Chemistry Reference
In-Depth Information
Scheme 12
The cholera-protective response is mainly directed against LPS. The
VcO1 Ogawa polysaccharide was conjugated to bovine serum albumin
(BSA). The immune response exerted was very robust
132
reinforcing the
confidence in an LPS-based conjugate vaccine.
Kovac's group has reported a systematic synthesis of numerous
oligosaccharides related to both serotype Ogawa and serotype Inaba in
the expectation that their protein conjugates will induce specific anti-
bodies that might be protective.
133
Protective and vibriocidal sera were
not induced by epitopes smaller than hexasaccharide 38 containing the
terminal methylated perosamine.
134
In contrast, glycoconjugates con-
taining the terminal hexasaccharides of the Inaba strain have not been
shown to induce protection.
135
In 1992, a new serogroup, denominated O139 Bengal, was found to
cause cholera outbreaks.
136
The CPS of V. cholerae O139 has a very
complex repeating unit
137
composed of a two units of the rare deoxysugar
3,6-dideoxy-L-xylohexose (colitose) and a 4,6-cyclic phosphate on the
galactose moiety.
The polysaccharide was split from the LPS anchor and was conjugated
to recombinant diphtheria toxin mutant. The conjugates elicit IgG and
IgM anti-PS antibodies with vibriocidal activity to strains VcO139.
138
The
synthesis of the tetrasaccharide fragment was reported almost simul-
taneously by Oscarsson
139
and Kovac.
140
4 Hospital-acquired infections
There are no vaccines against bacteria such as Staphylococcus aureus,
Escherichia coli, Pseudomonas aeruginosa, Clostridium dicile and Acine-
tobacter baumannii, which together are responsible for the majority of
nosocomial
infections, ranging from septicemia to pneumonia and
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