The antibody landscapes against Group 1 and 2 influenza virus hemagglutinin following AS03 and MF59 adjuvanted H5N1 vaccination

Current seasonal and pre-pandemic influenza vaccines induce short-lived predominantly strain-specific and limited heterosubtypic responses. To better understand how vaccine adjuvants AS03 and MF59 may provide improved antibody responses to vaccination, we interrogated serum from subjects who received 2 doses of inactivated monovalent influenza A/Indonesia/05/2005 vaccine with or without AS03 or MF59 using hemagglutinin (HA) microarrays. The arrays were designed to reflect both full length and globular head HA proteins derived from 17 influenza A subtypes (H1 to H16 and H18) and influenza B strains. We observed significantly increased strain-specific and broad homo- and hetero-subtypic antibody responses with both AS03 and MF59 adjuvanted vaccination with AS03 achieving a higher titer and breadth of IgG responses relative to MF59. Adjuvanted vaccine was also associated with the elicitation of stalk directed antibody. Finally, we established good correlation of the array antibody responses to H5 antigens with standard hemagglutination inhibition and microneutralization titers.

A Prevalent Focused Human Antibody Response to the Influenza Virus Hemagglutinin Head Interface

The rapid appearance of mutations in circulating human influenza viruses and selection for escape from herd immunity require prediction of likely variants for an annual updating of influenza vaccines. The identification of human antibodies that recognize conserved surfaces on the influenza virus hemagglutinin (HA) has prompted efforts to design immunogens that might selectively elicit such antibodies.

Librator, a platform for optimized sequence editing, design, and expression of influenza virus proteins

Artificial mutagenesis and chimeric/mosaic protein engineering have laid the foundation for antigenic characterization1 and universal vaccine design2–4 for influenza viruses. However, many methods used for influenza research and vaccine development require sequence editing and protein expression, limiting their applicability and the progress of related research to specialists. Rapid tools allowing even novice influenza researchers to properly analyze and visualize influenza protein sequences with accurate nomenclature are needed to expand the research field. To address this need, we developed Librator, a system for analyzing and designing protein sequences of influenza virus Hemagglutinin (HA) and Neuraminidase (NA). With Librator’s graphical user interface (GUI) and built-in sequence editing functions, biologists can easily analyze influenza sequences and phylogenies, automatically port sequences to visualize structures, then readily mutate target residues and design sequences for antigen probes and chimeric/mosaic proteins efficiently and accurately. This system provides optimized fragment design for Gibson Assembly5 of HA and NA expression constructs based on peptide conservation of all historical HA and NA sequences, ensuring fragments are reusable and compatible, allowing for significant reagent savings. Use of Librator will significantly facilitate influenza research and vaccine antigen design.

Antivirals Targeting the Surface Glycoproteins of Influenza Virus: Mechanisms of Action and Resistance

Hemagglutinin and neuraminidase, which constitute the glycoprotein spikes expressed on the surface of influenza A and B viruses, are the most exposed parts of the virus and play critical roles in the viral lifecycle. As such, they make prominent targets for the immune response and antiviral drugs. Neuraminidase inhibitors, particularly oseltamivir, constitute the most commonly used antivirals against influenza viruses, and they have proved their clinical utility against seasonal and emerging influenza viruses. However, the emergence of resistant strains remains a constant threat and consideration. Antivirals targeting the hemagglutinin protein are relatively new and have yet to gain global use but are proving to be effective additions to the antiviral repertoire, with a relatively high threshold for the emergence of resistance. Here we review antiviral drugs, both approved for clinical use and under investigation, that target the influenza virus hemagglutinin and neuraminidase proteins, focusing on their mechanisms of action and the emergence of resistance to them.

Serological and Molecular Detection of Avian Influenza Virus ‎Hemagglutinin (H5) in Wild Birds in and around Zaria, Nigeria

Avian influenza (AI) has a worldwide distribution and affects domestic and wild birds, thus causing great economic losses to the poultry industry. This study was carried out to detect avian influenza virus H5 antibodies and nucleic acidin some wild birds [Laughing doves (Spilolepia senegalensis), Speckled pigeons (Columba guinea), Cattle egrets (Bubulcus ibis), Senegalese parrots (Poicephalussenegalus), Mallards (Anas platyrhynchos) and Geese (Anseranserini)] in Zaria and its environs, Kaduna State Nigeria. Sera were tested for avian influenza virus (AIV) H5 antibody using competitive enzyme linked immunosorbent assay (cELISA). Pooled oropharyngeal and cloacal swabs of each bird species (8-10 samples) were tested for AIV nucleic acidusing one-stepreverse transcriptase polymerase chain reaction (RT-PCR). Results revealed overall prevalence of 6.62% and 3.85% for AIV antibody and nucleic acid respectively. Based on species, AIV antibody was detected in laughing dove (10%), speckled pigeon (13.64%) and mallard (19.05%).Also, AIV antigen was detected in Senegalese parrot (20%).In conclusion, AIV antibody and antigen were detected in wild birds in Zaria, Nigeria. Thus, these species of birds could play significant roles in the spread of this virus to chickens. Therefore, measures to limit the interactions of these wild birds with chickens should be implemented to minimize the spread of AI.

A public broadly neutralizing antibody class targets a membrane-proximal anchor epitope of influenza virus hemagglutinin

SummaryBroadly neutralizing antibodies against influenza virus hemagglutinin (HA) have the potential to provide universal protection against influenza virus infections. Here, we report a distinct class of broadly neutralizing antibodies targeting an epitope toward the bottom of the HA stalk domain where HA is “anchored” to the viral membrane. Antibodies targeting this membrane-proximal anchor epitope utilized a highly restricted repertoire, which encode for two conserved motifs responsible for HA binding. Anchor targeting B cells were common in the human memory B cell repertoire across subjects, indicating pre-existing immunity against this epitope. Antibodies against the anchor epitope at both the serological and monoclonal antibody levels were potently induced in humans by a chimeric HA vaccine, a potential universal influenza virus vaccine. Altogether, this study reveals an underappreciated class of broadly neutralizing antibodies against H1-expressing viruses that can be robustly recalled by a candidate universal influenza virus vaccine.

Identification and Characterization of Novel Antibody Epitopes on the N2 Neuraminidase

ABSTRACT The influenza virus neuraminidase (NA) is becoming a focus for novel vaccine designs. However, the epitopes of human anti-NA antibodies have been poorly defined. Using a panel of 10 anti-N2 monoclonal antibodies (MAbs) that bind the H3N2 virus A/Switzerland/9715293/2013, we generated five escape mutant viruses. These viruses contained mutations K199E/T, E258K, A272D, and S331N. We found that mutations at K199 and E258 had the largest impact on MAb binding, NA inhibition and neutralization activity. In addition, a natural isolate from the 2017-2018 season was found to contain the E258K mutation and was resistant to numerous antibodies tested. The mutation S331N, was identified in virus passaged in the presence of antibody; however, it had little impact on MAb activity and greatly decreased viral fitness. This information aids in identifying novel human MAb epitopes on the N2 and helps with the detection of antigenically drifted NAs. IMPORTANCE The influenza virus neuraminidase is an emerging target for universal influenza virus vaccines. However, in contrast to influenza virus hemagglutinin, we know little about antibody epitopes and antigenic sites on the neuraminidase. Characterizing and defining these sites is aiding vaccine development and helping to understand antigenic drift of NA.