A Novel Supplementation Approach to Enhance Host Response to Sublingual Vaccination

SIgA in various pulmonary diseases

Secretory immunoglobulin A (SIgA) is one of the most abundant immunoglobulin subtypes among mucosa, which plays an indispensable role in the first-line protection against invading pathogens and antigens. Therefore, the role of respiratory SIgA in respiratory mucosal immune diseases has attracted more and more attention. Although the role of SIgA in intestinal mucosal immunity has been widely studied, the cell types responsible for SIgA and the interactions between cells are still unclear. Here, we conducted a wide search of relevant studies and sorted out the relationship between SIgA and some pulmonary diseases (COPD, asthma, tuberculosis, idiopathic pulmonary fibrosis, COVID-19, lung cancer), which found SIgA is involved in the pathogenesis and progression of various lung diseases, intending to provide new ideas for the prevention, diagnosis, and treatment of related lung diseases.

A sublingual nanofiber vaccine to prevent urinary tract infections

Urinary tract infections (UTIs) are a major public health problem affecting millions of individuals each year. Recurrent UTIs are managed by long-term antibiotic use, making the alarming rise of antibiotic resistance a substantial threat to future UTI treatment. Extended antibiotic regimens may also have adverse effects on the microbiome. Here, we report the use of a supramolecular vaccine to provide long-term protection against uropathogenic Escherichia coli, which cause 80% of uncomplicated UTIs. We designed mucus-penetrating peptide-polymer nanofibers to enable sublingual (under the tongue) vaccine delivery and elicit antibody responses systemically and in the urogenital tract. In a mouse model of UTI, we demonstrate equivalent efficacy to high-dose oral antibiotics but with significantly less perturbation of the gut microbiome. We also formulate our vaccine as a rapid-dissolving sublingual tablet that raises response in mice and rabbits. Our approach represents a promising alternative to antibiotics for the treatment and prevention of UTIs.

Broad-Spectrum and Gram-Negative-Targeting Antibiotics Differentially Regulate Antibody Isotype Responses to Injected Vaccines

Antibiotics are extensively used worldwide for the treatment of common infections by agents such as E. coli and Salmonella. They also represent the most common cause of alteration of the microbiota in people. We addressed whether broad-spectrum and Gram-negative-targeting antibiotics differentially regulate systemic and mucosal immune responses to vaccines. Antibiotics treatment enhances serum IgG1 responses in mice immunized systemically with a model polyvalent vaccine. This increase was not seen for other IgG subclasses and was dependent on the immunogenicity of vaccine antigens. The broad-spectrum antibiotic cocktail also enhanced serum IgA responses. Interestingly, both the broad spectrum and the antibiotic targeting Gram-negative bacteria enhanced the number of IgA antibody secreting cells in the intestinal lamina propria. This effect was unlikely to be due to an increase in cells expressing gut-homing receptors (i.e., CCR9 and α₄β₇) in peripheral tissues. On the other hand, the microbiome in mice treated with antibiotics was characterized by an overall reduction of the number of firmicutes. Furthermore, Bacteroidetes were increased by either treatment, and Proteobacteria were increased by the broad-spectrum antibiotics cocktail. Thus, immunoglobulin isotype and subclass responses are differentially regulated by oral antibiotics treatment and the gut microbiota shapes mucosal antibody responses after systemic immunization.

Inhibition of elastase enhances the adjuvanticity of alum and promotes anti-SARS-CoV-2 systemic and mucosal immunity

We report that suppression of the serine protease elastase reshapes innate responses induced by injected vaccines containing alum adjuvant. This reprogramming improves the induction of protective antibodies in the bloodstream and stimulates innate signals, which support the development of antibody responses in mucosal tissues. Our findings identify elastase as the innate regulator that blunts the adjuvant activity of alum. They also demonstrate that vaccination via mucosal routes is not an absolute requirement for antibody responses in mucosal tissues and secretions. Supplementation of an alum-based vaccine containing SARS-CoV-2 spike protein subunit 1 as antigen increased anti–SARS-CoV-2 immunity in the blood and mucosal secretions in mice. Thus, this strategy could help in the development of future protein-based vaccines against SARS-CoV-2.

Alum, used as an adjuvant in injected vaccines, promotes T helper 2 (Th2) and serum antibody (Ab) responses. However, it fails to induce secretory immunoglobulin (Ig) A (SIgA) in mucosal tissues and is poor in inducing Th1 and cell-mediated immunity. Alum stimulates interleukin 1 (IL-1) and the recruitment of myeloid cells, including neutrophils. We investigated whether neutrophil elastase regulates the adjuvanticity of alum, and whether a strategy targeting neutrophil elastase could improve responses to injected vaccines. Mice coadministered a pharmacological inhibitor of elastase, or lacking elastase, developed high-affinity serum IgG and IgA antibodies after immunization with alum-adsorbed protein vaccines, including the spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-Cov-2). These mice also developed broader antigen-specific CD4⁺ T cell responses, including high Th1 and T follicular helper (Tfh) responses. Interestingly, in the absence of elastase activity, mucosal SIgA responses were induced after systemic immunization with alum as adjuvant. Importantly, lack or suppression of elastase activity enhanced the magnitude of anti–SARS-CoV-2 spike subunit 1 (S1) antibodies, and these antibodies reacted with the same epitopes of spike 1 protein as sera from COVID-19 patients. Therefore, suppression of neutrophil elastase could represent an attractive strategy for improving the efficacy of alum-based injected vaccines for the induction of broad immunity, including mucosal immunity.

Is the oral microbiome a source to enhance mucosal immunity against infectious diseases?

Mucosal tissues act as a barrier throughout the oral, nasopharyngeal, lung, and intestinal systems, offering first-line protection against potential pathogens. Conventionally, vaccines are applied parenterally to induce serotype-dependent humoral response but fail to drive adequate mucosal immune protection for viral infections such as influenza, HIV, and coronaviruses. Oral mucosa, however, provides a vast immune repertoire against specific microbial pathogens and yet is shaped by an ever-present microbiome community that has co-evolved with the host over thousands of years. Adjuvants targeting mucosal T-cells abundant in oral tissues can promote soluble-IgA (sIgA)-specific protection to confer increased vaccine efficacy. Th17 cells, for example, are at the center of cell-mediated immunity and evidence demonstrates that protection against heterologous pathogen serotypes is achieved with components from the oral microbiome. At the point of entry where pathogens are first encountered, typically the oral or nasal cavity, the mucosal surfaces are layered with bacterial cohabitants that continually shape the host immune profile. Constituents of the oral microbiome including their lipids, outer membrane vesicles, and specific proteins, have been found to modulate the Th17 response in the oral mucosa, playing important roles in vaccine and adjuvant designs. Currently, there are no approved adjuvants for the induction of Th17 protection, and it is critical that this research is included in the preparedness for the current and future pandemics. Here, we discuss the potential of oral commensals, and molecules derived thereof, to induce Th17 activity and provide safer and more predictable options in adjuvant engineering to prevent emerging infectious diseases.

Bioengineering of an elastase inhibitor from Caesalpinia echinata (Brazil wood) seeds

Protease inhibitors have been widely used in several therapeutic applications such as in the treatment of bleeding disorders, hypertension, cancer and pulmonary diseases. In a previous work, we demonstrated that a Kunitz-type serine protease inhibitor isolated from the seeds of Caesalpinia echinata (CeEI) exhibits pharmacological potential in lung inflammatory diseases in which neutrophil elastase plays a crucial role. However, an important challenge in the use of natural products is to ensure a commercially viable production. In this work, we report the cloning, expression and purification of two recombinant CeEI isoinhibitors with 700 base pairs encoding two proteins with 181 amino acid residues (rCeEI-4 and rCeEI-5). After the expression, each yielding 22 mg/L of active protein, both isoinhibitors presented a molecular mass of about 23.0 kDa, evaluated by SDS-PAGE. The inhibition constants for human neutrophil elastase (HNE) were 0.67 nM (rCeEI-4) and 0.57 nM (rCeEI-5), i.e., similar to the native inhibitor (1.90 nM). Furthermore, rCeEI-4 was used as a template to design smaller functional peptides flanking the inhibitor reactive site: rCeEI-36, delimited between the amino acid residues N³⁶ and S⁸⁸ containing a disulfide bond in the reactive-site loop, and rCeEI-46, delimited between S⁴⁶ and L⁷⁵ without the disulfide bond. The yields were 18 mg/L (rCeEI-36) and 12 mg/L (rCeEI-46). Both peptides inhibit HNE in the nanomolar range (K_i 0.30 ± 0.01 and 8.80 ± 0.23, respectively). Considering their size and the inhibitory efficiency, these peptides may be considered in strategies for the development of drugs targeting pulmonary disorders where elastase is involved.