Vaccines used in leprosy (Hansens disease) Advances in vaccines in leprosy

1. Vaccines for leprosy
A short talk - Anand

3. • ‘Vaccine' ≈ 'la vacche' ≈ cow
• Vaccines- enhances host immunity
• Are perhaps the most effective means of
controlling infectious diseases by inducing
active immunity

4. Vaccines are of 3 types-
• Live vaccines
• Killed vaccine
• Toxoids

5. Attenuated Live Vaccines
• Attenuated live organisms.
• Initiate an infection without causing any injury
or death
• Immunity little lesser than natural infection
• Lasts for several years.
• Booster doses generally not required
(exception - polio).

6. Killed vaccine
• Killed organisms
• Less immunogenic
• Protection for short periods.
• Repeated booster doses.
Toxoids
• Toxins of bacteria are detoxified and used as
vaccines.
• Antibodies neutralize the toxin, but have no
effect on organism.

7. Need for leprosy vaccine
• New case detection rate - Not decreased.
• Large number of hidden cases continues to increase
• Even after MDT, highly bacilliferous cases (BL/LL)
continue to be smear positive leading to relapses
and reactions
• Therefore, combination of MDT & immunisation for
active cases & in endemic areas –
Long term measure for eradication of leprosy.

8. Parameters for determining vaccine
efficacy
• For other vaccines, usually determined by its
ability to lower incidence of the disease.
• But, this parameter cannot be used for leprosy
because it has long IP & will require long term
trials
• Mitsuda test ---Lepromin (+)

9. • Aims of vaccine
– Immunoprophylaxis
– Immunotherapy

10. Effects of immunotherapy
Promotion of CD 4 Th 1 cells effective
antibacterial process.
Overproduction of CD 4 Th 2 cells is switched
off.
Regulatory activity of CD 8 cells is relaxed to
allow Th 1 activity
More efficient killing of viable bacilli including
persisters

11. OUTCOME
– Faster clearance of dead & viable bacilli including
persistors leads to
– Duration of treatment
-- Morbidity and mortality.
– Transmission and relapse
– Case holding and better compliance
– Clinical improvement in skin lesions
– Improved Host immunity

12. Problems with development of vaccine for
leprosy
• Long incubation period of disease.
• Paucity of animal model (Armadillo)
• Inability to culture bacteria in lab
Dasypus novemcinctus

13. CLASSIFICATION OF “CANDIDATE
VACCINES
• 1st Generation
Non Cultivable (M.leprae) Cultivable M.bacteria
• 1. Killed M leprae 1. BCG
• 2. Killed M leprae + BCG 2. BCG + M.vaccae
• 3. Acetoacetylated M leprae 3. Killed M.welchii
4. Killed ICRC
5. M.vaccae
6. M.habana
7. M gordonnae
8. M.phlei
• Second generation (In vitro/ Animal studies only)
• Subunit vaccines
• Shuttle plasmid vaccines

14. • These are vaccines under trial
• Yet to achieve the status of a vaccine

16. BCG
• Bacille Calmette Guerin in 1921
• Living bacteria derived from an attenuated
bovine strain of tubercle bacilli
• WHO recommendation - Danish 1331 strain
• The most widely used vaccine

17. Studies with BCG vaccine
• BCG was found effective against the growth of
M.leprae in foot-pads of mice
• Katoch et al (1989)– BL/LL patients treated
with MDT for 2 years and who were still
smear positive were given BCG which led to
increased bacterial killing and clearance
• But BCG vaccination is no more considered to
be a modality for immunoprophylaxis of
leprosy

18. BCG
• Indian studies -Protective efficacy ranging from
20-70%
• Almost equal to its efficacy in preventing TB
• Better protection against MBL (93%)
• Faster clearance of both live and dead bacilli as
well as faster histological and clinical clearance
• Repeat vaccination affords further protection
especially in children less than 15 years of age
• There is increased risk of type I reaction
• Indicated increased risk of tuberculoid and
indeterminate leprosy after BCG vaccination

19. Other studies
Efficacy
• Brazil - 90%
• Kenya - 81%
• Uganda - 80%
• Myanmar- 65%

20. CONVIT GARCIA

21. Convit García’s vaccine
(BCG+ Killed M.leprae)
• A Venezuelan scientist- developed a vaccine in
an attempt to fight leprosy
• In 1987, Convit added heat killed M.leprae to
the BCG vaccine
• The combined vaccine was tested worldwide,
but was not more effective than regular BCG
• A vaccine for leishmaniasis was later
developed using Convit's method

22. Convit vaccine
• Produced favourable clinical and histological
responses in both indeterminate & LL
• Few recent trials from India -shown better
lepromin conversion and faster clinical and
histological cure with the use of Convit
vaccine along with MDT compared to BCG
with MDT.

23. Acetoacetylated M leprae
• Carrier modified form of M leprae.
• Talwar et al gave acetoacetylated M.leprae to
13 LL patients. They observed lepromin
conversion in 7/13 patients
• Acetoacetylation improves interaction of
bacteria with leucocytes- in vitro studies show
improved macrophage migration.
• Immunization of contacts- it made them
lepromin positive.

24. Pathology
• Cell mediated immunity (CMI) is the dominant
host defence against M.leprae and circulating
anti-M.leprae antibodies have little role
• Lipid component of cell wall of M.leprae prevents
the recognition of bacilli by macrophages
• Tuberculoid leprosy exhibit CMI response due to
high levels of serum lipase, which removes the
lipids of the cell wall
• Delipidified cell component (DCC)
of M.leprae have been shown to activate
macrophages and kill M.leprae in vitro.

25. De-lipified cel components of
M leprae
• Defective macrophages of leprosy patients
were able to recognize the delipified cell
components as antigens.
• It led to proliferation of lymphocytes in
cultures following production of the desired
lymphokines.
• Mice vaccinated with delipified cell
components were found to control the growth
of M leprae

26. ICRC
• ICRC bacilli ( to MAC complex)
• 1979 - Cancer Research Institute Mumbai
• ICRC bacilli exhibit antigenic cross-reactivity
with M.leprae with reference to both B & T
cell antigens
• Antigens of the ICRC bacilli are also more
accessible, making the organism a stronger
immunogen

27. ICRC
• From a cultivable organism & hence cheap
• No contamination with animal products
• Induces stable immunity
• Vaccine may also act against infections caused
by these opportunistic microbes
• Rapid and significant fall in BI

28. • Advantages:-
– Enhances T cell reactivity
– Induces lepromin conversion in LL patients
– Faster clearing of M.leprae
• More data is available on its role in
immunoprophylaxis than in immunotherapy.
• Each dose contains 1 X 108 bacilli

29. Mw(M.welchii)
• A rapid growing mycobacterium is said to be a
cultivable saphrophytic soil bacillus
• Dr. G. P. Talwar, founder- director of NII,New Delhi
• Since 1998 under the trade name of ‘Leprovac’ &
is currently -‘Immuvac’
• Induce lepromin conversion in BL/LL patients
• The vaccine has been used in patients with MBL
• ICRC and Mw are similar cell antigens
Hence having similar results

30. Mw
• Antigenically similar to M.leprae and M
tuberculosis.
• Effective and tolerable
• Role in both immunotherapy and
immunoprophylaxis.
• More rapid bacterial clearance
• Earlier achievement BI negativity in patients
given M.w+ MDT compared to only MDT.

31. • Advantages:-
– Earlier release of patients from treatment
– Slow responders to MDT are benefited
– Decreased incidence of type II reactions and neuritis
• ADR:-
• Fever
• Mild injection site erythema induration(7d)
ulceration(3wks) healing (4wks) scar
• Loco-regional LAP

32. M.Vaccae
• Used in trials for immunotherapy of- TB, AD,
Psoriasis, Leishmaniasis, & Adeno Ca Lung
• To induce immunoreactivity to M leprae in the
form of lepromin conversion, in both in vivo
and in vitro studies
• Stanford et al demonstrated lepromin
conversion in humans using
BCG and killed M. vaccae

33. M.habana
• A photochromogen
• CDRI Lucknow have shown CMI response in
mice, langur & rhesus monkeys to its vaccine
• A potential candidate vaccine for both TB &
leprosy
• Protect mice against MTB, M ulcerans &
M leprae

34. 2nd generation subunit vaccine
• Advances in cloning -- identified many protein
antigens of M. leprae-- 70Kd, 65 Kd, 35 Kd, 31
Kd, 18 kd, 10 Kd
• Natural or recombinant form of these proteins
are available.
• Peptide base vaccine can elicit humoral and
CMI response.
• They are used for immunoprophylaxis,
immunotherapy, immunodiagnosis.
• Chemically synthesized by recombinant DNA
technology– free of biological contamination .
• Still in experimental stage- Not in humans

35. • Using recombinant technology, the entire
genome of M.leprae has been cloned.
• Recombinant DNA clones containing gene
coding for 5 immunogenic proteins have been
isolated using monoclonals.
• If scientists succeed in identifying the
'protective' antigen(s) from amongst these
proteins
• Clones making 'protective' antigen(s) could be
a constant source of supply for the
preparation of a vaccine.

36. HMW PP-I glycoprotein
• Fraction of sonicate of ICRC bacilli  gel
permeation HPLC  yields HMW glycoprotein
known as PP-I with molecular weight of 106 D.
• It is a strong immunogen, carrying epitopes
for B & T cells.
• Brings about lepromin conversion

37. M lepra 35 kD protein
• M lepra 35 kD protein
• Protective immunity in Guinea pigs was found
to be similar to BCG.

38. Other candidate Subunit vaccines
• M lepra 65 kD heat shock protein (hsp)
• M lepra: lsr antigen, 12 kD antigen
• M lepra groES, groEL, 70kD hsp
• M lepra 35kD + M tuberculosis 85B antigen
• M habana 65kD and 23 kd proteins

39. PLASMID EXPRESSING CYTOKINES
• Vector that expresses p35 and p40 chain of
murine IL-12 when combined with M.leprae
35Kd antigen
• Increases antigen specific production of
interferon γ
• Increased clearance of mycobacteria
compared to M.lepra 35kD vaccine alone.

40. SHUTTLE PLASMID VACCINES
• Approach has been to introduce genes coding
for protective antigens in BCG.
• Attempt to introduce several protective genes
from diverse organisms into BCG
• Simultaneouly with aim of developing
vaccines which will protect against many
disease including TB, leprosy, typhoid.

41. Advances
• October 2003 – Identification of M. leprae
antigens
• May 2005 – Completed screening of M.Leprae
for proteins strongly recognized by the human
immune system
• March 2006 – Identified 02 specific antigens
(MLO405 and ML2331) gave a significantly
greater sensitivity to PGL-1 antibody test

42. A vaccine for leprosy is being developed by American researchers
and is set for toxicology tests towards the end of 2014 and for
phase I clinical trials in human volunteers by 2015
The Guardian June 06,2014

43. PROBLEMS WITH THE CURRENT
VACCINES
1. Very few well-performed double-blind RCTs
with proper follow-up.
2. Vaccines such as Mw – 24m while MDT- 12 m
3. Bacteriological cure already 100% with MDT.
Hence No additional benefits
4. Unsatisfactory results in MBL with high BI at
onset.
5. Risk of type I reactions.
6. Observational studies overestimate the
efficacy of vaccines

44. CHALLENGES FOR NEW ANTI LEPROSY VACCINES
Complex host immunological response to
mycobacteria Eg:-quantity of mycobacterial
protein and the timing of exposure.
Testings limited mainly to animal models
For testing individual vaccines takes 9 -12 m
Limitations of the models for testing:-
 The sensitivity of mouse footpad infection
model is low
Complexity of the armadillo model
Limiting factors:-Not many new cases &
extensive infrastructure

45. Comparative Leprosy Vaccine Trial in
South India
– Double-blind, RCT prophylactic leprosy vaccine
– Compared BCG, BCG with Killed M.leprae, Mw,
ICRC with normal saline placebo.
– Study population- 2,90,000.
– Overall protective efficacy
• BCG-34.1%
• BCG with Killed M.leprae –64%
• ICRC— 65%
• Mw- 25.7%
– BCG with Killed M.leprae and ICRC vaccine were
found to be potentially more useful as
immunoprophylactic agent.

46. BCG BCG + killed M leprae ICRC Mw
Prophylactic efficacy 18-90% 50-64% 65.5% 25.7%
Therapeutic efficacy
(combined with MDT)
BI fall @ 2.4/ yr
BI-ve at end of 3.5 yrs
BI fall @
3/ yr
BI fall @
1.7/yr
BI fall @
1.7-2.72/ yr
2. BI-ve at end of 3 yrs
Type I reaction ↑ by 10% - - ↑ by 15%
Type II reaction ↓ by 30% - - ↓ by 25%

47. THE FUTURE
• BCG and ICRC Vaccine- future polyvalent
mycobacterial vaccine that might offer
protection against a wide spectrum of
mycobacterial diseases.
• Such a polyvalent mycobacterial vaccine
would reduce the number of vaccinations

49. References:
• Lepr Rev. 2004 Dec;75(4):357-66
• Bull World Health Organ1989; 67 : 389– 99.
• Indian J Lepr 1998; 70 : 369–388.
• Lancet 1996; 348: 17–24.
• Ind J Lper 2000; 72: 21–34.
• Int J Lepr Other Mycobact Dis 2001, 69: 10–13.
• Int J Lepr Other Mycobact Dis 2002; 70: 174–181.