In vivo adaptation of the Wayne model of latent tuberculosis

Abstract

Cultures of Mycobacterium tuberculosis grown under oxygen depletion conditions enter into a state of nonreplicating persistence that may reflect a physiologically latent state. When these cultures were harvested and injected intranasally into mice, no bacteria could be recovered from the lungs for about 3 weeks, but after that evidence of regrowth was observed. Preimmunization of mice with a panel of selected vaccine candidates slowed or prevented this event. This simple model has potential for identifying vaccines targeting latent tuberculosis.

FIG. 1.

Growth of freshly thawed regular cultures (squares) and “Wayne cultures” (triangles) adjusted for similar viabilities in the lungs of mice after intranasal inoculation. Data shown are means for four to five mice plus standard errors. Because of the high variance, the day 30 values were marginally significant (P = 0.04) whereas the day 62 counts were not significant.

FIG. 2.

Histopathological appearance of representative lung sections taken from vaccinated mice showing evidence of bacterial regrowth. (A) Severe granulomatous inflammation with evident areas of necrosis in mice injected with adjuvant only. (B) Tight lymphocytic mass around a vessel in the single ESAT-vaccinated mouse showing regrowth. (C) Larger lymphocytic granuloma in mice vaccinated with BfrB. Similar patterns were seen in the Erp-vaccinated group (not shown). (D) Lesion in BCG-vaccinated mice. Note the similarity to panel B. (E and F) In contrast, mice vaccinated with HspX showed much larger, less organized granulomas (E), often associated with evident acid-fast bacilli (F). For panels A through E, hematoxylin-and-eosin staining was used; magnification, ×200. For panel F, acid-fast bacillus staining was used.