Mkr. Tummuru et al., MUTATION OF THE CYTOTOXIN-ASSOCIATED CAGA GENE DOES NOT AFFECT THE VACUOLATING CYTOTOXIN ACTIVITY OF HELICOBACTER-PYLORI, Infection and immunity, 62(6), 1994, pp. 2609-2613
Helicobacter pylori now is recognized as an etiological agent in chron
ic superficial gastritis and peptic ulcer disease. Although only about
60% of H. pylori isolates produce an immunodominant 128-kDa antigen (
CagA; cytotoxin-associated gene product), virtually all H. pylori-infe
cted patients with duodenal ulceration develop a serologic response to
the 128-kDa protein, which suggests an association of this gene with
ulceration. The cloned cagA gene from H. pylori 84-183 was disrupted b
y insertion of a kanamycin resistance gene, and this inactivated cagA
construct was introduced into H. pylori 84-183 by electrotransformatio
n. Southern hybridization of kanamycin-resistant H. pylori transforman
ts demonstrated that the wild-type cagA gene had been disrupted by ins
ertion of the kanamycin cassette, and immunoblot analysis showed that
the mutant strains no longer produced the 128-kDa CagA protein. Simila
r results were obtained when the cagA mutation was introduced by natur
al transformation into H. pylori 60190, a high-level toxin-producing s
train. The cagA-negative H. pylori strains showed cytotoxin, urease, a
nd phospholipase C activities, C3 binding, and adherence similar to th
ose of the isogenic wild-type strains. These findings demonstrate that
the cagA gene product does not affect the vacuolating cytotoxin activ
ity of H. pylori.