A Universal Aptamer for Influenza A Viruses: Selection, Recognition, and Infection Inhibition.

It is crucial to develop universal inhibitors for viral inhibition due to the rapid mutation of viruses. Herein, a universal aptamer inhibitor was developed that enabled a single DNA molecule to recognize several hemeagglutinin (HA) protein subtypes, inducing broad neutralization against influenza A viruses (IAVs). Through a multi-channel enrichment (MCE) strategy, a high-affinity aptamer named UHA-2 was obtained, with its dissociation constants (Kd) for three different HA proteins being 1.5 ± 0.2 nM (H5N1), 3.7 ± 0.4 nM (H7N9), and 10.1 ± 1.1 nM (H9N2). The UHA-2 aptamer had a universal inhibition effect, by which it could broadly neutralize influenza A H5N1, H7N9, H9N2, H1N1, and H3N2 viruses. Universal aptamer inhibitors have the advantages of acquisition in vitro, stability, simple structure, small size, etc. This study not only develops a novel universal aptamer to achieve a broad inhibition effect on various IAVs, but also opens up an efficient strategy for the development of universal inhibitors against viruses.

Newcastle Disease Virus (NDV)-based vaccine candidate against SARS-CoV-2 Omicron by intranasal immunization.

Despite global vaccination efforts, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to evolve and spread globally. Currently, the development of affordable vaccine against Omicron variant of concern (VOC) is necessary. Here, we assessed the safety and immunogenicity of a SARS-CoV-2 vaccine consisting of a live Newcastle disease virus vector expressing the spike (S) protein of Omicron BA.1 administrated intranasally (IN) or intramuscularly (IM) in Golden Syrian hamster model. Immunogenicity studies showed that the prime-boost regimen elicited high antibody titers and the modified S antigen (Sm-F) could induce robust antibody response in low dosage immunization through IN route. Sera of the immunized hamsters provided effective cross-neutralizing activity against different Omicron variants, the prototype and delta strains of SARS-CoV-2. Moreover, the vaccine could provide complete immunoprotection in hamsters against the Omicron BA.1 challenge by either intranasal or intramuscular immunization. Overall, our study provides an alternative nasal vaccine against the SARS-CoV-2 Omicron variants.

Identifying Japanese Encephalitis Virus Using Metatranscriptomic Sequencing, Xinjiang, China.

The treat of infectious disease epidemics has increased the critical need for continuous broad-ranging surveillance of pathogens with outbreak potential. Using metatranscriptomic sequencing of blood samples, we identified several cases of Japanese encephalitis virus infection from Xinjiang Uyghur Autonomous Region, China. This discovery highlights the risk for known viral diseases even in nonendemic areas.

Ecology of avian influenza viruses in migratory birds wintering within the Yangtze River wetlands.

Migratory birds are considered natural reservoirs of avian influenza A viruses (AIVs). To further our viral ecology knowledge and understand the subsequent risk posed by wild birds, we conducted a 4-year surveillance study of AIVs in the bird wintering wetlands of the Yangtze River, China. We collected over 8000 samples and isolated 122 AIV strains. Analyses were then carried out with 108 novel sequenced genomes and data were deposited in GISAID and other public databases. The results showed that the Yangtze River wintering wetlands functioned as a mixing ground, where various subtypes of AIVs were detected harboring a high diversity of nucleotide sequences; moreover, a portion of AIV gene segments were persistent inter-seasonally. Phylogenetic incongruence presented complex reassortment events and distinct patterns among various subtypes. In addition, we observed that viral gene segments in wintering wetlands were closely related to known North American isolates, indicating that intercontinental gene flow occurred. Notably, highly pathogenic H5 and low pathogenic H9 viruses, which usually circulate in poultry, were found to have crossed the poultry/wild bird interface, with the viruses introduced to wintering birds. Overall, this study represented the largest AIV surveillance effort of wild birds within the Yangtze River wintering wetlands. Surveillance data highlighted the important role of wintering wild birds in the ecology of AIVs and may enable future early warnings of novel AIV emergence.

Vaccination with Consensus H7 Elicits Broadly Reactive and Protective Antibodies against Eurasian and North American Lineage H7 Viruses.

H7 subtype avian influenza viruses have caused outbreaks in poultry, and even human infection, for decades in both Eurasia and North America. Although effective vaccines offer the best protection against avian influenza viruses, antigenically distinct Eurasian and North American lineage subtype H7 viruses require the development of cross-protective vaccine candidates. In this study, a methodology called computationally optimized broadly reactive antigen (COBRA) was used to develop four consensus H7 antigens (CH7-22, CH7-24, CH7-26, and CH7-28). In vitro experiments confirmed the binding of monoclonal antibodies to the head and stem domains of cell surface-expressed consensus HAs, indicating display of their antigenicity. Immunization with DNA vaccines encoding the four antigens was evaluated in a mouse model. Broadly reactive antibodies against H7 viruses from Eurasian and North American lineages were elicited and detected by binding, inhibition, and neutralizing analyses. Further infection with Eurasian H7N9 and North American H7N3 virus strains confirmed that CH7-22 and CH7-24 conferred the most effective protection against hetero-lethal challenge. Our data showed that the consensus H7 vaccines elicit a broadly reactive, protective response against Eurasian and North American lineage H7 viruses, which are suitable for development against other zoonotic influenza viruses.

A cross-reactive human monoclonal antibody targets the conserved H7 antigenic site A from fifth wave H7N9-infected humans.

Subtype H7 avian influenza viruses have been found to be associated with human infection and represent a risk for global public health. In 2013, the emergence of H7N9 virus in human beings and persistent human infection in China raised the most serious pandemic threat. Here we identified a human monoclonal antibody, P52E03, targeting the hemagglutinin (HA) of subtype H7 influenza viruses (H7 antigen), from a convalescent patient infected with H7N9 in 2017. P52E03 showed in vitro hemagglutination inhibiting (HI) and neutralizing activity against subtype H7 viruses belonging to both North American and Eurasian lineages. Moreover, it could prophylactically protect mice against weight loss and death caused by challenge with lethal H7N9 viruses in vivo and, therefore, is a candidate for development of antiviral agent against H7N9 infection. By generating escape mutant variants, we found that a single G151E substitution in the viral H7 antigenic site A could abort the neutralizing activity. Computational structural prediction of the P52E03/H7 complex revealed that residues including G151 in and around the conserved antigenic site A region are important for antigen recognition by the H7 cross-reactive antibody. Finally, we found that the P52E03 germline precursor (gHgL) antibody recognizes HA with measurable affinity, suggesting that its epitope is vulnerable to the human immune system and might elicit neutralizing antibodies (nAbs) in vivo after vaccination.

The PA Subunit of the Influenza Virus Polymerase Complex Affects Replication and Airborne Transmission of the H9N2 Subtype Avian Influenza Virus.

The polymerase acidic (PA) protein is the third subunit of the influenza A virus polymerase. In recent years, studies have shown that PA plays an important role in overcoming the host species barrier and host adaptation of the avian influenza virus (AIV). The objective of this study was to elucidate the role of the PA subunit on the replication and airborne transmission of the H9N2 subtype AIV. By reverse genetics, a reassortant rSD01-PA was derived from the H9N2 subtype AIV A/Chicken/Shandong/01/2008 (SD01) by introducing the PA gene from the pandemic influenza A H1N1 virus A/swine/Shandong/07/2011 (SD07). Specific pathogen-free (SPF) chickens and guinea pigs were selected as the animal models for replication and aerosol transmission studies. Results show that rSD01-PA lost the ability of airborne transmission among SPF chickens because of the single substitution of the PA gene. However, rSD01-PA could infect guinea pigs through direct contact, while the parental strain SD01 could not, even though the infection of rSD01-PA could not be achieved through aerosol. In summary, our results indicate that the protein encoded by the PA gene plays a key role in replication and airborne transmission of the H9N2 subtype AIV.

The mRNA and Proteins Expression Levels Analysis of TC-1 Cells Immune Response to H9N2 Avian Influenza Virus.

Since 1994, the H9N2 avian influenza virus (AIV) has spread widely in mainland China, causing great economic losses to the poultry industry there. Subsequently, it was found that the H9N2 AIV had the ability to infect mammals, which gave rise to great panic. In order to investigate the immune response of a host infected with H9N2 AIV, TC-1 cells were set as a model in this research. Quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay methods were used to study the expression changes of pattern recognition receptors (PRRs), inflammatory cytokines, and chemokines in AIV-infected TC-1 cells. Our research found that TC-1 cells had similar susceptibility to both CK/SD/w3 (A/Chicken/Shandong/W3/2012) and CK/SD/w4 (A/Chicken/Shandong/W4/2012) H9N2 isolates, while the CK/SD/w3 isolate had a stronger capability of replication in the TC-1 cells. At the same time, the expression of PRRs (melanoma differentiation-associated gene 5, MDA-5), cytokines [interleukin (IL)-1ß and IL-6], and chemokines [regulated on activation, normal T cell expressed and secreted (RANTES) and interferon-γ-induced protein-10 kDa (IP-10)] were significantly up-regulated. These results indicated that MDA-5, IL-1ß, IL-6, RANTES, and IP-10 might play important roles in the host immune response to H9N2 AIV infection. This study provided useful information for further understanding the interaction between H9N2 virus infection and host immunity, and had certain guiding significance for the prevention and treatment of this disease.