including IgA production and Th17 responses) without excessive inflammation. Here, we chemically synthesized Alcaligenes lipid A, the biologically active part of LPS, and examined its efficacy as a nasal vaccine adjuvant for the induction of protectively immunity against Streptococcus pneumoniae infection. Mice were nasally immunized with pneumococcal surface protein A (PspA) as a vaccine antigen for S. pneumoniae, together with Alcaligenes lipid A. Alcaligenes lipid A supported the generation of high levels of PspA-specific IgA and IgG responses through the augmentation of germinal center formation in the nasopharynx-associated lymphoid tissue and cervical lymph nodes (CLNs). Moreover, Alcaligenes lipid A promoted PspA-specific CD4+ Th17 responses in the CLNs and spleen. Furthermore, neutrophils were recruited to infection sites upon nasal infection and synchronized with the antigen-specific T and B cell responses, resulting in the protection against S. pneumoniae infection. Taken together, Alcaligenes lipid A could be applied to the prospective adjuvant to enhance nasal vaccine efficacy by means of augmenting both the innate and acquired arms of mucosal immunity against respiratory bacterial infection.

Lipid A-Mediated Bacterial–Host Chemical Ecology: Synthetic Research of Bacterial Lipid As and Their Development as Adjuvants

“…Only hexa-acylated A. faecalis lipid A 19 (hexa-AfLA) showed a TLR4-dependent immunostimulatory effect comparable to extracted A. faecalis LOS, indicating that hexa-AfLA 19 is the active principle of A. faecalis LOS [ 7 , 60 ]. An in vivo assay with mice confirmed that hexa-AfLA 19 exhibited a similar beneficial adjuvant effect (enhancement of antigen-specific IgA and IgG production) as A. faecalis LOS, without toxicity [ 61 , 62 ]. As a safe nasal vaccine adjuvant, the efficacy of hexa-AfLA 19 has been demonstrated in Streptococcus pneumoniae infection models [ 61 ], indicating that it is an extremely promising adjuvant for vaccines against infectious diseases.…”

Lipopolysaccharide Derived From the Lymphoid-Resident Commensal Bacteria Alcaligenes faecalis Functions as an Effective Nasal Adjuvant to Augment IgA Antibody and Th17 Cell Responses

“…Immunization was performed as described previously ( 17 ). Briefly, on days 1, 7, and 17, the mice were intranasally immunized with 5 μg of ovalbumin (OVA) (Sigma-Aldrich) alone or 10 μg of Alcaligenes LPS or 1 μg of cholera toxin (CT) isolated from Vibrio cholerae (List Biological Laboratories, Campbell, CA, USA) in 15 µL of PBS and administered as 7.5 µL in each nostril of mice without anesthesia.…”

“…Briefly, on days 1, 7, and 17, the mice were intranasally immunized with 5 μg of ovalbumin (OVA) (Sigma-Aldrich) alone or 10 μg of Alcaligenes LPS or 1 μg of cholera toxin (CT) isolated from Vibrio cholerae (List Biological Laboratories, Campbell, CA, USA) in 15 µL of PBS and administered as 7.5 µL in each nostril of mice without anesthesia. One week after the final immunization, nasal wash, bronchoalveolar lavage fluid (BALF), serum, nasal passage, NALT, cervical lymphoid nodes (CLNs), and spleen were collected as previously described ( 17 , 18 ) and used for analysis.…”

“…Immunohistological analysis was performed as described previously ( 17 ). NALT and CLNs were embedded in Tissue-Tek O.C.T.…”

“…T-cell assay was performed as described previously ( 17 ). Cell suspension collected from CLNs and spleen was passed through a 100-μm cell filter (Thermo Fisher Scientific Inc.); then mixed with red blood cell lysis buffer (1.5 M NH 4 Cl, 100 mM KHCO 3 , and 10 mM EDTA-2Na [all Nacalai Tesque, Inc.]) for 1 min at room temperature; the resulting suspension was passed through a 100-μm cell filter (Thermo Fisher Scientific Inc.) again, and the filtrate was retained.…”