Differential Pathogenesis of Respiratory Syncytial Virus Clinical Isolates in BALB/c Mice

Abstract

Airway mucus is a hallmark of respiratory syncytial virus (RSV) lower respiratory tract illness. Laboratory RSV strains differentially induce airway mucus production in mice. Here, we tested the hypothesis that RSV strains differ in pathogenesis by screening six low-passage RSV clinical isolates for mucogenicity and virulence in BALB/cJ mice. The RSV clinical isolates induced variable disease severity, lung interleukin-13 (IL-13) levels, and gob-5 levels in BALB/cJ mice. We chose two of these clinical isolates for further study. Infection of BALB/cJ mice with RSV A2001/2-20 (2-20) resulted in greater disease severity, higher lung IL-13 levels, and higher lung gob-5 levels than infection with RSV strains A2, line 19, Long, and A2001/3-12 (3-12). Like the line 19 RSV strain, the 2-20 clinical isolate induced airway mucin expression in BALB/cJ mice. The 2-20 and 3-12 RSV clinical isolates had higher lung viral loads than laboratory RSV strains at 1 day postinfection (p.i.). This increased viral load correlated with higher viral antigen levels in the bronchiolar epithelium and greater histopathologic changes at 1 day p.i. The A2 RSV strain had the highest peak viral load at day 4 p.i. RSV 2-20 infection caused epithelial desquamation, bronchiolitis, airway hyperresponsiveness, and increased breathing effort in BALB/cJ mice. We found that RSV clinical isolates induce variable pathogenesis in mice, and we established a mouse model of clinical isolate strain-dependent RSV pathogenesis that recapitulates key features of RSV disease.Respiratory syncytial virus (RSV) is the most important cause of bronchiolitis and viral pneumonia in children. Each year in the United States, RSV causes lower respiratory tract illness (LRI) in 20 to 30% of infants and leads to the hospitalization of approximately 1% of infants at a cost of $300 to $400 million (19,21,27). The incidence and disease severity of RSV can vary from year to year (47). Dominant circulating RSV strains are generally replaced each year, likely by a process involving immune selection (5,6,53,54). RSV strain differences may contribute to year-to-year and/or patient-topatient variations in clinical severity.In BALB/cJ mice, laboratory RSV strains (A2, Long, and line 19) differ in their ability to cause pulmonary interleukin-13 (IL-13) and mucin expression (34, 41). We are interested in RSV-induced mucin expression in mice because mucus overabundance contributes to airway obstruction in severe RSV disease in children (2,33,44,56). IL-13 is a cytokine linked to mucus production (71). The line 19 RSV strain induces lung IL-13 and airway mucin expression in BALB/cJ mice, whereas the A2 and Long RSV strains do not (34, 41). However, the in vitro passage histories of RSV strains A2, Long, and line 19 are not defined and involve many serial passages. Thus, it is possible that mutations in these RSV laboratory strains determine pathogenesis phenotypes in the mouse model. RSV clinical isolates have not been studied extensively in vivo, and the role of RSV strain differences in...

Cross-resistance mechanism of respiratory syncytial virus against structurally diverse entry inhibitors

“…Our study demonstrates the value of the recombinant RSV strain expressing renilla luciferase that we recently generated (32) for this task. Major advantages over conventional RSV-based assays explored for high-throughput campaigns are the broad dynamic range of the luciferase reporter; the availability of a full set of subinfection assays for MOA characterization that are genetically matched to the screening strain; the option to readily assess resistance in genetically controlled viral recombinants by using an efficient reverse genetics system; and the high pathogenicity of the reporter strain in the mouse model compared with standard laboratory RSV strains (40), opening a straightforward path toward small-animal efficacy testing of lead candidates.…”

“…Recently established, this mouse model using the recRSV A2-L19F strain exhibits higher lung viral loads, more airway mucus, and more severe respiratory distress than both the parental A2 and line 19 strains (38,42), recapitulating key clinical parameters of infant RSV bronchiolitis (38,40,55). Although it is not determined yet whether pathogenicity of a resistant RSV-F D401E would be equally unchanged in the human host, efficient replication in particular of this recombinant in the mouse model raises concern that resistance mutations in the hotspot around F residue 400 could become prevalent in circulating RSV strains should any of these entry inhibitor classes experience broad clinical use.…”

“…with minimum essential medium (MEM) containing 10% (vol/vol) FBS, penicillin G, streptomycin sulfate, amphotericin B solution, and 0.75% methylcellulose. Six days p.i., cells were fixed with methanol and plaques were visualized by immunodetection as described (40,42).…”

“…Heightened thermosensitivity may coincide with lowered viral fitness in vivo, which could render drug-resistant variants clinically insignificant. We used an established mouse model for RSV infection (40) to assess pathogenicity of the mutant viruses. Only the two recombinants expressing single-mutant F variants that had emerged spontaneously during adaptation were subjected to this study.…”

Virus-like particle vaccines containing F or F and G proteins confer protection against respiratory syncytial virus without pulmonary inflammation in cotton rats

“…21,32 Numerical assessment of histopathology was performed on a scale of 0-3 by blinded observers with the severity scoring system. 21,33 The mucin expression was detected with PAS-positive area. The degrees of pulmonary eosinophilia were indicated by eosinophil numbers present per 400£ field using H&CR stain.…”