We have shown in a mouse model that the mixture
of anti-V.C and anti-CTB IgYs can be used to prevent
or treat cholera caused by either O1 or O139.
Administration of anti-V.C IgY alone also showed
some therapeutic effect, whereas anti-CTB IgY alone
was not so effective. These results indicate that the
elimination of the bacteria in the gut is more important
than neutralization of the toxin. This seems reason-
able. In the case of oral vaccination that has been
tried in humans, the vaccine inducing antibodies
against both bacteria and toxin is most effective [16].
Anti-V.C IgY was very effective for O139 infection
but was not very effective for O1 infection. The rea-
son for this difference is not clear. The behaviors of
toxin production and ELISA reaction were not differ-
ent between O1 and O139 cells. Furthermore, the
mice challenged with O139 died earlier than those
challenged with O1 (Fig. 2A and B), indicating that
the pathogenicity of O139 is stronger than that of O1
in this mouse model. On the banding profile of
Western blotting, however, some differences were
observed (data not shown). This time, we immunized
hens with mixed cells of O1 and O139. In order
clarify the above-mentioned phenomena, we plan toimmunize the hens with each of these cells and charac-
terize the antibodies obtained.
The therapeutic effects in the mice were similar
across the range of administration intervals, from 2h
to 8h. The mice were challenged with huge numbers
of cells (3.75×1010 CFU); this amount is speculated
to cause cholera more than 60オ of the time in humans
[17, 18]. This indicated that administration of IgY 3
or 4 times per day may be effective in humans.
In prevention studies, the occurrence of cholera
was inhibited almost completely by mixing the anti-V.
C IgY with live O1 or O139 cells. Also, the IgY
(mixture of anti-V.C and anti-CTB) demonstrated some
good effects even though it was administered 1h
before the challenge with O1 Inaba cells. It has been
reported that oral administration of IgY in humans has
good effects on S. mutance and H. pylori infection with-
out severe side effects including egg allergy [19, 20].
Therefore, we think the IgYs prepared this time can
be used for cholera in humans, too. We plan to carry
out these studies while carefully considering the dos-
age and dose interval of IgY administration, as well as
egg allergy. We think the best administrative method
is to mix them into dairy products, powdered milk,foods, water, or ORS to prevent or treat cholera in
humans, because they can supply water and nutrition
in addition to antibody activity. A large amount of IgY
can be easily prepared in dry powder form and can be
easily transferred, without reducing its activity, to a
place where a big outbreak of cholera might occur.
IgY is very simple to administer. It can be easily
given to people of all ages, from babies to the elderly,
even under serious or miserable conditions such as
those occurring after a natural disaster.
Acknowledgments. This work was supported by grants from the
Ministry of Education, Culture, Sports, Science, and Technology of
Japan.