Search

Introduction: Cotton rats are a suitable model for the study of influenza disease symptoms and responses to influenza vaccination. We have previously shown that two immunizations with 15 µg whole inactivated virus (WIV) influenza vaccine could completely protect animals from infection with the H1N1pdm09 virus. Methods: To further explore the cotton rat model, we here investigated the protective potential of a single intramuscular immunization and of prime/boost intramuscular immunizations with a low amount of antigen. Results: A single intramuscular immunization with doses more than or equal to 0.5 µg WIV reliably evoked antibody responses and doses more than or equal to 1 µg protected the animals from virus replication in the lungs and from severe weight loss. However, clinical symptoms like an increased respiration rate were still apparent. Administration of a booster dose significantly increased the humoral immune responses but did not or only moderately improved protection from clinical symptoms. Conclusion: Our data suggest that complete and partial protection by influenza vaccines can be mimicked in cotton rats by using specific vaccination regimens.

Highlights • Entry inhibitors might overcome the limitation of viral mutation. • Antiviral research benefits from a broad-spectrum approach. • Sialic acids can serve as a platform to create broad-spectrum antiviral drugs. • Sialic-acid-targeting drugs such as DAS-181 are promising antiviral strategies. • Multivalency is crucial when designing sialic-acid-based receptor analogues., 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.

Influenza is one of the most widespread viral infections worldwide and represents a major public health problem. The risk that one of the next pandemics is caused by an influenza strain is very high. It is very important to develop broad-spectrum influenza antivirals to be ready for any possible vaccine shortcomings. Anti-influenza drugs are available but they are far from ideal. Arguably, an ideal antiviral should target conserved viral domains and be virucidal, i.e. irreversibly inhibit viral infectivity. Here, we describe a new class of broad-spectrum anti-influenza macromolecules that meets these criteria and displays exceedingly low toxicity. These compounds are based on a cyclodextrin core modified on its primary face with long hydrophobic linkers terminated in 6’sialyl-N-acetyllactosamine (6’SLN) or 3’SLN. SLN enables nanomolar inhibition of the viruses while the hydrophobic linkers confer irreversibility to the inhibition. The combination of these two properties allows for efficacy in vitro against several human or avian influenza strains, as well as against a 2009 pandemic influenza strain ex vivo. Importantly, we show that, in mice, the compounds provide therapeutic efficacy when administered 24h post-infection allowing 90% survival as opposed to no survival for the placebo and oseltamivir..

Most influenza vaccines are administered via injection, which is considered as user-unfriendly. Vaccination via oral cavity using an orodispersible film (ODF) might be a promising alternative. To maintain the antigenicity of the vaccine during preparation and subsequent storage of these ODFs, sugars such as trehalose and pullulan can be employed as stabilizing excipients for the antigens. In this study, first, &beta, galactosidase was used as a model antigen. Solutions containing &beta, galactosidase and sugar (trehalose or trehalose/pullulan blends) were pipetted onto plain ODFs and then either air- or vacuum-dried. Subsequently, sugar ratios yielding the highest &beta, galactosidase stability were used to prepare ODFs containing H5N1 whole inactivated influenza virus vaccine (WIV). The stability of the H5N1 hemagglutinin was assessed by measuring its hemagglutination activity. Overall, various compositions of trehalose and pullulan successfully stabilized &beta, galactosidase and WIV in ODFs. WIV incorporated in ODFs showed excellent stability even at challenging storage conditions (60 &deg, C/0% relative humidity or 30 &deg, C/56% relative humidity) for 4 weeks. Except for sugars, the polymeric component of ODFs, i.e., hypromellose, possibly improved stability of WIV as well. In conclusion, ODFs may be suitable for delivering of WIV to the oral cavity and can possibly serve as an alternative for injections.

Administration of influenza vaccines to the lungs could be an attractive alternative to conventional parenteral administration. In this study, we investigated the deposition site of pulmonary delivered liquid and powder influenza vaccine formulations and its relation to their immunogenicity and protective efficacy. In vivo deposition studies in cotton rats revealed that, the powder formulation was mainly deposited in the trachea (similar to 65%) whereas the liquid was homogenously distributed throughout the lungs (similar to 96%). In addition, only 60% of the antigen in the powder formulation was deposited in the respiratory tract with respect to the liquid formulation. Immunogenicity studies showed that pulmonary delivered liquid and powder influenza formulations induced robust systemic and mucosal immune responses (significantly higher by liquids than by powders). When challenged with a clinical isolate of homologous H1N1pdm virus, all animals pulmonary administered with placebo had detectable virus in their lungs one day post challenge. In contrast, none of the vaccinated animals had detectable lung virus titers, except for two out of eight animals from the powder immunized group. Also, pulmonary vaccinated animals showed no or little signs of infection like increase in breathing frequency or weight loss upon challenge as compared to animals from the negative control group. In conclusion, immune responses induced by liquid formulation were significantly higher than responses induced by powder formulation, but the overall protective efficacy of both formulations was comparable. Thus, pulmonary immunization is capable of inducing protective immunity and the site of antigen deposition seems to be of minor relevance in inducing protection.

Adjuvanted whole inactivated virus (WIV) influenza vaccines show promise as broadly protective influenza vaccine candidates. Using WIV as basis we assessed the relative efficacy of different adjuvants by carrying out a head-to-head comparison of the liposome-based adjuvants CAF01 and CAF09 and the protein-based adjuvants CTA1-DD and CTA1-3M2e-DD and evaluated whether one or more of the adjuvants could induce broadly protective immunity. Mice were immunized with WIV prepared from A/Puerto Rico/8/34 (H1N1) virus intramuscularly with or without CAF01 or intranasally with or without CAF09, CTA1-DD, or CTA1-3M2e-DD, followed by challenge with homologous, heterologous or heterosubtypic virus. In general, intranasal immunizations were significantly more effective than intramuscular immunizations in inducing virus-specific serum-IgG, mucosal-IgA, and splenic IFNγ-producing CD4 T cells. Intranasal immunizations with adjuvanted vaccines afforded strong cross-protection with milder clinical symptoms and better control of virus load in lungs. Mechanistic studies indicated that non-neutralizing IgG antibodies and CD4 T cells were responsible for the improved cross-protection while IgA antibodies were dispensable. The role of CD4 T cells was particularly pronounced for CTA1-3M2e-DD adjuvanted vaccine as evidenced by CD4 T cell-dependent reduction of lung virus titers and clinical symptoms. Thus, intranasally administered WIV in combination with effective mucosal adjuvants appears to be a promising broadly protective influenza vaccine candidate.

BACKGROUND: Induction of CD8+ cytotoxic T cells (CTLs) to conserved internal influenza antigens, such as nucleoprotein (NP), is a promising strategy for the development of cross-protective influenza vaccines. However, influenza NP protein alone cannot induce CTL immunity due to its low capacity to activate antigen-presenting cells (APCs) and get access to the MHC class I antigen processing pathway.METHODS: To facilitate the generation of NP-specific CTL immunity we developed a novel influenza vaccine consisting of virosomes with the Toll-like receptor 4 (TLR4) ligand monophosphoryl lipid A (MPLA) and the metal-ion-chelating lipid DOGS-NTA-Ni incorporated in the membrane.RESULTS: In vitro, virosomes with incorporated MPLA induced stronger activation of APCs than unadjuvanted virosomes. Virosomes modified with DOGS-NTA-Ni showed high conjugation efficacy for his-tagged proteins and facilitated efficient uptake of conjugated proteins by APCs. Immunization of mice with MPLA-adjuvanted virosomes with attached NP resulted in priming of NP-specific CTLs while MPLA-adjuvanted virosomes with admixed NP were inefficient in priming CTLs. Both vaccines induced equally high titers of NP-specific antibodies. When challenged with heterosubtypic influenza virus, mice immunized with virosomes with attached or admixed NP were protected from severe weight loss. Yet, unexpectedly, they showed more weight loss and more severe disease symptoms than mice immunized with MPLA-virosomes without NP.CONCLUSIONS: Taken together, these results indicate that virosomes with conjugated antigen and adjuvant incorporated in the membrane are effective in priming of CTLs and eliciting antigen-specific antibody responses in vivo. However, for protection from influenza infection NP-specific immunity appeared not to be advantageous.

In this study, we have investigated genome-wide occurrence of Histone Acetyltransferases (HATs) in genomes of Mus musculus and Danio rerio on the basis of presence of HAT domain. Our study identified a group of proteins that lacks characteristic features of known HAT families, relatively smaller in size and has no other associated domains. Most of the proteins in this unclassified group are Camello proteins, which are not yet known and classified as functional HATs. Our in vitro and in vivo analysis revealed that Camello family proteins are active HATs and exhibit specificity towards histone H4. Interestingly, Camello proteins are among the first identified HATs showing perinuclear localization. Moreover, Camello proteins are evolutionarily conserved in all chordates and are observed for the first time in cnidarians in phylogeny. Furthermore, knockdown of Camello protein (CMLO3) in zebrafish embryos exhibited defects in axis elongation and head formation. Thus, our study identified a novel family of active HATs that is specific for histone H4 acetylation, exhibits perinuclear localization and is essential for zebrafish development.

Sequential infection with antigenically distinct influenza viruses induces cross-protective immune responses against heterologous virus strains in animal models. Here we investigated whether sequential immunization with antigenically distinct influenza vaccines can also provide cross-protection. To this end, we compared immune responses and protective potential against challenge with A(H1N1)pdm09 in mice infected sequentially with seasonal A(H1N1) virus followed by A(H3N2) virus or immunized sequentially with whole inactivated virus (WIV) or subunit (SU) vaccine derived from these viruses. Sequential infection provided solid cross-protection against A(H1N1)pdm09 infection while sequential vaccination with WIV, though not capable of preventing weight loss upon infection completely, protected the mice from reaching the humane endpoint. In contrast, sequential SU vaccination did not prevent rapid and extensive weight loss. Protection correlated with levels of cross-reactive but non-neutralizing antibodies of the IgG2a subclass, general increase of memory T cells and induction of influenza-specific CD4+ and CD8+ T cells. Adoptive serum transfer experiments revealed that despite lacking neutralizing activity, serum antibodies induced by sequential infection protected mice from weight loss and vigorous virus growth in the lungs upon A(H1N1)pdm09 virus challenge. Antibodies induced by WIV vaccination alleviated symptoms but could not control virus growth in the lung. Depletion of T cells prior to challenge revealed that CD8+ T cells, but not CD4+ T cells, contributed to cross-protection. These results imply that sequential immunization with WIV but not SU derived from antigenically distinct viruses could alleviate the severity of infection caused by a pandemic and may improve protection to unpredictable seasonal infection.

Sequential infection with antigenically distinct influenza viruses induces cross-protective immune responses against heterologous virus strains in animal models. Here we investigated whether sequential immunization with antigenically distinct influenza vaccines can also provide cross-protection. To this end, we compared immune responses and protective potential against challenge with A(H1N1)pdm09 in mice infected sequentially with seasonal A(H1N1) virus followed by A(H3N2) virus or immunized sequentially with whole inactivated virus (WIV) or subunit (SU) vaccine derived from these viruses. Sequential infection provided solid cross-protection against A(H1N1)pdm09 infection while sequential vaccination with WIV, though not capable of preventing weight loss upon infection completely, protected the mice from reaching the humane endpoint. In contrast, sequential SU vaccination did not prevent rapid and extensive weight loss. Protection correlated with levels of cross-reactive but non-neutralizing antibodies of the IgG2a subclass, general increase of memory T cells and induction of influenza-specific CD4+ and CD8+ T cells. Adoptive serum transfer experiments revealed that despite lacking neutralizing activity, serum antibodies induced by sequential infection protected mice from weight loss and vigorous virus growth in the lungs upon A(H1N1)pdm09 virus challenge. Antibodies induced by WIV vaccination alleviated symptoms but could not control virus growth in the lung. Depletion of T cells prior to challenge revealed that CD8+ T cells, but not CD4+ T cells, contributed to cross-protection. These results imply that sequential immunization with WIV but not SU derived from antigenically distinct viruses could alleviate the severity of infection caused by a pandemic and may improve protection to unpredictable seasonal infection.