Novel diagnostic and therapeutic approaches in tuberculosis
(Inventors:
S. E. Hasnain et al.)
Brief description:
The direct
observed treatment short course (DOTS) has been the most effective intervention
against tuberculosis taking into account the number of lives saved and
relapses avoided. However, the proportion of relapsed cases still is
alarming with several cases going undetected. Of the total cost, 5-10%
is spent on diagnosis that often lack sensitivity and can be time consuming,
leading to delay in the treatment procedure and consequently result
in increase in relapsed cases.
Treatment of
infectious and asymptomatic cases by early and accurate detection is
the best way today to intervene against tuberculosis. The bottleneck
in TB management is the proper and early detection of the disease. Understanding
its priority, one of the central goals of WHO is to ensure detection
of 70% of TB case worldwide.
Mycobacterium
tuberculosis can practically remain undetected in lungs for decades,
efficiently escaping detection by the host immune system and the drug
therapy. Only in 10% of the infected people, the number being higher
in immuno-compromised patients, TB erupts as a full-blown disease. Delay
in diagnosis of the asymptomatic patients and hence their treatment
impedes the downstream management and control of the disease. These
patients act as potential reservoir of M. tb
and spread infection in the community, unless effectively treated.
With the increasing emergence of multi drug resistant strains and co-infection
with HIV the problem is getting further compounded. Early diagnosis,
therefore, is a matter of utmost concern for TB disease management and
epidemiological investigations. Current diagnostic tools for tuberculosis
often lack sensitivity and can be time consuming. TB diagnosis largely
banks upon tuberculin skin test and staining and culture methods. The
epidemiological relevance of tuberculin test with purified protein derivative
(PPD) is questionable in areas where BCG vaccination is compulsory because
PPD is not sensitive enough to distinguish between vaccinated and infected
individual. Often the BCG vaccinated population is scored positive leading
to a wrong line of treatment. Microscopic determination of the
bacilli in the sputum samples requires high titers of bacilli (5000
– 10000 / ml) in sputum – a condition seen only in full blown tuberculosis
patients. Culture techniques can detect very low titers but are time
consuming, taking approximately 3 – 6 weeks. This necessitates development
of more promising and rapid diagnostic methods for successful TB management.
We have developed
several rapid ELISA based strategies that target these problems of TB
diagnosis, namely, a) effective avoidance of false positives where BCG
vaccinated healthy population can be differentiated from infected ones
and b) differentiation between the fresh and relapsed cases of tuberculosis.
Both the points are very important in launching a proper drug regime
to avoid recurrence of the disease and develop MDR-TB. In particular,
avoiding relapses can have important public health implications, by
reducing number of cases of TB with subsequent reduction of cost associated
with relapses. Also, since the method is ELISA based it can be performed
in any diagnostic lab. Further, it can be extended into a time-saving
high-throughput screening set-up for both diagnostic and epidemiological
investigations. In the present scenario of available detection techniques
we believe these will be of high commercial potential.
We have established
in an ELISA based study:
1. M. tb
ICDs could elicit strong B cell response and significantly distinguish
BCG-vaccinated healthy individuals from TB-patients. This observation
is highly significant as PPD, predominantly used for tuberculin skin
test for TB detection, lacks the sensitivity to distinguish between
BCG vaccinated and TB-infected populations. Also, M. tb
ICDs do not cross react with the sera of NTMs (there are more than 82
recognized species of mycobacteria that occasionally infect mammalian
hosts. These are referred to as nontuberculous mycobacteria) and non-TB
patients. These results, for the first time, highlight the potential
of M. tb ICDs as a diagnostic marker for TB and at the same time
discriminate TB from BCG as well as NTM background.
2. Rv2608 a
PPE_MPTR protein and the peptides corresponding to regions of high antigenic
index can differentiate between fresh tuberculosis and the relapsed
cases, with the latter category patients demonstrating the highest B
cell responses to the peptides. Therefore these peptides and the full
length protein, for the first time, can be used as diagnostic markers
for rapid detection of a relapsed case and instant initiation of an
appropriate drug management for the patient.
3. We have recently
shown that a member of the hypothetical PE/PPE ORF 2430c mounts a strong
B-cell response in sera of TB patients. What is more interesting about
this is the fact that the response is significantly pronounced for category
one patient (fresh infection or so called activation cases) as opposed
to the relapse case. Furthermore, this response was higher than that
generated by M.tb. HSP10 or PPD. This, therefore, provides a
strong diagnostic for active infection.
Utility:
In summary,
the diagnostic antigens identified by us will be able to detect active
infection (Rv2430c), relapse cases (Rv2608) and finally M.tb
from NTM and also BCG background. We believe this is the first time
that we have a powerful system for diagnostics which will have huge
commercial potential. Accordingly we have filed applications to protect
our IPR.
Research
publications:
Patents
filed:
Patent applications
on this invention have been filed under two different titles, namely:
(i)
Antigenic Peptides (from Rv 2608)
Patents applications : [PCT]
Search Reports
: [International]
(ii)
A method of diagnosing tuberculosis (based on using anti-ICD antibodies)
Patents applications : [PCT]
Search Reports
: [International]