The online version of this article (doi: 10.1186/s12985-017-0911-5) contains supplementary material, which is available to authorized users.
Enterovirus (EV) infection has been a serious health issue in Asia-Pacific region. It has been indicated that the occurrence of fatal hand foot and mouth disease (HFMD) cases following EV71 infection is mainly attributed to pulmonary edema. However, the development of pulmonary disorders after EV71 infection remains largely unknown. To establish an EV71-infected animal model and further explore the underlying association of central nervous system (CNS) invasion with pulmonary edema, we isolated a clinical source EV71 strain (ZZ1350) from a severe case in Henan Province.
We evaluated the cytotoxicity of ZZ1350 strain and the susceptibility in 3-day-old BALB/c mice with intraperitoneal, intracerebral and intramuscular inoculation. Various histopathological and immunohistochemical techniques were applied to determine the target organs or tissue damage after infection. Correlation analysis was used to identify the relationship between CNS injury and pulmonary disorders.
Our experimental results suggested that ZZ1350 (C4 subtype) had high cytotoxicity against African green monkey kidney (Vero) cells and human rhabdomyosarcoma (RD) cells and neonatal BALB/c mice were highly susceptible to the infection with ZZ1350 through three different inoculation routes (2 × 106 pfu/mouse) exhibiting severe neurological and respiratory symptoms that were similar to clinical observation. Viral replication was found in brain, spinal cord, skeletal muscle, lung, spleen, liver, heart of infected mice and these sections also showed histopathological changes. We found that brain histology score was positive correlated with lung histology score in total experimental mice and mice under the three inoculation routes (P < 0.05). At the same time, there were positive correlations between spinal cord score and lung score in total experimental mice and mice with intracerebral inoculation (P < 0.05).
ZZ1350 strain is effective to establish animal model of EV71 infection with severe neurological and respiratory symptoms. The development of pulmonary disorders after EV71 infection is associated with severity of CNS damage.
Additional file 1: Figure S1. RD cells exhibited obvious CPE following ZZ1350 infection. Control and infected RD cells at 60 hpi were captured under a light microscope (amplification: 100×). (TIFF 2294 kb)
Additional file 3: Figure S2. Weight loss after ZZ1350 infection. Body weight of mice (n = 7 for intracerebral inoculation; n = 6 for intramuscular inoculation; n = 6 for intraperitoneal inoculation and n = 5 for normal controls) was recorded every 2 days after ZZ1350 infection. Data are expressed as mean ± SEM. (TIFF 382 kb)
Additional file 4: Figure S3. ZZ1350 infection caused mice limb weakness. Percentage of limb paralysis of mice with three inoculation routes was recorded and calculated at 7 dpi. Limb paralysis (%) of mice with intracerebral (n = 7), intramuscular (n = 6) and intraperitoneal inoculation (n = 6) was 85.7%, 83.3%, 83.3% respectively. (TIFF 803 kb)
Additional file 5: Figure S4. ZZ1350 infection increased number of astrocytes in mouse brain. Astrocytes in brains from normal control (A-a) and mice with intracerebral (A-b), intramuscular (A-c), intraperitoneal inoculation (A-d) were determined by GFAP staining. B: Quantitative analysis of astrocytes number in slices of mice brains. Data are expressed as mean ± SEM. *** P < 0.001, intracerebral (n = 15), intramuscular (n = 12), or intraperitoneal inoculation (n = 11) vs normal controls (n = 10). (TIFF 3886 kb)
Additional file 6: Figure S5. ZZ1350 infection induced mucus production and alveolar space enlargement in mice lungs. Mucus production was determined by Masson’s Trichrome and PAS staining (A). Lm (B) was calculated based on 10 randomly selected fields in each section at 100× magnification with two crossed test lines. Data are expressed as mean ± SEM. *** P < 0.001, intracerebral (n = 15), intramuscular (n = 12), or intraperitoneal inoculation (n = 11) vs normal controls (n = 10). (TIFF 2944 kb)
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- Pulmonary edema following central nervous system lesions induced by a non- mouse-adapted EV71 strain in neonatal BALB/c mice
- BioMed Central
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