The 20-mer Peptide Library
Peptides are among the smallest known protein- based binding
molecules and have been shown to bind to an enormous range of
targets including other proteins, carbohydrates, lipids, small
organic molecules and a number of inorganic surface metals.
The CDx 20-residue peptide library is diverse (> 5 X 10 9
individual sequences) and peptide binders isolated from this
library can be used directly in diagnostic & therapeutic
validation strategies. Alternatively, they can be lead compounds
for the identification improved peptide and non- peptide molecules
that possess the desirable characteristics of high affinity
and selectivity.
Libraries based on non- mammalian
(shark) antibody variable domains (VNARs)
The IgNAR class of antibodies from sharks unusually lack the
associated light chain protein found in murine & human antibodies.
The IgNAR variable domains (VNARs) compensate
by displaying a more complex loop structure, with inbuilt mechanisms
to ensure loop stability. Halving the size of the active antibody-
binding component means that variable domain (VNAR)
fragments of these antibodies are easier to produce in mibcrobial
fermentation and shuld prove very well suited to commercial
scale-up. The loss of the light chain has an added advantage
in protein stability, with VNAR domains
being extremely resistant to harsh treatments that denature
other antibody fragments, such as high temperature and pressure
and chemical treatments. This makes them ideal candidates as
the “front end” for types of environmental and biowarfare
(BW) biosensors exposed to harsh conditions.
In vivo Affinity Maturation
Technology (InCellution)
- Evolves targets within an optimal native environment
to provide functionally relevant therapeutic or diagnostic
products for use in humans & animals
- Evolves targets that are either difficult or can’t
be evolved using existing in vitro evolution technologies
- Proprietary scheme and individual components; technology
is difficult to duplicate and or reverse engineer
- Complements existing evolution technologies
- Less expensive than animal based systems
- Currently developing two main components of the system
(mutation & display)
- Suitable for:
- Hormones
- Transcription factors
- DNA & RNAzymes
- Antibodies
- Antibody-like molecules
- Enzymes
- Receptors
Chlamydia Program
A new antigen panel is being developed to enable the easy
and accurate detection of chlamydial infections in patient
serum. Chlamydia is a major infectious agent in humans, causing
diseases such as infertility, pelvic inflammatory disease,
trachoma, bronchitis, pneumonia, chronic obstructive pulmonary
disease and has been strongly linked to heart disease. Currently
available tests are inadequate, particularly for C. pneumoniae.
The new serum- based tests will be able to detect both acute
and chronic infections caused by either C. trachomatis
or C. pneumoniae.
CDx scientists are identifying novel chlamydial antigens
associated with both acute and chronic or persistent chlamydial
infections. These novel antigens are then formulated and used
in assays with patient sera.
Rapid Microbial Genotyping
Understanding the population structures and patterns of
dissemination of infectious agents
provides essential ammunition to those entrusted with infectious
disease diagnosis, public health
assurance, infection control & biodefense.
Comparative microbial genomics has revolutionized understanding
of microbial population biology, evolution and molecular biology.
CDx researchers have exploited this to develop microbial genotyping
approaches that are based upon the efficient use of genetic
polymorphisms defined by the rapidly expanding databases of
comparative microbial genomic data.
Central to our approach is the computerised analyses of
comparative genetic data to identify minimal sets of polymorphisms
for predefined levels of genotyping resolution. This program
takes comparative gene sequence data as input and provides
as output, sets of single nucleotide polymorphisms (SNPs)
with a known level of discriminatory power.
Our SNP-based genotyping can easily be combined with simultaneous
assays for the presence of clinically relevant mobile genes
using Real Time PCR. This technology enables point-of-care
procedures that very rapidly and cheaply provide both epidemiological
fingerprints and a direct indication of virulence and resistance
phenotypes.
The CDx Microbial Genotyping group has reduced to practice,
molecular typing methods based on sets of polymorphisms identified
using these novel bioinformatic methods. The technology platform
used is real-time PCR. This is because it enables the interrogation
of genetic polymorphisms in a single step, and real-time PCR
devices are rapidly becoming ubiquitous in clinical and public
health microbiology laboratories.
Solid Phase Amplification
and Capture
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SPA (Solid Phase Amplification) is a patented process for
generating amplified nucleic acids attached to an immobile
solid phase such as the base of a microplate, a microarray
or a disposable microdevice.
SPA involves the use of one amplification primer covalently
attached to a solid support - in this case, the wall
of a microtitre well. Another amplification primer is
in solution and carries a detection tag, e.g. fluorescein.
After addition of the DNA sample, which can be as simple
as blood spot on filter paper, the reaction is cycled
to allow amplification of DNA.
Amplified DNA is synthesised as double-stranded DNA
with one end covalently attached to the well and the
other carrying a detection tag.
Following amplification the plate is washed using an
automated plate washer and amplified DNA is detected
and quantified by either direct measurement of the detection
tag or using an indirect colorimetric assay. The plate
is then read in a standard ELISA reader. A similar process
could be carried out on a microarray.
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SNAAC (Sequential Nucleic Acid Amplification
and Capture) is another patented method similar to SPA
but based on an immobilised hybridisation capture oligonucleotide
that captures solution phase amplified DNA in a single
step.
SNAAC is very similar to the SPA assay in terms of
simplicity except that it involves the use of a solid
phase-bound hybridisation capture probe that is complementary
to the internal portion of the amplified product. The
capture probe is designed so that it will not participate
in the amplification reaction. After addition of the
sample to the well, amplification is carried out in
solution, with one of the primers carrying a detection
tag, until the last cycle of amplification when the
cycling program allows a longer annealing step which
allows the product to be immobilised by the covalently
attached capture probe. After washing the plate using
an automated plate washer captured DNA is detected and
quantified using a standard ELISA reader.
Commercial application is especially amenable to:
- High density chips
Useful for Pharmacogenetics studies that require analysis
of many SNPs on a limited number of samples.
- Mini arrays in microwells (96
or 384 well plates)
A likely platform of choice for diagnostics where
there is generally a need to analyse a limited number
of SNPs or microbial pathogen sequences on a very
large number of samples.
- Microdevices
DNA amplification and detection microdevices (point
of care nucleic acid testing disposables) are currently
being developed by many groups. The amplification
of DNA on specific spots or strips on a disposable
microdevice is likely to be of great benefit for these
devices.
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