SUMMARY Almost two decades after identification of the CFTR gene, we lack answers to many questions about the pathogenesis of cystic fibrosis (CF), and it remains a lethal disease. Mice with a disrupted CFTR gene have greatly facilitated CF studies, but they fail to develop the characteristic pancreatic, lung, intestinal, liver, and other CF manifestations. Therefore, we produced pigs with a targeted disruption of both CFTR alleles. These animals exhibited defective chloride transport. They also developed meconium ileus, exocrine pancreatic destruction, and focal biliary cirrhosis, replicating abnormalities seen in newborn patients with CF. This swine model may provide opportunities to address persistent questions about CF pathogenesis and accelerate discovery of treatments and preventions.

NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptLung disease causes most of the morbidity and mortality in cystic fibrosis (CF). However, understanding its pathogenesis has been hindered by lack of an animal model with characteristic features of CF. To overcome this problem, we recently generated pigs with targeted CFTR genes. We now report that, within months of birth, CF pigs spontaneously develop hallmark features of CF lung disease including airway inflammation, remodeling, mucus accumulation, and infection. Their lungs contained multiple bacterial species, suggesting an equal opportunity host defense defect. In humans, the temporal and causal relationships between inflammation and infection have remained uncertain. To investigate these processes, we studied newborn pigs. Their lungs showed no inflammation, but were less often sterile than controls. Moreover, after intrapulmonary bacterial challenge, CF pigs failed to eradicate bacteria as effectively as wild-type pigs. These results suggest that impaired bacterial elimination is the pathogenic event that initiates a cascade of inflammation and pathology in CF lungs. Finding that CF pigs have a bacterial host defense defect within hours of birth provides an opportunity to further investigate pathogenesis and to test therapeutic and preventive strategies before secondary consequences develop.

Mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) anion channel cause the autosomal recessive disease, cystic fibrosis (CF). The most common mutation is ΔF508, which deletes phenylalanine508. In vitro studies indicate that CFTR-ΔF508 is misprocessed, though in vivo consequences of the mutation are uncertain. To better understand effects of the ΔF508 mutation, we produced CFTRΔF508/ΔF508 pigs. Our biochemical, immunocytochemical and electrophysiological data on CFTR-ΔF508 in newborn pigs paralleled in vitro results. They also indicated that CFTRΔF508/ΔF508 airway epithelia retain a small residual CFTR conductance; maximal stimulation produced ~6% of wild-type function. Interestingly, cAMP agonists were less potent at stimulating current in CFTRΔF508/ΔF508 epithelia, suggesting that quantitative tests of maximal anion current may overestimate transport under physiological conditions. Despite residual CFTR function, four older CFTRΔF508/ΔF508 pigs developed lung disease strikingly similar to human CF. These results suggest that this limited CFTR activity is insufficient to prevent lung or gastrointestinal disease in CF pigs. These data also suggest that studies of recombinant CFTR-ΔF508 misprocessing predict in vivo behavior, which validates its use in biochemical and drug discovery experiments. These findings help elucidate the molecular pathogenesis of the common CF mutation and will guide strategies for developing new therapeutics.

No abstract

Phosphatidylserine (PS), which is exposed on the surface of apoptotic cells, has been implicated in immune regulation. However, the effects of PS on the maturation and function of dendritic cells (DCs), which play a central role in both immune activation and regulation, have not been described. Large unilamellar liposomes containing PS or phosphatidylcholine were used to model the plasma membrane phospholipid composition of apoptotic and live cells, respectively. PS liposomes inhibited the up-regulation of HLA-ABC, HLA-DR, CD80, CD86, CD40, and CD83, as well as the production of IL-12p70 by human DCs in response to LPS. PS did not affect DC viability directly but predisposed DCs to apoptosis in response to LPS. DCs exposed to PS had diminished capacity to stimulate allogeneic T cell proliferation and to activate IFN-γ-producing CD4+ T cells. Exogenous IL-12 restored IFN-γ production by CD4+ T cells. Furthermore, activated CTLs proliferated poorly to cognate Ag presented by DCs exposed to PS. Our findings suggest that PS exposure provides a sufficient signal to inhibit DC maturation and to modulate adaptive immune responses.

Appendicitis is the most common surgical abdominal emergency in the pediatric population, but is rarely considered in children less than 3 years of age. The goal of this study was to identify the presenting symptoms and signs in this age group and examine their subsequent management and outcome. A 28-year experience of a single pediatric surgeon in academic practice was reviewed; 27 children less than 3 years old (mean 23 months) comprised 2.3% of all children with appendicitis in his series. The most common presenting symptoms were vomiting (27), fever (23), pain (21), anorexia (15), and diarrhea (11). The average duration of symptoms was 3 days, with 4 or more days in 9 children. Eighteen children were seen by a physician before the correct diagnosis was made; 14 were initially treated for an upper respiratory tract infection, otitis media, or a urinary tract infection. The most common presenting signs were abdominal tenderness (27), peritonitis (24), temperature 38.0 degrees C or more (21), abdominal distension (18), Leukocytosis (<12.0 x 10(3)/mm(3)) was found in 18, tenderness was localized to the right lower quadrant (RLQ) in 14 and was diffuse in 10. Abdominal radiographs demonstrated findings of a small-bowel obstruction (SBO) in 14 of 21 patients, a fecalith in 2, and a pneumoperitoneum in 1. Contrast enemas were performed in 6 children, 5 of whom had a phlegmon or an abscess. Perforated appendicitis was found in all 27 patients. An appendectomy was performed in 25 and a RLQ drain was placed in 18. Postoperative antibiotics were administered to 17 children for an average of 6 days. Two patients underwent interval appendectomies, 1 following treatment with IV antibiotics and 1 following surgical drainage. The average time to resume oral intake was 7 days and the average hospital stay was 21 (median 15) days. Sixteen patients had 22 complications, which included 6 wound infections, 4 abscesses, 4 wound dehiscences, 3 pneumonias, 2 SBOs, 2 incisional hernias, and 1 enterocutaneous fistula. Perforated appendicitis was found in all children less than 3 years old, resulting in very high morbidity (59% complications), which may be attributed to the 3-5-day delay in diagnosis. Although appendicitis is uncommon in this age group, it should be seriously considered in the differential diagnosis of children under the age of 3 years who present with the triad of abdominal pain, tenderness, and vomiting.

No abstract

No abstract