Studies on Trachoma

III. Comparison of Virus Infectivity for Man and Chick Embryos

Samuel D. Bell Jr.Department of Microbiology, Harvard University, School of Public Health, Boston, Massachusetts

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Edward S. MurrayDepartment of Microbiology, Harvard University, School of Public Health, Boston, Massachusetts

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Thomas J. CarrollDepartment of Microbiology, Harvard University, School of Public Health, Boston, Massachusetts

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John C. SnyderDepartment of Microbiology, Harvard University, School of Public Health, Boston, Massachusetts

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Summary

Three experiments on six volunteers challenged with aliquots of the same pool of trachoma virus (Saudi Arabian strain 2) are described. Under the conditions of the experiments the endpoints for infectivity for chick embryos and the human eye closely approximated each other. Incubation of chick embryos infected with trachoma virus at 34.0° to 35.0°C with constant, high relative humidity increased the accuracy of titrations and raised the infectious endpoint several fold. The effects of formalin-killed vaccines on individuals vaccinated 3 years previously and boostered just prior to challenge were inconclusive.

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