ABSTRACTNontypeableHaemophilus influenzae(NTHi) causes pulmonary infections in patients with chronic obstructive pulmonary disease and other mucociliary clearance defects. Like many bacteria inhabiting mucosal surfaces, NTHi produces lipooligosaccharide (LOS) endotoxins that lack the O side chain. Persistent NTHi populations express a discrete subset of LOS glycoforms, including those containing phosphorylcholine (PCho). In this study, we compared two NTHi strains with isogenic mutants lacking PCho for clearance from mice following pulmonary infection. Consistent with data from other model systems, populations of the strains NTHi 2019 and NTHi 86-028NP recovered from mouse lung contained an increased proportion of PCho+variants compared to that in the inocula. PCho−mutants were more rapidly cleared. Serial passage of NTHi increased both PCho content and bacterial resistance to clearance, and no such increases were observed for PCho−mutants. Increased PCho content was also observed in NTHi populations within non-endotoxin-responsive C3H/HeJ and Toll-like receptor 4 null (TLR4−/−) mice, albeit at later times postinfection. Changes in bacterial subpopulations and clearance were unaffected in TLR2−/−mice compared to the subpopulations in and clearance from mice of the parental strain. The clearance of PCho−mutants occurred at earlier time points in both strain backgrounds and in all types of mice. Comparison of bacterial populations in lung tissue cryosections by immunofluorescent staining showed sparse bacteria within the air spaces of C57BL/6 mice and large bacterial aggregates within the lungs of MyD88−/−mice. These results indicate that PCho promotes bacterial resistance to pulmonary clearance early in infection in a manner that is at least partially independent of the TLR4 pathway.

To determine the effects of expression of mutant Ki- ras on lung tumorigenesis, we developed a bitransgenic mouse model that expresses the human Ki- rasG12C allele in alveolar type II and/or Clara cells in a tetracycline-inducible, lung-specific manner. Expression of Ki- rasG12C caused multiple, small lung tumors over a 12-month time period. Although tumor multiplicity increased upon continued Ki- ras expression, most lung lesions were hyperplasias or well-differentiated adenomas. This is in contrast to the more severe phenotypes observed in other transgenic mouse models in which different mutant Ki- ras alleles were expressed in the lung. Expression of Ki- rasG12C was associated with a 2-fold increase in the activation of the Ras and Ral signaling pathways and increased phosphorylation of Ras downstream effectors, including Erk, p90 ribosomal S6 kinase, ribosomal S6 protein, p38 and MAPKAPK-2. In contrast, expression of the transgene had no effect on the activation of the JNK and Akt signaling pathways. Withdrawal of doxycycline for 1 month resulted in almost a complete absence of proliferative pulmonary lesions, suggesting tumor regression in the absence of Ki- ras expression. Mutant Ki- rasG12C expression was sufficient for initial lung tumor transformation, required for maintenance of tumor phenotype, and induced transformation of lung epithelial cells by the activation of multiple effector pathways. These results describe a novel mouse lung tumor model demonstrating benign tumor development in the absence of tumor progression, which will provide a new tool for understanding the early stages of lung tumor pathogenesis.

Following short-term signs of weakness, depression, and/or anorexia of less than 24 h, two adult male African green monkeys (Cercopithecus aethiops sabeus) of St. Kitts origin died from complications of cecal volvulus. Gaseous distention was radiologically apparent in one animal. Necropsy of both monkeys revealed cecal volvulus, one at the ileocecal junction and one involving a segment of the distal portion of the ileum and cecum. Congestion and hemorrhage were evident microscopically in the lamina propria of the affected intestine, with variable necrosis.