Application of reverse vaccinology for the identification of epitope candidates from Rickettsia rickettsii

Rocky mountain spotted fever is a severe disease caused by Rickettsia rickettsii that frequently causes the death of the patients. As there are not effective vaccines for this disease, we employed reverse vaccinology to find epitope candidates useful for vaccine development. To apply this bioinformatics, we used the following online software: ProPred1, RANKPEP, and HLA binding, to evaluate 143 amino acid sequences in the genome of Rickettsia rickettsii (NC_009882 Sheila Smith). This strategy allowed us to identify 19 epitope sequences with affinity to HLA I alleles: A0201, A24; HLA-B: B3501, B3901

Application of reverse vaccinology for the identification of epitope candidates from Rickettsia rickettsii

643-647Rocky mountain spotted fever is a severe disease caused by Rickettsia rickettsii that frequently causes the death of the patients. As there are not effective vaccines for this disease, we employed reverse vaccinology to find epitope candidates useful for vaccine development. To apply this bioinformatics, we used the following online software: ProPred1, RANKPEP, and HLA binding, to evaluate 143 amino acid sequences in the genome of Rickettsia rickettsii (NC_009882 Sheila Smith). This strategy allowed us to identify 19 epitope sequences with affinity to HLA I alleles: A0201, A24; HLA-B: B3501, B3901

Eco-bio-social determinants for house infestation by non-domiciliated Triatoma dimidiata in the Yucatan peninsula, Mexico

Background Chagas disease is a vector-borne disease of major importance in the Americas. Disease prevention is mostly limited to vector control. Integrated interventions targeting ecological, biological and social determinants of vector-borne diseases are increasingly used for improved control. Methodology/principal findings We investigated key factors associated with transient house infestation by T. dimidiata in rural villages in Yucatan, Mexico, using a mixed modeling approach based on initial null-hypothesis testing followed by multimodel inference and averaging on data from 308 houses from three villages. We found that the presence of dogs, chickens and potential refuges, such as rock piles, in the peridomicile as well as the proximity of houses to vegetation at the periphery of the village and to public light sources are major risk factors for infestation. These factors explain most of the intra-village variations in infestation. Conclusions/significance These results underline a process of infestation distinct from that of domiciliated triatomines and may be used for risk stratification of houses for both vector surveillance and control. Combined integrated vector interventions, informed by an Ecohealth perspective, should aim at targeting several of these factors to effectively reduce infestation and provide sustainable vector control

Disentangling Trypanosoma cruzi transmission cycle dynamics through the identification of blood meal sources of natural populations of Triatoma dimidiata in Yucatan, Mexico

Background In the Yucatan Peninsula, Mexico, Triatoma dimidiata is the main vector of Trypanosoma cruzi, the causative agent of Chagas disease. Little effort has been made to identify blood meal sources of T. dimidiata in natural conditions in this region, although this provides key information to disentangle T. cruzi transmission cycles and dynamics and guide the development of more effective control strategies. We identified the blood meals of a large sample of T. dimidiata bugs collected in different ecotopes simultaneously with the assessment of bug infection with T. cruzi, to disentangle the dynamics of T. cruzi transmission in the region. Methods A sample of 248 T. dimidiata bugs collected in three rural villages and in the sylvatic habitat surrounding these villages was used. DNA from each bug midgut was extracted and bug infection with T. cruzi was assessed by PCR. For blood meal identification, we used a molecular assay based on cloning and sequencing following PCR amplification with vertebrate universal primers, and allowing the detection of multiple blood meals in a single bug. Results Overall, 28.7% of the bugs were infected with T. cruzi, with no statistical difference between bugs from the villages or from sylvatic ecotopes. Sixteen vertebrate species including domestic, synanthropic and sylvatic animals, were identified as blood meal sources for T. dimidiata. Human, dog and cow were the three main species identified, in bugs collected in the villages as well as in sylvatic ecotopes. Importantly, dog was highlighted as the main blood meal source after human. Dog was also the most frequently identified animal together with human within single bugs, and tended to be associated with the infection of the bugs. Conclusions Dog, human and cow were identified as the main mammals involved in the connection of sylvatic and domestic transmission cycles in the Yucatan Peninsula, Mexico. Dog appeared as the most important animal in the transmission pathway of T. cruzi to humans, but other domestic and synanthropic animals, which most were previously reported as important hosts of T. cruzi in the region, were evidenced and should be taken into account as part of integrated control strategies aimed at disrupting parasite transmission

Non-randomized controlled trial of the long-term efficacy of an Ecohealth intervention against Chagas disease in Yucatan, Mexico

Non-domiciliated intrusive triatomine vectors are responsible for a low but significant transmission of Trypanosoma cruzi to humans. Their control is a challenge as insecticide spraying is of limited usefulness, and alternative strategies need to be developed for a sustainable control. We performed a non-randomized controlled trial of an Ecohealth intervention based on window insect screens and community participation to reduce house infestation by Triatoma dimidiata in two rural villages in Yucatan, Mexico. Efficacy of the intervention was measured over a three years follow-up period and entomological indicators showed that the proportion of triatomines found inside houses was significantly reduced in houses with insect screens, which effectively kept more bugs on the outside of houses. Using a previously developed model linking entomological data to the prevalence of infection in human, we predicted that the intervention would lead to a 32% reduction in yearly incidence and in the prevalence of T. cruzi infection. The cost for the coverage of all the windows of a house was of comparable magnitude to what families currently spend on various domestic insecticide, and most screens were still in good conditions after three years. In conclusion, the Ecohealth approach proposed here is effective for the long-term and sustainable control of intrusive T. dimidiata vectors in the Yucatan peninsula, Mexico. This strategy may also be easily adapted to other intrusive triatomine species as well as other regions/countries with comparable eco-epidemiological settings, and would be an excellent component of a larger integrated program for the control of a variety of other vector-borne diseases, bringing additional benefits to the communities. Our results should encourage a further scaling-up of our implementation strategy in additional villages in the region

A novel multi-epitope recombinant protein elicits an antigen-specific CD8+ T cells response in Trypanosoma cruzi-infected mice

About 6.5 million people worldwide are afflicted by Chagas disease, which is caused by the protozoan parasite Trypanosoma cruzi. The development of a therapeutic vaccine to prevent the progression of Chagasic cardiomyopathy has been proposed as an alternative for antiparasitic chemotherapy. Bioinformatics tools can predict MHC class I CD8 + epitopes for inclusion in a single recombinant protein with the goal to develop a multivalent vaccine. We expressed a novel recombinant protein Tc24-C4.10E harboring ten nonameric CD8 + epitopes and using Tc24-C4 protein as scaffold to evaluate the therapeutic effect in acute T. cruzi infection. T. cruzi-infected mice were immunized with Tc24-C4.10E or Tc24-C4 in a 50-day model of acute infection. Tc24-C4.10E-treated mice showed a decreased parasitemia compared to the Tc24-C4 (non-adjuvant) immunized mice or control group. Moreover, Tc24-C4.10E induced a higher stimulation index of CD8 + T cells producing IFNγ and IL-4 cytokines. These results suggest that the addition of the MHC Class I epitopes to Tc24-C4 can synergize the antigen-specific cellular immune responses, providing proof-of-concept that this approach could lead to the development of a promising vaccine candidate for Chagas disease

<i>Trypanosoma cruzi</i> vaccine candidate antigens Tc24 and TSA-1 recall memory immune response associated with HLA-A and -B supertypes in Chagasic chronic patients from Mexico

<div><p><i>Trypanosoma cruzi</i> antigens TSA-1 and Tc24 have shown promise as vaccine candidates in animal studies. We evaluated here the recall immune response these antigens induce in Chagasic patients, as a first step to test their immunogenicity in humans. We evaluated the <i>in vitro</i> cellular immune response after stimulation with recombinant TSA-1 (rTSA-1) or recombinant Tc24 (rTc24) in mononuclear cells of asymptomatic Chagasic chronic patients (n = 20) compared to healthy volunteers (n = 19) from Yucatan, Mexico. Proliferation assays, intracellular cytokine staining, cytometric bead arrays, and memory T cell immunophenotyping were performed by flow cytometry. Peripheral blood mononuclear cells (PBMC) from Chagasic patients showed significant proliferation after stimulation with rTc24 and presented a phenotype of T effector memory cells (CD45RA^-CCR7^-). These cells also produced IFN-γ and, to a lesser extent IL10, after stimulation with rTSA-1 and rTc24 proteins. Overall, both antigens recalled a broad immune response in some Chagasic patients, confirming that their immune system had been primed against these antigens during natural infection. Analysis of HLA-A and HLA-B allele diversity by PCR-sequencing indicated that HLA-A03 and HLA-B07 were the most frequent supertypes in this Mexican population. Also, there was a significant difference in the frequency of HLA-A01 and HLA-A02 supertypes between Chagasic patients and controls, while the other alleles were evenly distributed. Some aspects of the immune response, such as antigen-induced IFN-γ production by CD4⁺ and CD8⁺ T cells and CD8⁺ proliferation, showed significant association with specific HLA-A supertypes, depending on the antigen considered. In conclusion, our results confirm the ability of both TSA-1 and Tc24 recombinant proteins to recall an immune response induced by the native antigens during natural infection in at least some patients. Our data support the further development of these antigens as therapeutic vaccine against Chagas disease.</p></div

Phenotyping of CD4⁺ T memory cells.

<p>PBMC cells from seronegative controls (open circles) and Chagasic patients (black circles) were stimulated with rTc24, and phenotyped as T effector memory (T_EM), T central memory (T_CM) or T naïve (T_NAIVE) cells. Horizontal black lines indicate the mean of the group. *Indicates significant differences between seronegative and Chagasic patients (P <0.05, <i>t</i> test for parametric distribution or U Mann-Whitney for non-parametric distribution). Numbers in parenthesis indicate the sample size for each group.</p