Streptococcus pneumoniae Enhances Human Respiratory Syncytial Virus Infection In Vitro and In Vivo

PLoS One. 2015 May 13;10(5):e0127098. doi: 10.1371/journal.pone.0127098. eCollection 2015.

Abstract

Human respiratory syncytial virus (HRSV) and Streptococcus pneumoniae are important causative agents of respiratory tract infections. Both pathogens are associated with seasonal disease outbreaks in the pediatric population, and can often be detected simultaneously in infants hospitalized with bronchiolitis or pneumonia. It has been described that respiratory virus infections may predispose for bacterial superinfections, resulting in severe disease. However, studies on the influence of bacterial colonization of the upper respiratory tract on the pathogenesis of subsequent respiratory virus infections are scarce. Here, we have investigated whether pneumococcal colonization enhances subsequent HRSV infection. We used a newly generated recombinant subgroup B HRSV strain that expresses enhanced green fluorescent protein and pneumococcal isolates obtained from healthy children in disease-relevant in vitro and in vivo model systems. Three pneumococcal strains specifically enhanced in vitro HRSV infection of primary well-differentiated normal human bronchial epithelial cells grown at air-liquid interface, whereas two other strains did not. Since previous studies reported that bacterial neuraminidase enhanced HRSV infection in vitro, we measured pneumococcal neuraminidase activity in these cultures but found no correlation with the observed infection enhancement in our model. Subsequently, a selection of pneumococcal strains was used to induce nasal colonization of cotton rats, the best available small animal model for HRSV. Intranasal HRSV infection three days later resulted in strain-specific enhancement of HRSV replication in vivo. One S. pneumoniae strain enhanced HRSV both in vitro and in vivo, and was also associated with enhanced syncytium formation in vivo. However, neither pneumococci nor HRSV were found to spread from the upper to the lower respiratory tract, and neither pathogen was transmitted to naive cage mates by direct contact. These results demonstrate that pneumococcal colonization can enhance subsequent HRSV infection, and provide tools for additional mechanistic and intervention studies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Proteins / physiology
  • Cell Line
  • Coinfection / microbiology*
  • Female
  • Humans
  • Microbial Interactions
  • Nasal Septum / microbiology
  • Neuraminidase / physiology
  • Pneumococcal Infections / virology*
  • Respiratory Syncytial Virus Infections / microbiology*
  • Respiratory Syncytial Viruses / physiology*
  • Sigmodontinae
  • Streptococcus pneumoniae / physiology*

Substances

  • Bacterial Proteins
  • Neuraminidase

Grant support

This work was supported by the VIRGO consortium, an innovative cluster approved by the Netherlands Genomics Initiative and partially funded by the Dutch Government (grant #BSIK03012) and ZonMw (grant #91208012). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. A.D.M.E. Osterhaus co-founded and is a consultant of ViroClinics Biosciences B.V., a contract research organisation established in collaboration with Erasmus University. ViroClinics Biosciences B.V. had no role in funding, study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of this author is articulated in the author contributions’ sections. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.