Mouse lung infection model to assess Rhodococcus equi virulence and vaccine protection

作者：Gonzalez Iglesias Patricia; Scortti Mariela^*; MacArthur Iain; Hapeshi Alexia; Rodriguez Hector; Prescott John F; Vazquez Boland Jose A

来源：Veterinary Microbiology, 2014, 172(1-2): 256-264.

DOI：10.1016/j.vetmic.2014.03.026

• Rhodococcus equi
• Mouse model
• Lung infection
• Virulence
• Competitive virulence assay
• Vaccine assessment

The pathogenic actinomycete Rhodococcus aqui causes severe purulent lung infections in foals and immunocompromised people. Although relatively unsusceptible to R. aqui, mice are widely used for in vivo studies with this pathogen. The most commonly employed mouse model is based on systemic (intravenous) infection and determination of R. aqui burdens in spleen and liver. Here, we investigated the murine lung for experimental infection studies with R. aqui. Using a 107 CPU intranasal challenge in BALB/c mice, virulent R. aqui consistently survived in quantifiable numbers up to 10 days in the lungs whereas virulence-deficient R. equi bacteria were rapidly cleared. An internally controlled virulence assay was developed in which the test R. aqui strains are co-inoculated and monitored in the same mouse. Isogenic R. aqui bacteria lacking either the plasmid vapA gene or the entire virulence plasmid were compared using this competitive assay. Both strains showed no significant differences in in vivo fitness in the lung, indicating that the single loss of the virulence factor VapA was sufficient to account for the full attenuation seen in the absence of the virulence plaimid. To test the adequacy of the lung infection model for monitoring R. aqui vaccine efficacy, BALB/c mice were immunized with live R. aqui and challenged intranasally. Vaccination conferred protection against acute pulmonary challenge with virulent R. aqui. Our data indicate that the murine lung infection model provides a useful tool for both R. aqui virulence and vaccine studies.

• 出版日期2014-8-6