Immune profiling of influenza-specific B- and T-cell responses in macaques using flow cytometry-based assays

The efficacy and mechanism of salmeterol against influenza A virus in vitro and in vivo

Influenza A virus (IAV) is the most harmful pathogen to human beings among the various subtypes of influenza virus, which can lead to immune response, cause serious inflammation and damage to the lung. Salmeterol is a candidate compound with anti-IAV activity screened by virtual network proximity predication. In this paper, we further evaluated the pharmacodynamics of salmeterol against IAV in vivo and in vitro. The results showed that salmeterol could inhibit the activity of three IAV strains (H1N1, H3N2 and H1N1 strain resistant to oseltamivir and amantadine) in the MDCK cells. In vivo, salmeterol could improve the survival state of infected mice, and further mechanism studies shown that salmeterol could improve the pathological characteristics of the lungs, reduce the loads of virus and the expression of M2 and IFITM3 proteins in the lungs of mice. In addition, salmeterol could inhibit the formation of NLRP3 inflammasome, thus reducing the production of the TNF-α, IL-6 and MCP-1 and alleviating inflammatory symptoms. Further results showed that salmeterol can protect A549 cells from cytopathic effect caused by IAV and reduce the production of inflammasome by decreasing the expression of RIG-1 in A549 cells. Finally, salmeterol could improve the spleen morphology and significantly increase the ratio of lymphocyte CD4⁺/CD8⁺ to improve immune function of infected mice. In our study, it is confirmed that salmeterol has certain anti-IAV activity through pharmacodynamic study in vivo and in vitro, which lays an important research foundation for the new indication of salmeterol and discovery of new drug against IAV.

Immunization with inactivated whole virus particle influenza virus vaccines improves the humoral response landscape in cynomolgus macaques

Although antibody-inducing split virus vaccines (SV) are currently the most effective way to combat seasonal influenza, their efficacy can be modest, especially in immunologically-naïve individuals. We investigated immune responses towards inactivated whole influenza virus particle vaccine (WPV) formulations, predicated to be more immunogenic, in a non-human primate model, as an important step towards clinical testing in humans. Comprehensive analyses were used to capture 46 immune parameters to profile how WPV-induced responses differed to those elicited by antigenically-similar SV formulations. Naïve cynomolgus macaques vaccinated with either monovalent or quadrivalent WPV consistently induced stronger antibody responses and hemagglutination inhibition (HI) antibody titres against vaccine-matched viruses compared to SV formulations, while acute reactogenic effects were similar. Responses in WPV-primed animals were further increased by boosting with the same formulation, conversely to modest responses after priming and boosting with SV. 28-parameter multiplex bead array defined key antibody features and showed that while both WPV and SV induced elevated IgG responses against A/H1N1 nucleoprotein, only WPV increased IgG responses against A/H1N1 hemagglutinin (HA) and HA-Stem, and higher IgA responses to A/H1N1-HA after each vaccine dose. Antibodies to A/H1N1-HA and HA-Stem that could engage FcγR2a and FcγR3a were also present at higher levels after one dose of WPV compared to SV and remained elevated after the second dose. Furthermore, WPV-enhanced antibody responses were associated with higher frequencies of HA-specific B-cells and IFN-γ-producing CD4+ T-cell responses. Our data additionally demonstrate stronger boosting of HI titres by WPV following prior infection and support WPV administered as a priming dose irrespective of the follow up vaccine for the second dose. Our findings thus show that compared to SV vaccination, WPV-induced humoral responses are significantly increased in scope and magnitude, advocating WPV vaccination regimens for priming immunologically-naïve individuals and also in the event of a pandemic outbreak.

Influenza A Virus Hemagglutinin Trimer, Head and Stem Proteins Identify and Quantify Different Hemagglutinin-Specific B Cell Subsets in Humans

Antibody responses against the influenza A virus hemagglutinin (HA)-protein are studied intensively because they can protect against (re)infection. Previous studies have focused on antibodies targeting the head or stem domains, while other possible specificities are often not taken into account. To study such specificities, we developed a diverse set of HA-domain proteins based on an H1N1pdm2009-like influenza virus strain, including monomeric head and trimeric stem domain, as well as the full HA-trimer. These proteins were used to study the B cell and antibody responses in six healthy human donors. A large proportion of HA-trimer B cells bound exclusively to HA-trimer probe (54-77%), while only 8-18% and 9-23% were able to recognize the stem or head probe, respectively. Monoclonal antibodies (mAbs) were isolated and three of these mAbs, targeting the different domains, were characterized in-depth to confirm the binding profile observed in flow cytometry. The head-directed mAb, targeting an epitope distinct from known head-specific mAbs, showed relatively broad H1N1 neutralization and the stem-directed mAb was able to broadly neutralize diverse H1N1 viruses. Moreover, we identified a trimer-directed mAb that did not compete with known head or stem domain specific mAbs, suggesting that it targets an unknown epitope or conformation of influenza virus' HA. These observations indicate that the described method can characterize the diverse antibody response to HA and might be able to identify HA-specific B cells and antibodies with previously unknown specificities that could be relevant for vaccine design.

Animal Models for Influenza Research: Strengths and Weaknesses

Influenza remains one of the most significant public health threats due to its ability to cause high morbidity and mortality worldwide. Although understanding of influenza viruses has greatly increased in recent years, shortcomings remain. Additionally, the continuous mutation of influenza viruses through genetic reassortment and selection of variants that escape host immune responses can render current influenza vaccines ineffective at controlling seasonal epidemics and potential pandemics. Thus, there is a knowledge gap in the understanding of influenza viruses and a corresponding need to develop novel universal vaccines and therapeutic treatments. Investigation of viral pathogenesis, transmission mechanisms, and efficacy of influenza vaccine candidates requires animal models that can recapitulate the disease. Furthermore, the choice of animal model for each research question is crucial in order for researchers to acquire a better knowledge of influenza viruses. Herein, we reviewed the advantages and limitations of each animal model-including mice, ferrets, guinea pigs, swine, felines, canines, and non-human primates-for elucidating influenza viral pathogenesis and transmission and for evaluating therapeutic agents and vaccine efficacy.

Protocol for Creating Antibodies with Complex Fluorescence Spectra

Fluorescent antibodies are a workhorse of biomedical science, but fluorescence multiplexing has been notoriously difficult due to spectral overlap between fluorophores. We recently established proof-of-principal for fluorescence Multiplexing using Spectral Imaging and Combinatorics (MuSIC), which uses combinations of existing fluorophores to create unique spectral signatures for increased multiplexing. However, a method for labeling antibodies with MuSIC probes has not yet been developed. Here, we present a method for labeling antibodies with MuSIC probes. We conjugate a DBCO-Peg5-NHS ester linker to antibodies and a single-stranded DNA "docking strand" to the linker and, finally, hybridize two MuSIC-compatible, fluorescently labeled oligos to the docking strand. We validate the labeling protocol with spin-column purification and absorbance measurements. We demonstrate the approach using (i) Cy3, (ii) Tex615, and (iii) a Cy3-Tex615 combination as three different MuSIC probes attached to three separate batches of antibodies. We created single-, double-, and triple-positive beads that are analogous to single cells by incubating MuSIC probe-labeled antibodies with protein A beads. Spectral flow cytometry experiments demonstrate that each MuSIC probe can be uniquely distinguished, and the fraction of beads in a mixture with different staining patterns are accurately inferred. The approach is general and might be more broadly applied to cell-type profiling or tissue heterogeneity studies in clinical, biomedical, and drug discovery research.