Recombinant protein comprising multi-neutralizing epitopes induced high titer of antibodies against Influenza A virus

PD-1 and ICOS counter-regulate tissue resident regulatory T cell development and IL-10 production during flu

Regulatory T cells that express the transcription factor Foxp3 (Treg cells) are a highly heterogenous population of immunoregulatory cells critical for maintaining immune homeostasis and preventing immunopathology during infections. Tissue resident Treg (TR-Treg) cells are maintained within nonlymphoid tissues and have been shown to suppress proinflammatory tissue resident T cell responses and promote tissue repair. Human populations are repetitively exposed to influenza infections and lung tissue resident effector T cell responses are associated with flu-induced long-term pulmonary sequelae. The kinetics of TR-Treg cell development and molecular features of TR-Treg cells during repeated and/or long-term flu infections are unclear. Utilizing a Foxp3^RFP/IL-10^GFP dual reporter mouse model along with intravascular fluorescent in vivo labeling, we characterized the TR-Treg cell responses to repetitive heterosubtypic influenza infections. We found lung tissue resident Treg cells accumulated and expressed high levels of co-inhibitory and co-stimulatory receptors post primary and secondary infections. Blockade of PD-1 or ICOS signaling reveals that PD-1 and ICOS signaling pathways counter-regulate TR-Treg cell expansion and IL-10 production, during secondary influenza infection. Furthermore, the virus-specific TR-Treg cell response displayed distinct kinetics, when compared to conventional CD4⁺ tissue resident memory T cells, during secondary flu infection. Our results provide insight into the tissue resident Foxp3⁺ regulatory T cell response during repetitive flu infections, which may be applicable to other respiratory infectious diseases such as tuberculosis and COVID.

Evolutionary conservation and positive selection of Influenza A Nucleoprotein CTL epitopes for universal vaccination: a proof-of-concept

Influenza (flu) infection is a leading cause of respiratory disease and death worldwide. While seasonal flu vaccines are effective at reducing morbidity and mortality, such effects rely on the odds of successful prediction of the upcoming viral strains. Additional threats from emerging flu viruses that we cannot predict and avian flu viruses that can be directly transmitted to humans, urge the strategic development of universal vaccinations that can protect against flu viruses of different subtypes and across species. Annual flu vaccines elicit mainly humoral responses. Under circumstances when antibodies induced by vaccination fail to recognize and neutralize the emerging virus adequately, virus-specific cytotoxic T lymphocytes (CTLs) are the major contributors to the control of viral replication and elimination of infected cells. Our studies exploited the evolutionary conservation of influenza A nucleoprotein (NP) and the fact that NP-specific CTL responses pose a constant selecting pressure on functional CTL epitopes, to screen for NP epitopes that are highly conserved among heterosubtypes but are subjected to positive selection historically. We identified a region on NP that is evolutionarily conserved and historically positively selected (NP_137-182 ) and validated that it contains an epitope that is functional in eliciting NP-specific CTL responses and immunity that can partially protect immunized mice against lethal dose infection of a heterosubtypic influenza A virus. Our proof-of-concept study supports the hypothesis that evolutionary conservation and positive selection of influenza nucleoprotein can be exploited to identify functional CTL epitope to elicit cross protection against different heterosubtypes, therefore, to help develop strategies to modify flu vaccine formula for a broader and more durable protective immunity. This article is protected by copyright. All rights reserved.

H1N1 influenza virus epitopes classified by monoclonal antibodies

Epitopes serve an important role in influenza infection. It may be useful to screen universal influenza virus vaccines, analyzing the epitopes of multiple subtypes of the hemagglutinin (HA) protein. A total of 40 monoclonal antibodies (mAbs) previously obtained from flu virus HA antigens (development and characterization of 40 mAbs generated using H1N1 influenza virus split vaccines were previously published) were used to detect and classify mAbs into distinct flu virus sub-categories using the ELISA method. Following this, the common continuous amino acid sequences were identified by multiple sequence alignment analysis with the GenBank database and DNAMAN software, for use in predicting the epitopes of the HA protein. Synthesized peptides of these common sequences were prepared, and used to verify and determine the predicted linear epitopes through localization and distribution analyses. With these methods, nine HA linear epitopes distributed among different strains of influenza virus were identified, which included three from influenza A, four from 2009 H1N1 and seasonal influenza, and two from H1. The present study showed that considering a combination of the antigen-antibody reaction specificity, variation in the influenza virus HA protein and linear epitopes may present a useful approach for designing effective multi-epitope vaccines. Furthermore, the study aimed to clarify the cause and pathogenic mechanism of influenza virus HA-induced flu, and presents a novel idea for identifying the epitopes of other pathogenic microorganisms.

DNA-vaccine platform development against H1N1 subtype of swine influenza A viruses

Swine influenza virus (SIV) is an important viral pathogen in pig populations. However, commercial vaccines cannot provide complete protection with induced humoral immunity only, and require frequent updates to fight against current isolates. DNA vaccination is an effective means of eliciting both arms of the immune system, the humoral and cellular immune responses. In this study, DNA vector pcDNA3.1 was inserted with a chimeric intron downstream of the CMV promoter region followed by a Kozak sequence to enhance the expression of gene inserts. The C-terminal of the VP22 gene (VP22c), encoding the tegument protein of bovine herpesvirus-1, was fused separately to the N-terminal of four quadruplicated epitopes: two B-cell epitopes (HA91-108 and M2e), and two T-cell epitopes (NP366-374 and NP380-393), which were conserved, at least among the three SIV subtypes prevailing in pig populations in North America. Linker -KK- was used to space between each copy of the two B-cell epitopes, and -RVKR- was used for the two T-cell epitopes, in order to enhance the presentation of epitopes to the immune system. The expression of epitopes was confirmed in in vitro transfection of 293FT cells, and higher percentages of epitope-positive cells were achieved from the plasmids containing VP22c than those without. After the DNA plasmids were administered to mice intramuscularly in combination or separately, or boosted with recombinant proteins of quadruplicated epitopes fused to VP22c, the vaccine stimulated the desired epitope-specific humoral immunity to the two B-cell epitopes, and cellular immunity to the epitope NP380-393. Our results indicate that plasmids with quadruplicated epitopes fused to the VP22c may be a potential vehicle in developing epitopes as vaccines against SIV.

Investigation of the biological indicator for vaccine efficacy against highly pathogenic avian influenza (HPAI) H5N1 virus challenge in mice and ferrets

To investigate the biological indicator for vaccine efficacy against HPAI H5N1 virus challenge of varying clades, two inactivated whole-virus H5N1 vaccines containing the hemagglutinin (HA) and neuraminidase (NA) genes of either clade 2.2 A/EM/Korea/W149/06 (RgKoreaW149/06 x PR8) or clade 2.5 A/Ck/Korea/ES/03 (RgKoreaES223N/03XPR8) virus in the background of A/PR/8/34 (H1N1) were generated by reverse genetics. Administration of the vaccines (2-dose 1.77, 3.5, 7.5 or 15microg of HA) elicited high HI titers in a dose-dependent manner. Mice immunized with RgKoreaW149/06 x PR8 were completely protected from challenge against wild-type A/EM/Korea/W149/06 without clinical signs of infection. RgKoreaES223N/03XPR8 could not protect mice at 1.77microg while all immunized ferrets were completely protected. Two-dose (7.5microg) vaccinated mice (HI titer > or =320) and triple dose (7.5 microg) vaccinated ferrets with RgKoreaES223N/03xPR8 (HI titer > or =640) protected vaccine recipients from mortality, inhibited nasal virus shedding and limited influenza virus tropism. Thus, these vaccines provided cross-protectivity in both models. More importantly, these results collectively suggested a positive correlation between vaccine-induced HI titers and inhibition of virus shedding including block of viral proliferation in major organs against a heterologous HPAI H5N1 virus. Although developing technologies or methods that will enable the reduction of administration dose/frequency remains to be resolved, our study demonstrated a considerable biological marker (> or =640 HI titer) for full protection of the vaccinated hosts that could provide a preliminary basis for the assessment of complete immunization.

Characterization of immunity induced by M2e of influenza virus

The extracellular-domain of influenza Matrix 2 protein (M2e) is considered as a putative target for designing universal influenza vaccines. However, the mechanism by which M2-based vaccine induces protection has not been clear. In this study, we analyzed the immunity induced by free synthetic M2e peptide and found the peptide was highly immunogenic. Without carrier proteins, the synthetic M2e peptide could induce M2e-specific IgG antibodies in both incomplete Freund's and aluminum adjuvant. The peptide could also provoke M2e-specific T cell response, which could not be mounted by influenza virus. Moreover, immunization with M2e peptide could protect mice from a lethal challenge with influenza virus. These results provide useful information for the development of M2e-based influenza vaccine.

The epitope recognized by a monoclonal antibody in influenza A virus M2 protein is immunogenic and confers immune protection

Based on our previous study that the monoclonal antibody (mAb) 8C6 recognizing the extracellular domain of influenza A virus M2 protein (M2e) could passively induce protective immunity in mice, epitope mapping was performed in this study. A series of eight mutated M2e were constructed and expressed. It was found in immunoblotting assay that 8C6 could not bind to two of the mutated M2e proteins, which suggested the VETPIR epitope (aa7-12) in M2e for mAb 8C6. More important, EVETPIRN-peptide (aa6-13) conjugated immunogen induced high M2e specific antibody titer (1:25,600) in mice after booster immunization, and provided mice significantly 40% higher survival rate compared with the control group in challenge assay (p=0.0215), which suggested the EVETPIRN-epitope was immunogenic and actively conferred immune protection to some extent. In addition, sequence comparison suggested the EVETPIRN sequence (aa6-13) was highly conserved in all human influenza A strains. All these data suggested the EVETPIRN sequence in M2e could be one new target for influenza vaccine design.

Advances in viral respiratory infections: new experimental models

The wide array of models available for the study of respiratory viral infections is extremely valuable for the development of novel therapeutic and prophylactic options against these highly prevalent diseases. In addition, through these models we have gathered considerable insight into the cellular and molecular mechanisms involved in the pathogenesis of these infections and the inflammatory and immune responses they elicit in the host. This article reviews new promising models introduced recently in this field.

Alastair Stewart – University of Melbourne, Australia

There has long been interest in the potential relationships between viral respiratory illness and chronic respiratory disease. However, until relatively recently there have been few attempts to develop animal models that address chronic influences of acute and chronic infections. Professor Piedimonte and colleagues provide a commentary on the impact of molecular biology on studies of viral infection and address the important issues that arise in selecting appropriate strains and species to model the course of infection, inflammation and long term sequelae.