Phase II,randomized, open,controlled study of AS03‐adjuvanted H5N1 pre‐pandemic influenza vaccine in children aged 3 to 9 years: follow‐up of safety and immunogenicity persistence at 24 months post‐vaccination

Background

An AS03-adjuvanted H5N1 influenza vaccine elicited broad and persistent immune responses with an acceptable safety profile up to 6 months following the first vaccination in children aged 3–9 years.

Methods

In this follow-up of the Phase II study, we report immunogenicity persistence and safety at 24 months post-vaccination in children aged 3–9 years. The randomized, open-label study assessed two doses of H5N1 A/Vietnam/1194/2004 influenza vaccine (1·9 μg or 3·75 μg hemagglutinin antigen) formulated with AS03_A or AS03_B (11·89 mg or 5·93 mg tocopherol, respectively). Control groups received seasonal trivalent influenza vaccine. Safety was assessed prospectively and included potential immune-mediated diseases (pIMDs). Immunogenicity was assessed by hemagglutination-inhibition assay 12 and 24 months after vaccination; cross-reactivity and cell-mediated responses were also assessed. ({"type":"clinical-trial","attrs":{"text":"NCT00502593","term_id":"NCT00502593"}}NCT00502593).

Results

The safety population included 405 children. Over 24 months, five events fulfilled the criteria for pIMDs, of which four occurred in H5N1 vaccine recipients, including uveitis (n = 1) and autoimmune hepatitis (n = 1), which were considered to be vaccine-related. Overall, safety profiles of the vaccines were clinically acceptable. Humoral immune responses at 12 and 24 months were reduced versus those observed after the second dose of vaccine, although still within the range of those observed after the first dose. Persistence of cell-mediated immunity was strong, and CD4⁺ T cells with a T_H1 profile were observed.

Conclusions

Two doses of an AS03-adjuvanted H5N1 influenza vaccine in children showed low but persistent humoral immune responses and a strong persistence of cell-mediated immunity, with clinically acceptable safety profiles up to 24 months following first vaccination.     

HIV virological suppression influences response to the AS03‐adjuvanted monovalent pandemic influenza A H1N1 vaccine in HIV‐infected children

Design

Children with HIV are especially susceptible to complications from influenza infection, and effective vaccines are central to reducing disease burden in this population. We undertook a prospective, observational study to investigate the safety and immunogenicity of the inactivated split-virion AS03-adjuvanted pandemic H1N1(2009) vaccine in children with HIV.

Setting

National referral centre for Paediatric HIV in Ireland.

Sample

Twenty four children with HIV were recruited consecutively and received two doses of the vaccine. The serological response was measured before each vaccine dose (Day 0 and Day 28) and 2 months after the booster dose. Antibody titres were measured using a haemagglutination inhibition (HAI) assay. Seroprotection was defined as a HAI titre ≥ 1:40; seroconversion was defined as a ≥ fourfold increase in antibody titre and a postvaccination titre ≥ 1:40.

Main outcome measures

The seroconversion rates after prime and booster doses were 75% and 71%, respectively. HIV virological suppression at the time of immunization was associated with a significantly increased seroconversion rate (P = 0·009), magnitude of serological response (P = 0·02) and presence of seroprotective HAI titres (P = 0·017) two months after the booster dose. No other factor was significantly associated with the seroconversion/seroprotection rate. No serious adverse effects were reported. Vaccination had no impact on HIV disease progression. The AS03-adjuvanted pandemic H1N1 vaccine appears to be safe and immunogenic among HIV-infected children. A robust serological response appears to be optimized by adherence to a HAART regimen delivering virological suppression.     

Live attenuated H5N1 vaccine with H9N2 internal genes protects chickens from infections by both Highly Pathogenic H5N1 and H9N2 Influenza Viruses

Please cite this paper as: Nang et al. (2013) Live attenuated H5N1 vaccine with H9N2 internal genes protects chickens from infections by both Highly Pathogenic H5N1 and H9N2 Influenza Viruses. Influenza and Other Respiratory Viruses 7(2) 120–131. Background The highly pathogenic H5N1 and H9N2 influenza viruses are endemic in many countries around the world and have caused considerable economic loss to the poultry industry. Objectives We aimed to study whether a live attenuated H5N1 vaccine comprising internal genes from a cold‐adapted H9N2 influenza virus could protect chickens from infection by both H5N1 and H9N2 viruses. Methods We developed a cold‐adapted H9N2 vaccine virus expressing hemagglutinin and neuraminidase derived from the highly pathogenic H5N1 influenza virus using reverse genetics. Results and Conclusions Chickens immunized with the vaccine were protected from lethal infections with homologous and heterologous H5N1 or H9N2 influenza viruses. Specific antibody against H5N1 virus was detected up to 11 weeks after vaccination (the endpoint of this study). In vaccinated chickens, IgA and IgG antibody subtypes were induced in lung and intestinal tissue, and CD4+ and CD8+ T lymphocytes expressing interferon‐gamma were induced in the splenocytes. These data suggest that a live attenuated H5N1 vaccine with cold‐adapted H9N2 internal genes can protect chickens from infection with H5N1 and H9N2 influenza viruses by eliciting humoral and cellular immunity.     

H5N1 Virus Evolution in Europe-An Updated Overview

Since its emergence in South East Asia in 2003, Highly Pathogenic Avian Influenza (HPAI) A/H5N1 has reportedly caused outbreaks in poultry and/or wild birds in 62 countries, of which 24 were in Europe. Interestingly, out of the many genetic clades circulating in Asia, the westward spread of HPAI A/H5N1 to Central Asia, the Middle East, Europe and Africa was dominated by one single clade, namely clade 2.2. In this paper, we review and update through phylogenetic and gene migrational analysis the information concerning the evolution and the molecular epidemiology of HPAI A/H5N1 on the European continent.     

Safety and immunogenicity of Sinovac’s prototype pandemic influenza H5N1 vaccines: a review on clinical trials

Abstract  Sinovac Biotech started to develop prototype pandemic influenza H5N1 vaccines in March 2004. On 2 April 2008, Sinovac’s inactivated, aluminium‐adjuvanted, whole‐virion prototype pandemic influenza A (H5N1) vaccine (PanFlu™) was granted production licensure by the China regulatory authority State Food and Drug Administration. The whole‐virion H5N1 vaccine was manufactured in embryonated hens’ eggs using the reassortant strain NIBRG‐14 (A/Vietnam/1194/2004‐A/PR/8/34) as vaccine virus. It showed good safety, immunogenicity and cross‐reactivity in immunologically naïve adults. In primed adults, the vaccine induced a strong booster response. Plasma from a vaccinated individual showed a beneficial effect following passive immunotherapy of an H5N1 human infection case. This article reviews the process, status and results of clinical evaluation of Sinovac’s whole‐ and split‐virion H5N1 vaccines by focusing on the whole‐virion vaccine.     

Development of a new candidate H5N1 avian influenza virus for pre‐pandemic vaccine production

Background Highly pathogenic H5N1 avian influenza viruses currently circulating in birds have caused hundreds of human infections, and pose a significant pandemic threat. Vaccines are a major component of the public health preparedness for this likely event. The rapid evolution of H5N1 viruses has resulted in the emergence of multiple clades with distinct antigenic characteristics that require clade‐specific vaccines. A variant H5N1 virus termed clade 2.3.4 emerged in 2005 and has caused multiple fatal infections. Vaccine candidates that match the antigenic properties of variant viruses are necessary because inactivated influenza vaccines elicit strain‐specific protection. Objective To address the need for a suitable seed for manufacturing a clade 2.3.4 vaccine, we developed a new H5N1 pre‐pandemic candidate vaccine by reverse genetics and evaluated its safety and replication in vitro and in vivo. Methods A reassortant virus termed, Anhui/PR8, was produced by reverse genetics in compliance with WHO pandemic vaccine development guidelines and contains six genes from A/Puerto Rico/8/34 as well as the neuraminidase and hemagglutinin (HA) genomic segments from the A/Anhui/01/2005 virus. The multi‐basic cleavage site of HA was removed to reduce virulence. Results The reassortant Anhui/PR8 grows well in eggs and is avirulent to chicken and ferrets but retains the antigenicity of the parental A/Anhui/01/2005 virus. Conclusion These results indicate that the Anhui/PR8 reassortant lost a major virulent determinant and it is suitable for its use in vaccine manufacturing and as a reference vaccine virus against the H5N1 clade 2.3.4 viruses circulating in eastern China, Vietnam, Thailand, and Laos.     

Immunization with 1976 swine H1N1- or 2009 pandemic H1N1-inactivated vaccines protects mice from a lethal 1918 influenza infection

Please cite this paper as: Easterbrook et al. (2011) Immunization with 1976 swine H1N1‐ or 2009 pandemic H1N1‐inactivated vaccines protects mice from a lethal 1918 influenza infection. Influenza and Other Respiratory Viruses DOI: 10.1111/j.1750‐2659.2010.00191.x. Background Zoonotic infections with H1N1 influenza viruses that evolved initially from the 1918 virus (1918) and adapted to swine threatened a pandemic in 1976 (1976 swH1N1) and a novel reassortant H1N1 virus caused a pandemic in 2009–2010 (2009 pH1N1). Epidemiological and laboratory animal studies show that protection from severe 2009 pH1N1 infection is conferred by vaccination or prior infection with 1976 swH1N1 or 1918. Objectives Our aim was to demonstrate cross‐protection by immunization with 2009 pH1N1 or 1976 swH1N1 vaccines following a lethal challenge with 1918. Further, the mechanisms of cross‐protective antibody responses were evaluated. Methods Mice were immunized with 1976 swH1N1, 2009 pH1N1, 2009 seasonal trivalent, or 1918 vaccines and challenged with 1918. Cross‐reactive antibody responses were assessed and protection monitored by survival, weight loss, and pathology in mice. Results and Conclusions Vaccination with the 1976 swH1N1 or 2009 pH1N1 vaccines protected mice from a lethal challenge with 1918, and these mice lost no weight and had significantly reduced viral load and pathology in the lungs. Protection was likely due to cross‐reactive antibodies detected by microneutralization assay. Our data suggest that the general population may be protected from a future 1918‐like pandemic because of prior infection or immunization with 1976 swH1N1 or 2009 pH1N1. Also, influenza protection studies generally focus on cross‐reactive hemagglutination‐inhibiting antibodies; while hemagglutinin is the primary surface antigen, this fails to account for other influenza viral antigens. Neutralizing antibody may be a better correlate of human protection against pathogenic influenza strains and should be considered for vaccine efficacy.     

Influenza A H1N1 in HIV-infected adults

Objectives

HIV‐infected adults are considered to be at higher risk for influenza A H1N1 complications but data supporting this belief are lacking. We aimed to compare epidemiological data, clinical characteristics, and outcomes of influenza A H1N1 infection between HIV‐infected and ‐uninfected adults.

Methods

From 26 April to 6 December 2009, each adult presenting with acute respiratory illness at the emergency department of our institution was considered for an influenza A H1N1 diagnosis by specific multiplex real‐time polymerase chain reaction. For every HIV‐infected adult diagnosed, three consecutive adults not known to be HIV‐infected diagnosed in the same calendar week were randomly chosen as controls.

Results

Among 2106 adults tested, 623 (30%) had influenza A H1N1 infection confirmed. Fifty‐six (9%) were HIV‐positive and were compared with 168 HIV‐negative controls. Relative to HIV‐negative controls, HIV‐positive patients were older, more frequently male, and more frequently smokers (P≤0.02). In the HIV‐positive group, prior or current AIDS‐defining events were reported for 30% of patients, 9% and 30% had CD4 counts of <200 and 200–500 cells/μL, respectively, and 95% had HIV‐1 RNA <50 copies/mL. Pneumonia (9%vs. 25%, respectively, in the HIV‐positive and HIV‐negative groups; P=0.01) and respiratory failure (9%vs. 21%, respectively; P=0.04) were less common in the HIV‐positive group. Oseltamivir (95%vs. 71% in the HIV‐positive and HIV‐negative groups, respectively; P=0.003) was administered more often in HIV‐positive patients. Three patients (all HIV‐negative) died. In the HIV‐positive group, CD4 cell count and plasma HIV‐1 RNA did not differ before and 4–6 weeks after influenza A H1N1 diagnosis (P>0.05).

Conclusions

HIV infection did not increase the severity of influenza A H1N1 infection, and influenza A H1N1 infection did not have a major effect on HIV infection.     

A sensitive retroviral pseudotype assay for influenza H5N1‐neutralizing antibodies

Background The World Health Organisation (WHO) recommended the development of simple, safe, sensitive and specific neutralization assays for avian influenza antibodies. We have used retroviral pseudotypes bearing influenza H5 hemagglutinin (HA) as safe, surrogate viruses for influenza neutralization assays which can be carried out at Biosafety Level 2. Results Using our assay, sera from patients who had recovered from infection with influenza H5N1, and sera from animals experimentally immunized or infected with H5 tested positive for the presence of neutralizing antibodies to H5N1. Pseudotype neutralizing antibody titers were compared with titers obtained by hemagglutinin inhibition (HI) assays and microneutralization (MN) assays using live virus, and showed a high degree of correlation, sensitivity and specificity. Conclusions The pseudotype neutralization assay is as sensitive as horse erythrocyte HI and MN for the detection of antibodies to H5N1. It is safer, and can be applied in a high‐throughput format for human and animal surveillance and for the evaluation of vaccines.     

Ducks: The “Trojan Horses” of H5N1 influenza

Abstract Wild ducks are the main reservoir of influenza A viruses that can be transmitted to domestic poultry and mammals, including humans. Of the 16 hemagglutinin (HA) subtypes of influenza A viruses, only the H5 and H7 subtypes cause highly pathogenic (HP) influenza in the natural hosts. Several duck species are naturally resistant to HP Asian H5N1 influenza viruses. These duck species can shed and spread virus from both the respiratory and intestinal tracts while showing few or no disease signs. While the HP Asian H5N1 viruses are 100% lethal for chickens and other gallinaceous poultry, the absence of disease signs in some duck species has led to the concept that ducks are the “Trojan horses” of H5N1 in their surreptitious spread of virus. An important unresolved issue is whether the HP H5N1 viruses are maintained in the wild duck population of the world. Here, we review the ecology and pathobiology of ducks infected with influenza A viruses and ducks’ role in the maintenance and spread of HP H5N1 viruses. We also identify the key questions about the role of ducks that must be resolved in order to understand the emergence and control of pandemic influenza. It is generally accepted that wild duck species can spread HP H5N1 viruses, but there is insufficient evidence to show that ducks maintain these viruses and transfer them from one generation to the next.     

From the Cover: Adjuvanted H5N1 vaccine induces early CD4+ T cell response that predicts long-term persistence of protective antibody levels

Immune responses to vaccination are tested in clinical trials. This process usually requires years especially when immune memory and persistence are analyzed. Markers able to quickly predict the immune response would be very useful, particularly when dealing with emerging diseases that require a rapid response, such as avian influenza. To address this question we vaccinated healthy adults at days 1, 22, and 202 with plain or MF59-adjuvanted H5N1 subunit vaccines and tested both cell-mediated and antibody responses up to day 382. Only the MF59-H5N1 vaccine induced high titers of neutralizing antibodies, a large pool of memory H5N1-specific B lymphocytes, and H5-CD4⁺ T cells broadly reactive with drifted H5. The CD4⁺ response was dominated by IL-2⁺ IFN-γ⁻ IL-13⁻ T cells. Remarkably, a 3-fold increase in the frequency of virus-specific total CD4⁺ T cells, measurable after 1 dose, accurately predicted the rise of neutralizing antibodies after booster immunization and their maintenance 6 months later. We suggest that CD4⁺ T cell priming might be used as an early predictor of the immunogenicity of prepandemic vaccines.     

Long‐term vaccine‐induced heterologous protection against H5N1 influenza viruses in the ferret model

Please cite this paper as: Ducatez et al. (2012) Long‐term vaccine‐induced heterologous protection against H5N1 influenza viruses in the ferret model. Influenza and Other Respiratory Viruses 7(4), 506–512. Background Highly pathogenic H5N1 influenza viruses reemerged in humans in 2003 and have caused fatal human infections in Asia and Africa as well as ongoing outbreaks in poultry. These viruses have evolved substantially and are now so antigenically varied that a single vaccine antigen may not protect against all circulating strains. Nevertheless, studies have shown that substantial cross‐reactivity can be achieved with H5N1 vaccines. These studies have not, however, addressed the issue of duration of such cross‐reactive protection. Objectives To directly address this using the ferret model, we used two recommended World Health Organization H5N1 vaccine seed strains – A/Vietnam/1203/04 (clade 1) and A/duck/Hunan/795/02 (clade 2.1) – seven single, double, or triple mutant viruses based on A/Vietnam/1203/04, and the ancestral viruses A and D, selected from sequences at nodes of the hemagglutinin and neuraminidase gene phylogenies to represent antigenically diverse progeny H5N1 subclades as vaccine antigens. Results All inactivated whole‐virus vaccines provided full protection against morbidity and mortality in ferrets challenged with the highly pathogenic H5N1 strain A/Vietnam/1203/04 5 months and 1 year after immunization. Conclusion If an H5N1 pandemic was to arise, and with the hypothesis that one can extrapolate the results from three doses of a whole‐virion vaccine in ferrets to the available split vaccines for use in humans, the population could be efficiently immunized with currently available H5N1 vaccines, while the homologous vaccine is under production.     

Comparative safety, immunogenicity, and efficacy of several anti-H5N1 influenza experimental vaccines in a mouse and chicken models (Testing of killed and live H5 vaccine)

Please cite this paper as: Gambaryan et al. (2011) Comparative safety, immunogenicity, and efficacy of several anti‐H5N1 influenza experimental vaccines in a mouse and chicken models. Parallel testing of killed and live H5 vaccine. Influenza and Other Respiratory Viruses 6(3), 188–195. Objective Parallel testing of inactivated (split and whole virion) and live vaccine was conducted to compare the immunogenicity and protective efficacy against homologous and heterosubtypic challenge by H5N1 highly pathogenic avian influenza virus. Method Four experimental live vaccines based on two H5N1 influenza virus strains were tested; two of them had hemagglutinin (HA) of A/Vietnam/1203/04 strain lacking the polybasic HA cleavage site, and two others had hemagglutinins from attenuated H5N1 virus A/Chicken/Kurgan/3/05, with amino acid substitutions of Asp54/Asn and Lys222/Thr in HA1 and Val48/Ile and Lys131/Thr in HA2 while maintaining the polybasic HA cleavage site. The neuraminidase and non‐glycoprotein genes of the experimental live vaccines were from H2N2 cold‐adapted master strain A/Leningrad/134/17/57 (VN‐Len and Ku‐Len) or from the apathogenic H6N2 virus A/Gull/Moscow/3100/2006 (VN‐Gull and Ku‐Gull). Inactivated H5N1 and H1N1 and live H1N1 vaccine were used for comparison. All vaccines were applied in a single dose. Safety, immunogenicity, and protectivity against the challenge with HPAI H5N1 virus A/Chicken/Kurgan/3/05 were estimated. Results All experimental live H5 vaccines tested were apathogenic as determined by weight loss and conferred more than 90% protection against lethal challenge with A/Chicken/Kurgan/3/05 infection. Inactivated H1N1 vaccine in mice offered no protection against challenge with H5N1 virus, while live cold‐adapted H1N1 vaccine reduced the mortality near to zero level. Conclusions The high yield, safety, and protectivity of VN‐Len and Ku‐Len made them promising strains for the production of inactivated and live vaccines against H5N1 viruses.     

Insight into Alternative Approaches for Control of Avian Influenza in Poultry,with Emphasis on Highly Pathogenic H5N1

Highly pathogenic avian influenza virus (HPAIV) of subtype H5N1 causes a devastating disease in poultry but when it accidentally infects humans it can cause death. Therefore, decrease the incidence of H5N1 in humans needs to focus on prevention and control of poultry infections. Conventional control strategies in poultry based on surveillance, stamping out, movement restriction and enforcement of biosecurity measures did not prevent the virus spreading, particularly in developing countries. Several challenges limit efficiency of the vaccines to prevent outbreaks of HPAIV H5N1 in endemic countries. Alternative and complementary approaches to reduce the current burden of H5N1 epidemics in poultry should be encouraged. The use of antiviral chemotherapy and natural compounds, avian-cytokines, RNA interference, genetic breeding and/or development of transgenic poultry warrant further evaluation as integrated intervention strategies for control of HPAIV H5N1 in poultry.     

Efficacy of a heterologous vaccine and adjuvant in ferrets challenged with influenza virus H5N1

Please cite this paper as: Vela et al. (2012) Efficacy of a heterologous vaccine and adjuvant in ferrets challenged with influenza virus H5N1. Influenza and Other Respiratory Viruses 6(5), 328–340. Background In 1997, highly pathogenic avian influenza (HPAI) viruses caused outbreaks of disease in domestic poultry markets in Hong Kong. The virus has also been detected in infected poultry in Europe and Africa. Objective The objective of this study was to determine the efficacy of a heterologous vaccine administered with and without the aluminum hydroxide adjuvant in ferrets challenged with HPAI (A/Vietnam/1203/04). Methods Animals in four of the five groups were vaccinated twice 21 days apart, with two doses of a heterologous monovalent subvirion vaccine with or without an aluminum hydroxide adjuvant and challenged with a lethal target dose of A/Vietnam/1203/04. Results All animals vaccinated with the heterologous vaccine in combination with the aluminum hydroxide adjuvant survived a lethal challenge of A/Vietnam/1203/04. Four of the eight animals vaccinated with 30 μg of the vaccine without the adjuvant survived, while two of the eight animals vaccinated with 15 μg of the vaccine without the adjuvant survived. None of the unvaccinated control animals survived challenge. Additionally, changes in virus recovered from nasal washes and post‐mortem tissues and serology suggest vaccine efficacy. Conclusions Altogether, the data suggest that the heterologous vaccine in combination with the aluminum hydroxide adjuvant offers maximum protection against challenge with A/Vietnam/1203/04 when compared to the unvaccinated control animals or animals vaccinated without any adjuvant.