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The Black Death and Other Pandemics
Published in Scott M. Jackson, Skin Disease and the History of Dermatology, 2023
Scientists have supporting evidence—DNA studies of plague victims' teeth—that the Justinianic Plague was caused by the Yersinia pestis bacterium.20 This organism is transmitted by a vector, the Oriental rat flea (Xenopsylla cheopis), which introduces the disease to humans through its bite; although its natural reservoir is the rat, other mammals, such as prairie dogs, are suspects for hosting this bacterium. In humans, infection with Y. pestis presents in three major forms: bubonic, septicemic, and pneumonic. All three forms are typically seen in a pandemic. A victim has the best chance of surviving bubonic plague, which occurs after a bite and is characterized by the presence of buboes—large, painful lymph node swellings that eventually suppurate. If the infection spreads from the buboes to the bloodstream, septicemic plague ensues, and dark purpuric lesions develop all over the body. If the infection spreads to the lungs, the patient is said to have pneumonic plague, which can spread from person to person by respiratory droplets. Both septicemic and pneumonic plague are uniformly deadly without antibiotics. However, because persons with these more serious forms of plague were likely to die before having a chance to spread the disease, it is widely held that the bubonic form was most responsible for the transmission of the infection throughout the pandemic.
Bacteria
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
Although this disease is now rare, in the Middle Ages it was responsible for the death of up to twenty-five percent of the human population of Europe. It is caused by Yersinia pestis, a pleomorphic rod that is maintained in wild rodents. Man is infected by the bite of fleas which leave the rodents after they have died of the disease. The bubonic form of plague results when rat fleas inject the agent while feeding. In this form of the disease Y. pestis becomes localized in the lymph nodes draining the area of the bite. When the nodes become enlarged, they are called buboes. The infection progresses throughout the body. Sometimes the lungs become infected. When this happens, the disease may be spread by aerosols produced by coughing. This form is called pneumonic plague. The disease is readily treatable with streptomycin but if untreated may be rapidly fatal in a high proportion of cases.
Fleas
Published in Jerome Goddard, Public Health Entomology, 2022
Three clinical forms of plague are recognized: bubonic, septicemic, and pneumonic. The septicemic and pneumonic forms are usually secondary to the bubonic form, and the bubonic form is the most common in the Americas. Pneumonic plague is the most dangerous because of its rapid spread by aerosols (coughing).
Flagellin as a vaccine adjuvant
Published in Expert Review of Vaccines, 2018
Baofeng Cui, Xinsheng Liu, Yuzhen Fang, Peng Zhou, Yongguang Zhang, Yonglu Wang
Plague is an infectious disease of animals and humans caused by Yersinia pestis, a Gram-negative coccobacillus, that is acute and often fatal. Currently, there is no effective licensed vaccine that protects against pneumonic plague. However, a recombinant protein in which two protective antigens (F1 and V protein) of Y. pestis were fused to the hypervariable region of flagellin was designed to provide protection against respiratory exposure to Y. pestis [167]. Based on the results, the recombinant flagellin-F1-V protein was recognized by the TLR5 receptor and stimulated the production of proinflammatory cytokines, such as TNF-α, in vitro through the NK-κB pathway. Using a prime-boost immunization protocol, robust anti-F1 and anti-V humoral immunity in mice and two species of nonhuman primates was elicited by flagellin-F1-V. In immunized mice, the bacteria were completely cleared within 3 days of challenge. Based on outstanding preclinical results, the safety, immunogenicity, and tolerability of the flagellin-F1-V recombinant fusion protein were evaluated in humans. In phase I clinical trials (ClinicalTrials.gov Identifier: NCT01381744), increasing doses of the flagellin/F1/V vaccine in phosphate-buffered saline were administered via the i.m. route on days 0 and 28 to 18- to 45-year-old healthy volunteers. However, no further research results from phase I clinical trials have been formally posted to date.
Immunogenicity and protection efficacy of enhanced fitness recombinant Salmonella Typhi monovalent and bivalent vaccine strains against acute toxoplasmosis
Published in Pathogens and Global Health, 2021
Fei-Kean Loh, Sheila Nathan, Sek-Chuen Chow, Chee-Mun Fang
Heterologous antigens could be plasmid encoded or chromosomally integrated for expression in live S. Typhi vaccine. Plasmids can express high levels of antigens, but they tend to impose unacceptable metabolic burden that probably causes eventual plasmid loss. As an alternative, antigens expressed via chromosomal-based gene integration are more stable since the deletion of chromosomal genes is less likely [James E. 8]. However, a single chromosomal gene copy generally reduces the antigen mass, thus expressing insufficient level of antigen to induce an immune response [10]. This is a concern when developing T. gondii vaccines that require multiple antigens to confer cross-protection against the parasite’s changeable life stages. Remarkably, the coupling of plasmid- and chromosome-based antigen expression within single live Salmonella vaccines revealed the potential of gaining stable and adequate antigen expression with high immunity activation properties. Galen et al. constructed an S. Typhi bivalent plague vaccine combining plasmid expression of the F1 antigen and chromosomal expression of LcrV antigen of Yersinia pestis that conferred full protection against lethal pulmonary challenge in BALB/c mice [11]. Following that, Sanapala et al. constructed a trivalent Salmonella Typhimurium delivering LcrV196 and Psn of Yersinia pestis encoded on plasmid and F1 encoded within the chromosome that induced high antibody titers and significant protection against bubonic and pneumonic plague in BALB/c mice [12]. In recent years, Salmonella Choleraesuis has also been adapted as live vector to deliver SaoA antigen and enolase antigen that can confer full protection against Streptococcus suis [13., 2020; 14]. The high immunogenicity of live Salmonella vector achieved has encouraged its application toward vaccine development against a variety of human pathogens including T. gondii.