Establishment of a perinatal cytomegaiovirus (CMV) induced hepatobiliary system injury model in guinea pigs

Objective To establish a perinatal cytomegalovirus (CMV) induced hepatobiliary system injury model in guinea pigs. Methods Three experimental groups were designed as follows. (1) Prenatal group (Group P): Female guinea pigs on the 40th to 43rd gestational day were randomly allocated into 3 subgroups. Guinea pigs in group P1 and P2 accepted intraperitoneal injection of virus supernatant with the dose of 1 10 9 TCID per dam and saline respectively, while guinea pigs in group P3 served as blank control. Live-born pups were sacrificed within 24 hours, on day 10 or 20 after birth. Samples of livers, extrahepatic bile duct and blood were collected. Weight gain, clinical signs of hepa-tobiliary injury (I. E. , jaundice in non-fur-covered skin, acholic stools) and survival were recorded. (2) Neonatal group (Group N) : A subset of healthy pups accepted intraperitoneal injection of virus supernatant at the dose of 1 108 TCID per pup within 24 hours after birth. Samples were collected on day 10, 20, or 30 after birth. (3) Infantile Group (Group Ⅰ): Healthy pups were inoculated with a same dose of virus supernatant on day 10 after birth. Samples were harvested on day 10, 20 or 30 after inoculation. The level of total bilirubin (TB), direct bilirubin (DB), ALT and AST in blood samples was analyzed. Serial sections of the liver or extrahepatic bile duct fixed in formalin were stained with Hematoxylin and Eosin. Hybridization in situ was applied on frozen sections to detect the distribution of viral mRNA. Results Compared to those in the control group, TB, DB, ALT and AST levels in Pups infected prenatally were significantly higher within the first 10 days of life (P<0. 05), and de-creased to the normal level on 20th day of life. A few pups of P1 group got the signs of jaundice (ie. Acholic stools ), which were associated with increased TB and DB level. In the neonatal group, a higher AST level was observed on the 10th day post inoculation in pups but it returned to normal soon. Birth weight of pups infected prenatally was significantly lower than the saline injection group or the blank control group (P = 0. 0029, P = 0027, respectively). Significant growth retardation was noted after 20 days post inoculation, while not noted in the neonatal or infantile group. Histological analysis of the livers revealed a notable infil-tration of mononuclear cells in 63. 6% (14/22) of pups in the prenatal group. Inflammatory cells were mainly found in portal tract area. Interlohular portal tract damage and fihrosis together with bile ductular proliferation were noted. Balloon-like degeneration, necrosis and ductular cholestasis were found in liver tissues of a part of pups. Micro-abscesses were occasionally observed. Pathological changes were also found in pups inoculated within the first day of life (3/8), but not as severe as those in the prenatal group. No significant pathologic change was found in the infantile group. The gpCMV rnRNA signal was found in endothelia, epithelia and portal tract stoma, while no signal was found on hepatoeytes. Positive rate of gpCMV was 17. 27% (4/22) in pups of Group P1, significantly lower than that in pups of Group N or Ⅰ (55% vs 50%, respectively). Conclusions Intraperitoneal injection with non-enhanced gpCMV on the late gestational days of pregnant guinea pigs or within 24h after birth of neonatal pups could induce inflammation and injury in the hepatobiliary system. Key words: Hepatobiliary system injury; Cytomegalovirus infections; Perinatal