Transfer of a non-human primate (NHP) in vitro functional assay for the early evaluation of TB vaccine candidates and the associated immune response
Lead Research Organisation:
University of Oxford
Department Name: The Jenner Institute
Abstract
Tuberculosis (TB) remains a serious global health threat and the only currently available vaccine, BCG, is inadequate. A more effective vaccine is urgently needed. However, as it is unclear which measures of immunity indicate protection, new vaccine candidates are currently tested in animal models such as mice, cattle and non-human primates (NHPs). NHPs are considered particularly relevant as they develop the most human-like form of TB, and the use of NHPs in the field is increasing. Animals are vaccinated and then infected with the causative agent of TB, Mycobacterium tuberculosis (M.tb), to test whether the vaccine is protective. This procedure is classified as Moderate in severity, meaning that the animals are likely to experience "short term moderate pain, suffering or distress or long-lasting mild pain, suffering or distress... or moderate impairment of the well-being or general condition". As disease progresses, animals may experience loss of body weight, fever and respiratory distress and if left untreated will eventually die of pulmonary insufficiency; necessitating humane euthanasia.
For the past 6 years, Dr Tanner has led the development of an in vitro, or "test tube", assay which measures control of M.tb (or other bacteria from the same family as a surrogate) by blood or cells from a vaccinated animal or person, rather than infecting the animal or person themselves. This downgrades the severity of vaccine testing in animals considerably, falling under the 'refinement' category of the 3Rs. It also allows the testing of multiple conditions or immune responses in a set of cells from a single group of animals, and allows early down-selection of vaccine candidates going forward to testing, thereby reducing the numbers of animals required. In the longer-term, this work aims to demonstrate that the assay is a meaningful measure of protection, allowing bridging to the use of human samples (as comparison with efficacy in humans to prove this is not logistically or ethically possible). Ability to use human cells could largely replace the use of animals in TB vaccine efficacy testing.
The primary aim of this project is to successfully transfer the NHP MGIT assay to two major laboratories in the field of NHP TB vaccine testing: Public Health England (PHE) and the Biomedical Primate Research Centre (BPRC) in the Netherlands. These laboratories use ~100-150 macaques in M.tb challenge experiments each year with capacity increasing, and implementation of the MGIT assay could drastically reduce the requirement for this procedure. The transfer will involve four phases: standardisation (ensuring that all laboratories are performing the assay in the same way), harmonisation (ensuring that results from the same samples are concordant between replicates within a laboratory and between laboratories), validation (ensuring that results are biologically meaningful compared to measures of protection following in vivo infection), and finally an exploratory phase to investigate the underlying mechanisms of immunity. Stored samples from studies previously conducted at PHE and BPRC have been allocated for this project, meaning that no further animal experiments will be necessary. By successfully transferring the assay, these groups will be able to implement it into their future vaccine studies, having considerable local impact. Furthermore, the project will yield data demonstrating proof-of-concept that the MGIT assay is reproducible and transferable, thus increasing interest from additional TB research groups worldwide. Evidence that this assay correlates strongly with protection from in vivo M.tb infection will further confirm biological validity and give confidence to scientists and vaccine developers.
For the past 6 years, Dr Tanner has led the development of an in vitro, or "test tube", assay which measures control of M.tb (or other bacteria from the same family as a surrogate) by blood or cells from a vaccinated animal or person, rather than infecting the animal or person themselves. This downgrades the severity of vaccine testing in animals considerably, falling under the 'refinement' category of the 3Rs. It also allows the testing of multiple conditions or immune responses in a set of cells from a single group of animals, and allows early down-selection of vaccine candidates going forward to testing, thereby reducing the numbers of animals required. In the longer-term, this work aims to demonstrate that the assay is a meaningful measure of protection, allowing bridging to the use of human samples (as comparison with efficacy in humans to prove this is not logistically or ethically possible). Ability to use human cells could largely replace the use of animals in TB vaccine efficacy testing.
The primary aim of this project is to successfully transfer the NHP MGIT assay to two major laboratories in the field of NHP TB vaccine testing: Public Health England (PHE) and the Biomedical Primate Research Centre (BPRC) in the Netherlands. These laboratories use ~100-150 macaques in M.tb challenge experiments each year with capacity increasing, and implementation of the MGIT assay could drastically reduce the requirement for this procedure. The transfer will involve four phases: standardisation (ensuring that all laboratories are performing the assay in the same way), harmonisation (ensuring that results from the same samples are concordant between replicates within a laboratory and between laboratories), validation (ensuring that results are biologically meaningful compared to measures of protection following in vivo infection), and finally an exploratory phase to investigate the underlying mechanisms of immunity. Stored samples from studies previously conducted at PHE and BPRC have been allocated for this project, meaning that no further animal experiments will be necessary. By successfully transferring the assay, these groups will be able to implement it into their future vaccine studies, having considerable local impact. Furthermore, the project will yield data demonstrating proof-of-concept that the MGIT assay is reproducible and transferable, thus increasing interest from additional TB research groups worldwide. Evidence that this assay correlates strongly with protection from in vivo M.tb infection will further confirm biological validity and give confidence to scientists and vaccine developers.
Technical Summary
Tuberculosis (TB) remains a major global health threat, and the current vaccine (BCG) is inadequate. An improved vaccine is urgently needed, but in the absence of a validated alternative, candidate vaccines are currently tested in animal models such as mice, guinea pigs and non-human primates (NHPs). Animals are infected with pathogenic Mycobacterium tuberculosis (M.tb) following vaccination to determine efficacy; a procedure of Moderate Severity. As disease progresses, animals may experience loss of body weight, fever and respiratory distress and if left untreated will eventually die of pulmonary insufficiency; necessitating humane euthanasia. Dr Tanner has worked extensively on the development of an in vitro assay (the MGIT assay) as a correlate of protection, which may offer an alternative to in vivo M.tb infection and ultimately replace the use of animals in vaccine testing. NHPs are the most appropriate model to biologically validate the assay by comparing outcomes with measures of in vivo protection, allowing vaccine developers using this, and other preclinical models, to refine vaccine testing by replacing the infection stage. Rather, blood samples are taken from vaccinated animals and cells infected in vitro to measure vaccine efficacy. This project aims to transfer the NHP MGIT assay to two major end-user laboratories (Public Health England and the Biomedical Primate Research Centre) for use in their ongoing and future vaccine studies. Although preclinical testing may remain a regulatory requirement for progression to clinical trials, the early down-selection or gating of promising candidates using this assay will considerably reduce the numbers of animals challenged. In the longer-term, this work will offer the biological validation necessary to bridge to the use of human samples (as comparison with in vivo efficacy in humans is not logistically or ethically possible), which could largely replace the use of animals in TB vaccine efficacy testing.
Planned Impact
Infection of NHPs with virulent M.tb for vaccine testing is classified as 'Moderate' in severity by the Home Office and raises ethical issues regarding the infection procedure, disease symptoms and humane end-points. As disease progresses, animals may experience loss of body weight, fever and respiratory distress and if left untreated will eventually die of pulmonary insufficiency; necessitating humane euthanasia. At the two end-user institutes (PHE and BPRC), ~100-150 macaques are used in M.tb challenge experiments each year with capacity increasing. To our knowledge, at least 4 other groups are routinely using NHPs in TB vaccine research, increasing this value to ~400 animals per year. To gain a more accurate estimate, the search terms "Macaque, tuberculosis, vaccine" were entered into PubMed with date filters 2015-2016 and 2014-2015, returning 16 and 19 hits respectively; 3 were excluded as review or non-relevant articles in each case. From 2015-2016 and 2014-2015, the mean numbers of animals used per publication were 19 and 21, giving totals of ~250 and ~350 respectively. With only a fraction of research published, these figures are an underestimate. Furthermore, numbers are set to increase with reagent availability and a trend toward bigger group sizes, and the Gates Foundation recently promoting the use of NHPs as the 'gatekeeper' for progression of TB vaccine candidates to clinical trials.
This project is concerned with the transfer of an NHP in vitro 'MGIT' assay to the two end-user laboratories.
1) Short-term impact:
- Refining the process of testing TB vaccine candidates in NHP models by using the MGIT assay in place of Moderate Severity in vivo infection with pathogenic M.tb.
- Reducing the number of NHPs used in TB vaccine testing and associated immunology studies, as the MGIT assay allows:
a) Testing of multiple conditions (e.g. different clinical isolates/immunological mechanisms) using cells from a single group, rather than requiring multiple groups of animals.
b) Down-selection or 'gating' or vaccine candidates at an early stage of development such that far fewer go forward to in vivo efficacy testing.
Although preclinical testing may remain a regulatory requirement for progression to clinical trials, early down-selection of promising candidates will considerably reduce the numbers of animals challenged. Based on the proportion of vaccine candidates showing significant levels of protection in our mouse studies (~20%), we anticipate a reduction of 80% in the number of NHPs undergoing this procedure, as the MGIT assay selects out those candidates failing to induce protection. Bridging the biological validity of the NHP MGIT assay to use with other preclinical animal samples, a similar proportion of mice and guinea pigs would no longer undergo M.tb infection.
2) Long-term impact:
- To replace the use of NHPs and other animal models in TB vaccine testing by providing biological validity to the assay which can then be bridged to use in human cells (biological validity cannot be logistically achieved in humans where M.tb challenge is unethical); linking in with the NC3Rs highlight notice on the use of human tissue.
Other areas of impact include:
1) TB vaccine developers from preclinical to human trials would benefit from an additional tool for measuring protection, to either down-select vaccine candidates or measure efficacy in humans where M.tb challenge is not possible. This would also reduce the need for Cat. 3 facilities and dramatically reduce costs.
2) The MGIA would enhance the commercial private sector by providing a tool to facilitate vaccine selection, thus de-risking and accelerating TB vaccine development.
3) The global community will benefit from a lower burden of TB disease in the community if a successful vaccine is developed/treatment options improved, and the exploration phase may aid in this by contributing to an improved understanding of the critical immune mechanisms.
This project is concerned with the transfer of an NHP in vitro 'MGIT' assay to the two end-user laboratories.
1) Short-term impact:
- Refining the process of testing TB vaccine candidates in NHP models by using the MGIT assay in place of Moderate Severity in vivo infection with pathogenic M.tb.
- Reducing the number of NHPs used in TB vaccine testing and associated immunology studies, as the MGIT assay allows:
a) Testing of multiple conditions (e.g. different clinical isolates/immunological mechanisms) using cells from a single group, rather than requiring multiple groups of animals.
b) Down-selection or 'gating' or vaccine candidates at an early stage of development such that far fewer go forward to in vivo efficacy testing.
Although preclinical testing may remain a regulatory requirement for progression to clinical trials, early down-selection of promising candidates will considerably reduce the numbers of animals challenged. Based on the proportion of vaccine candidates showing significant levels of protection in our mouse studies (~20%), we anticipate a reduction of 80% in the number of NHPs undergoing this procedure, as the MGIT assay selects out those candidates failing to induce protection. Bridging the biological validity of the NHP MGIT assay to use with other preclinical animal samples, a similar proportion of mice and guinea pigs would no longer undergo M.tb infection.
2) Long-term impact:
- To replace the use of NHPs and other animal models in TB vaccine testing by providing biological validity to the assay which can then be bridged to use in human cells (biological validity cannot be logistically achieved in humans where M.tb challenge is unethical); linking in with the NC3Rs highlight notice on the use of human tissue.
Other areas of impact include:
1) TB vaccine developers from preclinical to human trials would benefit from an additional tool for measuring protection, to either down-select vaccine candidates or measure efficacy in humans where M.tb challenge is not possible. This would also reduce the need for Cat. 3 facilities and dramatically reduce costs.
2) The MGIA would enhance the commercial private sector by providing a tool to facilitate vaccine selection, thus de-risking and accelerating TB vaccine development.
3) The global community will benefit from a lower burden of TB disease in the community if a successful vaccine is developed/treatment options improved, and the exploration phase may aid in this by contributing to an improved understanding of the critical immune mechanisms.
