COVID-19 vaccines and a perspective on Africa.

Vaccines have dramatically changed the COVID-19 pandemic. Over 30 vaccines that were developed on four main platforms are currently being used globally, but a deep dissection of the immunological mechanisms by which they operate is limited to only a few of them. Here, we review the evidence describing specific aspects of the modes of action of COVID-19 vaccines; these include innate immunity, trained innate immunity, and mucosal responses. We also discuss the use of COVID-19 vaccines in the African continent which is ridden with inequality in its access to vaccines and vaccine-related immunological research. We argue that strengthening immunology research in Africa should inform on fundamental aspects of vaccination, including the relevance of genetics, trained innate immunity, and microbiome diversity.

A multiscale model of virus pandemic: Heterogeneous interactive entities in a globally connected world.

This paper is devoted to the multidisciplinary modelling of a pandemic initiated by an aggressive virus, specifically the so-called SARS-CoV-2 Severe Acute Respiratory Syndrome, corona virus n.2. The study is developed within a multiscale framework accounting for the interaction of different spatial scales, from the small scale of the virus itself and cells, to the large scale of individuals and further up to the collective behaviour of populations. An interdisciplinary vision is developed thanks to the contributions of epidemiologists, immunologists and economists as well as those of mathematical modellers. The first part of the contents is devoted to understanding the complex features of the system and to the design of a modelling rationale. The modelling approach is treated in the second part of the paper by showing both how the virus propagates into infected individuals, successfully and not successfully recovered, and also the spatial patterns, which are subsequently studied by kinetic and lattice models. The third part reports the contribution of research in the fields of virology, epidemiology, immune competition, and economy focussed also on social behaviours. Finally, a critical analysis is proposed looking ahead to research perspectives.

Multiple roles of perforin in hampering ERBB-2 (Her-2/neu) carcinogenesis in transgenic male mice.

Perforin (pfp)-mediated cytotoxicity is one of the principal immunosurveillance mechanisms involved in the fight against cancer. However, its importance in spontaneous epithelial cancer is still poorly defined. In this study, we use a realistic mouse model that displays many features that are equivalent to human pathology to evaluate the role of pfp-dependent immunosurveillance by comparing tumor progression in rat ERBB-2 (neu) transgenic, pfp-proficient (neu(+)/pfp(+)) or pfp-deficient (neu(+)/pfp(-)) BALB/c male mice. Adult neu(+)/pfp(+) males developed poorly differentiated salivary carcinomas, whereas neu(+)/pfp(-) males displayed their salivary carcinomas noticeably earlier and showed zones of more highly differentiated tumor, indicating that pfp-mediated immunosurveillance is able not only to delay the growth kinetic of an aggressive epithelial tumor, but also to shape its histology. The role of pfp-mediated immunosurveillance appeared to be of even more dramatic importance against the less aggressive male mammary carcinomas. In neu(+)/pfp(+) males, the incidence of mammary carcinomas was a sporadic and late event. In contrast, in neu(+)/pfp(-) males their incidence was four-fold higher. This higher cancer incidence was associated with a 2-fold higher occurrence of persisting mammary remnants, a major risk factor for mammary cancer in male mice, and one that would appear to be due to pfp's previously unidentified involvement in male mammary gland rejection during embryogenesis. This work thus provides further proof of the complex role that the immune system plays in the body and gives new insight into the pathogenesis of epithelial tumors, demonstrating that the penetrance and malignancy of a tumor may be dramatically affected by pfp-dependent mechanisms.

Systemic spread is an early step in breast cancer.

It is widely accepted that metastasis is a late event in cancer progression. Here, however, we show that tumor cells can disseminate systemically from earliest epithelial alterations in HER-2 and PyMT transgenic mice and from ductal carcinoma in situ in women. Wild-type mice transplanted with single premalignant HER-2 transgenic glands displayed disseminated tumor cells and micrometastasis in bone marrow and lungs. The number of disseminated cancer cells and their karyotypic abnormalities were similar for small and large tumors in patients and mouse models. When activated by bone marrow transplantation into wild-type recipients, 80 early-disseminated cancer cells sufficed to induce lethal carcinosis. Therefore, release from dormancy of early-disseminated cancer cells may frequently account for metachronous metastasis.

Are oncoantigens suitable targets for anti-tumour therapy?

When a vaccine-elicited immune response is directed against oncoantigens--proteins required for the neoplastic process--the chance that the tumour will evade the vaccine should be reduced. But how can these causal oncoantigens be identified? One approach is to find tumour-associated and microenvironment-associated oncoantigens required for progression from one tumour stage to the next by comparing gene signatures isolated from the different stages of tumour progression in cancer-prone transgenic mice. Mouse oncoantigens subsequently shown to be involved in human cancer can then be validated in mouse vaccination experiments. This provides the groundwork for the rational design of cancer vaccines for clinical trials.

Recombinant human lactoferrin induces human and mouse dendritic cell maturation via Toll-like receptors 2 and 4.

Lactoferrin, a key component of innate immunity, is a cationic monomeric 80-kDa glycoprotein of the transferrin superfamily. Recombinant human lactoferrin, known as talactoferrin (TLF), induces a distinct functional maturation program in human dendritic cells (DCs) derived from peripheral blood monocytes. However, the receptors and molecular mechanisms involved in this induction have not been fully determined. By exploiting genome-wide transcription profiling of immature DCs, TNF-α- and IL-1ß-matured DCs (m-DCs), and TLF-matured DCs (TLF-DCs), we have detected a set of transcripts specific for m-DCs and one specific for TLF-DCs. Functional network reconstruction highlighted, as expected, the association of m-DC maturation with IL-1ß, TNF-α, and NF-κB, whereas TLF-DC maturation was associated with ERK and NF-κB. This involvement of ERK and NF-κB transduction factors suggests direct involvement of Toll-like receptors (TLRs) in TLF-induced maturation. We have used MyD88 inhibition and siRNA silencing TLRs on human DCs and mouse TLR-2-knockout cells, to show that TLF triggers the maturation of both human and mouse DCs through TLR-2 and TLR-4.

Vaccines for tumour prevention.

Despite tremendous progress in basic and epidemiological research, effective prevention of most types of cancer is still lacking. Vaccine use in cancer therapy remains a promising but difficult prospect. However, new mouse models that recapitulate significant features of human cancer progression show that vaccines can keep precancerous lesions under control and might eventually be the spearhead of effective and reliable ways to prevent cancer.

Attenuation of PI3K/Akt-mediated tumorigenic signals through PTEN activation by DNA vaccine-induced anti-ErbB2 antibodies.

By studying BALB/c mice deficient in immune components, we show that the protective immunity to rat ErbB2(+) tumors rests on the Ab response elicited by the electroporation of a DNA vaccine encoding the extracellular and transmembrane domains of rat ErbB2. In vivo, the adoptive transfer of vaccine-elicited anti-rat ErbB2 Abs protected against a challenge of rat ErbB2(+) carcinoma cells (TUBO cells). In vitro, such Abs inhibited TUBO cell growth by impairing cell cycle progression and inducing apoptosis. To correlate intrinsic mechanisms of Ab action with their tumor-inhibitory potential, first we showed that TUBO cells constitutively express phosphorylated transgenic ErbB2/autochthonous ErbB3 heterodimers and exhibit a basal level of Akt phosphorylation, suggesting a constitutive activation of the PI3K/Akt pathway. Treatment with anti-ErbB2 Abs caused a drastic reduction in the basal level of Akt phosphorylation in the absence of an impairment of PI3K enzymatic activity. Notably, the same Ab treatment induced an increase in PTEN phosphatase activity that correlated with a reduced PTEN phosphorylation. In conclusion, vaccine-induced anti-ErbB2 Abs directly affected the transformed phenotype of rat ErbB2(+) tumors by impairing ErbB2-mediated PI3K/Akt signaling.

Erbb2 DNA vaccine combined with regulatory T cell deletion enhances antibody response and reveals latent low-avidity T cells: potential and limits of its therapeutic efficacy.

Rat (r)Erbb2 transgenic BALB-neuT mice genetically predestined to develop multiple invasive carcinomas allow an assessment of the potential of a vaccine against the stages of cancer progression. Because of rErbb2 expression in the thymus and its overexpression in the mammary gland, CD8(+) T cell clones reacting at high avidity with dominant rErbb2 epitopes are deleted in these mice. In BALB-neuT mice with diffuse and invasive in situ lesions and almost palpable carcinomas, a temporary regulatory T cells depletion combined with anti-rErbb2 vaccine markedly enhanced the anti-rErbb2 Ab response and allowed the expansion of latent pools of low-avidity CD8(+) T cells bearing TCRs repertoire reacting with the rErbb2 dominant peptide. This combination of a higher Ab response and activation of a low-avidity cytotoxic response persistently blocked tumor progression at stages in which the vaccine alone was ineffective. However, when diffuse and invasive microscopic cancers become almost palpable, this combination was no longer able to secure a significant extension of mice survival.

Role of ADCC, CDC, and CDCC in Vaccine-Mediated Protection against Her2 Mammary Carcinogenesis.

Amplification or mutation of the Her2 oncoantigen in human mammary glands leads to the development of an aggressive breast carcinoma. Several features of this breast carcinoma are reproduced in mammary carcinomas that spontaneously arise in female transgenic mice bearing the activated rat Her2 oncogene under transcriptional control of the mouse mammary tumor virus promoter-BALB-neuT (neuT) mice. We previously demonstrated that carcinoma progression in neuT mice can be prevented by DNA vaccination with RHuT, a plasmid coding for a chimeric rat/human Her2 protein. RHuT vaccination exerts an antitumor effect, mostly mediated by the induction of a strong anti-rat Her2 antibody response. IgG induced by RHuT vaccine mainly acts by blocking Her2 signaling, thus impairing cell cycle progression and inducing apoptosis of cancer cells, but other indirect effector mechanisms could be involved in the antibody-mediated protection. The recruitment of cells with perforin-dependent cytotoxic activity, able to perform antibody-dependent cellular cytotoxicity, has already been investigated. Less is known about the role of the complement system in sustaining antitumor response through complement-dependent cytotoxicity and cellular cytotoxicity in vaccinated mice. This work highlights that the weight of such mechanisms in RHuT-induced cancer protection is different in transplantable versus autochthonous Her2+ tumor models. These results may shed new light on the effector mechanisms involved in antibody-dependent anti-cancer responses, which might be exploited to ameliorate the therapy of Her2+ breast cancer.

2011: the immune hallmarks of cancer.

Ten years after the publication of the position paper "The hallmarks of cancer" (Hanahan and Weinberg Cell 100:57-70, 2000), it has become increasingly clear that mutated cells on their way to giving rise to a tumor have also to learn how to thrive in a chronically inflamed microenvironment, evade immune recognition, and suppress immune reactivity. Genetic and molecular definition of these three immune hallmarks of cancer offers the opportunity to learn how to deploy specific countermeasures to reverse the situation in favor of the immune system and, eventually, the patient. This new information could be channeled to address what seem to be the three major hallmarks for the immune control of cancer progression: effective procedures to activate immune reactivity; characterization of not-disposable oncoantigens; and counteraction of immune suppression.

p130Cas is an essential transducer element in ErbB2 transformation.

The ErbB2 oncogene is often overexpressed in breast tumors and associated with poor clinical outcome. p130Cas represents a nodal scaffold protein regulating cell survival, migration, and proliferation in normal and pathological cells. The functional role of p130Cas in ErbB2-dependent breast tumorigenesis was assessed by its silencing in breast cancer cells derived from mouse mammary tumors overexpressing ErbB2 (N202-1A cells), and by its reexpression in ErbB2-transformed p130Cas-null mouse embryonic fibroblasts. We demonstrate that p130Cas is necessary for ErbB2-dependent foci formation, anchorage-independent growth, and in vivo growth of orthotopic N202-1A tumors. Moreover, intranipple injection of p130Cas-stabilized siRNAs in the mammary gland of Balbc-NeuT mice decreases the growth of spontaneous tumors. In ErbB2-transformed cells, p130Cas is a crucial component of a functional molecular complex consisting of ErbB2, c-Src, and Fak. In human mammary cells, MCF10A.B2, the concomitant activation of ErbB2, and p130Cas overexpression sustain and strengthen signaling, leading to Rac1 activation and MMP9 secretion, thus providing invasive properties. Consistently, p130Cas drives N202-1A cell in vivo lung metastases colonization. These results demonstrate that p130Cas is an essential transducer in ErbB2 transformation and highlight its potential use as a novel therapeutic target in ErbB2 positive human breast cancers.

Planning a Bayesian early-phase phase I/II study for human vaccines in HER2 carcinomas.

Recent innovative statistical approaches for phase I/II clinical trials allow one to jointly model the toxicity and efficacy of a new treatment, taking into account the information gathered during the trial. Prior probabilities are then updated with interim data and thus predictive probabilities become more accurate as the trial progresses. In this study, prior distribution elicited from a physician's opinion on the available dose levels planned for a vaccination dose-finding trial, with human DNA in patients with HER2-positive tumours in terms of toxicity and therapeutic response is presented and discussed. A simulation study was conducted in order to quantify the impact of the choice of prior on study results, i.e. the recommended dose level at the end of the trial.

COVID-19 vaccines: where we stand and challenges ahead.

In the eleven months elapsed since the identification of the SARS-CoV-2 virus and its genome, an exceptional effort by the scientific community has led to the development of over 300 vaccine projects. Over 40 are now undergoing clinical evaluation, ten of these are in Phase III clinical trials, three of them have ended Phase III with positive results. A few of these new vaccines are being approved for emergency use. Existing data suggest that new vaccine candidates may be instrumental in protecting individuals and reducing the spread of pandemic. The conceptual and technological platforms exploited are diverse, and it is likely that different vaccines will show to be better suited to distinct groups of the human population. Moreover, it remains to be elucidated whether and to what extent the capacity of vaccines under evaluation and of unrelated vaccines such as BCG can increase immunological fitness by training innate immunity to SARS-CoV-2 and pathogen-agnostic protection. Due to the short development time and the novelty of the technologies adopted, these vaccines will be deployed with several unresolved issues that only the passage of time will permit to clarify. Technical problems connected with the production of billions of doses and ethical ones connected with the availably of these vaccines also in the poorest countries, are imminent challenges facing us. It is our tenet that in the long run more than one vaccine will be needed to ensure equitable global access, protection of diverse subjects and immunity against viral variants.

Zoledronic acid repolarizes tumour-associated macrophages and inhibits mammary carcinogenesis by targeting the mevalonate pathway.

It is unknown whether zoledronic acid (ZA) at clinically relevant doses is active against tumours not located in bone. Mice transgenic for the activated ErbB-2 oncogene were treated with a cumulative number of doses equivalent to that recommended in human beings. A significant increase in tumour-free and overall survival was observed in mice treated with ZA. At clinically compatible concentrations, ZA modulated the mevalonate pathway and affected protein prenylation in both tumour cells and macrophages. A marked reduction in the number of tumour-associated macrophages was paralleled by a significant decrease in tumour vascularization. The local production of vascular endothelial growth factor and interleukin-10 was drastically down-regulated in favour of interferon-γ production. Peritoneal macrophages and tumour-associated macrophages of ZA-treated mice recovered a full M1 antitumoral phenotype, as shown by nuclear translocation of nuclear factor kB, inducible nitric oxide synthase expression and nitric oxide production. These data indicate that clinically achievable doses of ZA inhibit spontaneous mammary cancerogenesis by targeting the local microenvironment, as shown by a decreased tumour vascularization, a reduced number of tumour-associated macrophages and their reverted polarization from M2 to M1 phenotype.

Local delivery of recombinant vaccinia virus encoding for neu counteracts growth of mammary tumors more efficiently than systemic delivery in neu transgenic mice.

Recombinant vaccinia virus has been widely employed as a cancer vaccine in several clinical trials. In this study we explored, employing BALB/c mice transgenic for the rat neu oncogene, the ability of the recombinant vaccinia virus neu (rV-neuT) vaccine to inhibit growth of neu+ mammary carcinomas and whether the efficacy of vaccination was dependent on: (a) carcinogenesis stage at which the vaccination was initiated; (b) number of vaccinations and (c) route of delivery (systemic vs. local). BALB-neuT mice were vaccinated one, two and three times by subcutaneous (s.c.) and intramammary gland (im.g.) injection with rV-neuT or V-wt (wild-type vaccinia virus) starting at the stage in which mouse mammary gland displays atypical hyperplasia, carcinoma in situ or invasive carcinoma. We demonstrated that vaccination using rV-neuT was more effective when started at an earlier stage of mammary carcinogenesis and after three vaccinations. The im.g. vaccination was more effective than the s.c. vaccination in inhibiting mammary carcinogenesis, eliciting anti-Neu antibodies, increasing anti-Neu IgG2a/G3 isotypes and inducing antibodies able to trigger mammary tumor cells apoptosis and antibody-dependent cellular cytotoxicity. The better protective ability of rV-neuT im.g. vaccination was associated with its capacity to induce a superior degree of in vivo mammary cancer cells apoptosis. Our research suggests that intratumoral vaccination using recombinant vaccinia virus could be employed to increase the activity of a genetic cancer vaccine. This study may have important implications for the design of cancer vaccine protocols for the treatment of breast cancer and of accessible tumors using recombinant vaccinia virus.

Stat3 is required for anchorage-independent growth and metastasis but not for mammary tumor development downstream of the ErbB-2 oncogene.

The oncogenic transcription factor Stat3 is constitutively active in a high percentage of human tumors including mammary adenocarcinomas and is reported to participate in the ErbB-2 oncogene signaling. In order to assess the role of signal transducer and activator of transcription 3 (Stat3) in mammary tumorigenesis downstream of ErbB-2, we generated mice expressing the activated rat ErbB-2 (neu) but lacking Stat3 in the mammary epithelium. Stat3 is apparently not required for neu-driven mammary tumorigenesis as tumors developed similarly in both Stat3-sufficient and Stat3-deficient glands. However, short hairpin RNA (shRNA)-mediated Stat3 silencing in a neu-overexpressing tumor-derived cell line completely abolished both neu-driven anchorage-independent growth and lung metastasis. Our data suggest that Stat3 might be a useful therapeutic target in breast tumors showing amplification and/or overexpression of the ErbB-2 oncogene, which normally display aggressive, metastatic behavior.

Biological fluid dynamics of airborne COVID-19 infection.

ABSTRACT: We review the state of knowledge on the bio-fluid dynamic mechanisms involved in the transmission of the infection from SARS-CoV-2. The relevance of the subject stems from the key role of airborne virus transmission by viral particles released by an infected person via coughing, sneezing, speaking or simply breathing. Speech droplets generated by asymptomatic disease carriers are also considered for their viral load and potential for infection. Proper understanding of the mechanics of the complex processes whereby the two-phase flow emitted by an infected individual disperses into the environment would allow us to infer from first principles the practical rules to be imposed on social distancing and on the use of facial and eye protection, which to date have been adopted on a rather empirical basis. These measures need compelling scientific validation. A deeper understanding of the relevant biological fluid dynamics would also allow us to evaluate the contrasting effects of natural or forced ventilation of environments on the transmission of contagion: the risk decreases as the viral load is diluted by mixing effects but contagion is potentially allowed to reach larger distances from the infected source. To that end, our survey supports the view that a formal assessment of a number of open problems is needed. They are outlined in the discussion.

Murine pneumotropic virus chimeric Her2/neu virus-like particles as prophylactic and therapeutic vaccines against Her2/neu expressing tumors.

Virus-like particles (VLPs) have increasingly attracted attention as DNA-free and safe antigen carriers in tumor immunotherapy, requiring only minute amounts of antigens. Previously, we have immunized with murine polyomavirus (MPyV) VLPs carrying human Her2/neu and prevented the outgrowth of a human Her2/neu expressing tumor in a transplantable tumor model as well as outgrowth of spontaneous rat Her2/neu carcinomas in BALB-neuT mice. Here, we examine if prophylactic and therapeutic protection could be obtained with murine pneumotropic virus (MPtV) VLPs, and study the cross-reactivity between human and rat Her2/neu. VLPs from MPyV and MPtV carrying human or rat Her2/neu were tested in two transplantable tumor models against a human Her2/neu positive (D2F2/E2) and a rat Her2/neu positive tumor cell line (TUBO). Rat Her2/neu-VLPs were also tested in BALB-neuT mice. Her2/neu-MPtVLPs were as efficient as prophylactic vaccines against D2F2/E2 and TUBO as those from MPyV. Homologous Her2/neu was better than heterologous, i.e. human Her2/neu-VLPs were better than rat Her2/neu-VLPs against D2F2/E2 and vice versa. Moreover, therapeutic immunization with human Her2/neu-VLPs together with CpG given up to 6 days after challenge protected against D2F2/E2. In BALB-neuT mice, rat Her2/neu-VLPs were less efficient than human Her2/neu-VLPs used in our previous study, implying that protection seen in that study was partly due to the use of human rather than rat Her2/neu. In conclusion, Her2/neu-MPtVLPs are effective both as prophylactic and therapeutic tumor vaccines. Homologous Her2/neu-VLPs are superior to heterologous in transplantable tumor models, while the opposite is true in BALB-neuT mice.

Lactoferrin, a major defense protein of innate immunity, is a novel maturation factor for human dendritic cells.

Lactoferrin (LF) is an important protein component of the innate immune system that is broadly distributed within the body fluids. LF is endowed with multiple biological activities. Talactoferrin (TLF), a recombinant human LF, is in clinical development as an anticancer agent and is entering Phase III clinical trials. Here, we show that TLF induces the maturation of human dendritic cells (DCs) derived from monocytes. TLF, at physiologically relevant concentrations (100 microg/ml) up-regulates the expression of human leukocyte antigen (HLA) class II, CD83, CD80, and CD86 costimulatory molecule and CXCR4 and CCR7 chemokine receptors, acting primarily through the p38 MAPK signaling pathway. DCs matured by TLF displayed an enhanced release of IL-8 and CXCL10, as well as a significantly reduced production of IL-6, IL-10, and CCL20. They also display a reduced ability to take up antigen and increased capacity to trigger proliferation and release IFN-gamma in the presence of allogeneic human T cells. TLF-matured DCs are able to prime naive T cells to respond to KLH antigen and display a significantly increased capacity to present Flu-MA(58-66) peptide to HLA-A2-matched T cells. These data suggest that a key immunomodulatory function that may be mediated by TLF is to link the innate with adaptive immunity through DC maturation.