CD8 Knockout Mice Are Protected from Challenge by Vaccination with WR201, a Live Attenuated Mutant of Brucella melitensis

Table 1

Six-week-old male C57BL/6 and CD8 knockout (CD8 KO) mice were orally immunized with 10¹¹ WR201 and eight weeks later challenged with 10⁴ B.  melitensis 16 M. Figures at 1 day and 2 weeks after challenge, when most or all animals were infected, are mean CFU ± SD. At 4 and 8 weeks, when many animals had cleared the infection and mean CFU counts became less meaningful, figures are shown as ratio of cleared/total. At day 1, 𝑛=5 for C57BL/6 and 𝑛=4 for CD8 KO; at 2 weeks 𝑛=10 for all groups. CFU comparisons utilized Student’s 𝑡-test while clearance comparisons utilized Fisher’s exact test.

Organ	Time after challenge	C57BL/6 immunized	C57BL/6 naive	𝑃 value; C57BL/6 immunized versus naive	CD8 KO immunized	CD8 KO naïve	𝑃 value; CD8 KO immunized versus naive	𝑃 value immunized versus immunized	𝑃 value naïve versus naive
Liver	2 wks	1.53 ± 0.840	2.91 ± 0.646	<0.01	1.58 ± 0.887	2.88 ± 0.646	<0.05	>0.05	>0.05
	4 wks	9/10	1/10	<0.001	7/10	0/10	<0.01	>0.05	>0.05
	8 wks	17/18	11/19	<0.05	20/23	14/20	>0.05	>0.05	>0.05
Spleen	2 wks	1.29 ± 0.676	2.46 ± 1.22	<0.05	1.59 ± 0.227	1.62 ± 0.662	>0.05	>0.05	>0.05
	4 wks	6/10	1/10	<0.05	6/10	0/10	<0.01	>0.05	>0.05
	8 wks	12/18	1/19	<0.001	12/23	1/20	<0.001	>0.05	>0.05
Lung	1 day	3.38 ± 0.66	3.32 ± 0.18	>0.05	3.48 ± 0.21	3.81 ± 0.14	>0.05	>0.05	>0.05
	2 wks	2.2 ± 0.89	2.03 ± 1.17	>0.05	2.32 ± 0.82	3.08 ± 0.66	>0.05	>0.05	0.048
	4 wks	8/10	4/10	>0.05	4/8	1/10	>0.05	>0.05	>0.05
	8 wks	11/16	11/19	>0.05	10/23	10/20	>0.05	>0.05	>0.05