1
UNITED
STATES
ENVIRONMENTAL
PROTECTION
AGENCY
WASHINGTON,
D.
C.
20460
OFFICE
OF
PREVENTION,
PESTICIDES
AND
TOXIC
SUBSTANCES
MEMORANDUM
SUBJECT:
Clarification
of
Response
to
Valent
Comments
from
Memorandum
February3
2004
TO:
Mike
Mendelsohn
Regulatory
Action
Leader
Microbial
Pesticides
Branch,
Biopesticides
and
Pollution
Prevention
Division
(
7511C)

FROM:
John
L.
Kough,
Ph.
D.,
Biologist
Microbial
Pesticides
Branch,
Biopesticides
and
Pollution
Prevention
Division
(
7511C)

ACTION
REQUESTED:
The
statement
in
the
February
3,
2004
memorandumfound
below
about
the
Ft.
Meade
EPA
laboratory
validation
of
the
ELISA
method
for
detecting
Cry3Bb1
was
confusing.
This
is
intended
to
clarify
the
statement
and
further
address
the
concern
stated
in
Valent
Corporation's
comments
about
the
analytical
method
for
Cry3Bb1
not
being
able
to
distinguish
between
the
natural
and
engineered
variant.
The
implication
is
that
crops
treated
with
microbial
Bacillus
thuringiensis
based
products
expressing
the
natural
Cry3B
 ­
endotoxin
could
be
mistaken
for
genetically­
engineered
contamination
perhaps
jeopardizing
organic
certification.

The
original
statement
in
the
February
memorandum
reads
as
follows:

The
results
of
the
ELISA
assay
for
detection
of
the
Cry3Bb1
variant
protein
expressed
in
corn
indicate
that
the
test
does
detect
the
Cry3Bb1
protein
in
corn
grain
with
acceptable
variation
and
sensitivity.
However,
the
acceptance
of
the
ELISA
test
as
a
valid
analytical
method
is
contingent
on
the
further
testing
of
the
method
by
an
independent
laboratory
as
well
as
confirmation
of
the
test
by
the
EPA
laboratory
at
Ft.
Meade.
During
this
further
validation
process,
the
issue
of
specificity
of
the
reagents
for
the
Cry3Bb1
variant
protein
compared
to
other
proteins
that
may
be
present
in
commerce
needs
to
be
addressed.
2
While
the
validation
process
will
continue
with
verification
of
assay
performance
by
the
Ft.
Mead
laboratory,
the
ELISA
assay
is
accepted
as
an
analytical
method
by
the
Agency.
The
potential
cross
recognition
by
the
immunological
reagents
will
be
addressed
during
this
process.
However,
there
are
other
features
of
the
assay
procedures
that
could
lessen
the
likelihood
of
recognizing
a
microbial
source
of
Cry3Bb1

­
endotoxin.
The
microbial
B.
thuringiensis
products
are
known
to
be
rapidly
weathered
away
by
environmental
conditions
like
rain
and
UV
radiation
lessening
the
possibility
of
a
microbial
product
being
present.
In
addition,
if
a
positive
result
was
obtained
for
the
presence
of
Cry3Bb1
protein
in
an
unexpected
source,
the
test
could
be
confirmed
by
washing
the
suspect
crop
then
retesting.
Any
surface
contamination
by
residues
from
treatment
with
a
B.
thuringiensis
product
would
be
removed.
Any
subsequent
positive
finding
should
be
a
true
Cry3Bb1
detection
since
it
would
represent
an
internal
tissue
detection
which
could
be
reasonably
assumed
to
result
only
from
plant
expression
of
the
Cry3Bb1
gene.
