Changing perspective on immunization against influenza

Multiple Neuraminidase Containing Influenza Virus-Like Particle Vaccines Protect Mice from Avian and Human Influenza Virus Infection

Avian influenza virus remains a threat for humans, and vaccines preventing both avian and human influenza virus infections are needed. Since virus-like particles (VLPs) expressing single neuraminidase (NA) subtype elicited limited heterosubtypic protection, VLPs expressing multiple NA subtypes would enhance the extent of heterosubtypic immunity. Here, we generated avian influenza VLP vaccines displaying H5 hemagglutinin (HA) antigen with or without avian NA subtypes (N1, N6, N8) in different combinations. BALB/c mice were intramuscularly immunized with the VLPs to evaluate the resulting homologous and heterosubtypic immunity upon challenge infections with the avian and human influenza viruses (A/H5N1, A/H3N2, A/H1N1). VLPs expressing H5 alone conferred homologous protection but not heterosubtypic protection, whereas VLPs co-expressing H5 and NA subtypes elicited both homologous and heterosubtypic protection against human influenza viruses in mice. We observed that VLP induced neuraminidase inhibitory activities (NAI), virus-neutralizing activity, and virus-specific antibody (IgG, IgA) responses were strongly correlated with the number of different NA subtype expressions on the VLPs. VLPs expressing all 3 NA subtypes resulted in the highest protection, indicated by the lowest lung titer, negligible body weight changes, and survival in immunized mice. These results suggest that expressing multiple neuraminidases in avian HA VLPs is a promising approach for developing a universal influenza A vaccine against avian and human influenza virus infections.

Dendritic Cells Targeting Lactobacillus plantarum Strain NC8 with a Surface-Displayed Single-Chain Variable Fragment of CD11c Induce an Antigen-Specific Protective Cellular Immune Response

Influenza A virus (H1N1) is an acute, highly contagious respiratory virus. The use of lactic acid bacteria (LAB) to deliver mucosal vaccines against influenza virus infection is a research hot spot. In this study, two recombinant Lactobacillus plantarum strains expressing hemagglutinin (HA) alone or coexpressing aCD11c-HA to target HA protein to dendritic cells (DCs) by fusion to an anti-CD11c single-chain antibody (aCD11c) were constructed. The activation of bone marrow dendritic cells (BMDCs) by recombinant strains and the interaction of activated BMDCs and sorted CD4⁺ or CD8⁺ T cells were evaluated through flow cytometry in vitro, and cellular supernatants were assessed by using an enzyme-linked immunosorbent assay kit. The results demonstrated that, compared to the HA strain, the aCD11c-HA strain significantly increased the activation of BMDCs and increased the production of CD4⁺ gamma interferon-positive (IFN-γ⁺) T cells, CD8⁺ IFN-γ⁺ T cells, and IFN-γ in the cell culture supernatant in vitro Consistent with these results, the aCD11c-HA strain clearly increased the activation and maturation of DCs, the HA-specific responses of CD4⁺ IFN-γ⁺ T cells, CD8⁺ IFN-γ⁺ T cells, and CD8⁺ CD107a⁺ T cells, and the proliferation of T cells in the spleen, finally increasing the levels of specific antibodies and neutralizing antibodies in mice. In addition, the protection of immunized mice was observed after viral infection, as evidenced by improved weight loss, survival, and lung pathology. The adoptive transfer of CD8⁺ T cells from the aCD11c-HA mice to NOD/Lt-SCID mice resulted in a certain level of protection after influenza virus infection, highlighting the efficacy of the aCD11c targeting strategy.

B-cell restriction - an alternative piece to the puzzle

Effective vaccination is based on three critical aspects of the B-cell response towards infectious agents: (i) that B-cells can generate specific antibodies towards a vast molecular diversity of antigens; proteins, sugars, DNA and lipids. There seems to be no limit to the ability to raise antibodies to everything. (ii) once stimulated, B-cells can perfect their antibodies through affinity maturation to complement every nook and cranny of the epitope and (iii) that the pathogen remains genetically stable and does not change to any great extent. Thus, antibodies produced against the vaccine and subsequent boosts recognize the viral virulent field isolates in future encounters and effectively knock them out. However, some vaccine targets, such as flu virus and HIV, are extremely genetically dynamic. The rapid genetic drift of these viruses renders them moving targets which assist in their ability to evade immune surveillance. Here we postulate that in the case of hyper-variable pathogens the B-cell response actually might be “too good”. We propose that restricting B-cell activities may prove effective in counteracting the genetic diversity of variant viruses such as flu and HIV. We suggest two levels of “B-cell restriction”: (i) to focus the B-cell response exclusively towards neutralizing epitopes by creating epitope-based immunogens; (ii) to restrict affinity maturation of B-cells to prevent the production of overly optimized exquisitely specific antibodies. Together, these “B-cell restrictions” provide a new modality for vaccine design.

Efficient oral vaccination by bioengineering virus-like particles with protozoan surface proteins

Intestinal and free-living protozoa, such as Giardia lamblia, express a dense coat of variant-specific surface proteins (VSPs) on trophozoites that protects the parasite inside the host’s intestine. Here we show that VSPs not only are resistant to proteolytic digestion and extreme pH and temperatures but also stimulate host innate immune responses in a TLR-4 dependent manner. We show that these properties can be exploited to both protect and adjuvant vaccine antigens for oral administration. Chimeric Virus-like Particles (VLPs) decorated with VSPs and expressing model surface antigens, such as influenza virus hemagglutinin (HA) and neuraminidase (NA), are protected from degradation and activate antigen presenting cells in vitro. Orally administered VSP-pseudotyped VLPs, but not plain VLPs, generate robust immune responses that protect mice from influenza infection and HA-expressing tumors. This versatile vaccine platform has the attributes to meet the ultimate challenge of generating safe, stable and efficient oral vaccines.

Giardia lamblia express a dense coat of variant-specific surface proteins (VSPs) on trophozoites that protects the parasite inside the host´s intestine. Here the authors show that stability and immunomodulatory properties of VSPs can be exploited to both protect and adjuvant vaccine antigens for oral administration.

Secretion of M2e:HBc fusion protein by Lactobacillus casei using Cwh signal peptide

The ability to serve as a delivery vehicle for various interesting biomolecules makes lactic acid bacteria (LAB) very useful in several applications. In the medical field, recombinant LAB expressing pathogenic antigens at different cellular locations have been used to elicit both mucosal and systemic immune responses. Expression–secretion vectors (ESVs) with a signal peptide (SP) are pivotal for protein expression and secretion. In this study, the genome sequence of Lactobacillus casei ATCC334 was explored for new SPs using bioinformatics tools. Three new SPs of the proteins Cwh, SurA and SP6565 were identified and used to construct an ESV based on our Escherichia coli–L. casei shuttle vector, pRCEID-LC13.9. Functional testing of these constructs with the green fluorescence protein (GFP) gene showed that they could secrete the GFP. The construct with CwhSP showed the highest GFP secretion. Consequently, CwhSP was selected to develop an ESV construct carrying a synthetic gene encoding the extracellular domain of the matrix 2 protein fused with the hepatitis B core antigen (M2e:HBc). This ESV was shown to efficiently express and secrete the M2e:HBc fusion protein. The identified SPs and the developed ESVs can be exploited for expression and secretion of homologous and heterologous proteins in L. casei.

The novel Cwh signal peptide selected from the Lactobacillus casei genome by using a bioinformatics approach was successfully used in the expression–secretion vector for heterologous protein secretion.

Immunogenicity and protective efficacy of the norovirus P particle-M2e chimeric vaccine in chickens

The ectodomain of the influenza matrix protein 2 (M2e) is highly conserved across strains and has been shown to be a promising candidate for universal influenza vaccine in the mouse model. In this study, we tested immune response and protective efficacy of a chimeric norovirus P particle containing the avian M2e protein against challenges with three avian influenza (AI) viruses (H5N2, H6N2, H7N2) in chickens. Two-week-old specific pathogen free chickens were vaccinated 3 times with an M2e-P particle (M2e-PP) vaccine via the subcutaneous (SQ) route with oil adjuvant, and transmucosal routes (intranasal, IN; eye drop, ED; microspray, MS) without adjuvant. M2e-PP vaccination via the SQ route induced significant IgG antibody responses which were increased by each booster vaccination. In groups vaccinated via IN, ED or MS, neither IgG nor IgA responses were detected from sera or nasal washes of immunized birds. The M2e-PP vaccination via the SQ route significantly reduced the virus shedding in the trachea and the cloaca for all three challenge viruses. Despite the absence of detectable IgG and IgA responses in birds vaccinated with the M2e-PP via intranasal routes, a similar level of reduction in virus shedding was observed in the IN group compared to the SQ group. Our results supports that the universal vaccine approach using M2e-based vaccine can provide cross-protection against challenge viruses among different HA subtypes although the efficacy of the vaccine should be enhanced further to be practical. Better understanding of the protective immune mechanism will be critical for the development of an M2e-based vaccine in chickens.

Expression and Characterization of Recombinant, Tetrameric and Enzymatically Active Influenza Neuraminidase for the Setup of an Enzyme-Linked Lectin-Based Assay

Developing a universal influenza vaccine that induces broad spectrum and longer-term immunity has become an important potentially achievable target in influenza vaccine research and development. Hemagglutinin (HA) and neuraminidase (NA) are the two major influenza virus antigens. Although antibody responses against influenza virus are mainly directed toward HA, NA is reported to be more genetically stable; hence NA-based vaccines have the potential to be effective for longer time periods. NA-specific immunity has been shown to limit the spread of influenza virus, thus reducing disease symptoms and providing cross-protection against heterosubtypic viruses in mouse challenge experiments.

The production of large quantities of highly pure and stable NA could be beneficial for the development of new antivirals, subunit-based vaccines, and novel diagnostic tools. In this study, recombinant NA (rNA) was produced in mammalian cells at high levels from both swine A/California/07/2009 (H1N1) and avian A/turkey/Turkey/01/2005 (H5N1) influenza viruses. Biochemical, structural, and immunological characterizations revealed that the soluble rNAs produced are tetrameric, enzymatically active and immunogenic, and finally they represent good alternatives to conventionally used sources of NA in the Enzyme-Linked Lectin Assay (ELLA).

An Innovative Pseudotypes-Based Enzyme-Linked Lectin Assay for the Measurement of Functional Anti-Neuraminidase Antibodies

Antibodies (Ab) to neuraminidase (NA) play a role in limiting influenza infection and might help reduce the disease impact. The most widely used serological assay to measure functional anti-NA immune responses is the Enzyme-Linked Lectin Assay (ELLA) which relies on hemagglutinin (HA) mismatched virus reassortants, or detergent treated viruses as the NA source to overcome interference associated with steric hindrance of anti-HA Ab present in sera. The difficulty in producing and handling these reagents, which are not easily adapted for screening large numbers of samples, limits the routine analysis of functional anti-NA Ab in clinical trials. In this study, we produced influenza lentiviral pseudoparticles (PPs) containing only the NA antigen (NA-PPs) with a simple two-plasmid co-transfection system. NA-PPs were characterized and tested as an innovative source of NA in the NA inhibition (NI) assay. Both swine A/California/07/2009 (H1N1) and avian A/turkey/Turkey/01/2005 (H5N1) N1s within NA-PPs retained their sialidase activity and were specifically inhibited by homologous and N1 subtype-specific, heterologous sheep sera. Moreover, A/California/07/2009 N1-PPs were a better source of NA compared to whole live and detergent treated H1N1 viruses in ELLA, likely due to lack of interference by anti-HA Ab, and absence of possible structural modifications caused by treatment with detergent. This innovative assay is safer and applicable to all NAs. Taken together, these results highlight the potential of NA-PPs-based NI assays to be developed as sensitive, flexible, easy to handle and scalable serological tests for routine NA immune response analysis.

A potential protein-based vaccine for influenza H5N1 from the recombinant HA1 domain of avian influenza A/H5N1 expressed in Pichia pastoris

ABSTRACT 

The HA1 genes from influenza A strains A/Puerto Rico/8/1934 H1N1 (A/PR/8/34) and A/Hatay/2004 H5N1 were each cloned in Pichia pastoris vectors in the correct reading frame with the yeast α-factor secretion signal and the C-terminus His-tag, resulting in simple, fast purification of expressed H1HA1 and H5HA1 protein from the culture medium. Mice vaccinated with the purified proteins showed robust T cell, anti-HA1 IgG responses and developed a high antibody response for hemagglutination inhibition (HI) at titer 7.6 log2. Chickens vaccinated with a dose of 200 µg of H5HA1 mixed with either Montanide or Freund's adjuvants gave HI values of up to 7 log2 at the third week comparable with a licensed inactivated H5N1 vaccine.

The relationship between in vivo antiviral activity and pharmacokinetic parameters of peramivir in influenza virus infection model in mice

The purpose of this study was to investigate the relationship between pharmacokinetic (PK) parameters of intravenous (IV) peramivir and in vivo antiviral activity pharmacodynamic (PD) outcomes in a mouse model of influenza virus infection. Peramivir was administrated to mice in three dosing schedules; once, twice and four times after infection of A/WS/33 (H1N1). The survival rate at day 14 after virus infection was employed as the antiviral activity outcome for analysis. The relationship between day 14 survival and PK parameters, including area under the concentration-time curve (AUC), maximum concentration (Cmax) and time that drug concentration exceeds IC95 (T(>IC95)), was estimated using a logistic regression model, and model fitness was evaluated by calculation of the Akaike information criterion (AIC) index. The AIC indices of AUC, Cmax and T(>IC95) were about 114, 151 and 124, respectively. The AIC of AUC and T(>IC95) were smaller than that of Cmax. Therefore, both AUC and T(>IC95) were the PK parameters that correlated best with the antiviral activity of peramivir IV against influenza virus infection in mice.

Universal anti-neuraminidase antibody inhibiting all influenza A subtypes

The only universally conserved sequence amongst all influenza A viral neuraminidase (NA) is located between amino acids 222-230 and plays crucial roles in viral replication. However, it remained unclear as to whether this universal epitope is exposed during the course of infection to allow binding and inhibition by antibodies. Using a monoclonal antibody (MAb) targeting this specific epitope, we demonstrated that all nine subtypes of NA were inhibited in vitro by the MAb. Moreover, the antibody also provided heterosubtypic protection in mice challenged with lethal doses of mouse-adapted H1N1 and H3N2, which represent group I and II viruses, respectively. Furthermore, we report amino acid residues I222 and E227, located in close proximity to the active site, are indispensable for inhibition by this antibody. This unique, highly-conserved linear sequence in viral NA could be an attractive immunological target for protection against diverse strains of influenza viruses.

Inhibitors of influenza viruses replication: a patent evaluation (WO2013019828)

A series of compounds incorporating two aromatic heterocycles were prepared as inhibitors of influenza virus replication in the patent. Some of them presented potent activity against influenza virus in Madin-Darby canine kidney (MDCK) cells and in influenza therapeutic mouse model. These compounds in the patent were also defined to be pharmaceutically acceptable salts and pharmaceutical compositions that were claimed to be useful for treating influenza. In view of the threat of influenza pandemic, it is necessary to discover new anti-influenza drugs. Although there is a lack of essential biological data and the molecular mechanisms are not clear, these compounds with potent antiviral activity stand for a new type of anti-influenza agents and deserve further studies.

Virus-like particles as universal influenza vaccines

Current influenza vaccines are primarily targeted to induce immunity to the influenza virus strain-specific hemagglutinin antigen and are not effective in controlling outbreaks of new pandemic viruses. An approach for developing universal vaccines is to present highly conserved antigenic epitopes in an immunogenic conformation such as virus-like particles (VLPs) together with an adjuvant to enhance the vaccine immunogenicity. In this review, the authors focus on conserved antigenic targets and molecular adjuvants that were presented in VLPs. Conserved antigenic targets that include the hemagglutinin stalk domain, the external domain of influenza M2 and neuraminidase are discussed in addition to molecular adjuvants that are engineered to be incorporated into VLPs in a membrane-anchored form.

Targeting the skin for microneedle delivery of influenza vaccine

Influenza infection represents a major socioeconomic burden worldwide. Skin represents a new target that has gained much attention in recent years for delivery of influenza vaccine as an alternative to the conventional intramuscular route of immunization. In this review we describe different microneedle vaccination approaches used in vivo, including metal and dissolving microneedle patches that have demonstrated promising results. Additionally we analyze the immunological basis for microneedle skin immunization and targeting of the skin's dense population of antigen presenting cells, their role, characterization, and function. Additionally we analyze the importance of inflammatory signaling in the skin after microneedle delivery.

Methamphetamine reduces human influenza A virus replication

Methamphetamine (meth) is a highly addictive psychostimulant that is among the most widely abused illicit drugs, with an estimated over 35 million users in the world. Several lines of evidence suggest that chronic meth abuse is a major factor for increased risk of infections with human immunodeficiency virus and possibly other pathogens, due to its immunosuppressive property. Influenza A virus infections frequently cause epidemics and pandemics of respiratory diseases among human populations. However, little is known about whether meth has the ability to enhance influenza A virus replication, thus increasing severity of influenza illness in meth abusers. Herein, we investigated the effects of meth on influenza A virus replication in human lung epithelial A549 cells. The cells were exposed to meth and infected with human influenza A/WSN/33 (H1N1) virus. The viral progenies were titrated by plaque assays, and the expression of viral proteins and cellular proteins involved in interferon responses was examined by Western blotting and immunofluorescence staining. We report the first evidence that meth significantly reduces, rather than increases, virus propagation and the susceptibility to influenza infection in the human lung epithelial cell line, consistent with a decrease in viral protein synthesis. These effects were apparently not caused by meth’s effects on enhancing virus-induced interferon responses in the host cells, reducing viral biological activities, or reducing cell viability. Our results suggest that meth might not be a great risk factor for influenza A virus infection among meth abusers. Although the underlying mechanism responsible for the action of meth on attenuating virus replication requires further investigation, these findings prompt the study to examine whether other structurally similar compounds could be used as anti-influenza agents.

Influenza infection and therapy: a systems approach

Seasonal flu affects 5–20% of the human population each year. Although mortality rates are typically <0.1% and the pandemic 2009 H1N1 influenza strain has been well contained by vaccination and strict hygiene, particularly virulent pandemic forms have emerged three times in the last century, resulting in millions of deaths. Current vaccine and therapeutic strategies are limited by the ability of the virus to generate variants that evade vaccine-induced immune responses and resist the therapeutic effects of antiviral drugs. Host genetic variations affect immune responses and may induce adverse effects during drug treatment or against vaccines. To develop new, first-in-class therapeutics, new antiviral targets and new chemical entities must be identified in the context of the immunogenomic repertoire of the patient. Since influenza and so many other viruses need to escape innate immunity to become pathogenic, the viral proteins responsible for this, as well as the host cell molecular pathways that lead to the antiviral response, are an excellent potential source of new therapeutic targets within a systems approach against influenza infections.

Engineering influenza viral vectors

The influenza virus is a respiratory pathogen with a negative-sense, segmented RNA genome. Construction of recombinant influenza viruses in the laboratory was reported starting in the 1980s. Within a short period of time, pioneer researchers had devised methods that made it possible to construct influenza viral vectors from cDNA plasmid systems. Herein, we discuss the evolution of influenza virus reverse genetics, from helper virus-dependent systems, to helper virus-independent 17-plasmid systems, and all the way to 3- and 1- plasmid systems. Successes in the modification of different gene segments for various applications, including vaccine and gene therapies are highlighted.

Recent advances in neuraminidase inhibitor development as anti-influenza drugs

The recent emergence of the highly pathogenic H5N1 subtype of avian influenza virus (AIV) and of the new type of human influenza A (H1N1) have emphasized the need for the development of effective anti-influenza drugs. Presently, neuraminidase (NA) inhibitors are widely used in the treatment and prophylaxis of human influenza virus infection, and tremendous efforts have been made to develop more potent NA inhibitors to combat resistance and new influenza viruses. In this review, we discuss the structural characteristics of NA catalytic domains and the recent developments of new NA inhibitors using structure-based drug design strategies. These drugs include analogues of zanamivir, analogues of oseltamivir, analogues of peramivir, and analogues of aromatic carboxylic acid and present promising options for therapeutics or leads for further development of NA inhibitors that may be useful in the event of a future influenza pandemic.

Randomized clinical trial of immunogenicity and safety of a recombinant H1N1/2009 pandemic influenza vaccine containing Advax™ polysaccharide adjuvant

BACKGROUND

Timely vaccine supply is critical during influenza pandemics. A recombinant hemagglutinin (rHA)-based vaccine could overcome production hurdles of egg-based vaccines but has never previously been tested in a real-life pandemic setting. The primary aim was to determine the efficacy of a recombinant pandemic vaccine and whether its immunogenicity could be enhanced by a novel polysaccharide adjuvant (Advax™).

METHODS

281 adults aged 18-70 years were recruited in a randomized, subject and observer blinded, parallel-group study of rHA H1N1/2009 vaccine with or without adjuvant. Immunizations were at 0 and 3 weeks with rHA 3, 11 or 45 μg. Serology and safety was followed for 6 months.

RESULTS

At baseline, only 9.1% of subjects (95% CI: 6.0-13.2) had seroprotective H1N1/2009 titers. Seroconversion rates varied by rHA dose, presence of adjuvant, subject age and number of immunizations. Eighty percent (95% CI: 52-96) of 18-49 year olds who received rHA 45 μg with adjuvant were seroprotected at week 3, representing a 11.1-fold increase in antibody titers from baseline. Advax™ adjuvant increased seroprotection rates by 1.9 times after the first, and 2.5 times after the second, immunization when compared to rHA alone. Seroprotection was sustained at 26 weeks and the vaccine was well tolerated with no safety issues.

CONCLUSIONS

The study confirmed the ability to design, manufacture, and release a recombinant vaccine within a short time from the start of an actual influenza pandemic. Advax™ adjuvant significantly enhanced rHA immunogenicity.

Influenza M1 VLPs containing neuraminidase induce heterosubtypic cross-protection

Influenza virus like particles (VLPs) containing hemagglutinin were previously demonstrated to induce protection against the homologous strains. However, little information is available on the protective role of neuraminidase (NA), the second major glycoprotein. In this study, we developed VLPs (NA VLPs) containing NA and M1 derived from A/PR/8/34 (H1N1) influenza virus, and investigated their ability to induce protective immunity. Intranasal immunization with NA VLPs induced serum antibody responses to H1N1 and H3N2 influenza A viruses as well as significant neuraminidase inhibition activity. Importantly, mice immunized with NA VLPs were 100% protected against lethal infection by the homologous A/PR/8/34 (H1N1) as well as heterosubtypic A/Philippines/82 (H3N2) virus, although body weight loss was observed after lethal challenge with heterosubtypic H3N2 virus. The present study therefore provides evidence that influenza VLPs containing M1 and NA are capable of inducing immunity to homologous as well as antigenically distinct influenza A virus strains.

Developments of subunit and VLP vaccines against influenza A virus

Influenza virus is a continuous and severe global threat to mankind. The continuously re-emerging disease gives rise to thousands of deaths and enormous economic losses each year, which emphasizes the urgency and necessity to develop high-quality influenza vaccines in a safer, more efficient and economic way. The influenza subunit and VLP vaccines, taking the advantage of recombinant DNA technologies and expression system platforms, can be produced in such an ideal way. This review summarized the recent advancements in the research and development of influenza subunit and VLP vaccines based on the recombinant expression of hemagglutinin antigen (HA), neuraminidase antigen (NA), Matrix 2 protein (M2) and nucleocapsid protein (NP). It would help to get insight into the current stage of influenza vaccines, and suggest the future design and development of novel influenza vaccines.

Influenza viral neuraminidase: the forgotten antigen

Influenza is the most common cause of vaccine-preventable morbidity and mortality despite the availability of the conventional trivalent inactivated vaccine and the live-attenuated influenza vaccine. These vaccines induce an immunity dominated by the response to hemagglutinin (HA) and are most effective when there is sufficient antigenic relatedness between the vaccine strain and the HA of the circulating wild-type virus. Vaccine strategies against influenza may benefit from inclusion of other viral antigens in addition to HA. Epidemiologic evidence and studies in animals and humans indicate that anti-neuraminidase (NA) immunity will provide protection against severe illness or death in the event of a significant antigenic change in the HA component of the vaccine. However, there is little NA immunity induced by trivalent inactivated vaccine and live-attenuated influenza vaccine. The quantity of NA in influenza vaccines is not standardized and varies significantly among manufacturers, production lots and tested strains. The activity and stability of the NA enzyme is influenced by concentration of divalent cations. If immunity against NA is desirable, a better understanding of how the enzymatic properties affect the immunogenicity is needed.

Correlates of vaccine protection from influenza and its complications

Despite use of influenza vaccines for more than 65 y, influenza and its complications are a major cause of morbidity and mortality worldwide. Most deaths during influenza virus infections are due to underlying co-morbidities or secondary bacterial pneumonia. The measures of immune response currently used for licensure of influenza vaccines are relevant mainly for protection from viral infection in healthy adults. Development of new or improved influenza vaccines will require a definition of novel, and specific correlates of protection. These correlates should associate immune responses with outcomes that are relevant to specific risk groups, such as asthma exacerbation, hospitalization or disruptions to care or daily activities. Assessment of vaccine effectiveness for both viral and bacterial vaccines should include measures of impact on secondary bacterial pneumonia.

Stability of seasonal influenza vaccines investigated by spectroscopy and microscopy methods

The stability of different seasonal influenza vaccines was investigated by spectroscopy and microscopy methods before and after the following stress-conditions: (i) 2 and 4 weeks storage at 25°C, (ii) 1 day storage at 37°C and (iii) one freeze-thaw cycle. The subunit vaccine Influvac (Solvay Pharma) and the split vaccine Mutagrip (Sanofi Pasteur) were affected by all stresses. The split vaccine Fluarix (GlaxoSmithKline) was affected only by storage at 25°C. The virosomal vaccine Inflexal V (Berna Biotech) was stable after the temperature stresses but aggregated after one freeze-thaw cycle. This study provides new insights into commercial vaccines of low antigen concentration and highlights the importance of using multiple techniques to assess vaccine stability.

Expression, purification and characterization of low-glycosylation influenza neuraminidase in α-1,6-mannosyltransferase defective Pichia pastoris

Influenza A viruses expose two major surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA). Although N-glycosylation is essential for many glycoproteins, the glycoproteins expressed in yeast are sometimes hyper-glycosylated, which maybe a primary hindrance to the exploitation of therapeutic glycoprotein production because glycoproteins decorated with yeast-specific glycans are immunogenic and show poor pharmacokinetic properties in humans. To elucidate the NA with different glycosylation in interaction with immunogenicity, here we reported the heterologous expression of influenza NA glycoprotein derived from influenza virus A/newCaledonia/20/99(H1N1) in wide-type Pichia pastoris, α-1,6-mannosyltransferase (och1)-defective P. pastoris and Escherichia coli. We also assessed the immunogenicity of hyper-glycosylated NA expressed in the wide-type, low-glycosylated NA expressed in och1-defective P. pastoris strain and non-glycosylated NA produced in E. coli. Recombinant NA was expressed in wide-type P. pastoris as a 59-97 above kDa glycoprotein, 52-57 kDa in the och1 defective strain, and as a 45 kDa non-glycoprotein in E. coli. The antibody titers of Balb/c mice were tested after the mice were immunized three times with 0.2, 1, or 3 μg purified recombinant NA. Our results demonstrated that after the second immunization, the antibody titer elicited with 1 μg low-glycosylated NA was 1:5,500, while it was 1:10 and 1:13 when elicited by 1 μg hyper-glycosylated and non-glycosylated NA. In the 0.2 μg dose groups, a high antibody titer (1:4,900) was only found after third immunization by low-glycosylated NA, respectively. These results suggest that low-glycosylation in och1-defective P. pastoris enhances the immunogenicity of recombinant NA and elicits similar antibody titers with less antigen when compared with hyper- and non-glycosylated NA. Thus, och1-defective P. pastoris may be a better yeast expression system for production of glycoproteins to research immunogenic characterization.

Immunization with 1976 swine H1N1- or 2009 pandemic H1N1-inactivated vaccines protects mice from a lethal 1918 influenza infection

BACKGROUND

Zoonotic infections with H1N1 influenza viruses that evolved initially from the 1918 virus (1918) and adapted to swine threatened a pandemic in 1976 (1976 swH1N1) and a novel reassortant H1N1 virus caused a pandemic in 2009-2010 (2009 pH1N1). Epidemiological and laboratory animal studies show that protection from severe 2009 pH1N1 infection is conferred by vaccination or prior infection with 1976 swH1N1 or 1918.

OBJECTIVES

Our aim was to demonstrate cross-protection by immunization with 2009 pH1N1 or 1976 swH1N1 vaccines following a lethal challenge with 1918. Further, the mechanisms of cross-protective antibody responses were evaluated.

METHODS

Mice were immunized with 1976 swH1N1, 2009 pH1N1, 2009 seasonal trivalent, or 1918 vaccines and challenged with 1918. Cross-reactive antibody responses were assessed and protection monitored by survival, weight loss, and pathology in mice.

RESULTS AND CONCLUSIONS

Vaccination with the 1976 swH1N1 or 2009 pH1N1 vaccines protected mice from a lethal challenge with 1918, and these mice lost no weight and had significantly reduced viral load and pathology in the lungs. Protection was likely due to cross-reactive antibodies detected by microneutralization assay. Our data suggest that the general population may be protected from a future 1918-like pandemic because of prior infection or immunization with 1976 swH1N1 or 2009 pH1N1. Also, influenza protection studies generally focus on cross-reactive hemagglutination-inhibiting antibodies; while hemagglutinin is the primary surface antigen, this fails to account for other influenza viral antigens. Neutralizing antibody may be a better correlate of human protection against pathogenic influenza strains and should be considered for vaccine efficacy.

The memory phase of the CD4 T-cell response to influenza virus infection maintains its diverse antigen specificity

A major gap in our understanding of the immune response to pathogens and vaccines is how closely the antigen specificity in the memory phase mimics repertoire that is rapidly expanded upon priming. Understanding the diversity of the CD4 T-cell memory compartment after a primary response to pathogens is hampered by the technical challenges of epitope discovery and suitable models to study primary immune responses. Recently, we have used overlapping synthetic peptides to empirically map most of the specificities present in the primary response to live influenza infection. We found that the CD4 T-cell response can be exceptionally diverse, depending on the allele(s) of MHC class II molecules expressed. In the current study, using a mouse model of primary influenza infection and peptide-specific cytokine EliSpots, we have asked how this broad CD4 T-cell immunodominance hierarchy changes as the immune response contracts and memory is established. Our studies revealed that, for the most part, diversity is maintained, and most specificities, including those for relatively minor epitopes, are preserved in the memory CD4 T-cell compartment. A modest, but reproducible shift in specificity toward haemagglutinin-derived epitopes was observed, raising the possibility that protein or peptide persistence might play a role in the evolution of the memory phase of the CD4 T-cell response.

Influenza A viruses: why focusing on M2e-based universal vaccines

The threat of highly virulent avian influenza, such as H5N1 and swine-origin H1N1 influenza viruses, bring out an urgent need to develop a universal influenza vaccine, which may provide cross-protection against different strain of influenza A viruses. The extra-domain of influenza M2 protein (M2e), which is almost completely conserved among all subtypes of influenza A viruses, is considered as a promising candidate target for the development of a broad-spectrum recombinant influenza A vaccine. The results of several preclinical studies with M2e protein, with or without carriers, have already proved the successful protection of M2e-based vaccinated animal model against lethal challenge of heterologous and homologous influenza A viruses. Recently, the results of Phase I/II clinical trail studies with M2e-based vaccines have raised hopes for considering these vaccines against seasonal and pandemic influenza A strains. Hence, it is expected that more and more effective and safe universal influenza vaccines based on M2e will be developed for prevention of seasonal and pandemic influenza in the near future.

Enhanced immunogenicity of stabilized trimeric soluble influenza hemagglutinin

BACKGROUND

The recent swine-origin H1N1 pandemic illustrates the need to develop improved procedures for rapid production of influenza vaccines. One alternative to the current egg-based manufacture of influenza vaccine is to produce a hemagglutinin (HA) subunit vaccine using a recombinant expression system with the potential for high protein yields, ease of cloning new antigenic variants, and an established safety record in humans.

METHODOLOGY/PRINCIPAL FINDINGS

We generated a soluble HA (sHA), derived from the H3N2 virus A/Aichi/2/68, modified at the C-terminus with a GCN4pII trimerization repeat to stabilize the native trimeric structure of HA. When expressed in the baculovirus system, the modified sHA formed native trimers. In contrast, the unmodified sHA was found to present epitopes recognized by a low-pH conformation specific monoclonal antibody. We found that mice primed and boosted with 3 microg of trimeric sHA in the absence of adjuvants had significantly higher IgG and HAI titers than mice that received the unmodified sHA. This correlated with an increased survival and reduced body weight loss following lethal challenge with mouse-adapted A/Aichi/2/68 virus. In addition, mice receiving a single vaccination of the trimeric sHA in the absence of adjuvants had improved survival and body weight loss compared to mice vaccinated with the unmodified sHA.

CONCLUSIONS/SIGNIFICANCE

Our data indicate that the recombinant trimeric sHA presents native trimeric epitopes while the unmodified sHA presents epitopes not exposed in the native HA molecule. The epitopes presented in the unmodified sHA constitute a "silent face" which may skew the antibody response to epitopes not accessible in live virus at neutral pH. The results demonstrate that the trimeric sHA is a more effective influenza vaccine candidate and emphasize the importance of structure-based antigen design in improving recombinant HA vaccines.

Influenza vaccine preference and uptake among older people in nine countries

AIM

This paper is a report of a study delineating factors that influence older people's preferences and uptake of the influenza vaccine in nine countries.

BACKGROUND

Vaccination uptake for the aging population in many countries still remains below the World Health Organization recommended rate. Older people who perceive higher susceptibility to and severity of influenza, and more benefits from vaccination and action cues prompting vaccination, tend to accept the vaccine, but those with more perceived barriers to vaccination are less likely to accept it.

METHOD

A total of 208 older people from China, Indonesia, Turkey, Korea, Greece, Canada, the United Kingdom, Brazil and Nigeria were recruited to 14 vaccinated and 12 unvaccinated focus groups. They shared their experiences of influenza, and influenza vaccination, and promotion of influenza vaccination in focus groups. The data were collected in 2007.

FINDINGS

We identified five themes and generated a hypothetical framework for in-depth understanding of vaccination behaviour among older people. Participants' vaccine preferences were determined by their behavioural beliefs in vaccination, which were based on their probability calculation of susceptibility to and severity of influenza and vaccine effectiveness, and their utility calculation of vaccine, healthcare and social costs. Action cues prompting vaccination and vaccine access further affected the vaccine uptake of participants with vaccine preferences. Vaccination coverage was likely to be higher in the countries where normative beliefs in favour of vaccination had formed.

CONCLUSION

The hypothetical framework can be used to guide healthcare providers in developing strategies to foster normative beliefs of older people in vaccination, provide effective action cues and promote vaccine access.

Dose sparing enabled by skin immunization with influenza virus-like particle vaccine using microneedles

To address the limitations of conventional influenza vaccine manufacturing and delivery, this study investigated administration of virus-like particle (VLP) influenza vaccine using a microneedle patch. The goal was to determine if skin immunization with influenza VLP vaccine using microneedles enables dose sparing. We found that low-dose influenza (A/PR/8/34 H1N1) VLP vaccination using microneedles was more immunogenic than low-dose intramuscular (IM) vaccination and similarly immunogenic as high-dose IM vaccination in a mouse model. With a 1μg dose of vaccine, both routes showed similar immune responses and protective efficacy, with microneedle vaccination being more effective in inducing recall antibody responses in lungs and antibody secreting cells in bone marrow. With a low dose of vaccine (0.3μg), microneedle vaccination induced significantly superior protective immunity, which included binding and functional antibodies as well as complete protection against a high dose lethal infection with A/PR/8/34 virus, whereas IM immunization provided only partial (40%) protection. Therefore, this study demonstrates that microneedle vaccination in the skin confers more effective protective immunity at a lower dose, thus providing vaccine dose-sparing effects.

Recombinant soluble, multimeric HA and NA exhibit distinctive types of protection against pandemic swine-origin 2009 A(H1N1) influenza virus infection in ferrets

The emergence and subsequent swift and global spread of the swine-origin influenza virus A(H1N1) in 2009 once again emphasizes the strong need for effective vaccines that can be developed rapidly and applied safely. With this aim, we produced soluble, multimeric forms of the 2009 A(H1N1) HA (sHA(3)) and NA (sNA(4)) surface glycoproteins using a virus-free mammalian expression system and evaluated their efficacy as vaccines in ferrets. Immunization twice with 3.75-microg doses of these antigens elicited strong antibody responses, which were adjuvant dependent. Interestingly, coadministration of both antigens strongly enhanced the HA-specific but not the NA-specific responses. Distinct patterns of protection were observed upon challenge inoculation with the homologous H1N1 virus. Whereas vaccination with sHA(3) dramatically reduced virus replication (e.g., by lowering pulmonary titers by about 5 log(10) units), immunization with sNA(4) markedly decreased the clinical effects of infection, such as body weight loss and lung pathology. Clearly, optimal protection was achieved by the combination of the two antigens. Our observations demonstrate the great vaccine potential of multimeric HA and NA ectodomains, as these can be easily, rapidly, flexibly, and safely produced in high quantities. In particular, our study underscores the underrated importance of NA in influenza vaccination, which we found to profoundly and specifically contribute to protection by HA. Its inclusion in a vaccine is likely to reduce the HA dose required and to broaden the protective immunity.

Mammalian expression of virus-like particles for advanced mimicry of authentic influenza virus

BACKGROUND

Influenza A viruses are major human and animal pathogens with huge economic and societal impact from illness, hospitalizations, and deaths. Virus-like particles (VLPs) of influenza virus have been suggested as a vaccine candidate offering improved safety and efficacy. To develop this concept further, we established a flexible platform to efficiently generate different subtypes of mammalian-expressed influenza VLPs. Here we demonstrate that these mammalian VLPs strongly resemble the authentic viruses in structure, particle size and composition of host factors, and even glycosylation of viral antigens.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, a mammalian VLP system was established by stable co-expression of four influenza structural proteins (HA, NA, M1, and M2) in a Vero cell line. By replacing the surface glycoproteins of HA and NA, we converted the H3N2-VLP subtype to H5N1-VLP. After centrifugation purification of conditioned media, the particle morphologies, average sizes, and hemagglutination abilities of secreted VLPs were characterized, and the VLP constituents were identified by LC/MS/MS. Protease protection assays demonstrated that specific cellular proteins that co-purified with influenza virions were integrated into mammalian VLPs. The glycosylation profiles of mammalian VLPs as revealed by deglycosylation assays were similar to that of progeny viruses produced from Vero cells. Vaccination of mice with 2.5 microg and above of H5N1-VLP elicited H5-specific IgG1 antibodies and resulted in full protection against lethal infection with homologous virus. These results provide compelling evidence that mammalian VLPs closely emulate the exterior of authentic virus particles not only in antigen presentation but also in biological properties and should provide promising vaccine candidates.

CONCLUSIONS/SIGNIFICANCE

This flexible mammalian influenza VLP system offers a superior alternative to the conventional reverse genetic vaccine platform without concerns over inadequate presentation of immune antigens or limitations imposed by the manipulation of real viruses.

Research and development of universal influenza vaccines

The continuous threat of influenza pandemics determines the urgency and necessity to develop safe and effective vaccines against divergent influenza viruses. This review describes the advancements in the research and development of universal influenza vaccines based on the relatively conserved sequences of M2e, HA, and other proteins of influenza viruses.

Structure, receptor binding, and antigenicity of influenza virus hemagglutinins from the 1957 H2N2 pandemic

The hemagglutinin (HA) envelope protein of influenza viruses mediates essential viral functions, including receptor binding and membrane fusion, and is the major viral antigen for antibody neutralization. The 1957 H2N2 subtype (Asian flu) was one of the three great influenza pandemics of the last century and caused 1 million deaths globally from 1957 to 1968. Three crystal structures of 1957 H2 HAs have been determined at 1.60 to 1.75 A resolutions to investigate the structural basis for their antigenicity and evolution from avian to human binding specificity that contributed to its introduction into the human population. These structures, which represent the highest resolutions yet recorded for a complete ectodomain of a glycosylated viral surface antigen, along with the results of glycan microarray binding analysis, suggest that a hydrophobicity switch at residue 226 and elongation of receptor-binding sites were both critical for avian H2 HA to acquire human receptor specificity. H2 influenza viruses continue to circulate in birds and pigs and, therefore, remain a substantial threat for transmission to humans. The H2 HA structure also reveals a highly conserved epitope that could be harnessed in the design of a broader and more universal influenza A virus vaccine.

Prior infection with an H1N1 swine influenza virus partially protects pigs against a low pathogenic H5N1 avian influenza virus

Most humans lack virus neutralizing (VN) and haemagglutination inhibition (HI) antibodies to H5N1 avian influenza viruses (AIVs), but cross-reactive neuraminidase inhibition (NI) antibodies and cell-mediated immune (CMI) responses are common. These immune responses result largely from infections with seasonal human H1N1 influenza viruses, but the protective effect of H1N1 infection-immunity against H5N1 infection has never been examined. To this purpose, we have used the pig model of influenza and a low pathogenic (LP) H5N1 AIV. Pigs were inoculated intranasally with sw/Belgium/1/98 (H1N1) 4 weeks before challenge with duck/Minnesota/1525/81 (H5N1). While the viruses failed to cross-react in HI and VN tests, the H1N1 infection induced high levels of H5N1 cross-reactive NI antibodies. Cross-reactive CMI was demonstrated by measurements of lymphoproliferation and IFN-gamma secretion after in vitro restimulation of peripheral blood mononuclear cells. All control pigs showed clinical signs and H5N1 virus isolation from the respiratory tract post-challenge. The H1N1-immune pigs, in contrast, showed a complete clinical protection and only 3 pigs out of 10 were H5N1 virus-positive. In a second and smaller experiment, H1N1 virus infection also conferred cross-protection against a LP H5N2 AIV, while cross-reactive immunity was solely detected in tests for CMI. Our data further support the notion that immunity induced by seasonal human H1N1 influenza virus infection may provide some protection against H5N1 or other H5 AIVs in the absence of neutralizing H5 antibodies. Further studies should reveal whether cross-protection holds against H5N1 viruses that are better adapted to replicate in mammals or with a more distantly related N1.

Baculovirus vector as a delivery vehicle for influenza vaccines

The baculovirus vector has emerged as an efficient delivery vehicle for influenza vaccines. In addition to the ease and safety in expeditious production, recent improvements in baculovirus engineering to display foreign proteins on the surface and to express transgenes with suitable promoters in various cell lines have become milestones in the development of the baculovirus expression system. Surface-displayed and shuttle promoter-mediated baculovirus vaccines for influenza present advantages in immunogenicity and safety, as studied in several animal models. A variety of strategies, including the modification of envelope proteins for surface display, the selection of novel promoters for in vivo transductions and advancements in downstream processing, aid the improvement of baculovirus-based influenza vaccines and represent progress toward next-generation vaccines for influenza.

Influenza vaccines based on virus-like particles

The simultaneous expression of structural proteins of virus can produce virus-like particles (VLPs) by a self-assembly process in a viral life cycle even in the absence of genomic material. Taking an advantage of structural and morphological similarities of VLPs to native virions, VLPs have been suggested as a promising platform for new viral vaccines. In the light of a pandemic threat, influenza VLPs have been recently developed as a new generation of non-egg based cell culture-derived vaccine candidates against influenza infection. Animals vaccinated with VLPs containing hemagglutinin (HA) or HA and neuraminidase (NA) were protected from morbidity and mortality resulting from lethal influenza infections. Influenza VLPs serve as an excellent model system of an enveloped virus for understanding the properties of VLPs in inducing protective immunity. In this review, we briefly describe the characteristics of influenza VLPs assembled with a lipid bilayer containing glycoproteins, and summarize the current progress on influenza VLPs as an alternative vaccine candidate against seasonal as well as pandemic influenza viruses. In addition, the protective immune correlates induced by vaccination with influenza VLPs are discussed.

Development of a vaccine against pandemic influenza viruses: current status and perspectives

The constant threat of a new influenza pandemic, which may be caused by a highly pathogenic avian influenza virus, necessitates the development of a vaccine capable of providing efficient, long-term, and cost-effective protection. Proven avenues for the development of vaccines against seasonal influenza as well as novel approaches have been explored over the past decade. Whereas significant insights are consistently being made, the generation of a highly efficient and cross-protective vaccine against the future pandemic influenza strain remains as the ultimate goal in the field. In this review, we re-examine these efforts and outline the scientific, political, and economic problems that befall this area of biotechnological research.

Induction of long-term protective immune responses by influenza H5N1 virus-like particles

Background

Recurrent outbreaks of highly pathogenic H5N1 avian influenza virus pose a threat of eventually causing a pandemic. Early vaccination of the population would be the single most effective measure for the control of an emerging influenza pandemic.

Methodology/Principal Findings

Influenza virus-like particles (VLPs) produced in insect cell-culture substrates do not depend on the availability of fertile eggs for vaccine manufacturing. We produced VLPs containing influenza A/Viet Nam1203/04 (H5N1) hemagglutinin, neuraminidase, and matrix proteins, and investigated their preclinical immunogenicity and protective efficacy. Mice immunized intranasally with H5N1 VLPs developed high levels of H5N1 specific antibodies and were 100% protected against a high dose of homologous H5N1 virus infection at 30 weeks after immunization. Protection is likely to be correlated with humoral and cellular immunologic memory at systemic and mucosal sites as evidenced by rapid anamnestic responses to re-stimulation with viral antigen in vivo and in vitro.

Conclusions/Significance

These results provide support for clinical evaluation of H5N1 VLP vaccination as a public health intervention to mitigate a possible pandemic of H5N1 influenza.

Comparing the antibody responses against recombinant hemagglutinin proteins of avian influenza A (H5N1) virus expressed in insect cells and bacteria

The hemagglutinin (HA) of influenza A virus plays an essential role in mediating the entry of the virus into host cells. Here, recombinant full-length HA5 protein from a H5N1 isolate (A/chicken/hatay/2004(H5N1)) was expressed and purified from the baculovirus-insect cell system. As expected, full-length HA5 elicits strong neutralizing antibodies, as evaluated in micro-neutralization tests using HA5 pseudotyped lentiviral particles. In addition, two fragments of HA5 were expressed in bacteria and the N-terminal fragment, covering the ectodomain before the HA1/HA2 polybasic cleavage site, was found to elicit neutralizing antibodies. But the C-terminal fragment, which covers the remaining portion of the ectodomain, did not. Neutralizing titer of the anti-serum against the N-terminal fragment is only four times lower than the anti-serum against the full-length HA5 protein. Using a novel membrane fusion assay, the abilities of these antibodies to block membrane fusion were found to correlate well with the neutralization activities.

Structural characterization of the 1918 influenza virus H1N1 neuraminidase

Influenza virus neuraminidase (NA) plays a crucial role in facilitating the spread of newly synthesized virus in the host and is an important target for controlling disease progression. The NA crystal structure from the 1918 "Spanish flu" (A/Brevig Mission/1/18 H1N1) and that of its complex with zanamivir (Relenza) at 1.65-A and 1.45-A resolutions, respectively, corroborated the successful expression of correctly folded NA tetramers in a baculovirus expression system. An additional cavity adjacent to the substrate-binding site is observed in N1, compared to N2 and N9 NAs, including H5N1. This cavity arises from an open conformation of the 150 loop (Gly147 to Asp151) and appears to be conserved among group 1 NAs (N1, N4, N5, and N8). It closes upon zanamivir binding. Three calcium sites were identified, including a novel site that may be conserved in N1 and N4. Thus, these high-resolution structures, combined with our recombinant expression system, provide new opportunities to augment the limited arsenal of therapeutics against influenza.

New vaccine approaches for seasonal and pandemic influenza

Inactivated influenza vaccines have been available since the late 1940s for the prevention of influenza disease. Based on the available scientific evidence, many public health authorities, including the World Health Organization, recommend annual use of these vaccines for specific populations, including the elderly. Despite these recommendations, actual vaccination uptake rates are very limited in many countries. Influenza vaccine research is confounded by the variable nature of the influenza viruses and annual influenza epidemics and by non-specific clinical diagnostic criteria. These confounding factors complicate evaluation not only of overall vaccine effectiveness, but also of the relative efficacy and effectiveness of different vaccine formulations. This paper summarizes recent advances in the development of seasonal and (pre-)pandemic vaccines, discusses the methodologic constraints on influenza vaccine research, and proposes measures to reduce the level of potential bias and confounding in influenza vaccine research.

Proteomics integrated with Escherichia coli vector-based vaccines and antigen microarrays reveals the immunogenicity of a surface sialidase-like protein of Propionibacterium acnes

Proteomics is a powerful tool for the identification of proteins, which provides a basis for rational vaccine design. However, it is still a highly technical and time-consuming task to examine a protein's immunogenicity utilizing traditional approaches. Here, we present a platform for effectively evaluating protein immunogenicity and antibody detection. A tetanus toxin C fragment (Tet-c) was used as a representative antigen to establish this platform. A cell wall-anchoring sialidase-like protein (SLP) of Propionibacterium acnes was utilized to assess the efficacy of this platform. We constructed an Escherichia coli vector-based vaccine by overexpressing Tet-c or SLP in E. coli and utilized an intact particle of E. coli itself as a vaccine (E. coli Tet-c or SLP vector). After ultraviolet (UV) irradiation, the E. coli vector-based vaccines were administered intranasally into imprinting control region mice without adding exogenous adjuvants. For antibody detection, we fabricated antigen microarrays by printing with purified recombinant proteins including Tet-c and SLP. Our results demonstrated that detectable antibodies were elicited in mice 6 weeks after intranasal administration of UV-irradiated E. coli vector-based vaccines. The antibody production of Tet-c and SLP was significantly elevated after boosting. Notably, the platform with main benefits of using E. coli itself as a vaccine carrier provides a critical template for applied proteomics aimed at screening novel vaccine targets. In addition, the novel immunogenic SLP potentially serves as an antigen candidate for the development of vaccines targeting P. acnes-associated diseases.

Inhibition of influenza A H3N8 virus infections in mice by morpholino oligomers

New methods to combat influenza A virus (FLUAV) in humans and animals are needed. The H3N8 subtype virus was the cause of the pandemic of 1890 and has recently undergone cross-species transmission from horses to dogs in the USA. In 2007 H3N8 spread to Australia, a continent previously devoid of equine influenza. Here, we show that antisense-peptide-conjugated phosphorodiamidate morpholino oligomers (PPMOs), delivered by intranasal administration, are able to inhibit the replication of FLUAV A/Eq/Miami/1/63 (H3N8) in mice by over 95% compared to controls. Monitoring of body weight and immune cell infiltrates in the lungs of noninfected mice indicated that PPMO treatment was not toxic at a concentration shown to be effectively antiviral in vivo. In addition, we detected a naturally occurring mutation within the PPMO target site of a viral gene that may be the cause of resistance to one of the two antisense PPMO sequences tested. These data indicate that PPMOs targeting highly conserved regions of FLUAV are promising novel therapeutic candidates.