Characterization of Novel Cross-Reactive Influenza B Virus Hemagglutinin Head Specific Antibodies That Lack Hemagglutination Inhibition Activity

HA antigenic variation and phylogenetic analysis of influenza B virus in Shiraz, Iran

BACKGROUND

Influenza infection is highly contagious respiratory illness triggered by the influenza virus, bearing substantial implications for global health. Influenza B viruses, specifically the Victoria and Yamagata lineages, have contributed to the disease burden, and the mismatch between circulating strains and vaccine strains has led to increased mortality and economic costs. Understanding the global epidemiology, seasonal variations, and genetic characteristics of influenza B is crucial for effective prevention and control strategies.

METHODS

The study investigated influenza B viruses in Shiraz, Iran during the Oct 2017 to Jan 2018. Throat swabs were collected from 235 individuals under 15 with influenza-like symptoms including fever and cough. Samples were stored at -80°C and transported to the lab for further analysis. Viral RNA was extracted and analyzed using Real-time PCR. The hemagglutinin (HA) gene of positive samples was sequenced, and phylogenetic trees were constructed. Amino acids indicative of adaptive mutations were identified using global sequence data.

RESULTS

23 of 235 samples (9.7 %) were positive for influenza B virus. The most common clinical manifestations were rhinorrhea and myalgia, with 20 individuals (87 % of the 23 infected people) each showing these symptoms. The phylogenetic analysis of the HA gene showed that the Victoria isolates were close to the B/Brisbane/60/2008 strain (12.5 % of the positive samples) and belonged to clade-1A, while the Yamagata isolates were close to the B/Phuket/3037/2013 strain (87.5 % of the positive samples) and belonged to clade-3.

CONCLUSION

The study highlights the need for importance vaccine coverage in the Shiraz region to address limited genetic diversity and strain mismatch. Continuous surveillance of mutations in the HA gene resulting in amino acid substitutions and their impact on vaccine efficacy is crucial. This study showed that the circulation of influenza B in Shiraz matched with the recommended Yamagata vaccine strain. These findings contribute to the understanding of influenza B dynamics and emphasize the importance of region-specific prevention and control strategies.

Substitutions near the HA receptor binding site explain the origin and major antigenic change of the B/Victoria and B/Yamagata lineages

Influenza B virus primarily infects humans, causing seasonal epidemics globally. Two antigenic variants-Victoria-like and Yamagata-like-were detected in the 1980s, of which the molecular basis of emergence is still incompletely understood. Here, the antigenic properties of a unique collection of historical virus isolates, sampled from 1962 to 2000 and passaged exclusively in mammalian cells to preserve antigenic properties, were determined with the hemagglutination inhibition assay and an antigenic map was built to quantify and visualize the divergence of the lineages. The antigenic map revealed only three distinct antigenic clusters-Early, Victoria, and Yamagata-with relatively little antigenic diversity in each cluster until 2000. Viruses with Victoria-like antigenic properties emerged around 1972 and diversified subsequently into two genetic lineages. Viruses with Yamagata-like antigenic properties evolved from one lineage and became clearly antigenically distinct from the Victoria-like viruses around 1988. Recombinant mutant viruses were tested to show that insertions and deletions (indels), as observed frequently in influenza B virus hemagglutinin, had little effect on antigenic properties. In contrast, amino-acid substitutions at positions 148, 149, 150, and 203, adjacent to the hemagglutinin receptor binding site, determined the main antigenic differences between the Early, Victoria-like, and Yamagata-like viruses. Surprisingly, substitutions at two of the four positions reverted in recent viruses of the Victoria lineage, resulting in antigenic properties similar to viruses circulating ∼50 y earlier. These data shed light on the antigenic diversification of influenza viruses and suggest there may be limits to the antigenic evolution of influenza B virus.

Functionality of the putative surface glycoproteins of the Wuhan spiny eel influenza virus

A panel of influenza virus-like sequences were recently documented in fish and amphibians. Of these, the Wuhan spiny eel influenza virus (WSEIV) was found to phylogenetically cluster with influenza B viruses as a sister clade. Influenza B viruses have been documented to circulate only in humans, with certain virus isolates found in harbor seals. It is therefore interesting that a similar virus was potentially found in fish. Here we characterize the putative hemagglutinin (HA) and neuraminidase (NA) surface glycoproteins of the WSEIV. Functionally, we show that the WSEIV NA-like protein has sialidase activity comparable to B/Malaysia/2506/2004 influenza B virus NA, making it a bona fide neuraminidase that is sensitive to NA inhibitors. We tested the functionality of the HA by addressing the receptor specificity, stability, preferential airway protease cleavage, and fusogenicity. We show highly specific binding to monosialic ganglioside 2 (GM2) and fusogenicity at a range of different pH conditions. In addition, we found limited antigenic conservation of the WSEIV HA and NA relative to the B/Malaysia/2506/2004 virus HA and NA. In summary, we perform a functional and antigenic characterization of the glycoproteins of WSEIV to assess if it is indeed a bona fide influenza virus potentially circulating in ray-finned fish.

Requirement of Fc-Fc Gamma Receptor Interaction for Antibody-Based Protection against Emerging Virus Infections

Identification of therapeutics against emerging and re-emerging viruses remains a continued priority that is only reinforced by the recent SARS-CoV-2 pandemic. Advances in monoclonal antibody (mAb) isolation, characterization, and production make it a viable option for rapid treatment development. While mAbs are traditionally screened and selected based on potency of neutralization in vitro, it is clear that additional factors contribute to the in vivo efficacy of a mAb beyond viral neutralization. These factors include interactions with Fc receptors (FcRs) and complement that can enhance neutralization, clearance of infected cells, opsonization of virions, and modulation of the innate and adaptive immune response. In this review, we discuss recent studies, primarily using mouse models, that identified a role for Fc-FcγR interactions for optimal antibody-based protection against emerging and re-emerging virus infections.