Secretory IgAs (sIgA) constitute the principal isotype of antibodies present in nasal and mucosal secretions. They are secreted by plasma cells adjacent to the mucosal epithelial cells, the site where infection occurs, and are the main humoral mediator of mucosal immunity. Mucosally delivered vaccines, such as live attenuated influenza vaccine (LAIV), are able to mimic natural infection without causing disease or virus transmission and mainly elicit a local immune response. The measurement of sIgA concentrations in nasal swab/wash and saliva samples is therefore a valuable tool for evaluating their role in the effectiveness of such vaccines. Here, we describe two standardized assays (enzyme‐linked immunosorbent assay and microneutralization) available for the quantification of sIgA and discuss the advantages and limitations of their use.

Influenza vaccines are a fundamental tool for preventing the disease and reducing its consequences, particularly in specific high-risk groups. In order to be licensed, influenza vaccines have to meet strict criteria established by European Medicines Agency. Although the licensure of influenza vaccines started 65 years ago, Hemagglutination Inhibition and Single Radial Hemolysis are the only serological assays that can ascertain correlates of protection. However, they present evident limitations. The present review focuses on the evaluation of cell-mediated immunity (CMI), which plays an important role in the host immune response in protecting against virus-related illness and in the establishment of long-term immunological memory. Although correlates of protection are not currently available for CMI, it would be advisable to investigate this kind of immunological response for the evaluation of next-generation vaccines.

Influenza continues to be the most important cause of viral respiratory disease, despite the availability of vaccines. Today’s evaluation of influenza vaccines mainly focuses on the quantitative and functional analyses of antibodies to the surface proteins haemagglutinin (HA) and neuraminidase (NA). However, there is an increasing interest in measuring cellular immune responses targeting not only mutation-prone surface HA and NA but also conserved internal proteins as these are less explored yet potential correlates of protection. To date, laboratories that monitor cellular immune responses use a variety of in-house procedures. This generates diverging results, complicates interlaboratory comparisons, and hampers influenza vaccine evaluation. The European FLUCOP project aims to develop and standardize assays for the assessment of influenza vaccine correlates of protection. This report describes the harmonization and qualification of the influenza-specific interferon-gamma (IFN-γ) Enzyme-Linked ImmunoSpot (ELISpot) assay. Initially, two pilot studies were conducted to identify sources of variability during sample analysis and spot enumeration in order to develop a harmonized Standard Operating Procedure (SOP). Subsequently, an assay qualification study was performed to investigate the linearity, intermediate precision (reproducibility), repeatability, specificity, Lower and Upper Limits of Quantification (LLOQ-ULOQ), Limit of Detection (LOD) and the stability of signal over time. We were able to demonstrate that the FLUCOP harmonized IFN-γ ELISpot assay procedure can accurately enumerate IFN-γ secreting cells in the analytical range of 34.4 Spot Forming Units (SFU) per million cells up to the technical limit of the used reader and in the linear range from 120 000 to 360 000 cells per well, in plates stored up to 6 weeks after development. This IFN-γ ELISpot procedure will hopefully become a useful and reliable tool to investigate influenza-specific cellular immune responses induced by natural infection or vaccination and can be an additional instrument in the search for novel correlates of protection.

Introduction: Leishmaniasis represents one of the most dangerous neglected tropical diseases. The parasite used to show a well-defined geographical distribution; however, during the last decade the parasite has spread into new areas. This change in the worldwide distribution of the parasite and in leishmaniasis epidemiology are the result of man’s ill-considered interventions in the environment and of the consequent global warming. Areas covered: The present review focuses on Leishmaniasis incidence in the Mediterranean basin and underlines the pressing need to raise awareness toward the real burden of the disease in the European region. The research was undertaken using Pubmed and including all studies up to January 2020. Expert opinion: Environmental and climatic transformations have allowed the shifting northward of sand fly European geographical distribution, affecting areas traditionally considered as Leishmania-free, including Northern Italy, Germany and even Belgium. The large-scale migration from the Middle East and Africa to Europe, and particularly to Italy for its central position in the Mediterranean basin, represents an additional and critical risk factor for the spread not only of leishmaniasis but also of other potentially life-threatening diseases. These factors highlight how the current epidemiological European scenario could drastically evolve in the next future.

Since the first detection of a novel Coronavirus (SARS-CoV-2) in December 2019 in Wuhan (China), it has become crucial to assess and quantize the human humoral immune response after SARS-CoV-2 natural infection and/or vaccination. Having well standardized and reliable serological assays able to accurately measure the total IgG antibodies response as well as the neutralization dynamics, play a pivotal role for the evaluation of “second” and “third” vaccines generation and in monitoring the effect in case of reinfection in the human population caused by the original strains or new SARS-CoV-2 variants. In the present study we reported that both symptomatic convalescent and vaccinated donors showed the presence of different levels of neutralizing antibodies. In addition, vaccinated subjects presented high levels of anti-S antibodies, whereas the complete absence of anti-N antibodies, whereas convalescent patients presented high levels of both anti-S and anti-N antibodies. The evaluation of the correlation between SARS-CoV-2 neutralizing and binding antibodies in convalescent and vaccinated subjects revealed that the IgG anti-S log-values were significantly higher in the vaccinated group respect to convalescent subjects. In addition, the level of binding antibodies recognizing the S protein shows a positive linear regression when compared to neutralizing titres in both the two groups evaluated.

Since the mid-1980s, two lineages of influenza B viruses have been distinguished. These can co-circulate, limiting the protection provided by inactivated trivalent influenza vaccines (TIVs). This has prompted efforts to formulate quadrivalent influenza vaccines (QIVs), to enhance protection against circulating influenza B viruses. This review describes the results obtained from seven phase III clinical trials evaluating the immunogenicity, safety, and lot-to-lot consistency of a new quadrivalent split-virion influenza vaccine (Vaxigrip Tetra^®) formulated by adding a second B strain to the already licensed TIV. Since Vaxigrip Tetra was developed by means of a manufacturing process strictly related to that used for TIV, the data on the safety profile of TIV are considered supportive of that of Vaxigrip Tetra. The safety and immunogenicity of Vaxigrip Tetra were similar to those of the corresponding licensed TIV. Moreover, the new vaccine elicits a superior immune response towards the additional strain, without affecting immunogenicity towards the other three strains. Vaxigrip Tetra is well tolerated, has aroused no safety concerns, and is recommended for the active immunization of individuals aged ≥6 months. In addition, preliminary data confirm its immunogenicity and safety even in children aged 6–35 months and its immunogenicity in older subjects (aged 66–80 years).