Interview: Professor Robert Miller
Robert Miller is an Honorary Consultant Physician for Camden Primary Care Trust, University College London Hospitals (NHS), and Reader in Clinical Infection in the Centre for Sexual Health & HIV Research, Royal Free and University College Medical School. His research interests include the epidemiology of Pneumocystis pneumonia, and herpes virus/polyoma virus infection in patients with AIDS. Here, Professor Miller explains how funds from the Dr Hadwen Trust are supporting his research to learn about human Pneumocystis infection, whilst replacing animal experiments.
1. What aspect of your research is the Dr Hadwen Trust funding? How is this directed towards the replacement of animal-based methods?
The Dr Hadwen Trust is funding a project which aims to develop a method to culture Pneumocystis jirovecii.
Pneumocystis was discovered by Chagas in Brazil 100 years ago. He mistakenly thought it was a protozoan and was part of the life cycle of the Trypanosome responsible for Chagas Disease. It is only over the last 20 years or so that there has been an increasing realisation that Pneumocystis is, in fact, a fungus and not a protozoan. Even more recently it has been appreciated that Pneumocystis species infecting different hosts are genetically distinct, albeit morphologically similar.
A big frustration in studying Pneumocystis is that the organism cannot be reliably cultured in vitro. This means that research into Pneumocystis relies on the use of animal models, for example, steroid immune-suppressed rats or severe combined immunodeficiency (SCID) mice. These models pose several problems.
Firstly, the organism actually studied in these animals is not human Pneumocystis. It is either Pneumocystis carinii (in the rat model) or Pneumocystis murina (in the mouse model). It is not possible to use these animal models to propagate and culture human Pneumocystis (Pneumocystis jirovecii).
Secondly, the animal hosts in which these experiments are carried out are artificially manipulated either by inducing immune suppression in the rat model, by giving steroids; or by using mice with congenital immune deficiency in the case of the SCID mouse.
The most robust scientific model would be one that permitted culture of human Pneumocystis in vitro, enabling direct study of the human pathogen and obviating the need for animals and extrapolation of research findings to the human infection. Once a robust culture method is developed, for example, it will be possible to study the development of novel antimicrobial agents and also to undertake antibiotic sensitivity testing for the first time.
2. What stimulated you to pursue this direction in your research?
A frustration that the existing animal models of infection did not in fact enable us to study the human infection at all.
3. In your view what are the major barriers to the replacement of animal experiments in your research field?
The major barrier to the replacement of animal experiments in human Pneumocystis infection research is down to one rate-limiting step, and that is the ability to culture the human infection in vitro. Several research groups have previously attempted to culture Pneumocystis in vitro but perhaps have been thwarted by the presumption until recently that the organism was a protozoan.
4. Do you think that the wider research community has a sufficient understanding of, and interest in, replacing animal experiments?
I think in recent years there has been an increasing understanding and awareness of the need for and value of replacing animal experiments.
5. Would additional earmarked funding for non-animal method development attract more researchers to this kind of work?
I am sure more researchers would be attracted to this kind of work should additional funds be earmarked for non-animal method development.
6. What’s next, scientifically, in the development and use of non-animal methods in your field?
Once a robust in vitro culture method is available for human Pneumocystis infection we will be able to move forward by looking at pathogen-related factors that associate with virulence and transmissibility. Additionally, we will be able to examine the concept of drug resistance, something that has been talked about a lot in the literature, based on clinical observation, but to date it has not been possible to look at the pharmacokinetics of this concept.
Selected publications
Huggett JF, Taylor MS, Kocjan G et al (2008). Development and evaluation of a real-time PCR assay for detection of Pneumocystis jirovecii DNA in bronchoalveolar lavage fluid of HIV-infected patients. Thorax 63:154-159.
Miller RF, Lindley AR, Copas A et al (2005). Genotypic variation in Pneumocystis jirovecii isolates in Britain. Thorax 60:679-682.