Aaron Farnsworth

Universal antibodies and their applications to the quantitative determination of virtually all subtypes of the influenza A viral hemagglutinins

The fusion peptide is the only universally conserved sequence in the hemagglutinins of all 16 subtypes of influenza A and two genetic lineages of influenza B viruses. Here, peptides selected by bioinformatics approach were modified and conjugated to overcome serious technical hurdles such as the high hydrophobicity and weak immunogenicity of the viral fusion peptides. Antibodies generated against fusion peptides demonstrated remarkable specificity against the viral sequences and robustness of quantitatively analyzing the viral hemagglutinins even under stringent conditions. As quantitatively revealed by antibody-binding experiments, the fusion peptides of diverse hemagglutinins are exposed to the same degree upon unfolding at neutral pH to the physiologically fusogenic state. To our knowledge, this is the first report on the quantitative determination of virtually all influenza vaccines using a single universal antibody.

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.

Aurintricarboxylic Acid Is a Potent Inhibitor of Influenza A and B Virus Neuraminidases

Background Influenza viruses cause serious infections that can be prevented or treated using vaccines or antiviral agents, respectively. While vaccines are effective, they have a number of limitations, and influenza strains resistant to currently available anti-influenza drugs are increasingly isolated. This necessitates the exploration of novel anti-influenza therapies. Methodology/Principal Findings We investigated the potential of aurintricarboxylic acid (ATA), a potent inhibitor of nucleic acid processing enzymes, to protect Madin-Darby canine kidney cells from influenza infection. We found, by neutral red assay, that ATA was protective, and by RT-PCR and ELISA, respectively, confirmed that ATA reduced viral replication and release. Furthermore, while pre-treating cells with ATA failed to inhibit viral replication, pre-incubation of virus with ATA effectively reduced viral titers, suggesting that ATA may elicit its inhibitory effects by directly interacting with the virus. Electron microscopy revealed that ATA induced viral aggregation at the cell surface, prompting us to determine if ATA could inhibit neuraminidase. ATA was found to compromise the activities of virus-derived and recombinant neuraminidase. Moreover, an oseltamivir-resistant H1N1 strain with H274Y was also found to be sensitive to ATA. Finally, we observed additive protective value when infected cells were simultaneously treated with ATA and amantadine hydrochloride, an anti-influenza drug that inhibits M2-ion channels of influenza A virus. Conclusions/Significance Collectively, these data suggest that ATA is a potent anti-influenza agent by directly inhibiting the neuraminidase and could be a more effective antiviral compound when used in combination with amantadine hydrochloride.

Simultaneous quantification of the viral antigens hemagglutinin and neuraminidase in influenza vaccines by LC-MSE.

Current methods for quality control of inactivated influenza vaccines prior to regulatory approval include determining the hemagglutinin (HA) content by single radial immunodiffusion (SRID), verifying neuraminidase (NA) enzymatic activity, and demonstrating that the levels of the contaminant protein ovalbumin are below a set threshold of 1 μg/dose. The SRID assays require the availability of strain-specific reference HA antigens and antibodies, the production of which is a potential rate-limiting step in vaccine development and release, particularly during a pandemic. Immune responses induced by neuraminidase also contribute to protection from infection; however, the amounts of NA antigen in influenza vaccines are currently not quantified or standardized. Here, we report a method for vaccine analysis that yields simultaneous quantification of HA and NA levels much more rapidly than conventional HA quantification techniques, while providing additional valuable information on the total protein content. Enzymatically digested vaccine proteins were analyzed by LC-MS(E), a mass spectrometric technology that allows absolute quantification of analytes, including the HA and NA antigens, other structural influenza proteins and chicken egg proteins associated with the manufacturing process. This method has potential application for increasing the accuracy of reference antigen standards and for validating label claims for HA content in formulated vaccines. It can also be used to monitor NA and chicken egg protein content in order to monitor manufacturing consistency. While this is a useful methodology with potential for broad application, we also discuss herein some of the inherent limitations of this approach and the care and caution that must be taken in its use as a tool for absolute protein quantification. The variations in HA, NA and chicken egg protein concentrations in the vaccines analyzed in this study are indicative of the challenges associated with the current manufacturing and quality control testing procedures.

Antigenic stability of H1N1 pandemic vaccines correlates with vaccine strain.

In 2009 a novel H1N1 influenza virus emerged and spread rapidly. Soon after vaccine lots were released, however, the shelf life was revised downward due to an unexpected decrease in HA potency. In this study, we found differences in both stability and antigenic content of two monovalent H1N1/2009 vaccine preparations. These appear to have arisen due to differences in the A/California/7/2009-like influenza strain used to prepare vaccine.

A monoclonal antibody targeting a highly conserved epitope in influenza B neuraminidase provides protection against drug resistant strains.

All influenza viral neuraminidases (NA) of both type A and B viruses have only one universally conserved sequence located between amino acids 222-230. A monoclonal antibody against this region has been previously reported to provide broad inhibition against all nine subtypes of influenza A NA; yet its inhibitory effect against influenza B viral NA remained unknown. Here, we report that the monoclonal antibody provides a broad inhibition against various strains of influenza B viruses of both Victoria and Yamagata genetic lineage. Moreover, the growth and NA enzymatic activity of two drug resistant influenza B strains (E117D and D197E) are also inhibited by the antibody even though these two mutations are conformationally proximal to the universal epitope. Collectively, these data suggest that this unique, highly-conserved linear sequence in viral NA is exposed sufficiently to allow access by inhibitory antibody during the course of infection; it could represent a potential target for antiviral agents and vaccine-induced immune responses against diverse strains of type B influenza virus.

A Novel Synthetic Receptor-Based Immunoassay for Influenza Vaccine Quantification

Vaccination is the most effective prophylactic method for preventing influenza. Quantification of influenza vaccine antigens is critically important before the vaccine is used for human immunization. Currently the vaccine antigen quantification relies on hemagglutinin content quantification, the key antigenic component, by single radial immunodiffusion (SRID) assay. Due to the inherent disadvantages associated with the traditional SRID; i.e. low sensitivity, low throughput and need for annual reagents, several approaches have been proposed and investigated as alternatives. Yet, most alternative methods cannot distinguish native hemagglutinin from denatured form, making them less relevant to antigenic analyses. Here, we developed a quantitative immunoassay based on the sialic acid binding property of influenza vaccine antigens. Specifically, we chemically synthesized human and avian influenza virus receptors analogues, N-acetylneuraminic acid-2,6-lactose and N-acetylneuraminic acid-2,3-lactose derivatives with an azidopropyl aglycon, using α-2,6- and α-2,3-sialyltransferases, respectively. The azido group of the two sialyllactose-derivatives was reduced and conjugated to mouse serum albumin through a squarate linkage. We showed that the synthetic α-2,6- and α-2,3-receptors selectively bound to human and avian-derived hemagglutinins, respectively, forming the basis of a new, and robust assay for hemagglutinin quantification. Hemagglutinin treated at high temperature or low pH was measured differentially to untreated samples suggesting native conformation is dependent for optimal binding. Importantly, this receptor-based immunoassay showed excellent specificity and reproducibility, high precision, less turnaround time and significantly higher sensitivity and throughput compared with SRID in analyzing multiple influenza vaccines.

Surface modifications of influenza proteins upon virus inactivation by β-propiolactone.

Inactivation of intact influenza viruses using formaldehyde or β‐propiolactone (BPL) is essential for vaccine production and safety. The extent of chemical modifications of such reagents on viral proteins needs to be extensively investigated to better control the reactions and quality of vaccines. We have evaluated the effect of BPL inactivation on two candidate re‐assortant vaccines (NIBRG‐121xp and NYMC‐X181A) derived from A/California/07/2009 pandemic influenza viruses using high‐resolution FT‐ICR MS‐based proteomic approaches. We report here an ultra performance LC MS/MS method for determining full‐length protein sequences of hemagglutinin and neuraminidase through protein delipidation, various enzymatic digestions, and subsequent mass spectrometric analyses of the proteolytic peptides. We also demonstrate the ability to reliably identify hundreds of unique sites modified by propiolactone on the surface of glycoprotein antigens. The location of these modifications correlated with changes to protein folding, conformation, and stability, but demonstrated no effect on protein disulfide linkages. In some cases, these modifications resulted in suppression of protein function, an effect that correlated with the degree of change of the modified amino acids’ side chain length and polarity.

The Universal Epitope of Influenza A Viral Neuraminidase Fundamentally Contributes to Enzyme Activity and Viral Replication

Background: The influenza viral neuraminidase has only one universally conserved peptide sequence with unknown function. Results: Sequence alterations in this region decrease substrate binding, enzymatic activity, protein stability, and viral growth. Conclusion: The universal epitope is indispensable for maximal enzymatic function and robust viral propagation. Significance: The universally conserved NA sequence is an attractive target for antiviral intervention and vaccine development. The only universally conserved sequence among all influenza A viral neuraminidases is located between amino acids 222 and 230. However, the potential roles of these amino acids remain largely unknown. Through an array of experimental approaches including mutagenesis, reverse genetics, and growth kinetics, we found that this sequence could markedly affect viral replication. Additional experiments revealed that enzymes with mutations in this region demonstrated substantially decreased catalytic activity, substrate binding, and thermostability. Consistent with viral replication analyses and enzymatic studies, protein modeling suggests that these amino acids could either directly bind to the substrate or contribute to the formation of the active site in the enzyme. Collectively, these findings reveal the essential role of this unique region in enzyme function and viral growth, which provides the basis for evaluating the validity of this sequence as a potential target for antiviral intervention and vaccine development.

Acetaminophen Modulates the Transcriptional Response to Recombinant Interferon-β

Background Recombinant interferon treatment can result in several common side effects including fever and injection-site pain. Patients are often advised to use acetaminophen or other over-the-counter pain medications as needed. Little is known regarding the transcriptional changes induced by such co-administration. Methodology/Principal Findings We tested whether the administration of acetaminophen causes a change in the response normally induced by interferon-β treatment. CD-1 mice were administered acetaminophen (APAP), interferon-β (IFN-β) or a combination of IFN-β+APAP and liver and serum samples were collected for analysis. Differential gene expression was determined using an Agilent 22 k whole mouse genome microarray. Data were analyzed by several methods including Gene Ontology term clustering and Gene Set Enrichment Analysis. We observed a significant change in the transcription profile of hepatic cells when APAP was co-administered with IFN-β. These transcriptional changes included a marked up-regulation of genes involved in signal transduction and cell differentiation and down-regulation of genes involved in cellular metabolism, trafficking and the IκBK/NF-κB cascade. Additionally, we observed a large decrease in the expression of several IFN-induced genes including Ifit-3, Isg-15, Oasl1, Zbp1 and predicted gene EG634650 at both early and late time points. Conclusions/Significance A significant change in the transcriptional response was observed following co-administration of IFN-β+APAP relative to IFN-β treatment alone. These results suggest that administration of acetaminophen has the potential to modify the efficacy of IFN-β treatment.