New strides towards a simple molecular test for diagnosis of sleeping
sickness
Today experts stress that the parasitologic
tests used for diagnosis of human African
trypanosomiasis (HAT), or sleeping sickness,
have low sensitivity, and that current serologic
tests have inadequate specificity. Possible
solutions to address these challenges include
the detection of trypanosomal DNA from
a patient’s blood, urine or saliva. Using this
method would also be a significant improvement on parasitological examination. Loop-mediated
isothermal amplification (LAMP) of DNA
also represents a promising new molecular
technique that shows high sensitivity and
specificity. Target DNA is amplified under
isothermal conditions, meaning that the test
can be carried out with minimal equipment.
Positive samples are identified visually either
through the formation of a white precipitate
or through a colour reaction. LAMP can also
be used for the simultaneous analysis of large
numbers of samples, and can be performed
by staff with minimal experience in molecular
biology. This test may also be useful for
confirming cure in treatment follow-up.
During the past year, FIND has been working
with Murdoch and Obihiro Universities to
develop and evaluate HAT diagnostic tests
based on the LAMP technology. Sets of primers
that are specific to the subgenus Trypanozoon,
T.b. rhodesiense and T.b. gambiense have been
designed, and tests are being optimized using
DNA from various members of the sub-genus
Trypanozoon, with great success. The most
sensitive and specific primer sets are being
validated using samples from HAT patients.
The tests have been reproduced successfully
in laboratories in endemic countries, including
Tanzania, Uganda and Kenya. This work is
giving sufficiently promising results to support
adaptation of the LAMP technique for diagnosis
of HAT and has increased the prospects for a
commercial test being developed in 2008.
|
|
|
Scientists at both Obihiro (left) and Murdoch (right) Universities who are working with FIND to optimize reagents for HAT LAMP tests
|
|
