Influenza vaccines: unmet needs and recent developments

The Next Generation of Influenza Vaccines: Towards a Universal Solution

Influenza viruses remain a constant burden in humans, causing millions of infections and hundreds of thousands of deaths each year. Current influenza virus vaccine modalities primarily induce antibodies directed towards the highly variable head domain of the hemagglutinin protein on the virus surface. Such antibodies are often strain-specific, meaning limited cross-protection against divergent influenza viruses is induced, resulting in poor vaccine efficacy. To attempt to counteract this, yearly influenza vaccination with updated formulations containing antigens from more recently circulating viruses is required. This is an expensive and time-consuming exercise, and the constant arms race between host immunity and virus evolution presents an ongoing challenge for effective vaccine development. Furthermore, there exists the constant pandemic threat of highly pathogenic avian influenza viruses with high fatality rates (~30–50%) or the emergence of new, pathogenic reassortants. Current vaccines would likely offer little to no protection from such viruses in the event of an epidemic or pandemic. This highlights the urgent need for improved influenza virus vaccines capable of providing long-lasting, robust protection from both seasonal influenza virus infections as well as potential pandemic threats. In this narrative review, we examine the next generation of influenza virus vaccines for human use and the steps being taken to achieve universal protection.

Preliminary Volumetric Calculation of the Mucosal Surface in the Nares of Lambs Using a Segmentation of Computed Tomographic Images

Intranasal vaccinations are becoming more important in both human and animal medicine to generate a localized IgA immune response not seen with parenteral vaccinations. This localized IgA response is more effective at reducing pathogen load on the mucosal surface of a potential host. One prerequisite for a successful nasal vaccination is the need to understand the distribution pattern of the nebulized vaccine, which requires an understanding the volume of the nares as well as the mucosal surface area. The exact mucosal surface area of ruminant nares has not yet been investigated. The aim of this concept study is to provide a detailed breakdown of a new method of volumetric rendering that can be used to calculate the volume and mucosal surface area of ruminant nares from computed tomographic images. The program Seg 3D was used to perform semi-automatic segmentation of a CT scan of a 9-month-old lamb head. Threshold segmentation and manual segmentation were used in combination to select the lamb's nasal cavity. The segmentation process yielded a volumetric rendering that was used to calculate the surface area and volume of the lamb's nasal cavity, with the segmentation process was repeated for each individual side of the lamb's nares. The surface area of the mucosal surface of each nostril is approximately 448 cm², and the volume is approximately 45 cm³. The methodology described in this study successfully calculated the volume and surface area of a lamb's nares using volumetric rendering.

Epidemiological features and trends of influenza incidence in mainland China: A population-based surveillance study from 2005 to 2015

OBJECTIVES

To investigate epidemiological features and trends of influenza incidence with 1,173,640 cases in mainland China from 2005 to 2015.

METHODS

Incidence and mortality data for influenza from 2005 to 2015 were provided by the data-center of China public health science and covered a population of about 1.3 billion people from 31 provinces and regions in mainland China. Joinpoint regression and exploratory spatial data analyses were used to examine the incidence trends from 2005 to 2015.

RESULTS

The first upsurge in influenza cases occurred in 2009, and the highest incidence of influenza occurred in 2014 (15.9045 cases/100,000 people). The average incidence per year from 2009 to 2015 was threefold higher than that from 2005 to 2008 (10.5308 vs 3.4589 cases/100,000 people; incidence rate ratio=3.0446). The joinpoint regression results showed that there was an increasing influenza incidence trend from 2005 to 2015 (annual change in percentage=13.6%, 95%CI 2.2-26.3, p=0.0236). The seasonal pattern analysis showed that influenza typically occurred in winter and spring during each monitoring year, peaking from November to March the next year.

CONCLUSIONS

This study will help governments to make valuable decisions in allocating scarce resources and providing strategies to limit the spread of influenza.

In vitro responses of chicken macrophage-like monocytes following exposure to pathogenic and non-pathogenic E. coli ghosts loaded with a rational design of conserved genetic materials of influenza and Newcastle disease viruses

Avian influenza virus (AIV) and Newcastle disease virus (NDV) are two important viral diseases in the poultry industry. Therefore, new disease-fighting strategies, especially effective genetic vaccination, are in high demand. Bacterial Ghost (BG) is a promising platform for delivering genetic materials to macrophages, cells that are among the first to encounter these viruses. However, there is no investigation on the immune response of these macrophage-targeted treatments. Here, we investigated the effect of genetic materials of AIV and NDV on the gene expression profile of important pro-inflammatory cytokines, a chemokine, a transcription factor, major histocompatibility complexes, and the viability of the chicken macrophage-like monocyte cells (CMM). Our genetic construct contained the external domain of matrix protein 2 and nucleoprotein gene of AIV, and immunodominant epitopes of fusion and hemagglutinin-neuraminidase proteins of NDV (hereinafter referred to as pAIV-Vax), delivered via the pathogenic and non-pathogenic BGs (Escherichia coli O78K80 and E. coli TOP10 respectively). The results demonstrated that both types of BGs were able to efficiently deliver the construct to the CMM, although the pathogenic strain derived BG was a significantly better stimulant and delivery vehicle. Both BGs were safe regarding LPS toxicity and did not induce any cell death. Furthermore, the loaded BGs were more powerful in modulating the pro-inflammatory cytokines' responses and antigen presentation systems in comparison to the unloaded BGs. Nitric oxide production of the BG-stimulated cells was also comparable to those challenged by the live bacteria. According to the results, the combination of pAIV-Vax construct and E. coli O78K80 BG is promising in inducing a considerable innate and adaptive immune response against AIV-NDV and perhaps the pathogenic E. coli, provided that the current combination be a potential candidate for in vivo testing regarding the development of an effective trivalent DNA vaccine against avian influenza and Newcastle disease, as well as a bacterial ghost vaccine against avian pathogenic E. coli (APEC).

The success of microneedle-mediated vaccine delivery into skin

Microneedles (MNs) are designed to specifically target the outermost, skin barrier layer, the stratum corneum, creating transient pathways for minimally invasive transcutaneous delivery. It is reported that MNs can facilitate delivery without stimulating the pain receptors or damaging blood vessels that lie beneath, thus being perceived as painless and associated with reduced bleeding. This immunocompetence of the skin, coupled with its ease of access, makes this organ an attractive vaccination site. The purpose of this review was to collate primary scientific literature pertaining to MN-mediated in vivo vaccination programmes. A total of 62 original research articles are presented, compiling vaccination strategies in 6 different models (mouse, rat, guinea pig, rabbit, pig, macaque and human). Vaccines tested span a wide range of viral, bacterial and protozoan pathogens and includes 7 of the 13 vaccine-preventable diseases, as defined by the WHO. This review highlights the paucity of available clinical trial data. MN-delivered vaccines have demonstrated safety and immunogenicity in pre-clinical models and boast desirable attributes such as painless administration, thermostability, dose-sparing capacity and the potential for self-administration. These advantages should contribute to enhanced global vaccine access.

[Current state of influenza vaccination and factors affecting vaccination rate among pregnant women]

PURPOSE

This study was done to examine the actual state of influenza vaccination among pregnant women and factors affecting vaccination rate.

METHODS

Data were collected using self-report questionnaires. Participants were pregnant women who participated in a prenatal education program at an acute care hospital in 2013. Data collected from 218 pregnant women were analyzed using the SPSS 18.0 Program.

RESULTS

Only 48.6% of the pregnant women had received vaccination when the influenza was prevalent. Statistically significant factors affecting the influenza vaccination rate among pregnant women were vaccination experience in the previous year, knowledge and attitude about vaccination, and gestation period.

CONCLUSION

Results indicate that the influenza vaccination rate among pregnant women is lower than that of elders, healthcare workers, and patients with chronic diseases, who have been considered to be the mandatory vaccination recipients. Therefore, it is necessary to develop programs and policies which provide information including safety of vaccines for pregnant women and to induce positive attitudes towards vaccination for these women, in order to ultimately improve the vaccination rate.

Effectiveness of Influenza Vaccination for Individuals with Chronic Obstructive Pulmonary Disease (COPD) in Low- and Middle-Income Countries

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of death globally. In addition to the mortality associated with it, people with COPD experience significant morbidity, making this set of conditions a major public health concern. Infections caused by influenza virus are a preventable cause of morbidity and vaccination has been shown to be effective. The evidence of their benefit in persons with COPD mainly comes from high-income countries where influenza vaccination is used in routine practice, but little is known about the effectiveness, cost-effectiveness, and scalability of vaccination in low- and middle-income countries. We therefore systematically reviewed and present evidence related to vaccination against influenza in persons with COPD with a special focus on studies from low- and middle-income countries (LMICs). Available data from 19 studies suggest that the use of influenza vaccine in persons with COPD is beneficial, cost-effective, and may be relevant for low- and middle-income countries. Wider implementation of this intervention needs to take into account the health care delivery systems of LMICs and use of prevalent viral strains in vaccines to be most cost effective.

Antiviral therapy in seasonal influenza and 2009 H1N1 pandemic influenza: Korean experiences and perspectives

Influenza is a major cause of substantial morbidity and mortality in humans every year. Vaccination is the main strategy to prevent influenza infection, but antiviral agents also play an important role in the control of both seasonal and pandemic influenza. During the influenza A/H1N1 pandemic in 2009, early prompt antiviral therapy may have reduced the severity of the influenza outcomes including pneumonia, hospitalization and mortality in the Republic of Korea. Since the 2009 H1N1 pandemic, there have been increasing usages of antiviral agents for the treatment of patients with seasonal influenza. Although currently rare, antiviral resistance among influenza viruses may emerge and increase with increased use of neuraminidase inhibitors. New agents with different modes of action are under investigation, including favipiravir, DAS181, nitazoxanide and broad-spectrum neutralizing monoclonal antibodies. Data are limited with respect to high-dose and combination antiviral therapies. So, clinical trials are warranted to evaluate diverse antiviral combinations that may be synergistic and less likely to induce breakthrough resistance.

Difluorosialic acids, potent novel influenza virus neuraminidase inhibitors, induce fewer drug resistance-associated neuraminidase mutations than does oseltamivir

Neuraminidase inhibitors (NAIs), including the most frequently prescribed oral therapeutic oseltamivir, play a critical role in the control of severe influenza virus (IFV) infections. However, recent reports of spread of an oseltamivir-resistant H1N1 pandemic strain in individuals who have never been exposed to oseltamivir highlight an urgent need for new antivirals against NAI-resistant IFVs. Difluorosialic acids (DFSAs) are a novel class of anti-IFV NAIs designed based on the mechanism of action of IFV NA, and distinguished by their covalent inhibition mode and their high structural similarity to the natural substrate, sialic acid. These characteristics should render the development of resistance a less rapid process. In this report, we evaluated the relative propensity of influenza A virus (IFV-A) NA to develop resistance against the DFSA class of inhibitor by passaging IFV-A strains in vitro in the presence of either oseltamivir or a representative DFSA (FeqGuDFSA). All the passage-selected lines gained mutations in hemagglutinin. Among the 12 oseltamivir-resistant passaged lines, five gained NA mutations and four of these were the well-defined H275Y mutation that causes oseltamivir resistance. In contrast, out of 15 DFSA-passaged lines, only 2 lines gained NA mutations. Further, NA inhibition assays indicated that these mutations did not change the sensitivity of NA to DFSA and thus the resistance to DFSA was not conferred by these NA mutations. These results strongly suggest that, compared to oseltamivir, IFV is less prone to development of resistance against DFSAs through NA mutations.

Association between Living Arrangements and Influenza Vaccination Rates among Elderly South Korean People: The Fifth Korea National Health and Nutrition Examination Survey (KNHANES V-2)

BACKGROUND

This study aimed to investigate the association between living arrangements and influenza vaccination among elderly South Korean subjects.

METHODS

We used data from the fifth Korean National Health and Nutrition Examination Survey. Participants older than 65 years were included and categorized into 4 groups according to the type of living arrangement as follows: (1) living alone group; (2) living with a spouse group; (3) living with offspring (without spouse) group; and (4) living with other family members group. A total of 1,435 participants were included in this cross-sectional analysis.

RESULTS

A lower vaccination rate was observed in the living with offspring (without spouse) group, whereas the living with a spouse group had higher rates of both seasonal and H1N1 influenza vaccination. After adjusting for age, sex, region, education level, income level, and number of comorbidities, the living with offspring (without spouse) group had a higher H1N1 vaccination non-receipt rate than the living alone group (odds ratio, 2.03; 95% confidence interval, 1.08-3.82).

CONCLUSION

Influenza vaccination rates differed according to the type of living arrangement. Particularly, those living with offspring (without spouse) had the lowest H1N1 influenza vaccination rate compared to those with other living arrangements, and this difference was significant. Interventions to improve influenza vaccination coverage should target not only elderly persons who live alone, but also those living with offspring.

Virus-vectored influenza virus vaccines

Despite the availability of an inactivated vaccine that has been licensed for >50 years, the influenza virus continues to cause morbidity and mortality worldwide. Constant evolution of circulating influenza virus strains and the emergence of new strains diminishes the effectiveness of annual vaccines that rely on a match with circulating influenza strains. Thus, there is a continued need for new, efficacious vaccines conferring cross-clade protection to avoid the need for biannual reformulation of seasonal influenza vaccines. Recombinant virus-vectored vaccines are an appealing alternative to classical inactivated vaccines because virus vectors enable native expression of influenza antigens, even from virulent influenza viruses, while expressed in the context of the vector that can improve immunogenicity. In addition, a vectored vaccine often enables delivery of the vaccine to sites of inductive immunity such as the respiratory tract enabling protection from influenza virus infection. Moreover, the ability to readily manipulate virus vectors to produce novel influenza vaccines may provide the quickest path toward a universal vaccine protecting against all influenza viruses. This review will discuss experimental virus-vectored vaccines for use in humans, comparing them to licensed vaccines and the hurdles faced for licensure of these next-generation influenza virus vaccines.