CORRELATES OF PROTECTION AND HOST-RELATED MODIFIERS OF THE IMMUNOGENICITY OF INFLUENZA VACCINES: EVIDENCE MAPS AND EVIDENCE GAPS

Seasonal influenza is the leading infectious disease in terms of its health and socioeconomic impact. Annual immunization is the most efficient way to reduce this burden. To be clinically effective, influenza vaccines must be immunogenic, and several immunological assays to test their immunogenicity have been developed. The overall aim of this PhD thesis is to provide the principal stakeholders (including scientists, healthcare professionals, policy-makers, pharmaceutical industry, etc.) with stateof-the-art knowledge and practices related to influenza vaccine-induced immunogenicity. To achieve this aim, we developed a novel empirical approach that incorporated some modern techniques, including, for example, evidence mapping. Basically, this thesis is composed of three main domains. In the introductory part, we will briefly cover the topics of influenza disease, influenza vaccination, the immunogenicity measurements of influenza vaccines and their correlates of protection. The second part, which is the core of the present project, is composed of two original case studies. The first study aimed to describe the patterns of use of the various immunological assays available to measure the influenza vaccine-induced adaptive immune response and to determine its correlates of protection. For this purpose, we analyzed 1,164 phase I–IV studies that enrolled a total of 754,935 subjects. Of the studies included in our analysis, 76.5% measured only the humoral immune response. Among these, the hemagglutination-inhibition assay was by far the most widely used. Other, less common, humoral immune response assays were: virus neutralization (21.7%), enzyme-linked immunosorbent (10.1%), single radial hemolysis (4.6%) and assays able to quantify antineuraminidase antibodies (1.7%). By contrast, cell-mediated immunity was quantified in only 23.5% of studies. Several variables were significantly (P < .05) associated with the use of single assays. Specifically, some influenza vaccine types (e.g. adjuvanted, live attenuated and cell culture-derived or recombinant), study phase and study sponsorship pattern were usually found to be statistically significant predictors. In the second study, we went further by systematically analyzing host-related factors able to modify influenza vaccine-induced immunogenicity. To this end, a total of 28 systematic reviews/meta-analyses (with thousands of participants) were analyzed. These covered the following domains: intravenous drug use, psychological stress, acute and chronic physical exercise, genetic polymorphisms, use of pre-/pro-/symbiotics, previous Bacillus Calmette–Guérin vaccination, diabetes mellitus, vitamin D supplementation/deficiency, latent cytomegalovirus infection and various forms of immunosuppression. In order to present effect sizes on the same scale, all meta-analyses were re-performed, whenever possible, and cumulative evidence synthesis ranking was carried out. Meta-analysis was conducted separately on each health condition category and virus (sub)type. A total of 295 meta-analyses were re-performed/performed ex novo; of these, 97 pooled estimates were used in order to construct an evidence-based stakeholder-friendly map. Finally, we discussed the principal findings, made some suggestions from the point of view of the various stakeholders and proposed a novel immunogenicity pathway

Emerging and Re-emerging Arboviral Diseases as a Global Health Problem

Newly emerging or re-emerging infections continue to pose significant global public health threats. This chapter provides an overview of the combinations of factors that led to the emergence of arthropod-borne viruses as human and veterinary health threats, in order to understand the risk associated and how this can be mitigated. Considering the history of emergence of some arboviruses, these epidemics have occurred globally as a result of climate and socioeconomic changes that have allowed the spread to new geographical areas of viruses previously confined to specific ecological niches such as West Nile and Chikungunya, or viruses considered under control such as Dengue, Japanese encephalitis, and Yellow fever. Moreover, the greatest risk for humans derives from the ability of these viruses to adopt transmission cycles involving highly anthropophilic mosquito species. Finally, many other arboviruses are largely ignored despite their potential to emerge globally. The recent epidemic spread of Zika virus throughout the Americas is the evidence that arboviruses are likely to continually emerge and re-emerge and that improved scientific technologies and knowledge is essential to deal with future vector-borne epidemics. Research priorities should therefore focus on surveillance systems and vector control tools, as well as on the development of antiviral molecules or candidate vaccine

The baculovirus expression vector system: a modern technology for the future of influenza vaccine manufacturing

Introduction Influenza is a vaccine-preventable disease. Due to the evolving nature of influenza viruses, the composition of vaccines has to be updated annually. Most of the current influenza vaccines are still produced in embryonated chicken eggs, a well-established process with some limitations. Area covered This review focuses on the recombinant DNA technology using baculovirus expression vector system a modern method of manufacturing licensed influenza vaccines. The speed, scalability, biosafety and flexibility of the process, together with the reliability of the hemagglutinin in the vaccine, represent a significant advance toward new platforms for vaccine production. Expert opinion The scenario of vaccine production in the next years seems to be particularly interesting, involving a transition from the current egg-based production to new technologies, such as the cell culture platform, the RNA technology, the plant-based system, and the DNA vaccine. This latter offers great advantages over egg- and cell-based influenza vaccine production. The universal vaccine remains the goal of researchers and ideally would avoid the need for annual reformulation and re-administration of seasonal vaccines. The lesson learned from the COVID-19 pandemic highlights the importance of having different technologies available and able to promptly respond to a great demand of vaccines worldwide

Comparison of influenza-specific neutralizing antibody titers determined using different assay readouts and hemagglutination inhibition titers:good correlation but poor agreement

Determination of influenza-specific antibody titers is commonly done using the hemagglutination inhibition assay (HAI) and the viral microneutralization assay (MN). Both assays are characterized by high intra- and inter-laboratory variability. The HAI assay offers little opportunity for standardization. For the MN assay, variability might be due to the use of different assay protocols employing different readouts. We therefore aimed at investigating which of the MN assay readout methods currently in use would be the most suitable choice for a standardized MN assay that could serve as a substitute for the HAI assay. For this purpose, human serum samples were tested for the presence of influenza specific neutralizing antibodies against A/California/7/09 H1N1 (49 sera) or A/Hong Kong/4801/2014 (50 sera) using four different infection readout methods for the MN assay (cytopathic effect, hemagglutination, ELISA, RT qPCR) and using the HAI assay. The results were compared by correlation analysis and by determining the level of agreement before and after normalization to a standard serum. Titers as measured by the 4 MN assay readouts showed good correlation, with high Person's r for most comparisons. However, agreement between nominal titers varied with readouts compared and virus strain used. In addition, Pearson's correlation of MN titers with HAI titers was high but agreement of nominal titers was moderate and the average difference between the readings of two assays (bias) was virus strain-dependent. Normalization to a standard serum did not result in better agreement of assay results. Our study demonstrates that different MN readouts result in nominally different antibody titers. Accordingly, the use of a common and standardized MN assay protocol will be crucial to minimize inter-laboratory variability. Based on reproducibility, cost effectiveness and unbiased assessment of results we elected the MN assay with ELISA readout as most suitable for a possible replacement of the HAI assay

Fluid management in the perioperative setting: mind the kidney

Acute kidney injury (AKI) is one of the most frequent complications in critically ill patients and in the perioperative setting. The anatomical structure and the microvasculature of the kidney makes it highly vulnerable to hypoxia. Although fluid therapy is considered crucial in situations where improvement of cardiac output is needed, it can also contribute to AKI development when administered inappropriately. Hemodilution and anemia during cardio-pulmonary bypass have been demonstrated to be risk factors for AKI and they are likely to be a consequence of fluid administration. In order to assess the perfusion of the kidneys it is necessary to investigate the determinants of delivery of oxygen at the microcirculatory level. Indeed, fluids can decrease the capillary hematocrit and the functional capillary density, affecting the renal oxygenation and increasing the risk of AKI. Monitoring sublingual microcirculation can be a reliable tool to guide fluid administration, aiming to prevent or improve perioperative AKI

Toxoplasma gondii in women of childbearing age and during pregnancy: seroprevalence study in Central and Southern Italy from 2013 to 2017

Toxoplasmosis is a worldwide health problem. Infection in pregnant women can result in severe fetal morbidity or in subclinical neonatal infection; most subclinical cases develop ocular and neurological sequelae. The purpose of this serological study was to assess the prevalence of Toxoplasma gondii in two populations of women of childbearing age in Siena (Tuscany, Central Italy) and Bari (Apulia, Southern Italy) between 2013 and 2017 and in a group of pregnant women in Bari in 2016-2017. Serum samples were tested for the presence of specific anti-Toxoplasma gondii IgG antibodies by a commercially available ELISA test. The percentage of seropositive subjects in Bari was significantly higher than in Siena (22.4% vs. 12.4%) and an age-related trend was observed. A low prevalence of T. gondii infection (13.8%) was observed among the pregnant women tested. In addition to showing a significant difference between Central and Southern Italy, this study provides updated data on T. gondii seroprevalence in women during childbearing age and pregnancy. The results confirm a trend toward a decrease, especially in younger people and pregnant women

Epidemiology of herpes simplex virus type 1 and 2 in Italy: a seroprevalence study over 15 years

Introduction: Herpes simplex viruses (HSV) are among the most widespread causative agents of human viral infections. HSV-2 is one of the commonest causes of genital disease, while HSV-1 is associated primarily with orolabial ulceration; however, recent changes in HSV epidemiology showed an increase in genital and neonatal herpes particularly caused by HSV-1. The main purpose of this study was to assess the seroprevalence of HSV-1 and HSV-2 in a random population in Siena (central Italy) in 2000, 2005 and 2013-2014 and in Bari (southern Italy) in 2005. Moreover, a preliminary study was conducted to investigate the spread of HSV infection in a population of pregnant women and infants in Bari in 2003, 2004 and 2005. Methods: Human serum samples were tested for the presence of specific anti-HSV-1 and anti-HSV-2 IgG antibodies using a commercially available ELISA test. Results and conclusions: For the primary purpose, seroprevalence rates observed in Siena were compared over the years sampled and with the seroprevalence rate found in Bari. Results of seroprevalence in Siena show a decreased trend for both viruses, especially in adolescents and young adults; moreover, HSV-2 seroprevalence rates found in the two cities suggest geographical differences. For the secondary purpose, prevalence rates among pregnant women were compared with the seroprevalence found in women of the general population. No significant difference in prevalence rates were found among pregnant women, while results indicate both viruses are a source of infection in infants

immunogenicity and safety of quadrivalent versus trivalent inactivated subunit influenza vaccine in children and adolescents a phase iii randomized study

Abstract Objectives To analyze the immunogenicity and safety of inactivated subunit quadrivalent influenza vaccine (QIV) versus trivalent influenza vaccine (TIV) in children and adolescents 3–17 years of age. Methods In this phase III, multicenter, double-blind study, 1200 subjects were randomized to receive QIV (n = 402), or TIV with the B-strain of the Victoria lineage (n = 404) or Yamagata lineage (n = 394). The primary objective was to demonstrate non-inferiority of QIV to TIV for immunogenicity against shared influenza strains, based on post-vaccination hemagglutinin inhibition (HI) titers. Secondary objectives were to show superiority of QIV to TIV for immunogenicity against alternate-lineage B-strains, and to further characterize immune response by analyzing virus neutralization and neuraminidase inhibition titers. Reactogenicity and safety were also compared post-vaccination. Results QIV elicited a non-inferior response for shared strains (upper limits of the 95% confidence intervals for the HI geometric mean ratios [GMRs] of TIV/QIV  Conclusions QIV had comparable immunogenicity to TIV for shared strains and superior immunogenicity to the alternate-lineage B-strains in TIV. Safety and tolerability profiles were comparable

Influenza vaccines: Evaluation of the safety profile

3noopenThe safety of vaccines is a critical factor in maintaining public trust in national vaccination programs. Vaccines are recommended for children, adults and elderly subjects and have to meet higher safety standards, since they are administered to healthy subjects, mainly healthy children. Although vaccines are strictly monitored before authorization, the possibility of adverse events and/or rare adverse events cannot be totally eliminated. Two main types of influenza vaccines are currently available: parenteral inactivated influenza vaccines and intranasal live attenuated vaccines. Both display a good safety profile in adults and children. However, they can cause adverse events and/or rare adverse events, some of which are more prevalent in children, while others with a higher prevalence in adults. The aim of this review is to provide an overview of influenza vaccine safety according to target groups, vaccine types and production methods.openTrombetta, Claudia Maria*; Gianchecchi, Elena; Montomoli, EmanueleTrombetta, Claudia Maria; Gianchecchi, Elena; Montomoli, Emanuel