Vaccination in murine schistosomiasis with adult worm-derived antigens: variables influencing protection in outbred mice

Development of the Sm14/GLA-SE Schistosomiasis Vaccine Candidate: An Open, Non-Placebo-Controlled, Standardized-Dose Immunization Phase Ib Clinical Trial Targeting Healthy Young Women

We report the successful closure of Phase I clinical trials, comprising Phases Ia and Ib, of the vaccine candidate against human schistosomiasis: the Schistosoma mansoni 14 kDa fatty acid-binding protein (Sm14) + glucopyranosyl lipid A in squalene emulsion (GLA-SE). Shown here are the results of Phase Ib, an open, non-placebo-controlled, standardized-dose immunization trial involving 10 healthy 18-49-year-old women. Fifty micrograms of the Sm14 protein plus 10 µg GLA-SE per dose was given intramuscularly thrice at 30-day intervals. Participants were assessed clinically, biochemically, and immunologically for up to 120 days. In preambular experiments involving vaccinated pregnant female rabbits, we did not find any toxicological features in either the offspring or mothers, and the vaccine induced adaptive immunity in the animals. In women, no adverse events were observed, and vaccination induced high titers of anti-Sm14 serum IgG antibody production. Vaccination also elicited robust cytokine responses, with increased TNFα, IFNγ, and IL-2 profiles in all vaccinees on days 90 and 120. The completion of Phase I clinical trials, which were performed to the highest standards set by Good Clinical Research Practice (GCP) standards, and preclinical data in pregnant rabbits enabled the vaccine candidate to proceed to Phase II clinical trials in endemic areas.

Current Status of the Sm14/GLA-SE Schistosomiasis Vaccine: Overcoming Barriers and Paradigms towards the First Anti-Parasitic Human(itarian) Vaccine

Schistosomiasis, a disease historically associated with poverty, lack of sanitation and social inequality, is a chronic, debilitating parasitic infection, affecting hundreds of millions of people in endemic countries. Although chemotherapy is capable of reducing morbidity in humans, rapid re-infection demonstrates that the impact of drug treatment on transmission control or disease elimination is marginal. In addition, despite more than two decades of well-executed control activities based on large-scale chemotherapy, the disease is expanding in many areas including Brazil. The development of the Sm14/GLA-SE schistosomiasis vaccine is an emblematic, open knowledge innovation that has successfully completed phase I and phase IIa clinical trials, with Phase II/III trials underway in the African continent, to be followed by further trials in Brazil. The discovery and experimental phases of the development of this vaccine gathered a robust collection of data that strongly supports the ongoing clinical phase. This paper reviews the development of the Sm14 vaccine, formulated with glucopyranosyl lipid A (GLA-SE), from the initial experimental developments to clinical trials including the current status of phase II studies.

Development of the Brazilian Anti Schistosomiasis Vaccine Based on the Recombinant Fatty Acid Binding Protein Sm14 Plus GLA-SE Adjuvant

Data herein reported and discussed refer to vaccination with the recombinant fatty acid binding protein (FABP) family member of the schistosomes, called Sm14. This antigen was discovered and developed under a Brazilian platform led by the Oswaldo Cruz Foundation, from the Health Ministry in Brazil, and was assessed for safety and immunogenicity in healthy volunteers. This paper reviews past and recent outcomes of developmental phases of the Sm14-based anti schistosomiasis vaccine addressed to, ultimately, impact transmission of the second most prevalent parasitic endemic disease worldwide.

Preliminary analysis of Sm14 in distinct fractions of Schistosoma mansoni adult worm extract

In previous studies it was shown that the recombinant molecule, r-Sm14, induces high levels of protection against Schistosoma mansoni infection in two outbred animal models and immune crossprotection against infection by Fasciola hepatica in Swiss outbred mice. r-Sm14 was derived from a living worm extract, called SE, and is being developed as the molecular basis of an anti-helminth bivalent vaccine against the two parasites, for medical and veterinary application. Present data refer to SDS-PAGE and Western Blotting analysis of four different preparations of S. mansoni adult worms focusing Sm14 identification. The extracts correspond to the initial fraction of the SE extraction process, containing products released by living worms (SEi); SE2, reextraction of adult worms in PBS; and SE of separated male and female adult worms. In all extracts it was possible to detect the component of 14 kDa, that was recognized by specific anti-rSm14 antibody raised in rabbits.

The effects of immunization with recombinant Sm14 (rSm14) in reducing worm burden and mortality of mice infected with Schistosoma mansoni

To investigate whether mice immunization with the recombinant form of a 14.7 KDa Schistosoma mansoni protein (rSm14) confers protection against a S. mansoni lethal challenge infection, rSm14-immunized mice were challenged with different cercarial burdens. A significant protection was detected in immunized mice challenged with 100 or 1,000 S. mansoni cercariae when compared with their controls (p< 0.004 and p< 0.01 respectively). Differently from previous report, none of the mice from the control group (not immunized and infected with 1000 cercariae) died before the 30th day post-infection. A direct correlation between the number of challenge cercariae and the precocity of mice death was found. IgM anti-rSm14 antibodies were significantly produced (p< 0.05) mainly in the groups of immunized mice infected with 500 or 1000 cercariae. IgG and IgA anti-rSm14 antibodies were not significantly detected. In Western immunoblots, all mice sera showed a specific antibody response with a 14.7 KDa antigen being reacted with particular intensity in sera from immunized mice. The results show that immunization with rSm14 reduced mice worm burden independently of the cercariae load of challenge infection. No correlation was found between serum antibodies and worm burden reduction. In relation to cercarial load and the rate and precocity of mice mortality a direct correlation was found.

Immunoreactivity of a cytokeratin-related polypeptide from adult Schistosoma mansoni

A saline extract (SE) derived from living adult Schistosoma mansoni confers high levels of resistance to challenge infection in mice and rabbits. We have carried out a number of experiments to analyse the composition of SE and to define the proteins that are rapidly released from the parasite. One of these proteins, with apparent molecular mass of 62 kDa, is recognized by polyclonal and monoclonal antibodies raised against high molecular mass cytokeratins from human epidermal cells. Immunocytochemical studies revealed a tegumental staining using the anti-cytokeratin antibody. Moreover, sera from schistosomiasis patients, as well as those from animals immunized with SE, were able to recognize this 62 kDa polypeptide as shown by immunoblot assays. These results suggest the existence of cytokeratin-containing filaments in the schistosome.