Progress in vaccine development for infectious diseases-a Keystone Symposia report.

The COVID-19 pandemic has taught us many things, among the most important of which is that vaccines are one of the cornerstones of public health that help make modern longevity possible. While several different vaccines have been successful at stemming the morbidity and mortality associated with various infectious diseases, many pathogens/diseases remain recalcitrant to the development of effective vaccination. Recent advances in vaccine technology, immunology, structural biology, and other fields may yet yield insight that will address these diseases; they may also help improve societies' preparedness for future pandemics. On June 1-4, 2022, experts in vaccinology from academia, industry, and government convened for the Keystone symposium "Progress in Vaccine Development for Infectious Diseases" to discuss state-of-the-art technologies, recent advancements in understanding vaccine-mediated immunity, and new aspects of antigen design to aid vaccine effectiveness.

[COVID-19: Warp Speed vaccines]. / COVID-19, des vaccins à la vitesse de l'éclair.

A vaccine is required to effectively control the COVID-19 pandemic in the mid and long term. The development of vaccines against SARS-CoV-2 was initiated as soon as the genetic sequence of the virus was published, and has evolved at an unprecedented speed, with a first clinical trial launched in March 2020. One year later, more than a dozen of vaccines based on different concepts, with some having been evaluated only in clinical trials so far, are authorized under emergency procedures. Here, we review these vaccines, compare their properties and discuss the challenges they face, including the emergence of viral variants of concern.

TITLE: COVID-19, des vaccins à la vitesse de l'éclair. ABSTRACT: Un vaccin est nécessaire pour endiguer efficacement, à moyen et long terme, une pandémie comme celle de la COVID-19 (coronavirus disease 2019). Le développement de vaccins contre le virus responsable de la maladie, le SARS-CoV-2 (severe acute respiratory syndrome-coronavirus 2), a été débuté dès la publication de la séquence du génome viral. Ce développement a progressé à une vitesse sans précédent, avec un premier essai clinique réalisé peu de temps après, en mars 2020. Un an plus tard, une dizaine de vaccins reposant sur des concepts différents, dont certains n'avaient été testés que dans des essais cliniques, sont autorisés dans le cadre de procédures d'urgence. Dans cet article, nous passons en revue ces différents vaccins, nous comparons leurs propriétés et nous discutons les défis auxquels ils sont confrontés, en particulier l'émergence de nouveaux variants viraux.

Optimize Prime/Boost Vaccine Strategies: Trained Immunity as a New Player in the Game.

Most vaccines require multiple doses to induce long-lasting protective immunity in a high frequency of vaccines, and to ensure strong both individual and herd immunity. Repetitive immunogenic stimulations not only increase the intensity and durability of adaptive immunity, but also influence its quality. Several vaccine parameters are known to influence adaptive immune responses, including notably the number of immunizations, the delay between them, and the delivery sequence of different recombinant vaccine vectors. Furthermore, the initial effector innate immune response is key to activate and modulate B and T cell responses. Optimization of homologous and heterologous prime/boost vaccination strategies requires a thorough understanding of how vaccination history affects memory B and T cell characteristics. This requires deeper knowledge of how innate cells respond to multiple vaccine encounters. Here, we review how innate cells, more particularly those of the myeloid lineage, sense and respond differently to a 1st and a 2nd vaccine dose, both in an extrinsic and intrinsic manner. On one hand, the presence of primary specific antibodies and memory T cells, whose critical properties change with time after priming, provides a distinct environment for innate cells at the time of re-vaccination. On the other hand, innate cells themselves can exert enhanced intrinsic antimicrobial functions, long after initial stimulation, which is referred to as trained immunity. We discuss the potential of trained innate cells to be game-changers in prime/boost vaccine strategies. Their increased functionality in antigen uptake, antigen presentation, migration, and as cytokine producers, could indeed improve the restimulation of primary memory B and T cells and their differentiation into potent secondary memory cells in response to the boost. A better understanding of trained immunity mechanisms will be highly valuable for harnessing the full potential of trained innate cells, to optimize immunization strategies.

The Route of Vaccine Administration Determines Whether Blood Neutrophils Undergo Long-Term Phenotypic Modifications.

Innate immunity modulates adaptive immunity and defines the magnitude, quality, and longevity of antigen-specific T- and B- cell immune memory. Various vaccine and administration factors influence the immune response to vaccination, including the route of vaccine delivery. We studied the dynamics of innate cell responses in blood using a preclinical model of non-human primates immunized with a live attenuated vaccinia virus, a recombinant Modified vaccinia virus Ankara (MVA) expressing a gag-pol-nef fusion of HIV-1, and mass cytometry. We previously showed that it induces a strong, early, and transient innate response, but also late phenotypic modifications of blood myeloid cells after two months when injected subcutaneously. Here, we show that the early innate effector cell responses and plasma inflammatory cytokine profiles differ between subcutaneous and intradermal vaccine injection. Additionally, we show that the intradermal administration fails to induce more highly activated/mature neutrophils long after immunization, in contrast to subcutaneous administration. Different batches of antibodies, staining protocols and generations of mass cytometers were used to generate the two datasets. Mass cytometry data were analyzed in parallel using the same analytical pipeline based on three successive clustering steps, including SPADE, and categorical heatmaps were compared using the Manhattan distance to measure the similarity between cell cluster phenotypes. Overall, we show that the vaccine per se is not sufficient for the late phenotypic modifications of innate myeloid cells, which are evocative of innate immune training. Its route of administration is also crucial, likely by influencing the early innate response, and systemic inflammation, and vaccine biodistribution.