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Background The human hookworm, Necator americanus, is a parasite that infects almost half a billion people worldwide. Although treatment is available, vaccination is favorable to combat the spread of this parasite due to its wide distribution and continuous reinfection cycle in endemic communities. Methods We have designed a lipopeptide oral delivery system using a B-cell epitope derived from the aspartic protease Na-APR-1 from N americanus, attached to a T-helper epitope. Lipopeptides were self-assembled into nanoparticles or entrapped in liposomes that were electrostatically coated with alginate and trimethyl chitosan polymer shields. The adjuvant-free vaccine candidates were orally administered to mice and generated a humoral immune response against both peptide antigen, and the parent protein in the hookworm gut. Results The vaccine candidates were evaluated in a rodent hookworm challenge model, resulting in up to 98% and 99% decreases in mean intestinal worm and egg burdens in immunized mice, respectively. Conclusions Lipopeptide survived the gastrointestinal conditions, induced humoral immune responses and drived protection against parasite challenge infection.

Background: Innate immune system plays an important role in pathogen detection and the recognition of vaccines, mainly through pattern recognition receptors (PRRs) that identify pathogen components (danger signals). One of the typically recognised bacterial components are lipids in conjugation with peptides, proteins and saccharides. Lipidic compounds are readily recognised by the immune system, and thus are ideal candidates for peptide- based vaccine delivery. Thus, bacterial or synthetic lipids mixed with, or conjugated to, antigens have shown adjuvant properties. These systems have many advantages over traditional adjuvants, including low toxicity and good efficacy for stimulating mucosal and systemic immune responses. Methods: The most recent literature on the role of lipids in stimulation of immune responses was selected for this review. The vast majority of reviewed papers were published in the last decade. Older but significant findings are also cited. Results: This review focuses on the development of lipopeptide vaccine systems including application of palmitic acid, bacterial lipopeptides, glycolipids and the lipid core peptide and their routes of administration. The use of liposomes as a delivery system that incorporates lipopeptides is discussed. The review also includes a brief description of immune system in relation to vaccinology and discussion on vaccine delivery routes. Conclusion: Lipids and their conjugates are an ideal frontrunner in the development of safe and efficient vaccines for different immunisation routes.

We have successfully demonstrated that submicron-sized polymer-peptide conjugates were capable of inducing strong humoral immune responses after single immunization.

Peptide-based subunit vaccines require an immunostimulant (adjuvant) and/or delivery system to protect the antigenic peptide from degradation and induce the desired immunity. Currently available adjuvants are either too toxic for human use (experimental adjuvants) or they are limited for use in particular vaccines or licensed countries (commercial adjuvants). Therefore, there is an immediate need for novel adjuvants that are both safe and effective. Herein, we assessed the ability of cholic acid (a major bile acid) as a nontoxic, biodegradable, human-derived, potent vaccine delivery system. An antigenic peptide derived from Group A Streptococcus was conjugated to hydrophobic cholic acid via solid phase peptide synthesis to produce lipopeptide that self-assembled into rod-like nanoparticles under aqueous conditions. Following intranasal immunization in mice, this lipopeptide was capable of inducing the production of opsonic epitope-specific antibodies on its own and in liposomal formulation. The cholic acid-based conjugate induced significantly stronger humoral immune responses than cholera toxinbased adjuvant. Thus, we demonstrated, for the first time, capability of the human-derived lipid to act as a built-in immunoadjuvant for vaccines.

We previously reported that reduced GPR183 expression in blood from tuberculosis (TB) patients with diabetes is associated with more severe TB. To further elucidate the role of GPR183 and its oxysterol ligands in the lung, we studied dysglycemic mice infected with M.tuberculosis. We found upregulation of the oxysterol-producing enzymes CH25H and CYP7B1 and increased concentrations of 25-hydroxycholesterol upon Mtb infection in the lungs of mice. This was associated with increased expression of GPR183 indicative of oxysterol-mediated recruitment of GPR183-expressing immune cells to the lung. CYP7B1 was predominantly expressed by macrophages in TB granulomas. CYP7B1 expression was significantly blunted in lungs from dysglycemic animals which coincided with delayed macrophage infiltration. GPR183-deficient mice similarly had reduced macrophage recruitment during early infection. Together we demonstrate a requirement of the GPR183/oxysterol axis for positioning of macrophages to the site of infection and add an explanation to more severe TB in diabetes patients.

RationaleSevere viral respiratory infections are often characterised by extensive myeloid cell infiltration and activation and persistent lung tissue injury. However, the immunological mechanisms driving excessive inflammation in the lung remain poorly understood.ObjectivesTo identify the mechanisms that drive immune cell recruitment in the lung during viral respiratory infections and identify novel drug targets to reduce inflammation and disease severity.MethodsPreclinical murine models of influenza virus and severe acute respiratory coronavirus 2 (SARS-CoV-2) infection.ResultsOxidised cholesterols and the oxysterol-sensing receptor GPR183 were identified as drivers of monocyte-macrophage infiltration to the lung during influenza virus (IAV) and SARS-CoV-2 infection. Both IAV and SARS-CoV-2 infection upregulated the enzymes cholesterol 25-hydroxylase (CH25H) and cytochrome P450 family 7 subfamily member B1 (CYP7B1) in the lung, resulting in local production of the oxidised cholesterols 25-hydroxycholesterol (25-OHC) and 7α,25-dihydroxycholesterol (7α,25-OHC). Loss-of-function mutation of GPR183, or treatment with a GPR183 antagonist, reduced macrophage infiltration and inflammatory cytokine production in the lungs of IAV- or SARS-CoV-2-infected mice. The GPR183 antagonist significantly attenuated the severity of SARS-CoV-2 infection and viral loads. Analysis of single cell RNASeq data on bronchoalveolar lavage samples from healthy controls and COVID-19 patients with moderate and severe disease revealed thatCH25H, CYP7B1andGPR183are significantly upregulated in macrophages during COVID-19.ConclusionThis study demonstrates that oxysterols drive inflammation in the lungviaGPR183 and provides the first preclinical evidence for therapeutic benefit of targeting GPR183 during severe viral respiratory infections.

Oxidized cholesterols, the so-called oxysterols, are widely known to regulate cholesterol homeostasis. However, more recently oxysterols have emerged as important lipid mediators in the response to both bacterial and viral infections. This review summarizes our current knowledge of selected oxysterols and their receptors in the control of intracellular bacterial growth as well as viral entry into the host cell and viral replication. Lastly, we briefly discuss the potential of oxysterols and their receptors as drug targets for infectious and inflammatory diseases.