Virus-like particles (VLPs) are a versatile, safe, and highly immunogenic vaccine platform. Recently, there are developmental vaccines targeting SARS-CoV-2, the causative agent of COVID-19. The COVID-19 pandemic affected humanity worldwide, bringing out incomputable human and financial losses. The race for better, more efficacious vaccines is happening almost simultaneously as the virus increasingly produces variants of concern (VOCs). The VOCs Alpha, Beta, Gamma, and Delta share common mutations mainly in the spike receptor-binding domain (RBD), demonstrating convergent evolution, associated with increased transmissibility and immune evasion. Thus, the identification and understanding of these mutations is crucial for the production of new, optimized vaccines. The use of a very flexible vaccine platform in COVID-19 vaccine development is an important feature that cannot be ignored. Incorporating the spike protein and its variations into VLP vaccines is a desirable strategy as the morphology and size of VLPs allows for better presentation of several different antigens. Furthermore, VLPs elicit robust humoral and cellular immune responses, which are safe, and have been studied not only against SARS-CoV-2 but against other coronaviruses as well. Here, we describe the recent advances and improvements in vaccine development using VLP technology.

Neglected Tropical Diseases (NTDs) are a group of diseases that are highly prevalent in tropical and subtropical regions, and closely associated with poverty and marginalized populations. Infectious diseases affect over 1.6 billion people annually, and vaccines are the best prophylactic tool against them. Along with NTDs, emerging and reemerging infectious diseases also threaten global public health, as they can unpredictably result in pandemics. The recent advances in vaccinology allowed the development and licensing of new vaccine platforms that can target and prevent these diseases. In this work, we discuss the advances in vaccinology and some of the difficulties found in the vaccine development pipeline for selected NTDs and emerging and reemerging infectious diseases, including HIV, Dengue, Ebola, Chagas disease, malaria, leishmaniasis, zika, and chikungunya.

The mechanisms through which allergies can be inhibited after preconception immunization with allergens are not fully understood. We aimed to evaluate whether maternal immunization can induce a regulatory B (B10) cell population in offspring in concert with allergy inhibition. C57BL/6 females were or were not immunized with OVA and were mated with normal WT males. Their offspring were evaluated at 3 days of age or 20 days after neonatal immunization. Human peripheral B cells from atopic and non-atopic individuals were also evaluated. Preconception OVA immunization induced B10 cells in offspring, and IL-10 production appeared to be critical for FcγRIIB upregulation in offspring B cells. Murine and human IL-10-producing B cells responded in vitro to IgG according to the atopic repertoire of the cells. Our results reveal that maternal immunization induces allergen-specific B10 cells in offspring and a pivotal role for the IgG repertoire in IL-10 production by murine and human B cells.

Regulatory B (B10) cells can control several inflammatory diseases, including allergies; however, the origin of peripheral B10 cells is not fully understood, and the involvement of primary lymphoid organs (PLOs) as a primary site of maturation is not known. Here, using a murine model of allergy inhibition mediated by maternal immunization with ovalbumin (OVA), we aimed to evaluate whether B10 cells can mature in the thymus and whether IgG can mediate this process. Female mice were immunized with OVA, and offspring thymus, bone marrow, spleen, lung, and serum samples were evaluated at different times and after passive transfer of purified IgG or thymocytes. A translational approach was implemented using human nonatopic thymus samples, nonatopic peripheral blood mononuclear cells (PBMCs), and IgG from atopic or nonatopic individuals. Based on the expression of CD1d on B cells during maturation stages, we suggest that B10 cells can also mature in the murine thymus. Murine thymic B10 cells can be induced in vitro and in vivo by IgG and be detected in the spleen and lungs in response to an allergen challenge. Like IgG from atopic individuals, human IgG from nonatopic individuals can induce B10 cells in the infant thymus and adult PBMCs. Our observations suggest that B10 cells may mature in the thymus and that this mechanism may be mediated by IgG in both humans and mice. These observations may support the future development of IgG-based immunoregulatory therapeutic strategies.

Over the last decade, our group has demonstrated that murine preconception immunization with allergens has a protective effect on allergy development in offspring. The murine model used in the present study allowed us to compare allergy induction by ovalbumin (OVA) and dust mite extract from Dermatophagoides pteronyssinus (Dp). Female mice were immunized with OVA or Dp. Pups from immunized and non-immune mothers were immunized at 3 days old (do) with the same antigen used for the maternal immunization. The offspring were analyzed at 20 do. Preconceptional immunization with OVA or Dp did not increase maternal IgE serum levels, although the immunizations induced an increase in allergen-specific IgG1 Ab levels. Offspring serum analyses revealed that maternal immunization with OVA suppressed IgE production only in offspring immunized with OVA. Both preconception immunization protocols inhibited cellular influx into the airways of immunized offspring compared with controls. Similar frequencies of offspring IgM + B cells were found in the OVA- and Dp-immunized groups compared with their respective control groups. Moreover, preconception immunization with OVA enhanced FcγRIIb expression on OVA-immunized offspring B cells. In contrast, decreased FcγRIIb expression was detected on Dp-immunized offspring B cells compared with cells from the offspring of non-immune mothers. Together, these results show that preconception OVA immunization and Dp immunization can inhibit allergy development but have opposite effects on FcγRIIb expression on offspring B cells.

The COVID-19 vaccinations have played a significant role in controlling the pandemic. To elucidate their impact on the immune system, a COVID-19 vaccination atlas was developed through an integrative systems vaccinology approach. The atlas includes both healthy individuals and those infected with or without prior vaccination, and covers the administration of five vaccines in different regimens: Covilo®, Zifivax®, Vaxzebria® or Covishield®, Spikevax®, and Comirnaty®. Critical markers were identified to discriminate the different types of vaccines and infection, in which infection was associated with GATA3, ZNF3, KMT2A, ASXL1, SP100, and GZMM, and vaccine types were marked by ITGAM, ACTG1, LGALS3, and STAT5B. Additionally, the immunological signatures of heterologous vaccination and infection were described, and it was also shown how a full vaccination regimen markedly limited the shift of immune responses during natural infection, thereby constraining disease progression. Finally, the common transcripts shared across COVID-19 vaccines and vaccines against other pathogens were described.