Efficacy of novel recombinant fowlpox vaccine against recent Mexican H7N3 highly pathogenic avian influenza virus

Since 2012, H7N3 highly pathogenic avian influenza (HPAI) has produced negative economic and animal welfare impacts on poultry in central Mexico. In the present study, chickens were vaccinated with two different recombinant fowlpox virus vaccines (rFPV-H7/3002 with 2015 H7 hemagglutinin [HA] gene insert, and rFPV-H7/2155 with 2002 H7 HA gene insert), and were then challenged three weeks later with H7N3 HPAI virus (A/chicken/Jalisco/CPA-37905/2015). The rFPV-H7/3002 vaccine conferred 100% protection against mortality and morbidity, and significantly reduced virus shed titers from the respiratory and gastrointestinal tracts. In contrast, 100% of sham and rFPV-H7/2155 vaccinated birds shed virus at higher titers and died within 4?days. Pre- (15/20) and post- (20/20) challenge serum of birds vaccinated with rFPV-H7/3002 had antibodies detectable by hemagglutination inhibition (HI) assay using challenge virus antigen. However, only a few birds (3/20) in the rFPV-H7/2155 vaccinated group had antibodies that reacted against the challenge strain but all birds had antibodies that reacted against the homologous vaccine antigen (A/turkey/Virginia/SEP-66/2002) (20/20). One possible explanation for differences in vaccines efficacy is the antigenic drift between circulating viruses and vaccines. Molecular analysis demonstrated that the Mexican H7N3 strains have continued to rapidly evolve since 2012. In addition, we identified in silico three potential new N-glycosylation sites on the globular head of the H7 HA of A/chicken/Jalisco/CPA-37905/2015 challenge virus, which were absent in 2012 H7N3 outbreak virus. Our results suggested that mutations in the HA antigenic sites including increased glycosylation sites, accumulated in the new circulating Mexican H7 HPAIV strains, altered the recognition of neutralizing antibodies from the older vaccine strain rFPV-H7/2155. Therefore, the protective efficacy of novel rFPV-H7/3002 against recent outbreak Mexican H7N3 HPAIV confirms the importance of frequent updating of vaccines seed strains for long-term effective control of H7 HPAI virus.     

Reduced serologic sensitivity to influenza A virus illness among inactivated influenza vaccinees

We compared ≥4-fold increases in antibody titers by hemagglutination inhibition assay to RT-PCR results among 42 adults with PCR-confirmed influenza A virus illnesses. Serologic sensitivity was higher among unvaccinated (69%, 95% confidence interval [CI] = 48–90%) than vaccinated healthcare personnel (38%, 95% CI = 29–46%) in a 2010–11 prospective cohort.     

流感病毒血凝素在多种系统中表达的研究进展

流感疫苗是预防流感病毒感染最有效的方法。传统灭活流感疫苗通过在鸡胚中培养病毒后经纯化获得。流感每年都会发生季节性流行,流感病毒高度多变的特性使生产有效疫苗成为一项挑战。为了克服流感疫苗生产对鸡胚的依赖,需要开发新的流感疫苗生产策略。由于血凝素是流感病毒主要表面抗原之一,重组血凝素亚单位疫苗为流感疫苗的生产提供了一个方案。本文将对流感病毒血凝素在大肠埃希菌、毕赤酵母、昆虫细胞、哺乳动物细胞多种系统中表达的研究进行综述。     

Protective immunity to H7N9 influenza viruses elicited by synthetic DNA vaccine

Despite an intensive vaccine program influenza infections remain a major health problem, due to the viruses’ ability to change its envelope glycoprotein hemagglutinin (HA), through shift and drift, permitting influenza to escape protection induced by current vaccines or natural immunity. Recently a new variant, H7N9, has emerged in China causing global concern. First, there have been more than 130 laboratory-confirmed human infections resulting in an alarmingly high death rate (32.3%). Second, genetic changes found in H7N9 appear to be associated with enabling avian influenza viruses to spread more effectively in mammals, thus transmitting infections on a larger scale. Currently, no vaccines or drugs are effectively able to target H7N9. Here, we report the rapid development of a synthetic consensus DNA vaccine (pH7HA) to elicit potent protective immunity against the H7N9 viruses. We show that pH7HA induces broad antibody responses that bind to divergent HAs from multiple new members of the H7N9 family. These antibody responses result in high-titer HAI against H7N9. Simultaneously, this vaccine induces potent polyfunctional effector CD4 and CD8T cell memory responses. Animals vaccinated with pH7HA are completely protected from H7N9 virus infection and any morbidity associated with lethal challenge. This study establishes that this synthetic consensus DNA vaccine represents a new tool for targeting emerging infection, and more importantly, its design, testing and development into seed stock for vaccine production in a few days in the pandemic setting has significant implications for the rapid deployment of vaccines protecting against emerging infectious diseases.     

Spread of predominant neuraminidase and hemagglutinin co-mutations in the influenza A/H3N2 virus genome

Genetic variation of influenza neuraminidase (NA), unlike for hemagglutinin (HA), has not been fully characterized. Therefore, we determined the relation between mutations in the NA and HA genome segments of 205 influenza A/H3N2 viruses isolated from patients in Japan during the five seasons from 2010 to 2015. The amino acid (AA) sequences of the NA and HA proteins in these isolates were then determined. In the 2011–2012 season, there was the emergence of isolates with NA and HA sequences containing AA93G (NA93G) and AA278K (HA278K), respectively (24/48 isolates, 50.0%). This was in contrast to NA93D-HA278N being detected exclusively in the previous 2010–2011 season (24/24 isolates, 100.0%). The isolates with the NA93G-HA278K substitutions became predominant in the following 2012–2013 season (95.8%, 46/48 isolates). The NA and HA phylogenetic trees of the 2011–2012 and 2012–2013 seasons were segregated by clades with NA93D-HA278N or NA93G-HA278K. In the subsequent 2013–2014 and 2014–2015 seasons, the strong relationship between NA93D-HA278N and NA93G-HA278K observed in the previous seasons, was no longer present and NA93G-HA278N (33/52 isolates, 63.5% in the 2014–2015 season) became predominant. In addition, the clades within the NA and HA trees could no longer be segregated based on NA AA93 and HA AA278. These findings suggest that the co-mutation of NA and HA AA sequences is present and may contribute to the formation of an epidemic lineage.     

成都市2009年流感病毒H3N2亚型血凝素基因分析

[目的]了解某市流行的H3N2流感病毒分子生物学特征、进化情况,及其血凝素基因与猪流感病毒血凝素基因的关系。[方法]对该市分离的2009年H3N2亚型流感病毒40株血凝素基因进行逆转录-聚合酶链(RT-PCR)扩增,然后测序,分析该市流感病毒H3N2亚型的核酸序列和氨基酸序列,与2009年疫苗推荐株及四川省猪流感病毒基因序列比对分析。[结果]该市2009年流感病毒H3N2亚型的流行株,与2009年的疫苗株比较,碱基同源性为99.5%,抗原性有一定的差异,但不是重组变异病毒,其流行强度有限。与A/swine//Sichuan/1/2006(H3N2)比较,同源性为94.4%,说明人源流感病毒A/H3N2与猪源流感病毒A/H3N2具有一定的同源性,但抗原决定簇区和受体结合位点具有差异,在种间互相流行的可能性较低。[结论]该市流感A/H3N2流行株虽然有一定的变异,但没有大流行的预警提示出现。长期监测具有必要性。     

Trypsin pre-treatment corrects SRID over-estimation of immunologically active,pre-fusion HA caused by mixed immunoprecipitin rings

Influenza vaccines are the primary intervention to prevent the substantial health burden of seasonal and pandemic influenza. Subunit and split influenza vaccines are formulated, released for clinical use, and tested for stability based on their content of immunologically active (capable of eliciting functional antibodies) hemagglutinin (HA). Single-radial immunodiffusion (SRID), the standard in vitro potency assay in the field, is believed to specifically detect immunologically active HA. We confirmed that, with conformationally homogeneous HA preparations, SRID specifically detected native, pre-fusion HA, which elicited influenza neutralizing and hemagglutination inhibiting (HI) antibodies in mice, and it did not detect low-pH stressed, post-fusion HA, which was selectively removed from the SRID gel during a blotting step and was significantly less immunologically active. This selective detection was due to the SRID format, not a conformational specificity of the sheep antiserum used in the SRID, as the same antiserum detected non-stressed and low-pH stressed HA similarly when used in an ELISA format. However, when low-pH stressed HA was mixed with non-stressed HA, SRID detected both forms in mixed immunoprecipitin rings, leading to over-quantification of pre-fusion HA. We previously reported that trypsin digestion of antigen samples selectively degrade stressed HA, so that an otherwise conformationally insensitive biophysical quantification technique, reversed-phase high pressure liquid chromatography (RP-HPLC), can specifically quantify trypsin-resistant, immunologically active, pre-fusion HA. Here, we report that trypsin digestion can also improve the specificity of SRID so that it can quantify immunologically active, pre-fusion HA when it is mixed with less immunologically active, post-fusion HA.     

The vaccinia virus fusion inhibitor proteins SPI-3 (K2) and HA (A56) expressed by infected cells reduce the entry of superinfecting virus

The orthopoxvirus SPI-3 (K2) and A56 (hemagglutinin, HA) proteins interact and together prevent cell–cell fusion. SPI-3/A56 has been proposed to prevent the superinfection of previously infected cells by reducing virus–cell fusion. Binding of mature virions of vaccinia virus (VV) to VV-infected cells was unaffected by SPI-3 or A56 on the surface of infected cells. Entry of VV into infected cells was assessed using VV-P_T7-luc carrying the luciferase reporter under T7 control. Cells infected with VV or cowpox virus (CPV) expressing T7 RNA polymerase and lacking SPI-3 and/or A56 were superinfected with VV-P_T7-luc, and luciferase activity was measured. Inactivation of SPI-3 or A56 from the pre-infecting virus resulted in greater luciferase expression from the superinfecting VV-P_T7-luc. Antibody against SPI-3 present during infection with wild-type CPV-T7 increased luciferase expression from superinfecting VV-P_T7-luc. The SPI-3/A56 complex on the infected cell surface therefore appears to reduce the entry of virions into infected cells.