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stored in liquid nitrogen (Cameron, 1988), standardized mice (strain HSFS/ N) (Manclark et al., 1976), a freeze-dried reference vaccine (Armitage and Perry, 1957), and an interval between immunization and injection of 14 to 17 days (Cameron, 1988).

The intranasal mouse protection test has been improved by use of a standardized system for delivery of bacteria by aerosol (Sato and Sato, 1988). This test has been used for the study of the role in pathogenesis of bacterial adherence proteins, for example, the 69-kilodalton outer membrane protein (Shahin et al., 1990).

The toxicities of vaccines have been studied by the mouse weight gain test. This test depends on the observation that intraperitoneal injection of vaccine into young mice leads to a weight loss within hours, followed by total recovery of weight within the next 7 days (Cameron, 1988).  The causes of toxicity (manifested as poor weight gain) in the test are not well understood; the test is not very sensitive to endotoxin (Cameron, 1977). Results of the test have been shown to vary with the adjuvant or absorbent used with the vaccine, mouse strain, diet, size of cage, ambient temperature, and duration of exposure to light (Cameron, 1988). These vagaries further illustrate the difficulty of generalizing to humans the results obtained from studies in animals.

A sensitive assay for the particularly important toxin PT and for anti-PT has been developed by using Chinese hamster ovary (CHO) cells (Gillenius et al., 1985; Hewlett et al., 1983). In the presence of PT, CHO cells undergo a characteristic clumping, which can be blocked with antibody to PT. The test can detect PT at levels one-fiftieth those of the next most sensitive assay (Cameron, 1988).

In summary, B. pertussis is a complex organism, multiple factors having been proposed as possible contributors to its virulence. Their role in whooping cough has not been clearly established. Without better understanding of the organism and the human disease, it cannot be concluded with confidence that data from animal models relate to findings in humans. 

REFERENCES

Armitage P, Perry WLM. 1957. British standard for pertussis vaccine: its use in routine control of commercial vaccines. British Medical Journal 2:501-505.

Ashworth LAE, Irons LI, Dowsett AB. 1982. Antigenic relationship between serotype-specific agglutinogen and fimbriae of Bordetella pertussis. Infection and Immunity 37:1278-1281.

Berenbaum MC, Ungar J, Stevens WK. 1960. Intracranial infection of mice with Bordetella pertussis. Journal of General Microbiology 22:313-322.

Cameron J. 1977. Pertussis vaccine: mouse-weight-gain (toxicity) test. Developments in Biological Standardization 34:213-215.

Cameron J. 1988. Evaluation of control testing of pertussis vaccines. In: Wardlaw AC, Parton R, eds. Pathogenesis and Immunity in Pertussis. New York: John Wiley & Sons.



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