Viral determinants of FMDV A/Arg/01 virulence in adult mice

CACCIABUE M.; CURRÁ A.; KÖNIG G.; RIEDER, E.; CARRILLO, E.; GISMONDI M.I.

Bangkok

Congreso; 2019 Meeting of the Global Foot-and-mouth Disease Research Alliance; 2019

Different animal models including adult C57 Bl/6J mice have been used to study FMDV biology and host susceptibility to viral infection. We previously characterized two FMDV A/Arg/01 variants derived from field isolates that circulated in Argentina during the 2000-2001 epizootia. These viruses exhibit differential virulence in adult C57 Bl/6J mice: FMDV A01NL is a non-lethal variant that causes mild signs of disease, whereas FMDV A01L is a lethal virus that causes death of all mice within 24-48 h, independently of the dose used (102-106 pfu/mice, intraperitoneal injection). Histological analysis showed that both viruses produce a systemic infection with pathological changes in the exocrine pancreas. Complete consensus sequences revealed 31 nucleotide changes between FMDV A01NL and FMDV A01L (6 non-synonymous, 23 synonymous and 2 changes in the 5? non-coding region). To evaluate the role of non-synonymous mutations (C2211T and T2515C in VP2, C3688T and A3775T in VP1, A4579G and A5086G in 2C) in the differential pathogenicity of both FMDV variants, a set of seven chimerical viruses with the mutations of FMDV A01L in the genetic backbone of an FMDV A01NL cDNA clone (A01NLc) were obtained and characterized. The engineered viruses include single substitutions (viruses 2211Lc, 2515Lc, 3688Lc, 3775Lc) or multiple mutations (viruses CapL, containing the VP2 and VP1 mutations; 2CL, containing the mutations present in 2C; and A01Lc, containing VP2, VP1 and 2C mutations). In order to evaluate the lethality of the chimerical viruses, groups of 9 week- old female mice were inoculated intraperitoneally with 105 pfu/mouse and monitored for 7 days. Blood samples were taken at 22 hours post infection (hpi) for virus titration. Mice inoculated with viruses 2211Lc, 2515Lc, 3688Lc, 3775Lc and 2CLc presented mild signs of disease at 48 hpi that reverted upon 72 hpi. This phenotype was indistinguishable from that of viruses A01NLc and FMDV A01NL. Contrarily, mice inoculated with A01Lc showed severe signs of disease or even died at 48 hpi; this virus displayed the same phenotype as the parental virus FMDV A01L. Of note, mice inoculated with CapLc showed moderate signs of disease at 48 hpi. Viral replication was evidenced at 22 hpi in all groups of mice as determined by virus titration. Viremia was significantly higher in mice inoculated with FMDV A01L and A01Lc (p