GADD34 DC/DC neonates are extremely sensitive to CHIKV infection and display signs of acute myocarditis and ventricles dilatation probably causing recurrent cardiac failures. CHIKV cardiac tropism is not normally observed in WT mouse and inability of heart tissues to produce sufficient type-I IFN in GADD34 DC/DC could allow abnormally high viral replication, myocarditis and dilated cardiomyopathy. Interestingly many cases of myopericarditis induced by CHIKV and leading to dilated cardiomyopathies in infected patients have been reported since the Figure 7 . CHIKV infection in mouse neonates. A) Kaplan-Meier plots representing the survival of FVB (WT) and GADD34 DC/DC mouse neonates 9-day-old (n = 11 per group) (upper panel) or 12-day-old (n = 14 per group) (lower panel) after intradermal inoculation with 10 6 PFU of CHIKV and observed for 21 days. B) Left panel, viral titers in different tissues and serum of 12-day-old mice inoculated with 10 6 PFU of CHIKV via the intradermal route. Mice were sacrificed 5 days after infection and the amount of infectious virus in serum and tissues quantified by TCID50 (see methods) (n = 5). In addition of considerably increased levels of viral replication in CHIKV target tissues, GADD34 DC/DC neonates also display signs of heart infection. Right panel, Quantification of IFN-b for the same different tissues, CHIKV-infected target tissues of GADD34 DC/DC mice produced less IFN-b than WT. C) 17-day-old mice were infected with 10 6 PFU of CHIKV via the intradermal route, and sacrificed 72 h later. Quantification of viral titers and IFN-b/ viral titers ratio is presented for different tissues. A broken line indicates the detection threshold. In B and C represented data are arithmetic mean 6 standard deviation, n = 5. In B and C p values were calculated using a Student's t test, *p#0.1, **p#0.05. doi:10.1371/journal.ppat.1002708.g007 Figure 8 . CHIKV infection causes severe myocarditis in mouse neonates. Histological appearance of horizontal sections of the heart through left and right ventricles of 12-day FVB (A, C and E) and GADD34 DC/DC mice at D5 pi (B, D and F). Normal appearance of heart of FVB infected mice, at low magnification (A, 610) with normal cardiomyocytes (C, 6100) and exceptional small foci of lymphocytes (E, 6400). Numerous foci of necrosis in the heart of GADD34 DC/DC infected mice, at low magnification (B, 610) and extensive through the ventricular wall (D, 6100). Higher magnification shows few residual cardiomyocytes (arrow head) and inflammation mainly composed of monocytes as well as extensive deposition of calcium (F, 6400). The mice were inoculated with 10 6 PFU of CHIKV via the intradermal route. doi:10.1371/journal.ppat.1002708.g008