Malaria vaccine efficacy: overcoming the helminth hurdle

Epidemiological study of the association between malaria and helminth infections in Nigeria

The relationship between intestinal helminth infection and susceptibility to malaria remains unclear. We studied the relationship between these infections. Seven schools in Ilero, Nigeria referred all pupils with febrile illness to our study center for free malaria treatment during a 3-month study period. At the end, all pupils submitted a stool sample for microscopic investigation for helminth eggs. We used an unmatched case-control design to calculate the odds ratios for helminth infection in children with at least one attack of malaria (cases) and children with no malaria episodes during the study (controls). We recorded 115 malaria cases in 82 of 354 (23.2%), 16 of 736 (2.2%), and 17 of 348 (4.7%) children ages ≤ 5, 6-10, and 11-15 years old, respectively (P = 0.001). Helminth infection rate in cases was 21 of 115 (18.3%) compared with 456 of 1,327 (34.4%) in controls. Weighted odds ratio stratified by age group for helminth infection in cases versus controls was 0.50 (95% confidence interval = 0.2-0.84, P < 0.01). Ascaris and hookworm were the most common helminths detected, with prevalence rates of 14 (12.2%) and 6 (5.2%) among cases compared with 333 (25.1%) and 132 (10.0%) in controls, respectively (P = 0.001). The negative association between helminth infection and malaria may be of importance in the design of deworming programs.

Helminth/Parasite treatment of multiple sclerosis

OPINION STATEMENT

Epidemiological studies suggest that autoimmune diseases, such as multiple sclerosis (MS), are less frequent in individuals who are helminth carriers. This observation has been tested in murine models of colitis, MS, type 1 diabetes and asthma. In each case, mice colonized with helminths show protection from disease. This apparent down-modulation of inflammatory response resulting from helminth infection has triggered interest in exploring the potential clinical efficacy of controlled helminth infection in patients suffering from autoimmune diseases. To date, clinical trials using helminth therapy (Trichura suis ova [TSO] or Necator americanus larvae) in MS have been small, safety-oriented trials of short duration, attempting to reproduce and confirm epidemiological and experimental data. Thus far, no adverse events related to therapeutic helminth infection have been observed. Nonetheless, there is a clear need for caution when considering such approaches. Some preliminary clinical, magnetic resonance imaging and immunological outcomes using TSO have been encouraging. Nevertheless, results should be interpreted with caution as the number of individuals studied was small and duration of follow up limited. Longer studies, monitoring safety and objective outcome measures are necessary to assess this novel therapeutic strategy in a more definitive fashion. An alternative approach to use of live helminth infections might arise from identification of helminth-derived immunomodulatory molecules mimicking the protective effects of parasite infection, i.e. capable of altering immune responses and, therefore, the course of autoimmune diseases. Although positive results from administering parasite products in mouse models of autoimmunity have been reported, much remains to be explored before the field can move from experimental animal models to application in clinical practice. To the best of my knowledge, parasite-derived molecules have not yet been administered as treatment for any autoimmune disease in humans. At this time, it is strongly recommended that live helminth or ova parasites be administered only to individuals participating in strictly monitored, controlled clinical trials.

A research agenda for helminth diseases of humans: basic research and enabling technologies to support control and elimination of helminthiases

Successful and sustainable intervention against human helminthiases depends on optimal utilisation of available control measures and development of new tools and strategies, as well as an understanding of the evolutionary implications of prolonged intervention on parasite populations and those of their hosts and vectors. This will depend largely on updated knowledge of relevant and fundamental parasite biology. There is a need, therefore, to exploit and apply new knowledge and techniques in order to make significant and novel gains in combating helminthiases and supporting the sustainability of current and successful mass drug administration (MDA) programmes. Among the fields of basic research that are likely to yield improved control tools, the Disease Reference Group on Helminth Infections (DRG4) has identified four broad areas that stand out as central to the development of the next generation of helminth control measures: 1) parasite genetics, genomics, and functional genomics; 2) parasite immunology; 3) (vertebrate) host–parasite interactions and immunopathology; and 4) (invertebrate) host–parasite interactions and transmission biology. The DRG4 was established in 2009 by the Special Programme for Research and Training in Tropical Diseases (TDR). The Group was given the mandate to undertake a comprehensive review of recent advances in helminthiases research in order to identify notable gaps and highlight priority areas. This paper summarises recent advances and discusses challenges in the investigation of the fundamental biology of those helminth parasites under the DRG4 Group's remit according to the identified priorities, and presents a research and development agenda for basic parasite research and enabling technologies that will help support control and elimination efforts against human helminthiases.

Dormancy in mammalian malaria

This analysis principally concerns biological aspects of dormancy in mammalian malaria, with particular reference to the hypnozoite. Research is needed to reveal what happens to sporozoites of Plasmodium cynomolgi between the time of inoculation and when hypnozoites are first seen in the liver 36-40 h later. It is likely that hypnozoites of relapsing malarial parasites will prove to be directly sporozoite-derived rather than merozoite-derived. There is indirect evidence that, contrary to what is generally assumed, activation of hypnozoites might not be the only cause of recurrent Plasmodium vivax malaria. Latent stages pose a threat to success in eradicating malaria; some suggestions are therefore made for demystifying work on hypnozoites and quiescent merozoites.

Probiotic helminth administration in relapsing-remitting multiple sclerosis: a phase 1 study

BACKGROUND

Probiotic treatment strategy based on the hygiene hypothesis, such as administration of ova from the non-pathogenic helminth, Trichuris suis, (TSO) has proven safe and effective in autoimmune inflammatory bowel disease.

OBJECTIVE

To study the safety and effects of TSO in a second autoimmune disease, multiple sclerosis (MS), we conducted the phase 1 Helminth-induced Immunomodulatory Therapy (HINT 1) study.

METHODS

Five subjects with newly diagnosed, treatment-naive relapsing-remitting multiple sclerosis (RRMS) were given 2500 TSO orally every 2 weeks for 3 months in a baseline versus treatment control exploratory trial.

RESULTS

The mean number of new gadolinium-enhancing magnetic resonance imaging (MRI) lesions (n-Gd+) fell from 6.6 at baseline to 2.0 at the end of TSO administration, and 2 months after TSO was discontinued, the mean number of n-Gd+ rose to 5.8. No significant adverse effects were observed. In preliminary immunological investigations, increases in the serum level of the cytokines IL-4 and IL-10 were noted in four of the five subjects.

CONCLUSION

TSO was well tolerated in the first human study of this novel probiotic in RRMS, and favorable trends were observed in exploratory MRI and immunological assessments. Further investigations will be required to fully explore the safety, effects, and mechanism of action of this immunomodulatory treatment.