Maurizio Federico

Endothelial cell dysfunction plays a key role in the pathogenesis of severe and critical COVID-19, leading to a multi-systemic inflammatory disease, and results from the direct interaction of the SARS-CoV-2 Spike proteins with endothelial cells. COVID-19 RNA vaccines encode a recombinant SARS-CoV-2 Spike protein which undergoes systemic biodistribution. No information is however so far available on the direct effects of COVID-19 RNA vaccines on human endothelial cells. In the present study, we exposed cultured human umbilical venous endothelial cells (HUVEC) to the COVID-19 RNA vaccine Spikevax ^TM (Moderna, Inc.), and thereafter we measured the expression of the Spike protein, of the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α, of the adhesion molecules intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1), as well as the attachment of human leukocytes to HUVEC layers. We also assessed the effects of Spikevax ^TM on HUVEC viability. Exposure of HUVEC to the COVID-19 RNA vaccine Spikevax ^TM resulted in effective cell transfection, and subsequent production of the Spike protein, which was expressed in the cells and secreted in the culture medium. Spike protein production was accompanied by increased gene expression of IL-6 and TNF-α and of ICAM-1 and VCAM-1, as well as by increased attachment of leukocytes to HUVEC monolayers. Exposure to the COVID-19 RNA vaccine Spikevax ^TM did not affect HUVEC viability. Our results provide a mechanistic explanation to post-COVID-19 RNA vaccination pathologies resulting from endothelial dysfunction, such as during atherosclerosis, autoimmune inflammation, and systemic inflammatory conditions.

Background/Objectives: African Swine Fever (ASF) represents one of the most serious threats to animal health and global food security. The causative agent of ASF is the African swine fever virus (ASFV), a DNA virus belonging to the Asfarviridae family. Here, we describe ex vivo results for an original anti-ASFV vaccine approach based on the cellular immune response induced by extracellular vesicles (EVs) engineered to express four ASFV proteins. EV engineering was achieved by expressing a DNA vector encoding a biologically inactive HIV-1 Nef protein (Nef^mut), which exhibits unusually high efficiency of incorporation into EVs, even when fused to foreign proteins. Previous studies have demonstrated that intramuscular injection of Nef^mut-based vectors leads to the engineering of Evs, spontaneously released by muscle cells, and induction of antigen-specific CD8⁺ T cell immunity. Methods: We designed DNA vectors expressing the fusion products between Nef^mut and each of the four ASFV structural proteins p30, p54, pp62, and p72. Engineered EVs were molecularly characterized by Western blot and nanotrack analysis, and their potential immunogenicity was assessed by priming and cross-presentation assays. Results: We assessed that the four fusion proteins were successfully expressed in transfected mammalian cells, with the release of valuable amounts of engineered EVs. When immature swine dendritic cells were challenged with the engineered EVs and then co-cultivated with autologous peripheral blood lymphocytes in priming assays, lymphocyte subpopulations specifically reacting against each ASFV antigen were elicited, as detected by an IFN-γ ELISpot assay. In addition, we provide evidence that the Nef^mut-based fusion products incorporated into the engineered EVs can be cross-presented by professional antigen-presenting cells, leading to cross-priming of autologous lymphocytes. Conclusions: These results represent the best premise to go forward with experiments examining immunogenicity and antiviral efficiency in pigs.

Background/Objectives: African Swine Fever (ASF) represents one of the most serious threats to animal health and global food security. The causative agent of ASF is the African swine fever virus (ASFV), a DNA virus belonging to the Asfarviridae family. Here, we describe ex vivo results for an original anti-ASFV vaccine approach based on the cellular immune response induced by extracellular vesicles (EVs) engineered to express four ASFV antigens. EV engineering was achieved by expressing a DNA vector encoding a biologically inactive HIV-1 Nef protein (Nef^mut), which exhibits unusually high efficiency of incorporation into EVs, even when fused to foreign proteins. Previous studies have demonstrated that intramuscular injection of Nef^mut-based vectors leads to the engineering of EVs spontaneously released by muscle cells and induction of antigen-specific CD8⁺ T cell immunity. Methods: We designed DNA vectors expressing the fusion products between Nef^mut and each of the four ASFV structural proteins p³⁰, p⁵⁴, pp⁶², and p⁷². Engineered EVs were molecularly characterized by western blot and nanotrack analysis, and their potential immunogenicity was assessed by priming and cross-presentation assays. Results: We assessed that the four antigens were successfully expressed in transfected mammalian cells, with the release of valuable amounts of engineered EVs. When immature swine dendritic cells were challenged with the engineered EVs and then co-cultivated with autologous peripheral blood lymphocytes in priming assays, lymphocyte subpopulations specifically reacting against each ASFV antigen were elicited, as detected by an IFN-γ ELISpot assay. In addition, we provide evidence that the Nef^mut-based fusion products incorporated into the engineered EVs can be cross-presented by professional antigen-presenting cells, leading to cross-priming of autologous lymphocytes. Conclusions: These results represent the best premise to go forward with experiments of immunogenicity and antiviral efficiency in pigs.

People living with HIV-1 (PLWH) are part of the so-called “fragile” populations to which COVID-19 vaccines were/are strongly recommended. The fact that most widely used COVID-19 vaccines rely on the production of a biologically active SARS-CoV-2 Spike protein expressed by synthetic mRNA poses the relevant question of whether and how this vaccination influences the fate of the HIV-1 reservoir. This report presents a detailed analysis of the literature data on the effects of SARS-CoV-2 Spike and COVID-19 vaccines on HIV-1 latently infected cells. Despite being limited in number, the experimental evidences consistently indicate that vaccine mRNA and/or SARS-CoV-2 Spike can effectively reactivate latent HIV-1. This conclusion has been drawn after “in vitro”, “ex vivo”, and “in vivo” assays, and with virus-associated Spike, soluble Spike, or its intracellular expression, as well as with COVID-19 mRNA vaccines. On the other hand, real-world observations on vaccinated PLWH under antiretroviral therapy (ART) provided evidence of HIV-1 reactivation almost exclusively in PLWH with unsuppressed viremia, as measured in terms of size of the HIV-1 reservoir. Although several issues still need to be clarified through urgent additional investigations, these data suggest the possibility that the Spike protein and/or the vaccine mRNA molecules affect the HIV-1 latency in PLWH.

Self-amplifying RNA-based (saRNA) technology represents the last frontier in using synthetic RNA in vaccinology. Typically, saRNA consists of positive-strand RNA molecules of viral origin (almost exclusively from alphaviruses) where the sequences of structural proteins are replaced with the open reading frame coding the antigen of interest. For in vivo delivery, they are complexed with lipid nanoparticles (LNPs), just like current COVID-19 vaccines based on synthetic messenger RNA (mRNA). Given their ability to amplify themselves inside the cell, optimal intracellular levels of the immunogenic antigen can be achieved by delivering lower amounts of saRNA molecules compared to mRNA-based vaccines. However, the excessive intracellular accumulation of saRNA may represent a relevant drawback since, as already described in alphavirus-infected cells, the recipient cell may react by incorporating excessive RNA molecules into extracellular vesicles (EVs). These EVs can shed and enter neighboring as well as distant cells, where the EV-associated saRNA can start a new replication cycle. This mechanism could lead to an unwanted and unnecessary spread of saRNA throughout the body, posing relevant safety issues. This perspective article discusses the molecular mechanisms through which saRNAs can be transmitted among different cells/tissues. In addition, a simple way to control the possible excessive saRNA intercellular propagation through the co-expression of an EV-anchored protein inhibiting the saRNA replication is proposed. Based on current knowledge, a safety improvement of saRNA-based vaccines appears to be mandatory for their usage in healthy humans.

The action of mRNA-based vaccines requires the expression of the antigen in cells targeted by lipid nanoparticle–mRNA complexes. When the vaccine antigen is not fully retained by the producer cells, its local and systemic diffusion can have consequences depending on both the levels of antigen expression and its biological activity. A peculiarity of mRNA-based COVID-19 vaccines is the extraordinarily high amounts of the Spike antigen expressed by the target cells. In addition, vaccine Spike can be shed and bind to ACE-2 cell receptors, thereby inducing responses of pathogenetic significance including the release of soluble factors which, in turn, can dysregulate key immunologic processes. Moreover, the circulatory immune responses triggered by the vaccine Spike is quite powerful, and can lead to effective anti-Spike antibody cross-binding, as well as to the emergence of both auto- and anti-idiotype antibodies. In this paper, the immunologic downsides of the strong efficiency of the translation of the mRNA associated with COVID-19 vaccines are discussed together with the arguments supporting the idea that most of them can be avoided with the advent of next-generation, mucosal COVID-19 vaccines.

The emergence of tumors associated with defects in immune surveillance often involve the impairment of key functions of T lymphocytes. Therefore, several anticancer immunotherapies have focused on the induction/strengthening of the tumor-specific activity of T cells. In particular, strategies based on immune checkpoint inhibitors, CAR-T cells, and mRNA vaccines share a common goal of inducing/recovering an effective antitumor cytotoxic activity, often resulting in either exhausted or absent in patients’ lymphocytes. In many instances, these approaches have been met with success, becoming part of current clinic protocols. However, the most practiced strategies sometimes also pay significant tolls in terms of adverse events, a lack of target specificity, tumor escape, and unsustainable costs. Hence, new antitumor immunotherapies facing at least some of these issues need to be explored. In this perspective article, the characteristics of a novel CD8⁺ T cell-specific anticancer vaccine strategy based on in vivo-engineered extracellular vesicles are described. How this approach can be exploited to overcome at least some of the limitations of current antitumor immunotherapies is also discussed.

Severe acute respiratory syndrome coronavirus (SARS-CoV)-2 enters the host by infecting nasal ciliated cells. Then, the virus can spread towards the oropharyngeal cavity and the pulmonary tissues. The antiviral adaptive immunity is promptly induced in response to the virus’s detection, with virus-specific T-lymphocytes appearing before antiviral antibodies. Both the breadth and potency of antiviral CD8⁺ T-cell immunity have a key role in containing viral spread and disease severity. Current anti-SARS-CoV-2 vaccines do not impede the virus’s replication in the upper respiratory tract, and there is consensus on the fact that the best potency of the antiviral immune response in both blood and the upper respiratory tract can be reached upon infection in vaccinees (i.e., breakthrough infection). However, whether the antiviral CD8⁺ T-cells developing in response to the breakthrough infection in the upper respiratory tract diffuse to the lungs is also still largely unknown. To fill the gap, we checked the CD8⁺ T-cell immunity elicited after infection of K18-hACE2 transgenic mice both at 3 weeks and 3 months after anti-spike vaccination. Virus-specific CD8⁺ T-cell immunity was monitored in both blood and the lungs before and after infection. By investigating the de novo generation of the CD8⁺ T-cells specific for SARS-CoV-2 viral proteins, we found that both membrane (M) and/or nucleocapsid (N)-specific CD8⁺ T-cells were induced at comparable levels in the blood of both unvaccinated and vaccinated mice. Conversely, N-specific CD8⁺ T-cells were readily found in the lungs of the control mice but were either rare or absent in those of vaccinated mice. These results support the idea that the hybrid cell immunity developing after asymptomatic/mild breakthrough infection strengthens the antiviral cell immunity in the lungs only marginally, implying that the direct exposition of viral antigens is required for the induction of an efficient antiviral cell immunity in the lungs.

Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)-2 enters the host by infecting nasal ciliated cells. Then, the virus can spread towards the oropharyngeal cavity and the pulmonary tissues. The antiviral adaptive immunity is promptly induced in response to virus detection, with virus-specific T lymphocytes appearing before antiviral antibodies. Both breadth and potency of the antiviral CD8+ T cell immunity have a key role in containing viral spread and disease severity. Current anti-SARS-CoV-2 vaccines do not impede the virus replication in the upper respiratory tract, and there is consensus on the fact that the best potency of the antiviral immune response in both blood and upper respiratory tract can be reached upon infection in vaccinees (i.e., breakthrough infection). However, whether the antiviral CD8+ T cells developing in response to the breakthrough infection in the upper respiratory tract diffuse to the lungs also is still largely unknown. To fill the gap, we checked the CD8+ T cell immunity elicited after infection of K18-hACE2 transgenic mice both 3 weeks and 3 months after anti-Spike vaccination. The virus-specific CD8+ T cell immunity was monitored in both blood and the lungs before and after infection. By investigating the de novo generation of CD8+ T cells specific for SARS-CoV-2 viral proteins, we found that both membrane (M) and/or nucleocapsid (N)-specific CD8+ T cells were induced at comparable levels in blood of both unvaccinated and vaccinated mice. Conversely, N-specific CD8+ T cells were readily found in the lungs of control mice, but were either rare or absent in those of vaccinated mice. These results support the idea that the hybrid cell immunity developing after asymptomatic/mild breakthrough infection strengthens the antiviral cell immunity at lungs only marginally, implying that the direct exposition of the viral antigens is required for the induction of an efficient antiviral cell immunity in the lungs.

Induction of effective immunity in the lungs should be a requisite for any vaccine designed to control the severe pathogenic effects generated by respiratory infectious agents. We recently provided evidence that the generation of endogenous extracellular vesicles (EVs) engineered for the incorporation of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)-2 Nucleocapsid (N) protein induced immunity in the lungs of K18-hACE2 transgenic mice, which then can survive the lethal virus infection. However, nothing is known about the ability of the N-specific CD8⁺ T cell immunity in controlling viral replication in the lungs, a major pathogenic signature of severe disease in humans. To fill the gap, we investigated the immunity generated in the lungs by N-engineered EVs in terms of induction of N-specific effectors and resident memory CD8⁺ T lymphocytes before and after virus challenge carried out three weeks and three months after boosting. At the same time points, viral replication extents in the lungs were evaluated. Three weeks after the second immunization, virus replication was reduced in mice best responding to vaccination by more than 3-logs compared to the control group. The impaired viral replication matched with a reduced induction of Spike-specific CD8⁺ T lymphocytes. The antiviral effect appeared similarly strong when the viral challenge was carried out 3 months after boosting, and associated with the persistence of N-specific CD8⁺ T-resident memory lymphocytes. In view of the quite low mutation rate of the N protein, the present vaccine strategy has the potential to control the replication of all emerging variants.