BSP Meeting Cambridge 2014

6-9th April was spent at the University of Cambridge attending the British Society for Parasitology annual meeting, including the Tryp-Leish symposium. Thanks to Mark Field (and colleagues) for organising a great meeting – his final act in Cambridge before packing up his lab and moving to the University of Dundee!

There were many great talks, but highlights included the latest findings from Federico Rojas (Keith Matthews, University of Edinburgh) on bloodstream-form T. brucei differentiation (SIF receptor, anybody?), and Lucy Glover’s talk on VEX1, a significant player in the regulation of antigenic variation in T. brucei (David Horn, University of Dundee). Mike Barrett’s CA Wright medal talk (drug resistance and modes of action) and the plenary talks by Keith Gull (trypanosome cell biology) and David Roos (apicomplexan cell biology) were also fascinating.

Finally, the meeting provided a great opportunity to talk science and catch up with friends over a beer or two in a great setting.

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Post-doctoral Research Fellow position available

A belated update:

Dr Rachel Currier joined the lab on August 19th to work on the project outlined below. Rachel has a diverse background in molecular parasitology and snake venom biology, including high-throughput approaches, gained during MSc and PhD study at the Liverpool School of Tropical Medicine.

                                                                                                                         

There is currently a vacancy for a post-doctoral research fellow in my lab – funded for three years by the Medical Research Council (further details and how to apply can be found on the LSHTM jobs site) – closing date for applications: 24th May, 2013.

The aim of the project is to characterise the determinants of human serum efficacy in Trypanosoma brucei, specifically looking at uptake, intracellular transport and activation of the lytic factor(s). This will employ a similar approach to that used to identify the efficacy determinants of the five anti-HAT drugs published in 2012 (Alsford et al, 2012; see also, Current Research and recent reviews in Parasitology and Trends in Parasitology).

The successful applicant will need a strong background in molecular and cellular biology, as well as the ability to develop novel assays to assess the function of proteins identified using our high throughput RNAi phenotyping approach. A keen interest in host-parasite interactions, and knowledge and experience of high througput genomic and proteomic approaches would also be an advantage.

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Opinion piece published in Trends in Parasitology…

Receptor mediated endocytosis for drug delivery in African trypanosomes: fulfilling Paul Ehrlich’s vision of chemotherapy
(featured on the front cover of the May 2013 edition of Trends in Parasitology)

A lot of time is spent identifying candidate drug targets and then designing inhibitors to block their function in the ‘test tube’. Unfortunately, though highly effective on the bench, many of these compounds fail when used against their target pathogen. Therefore, it’s of fundamental importance to consider how any inhibitor is to enter the target cell, whether by passive diffusion through the membrane, uptake via a membrane channel, or by receptor mediated endocytosis.

We argue that receptor-mediated endocytosis (RME) represents a robust validated route for the entry of drugs into African trypanosomes (and probably any other pathogen). Recent developments in our understanding of the uptake of suramin (Alsford et al, 2012) and human serum trypanolytic factors (Higgins et al, 2013) have shown just how effective RME is at taking up trypanocidal agents. Using these compounds, and others, as chemical probes will enable us to expand our understanding of the network of proteins underlying and driving RME. Further, this may lead to the identification of specific essential pathways that can be exploited for drug uptake and which are less vulnerable to the development of drug resistance.

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Speaking at KMCB meeting, Woods Hole MA, April 2013

The 5th Kinetoplastid Molecular Cell Biology meeting in Woods Hole MA kicks off on the 21st April, and I’m going to be speaking about some of the findings from our latest RNAi library screen.

Inhibition of Trypanosoma brucei cathepsin-L increases sensitivity to lysis by human serum.

Human serum (HS) is highly effective at killing non-human infective trypanosomes, such as T. b. brucei, T. congolense and T. vivax (though, unfortunately, T. b. gambiense and T. b. rhodesiense are unaffected, explaining their ability to cause devastating disease in humans).

From the work of several groups over the last two decades we know a huge amount about the mode of action of the HS trypanolytic factor (TLF; Vanhollebeke & Pays, 2010), as well as some of the ways that human infective African trypanosomes have evolved resistance (Stephens et al, 2012). However, although it’s known that TLF enters the parasite via the haptoglobin-haemoglobin receptor (HpHbR), the proteins that enable its transit to the lysosome are a mystery.

HS selection of the bloodstream form T. b. brucei RNAi  library, and Illumina high thoughput sequencing of the remaining RNAi fragments, has identified proteins that likely influence the transit of TLF to the trypanosome lysosome and its action therein. This has revealed the first hints of a network of proteins, beyond the HpHbR, that influences the efficacy of TLF-mediated killing of African trypanosomes.

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Review published in ‘Parasitology’…

Genetic dissection of drug resistance in trypanosomes | Full Text
Part of a special edition of Parasitology, 140(12):  Genetic and genomic approaches to understanding drug resistance in parasites (October, 2013).

Our understanding of the routes to drug resistance in trypanosomes, as well as our ability to dissect the modes of action of anti-trypanosomal drugs has massively increased with recent advances in high throughput approaches to functional genomics in Trypanosoma brucei, leading to the identification of more than 50 proteins contributing to the efficacy of the five anti-trypanosomal drugs (Alsford et al, 2012), including an aquaglyceroporin responsible for melarsoprol-pentamidine cross-resistance (Baker et al, 2012).

In this review, we summarise what’s known about drug resistance in trypanosomes, and the technology that has underpinned the most recent advances, whilst ackowledging past advances in understanding drug resistance in these parasites (for example: Maser et al, 1999; Wilkinson et al, 2008; Vincent et al, 2010). It also looks to the future, with the possiblilty that similar analyses using drugs against the related typanosomatid, Leishmania, will develop our understanding of drug resistance and the parasite factors that determine drug efficacy in this widespread group of parasites.

Understanding the parasite-intrinsic factors that influence drug efficacy highlights routes of drug uptake and activation, thereby identifying potential resistance mechanisms (and appropriate combination therapies to protect valuable drugs), as well as robust entry points into the parasite that we can exploit in the future.

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Peer review – a shifting deadline

Article peer review is an important part of our role as scientists, provided free of charge to scientific publishers, and a necessary (though not infallible) quality control on the published record.

Clearly, the vast majority of editors and pubishers appreciate the contributions of academics to this process. However, there’s increasing pressure coming from some journal editors to expedite peer review as quickly as possible – it’s unclear what impact this will have on review quailty, but it’s unlikely to be positive. The need to provide rapid reviews has come as publishers promise ever shrinking submission-to-decision times as one way to stand out in an overcrowded journal market.

Recently, I was invited to peer review an article and was given a perfectly reasonable two weeks to provide my comments. I accepted the editor’s invitation, but then nine days before the deadline I received an email saying my review was no longer required, as they’d already received sufficient comments. Fortunately, I hadn’t read the paper or started my report, and so initially wasn’t that bothered – it just gave me more time to deliver on my teaching commitments, get on with some overdue lab work, and finish two review articles of my own. But then various conversations with colleagues at LSHTM got me thinking. There are two reasons why I feel that this is a fundamentally poor way to behave (and why I won’t be accepting any invitations to review manuscripts for this journal in the future)…

1. I’d accepted the invitation and had set aside some time to read and comment on the scientific merits of the paper. It was only chance that I hadn’t started this process by the time I got the email telling me my comments were no longer required. I could just as easily have been a significant way through, meaning that my time would have been entirely wasted.

2. Delivering a peer review that is both fair and constructive for the authors, and supportive of the integrity of the scientific record, requires time and space in which to reflect on the data and interpretations presented. To rush this process does a disservice to the authors and has the potential to undermine the scientific literature; a remarkable amount of time and funding can be wasted by students and post-docs following up on results that are misrepresented in the literature or flat out wrong.

We rely on the scientific literature to a greater or lesser extent to identify the scientific questions we want to address and the hypotheses that we want to test. Therefore, it is imperative that we strive to maintain the quality of this exponentially growing resource, rather than seeking new ways to undermine it.

MRC Funding

The MRC have recently agreed to fund a three year project in the lab investigating human serum efficacy determinants in Trypanosoma brucei, specifically looking at intracellular transport and activation of the lytic factor(s). This will employ a similar approach to that used to identify the efficacy determinants of the five anti-HAT drugs published earlier this year (Alsford et al, 2012; see also Current Research).

I’ll be posting an advert soon for an experienced post-doc: someone with extensive cell and molecular biology skills, and a keen interest in host-parasite interactions. A detailed job description and person specification will be posted here and on the usual channels once I have them.

Why study African trypanosomes?

We’ve always needed to be able to justify our chosen area of research, and this is particularly the case in current times when funding is so hard to come by. This question is also pertinent given the recent successes achieved in controlling Human African Trypanosomiasis (HAT) by numerous NGOs, the WHO, and many African public health professionals and institutions. Their efforts have led to a collapse in recorded cases, a trend that has resulted in less than 7,000 incidents of HAT being reported in 2011 (Simmarro et al, 2012). These successes inspired the WHO in Africa to propose that HAT should be eliminated as a public health problem by 2015 (WHO Africa) – though this should not be confused with full elimination or eradication of HAT, and even if achieved, surveillance measures will need to be maintained.

So why do so many of us still work on Trypanosoma brucei, the African trypanosome?

One simple answer is that people are still dying from HAT. The available drugs have been in use for many years (almost 100 in the case of suramin), they are toxic with a whole collection of extremely unpleasant side effects, they are complex to adminsister (requiring prolonged use, and hospitalisation of the patient), and the incidence of treatment failures and resistance is on the rise (Barrett et al, 2011). Without treatment HAT is fatal – in weeks to months in the case of East African HAT, while West African HAT can take  months to years to cause death (Brun et al, 2010). Although, it should be noted that a recent report has shown that some individuals can become aparasitaemic, asymptomatic and present a declining serological response, even in the absence of treatment (Jamonneau et al, 2012). How widespread this apparent ‘trypanotolerance’ is within the HAT at-risk population is unknown, as is the potential for ‘reactivation’ in these individuals.

The reported case numbers are a gross underestimate of the real situation. The WHO estimates that in 2011 there were nearer to 30,000 cases (WHO Factsheet 259). This is due to a number of factors, including poor accessibility to some endemic areas, stigma associated with the disease preventing sufferers from seeking help, and misdiagnosis (symptoms are non-specific). In fact the true situation may be even worse as, due to its speed of progress, many East African HAT sufferers are simply missed (Odiit et al, 2005). Though given all this, case numbers are the lowest they’ve been for many years, and elimination, may be an achievable goal (Welburn & Maudlin, 2012), though not necessarily within the ambitious time frame set by WHO Africa.

Unfortunately, we’ve been here before. Extensive control efforts, focusing on reducing the number of tsetse flies (the vector) and reservoir animals in endemic areas, led to a massive reduction in the number of HAT cases throughout the 1960s. At this time a combination of civil conflict and complacency led to the failure of these early control efforts and HAT resurged, with the resultant epidemic reaching its peak in the mid 1990s. Hence, it is now, when case numbers are at a 50 year low, that control efforts need to be maintained, if not redoubled, for HAT elimination to be achieved; especially given the issues with the available drugs and the potential for significant civil conflict in the region, which can lead to population displacement into endemic areas (Berrang Ford, 2007; Ruiz-Postigo et al, 2012).

It’s not only humans who suffer from the ravages of this devastating disease. African trypanosomes also parasitise other mammals, including livestock and wild ungulates (antelope, wildebeest, etc), and many of these animals can act as resevoirs of human infection – the existence of so many resevoirs of HAT is just one significant obstacle among many that make control of this disease, let alone elimination, a huge challenge. So, even though HAT as a public health problem is currently declining, these parasites are still having a massive impact on livelihoods and health in Africa through their detrimental effect on livestock farming. In fact, T. brucei and the related trypansomes, T. conglense and T.vivax, have had a restrictive effect on the development of livestock farming in Africa over millennia, and this is still the case today in endemic areas. Just as for HAT, there is only a limited set of drugs available and parasite resistance to these is a serious problem (Geerts et al, 2001).

Surely, the above is reason enough to continue working on T. brucei?

The African trypanosome isn’t the only trypanosomatid to cause devastating disease. The American trypanosome, T. cruzi, causes Chagas’ disease in Central and South America, and Leishmania, a group of related trypanosomatids, causes a collection of diseases throughout the tropics and sub-tropics. Genetically, these three groups of parasites are very similar, though there are significant differences, not least of which is that T. cruzi and Leishmania are intracelllular parasites, while T. brucei is extracellular. Although T. cruzi and Leishmania are extensively studied in labs around the world, neither is as genetically tractable as T. brucei. Therefore, initial experiments in T. brucei can help to set the direction and priorities for later work in these other parasites, potentially saving a huge amount of time in the process.

Finally, the trypanosomatids (trypanosomes and Leishmania) are intrinsically interesting for the many unusual aspects of their biology, due in part to their position at the root of the eukaryotic tree of life. They provide a highly divergent comparator, giving a different perspective (for example see, Dubois et al, 2012, and Field et al, 2012) from the evolutionarily closely related group of widely studied ‘model’ organisms, such as Drosophila, C. elegans, the yeasts, Xenopus and mammals.

For all of this though, the most important reason to study the African tryanosome is that it causes a devastating disease in both humans and our livestock, the treatments for which are unsatisfactory, and whose elimination, or even eradication, we should all be striving for.

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Invited talk at Nottingham University

Thanks to Bill Wickstead for inviting me to give a talk as part of the Nottingham University School of Biology seminar series (17/10/2012). I spoke about High throughput genetic analysis in Trypanosoma brucei – deciphering trypanosome biology; an all encompassing title, but RNAi library screens access so many different elements of trypanosome biology that it’s difficult to be more specific!

It was a worthwhile trip both socially and scientifically, with the talk generating some great discussions both during and after – it was nice to find an enthusiastic (non-tryp) audience for some of our recent and not so recent findings (mostly focusing on the drug screen outputs published in Nature back in February, 2012).

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