Inhalation of vaccines and antiviral drugs to fight respiratory virus infections: reasons to prioritize the pulmonary route of administration.

Many of the current pandemic threats are caused by viruses that infect the respiratory tract. Remarkably though, the majority of vaccines and antiviral drugs are administered via alternative routes. In this perspective, we argue that the pulmonary route of administration deserves more attention in the search for novel therapeutic strategies against respiratory virus infections. Firstly, vaccines administered at the viral portal of entry can induce a broader immune response, employing the mucosal arm of the immune system; secondly, direct administration of antiviral drugs at the target site leads to superior bioavailability, enabling lower dosing and reducing the chance of side effects. We further elaborate on why the pulmonary route may induce a superior effect compared to the intranasal route of administration and provide reasons why dry powder formulations for inhalation have significant advantages over standard liquid formulations.

Performance Testing of a Homemade Aerosol Generator for Pulmonary Administration of Dry Powder Formulations to Mice.

A challenge in the development of dry powder formulations for inhalation is the poor reproducibility of their administration to small laboratory animals. The currently used devices for the pulmonary administration of dry powder formulations to small rodents often function sub-optimally as they use the same puff of air for both powder dispersion and aerosol delivery. As a result, either the air volume and flow rate are too low for complete powder deagglomeration or they are too high for effective aerosol delivery to the lungs of the animal. Therefore, novel and better devices are desired. We here present an aerosol generator designed to administer a pre-generated aerosol to the lungs of mice. By mapping the complex relationship between the airflow rate, delivery time and emitted dose, we were able to control the amount of powder being delivered from the aerosol generator. The emitted aerosol had a size range favorable for lung deposition and could be measured reproducibly. Nevertheless, in vivo fluorescent imaging still revealed considerable differences between the mice in terms of the dose deposited and the distribution of powder over the lungs, suggesting that a certain biological variation in lung deposition is inevitable.

Development of an inhalable antiviral powder formulation against respiratory syncytial virus.

Respiratory viruses including the respiratory syncytial virus (RSV) aggravate the global burden of virus-inflicted morbidity and mortality. Entry inhibitors are a promising class of antiviral drugs for combating these viruses, as they can prevent infection at the site of viral entry, i.e., the respiratory tract. Here we used a broad-spectrum entry inhibitor, composed of a ß-cyclodextrin backbone, functionalized with 11-mercapto-1-undecanesulfonate (CD-MUS) that is capable of neutralizing a variety of viruses that employ heparan sulfate proteoglycans (HSPG) to infect host cells. CD-MUS inactivates viral particles irreversibly by binding to viral attachment proteins through a multivalent binding mechanism. In the present study, we show that CD-MUS is well tolerated when administered to the respiratory tract of mice. Based on this, we developed an inhalable spray-dried powder formulation that fits the size requirements for lung deposition and disperses well upon use with the Cyclops dry powder inhaler (DPI). Using an in vitro dose-response assay, we show that the compound retained its activity against RSV after the spray drying process. Our study sets the stage for further in vivo studies, exploring the efficacy of pulmonary administered CD-MUS in animal models of RSV infection.

Inhaled vaccine delivery in the combat against respiratory viruses: a 2021 overview of recent developments and implications for COVID-19.

INTRODUCTION: As underlined by the late 2019 outbreak of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), vaccination remains the cornerstone of global health-care. Although vaccines for SARS-CoV-2 are being developed at a record-breaking pace, the majority of those that are licensed or currently registered in clinical trials are formulated as an injectable product, requiring a tightly regulated cold-chain infrastructure, and primarily inducing systemic immune responses. AREAS COVERED: Here, we shed light on the status of inhaled vaccines against viral pathogens, providing background to the role of the mucosal immune system and elucidating what factors determine an inhalable vaccine's efficacy. We also discuss whether the development of an inhalable powder vaccine formulation against SARS-CoV-2 could be feasible. The review was conducted using relevant studies from PubMed, Web of Science and Google Scholar. EXPERT OPINION: We believe that the scope of vaccine research should be broadened toward inhalable dry powder formulations since dry vaccines bear several advantages. Firstly, their dry state can tremendously increase vaccine stability and shelf-life. Secondly, they can be inhaled using disposable inhalers, omitting the need for trained health-care personnel and, therefore, facilitating mass-vaccination campaigns. Thirdly, inhalable vaccines may provide improved protection since they can induce an IgA-mediated mucosal immune response.

Assessing the Immunomodulatory Effect of Size on the Uptake and Immunogenicity of Influenza- and Hepatitis B Subunit Vaccines In Vitro.

Viral subunit vaccines are a safer and more tolerable alternative to whole inactivated virus vaccines. However, they often come with limited efficacy, necessitating the use of adjuvants. Using free and particle-bound viral antigens, we assessed whether size affects the uptake of those antigens by human monocyte-derived dendritic cells (Mo-DCs) and whether differences in uptake affect their capacity to stimulate cytokine production by T cells. To this end, influenza antigens and hepatitis B surface antigen (HBsAg) were covalently conjugated to polystyrene particles of 500 nm and 3 µm. Cellular uptake of the antigens, either unconjugated or conjugated, and their capacity to stimulate T cells within a population of human peripheral blood mononuclear cells (PBMCs) were measured by flow cytometry. Conjugation of both antigens to particles significantly increased their uptake by Mo-DCs. Moreover, both the 500 nm and 3 µm influenza conjugates induced significantly higher numbers of cytokine-producing CD4+ T cells and induced increased production of the pro-inflammatory cytokines IFNγ and TNFα. In contrast, conjugation of HBsAg to particles did not notably affect the T cell response. In conclusion, conjugation of antigen to 500 nm and 3 µm particles leads to increased antigen uptake by human Mo-DCs, although the capacity of such conjugates to induce T cell stimulation likely depends on the immunological status of the PBMC donor.

Advances in the development of entry inhibitors for sialic-acid-targeting viruses.

Over the past decades, several antiviral drugs have been developed to treat a range of infections. Yet the number of treatable viral infections is still limited, and resistance to current drug regimens is an ever-growing problem. Therefore, additional strategies are needed to provide a rapid cure for infected individuals. An interesting target for antiviral drugs is the process of viral attachment and entry into the cell. Although most viruses use distinct host receptors for attachment to the target cell, some viruses share receptors, of which sialic acids are a common example. This review aims to give an update on entry inhibitors for a range of sialic-acid-targeting viruses and provides insight into the prospects for those with broad-spectrum potential.

Dropping anchor: attachment of peptidylarginine deiminase via A-LPS to secreted outer membrane vesicles of Porphyromonas gingivalis.

The periodontal pathogen Porphyromonas gingivalis has been invoked in the autoimmune disease rheumatoid arthritis (RA). This association relates to the peptidylarginine deiminase of P. gingivalis (PPAD), an enzyme capable of citrullinating human proteins and potentially contributing to loss of tolerance to citrullinated proteins in RA. PPAD is both retained in the outer membrane (OM) of P. gingivalis cells and secreted into the extracellular milieu, where it is detected in a soluble form and in association with outer membrane vesicles (OMVs). Recent studies showed that certain P. gingivalis proteins are retained in the OM through modification with an A-type lipopolysaccharide (A-LPS). Here, we investigated the possible involvement of A-LPS modification in the association of PPAD to the OM and OMVs. The results indicate that the OM- and OMV-associated PPAD is A-LPS-modified. The modified PPAD species is of low abundance in particular clinical isolates of P. gingivalis, which is not due to defects in the overall synthesis of A-LPS-modified proteins but, rather, to particular traits of the respective PPAD proteins. Lastly, we show that OMV association protects the A-LPS-modified PPAD from proteolytic degradation. Altogether, our observations show that A-LPS modification contributes to OM(V) sorting and 'protective secretion' of PPAD.