Anti-influenza Hyperimmune Immunoglobulin Enhances Fc-functional Antibody Immunity during Human Influenza Infection

BACKGROUND: New treatments for severe influenza are needed. Passive transfer of influenza-specific hyperimmune pooled immunoglobulin (Flu-IVIG) boosts neutralising antibody responses to past strains in influenza-infected subjects. The effect of Flu-IVIG on antibodies with Fc-mediated functions, which may target diverse influenza strains, is unclear. METHODS: We studied the capacity of Flu-IVIG, relative to standard IVIG, to bind to Fc receptors and mediate antibody-dependent cellular cytotoxicity in vitro. The effect of Flu-IVIG infusion, compared to placebo infusion, was examined in serial plasma samples from 24 subjects with confirmed influenza infection in the INSIGHT FLU005 pilot study. RESULTS: Flu-IVIG contains higher concentrations of Fc-functional antibodies than IVIG against a diverse range of influenza hemagglutinins. Following infusion of Flu-IVIG into influenza-infected subjects, a transient increase in Fc-functional antibodies was present for 1-3 days against infecting and non-infecting strains of influenza. CONCLUSIONS: Flu-IVIG contains antibodies with Fc-mediated functions against influenza virus and passive transfer of Flu-IVIG increases anti-influenza Fc-functional antibodies in the plasma of influenza-infected subjects. Enhancement of Fc-functional antibodies to a diverse range of influenza strains suggests that Flu-IVIG infusion could prove useful in the context of novel influenza virus infections, when there may be minimal or no neutralising antibodies in the Flu-IVIG preparation

Highly pathogenic avian influenza virus infection in chickens but not ducks is associated with elevated host immune and pro-inflammatory responses

Highly pathogenic avian influenza (HPAI) H5N1 viruses cause severe infection in chickens at near complete mortality, but corresponding infection in ducks is typically mild or asymptomatic. To understand the underlying molecular differences in host response, primary chicken and duck lung cells, infected with two HPAI H5N1 viruses and a low pathogenicity avian influenza (LPAI) H2N3 virus, were subjected to RNA expression profiling. Chicken cells but not duck cells showed highly elevated immune and pro-inflammatory responses following HPAI virus infection. HPAI H5N1 virus challenge studies in chickens and ducks corroborated the in vitro findings. To try to determine the underlying mechanisms, we investigated the role of signal transducer and activator of transcription-3 (STAT-3) in mediating pro-inflammatory response to HPAIV infection in chicken and duck cells. We found that STAT-3 expression was down-regulated in chickens but was up-regulated or unaffected in ducks in vitro and in vivo following H5N1 virus infection. Low basal STAT-3 expression in chicken cells was completely inhibited by H5N1 virus infection. By contrast, constitutively active STAT-3 detected in duck cells was unaffected by H5N1 virus infection. Transient constitutively-active STAT-3 transfection in chicken cells significantly reduced pro-inflammatory response to H5N1 virus infection; on the other hand, chemical inhibition of STAT-3 activation in duck cells increased pro-inflammatory gene expression following H5N1 virus infection. Collectively, we propose that elevated pro-inflammatory response in chickens is a major pathogenicity factor of HPAI H5N1 virus infection, mediated in part by the inhibition of STAT-3

A comparative analysis of host responses to avian influenza infection in ducks and chickens highlights a role for the interferon-induced transmembrane proteins in viral resistance

Chickens are susceptible to infection with a limited number of Influenza A viruses and are a potential source of a human influenza pandemic. In particular, H5 and H7 haemagglutinin subtypes can evolve from low to highly pathogenic strains in gallinaceous poultry. Ducks on the other hand are a natural reservoir for these viruses and are able to withstand most avian influenza strains. Results: Transcriptomic sequencing of lung and ileum tissue samples from birds infected with high (H5N1) and low (H5N2) pathogenic influenza viruses has allowed us to compare the early host response to these infections in both these species. Chickens (but not ducks) lack the intracellular receptor for viral ssRNA, RIG-I and the gene for an important RIG-I binding protein, RNF135. These differences in gene content partly explain the differences in host responses to low pathogenic and highly pathogenic avian influenza virus in chicken and ducks. We reveal very different patterns of expression of members of the interferon-induced transmembrane protein (IFITM) gene family in ducks and chickens. In ducks, IFITM1, 2 and 3 are strongly up regulated in response to highly pathogenic avian influenza, where little response is seen in chickens. Clustering of gene expression profiles suggests IFITM1 and 2 have an anti-viral response and IFITM3 may restrict avian influenza virus through cell membrane fusion. We also show, through molecular phylogenetic analyses, that avian IFITM1 and IFITM3 genes have been subject to both episodic and pervasive positive selection at specific codons. In particular, avian IFITM1 showed evidence of positive selection in the duck lineage at sites known to restrict influenza virus infection. Conclusions: Taken together these results support a model where the IFITM123 protein family and RIG-I all play a crucial role in the tolerance of ducks to highly pathogenic and low pathogenic strains of avian influenza viruses when compared to the chicken

Inducible Bronchus-Associated Lymphoid Tissues (iBALT) Serve as Sites of B Cell Selection and Maturation Following Influenza Infection in Mice

Seasonally recurrent influenza virus infections are a significant cause of global morbidity and mortality. In murine models, primary influenza infection in the respiratory tract elicits potent humoral responses concentrated in the draining mediastinal lymph node and the spleen. In addition to immunity within secondary lymphoid organs (SLO), pulmonary infection is also associated with formation of ectopic inducible bronchus-associated tissues (iBALT) in the lung. These structures display a lymphoid organization, but their function and protective benefits remain unclear. Here we examined the phenotype, transcriptional profile and antigen specificity of B cell populations forming iBALT in influenza infected mice. We show that the cellular composition of iBALT was comparable to SLO, containing populations of follicular dendritic cells (FDC), T-follicular helper (Tfh) cells, and germinal center (GC)-like B cells with classical dark- and light-zone polarization. Transcriptional profiles of GC B cells in iBALT and SLO were conserved regardless of anatomical localization. The architecture of iBALT was pleiomorphic and less structurally defined than SLO. Nevertheless, we show that GC-like structures within iBALT serve as a distinct niche that independently support the maturation and selection of B cells primarily targeted against the influenza virus nucleoprotein. Our findings suggest that iBALT, which are positioned at the frontline of the lung mucosa, drive long-lived, and unique GC reactions that contribute to the diversity of the humoral response targeting influenza

Antibody Responses with Fc-Mediated Functions after Vaccination of HIV-Infected Subjects with Trivalent Influenza Vaccine

UNLABELLED: This study seeks to assess the ability of seasonal trivalent inactivated influenza vaccine (TIV) to induce nonneutralizing antibodies (Abs) with Fc-mediated functions in HIV-uninfected and HIV-infected subjects. Functional influenza-specific Ab responses were studied in 30 HIV-negative and 27 HIV-positive subjects immunized against seasonal influenza. All 57 subjects received the 2015 TIV. Fc-mediated antihemagglutinin (anti-HA) Ab activity was measured in plasma before and 4 weeks after vaccination using Fc-receptor-binding assays, NK cell activation assays, and phagocytosis assays. At baseline, the HIV-positive group had detectable but reduced functional Ab responses to both vaccine and nonvaccine influenza antigens. TIV enhanced Fc-mediated Ab responses in both HIV-positive and HIV-negative groups. A larger rise was generally observed in the HIV-positive group, such that there was no difference in functional Ab responses between the two groups after vaccination. The 2015 TIV enhanced functional influenza-specific Ab responses in both HIV-negative and HIV-positive subjects to a range of influenza HA proteins. The increase in functional Ab responses in the HIV-positive group supports recommendations to immunize this at-risk group. IMPORTANCE: Infection with HIV is associated with increasing disease severity following influenza infections, and annual influenza vaccinations are recommended for this target group. However, HIV-infected individuals respond relatively poorly to vaccination compared to healthy individuals, particularly if immunodeficient. There is therefore a need to increase our understanding of immunity to influenza in the context of underlying HIV infection. While antibodies can mediate direct virus neutralization, interactions with cellular Fc receptors may be important for anti-influenza immunity in vivo by facilitating antibody-dependent cellular cytotoxicity (ADCC) and/or antibody-dependent phagocytosis (ADP). The ability of seasonal influenza vaccines to induce antibody responses with potent Fc-mediated antiviral activity is currently unclear. Probing the ADCC and ADP responses to influenza vaccination has provided important new information in the quest to improve immunity to influenza