The potential of DNA vaccination against tumor-associated antigens for antitumor therapy

Conventional treatment approaches for malignant tumors are highly invasive and sometimes have only a palliative effect. Therefore, there is an increasing demand to develop novel, more efficient treatment options. Increased efforts have been made to apply immunomodulatory strategies in antitumor treatment. In recent years, immunizations with naked plasmid DNA encoding tumor-associated antigens have revealed a number of advantages. By DNA vaccination, antigen-specific cellular as well as humoral immune responses can be generated. The induction of specific immune responses directed against antigens expressed in tumor cells and displayed e.g., by MHC class I complexes can inhibit tumor growth and lead to tumor rejection. The improvement of vaccine efficacy has become a critical goal in the development of DNA vaccination as antitumor therapy. The use of different DNA delivery techniques and coadministration of adjuvants including cytokine genes may influence the pattern of specific immune responses induced. This brief review describes recent developments to optimize DNA vaccination against tumor-associated antigens. The prerequisite for a successful antitumor vaccination is breaking tolerance to tumor-associated antigens, which represent "self-antigens." Currently, immunization with xenogeneic DNA to induce immune responses against self-molecules is under intensive investigation. Tumor cells can develop immune escape mechanisms by generation of antigen loss variants, therefore, it may be necessary that DNA vaccines contain more than one tumor antigen. Polyimmunization with a mixture of tumor-associated antigen genes may have a synergistic effect in tumor treatment. The identification of tumor antigens that may serve as targets for DNA immunization has proceeded rapidly. Preclinical studies in animal models are promising that DNA immunization is a potent strategy for mediating antitumor effects in vivo. Thus, DNA vaccines may offer a novel treatment for tumor patients. DNA vaccines may also be useful in the prevention of tumors with genetic predisposition. By DNA vaccination preventing infections, the development of viral-induced tumors may be avoided.     

Immunological, cellular and molecular events in typhoid fever

Salmonella, a facultative intracellular Gram-negative bacterium infects a wide range of hosts causing several gastrointestinal diseases and enteric fever in humans and certain animal species. Typhoid caused by Salmonella typhi remains a major health concern in India and worldwide. Also, with emergence of multidrug resistant strains, Salmonella has acquired increased virulence, communicability and survivability, resulting in increased morbidity and mortality. Though a number of vaccines for typhoid are available against S. typhi (or also against S. typhimurium), these have certain undesirable side effects and the search for new immunogens suitable for vaccine formulation is still continuing. The immune response to primary Salmonella infection involves both humoral and cell-mediated responses. The protective immunity against Salmonella depends on host- parasite interaction, however; the detailed mechanism of virulence, innate resistance and susceptibility of host remains unclear. This review focuses on the molecular, immunological and cellular mechanisms of pathogenesis of Salmonella infection to provide an insight to counteract bacterial infections and allow a better understanding of its clinical manifestations. It also reviews better technological possibilities combined with increased knowledge in related fields such as immunology and molecular biology and allow for new vaccination strategies. Some new approaches such as subunit and nucleic acid vaccines and recombinant antigen which are becoming increasingly important for the development of potential vaccines have also been discussed. A significant progress has been made in our understanding of Salmonella pathogenesis. Despite these efforts, however, many challenges exist, especially for investigators who aim to understand how the pathogenic mechanisms operating in vitro apply to in vivo model systems. However, unyielding work and collaborations between Salmonella researchers and clinicians worldwide have made significant contributions to understanding the interaction between virulence determinants and immunity required to stop the spread of this pathogen.     

Augmentation of innate host defenses against opportunistic fungal pathogens

Development of invasive fungal infection is the result of the complex interaction between fungal and host factors. The outcome of infection, once it has developed, depends upon appropriate use of antifungal therapy, surgical debridement as indicated, and improvement of host defenses. Thus, there have been major efforts for development of new strategies for immunomodulation and augmentation of host defenses in prevention and treatment of invasive mycoses. These modalities include granulocyte and granulocyte-macrophage colony-stimulating factors, interferon-γ, granulocyte transfusions, immunotherapy with infusion of dendritic cells and T cells, anti-heat shock protein 90 monoclonal antibodies, long pentraxin 3, mannose-binding lectin, and deferasirox. Although major strides in our understanding of augmentation of host response to invasive fungal infections are opening up novel avenues of therapy to harness patients’ innate immune systems against these frequently lethal pathogens, well-designed clinical trials are needed to demonstrate safety and efficacy of these new approaches.     

Fungal Vaccines and Immunotherapeutics: Current Concepts and Future Challenges

Purpose of review

The remarkable advances in modern medicine have paradoxically resulted in a rapidly expanding population of immunocompromised patients displaying extreme susceptibility to life-threatening fungal infections. There are currently no licensed vaccines, and the prophylaxis and therapy of fungal infections in at-risk individuals remains challenging, contributing to undesirable mortality and morbidity rates. The design of successful antifungal preventive approaches has been hampered by an insufficient understanding of the dynamics of the host-fungus interaction and the mechanisms that underlie heterogenous immune responses to vaccines and immunotherapy.

Recent findings

Recent advances in proteomics and glycomics have contributed to the identification of candidate antigens for use in subunit vaccines, novel adjuvants, and delivery systems to boost the efficacy of protective vaccination responses that are becoming available, and several targets are being exploited in immunotherapeutic approaches.

Summary

We review some of the emerging concepts as well as the inherent challenges to the development of fungal vaccines and immunotherapies to protect at-risk individuals.

     

Recent Studies on Invasive Fungal Diseases in Children and Adolescents: an Update

The improved survival of fragile pediatric hosts such as those afflicted with primary or acquired immune deficiencies, prematurity, and surgical pathology – mainly gastrointestinal and trauma – has resulted in an increased number of children susceptible to invasive fungal infections. These infections are associated with significant morbidity and mortality. Newer, safer antifungal agents allow for preventive and empiric strategies in the management of patients at risk, such as premature infants, patients receiving chemotherapy, and bone marrow or solid-organ transplant recipients. Improved radiological and molecular techniques result in earlier diagnosis of fungal infections, allowing for preemptive therapy in these patients, minimizing exposure to antifungal agents and the risk of emergence of resistant fungal strains. A better understanding of the differences in pharmacokinetics between children and adults will allow for better utilization of existing antifungal agents and improved outcomes.     

DNA vaccination strategies for anti-tumour effective gene therapy protocols

After more than 15 years of experimentation, DNA vaccines have become a promising perspective for tumour diseases, and animal models are widely used to study the biological features of human cancer progression and to test the efficacy of vaccination protocols. In recent years, immunisation with naked plasmid DNA encoding tumour-associated antigens or tumour-specific antigens has revealed a number of advantages: antigen-specific DNA vaccination stimulates both cellular and humoral immune responses; multiple or multi-gene vectors encoding several antigens/determinants and immune-modulatory molecules can be delivered as single administration; DNA vaccination does not induce autoimmune disease in normal animals; DNA vaccines based on plasmid vectors can be produced and tested rapidly and economically. However, DNA vaccines have shown low immunogenicity when tested in human clinical trials, and compared with traditional vaccines, they induce weak immune responses. Therefore, the improvement of vaccine efficacy has become a critical goal in the development of effective DNA vaccination protocols for anti-tumour therapy. Several strategies are taken into account for improving the DNA vaccination efficacy, such as antigen optimisation, use of adjuvants and delivery systems like electroporation, co-expression of cytokines and co-stimulatory molecules in the same vector, different vaccination protocols. In this review we discuss how the combination of these approaches may contribute to the development of more effective DNA vaccination protocols for the therapy of lymphoma in a mouse model.     

COVID-19–associated mucormycosis: Evidence-based critical review of an emerging infection burden during the pandemic’s second wave in India

Coronavirus Disease 2019 (COVID-19), during the second wave in early 2021, has caused devastating chaos in India. As daily infection rates rise alarmingly, the number of severe cases has increased dramatically. The country has encountered health infrastructure inadequacy and excessive demand for hospital beds, drugs, vaccines, and oxygen. Adding more burden to such a challenging situation, mucormycosis, an invasive fungal infection, has seen a sudden surge in patients with COVID-19. The rhino-orbital-cerebral form is the most common type observed. In particular, approximately three-fourths of them had diabetes as predisposing comorbidity and received corticosteroids to treat COVID-19. Possible mechanisms may involve immune and inflammatory processes. Diabetes, when coupled with COVID-19–induced systemic immune change, tends to cause decreased immunity and an increased risk of secondary infections. Since comprehensive data on this fatal opportunistic infection are evolving against the backdrop of a major pandemic, prevention strategies primarily involve managing comorbid conditions in high-risk groups. The recommended treatment strategies primarily included surgical debridement and antifungal therapy using Amphotericin B and selected azoles. Several India-centric clinical guidelines have emerged to rightly diagnose the infection, characterise the clinical presentation, understand the pathogenesis involved, and track the disease course. Code Mucor is the most comprehensive one, which proposes a simple but reliable staging system for the rhino-orbital-cerebral form. A staging system has recently been proposed, and a dedicated registry has been started. In this critical review, we extensively analyse recent evidence and guidance on COVID-19–associated mucormycosis in India.     

Vaccinology in the era of high-throughput biology

Vaccination has been tremendously successful saving lives and preventing infections. However, the development of vaccines against global pandemics such as HIV, malaria and tuberculosis has been obstructed by several challenges. A major challenge is the lack of knowledge about the correlates and mechanisms of protective immunity. Recent advances in the application of systems biological approaches to analyse immune responses to vaccination in humans are beginning to yield new insights about mechanisms of vaccine immunity, and to define molecular signatures, induced rapidly after vaccination, that correlate with and predict vaccine induced immunity. Here, we review these advances and discuss the potential of this systems vaccinology approach in defining novel correlates of protection in clinical trials, and in infection-induced ‘experimental challenge models'' in humans.     

Antifungal drug resistance in molds: Clinical and microbiological factors

The incidence of fungal infections has increased over the past decade. In addition to classical pathogens, such as Aspergillus spp, new fungal species are increasingly reported. Despite the availability of new antifungals, mortality of invasive fungal infections remains very high. The host immune status is the main factor for survival. However, most of these pathogens have high minimum inhibitory concentrations (MICs) to antifungals, and therefore, the influence of these high MICs in the outcome of the patients have begun to be addressed. Several strains of Aspergillus fumigatus showing resistance to itraconazole have been isolated, and the molecular-resistance mechanisms have been characterized. In addition, attempts to correlate high MICs with patient outcome have been performed. Although correlation is far from perfect, a clear trend between high MICs and poor outcome has been established. Resistance of fungi to antifungals is a health problem requiring support from research agencies.     

Exploiting natural immunity to helminth parasites for the development of veterinary vaccines

The development of subunit vaccines against most parasitic helminth infections will require a better understanding of the different components of a natural rejection process including (1) recognition of parasite antigens; (2) induction of protective immune response phenotypes; and (3) activation of appropriate immune effector mechanisms. While novel technologies have allowed significant progress to be made in the identification of candidate vaccine antigens, the large scale production of these antigens and their presentation to the host with appropriate adjuvant systems remains a major problem in vaccine research. Identification of the molecular interactions involved in the innate immune response to helminth infections and the application of new genomic and proteomic technologies are likely to lead to major advances in these research fields. Gastrointestinal nematode parasites and liver fluke are the most important helminth parasites of production animals. In recent years, a lot of new knowledge has been gathered on the immunobiology of the host-parasite interactions in these two infection systems, which has allowed new vaccination strategies to be considered. Functional genomic technologies such as gene expression analysis by microarrays, promise to further advance our understanding of the molecular pathways leading to protection against parasite infections. This will not only have implications for vaccine research, but also provide novel targets for drug development and genetic selection.     

Antifungals discovery: an insight into new strategies to combat antifungal resistance

Undeniably, new antifungal treatments are necessary against pathogenic fungi. Fungal infections have significantly increased in recent decades, being highlighted as important causes of morbidity and mortality, particularly in immunocompromised patients. Five main antifungal classes are used: (i) azoles, (ii) echinocandins, (iii) polyenes, (iv) allylamines and (v) pyrimidine analogues. Moreover, the treatment of mycoses has several limitations, such as undesirable side effects, narrow activity spectrum, a small number of targets and fungal resistance, which are still of major concern in clinical practice. The discovery of new antifungals is mostly achieved by the screening of natural or synthetic/semisynthetic chemical compounds. The most recent discoveries in drug resistance mechanism and their avoidance were explored in a review, focusing on different antifungal targets, as well as new agents or strategies, such as combination therapy, that could improve antifungal therapy.

Significance and Impact of the Study

The failure to respond to antifungal therapy is complex and is associated with microbiological resistance and increased expression of virulence in fungal pathogens. Thus, this review offers an overview of current challenges in the treatment of fungal infections associated with increased antifungal drug resistance and the formation of biofilms in these opportunistic pathogens. Furthermore, the most recent and potential strategies to combat fungal pathogens are explored here, focusing on new agents as well as innovative approaches, such as combination therapy between antifungal drugs or with natural compounds.     

Synthesis and antifungal activity of functionalized 2,3-spirostane isomers

Invasive fungal infections are a major complication for individuals with compromised immune systems. One of the most significant challenges in the treatment of invasive fungal infections is the increased resistance of many organisms to widely used antifungals, making the development of novel antifungal agents essential. Many naturally occurring products have been found to be effective antimicrobial agents. In particular, saponins with spirostane glycosidic moieties—isolated from plant or marine species—have been shown to possess a range of antimicrobial properties. In this report, we outline a novel approach to the synthesis of a number of functionalized spirostane molecules that can be further used as building blocks for novel spirostane-linked glycosides and present results from the in vitro screenings of the antifungal potential of each derivative against four fungal species, including Candida albicans, Cryptococcus neoformans, Candida glabrata, and the filamentous fungus Aspergillus fumigatus.     

Immunity against Staphylococcus aureus cutaneous infections

Complications arising from cutaneous and soft tissue infections with Staphylococcus aureus are a major clinical problem owing to the high incidence of these infections and the widespread emergence of antibiotic-resistant bacterial strains. If prophylactic vaccines or immunotherapy for certain patient populations are to be developed as an alternative to antibiotics, it will be essential to better understand the immune mechanisms that provide protection against S. aureus skin infections. Recent discoveries have identified a key role for interleukin-1 (IL-1)- and IL-17-mediated immune responses in promoting neutrophil recruitment to the site of infection in the skin, a process that is required for host defence and bacterial clearance. This Review describes these new insights and discusses their potential impact on immune-based therapies and vaccination strategies.     

Opciones terapéuticas para el tratamiento antifúngico en el paciente crítico

Invasive fungal infections, especially in the critical care setting, have become an excellent target for prophylactic, empiric, and pre-emptive therapy interventions due to their associated high morbidity, mortality rate, increased incidence, and healthcare costs. For these reasons, new studies and laboratory tests have been developed over the last few years in order to formulate an early therapeutic intervention strategy in an attempt to reduce the high mortality rate associated with these infections. In recent years, evidencebased studies have shown the roles that the new antifungal drugs play in the treatment of invasive mycosis in seriously ill and complex patients, although data from critically ill patients are more limited. New antifungal agents have been analyzed in different clinical situations in critical care units, and the increasing number of non-Candida albicans species suggest that the application of early echinocandin therapy in critically ill patients with invasive candidiasis is a good option. Voriconazole should be recommended for invasive aspergillosis as a first line option.     

Mucosal immunity and vaccination

Abstract The gut mucosal immune system is a critical component of the body's defense against pathogenic organisms, especially those responsible for enteric infections associated with diarrhoeal disease. Attempts to vaccinate against infections of mucosal tissues have been less successful than vaccination against systematic infections, to a large extent reflecting a still incomplete knowledge about the most efficient means for inducing protective local immune responses at these sites. Secretory IgA (SIgA) is the predominating immunoglobulin along mucosal surfaces, and SIgA antibodies generated in gastrointestinal, respiratory or genito-urinary mucosal tissues can confer protection against infections affecting or originating in these sites. An efficacious intestinal SIgA immunity-inducing oral vaccine against cholera has been developed recently, and development of oral vaccines against other enteric infections such as those caused by enterotoxigenic Escherichia coli, Shigella and rotaviruses is in progress as well. Based on the concept of a common mucosal immune system through which activated lymphocytes from the gut can disseminate immunity to other mucosal and glandular tissues, there is currently also much interest in the possibility of developing oral vaccines against infections in the respiratory and urogenital tracts. However, the large and repeated antigen doses often required to achieve a protective immune response still makes this vaccination approach impractical for many purified antigens. There is, therefore, a great need to develop strategies for enhancing delivery of antigen to the mucosal immune system as well as to identify mucosa-active immunostimulating agents (adjuvants). These and other aspects of mucosal immunity in relation to immunization and vaccine development are discussed in this short review article.     

Mucosal immunity and vaccination.

The gut mucosal immune system is a critical component of the body's defense against pathogenic organisms, especially those responsible for enteric infections associated with diarrhoeal disease. Attempts to vaccinate against infections of mucosal tissues have been less successful than vaccination against systemic infections, to a large extent reflecting a still incomplete knowledge about the most efficient means for inducing protective local immune responses at these sites. Secretory IgA (SIgA) is the predominating immunoglobulin along mucosal surfaces, and SIgA antibodies generated in gastrointestinal, respiratory or genito-urinary mucosal tissues can confer protection against infections affecting or originating in these sites. An efficacious intestinal SIgA immunity-inducing oral vaccine against cholera has been developed recently, and development of oral vaccines against other enteric infections such as those caused by enterotoxigenic Escherichia coli, Shigella and rotaviruses is in progress as well. Based on the concept of a common mucosal immune system through which activated lymphocytes from the gut can disseminate immunity to other mucosal and glandular tissues, there is currently also much interest in the possibility of developing oral vaccines against infections in the respiratory and urogenital tracts. However, the large and repeated antigen doses often required to achieve a protective immune response still makes this vaccination approach impractical for many purified antigens. There is, therefore, a great need to develop strategies for enhancing delivery of antigen to the mucosal immune system as well as to identify mucosa-active immunostimulating agents (adjuvants). These and other aspects of mucosal immunity in relation to immunization and vaccine development are discussed in this short review article.     

Factors that may impact on immunosenescence: an appraisal

The increasing ratio of ageing population poses new challenges to healthcare systems. The elderly frequently suffer from severe infections. Vaccination could protect them against several infectious diseases, but it can be effective only if cells that are capable of responding are still present in the repertoire. Recent vaccination strategies in the elderly might achieve low effectiveness due to age-related immune impairment. Immunosenescence affects both the innate and adaptive immunity. Beside individual variations of genetic predisposition, epigenetic changes over the full course of human life exert immunomodulating effects. Disturbances in macrophage-derived cytokine release and reduction of the natural killer cell mediated cytotoxicity lead to increased frequency of infections. Ageing dampens the ability of B cells to produce antibodies against novel antigens. Exhausted memory B lymphocyte subsets replace naïve cells. Decline of cell-mediated immunity is the consequence of multiple changes, including thymic atrophy, reduced output of new T lymphocytes, accumulation of anergic memory cells, and deficiencies in cytokines production. Persistent viral and parasitic infections contribute to the loss of immunosurveillance and premature exhaustion of T cells. Reduced telomerase activity and Toll-like receptor expression can be improved by chemotherapy. Reversion of thymic atrophy could be achieved by thymus transplantation, depletion of accumulated dysfunctional naive T cells and herpesvirus-specific exhausted memory cells. Administration of interleukin (IL)-2, IL-7, IL-10, keratinocyte growth factor, thymic stromal lymphopoietin, as well as leptin and growth hormone boost thymopoiesis. In animals, several strategies have been explored to produce superior vaccines. Among them, virosomal vaccines containing polypeptide antigens or DNA plasmids as well as new adjuvanted vaccine formulations elicit higher dendritic cell activity and more effective serologic than conventional vaccines responses in the elderly. Hopefully, at least some of these approaches can be translated to human medicine in a not too far future.     

The role of immunostimulation in the treatment of invasive fungal infection

Invasive fungal infections (IFI) constitute a severe and increasing problem in an expanding patient population with immunodeficiency due to various reasons. Despite current management strategies, IFI remain a common and frequently devastating problem. New antifungals have been introduced in the medical armamentarium, but the results in patients’ survival are not yet optimal. The compromised host defense mechanisms of these patients contribute to the high failure rates. Immunoregulation includes strategies for restoration or augmentation of impaired immune responses that increase phagocytes’ number or enhance their function. Although there are extensive preclinical data, clinical investigations are very limited. Administration of certain beneficial cytokines, antibodies and other immune molecules, granulocyte transfusions, and stimulation of adaptive immunity through vaccination are potential, promising future preventive and therapeutic modalities and could be adjuncts to antifungal therapy for IFI. This review highlights and comments on preclinical and clinical studies published since 2005.     

Anti-HER2 vaccines: new prospects for breast cancer therapy

Each year, breast cancer accounts for more than 400,000 new cancer cases and more than 130,000 cancer deaths in Europe. Prognosis of nonmetastatic breast cancer patients is directly related to the extent of the disease, mainly nodal spreading and tumor size, and to the molecular profile, particularly HER2 over-expression. In patients with HER2-over-expressing tumors, different studies have shown cellular and/or humoral immune responses against HER2 associated with a lower tumor development at early stages of the disease. These findings have led to the hypothesis that the generation of an anti-HER2 immune response should protect patients from HER2-over-expressing tumor growth. Taken together with the clinical efficiency of trastuzumab-based anti-HER2 passive immunotherapy, these observations allowed to envisage various vaccine strategies against HER2. The induction of a stable and strong immunity by cancer vaccines is expected to lead to establishment of immune memory, thereby preventing tumor recurrence. However, an immunological tolerance against HER2 antigen exists representing a barrier to effective vaccination against this oncoprotein. As a consequence, the current challenge for vaccines is to find the best conditions to break this immunological tolerance. In this review, we will discuss the different anti-HER2 vaccine strategies currently developed; considering the strategies having reached the clinical phases as well as those still in preclinical development. The used antigen can be either composed of tumoral allogenic cells or autologous cells, or specific to HER2. It can be delivered by dendritic cells or in a DNA, peptidic or proteic form. Another area of research concerns the use of anti-idiotypic antibodies mimicking HER2.     

mRNA vaccines for COVID-19: what,why and how

The Coronavirus disease-19 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus -2 (SARS-CoV-2), has impacted human lives in the most profound ways with millions of infections and deaths. Scientists and pharmaceutical companies have been in race to produce vaccines against SARS-CoV-2. Vaccine generation usually demands years of developing and testing for efficacy and safety. However, it only took less than one year to generate two mRNA vaccines from their development to deployment. The rapid production time, cost-effectiveness, versatility in vaccine design, and clinically proven ability to induce cellular and humoral immune response have crowned mRNA vaccines with spotlights as most promising vaccine candidates in the fight against the pandemic. In this review, we discuss the general principles of mRNA vaccine design and working mechanisms of the vaccines, and provide an up-to-date summary of pre-clinical and clinical trials on seven anti-COVID-19 mRNA candidate vaccines, with the focus on the two mRNA vaccines already licensed for vaccination. In addition, we highlight the key strategies in designing mRNA vaccines to maximize the expression of immunogens and avoid intrinsic innate immune response. We also provide some perspective for future vaccine development against COVID-19 and other pathogens.