Effect of herpesvirus infection on pancreatic duct cell secretion

To examine the effect of acute infection caused by herpesvirus (pseudorabies virus, PRV) on pancreatic ductal secretion.

The virulent Ba-DupGreen (BDG) and non-virulent Ka-RREp0lacgfp (KEG) genetically modified strains of PRV were used in this study and both of them contain the gene for green fluorescent protein (GFP). Small intra/interlobular ducts were infected with BDG virus (10(7) PFU/mL for 6 h) or with KEG virus (10(10) PFU/mL for 6 h), while non-infected ducts were incubated only with the culture media. The ducts were then cultured for a further 18 h. The rate of HCO(3)(-) secretion (base efflux -J(B-)) was determined from the buffering capacity of the cells and the initial rate of intracellular acidification (1) after sudden blockage of basolateral base loaders with dihydro-4,4-diisothiocyanatostilbene-2,2-disulfonic acid (500 micromol/L) and amiloride (200 micromol/L), and (2) after alkali loading the ducts by exposure to NH(4)Cl. All the experiments were performed in HCO(3)(-)-buffered Ringer solution at 37 degrees (n = 5 ducts for each experimental condition). Viral structural proteins were visualized by immunohistochemistry. Virally-encoded GFP and immunofluorescence signals were recorded by a confocal laser scanning microscope.

The BDG virus infected the majority of accessible cells of the duct as judged by the appearance of GFP and viral antigens in the ductal cells. KEG virus caused a similarly high efficiency of infection. After blockage of basolateral base loaders, BDG infection significantly elevated -J(B-) 24 h after the infection, compared to the non-infected group. However, KEG infection did not modify -J(B-). After alkali loading the ducts, -J(B-) was significantly elevated in the BDG group compared to the control group 24 h after the infection. As we found with the inhibitor stop method, no change was observed in the group KEG compared to the non-infected group.

Incubation with the BDG or KEG strains of PRV results in an effective infection of ductal epithelial cells. The BDG strain of PRV, which is able to initiate a lytic viral cycle, stimulates HCO(3)(-) secretion in guinea pig pancreatic duct by about four- to fivefold, 24 h after the infection. However, the KEG strain of PRV, which can infect, but fails to replicate, has no effect on HCO(3)(-) secretion. We suggest that this response of pancreatic ducts to virulent PRV infection may represent a defense mechanism against invasive pathogens to avoid pancreatic injury.