RESUMO
Francisella tularensis is a highly infectious Gram-negative bacterium that is the etiologic agent of tularemia in animals and humans. The incidence of tularemia is very low with a lack of comprehensive data that describe disease in humans due to difficulty in understanding time and routes of exposure. Under the title Operation Whitecoat, researchers at Ft. Detrick, MD conducted 40 clinical studies of tularemia from 1958 to 1968. In these studies, one of the objectives was to evaluate candidate countermeasures for treatment or prophylaxis of disease after exposure to Francisella tularensis strain Schu S4 by inhalation. These studies were reviewed retrospectively to delineate the early signs and symptoms or natural history of pneumonic tularemia and examine the efficacy of tetracycline in controlled human clinical studies. Using vital signs, onset of fever was objectively defined and calculated for each subject, while Adverse Events reported after exposure were also used to define the timing of disease onset and symptoms of early disease. There was a dose response relationship between time to fever onset and exposed dose at 200 cfu (172.8 h), 700 cfu (163.2 h), 2,500 cfu (105.3 h), and 25,000 cfu (75.5 h). Onset of fever was typically the earliest sign of disease at all doses but was often accompanied by symptoms such as headache, myalgia, chest pain, and nausea, irrespective of dose except at 200 cfu where only 50% of subjects exhibited fever onset or symptoms. Examining the efficacy of different treatment regimens of tetracycline, ineffective treatments were indicated by relapse of disease (fever and Adverse Events) after cessation of antibiotic treatment. Stratification of the data suggested that treatment for <14 days or doses <2g/day was associated with increased percentage of subjects with relapse of disease symptoms. Although these types of human challenge studies would not be ethically possible now, the climate post-World War II supported human testing under rigorous conditions with informed consent. Thus, going back and analyzing these unique clinical human challenge studies has helped describe the course of infection and disease induced by a biothreat pathogen and possible countermeasures for treatment under controlled conditions.
RESUMO
Chikungunya virus, transmitted by mosquitoes to man, causes an acute illness characterized by fever, rash and striking joint symptoms. US Military investigators developed, manufactured at The Salk Institute-Government Services Division (TSI-GSD), and tested the live, attenuated Chikungunya Vaccine TSI-GSD-218. The manufacturing facility stopped production in 1994. The Chikungunya Vaccine TSI-GSD-218 development effort was terminated in 1998, and materials were archived. In 2005, an alarming outbreak of chikungunya disease began in Africa and spread to islands in the Indian Ocean and throughout much of Asia. Abrupt epidemics with high attack rates and serious, even fatal, complications were reported, and travelers carried the virus to Europe and the Americas. In response to urgent requests, the US Military offered assistance by providing non-exclusive access to the previously stored vaccine production seed materials, bulk vaccine, regulatory documentation, and reports of previous clinical trials. Five companies requested technology transfers. This experience provides lessons about epidemiological unpredictability, preparedness, vaccine manufacturing, the potential global importance of vaccine seed materials and the advisability of a global strategic plan. Consideration should be given to banking of vaccine production seeds, cell substrates, and manufacturing instructions. In view of the manufacturability, attenuation, and immunogenicity of Chikungunya Vaccine TSI-GSD-218, authorities may wish to consider this product as a possible candidate itself, as a comparator vaccine to improve upon, as a seed for inactivated vaccine, or as a source of virus or antigen for neutralization assays or immunoassays.