The Challenge of Parasite Control
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2015
Several newer vaccine types have been developed, some of which are acellular vaccines in that they do not include whole organisms. An example is the subunit vaccine, in which the vaccine consists of particular immunostimulatory antigens only. The hepatitis B vaccine, for instance, is composed only of viral surface proteins. Our understanding of the stimulatory role of T cells in a humoral response has resulted in the development of conjugate vaccines (Figure 9.23A). These vaccines rely on a combination of antigens that stimulate both B and T cells. The Haemophilus influenzae vaccine, for instance, combines polysaccharides found in the bacterial capsule with pep-tides recognized by antigen-specific T cells. The result is a much stronger antibody response then could be elicited with the polysaccharides alone.
The Challenge of Parasite Control
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2023
Several newer vaccine types have been developed, some of which are acellular vaccines in that they do not include whole organisms. An example is the subunit vaccine, in which the vaccine consists of particular immunostimulatory antigens only. The hepatitis B vaccine, for instance, is composed only of viral surface proteins. Our understanding of the stimulatory role of T cells in a humoral response has resulted in the development of conjugate vaccines (Figure 9.28). These vaccines rely on a combination of antigens that stimulate both B and T cells. The Haemophilus influenzae vaccine, for instance, combines polysaccharides found in the bacterial capsule with peptides recognized by antigen-specific T cells. The result is a much stronger antibody response then could be elicited with the polysaccharides alone. And most recently, used clinically only since late 2020, are the mRNA vaccines used against the SARS-CoV-2 virus that causes Covid-19. These vaccines consist of viral mRNA that encodes an antigenic viral peptide. The RNA is surrounded by a lipid-based vesicle, which fuses with host cells, allowing the RNA to enter these cells. The viral mRNA is subsequently translated by host translation machinery and the resulting viral peptide is released from the cell where it stimulates an immune response. See the web callout associated with this section to learn about other vaccine types, including those based on nucleic acid.
Bacille Calmette–Guerin and Prospects for New Vaccines against Tuberculosis
Peter D O Davies, Stephen B Gordon, Geraint Davies in Clinical Tuberculosis, 2014
An alternative approach to replacing BCG is to leave BCG as it is, administered at birth throughout most of the world, and develop a booster vaccine to be given at a later point in time. Such a vaccine could be given in infancy (soon after BCG vaccination), in adolescence (before the rise in incidence that occurs in adolescence/young adults) or to HIV-infected adults, ideally at HIV diagnosis and before they become immunosuppressed. The field of BCG booster vaccines is more advanced than BCG replacements, and there are currently several BCG booster vaccine candidates being evaluated in the clinic [59]. This approach requires the selection of antigen(s) within M. tuberculosis for inclusion in a subunit vaccine and also requires a choice of antigen delivery system. To boost an immune response induced by BCG, the antigens selected need to be expressed by BCG. Within the field of BCG booster vaccines there are two main approaches. The first is to develop a protein subunit vaccine that is administered with an adjuvant. The second is to develop a recombinant viral vector expressing the antigen(s) of choice where the viral vector acts as the adjuvant to stimulate the cellular immune response. The leading candidates in each of these categories are described in more detail here.
Preclinical developments in the delivery of protein antigens for vaccination
Published in Expert Opinion on Drug Delivery, 2023
Dylan A. Hendy, Alex Haven, Eric M. Bachelder, Kristy M. Ainslie
Vaccination aims to mirror this process while not infecting a person with a potentially dangerous pathogen (Figure 1). With attenuated pathogen vaccines, this problem presents a delicate balance between delivering a vaccine that could cause disease with one potent enough to drive a protective immune response. Utilizing purified antigens from a pathogen (e.g. proteins and sugars) for vaccination (a subunit vaccine) is one method to ensure infection will not occur while simultaneously ensuring a response against a protective antigen is generated. While the use of subunit antigens is safer than attenuated pathogen vaccines, they often need to be delivered with immune stimulating molecules to activate the immune system as would happen in a natural infection and provide a balanced Th1/Th2 response [5]. Furthermore, these vaccines can be improved by delivery strategies that can protect the antigen from degradation, provide targeting to immune cells, reduce adjuvant toxicity, and present antigen to immune cells in a way that mimics natural infection.
Exploring Klebsiella pneumoniae capsule polysaccharide proteins to design multiepitope subunit vaccine to fight against pneumonia
Published in Expert Review of Vaccines, 2022
Jyotirmayee Dey, Soumya Ranjan Mahapatra, S Lata, Shubhransu Patro, Namrata Misra, Mrutyunjay Suar
Klebsiella pneumoniae has emerged as an urgent public health threat in many industrialized countries worldwide. Infections caused by K. pneumoniae are difficult to treat because these organisms are typically resistant to multiple drugs, and the patients have significant co-morbidities. Given the dearth of new antibiotics and the recent incidence of multidrug-resistant strains, there is a critical need for the development of a vaccine against K. pneumoniae infections [20]. The capsule polysaccharide (CPS) of K. pneumoniae has long been viewed as an important virulence factor that promotes resistance to phagocytosis and serum bactericidal activity. Experimental studies have demonstrated that anti-CPS IgG isolated from human volunteers protects mice against K. pneumoniae sepsis [65]. In present times, the multi-epitope subunit vaccine is preferable than the traditional vaccine for several advantages including safety, higher stability, less allergic, autoimmune responses, and a more convenient production process. High throughput next-generation sequencing and advanced genomics and proteomics technologies have brought about a significant change in the computational immunology approach. With the abundance of genomic data and a plethora of immunoinformatics tools available, a better understanding of the immune response of the human body against a multitude of infectious pathogens can be deciphered [66].
Combined adjuvant-delivery system for new generation vaccine antigens: alliance has its own advantage
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2018
Monika Kaurav, Jitender Madan, M. S. Sudheesh, Ravi Shankar Pandey
There are certain limitations associated with the subunit vaccine approach; the first limitation is the incapability of protein synthesized by cell culture techniques to form a three-dimensional structure that happens occurs in the host, and may not elicit protective antibodies. Second, subunit vaccines typically induce deprived antibody responses than other vaccines due to the lack of innate defensive prompts that initiate natural immune system. Furthermore, alum is the solely adjuvant utilized in the majority of the marketed vaccine induces only T-helper lymphocytes (Th2) immune response with minimal/no cellular immunity. Thus, it is a poor adjuvant for intracellular chronic infections vaccine, where active and persistent cellular immune response mediated by T-cell is necessary [4].
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