Bacterial Membrane Vesicles in Pneumonia: From Mediators of Virulence to Innovative Vaccine Candidates

Pneumonia due to respiratory infection with most prominently bacteria, but also viruses, fungi, or parasites is the leading cause of death worldwide among all infectious disease in both adults and infants. The introduction of modern antibiotic treatment regimens and vaccine strategies has helped to lower the burden of bacterial pneumonia, yet due to the unavailability or refusal of vaccines and antimicrobials in parts of the global population, the rise of multidrug resistant pathogens, and high fatality rates even in patients treated with appropriate antibiotics pneumonia remains a global threat. As such, a better understanding of pathogen virulence on the one, and the development of innovative vaccine strategies on the other hand are once again in dire need in the perennial fight of men against microbes. Recent data show that the secretome of bacteria consists not only of soluble mediators of virulence but also to a significant proportion of extracellular vesicles—lipid bilayer-delimited particles that form integral mediators of intercellular communication. Extracellular vesicles are released from cells of all kinds of organisms, including both Gram-negative and Gram-positive bacteria in which case they are commonly termed outer membrane vesicles (OMVs) and membrane vesicles (MVs), respectively. (O)MVs can trigger inflammatory responses to specific pathogens including S. pneumonia, P. aeruginosa, and L. pneumophila and as such, mediate bacterial virulence in pneumonia by challenging the host respiratory epithelium and cellular and humoral immunity. In parallel, however, (O)MVs have recently emerged as auspicious vaccine candidates due to their natural antigenicity and favorable biochemical properties. First studies highlight the efficacy of such vaccines in animal models exposed to (O)MVs from B. pertussis, S. pneumoniae, A. baumannii, and K. pneumoniae. An advanced and balanced recognition of both the detrimental effects of (O)MVs and their immunogenic potential could pave the way to novel treatment strategies in pneumonia and effective preventive approaches.

Mapping the technological landscape of SARS, MERS, and SARS-CoV-2 vaccines

PURPOSE

The last two decades have seen the emergence of several viral outbreaks. Some of them are the severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and severe acute respiratory syndrome 2 (SARS-CoV2) - the cause of the coronavirus disease 2019 (COVID-19). Ever, vaccines for emergency use have been authorized for the control and prevention of COVID-19. Currently, there is an urgent need to develop a vaccine for prophylaxis of COVID-19 and for other future epidemics.

METHODS

This review describes patented vaccines for SARS and MERS-CoV and vaccines developed and approved for emergency use against the new coronavirus (COVID-19). The European Patent Office and the World Intellectual Property Organization were the patent databases used using specific terms. In addition, another search was carried out in the Clinical Trials in search of ongoing clinical studies focused on the COVID-19 vaccine.

RESULTS

The patent search showed that most vaccines are based on viral vector platforms, nucleic acids, or protein subunits. The review also includes an overview of completed and ongoing clinical trials for SARS-CoV-2 in several countries.

CONCLUSION

The information provided here lists vaccines for other types of coronavirus that have been used in the development of vaccines for COVID-19.

Membrane vesicles from periodontal pathogens and their potential roles in periodontal disease and systemic illnesses

Periodontium is an ordered ecological system where a dynamic equilibrium exists between oral microorganisms and the host defense system, and periodontal disease occurs whenever the balance is broken. Periodontal pathogens mainly include gram-negative anaerobic bacteria and emerging gram-positive microbes, which have a large variety of virulence factors and influence disease initiation and progression. Recently, different types of bacterial membrane vesicles (MVs), formed by bubbling of membrane materials from living cells or in conditions of endolysin-triggered cell death, have gained interests as a novel virulence factor for periodontopathogens. MVs load multiple sorted cargo molecules, such as proteins, lipids, and genetic materials, and actively participate in toxin transport, signal delivery, and periodontal disease pathogenesis. Since periodontitis is recognized as a risk factor for many systemic diseases, periodontal MVs could work as a bridge for periodontal diseases and systemic illnesses. Furthermore, MVs with unique nature and advantages are promising candidates as vaccines and drug delivery vehicles. In this review, we provided an overview of different types and compositions of periodontal MVs, described their involvements in the pathogenesis of periodontitis and several general diseases, and discussed potential applications of periodontal MVs in vaccination and drug delivery.

Cutaneous reactions reported after Moderna and Pfizer COVID-19 vaccination: A registry-based study of 414 cases

Background

Cutaneous reactions after messenger RNA (mRNA)-based COVID-19 vaccines have been reported but are not well characterized.

Objective

To evaluate the morphology and timing of cutaneous reactions after mRNA COVID-19 vaccines.

Methods

A provider-facing registry-based study collected cases of cutaneous manifestations after COVID-19 vaccination.

Results

From December 2020 to February 2021, we recorded 414 cutaneous reactions to mRNA COVID-19 vaccines from Moderna (83%) and Pfizer (17%). Delayed large local reactions were most common, followed by local injection site reactions, urticarial eruptions, and morbilliform eruptions. Forty-three percent of patients with first-dose reactions experienced second-dose recurrence. Additional less common reactions included pernio/chilblains, cosmetic filler reactions, zoster, herpes simplex flares, and pityriasis rosea-like reactions.

Limitations

Registry analysis does not measure incidence. Morphologic misclassification is possible.

Conclusions

We report a spectrum of cutaneous reactions after mRNA COVID-19 vaccines. We observed some dermatologic reactions to Moderna and Pfizer vaccines that mimicked SARS-CoV-2 infection itself, such as pernio/chilblains. Most patients with first-dose reactions did not have a second-dose reaction and serious adverse events did not develop in any of the patients in the registry after the first or second dose. Our data support that cutaneous reactions to COVID-19 vaccination are generally minor and self-limited, and should not discourage vaccination.

Vaccine Development for Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS), which is caused by SFTS virus (SFTSV), is a tick-borne emerging zoonosis with a high case-fatality rate. At present, there is no approved SFTS vaccine, although the development of a vaccine would be one of the best strategies for preventing SFTS. This article focused on studies aimed at establishing small animal models of SFTS that are indispensable for evaluating vaccine candidates, developing these vaccine candidates, and establishing more practical animal models for evaluation. Innate immune-deficient mouse models, a hamster model, an immunocompetent ferret model and a cat model have been developed for SFTS. Several vaccine candidates for SFTS have been developed, and their efficacy has been confirmed using these animal models. The candidates consist of live-attenuated virus-based, viral vector-based, or DNA-based vaccines. SFTS vaccines are expected to be used for humans and companion dogs and cats. Hence for practical use, the vaccine candidates should be evaluated for efficacy using not only nonhuman primates but also dogs and cats. There is no practical nonhuman primate model of SFTS; however, the cat model is available to evaluate the efficacy of these candidate SFTS vaccines on domesticated animals.

Induction of Robust and Specific Humoral and Cellular Immune Responses by Bovine Viral Diarrhea Virus Virus-Like Particles (BVDV-VLPs) Engineered with Baculovirus Expression Vector System

Bovine viral diarrhea virus (BVDV) is an important animal pathogen that affects cattle. Infections caused by the virus have resulted in substantial economic losses and outbreaks of BVDV are reported globally. Virus-like particles (VLPs) are promising vaccine technology largely due to their safety and strong ability to elicit robust immune responses. In this study, we developed a strategy to generate BVDV-VLPs using a baculovirus expression vector system (BEVS). We were able to assemble BVDV-VLPs composed of dimerized viral proteins E2 and E^rns, and the VLPs were spherical particles with the diameters of about 50 nm. Mice immunized with 15 μg of VLPs adjuvanted with ISA201 elicited higher levels of E2-specific IgG, IgG1, and IgG2a antibodies as well as higher BVDV-neutralizing activity in comparison with controls. Re-stimulation of the splenocytes collected from mice immunized with VLPs led to significantly increased levels of CD3⁺CD4⁺T cells and CD3⁺CD8⁺T cells. In addition, the splenocytes showed dramatically enhanced proliferation and the secretion of Th1-associated IFN-γ and Th2-associated IL-4 compared to that of the unstimulated control group. Taken together, our data indicate that BVDV-VLPs efficiently induced BVDV-specific humoral and cellular immune responses in mice, showing a promising potential of developing BVDV-VLP-based vaccines for the prevention of BVDV infections.

Severe, Refractory Immune Thrombocytopenia Occurring After SARS-CoV-2 Vaccine

The rollout of the SARS-CoV-2 vaccine is underway, and millions have already been vaccinated. At least 25 reports of "immune thrombocytopenia" (ITP) or "thrombocytopenia" following the Moderna or Pfizer vaccine have been added to the Vaccine Adverse Event Reporting System (VAERS) in the US. ITP is a rare but known complication of several vaccinations. SARS-CoV-2 vaccine is new, with a novel mechanism of action, and understanding the epidemiology, clinical manifestations, treatment success and natural history of post-vaccination thrombocytopenia is evolving. We report a 74-year-old man who developed refractory thrombocytopenia within one day of receiving the Moderna SARS-CoV-2 vaccine. Several hours after vaccination, he developed significant epistaxis and cutaneous purpura. Severe thrombocytopenia was documented the following day, and he developed extremity weakness and encephalopathy with facial muscle weakness. Over a 14-day period, thrombocytopenia was treated first with high dose dexamethasone, intravenous immunoglobulin, platelet transfusions, rituximab, plasma exchange (for presumed acute inflammatory demyelinating polyneuropathy (AIDP)), and four daily doses of the thrombopoietin receptor agonist (TPO-RA) eltrombopag (Promacta™), without a platelet response. Three days later, he received the TPO-RA romiplostim (Nplate™). Five days later, his platelet count began to rise and by post-vaccination day 25, his platelet count was in the normal range. Thrombocytopenia was refractory to frontline and second-line treatment. The eventual rise in his platelet count suggests that one or both TPO-RAs may have impacted platelet recovery. Possibly, but less likely given the temporality, the drug-induced thrombocytopenia was subsiding. The aggressive use of immunosuppressive treatment may jeopardize the intended purpose of the SARS-CoV-2 vaccine, and earlier use of non-immunosuppressive second-line treatment for vaccine-related severe thrombocytopenia, such as with TPO-RAs, should be considered. While it is imperative to continue the global vaccination program, vigilance to the occurrence of post-vaccination severe thrombocytopenia is warranted.

Transgene Delivery to Human Induced Pluripotent Stem Cells Using Nanoparticles

Human induced pluripotent stem cells (hiPSCs) and hiPSCs-derived cells have the potential to revolutionize regenerative and precision medicine. Genetically reprograming somatic cells to generate hiPSCs and genetic modification of hiPSCs are considered the key procedures for the study and application of hiPSCs. However, there are significant technical challenges for transgene delivery into somatic cells and hiPSCs since these cells are known to be difficult to transfect. The existing methods, such as viral transduction and chemical transfection, may introduce significant alternations to hiPSC culture which affect the potency, purity, consistency, safety, and functional capacity of hiPSCs. Therefore, generation and genetic modification of hiPSCs through non-viral approaches are necessary and desirable. Nanotechnology has revolutionized fields from astrophysics to biology over the past two decades. Increasingly, nanoparticles have been used in biomedicine as powerful tools for transgene and drug delivery, imaging, diagnostics, and therapeutics. The most successful example is the recent development of SARS-CoV-2 vaccines at warp speed to combat the 2019 coronavirus disease (COVID-19), which brought nanoparticles to the center stage of biomedicine and demonstrated the efficient nanoparticle-mediated transgene delivery into human body. Nanoparticles have the potential to facilitate the transgene delivery into the hiPSCs and offer a simple and robust approach. Nanoparticle-mediated transgene delivery has significant advantages over other methods, such as high efficiency, low cytotoxicity, biodegradability, low cost, directional and distal controllability, efficient in vivo applications, and lack of immune responses. Our recent study using magnetic nanoparticles for transfection of hiPSCs provided an example of the successful applications, supporting the potential roles of nanoparticles in hiPSC biology. This review discusses the principle, applications, and significance of nanoparticles in the transgene delivery to hiPSCs and their successful application in the development of COVID-19 vaccines.

Rational Vaccine Design in Times of Emerging Diseases: The Critical Choices of Immunological Correlates of Protection, Vaccine Antigen and Immunomodulation

Vaccines are the most effective medical intervention due to their continual success in preventing infections and improving mortality worldwide. Early vaccines were developed empirically however, rational design of vaccines can allow us to optimise their efficacy, by tailoring the immune response. Establishing the immune correlates of protection greatly informs the rational design of vaccines. This facilitates the selection of the best vaccine antigens and the most appropriate vaccine adjuvant to generate optimal memory immune T cell and B cell responses. This review outlines the range of vaccine types that are currently authorised and those under development. We outline the optimal immunological correlates of protection that can be targeted. Finally we review approaches to rational antigen selection and rational vaccine adjuvant design. Harnessing current knowledge on protective immune responses in combination with critical vaccine components is imperative to the prevention of future life-threatening diseases.

Live-attenuated Vaccines Prevent Respiratory Syncytial Virus-associated Illness in Young Children

Rationale: Active immunization is needed to protect infants and young children against respiratory syncytial virus (RSV). Rationally designed live-attenuated RSV vaccines are in clinical development.Objectives: Develop preliminary estimates of vaccine efficacy, assess durability of antibody responses to vaccination and "booster" responses after natural RSV infection, and determine sample sizes needed for more precise estimates of vaccine efficacy.Methods: We analyzed data from seven phase 1 trials of live-attenuated RSV vaccines in 6- to 24-month-old children (n = 239).Measurements and Main Results: The five vaccine regimens that induced neutralizing antibody responses in ≥80% of vaccinees (defined post hoc as "more promising") protected against RSV-associated medically attended acute respiratory illness (RSV-MAARI) and medically attended acute lower respiratory illness (RSV-MAALRI) and primed for potent anamnestic responses upon natural exposure to wild-type RSV. Among recipients of "more promising" RSV vaccines, efficacy against RSV-MAARI was 67% (95% confidence interval [CI], 24 to 85; P = 0.008) and against RSV-MAALRI was 88% (95% CI, -9 to 99; P = 0.04). A greater than or equal to fourfold increase in RSV serum neutralizing antibody following vaccination was strongly associated with protection against RSV-MAARI (odds ratio, 0.26; 95% CI, 0.09 to 0.75; P = 0.014) and RSV-MAALRI; no child with a greater than or equal to fourfold increase developed RSV-MAALRI. Rates of RSV-MAARI and RSV-MAALRI in placebo recipients were 21% and 7%, respectively. Given these rates, a study of 540 RSV-naive children would have 90% power to demonstrate ≥55% efficacy against RSV-MAARI and ≥80% efficacy against RSV-MAALRI; if rates were 10% and 3%, a study of 1,300 RSV-naive children would be needed.Conclusions: Rapid development of a live-attenuated RSV vaccine could contribute substantially to reducing the global burden of RSV disease.

Modular complement assemblies for mitigating inflammatory conditions

Complement protein C3dg, a key linkage between innate and adaptive immunity, is capable of stimulating both humoral and cell-mediated immune responses, leading to considerable interest in its use as a molecular adjuvant. However, the potential of C3dg as an adjuvant is limited without ways of controllably assembling multiple copies of it into vaccine platforms. Here, we report a strategy to assemble C3dg into supramolecular nanofibers with excellent compositional control, using β-tail fusion tags. These assemblies were investigated as therapeutic active immunotherapies, which may offer advantages over existing biologics, particularly toward chronic inflammatory diseases. Supramolecular assemblies based on the Q11 peptide system containing β-tail-tagged C3dg, B cell epitopes from TNF, and the universal T cell epitope PADRE raised strong antibody responses against both TNF and C3dg, and prophylactic immunization with these materials significantly improved protection in a lethal TNF-mediated inflammation model. Additionally, in a murine model of psoriasis induced by imiquimod, the C3dg-adjuvanted nanofiber vaccine performed as well as anti-TNF monoclonal antibodies. Nanofibers containing only β-tail-C3dg and lacking the TNF B cell epitope also showed improvements in both models, suggesting that supramolecular C3dg, by itself, played an important therapeutic role. We observed that immunization with β-tail-C3dg caused the expansion of an autoreactive C3dg-specific T cell population, which may act to dampen the immune response, preventing excessive inflammation. These findings indicate that molecular assemblies displaying C3dg warrant further development as active immunotherapies.

Single-component, self-assembling, protein nanoparticles presenting the receptor binding domain and stabilized spike as SARS-CoV-2 vaccine candidates

Vaccination against SARS-CoV-2 provides an effective tool to combat the COIVD-19 pandemic. Here, we combined antigen optimization and nanoparticle display to develop vaccine candidates for SARS-CoV-2. We first displayed the receptor-binding domain (RBD) on three self-assembling protein nanoparticle (SApNP) platforms using the SpyTag/SpyCatcher system. We then identified heptad repeat 2 (HR2) in S2 as the cause of spike metastability, designed an HR2-deleted glycine-capped spike (S2GΔHR2), and displayed S2GΔHR2 on SApNPs. An antibody column specific for the RBD enabled tag-free vaccine purification. In mice, the 24-meric RBD-ferritin SApNP elicited a more potent neutralizing antibody (NAb) response than the RBD alone and the spike with two stabilizing proline mutations in S2 (S2P). S2GΔHR2 elicited two-fold-higher NAb titers than S2P, while S2GΔHR2 SApNPs derived from multilayered E2p and I3-01v9 60-mers elicited up to 10-fold higher NAb titers. The S2GΔHR2-presenting I3-01v9 SApNP also induced critically needed T-cell immunity, thereby providing a promising vaccine candidate.

Strategies for Disseminating and Implementing COVID-19 Vaccines in Rural Areas

The United States has well-documented rural–urban health disparities, and it is imperative that these are not exacerbated by an inefficient rollout of coronavirus disease 2019 (COVID-19) vaccines to rural areas. In addition to the preexisting barriers to delivering and receiving health care in rural areas, such as high patient:provider ratios and long geographic distances between patients and providers, rural residents are significantly more likely to say they have no intention of receiving a COVID-19 vaccine, compared with urban residents. To overcome these barriers and ensure that rural residents receive the vaccine, officials and communities should look to previous research on how to communicate vaccine information and implement successful vaccination programs in rural areas for guidance and concrete strategies to use in their local efforts.

Graphical Abstract

Effects of SARS-CoV-2 variants on vaccine efficacy and response strategies

INTRODUCTION

As the global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic continues to spread, several variants have emerged. Variants B.1.1.7 and B.1.351 have attracted significant attention owing to their widespread transmission and possible immune evasion. A total of 19 SARS-CoV-2 vaccines based on original strains have entered clinical studies, including nine vaccines that have obtained emergency use or conditional marketing authorizations. However, newly emerging variants may affect their protective efficacy. Decreased efficacy of the Novartis, Johnson & Johnson, and AstraZeneca vaccines against B.1.351 has been reported. The spread of variants creates a tremendous challenge for the prevention and control of the SARS-CoV-2 pandemic via vaccination. Several response strategies, including accelerating massive rollouts of current vaccines, increasing vaccine immunogenicity by increasing vaccination doses, and accelerating next-generation vaccines against variants, have been suggested.

AREAS COVERED

SARS-CoV-2 vaccine efficacy against variants and response strategies for emerging variants.

EXPERT OPINION

Current SARS-CoV-2 vaccines authorized for emergency use or under clinical trials have shown certain advantages in providing adequate protection against new variants. We analyzed the effects of reported variants on neutralizing antibodies and the protective efficacy of different vaccines and propose strategies for applying current vaccines against variants and developing next-generation vaccines.

Factors Influencing the Efficacy of COVID-19 Vaccines: A Quantitative Synthesis of Phase III Trials

To date, there is still a paucity of data from Phase III trials concerning the efficacy of vaccines against COVID-19. Furthermore, no studies investigated the variables that may modulate the efficacy of vaccination. The aim of this analysis was to assess whether there are modifying factors that may potentially influence the clinical efficacy of COVID-19 vaccines. A quantitative synthesis of data from Phase III trials was performed via pairwise and network meta-analyses, along with meta-regression analysis. Data from Phase III trials are currently available only for AZD1222, BNT162b2, mRNA-1237, and Sputnik V. Vaccination resulted to be generally effective (90.0%, 95%CI 72.6-96.4; p < 0.001), although the efficacy of AZD1222 (62.1%) introduced a significant level of heterogeneity in the meta-analysis (I2 92.17%, p < 0.001). No significant modifying factors resulted from the meta-regression analysis. However, considering the mRNA-based vaccines, a trend toward significance (p = 0.081) resulted for age. The network meta-analysis provided the following rank of effectiveness: BNT162b2 ≃ mRNA-1273 > Sputnik V >> AZD1222. In conclusion, no modifying factors seem to modulate the efficacy of vaccines against COVID-19. This quantitative synthesis will need to be updated as soon as further clinical results on the efficacy profile are available from Phase III trials for further licensed COVID-19 vaccines.

Interim seasonal influenza vaccine effectiveness estimates as proxy for final estimates: analysis of systematically identified matched pairs of interim/final estimates from test-negative design studies in outpatient settings from 2010/11 to 2018/19

OBJECTIVES

Limited time for seasonal influenza vaccine development means that the World Health Organization has to consider interim (early) rather than final vaccine effectiveness (VE) estimates in deciding influenza vaccine composition. We assessed agreement between interim and final VE estimates, and factors that may determine a substantial difference (≥10%) between point estimates.

METHODS

This was a mixed methods study. We systematically searched, identified, and matched interim/final VE studies of test-negative design (TND) type in outpatient settings after the 2009/10 influenza pandemic. The chi-square statistic (χ2) was used to assess the statistical significance of the difference between paired interim/final VE estimates. We calculated the difference between point estimates and used multivariable logistic regression to assess factors that may determine a substantial difference.

RESULTS

We identified 68 interim/final VE pairs. There was no statistically significant difference between almost all compared pairs. An inconsistent statistical model for interim/final VE estimation and interim VE estimation before the epidemic peak increased the odds of having a substantial difference between estimates.

CONCLUSION

: Interim influenza VE appears to be sufficient for vaccine composition decision-making. Consistency in interim/final VE estimation, and interim VE estimation during/after epidemic peak may increase agreement between the VE estimates.

Aluminium contact allergy without vaccination granulomas: A systematic review and meta-analysis

Aluminium contact allergy is mainly seen as granulomas following immunization with aluminium-adsorbed vaccines and contact allergy following epicutaneous exposure may be overlooked. To investigate the prevalence of aluminium allergy confirmed by patch testing, with no association with vaccination granulomas, and explore whether epicutaneous exposure to aluminium can contribute to allergic contact dermatitis. Two authors independently searched PubMed and MEDLINE (OVID) for case studies on contact allergy to aluminium proven by patch testing. Age-stratified meta-analyses to calculate the pooled prevalence were performed. Twenty-five studies describing a total of 73 cases were included in the review. Seven studies were suitable for meta-analyses. The prevalence of aluminium contact allergy was 5.61% (95% confidence interval [CI] 0.12%-11.08%) for children and 0.36% (95% CI 0.04%-0.67%) for adults. The studies described a variety of epicutaneous exposures, where metallic aluminium, topical medicaments, and deodorants were the main sources. Aluminium sensitization without a known exposure source was described in 10 of the 25 articles. The prevalence of aluminium contact allergy in the general public may be higher than expected and not solely related to vaccination granulomas. However, the clinical relevance is rare if not related to granulomas.

Herpes Zoster in an Immunocompetent Child without a History of Varicella

Herpes zoster is a relatively rare infectious disease in the pediatric population, as compared with adults, which is due to the reactivation of latent Varicella-Zoster virus. We report a 7-year-old child without any history of varicella, who first experienced skin pain and later presented skin lesions in dermatomal distribution. Finally, the patient was diagnosed with herpes zoster. We aim to emphasize that herpes zoster could occur in immunocompetent children and may be due to the reactivation of the vaccine strain or previous subclinical infection.

Engineering Vaccines for Tissue-Resident Memory T Cells

In recent years, tissue-resident memory T cells (TRM) have attracted significant attention in the field of vaccine development. Distinct from central and effector memory T cells, TRM cells take up residence in home tissues such as the lung or urogenital tract and are ideally positioned to respond quickly to pathogen encounter. TRM have been found to play a role in the immune response against many globally important infectious diseases for which new or improved vaccines are needed, including influenza and tuberculosis. It is also increasingly clear that TRM play a pivotal role in cancer immunity. Thus, vaccines that can generate this memory T cell population are highly desirable. The field of immunoengineering-that is, the application of engineering principles to study the immune system and design new and improved therapies that harness or modulate immune responses-is ideally poised to provide solutions to this need for next-generation TRM vaccines. This review covers recent developments in vaccine technologies for generating TRM and protecting against infection and cancer, including viral vectors, virus-like particles, and synthetic and natural biomaterials. In addition, it offers critical insights on the future of engineering vaccines for tissue-resident memory T cells.

Emerging Role of Exosomes in Tuberculosis: From Immunity Regulations to Vaccine and Immunotherapy

Exosomes are cell-derived nanovesicles carrying protein, lipid, and nucleic acid for secreting cells, and act as significant signal transport vectors for cell-cell communication and immune modulation. Immune-cell-derived exosomes have been found to contain molecules involved in immunological pathways, such as MHCII, cytokines, and pathogenic antigens. Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), remains one of the most fatal infectious diseases. The pathogen for tuberculosis escapes the immune defense and continues to replicate despite rigorous and complicate host cell mechanisms. The infected-cell-derived exosomes under this circumstance are found to trigger different immune responses, such as inflammation, antigen presentation, and activate subsequent pathways, highlighting the critical role of exosomes in anti-MTB immune response. Additionally, as a novel kind of delivery system, exosomes show potential in developing new vaccination and treatment of tuberculosis. We here summarize recent research progress regarding exosomes in the immune environment during MTB infection, and further discuss the potential of exosomes as delivery system for novel anti-MTB vaccines and therapies.

Depth of tumor implantation affects response to in situ vaccination in a syngeneic murine melanoma model

An important component of research using animal models is ensuring rigor and reproducibility. This study was prompted after two experimenters performing virtually identical studies obtained different results when syngeneic B78 murine melanoma cells were implanted into the skin overlying the flank and treated with an in situ vaccine (ISV) immunotherapy. Although both experimenters thought they were using identical technique, we determined that one was implanting the tumors intradermally (ID) and the other was implanting them subcutaneously (SC). Though the baseline in vivo immunogenicity of tumors can depend on depth of their implantation, the response to immunotherapy as a function of tumor depth, particularly in immunologically 'cold' tumors, has not been well studied. The goal of this study was to evaluate the difference in growth kinetics and response to immunotherapy between identically sized melanoma tumors following ID versus SC implantation. We injected C57BL/6 mice with syngeneic B78 melanoma cells either ID or SC in the flank. When tumors reached 190-230 mm3, they were grouped into a 'wave' and treated with our previously published ISV regimen (12 Gy local external beam radiation and intratumoral hu14.18-IL2 immunocytokine). Physical examination demonstrated that ID-implanted tumors were mobile on palpation, while SC-implanted tumors became fixed to the underlying fascia. Histologic examination identified a critical fascial layer, the panniculus carnosus, which separated ID and SC tumors. SC tumors reached the target tumor volume significantly faster compared with ID tumors. Most ID tumors exhibited either partial or complete response to this immunotherapy, whereas most SC tumors did not. Further, the 'mobile' or 'fixed' phenotype of tumors predicted response to therapy, regardless of intended implantation depth. These findings were then extended to additional immunotherapy regimens in four separate tumor models. These data indicate that the physical 'fixed' versus 'mobile' characterization of the tumors may be one simple method of ensuring homogeneity among implanted tumors prior to initiation of treatment. Overall, this short report demonstrates that small differences in depth of tumor implantation can translate to differences in response to immunotherapy, and proposes a simple physical examination technique to ensure consistent tumor depth when conducting implantable tumor immunotherapy experiments.

Cost-Effectiveness Analysis of Switching from Trivalent to Quadrivalent Seasonal Influenza Vaccine in Argentina

The burden of seasonal influenza disease in Argentina is considerable. The cost-effectiveness of trivalent (TIV) versus quadrivalent influenza vaccine (QIV) in Argentina was assessed. An age-stratified, static, decision-tree model compared the costs and benefits of vaccination for an average influenza season. Main outcomes included: numbers of influenza cases; general practitioner (GP) visits; complicated ambulatory cases; hospitalizations; deaths averted; and costs per quality-adjusted life years (QALYs) gained. Epidemiological data from Argentina for 2014–2019 were used to determine the proportion of A and B strain cases, and the frequency of mismatch between vaccine and circulating B strains. To manage uncertainty, one-way and probabilistic sensitivity analyses were performed. Switching from TIV to QIV would prevent 19,128 influenza cases, 16,164 GP visits, 2440 complicated ambulatory cases, 524 hospitalizations, and 82 deaths. Incremental cost–effectiveness ratios (ICERs) per QALY were 13,590 and 11,678 USD from the payer’s and societal perspectives, respectively. The greatest health benefits and direct medical cost savings would occur in ≥ 65-year-olds. One-way sensitivity analyses demonstrated the principal drivers of ICER to be vaccine acquisition costs, environmental B strain predominance, and B strain mismatch. Introducing QIV in Argentina would be beneficial and cost-effective relative to TIV, particularly in older adults.