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J. Exp. Med.,
Volume 187, Number 1, January 5, 1998 135-140
By


From the * Centro CNR Biomembrane and Dipartimento di Scienze Biomediche, Università di
Padova, 35121 Padova, Italy; the A major virulence factor in the stomach chronic infection by Helicobacter pylori is a protein toxin
(VacA), which alters cell membrane trafficking of late endosomal/prelysosomal compartments. Its role in the chronic infection established by H. pylori is unknown. To test the possibility that
VacA alters antigen processing taking place in prelysosomal compartments, we have used the
well-established model of antigen processing and presentation consisting of tetanus toxoid-specific human (CD4+) T cells stimulated by autologous antigen-pulsed Epstein-Barr virus-transformed B cells. We found that VacA interferes with proteolytic processing of tetanus toxin and
toxoid and specifically inhibits the Ii-dependent pathway of antigen presentation mediated by
newly synthesized major histocompatibility complex (MHC) class II, while leaving unaffected
the presentation pathway dependent on recycling MHC class II. The results presented here
suggest that VacA may contribute to the persistence of H. pylori by interfering with protective
immunity and that this toxin is a new useful tool in the study of the different pathways of antigen presentation.
Basel Institute for Immunology, 4005 Basel, Switzerland; and the § Centro Ricerche IRIS, Chiron-Vaccines, 53100 Siena, Italy
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