Persistent infection by Helicobacter pylori down-modulates virus-specific CD8+ cytotoxic T cell response and prolongs viral infection.

To determine whether Helicobacter pylori infection affects clearance of a concomitant viral infection and cytotoxic T lymphocyte (CTL) and cytokine response to that infection, H. pylori-infected BALB/c mice were challenged with a recombinant vaccinia virus expressing human immunodeficiency virus type 1 gp160. Two H. pylori strains, a colonizing clinical isolate (KS612) and an established standard noncolonizing strain (NCTC11637), were compared. Clearance of recombinant vaccinia virus was reduced in KS612-infected mice compared with NCTC11637-infected and control mice. As a potential mechanism, in contrast to control or NCTC11637-infected mice, the H. pylori clinical isolate KS612 diminished gp160-specific and vaccinia virus-specific CTL activity, even in the presence of exogenous interleukin-2. Furthermore, KS612-infected mice had reduced Th1 cytokine responses to gp120 in vitro compared with control or NCTC11637-infected mice. These results have implications for possible effects of prevalent H. pylori infection on other human diseases.