Deletion in the Shigella enterotoxin genes further attenuates Shigella flexneri 2a bearing guanine auxotrophy in a phase 1 trial of CVD 1204 and CVD 1208.
BACKGROUND
We created a live, attenuated, oral Shigella vaccine by constructing a lineage of guanine auxotrophs and conducted a double-blind, placebo-controlled trial to ascertain (1) the attenuation profile of Delta guaBA Shigella flexneri 2a, which harbors deletions in the guanine nucleotide synthesis pathway (CVD 1204); (2) additional attenuation conferred by deletions in set and sen genes encoding Shigella enterotoxins (ShETs) 1 and 2, respectively (CVD 1208); and (3) the relative immunogenicity of these constructs.


METHODS
Inpatient volunteers received a single oral dose of CVD 1204, CVD 1208 (10(7), 10(8), or 10(9) cfu), or placebo. Clinical, immunologic, and microbiologic responses were evaluated.


RESULTS
Reactogenicity occurred in 8 of 23 recipients of CVD 1204, characterized by diarrhea (30%), fever (22%), and/or dysentery (17%), but in only 1 (5%) of 21 recipients of CVD 1208 (brief fever) (P=.02, Fisher's exact test). Antilipopolysaccharide responses, as measured by antibody-secreting cell, serum, or fecal antibody levels, occurred in 67%, 71%, and 100% of recipients of CVD 1204 and in 86%, 43%, and 100% of recipients of CVD 1208 at doses of 10(7), 10(8), and 10(9) cfu, respectively.


CONCLUSIONS
We conclude that 1 or both ShETs are virulence determinants in humans; their inactivation, in combination with Delta guaBA, leads to a well-tolerated and immunogenic Shigella vaccine candidate.
Kotloff
Karen L
KL
Division of Infectious Disease and Tropical Pediatrics, Department of Pediatrics, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA. kkotloff@medicine.umaryland.edu
Pasetti
Marcela F
MF
Barry
Eileen M
EM
Nataro
James P
JP
Wasserman
Steven S
SS
Sztein
Marcelo B
MB
Picking
William D
WD
Levine
Myron M
MM
D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000907:Antibodies, Bacterial / Q000032:analysis / Q000097:blood; D000921:Antibody-Producing Cells / Q000276:immunology; D001426:Bacterial Proteins / Q000235:genetics; D004311:Double-Blind Method; D004768:Enterotoxins / Q000235:genetics*; D005334:Fever / Q000209:etiology; D017353:Gene Deletion; D006147:Guanine / Q000378:metabolism; D006801:Humans; D007070:Immunoglobulin A / Q000032:analysis / Q000097:blood; D007074:Immunoglobulin G / Q000032:analysis / Q000097:blood; D008070:Lipopolysaccharides / Q000276:immunology; D008875:Middle Aged; D009154:Mutation; D010919:Placebos; D022281:Shigella Vaccines / Q000009:adverse effects / Q000276:immunology*; D012763:Shigella flexneri / Q000235:genetics* / Q000254:growth & development / Q000276:immunology / Q000472:pathogenicity; D014613:Vaccines, Attenuated / Q000009:adverse effects / Q000276:immunology
D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D004768:Enterotoxins; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D010919:Placebos; D022281:Shigella Vaccines; D014613:Vaccines, Attenuated; D006147:Guanine