1. Tissue cyst yields and size distribution during the course of chronic infection.
Tissue cyst yields and size distribution during the course of chronic infection. (A) The average tissue cyst yield from 99 independent Percoll gradient purifications was established as described in Materials and Methods. In spite of considerable heterogeneity at each time point, the mean yield (black line) was found to be very similar and not statistically significant (one-way ANOVA, F4,94 = [P = ], α = 0.05). The mean tissue cyst burden per mouse was established as described in Materials and Methods and in Text S1 in the supplemental material. The actual means and standard deviations are reported in Table 1. (B) Evidence of spontaneous reactivation in the brain of an infected CBA/J mouse harvested 4 weeks postinfection. The enlarged DIC image reveals two tissue cysts and two tachyzoite vacuoles (red arrows). The tissue cysts are evident as Dolichos biflorus agglutinin (DBA) lectin-positive halos and by the patterns of the DNA labeling (small yellow arrows). In contrast, the tachyzoites vacuoles lack a cyst wall, and as a result, they are DBA negative (small red arrows). (C) Distribution of the diameters of tissue cysts harvested 3, 4, 5, 6, and 8 weeks postinfection exhibit considerable heterogeneity at all time points. Statistical analysis by ANOVA reveals diverse level of significance (F4,625 = 6.307; P < ). The analysis between weeks was done using Tukey’s pairwise multiple-comparison test (α = 0.05). A mean diameter (black line) that differed significantly from another is indicated by the letter Y (for yes), and the level of significance is indicated by the number of asterisks. The letter N (for no) indicates that the two mean diameters being compared did not differ significantly.
Elizabeth Watts et al. mBio 2015; doi: /mBio