Recombinant Leishmania Hsp90 and Hsp70 are recognized by sera from visceral leishmaniasis patients but not Chagas' disease patients

Systems biology of autophagy in leishmanial infection and its diverse role in precision medicine

Autophagy is a contentious issue in leishmaniasis and is emerging as a promising therapeutic regimen. Published research on the impact of autophagic regulation on Leishmania survival is inconclusive, despite numerous pieces of evidence that Leishmania spp. triggers autophagy in a variety of cell types. The mechanistic approach is poorly understood in the Leishmania parasite as autophagy is significant in both Leishmania and the host. Herein, this review discusses the autophagy proteins that are being investigated as potential therapeutic targets, the connection between autophagy and lipid metabolism, and microRNAs that regulate autophagy and lipid metabolism. It also highlights the use of systems biology to develop novel autophagy-dependent therapeutics for leishmaniasis by utilizing artificial intelligence (AI), machine learning (ML), mathematical modeling, network analysis, and other computational methods. Additionally, we have shown many databases for autophagy and metabolism in Leishmania parasites that suggest potential therapeutic targets for intricate signaling in the autophagy system. In a nutshell, the detailed understanding of the dynamics of autophagy in conjunction with lipids and miRNAs unfolds larger dimensions for future research.

Comparative evaluation of recombinant HSP70 (N & C-terminal) fragments in the detection of equine trypanosomosis

Trypanosomosis (Surra) is an economically important disease caused by Trypanosoma evansi which is an extracellular parasite present in the plasma, tissues and other body fluids of a wide range of hosts including domesticated animals. Currently, serological reports are based on detection of antibodies by ELISA using whole cell lysate (WCL) antigen, which has a limitation of persistence of anti-trypanosomal antibodies after successful treatment of the disease. Moreover, it has some ethical issues also like requirement of mice for in vivo maintenance of parasite for preparing the antigen. Therefore, in the present study, an attempt was made to evaluate the in vitro production of recombinant heat shock protein 70 (HSP70) for detection of antibodies in experimentally infected ponies. The amino acid sequence analysis of HSP70 revealed that N-terminal region of the protein was highly conserved while the C-terminal region was most divergent. The four different regions of HSP70 protein viz. HSP-1, HSP-2, HSP-3 and HSP-4 were cloned and expressed, among which HSP-1 (N-terminal region) & HSP-2 (C-terminal region) were truncated while HSP-3 & HSP-4 were complete C-terminal proteins. The recombinant fragments were probed with sequentially pooled experimental serum samples where antibodies were detected in these fragments from 10(th) day post infection till the termination of the experiment. Further, these recombinant fragments were also comparatively evaluated with WCL antigen in ELISA using experimental as well as field serum samples. It was observed that after successful treatment of infected ponies, there was a sharp fall in antibodies (within 90 days) when tested with recombinant HSP's fragments, while antibodies persisted even after 469 days when tested against WCL antigen. The sensitivity and specificity of all HSP70 fragments were also estimated from field serum samples with reference to WCL antigen ELISA. The HSP-1 showed minimum sensitivity (41.03%) among all the recombinant fragments. Among the C-terminal fragments, maximum sensitivity was observed with the HSP-2 (61.54%) while minimum was observed with HSP-4 (48.72%). The specificity increases for recombinant fragments from N-terminal to C-terminal region of protein and maximum specificity was observed with HSP-4 fragment (91.3%).

Production and preliminary evaluation of Trypanosoma evansi HSP70 for antibody detection in Equids

The present immuno-diagnostic method using soluble antigens from whole cell lysate antigen for trypanosomosis have certain inherent problems like lack of standardized and reproducible antigens, as well as ethical issues due to in vivo production, that could be alleviated by in vitro production. In the present study we have identified heat shock protein 70 (HSP70) from T. evansi proteome. The nucleotide sequence of T. evansi HSP70 was 2116 bp, which encodes 690 amino acid residues. The phylogenetic analysis of T. evansi HSP70 showed that T. evansi occurred within Trypanosoma clade and is most closely related to T. brucei brucei and T. brucei gambiense, whereas T. congolense HSP70 laid in separate clade. The two partial HSP70 sequences (HSP-1 from N-terminal region and HSP-2 from C-terminal region) were expressed and evaluated as diagnostic antigens using experimentally infected equine serum samples. Both recombinant proteins detected antibody in immunoblot using serum samples from experimental infected donkeys with T. evansi. Recombinant HSP-2 showed comparable antibody response to Whole cell lysate (WCL) antigen in immunoblot and ELISA. The initial results indicated that HSP70 has potential to detect the T. evansi infection and needs further validation on large set of equine serum samples.

A member of the HSP90 family from ovine Babesia in China: molecular characterization, phylogenetic analysis and antigenicity

Heat shock protein 90 (HSP90) is a key component of the molecular chaperone complex essential for activating many signalling proteins involved in the development and progression of pathogenic cellular transformation. A Hsp90 gene (BQHsp90) was cloned and characterized from Babesia sp. BQ1 (Lintan), an ovine Babesia isolate belonging to Babesia motasi-like group, by screening a cDNA expression library and performing rapid amplification of cDNA ends. The full-length cDNA of BQHsp90 is 2399 bp with an open reading frame of 2154 bp encoding a predicted 83 kDa polypeptide with 717 amino acid residues. It shows significant homology and similar structural characteristics to Hsp90 of other apicomplex organisms. Phylogenetic analysis, based on the HSP90 amino acid sequences, showed that the Babesia genus is clearly separated from other apicomplexa genera. Five Chinese ovine Babesia isolates were divided into 2 phylogenetic clusters, namely Babesia sp. Xinjiang (previously designated a new species) cluster and B. motasi-like cluster which could be further divided into 2 subclusters (Babesia sp. BQ1 (Lintan)/Babesia sp. Tianzhu and Babesia sp. BQ1 (Ningxian)/Babesia sp. Hebei). Finally, the antigenicity of rBQHSP90 protein from prokaryotic expression was also evaluated using western blot and enzyme-linked immunosorbent assay (ELISA).

B-cell epitopes of antigenic proteins in Leishmania infantum: an in silico analysis

Serodiagnosis of visceral leishmaniasis is often hindered by cross-reactions to other parasitic diseases. Identifying specific B-cell epitopes in proteins is therefore important for immunodiagnostics, as well as for disease control by vaccines. This study aimed to identify linear and conformational B-cell epitopes and to evaluate the secondary structure of antigen proteins in Leishmania infantum using in silico analysis. Linear epitopes were predicted using the Immune Epitope Database and Analysis Resource (IEDB), BepiPred and BcePred programs. The conformational B-cell epitopes were identified using the CBTOPE server. The combination of the predictions using IEDB, BepiPred and BcePred generated 148 linear epitopes from the calpain-like cysteine peptidase (CP), thiol-dependent reductase 1 (TDR1) and HSP70 proteins. In total, 164 conformational epitopes were predicted, mostly located in the linear epitope region. The predicted epitopes are located in α helix and random coil regions in the thiol-dependent reductase 1 and HSP70 proteins. New linear and conformational B-cell epitopes of L. infantum proteins were identified in silico, and the prediction using various programs ensures greater accuracy of the results, as suggested by confirmation of previously identified HSP70 epitopes.

Evaluation of three recombinant Leishmania infantum antigens in human and canine visceral leishmaniasis diagnosis

Visceral leishmaniasis (VL) is a neglected disease and is fatal if untreated. Dogs serve as reservoirs for Leishmania infantum (syn. L. chagasi) due to their susceptibility to infection and high skin parasitism. Therefore, VL control in Brazil involves the elimination of seropositive dogs, among other actions. However, the most frequently used serological tests have limitations regarding sensitivity and specificity. In this study, we have selected three Leishmania antigens (C1, C8 and C9) and have produced them as recombinant proteins using pET-28a-TEV vector and Escherichia coli BL-21 as expression system. When tested in ELISA with human samples, the C9 antigen was the one showing the most promising results, with 68% sensitivity and 78% specificity. When testing canine samples, the C1, C8 and C9 antigens showed a sensitivity range from 70% to 80% and specificity range from 60% to 90%. The C1 antigen presented higher sensitivity (80%) and the C8 antigen presented higher specificity (90%). Due to it, we decided to mix and test C1 and C8 antigens together, resulting in the C18 antigen. The mix also yielded high percentages of detected symptomatic and asymptomatic dogs however it did not improve the performance of the diagnostic. Comparison of our tests with the tests recommended by the Brazilian Ministry of Health revealed that our antigens' sensitivities and the percentage of detected asymptomatic dogs were much higher. Our results suggest that the C1, C8, C18 and C9 recombinant proteins are good antigens to diagnose canine visceral leishmaniasis and could potentially be used in screening tests. To diagnose human visceral leishmaniasis, the C9 antigen presented reasonable results, but more optimization must be performed for this antigen to provide better performance.

No stress--Hsp90 and signal transduction in Leishmania

SUMMARY Hsp90 (a.k.a. Hsp83) plays a significant role in the life cycle control of the protozoan parasite Leishmania donovani. Rather than protecting Leishmania spp. against adverse and stressful environs, Hsp90 is required for the maintenance of the motile, highly proliferative insect stage, the promastigote. However, Hsp90 is also essential for survival and proliferation of the intracellular mammalian stage, the amastigote. Moreover, recent evidence shows Hsp90 and other components of large multi-chaperone complexes as substrates of stage-specific protein phosphorylation pathways, and thus as likely effectors of the signal transduction pathways in Leishmania spp. Future efforts should be directed towards the identification of the protein kinases and the critical phosphorylation sites as targets for novel therapeutic approaches.

Towards a more precise serological diagnosis of human tegumentary leishmaniasis using Leishmania recombinant proteins

Background

Exposure to Leishmania induces a humoral immune response that can be used as a marker of parasite exposure.

Methodology/Principal Findings

Herein, ELISA was used to screen sera from patients with Tegumentary Leishmaniasis (TL) against different L. infantum-chagasi-derived recombinant proteins (rHSP70, rH2A, rH2B, rH3, rH4 and rKMP11). Among the recombinant proteins, rHSP70 and rH2A showed the best reactivity against human sera obtained from endemic areas of TL. Receiver-Operator Characteristics (ROC) curve analysis was used to identify the effectiveness of these proteins for serodiagnosis of TL. ROC curves confirmed the superior performance of rHSP70 and rH2A, in comparison to the other tested recombinant proteins. Additionally, we evaluated the specificity of the response to rHSP70 and rH2A by testing sera obtained from patients with Chagas' disease, Tuberculosis, Leprosy or Systemic Lupus Erythematosus. In this case, rHSP70 displayed an increased ability to discriminate diseases, in comparison to SLA.

Conclusion

Our results raise possibility of using rHSP70 for the serodiagnosis of TL

Identification and characterization of a novel Leishmania donovani antigen for serodiagnosis of visceral leishmaniasis

Despite several drawbacks, rK39-based rapid immunochromatographic test is widely used for the diagnosis of visceral leishmaniasis (VL) in the Indian subcontinent. There is an urgent need to develop a better antigen. In this study we separated crude soluble antigens of Leishmania donovani by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and hybridized with pool sera from pre- and post-treated VL patients, 6 months follow-up, endemic healthy (EHC), and nonendemic healthy controls (NEHC) by Western blotting. The sensitivity of enzyme-linked immunosorbent assay with identified protein was 95% (confidence interval [CI] = 89.6-98.01%), whereas the specificity for EHC, NEHC, and different disease groups were 96.3% (CI = 89.8-98.6%), 100% (CI = 95.8-100%), and 97.4% (CI = 91.02-99.3%), respectively. This specific antigen was subjected to two-dimensional gel electrophoresis and after tryptic digestion, antigen was characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Further analysis showed that it is a member of the heat shock protein family of 70 kDa, designated as BHUP1, and has great potential in the diagnosis of VL.

Characterization of novel Leishmania infantum recombinant proteins encoded by genes from five families with distinct capacities for serodiagnosis of canine and human visceral leishmaniasis

To expand the available panel of recombinant proteins that can be useful for identifying Leishmania-infected dogs and for diagnosing human visceral leishmaniasis (VL), we selected recombinant antigens from L. infantum, cDNA, and genomic libraries by using pools of serum samples from infected dogs and humans. The selected DNA fragments encoded homologs of a cytoplasmic heat-shock protein 70, a kinesin, a polyubiquitin, and two novel hypothetical proteins. Histidine-tagged recombinant proteins were produced after subcloning these DNA fragments and evaluated by using an enzyme-linked immunosorbent assays with panels of canine and human serum samples. The enzyme-linked immunosorbent assays with different recombinant proteins had different sensitivities (67.4-93.0% and 36.4-97.2%) and specificities (76.1-100% and 90.4-97.3%) when tested with serum samples from Leishmania-infected dogs and human patients with VL. Overall, no single recombinant antigen was sufficient to serodiagnosis all canine or human VL cases.

Trypanosoma carassii hsp70 increases expression of inflammatory cytokines and chemokines in macrophages of the goldfish (Carassius auratus L.)

We report on the cloning and characterization of Trypanosoma carassii 70 KDa heat shock protein (hsp70). T. carassii hsp70 was secreted/excreted into culture medium in vitro and was recognized by sera from infected fish. Recombinant hsp70 (rhsp70) activated goldfish macrophages and stimulated the production of pro-inflammatory cytokines including interferon gamma (IFNgamma), tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, (IL)-12 and chemokines CCL-1 and CXCL-8 (IL-8). T. carassii hsp70-induced cytokine expression was abrogated by pronase treatment of macrophages confirming the existence of receptor(s) on goldfish macrophage surface that recognize parasite molecule. Parasite hsp70 also up-regulated the expression inducible nitric oxide synthase (iNOS) isoforms A and B and induced a strong nitric oxide response of goldfish macrophages.

Th1-stimulatory polyproteins of soluble Leishmania donovani promastigotes ranging from 89.9 to 97.1 kDa offers long-lasting protection against experimental visceral leishmaniasis

Our earlier studies identified a fraction (F2) of Leishmania donovani soluble promastigote antigen belonging to 97.4-68 kDa for its ability to stimulate Th1-type cellular responses in cured visceral leishmaniasis (VL) patients as well as in cured hamsters. A further fractionation of F2-fraction into seven subfractions (F2.1-F2.7) and re-assessment for their immunostimulatory responses revealed that out of these, only four (F2.4-F2.7) belonging to 89.9-97.1 kDa, stimulated remarkable Th1-type cellular responses either individually or in a pooled form (P4-7). In this study these potential subfractions were further assessed for their prophylactic potential in combination with BCG against L. donovani challenge in hamsters. Optimum parasite inhibition ( approximately 99%) was obtained in hamsters vaccinated with pooled subfractions and they survived for 1 year. The protection was further supported by remarkable lymphoproliferative, IFN-gamma and IL-12 responses along with profound delayed type hypersensitivity and increased levels of Leishmania-specific IgG2 antibody as observed on days 45, 90 and 120 post-challenge suggesting that a successful subunit vaccine against VL may require multiple Th1-immunostimulatory proteins. MALDI-TOF-MS/MS analysis of these subfractions further revealed that of the 19 identified immunostimulatory proteins, Elongation factor-2, p45, Heat shock protein-70/83, Aldolase, Enolase, Triosephosphate isomerase, Disulfideisomerase and Calreticulin were the major ones in these subfractions.

The Leishmania HSP20 is antigenic during natural infections, but, as DNA vaccine, it does not protect BALB/c mice against experimental L. amazonensis infection

Protozoa of the genus Leishmania are causative agents of leishmaniasis, an important health problem in both human and veterinary medicine. Here, we describe a new heat shock protein (HSP) in Leishmania, belonging to the small HSP (sHSP) family in kinetoplastids. The protein is highly conserved in different Leishmania species, showing instead significant divergence with sHSP's from other organisms. The humoral response elicited against this protein during Leishmania infection has been investigated in natural infected humans and dogs, and in experimentally infected hamsters. Leishmania HSP20 is a prominent antigen for canine hosts; on the contrary, the protein seems to be a poor antigen for human immune system. Time-course analysis of appearance of anti-HSP20 antibodies in golden hamsters indicated that these antibodies are produced at late stages of the infection, when clinical symptoms of disease are patent. Finally, the protective efficacy of HSP20 was assessed in mice using a DNA vaccine approach prior to challenge with Leishmania amazonensis.

Distinct mitochondrial HSP70 homologues conserved in various Leishmania species suggest novel biological functions

We report the identification of two distinct homologues of the 70-kDa mitochondrial heat shock protein (mtHSP70) from Leishmania chagasi/Leishmania infantum (Lc2.1 and Lc2.2). In Leishmania species, multiple genes encoding Lc2.2 are present whilst single genes encode Lc2.1. Strikingly, genes encoding Lc2.1-like proteins are absent from Trypanosoma species. Lc2.2 is characterized by a poly-glutamine rich C-terminus, absent from Lc2.1 or mtHSP70 homologues outside the trypanosomatids. Lc2.1 displays unique substitutions within its peptide-binding domain which modify amino acids strictly conserved in cytoplasmic and mitochondrial HSP70 proteins alike. Affinity purified antibodies recognize mainly a single protein in extracts from promastigotes/epimastigotes of various Leishmania/Trypanosoma species. Upon differentiation of Leishmania amazonensis into amastigotes a second protein (presumably Lc2.1) is induced and becomes the predominant mtHSP70 homologue expressed. Subcellular localization of these proteins was investigated and ratified a distribution throughout the mitochondrial matrix. Our results imply novel mtHSP70 functions which evolved within the genus Leishmania.

Proteomic approach for identification and characterization of novel immunostimulatory proteins from soluble antigens of Leishmania donovani promastigotes

Visceral leishmaniasis (VL) caused by Leishmania donovani is a major parasitic disease prevalent in endemic regions of Bihar in India. In the absence of good chemotherapeutic options, there is a need to develop an effective vaccine against VL which should be dependent on the generation of a T helper type 1 (Th1) immune response. We have shown that soluble proteins from promastigote of a new clinical isolate of L. donovani (2001) ranging from 68 to 97.4 kDa (F2 fraction), induce Th1 responses in the peripheral blood mononuclear cells of cured Leishmania patients and hamsters and also showed significant prophylactic potential. To understand the nature of F2 proteins, it was further characterized using 2-DE, MALDI-TOF and MALDI-TOF/TOF-MS. In all, 63 spots were cut from a CBB stained gel for analysis and data was retrieved for 52 spots. A total of 33 proteins were identified including six hypothetical/unknown proteins. Major immunostimulatory proteins were identified as elongation factor-2, p45, heat shock protein (HSP)70, HSP83, aldolase, enolase, triosephosphate isomerase, protein disulfideisomerase and calreticulin. This study substantiates the usefulness of proteomics in characterizing a complex protein fraction (F2) map of soluble L. donovani promastigote antigen identified as Th1 stimulatory for its potential as vaccine targets against VL.

Diagnosis of canine visceral leishmaniasis: biotechnological advances

Human visceral leishmaniasis (HVL) is endemic in the tropical and sub-tropical regions of Africa, Asia, the Mediterranean, Southern Europe and South and Central America, with approximately 500,000 new cases reported annually. As dogs are considered to be the major reservoirs for HVL, the accurate diagnosis of disease in these animals is important. Diagnosis of canine visceral leishmaniasis (CVL) is performed mainly by direct parasitological methods that can yield false-negative results, either because of the very low number of Leishmania spp. organisms in clinical samples (bone marrow and lymph nodes) or because morphological identification is difficult. In addition, these methods are invasive. Conventional serological techniques are limited by cross-reactivity with other parasitic diseases and because several technical procedures have not been standardised. The development of polymerase chain reaction based approaches and immunoassays based on the use of recombinant antigens aimed at improving the sensitivity and specificity of CVL diagnosis is discussed.

Leishmania chagasi T-cell antigens identified through a double library screen

Control of human visceral leishmaniasis in regions where it is endemic is hampered in part by limited accessibility to medical care and emerging drug resistance. There is no available protective vaccine. Leishmania spp. protozoa express multiple antigens recognized by the vertebrate immune system. Since there is not one immunodominant epitope recognized by most hosts, strategies must be developed to optimize selection of antigens for prevention and immunodiagnosis. For this reason, we generated a cDNA library from the intracellular amastigote form of Leishmania chagasi, the cause of South American visceral leishmaniasis. We employed a two-step expression screen of the library to systematically identify T-cell antigens and T-dependent B-cell antigens. The first step was aimed at identifying the largest possible number of clones producing an epitope-containing polypeptide by screening with a pool of sera from Brazilians with documented visceral leishmaniasis. After removal of clones encoding heat shock proteins, positive clones underwent a second-step screen for their ability to cause proliferation and gamma interferon responses in T cells from immune mice. Six unique clones were selected from the second screen for further analysis. The corresponding antigens were derived from glutamine synthetase, a transitional endoplasmic reticulum ATPase, elongation factor 1gamma, kinesin K39, repetitive protein A2, and a hypothetical conserved protein. Humans naturally infected with L. chagasi mounted both cellular and antibody responses to these proteins. Preparations containing multiple antigens may be optimal for immunodiagnosis and protective vaccines.

Bioinformatic identification of tandem repeat antigens of the Leishmania donovani complex

With large amounts of parasite gene sequence available, additional bioinformatic tools to screen these sequences for identifying genes encoding antigens are needed. Proteins containing tandem repeat (TR) domains are often B-cell antigens, and antibody responses toward TR domains of the proteins are dominant in human infected with certain parasites. We hypothesized that antigens of serological significance could be identified with a search for TR domains. Here we show the result of bioinformatic screening of the gene sequence database of the parasitic protozoan Leishmania infantum. Of 8,191 genes scanned, 64 genes contained TR domains. Of the 64 genes, 22 encoded previously characterized antigens; the remaining 42 genes were previously uncharacterized. By using sera from Sudanese visceral leishmaniasis patients, we confirmed that the TR domains of LinJ11.0070, LinJ25.1100, LinJ27.0400, and LinJ29.0110, which were from the 42 uncharacterized proteins, are also antigenic. The results suggest the validity of this approach for identifying leishmanial antigens of serological significance.

Fungal heat-shock proteins in human disease

Heat-shock proteins (hsps) have been identified as molecular chaperones conserved between microbes and man and grouped by their molecular mass and high degree of amino acid homology. This article reviews the major hsps of Saccharomyces cerevisiae, their interactions with trehalose, the effect of fermentation and the role of the heat-shock factor. Information derived from this model, as well as from Neurospora crassa and Achlya ambisexualis, helps in understanding the importance of hsps in the pathogenic fungi, Candida albicans, Cryptococcus neoformans, Aspergillus spp., Histoplasma capsulatum, Paracoccidioides brasiliensis, Trichophyton rubrum, Phycomyces blakesleeanus, Fusarium oxysporum, Coccidioides immitis and Pneumocystis jiroveci. This has been matched with proteomic and genomic information examining hsp expression in response to noxious stimuli. Fungal hsp90 has been identified as a target for immunotherapy by a genetically recombinant antibody. The concept of combining this antibody fragment with an antifungal drug for treating life-threatening fungal infection and the potential interactions with human and microbial hsp90 and nitric oxide is discussed.

A new Paracoccidioides brasiliensis 70-kDa heat shock protein reacts with sera from paracoccidioidomycosis patients

A cDNA coding for a new member of the 70-kDa heat shock proteins (HSP70) family from the dimorphic and pathogenic fungus, Paracoccidioides brasiliensis, was cloned and characterized. The cDNA-deduced sequence coded for 655 amino acid residues and showed 95% identity to a previously described P. brasiliensis hsp70 gene. Cytoplasmic and typical nuclear localization signals, which indicate induction upon stress, were identified in the deduced peptide. The complete hsp70 cDNA coding region was cloned into a pGEX 4T-3 plasmid and expressed in Escherichia coli as a glutathione-S-transferase-tagged fusion protein. The recombinant protein reacted with a rabbit polyclonal antibody against HSP70. Western immunoblot experiments demonstrated that sera from paracoccidioidomycosis patients recognized the purified recombinant protein, suggesting an immunological role for this protein in the infectious process. The antigenicity analysis of rHSP70 detected three internal peptides that could act as activators of T-cell proliferation.

Cloning and characterization of the Leishmania (Viannia) braziliensis Hsp70 gene. Diagnostic use of the C-terminal fragment rLb70(513-663)

Cross-reactions between Leishmania braziliensis and Trypanosoma cruzi caused by common antigenic determinants hinder the specific diagnosis of cutaneous and mucocutaneous leishmaniasis (CL and MCL). Therefore, the usefulness of the 70-kDa heat shock protein (Hsp70) from L. braziliensis for differential serodiagnosis was investigated. The single-copy gene encoding Hsp70, consisting of 663 amino acids, was isolated from a genomic DNA library. The antigenicity data show that Hsp70 is an immunodominant antigen highly recognized (84%) by sera of patients with CL and MCL and to a lesser extent by chagasic patients (18.75%). Antigenic mapping of the 5 overlapping fragments into which the protein was split showed that the main antigenic determinants are located in the carboxy-terminal end. The linear antigenic determinants that show cross-reactions with chagasic sera are located in the fragment rLb70(352-518). The carboxy-terminal fragment rLb70(513-663) presents 70% sensitivity and 100% specificity, so it could be a potential candidate for specific serodiagnosis of CL and MCL caused by L. braziliensis.

Schistosoma mansoni heat shock protein 70 elicits an early humoral immune response in S. mansoni infected baboons

A study was undertaken to search for DNA recombinant Schistosoma mansoni proteins responsible for eliciting an antibody response from the host at a very early phase after infection. A S. mansoni adult worm cDNA expression library was screened using pooled sera from baboons with four weeks of infection. Based on their specific reactivity with the S. mansoni infected sera and no reactivity when tested against the pre-infection sera from the same baboons, four clones were selected for further studies. Sequence analysis revealed that they were homologous to the S. mansoni heat shock protein 70 (hsp70). The insert sizes of the four selected clones varied from 1150 to 2006 bp. The preliminary characterization for antibody reactivity against a panel of baboon sera showed that the longest clone was the most reactive, eight out of eight acute and three out of four chronic sera reacting positively to this clone. The shortest clone was the least reactive. Our results suggest that the S. mansoni hsp70 elicits an early and strong antibody response in baboons and that antibodies to this protein can be detected in chronically infected animals. Therefore S. mansoni hsp70 may be a valid target for immunodiagnosis. However further studies are needed to identify the portion of the hsp70 that best fits the requirements for a valuable diagnostic antigen.

Dual role of the Leishmania major ribosomal protein S3a homologue in regulation of T- and B-cell activation

We have recently characterized a novel Leishmania major gene encoding a polypeptide of 30 kDa that was homologous to mammalian ribosomal protein S3a and was named LmS3a-related protein (LmS3arp). The protein was found to be expressed by all the Leishmania species so far examined (L. infantum, L. amazonensis, and L. mexicana). In the present study we have extended our approach to the analysis of LmS3arp activity on T- and B-cell functions in a murine model. The results presented in this report show that LmS3arp plays a dual role in the regulation of T- and B-cell reactivity. Indeed, we found that injection of the LmS3arp recombinant protein (rLmS3arp) into BALB/c mice induces preferential activation of B cells, as shown by the following criteria: (i) increased expression of CD69 molecules on immunoglobulin M (IgM)-secreting spleen cells, (ii) a considerable increase of IgM-secreting B cells, and (iii) elevated levels of IgM antibodies in the sera of injected animals. Moreover, the IgM antibodies are not specific to the Leishmania antigens but preferentially recognize heterologous antigens like myosin, thyroglobulin, DNA, and keyhole limpet hemocyanin. Furthermore, the strong polyclonal expansion of nonspecific, non-parasite-directed B-cell clones induced by rLmS3arp is concomitant with a marked inhibition of T-cell proliferation. Analysis of cytokine production revealed a significant downregulation of gamma interferon, interleukin-2 (IL-2), and IL-12 secretion. Taken together, our data suggest that rLmS3arp, through direct or indirect action toward B and T cells and cytokine secretion, could participate in the immunoregulatory processes that play a role in the balance of the Th1 and Th2 immune response.

Molecular and immunological characterisation of the glucose regulated protein 78 of Leishmania donovani(1)

To identify novel potential Leishmania vaccine antigens, antibodies from patients with visceral leishmaniasis (VL) were used to isolate clones from a cDNA expression library of L. donovani amastigotes. Glucose Regulated Protein (GRP78), a member of the 70 kDa heat-shock protein family was identified and characterised. The GRP78 gene was localised to chromosome 15 in L. donovani, L. major, and L. mexicana by pulse-field gel electrophoresis. The Leishmania GRP78 protein contain a carboxy-terminal endoplasmic reticulum retention signal sequence (MDDL) as does the Trypanosoma cruzi GRP78. Immunofluorescence using antibodies to the recombinant DNA-derived GRP78 protein showed staining localised to reticular material throughout the cytoplasm and in the perinuclear region of promastigotes, suggesting that the protein is localised in the endoplasmic reticulum. The protective efficacy of GRP78 was assessed in mice vaccine experiments. A GRP78 DNA vaccine primed for an immune response that protected C57Bl/6 and C3H/He mice against infection with L. major. Similarly vaccination with a recombinant form of GRP78 purified from Escherichia coli and administered with Freund's as adjuvant induced protective immunity in C57Bl/6 mice.

Inducible resistance to oxidant stress in the protozoan Leishmania chagasi

Leishmania sp. protozoa are introduced into a mammalian skin by a sandfly vector, whereupon they encounter increased temperature and toxic oxidants generated during phagocytosis. We studied the effects of 37 degrees C "heat shock" or sublethal menadione, which generates superoxide and hydrogen peroxide, on Leishmania chagasi virulence. Both heat and menadione caused parasites to become more resistant to H(2)O(2)-mediated toxicity. Peroxide resistance was also induced as promastigotes developed in culture from logarithmic to their virulent stationary phase form. Peroxide resistance was not associated with an increase in reduced thiols (trypanothione and glutathione) or increased activity of ornithine decarboxylase, which is rate-limiting in trypanothione synthesis. Membrane lipophosphoglycan increased in size as parasites developed to stationary phase but not after environmental exposures. Instead, parasites underwent a heat shock response upon exposure to heat or sublethal menadione, detected by increased levels of HSP70. Transfection of promastigotes with L. chagasi HSP70 caused a heat-inducible increase in resistance to peroxide, implying it is involved in antioxidant defense. We conclude that leishmania have redundant mechanisms for resisting toxic oxidants. Some are induced during developmental change and others are induced in response to environmental stress.

Evolutionarily conserved proteins as prominent immunogens during Leishmania infections

Many Leishmania antigens have been identified as members of conserved protein families, such as the acidic ribosomal proteins, the histones and the heat-shock proteins; despite this, they elicit specific immune responses. Furthermore, homologues of many of these antigens are immune targets in other infectious diseases and systemic autoimmune diseases. Here, Jose Mar a Requena, Carlos Alonso and Manuel Soto review this class of widely distributed antigens, which they call 'panantigens'. They also propose a model to explain the prominent immunogenicity of these antigens during Leishmania infection, on the basis of the fact that many panantigens are constituents of multicomponent complexes in the cell. The elucidation of the pathways by which Leishmania antigens are processed and presented to effector cells from the host immune system will shed light on the immunopathology of leishmaniasis and help in the development of protective immunotherapies.

Expression and subcellular localization of cpn60 protein family members in Leishmania donovani

We have identified two diverged members of the cpn60 gene family in Leishmania donovani, causative agent of Indian Kala Azar. One of the genes, cpn60.1, although actively transcribed, is not expressed to detectable levels of protein in cultured L. donovani. The other gene, cpn60.2, which, compared with cpn60.1, shows a higher sequence conservation with the hsp60 genes from Trypanosoma brucei and Trypanosoma cruzi is expressed constitutively in cultured promastigotes. The abundance of the gene product, Cpn60.2, increases by 2.5-fold under heat stress and in axenic amastigotes of L. donovani. Cpn60.2 is also found enriched in mitochondrial cell fractions and localizes to the mitochondrial matrix. We conclude that Cpn60.2 is the major mitochondrial chaperonin in Leishmania.

Cloning of a Leishmania major gene encoding for an antigen with extensive homology to ribosomal protein S3a

Following purification by affinity chromatography, a Leishmania major S-hexylglutathione- binding protein of molecular mass 66kDa was isolated. The immune serum against the parasite 66kDa polypeptide when used to screen a L. major cDNA library could identify clones encoding for the human v-fos transformation effector homologue, namely ribosomal protein S3a, and thus was named LmS3a-related protein (LmS3arp). A 1027bp cDNA fragment was found to contain the entire parasite gene encoding for a highly basic protein of 30kDa calculated molecular mass sharing homology to various ribosomal S3a proteins from different species. Using computer methods for a multiple alignment and sequence motif search, we found that LmS3arp shares a sequence homology to class theta glutathione S-transferase mainly in a segment containing critical residues involved in glutathione binding. These new findings are discussed in the light of recent published data showing multiple function(s) of the ribosomal proteins S3a.

The 90-kDa molecular chaperone family: structure, function, and clinical applications. A comprehensive review

The 90-kDa molecular chaperone family (which comprises, among other proteins, the 90-kDa heat-shock protein, hsp90 and the 94-kDa glucose-regulated protein, grp94, major molecular chaperones of the cytosol and of the endoplasmic reticulum, respectively) has become an increasingly active subject of research in the past couple of years. These ubiquitous, well-conserved proteins account for 1-2% of all cellular proteins in most cells. However, their precise function is still far from being elucidated. Their involvement in the aetiology of several autoimmune diseases, in various infections, in recognition of malignant cells, and in antigen-presentation already demonstrates the essential role they likely will play in clinical practice of the next decade. The present review summarizes our current knowledge about the cellular functions, expression, and clinical implications of the 90-kDa molecular chaperone family and some approaches for future research.

Characterization of the immunostimulatory properties of Leishmania infantum HSP70 by fusion to the Escherichia coli maltose-binding protein in normal and nu/nu BALB/c mice

Leishmania infantum HSP70 has been described as an immunodominant antigen in both humans and dogs suffering from visceral leishmaniasis. In this study, we used L. infantum HSP70 fused to Escherichia coli maltose-binding protein (MBP), as the reporter protein, to analyze the influence of HSP70 on the immunogenicity of MBP in BALB/c mice. Plasmids were constructed to produce the three recombinant proteins used in this study, namely, MBP, L. infantum HSP70, and MBP-HSP70, which consists of MBP fused to the L. infantum HSP70 amino terminus. Immunization of BALB/c mice with the MBP-HSP70 fusion protein elicited humoral and cellular responses against MBP that were higher by an order of magnitude than those elicited by immunization with MBP alone or with a mixture of MBP and HSP70. Covalent linkage of MBP to HSP70 was essential for eliciting a strong anti-MBP immune response. Cytokine secretion and immunoglobulin G isotype analyses indicated that immunization with the MBP-HSP70 fusion protein preferentially induces a Th1 immune response. Immunization of athymic nu/nu mice with the MBP-HSP70 fusion protein unexpectedly gave rise to an anti-MBP humoral response showing features of a T-cell-dependent response. Thus, we present evidence that L. infantum HSP70 demonstrates an adjuvant effect in the immune response against a covalently linked reporter protein.

Multicomponent chimeric antigen for serodiagnosis of canine visceral leishmaniasis

In this work, we describe the assembly of a synthetic gene coding for several antigenic determinants found in different Leishmania infantum antigens. Selected epitopes were derived from the ribosomal proteins LiP2a, LiP2b, and LiP0 and from the histone H2A. The resulting gene was overexpressed in Escherichia coli either as a fusion protein (with the vector pMAL-c2) or alone (with the vector pQE). In both cases, high-level bacterial production of the recombinant protein was achieved and the products were found to be stable. Enzyme-linked immunosorbent assay (ELISA) and Western blotting experiments confirmed that the corresponding epitopes are present in the engineered protein. Finally, a serological evaluation of this multiple-epitope protein by Falcon assay screening test-ELISA revealed a sensitivity of 79 to 93% and a specificity of 96 to 100% in diagnosis of canine visceral leishmaniasis, indicating that this protein represents a valuable tool for serodiagnosis.

Response to heterologous leishmanins in cutaneous leishmaniasis in Nigeria--discovery of a new focus

A pilot study was undertaken to preliminary illustrate the leishmanin skin test (LST) positivity to distinct antigen preparations (derived from promastigote of either Leishmania major or L. amazonensis, or pooled L. mexicana, L. amazonensis and L. guyanensis) in cutaneous leishmaniasis (CL) patients and healthy subjects living in two endemic foci in Nigeria. The study was designed to provide insights into whether cross-species leishmanin, such as that prepared from New World Leishmania could be useful to detect cases of Old World leishmanial infection and to compare the results with LST using L. major-derived leishmanin. The overall LST positivity in individuals from Keana tested with the cross-species leishmanin was 28.7% (27/94), while the positivity rate in the subjects from Kanana tested with the same leishmanin was 54.5% (6/11). Lower positivity values were obtained when L. major (12.5%; 11/88) or L. amazonensis (15.8%; 9/57) was tested as antigen in grossly comparable populations. Moreover, the pooled leishmanin identified most of the subjects (13/14; 92.9%) with active or healed CL, and the maximum reaction sizes were found among positive subjects in this group. No healthy controls (10 total) showed specific DTH response. The LST was useful for assessing the prevalence of subclinical infection and for measuring CL transmission over time. We report for the first time the occurrence of CL in Kanana village of Langtang South local government area of Plateau State.

Mapping of the linear antigenic determinants of the Leishmania infantum hsp70 recognized by leishmaniasis sera

Mapping of antigenic determinants of the Leishmania infantum Hsp70 was studied by analysis of the reactivity of sera from dogs with natural visceral leishmaniasis against a collection of peptides representing overlapping sequences of the Hsp70. Despite the considerable variation in the immune response among individuals three immunodominant regions were revealed encompassing residues 241 to 260 (region I), 435 to 469 (region II) and from amino acid 601 to the carboxyl-terminal end of the protein (region II. Since anti-peptide H17 antibodies purified from a pool of leishmaniasis sera recognized the L. infantum Hsp70 and since they did not react with the homologous Hsp70s from other trypanosomatids, such as Trypanosoma cruzi, Trypanosoma rangeli and Leishmania panamensis, it was concluded that peptide H17 (region II contains an immunodominant B cell species-specific epitope. Our data indicate, however, that the complete recombinant L infantum Hsp70 protein cannot be used as a disease-specific tool for serodiagnosis since it is also recognized by the sera from patients with Chagas' disease.

During canine leishmaniasis a protein belonging to the 83-kDa heat-shock protein family elicits a strong humoral response

By screening of a Leishmania infantum expression library with the serum from a dog affected with visceral leishmaniasis, a cDNA clone with sequence homology to the Hsp83 gene family was isolated. From analysis of the genomic distribution of the cDNA sequence, it was estimated that the L. infantum genome contains 7 Hsp83 genes tandemly organized. The full-length coding region of the Hsp83 gene located at the 5'-end of the cluster was determined. The deduced amino acid sequence of the L. infantum Hsp83 shows a high level of sequence identity with members of the Hsp83's protein family from other eukaryotic organisms. The complete protein (LiHsp83) and 4 subfragments (LiA1, LiB1, LiC1 and LiD1) were expressed in Escherichia coli as recombinant proteins and used as target antigens in FAST-ELISA assays against a collection of sera from dogs with visceral leishmaniasis. Ninety percent of the sera recognized the recombinant LiHsp83, indicating that L. infantum Hsp83 is a potent immunogen during canine leishmaniasis. Serological analysis of the recombinant subfragments identified the LiB1 subfragment, from amino acid 156 to 283, as the immunodominant region of the protein. This region, which is the less evolutionary conserved region of the protein, was recognized by 88% of the visceral leishmaniasis sera. The results suggest that L. infantum Hsp83 and particular protein subfragments may be useful in serodiagnostic assays for canine leishmaniasis.

During canine viscero-cutaneous leishmaniasis the anti-Hsp70 antibodies are specifically elicited by the parasite protein

A Leishmania infantum cDNA library was screened with sera from dogs with viscero-cutaneous leishmaniasis. Sequence analysis of a positive clone isolated from the library revealed that it coded for the carboxyl-terminal region of a member of the 70-kDa heat-shock protein family. The full-length sequence of the L. infantum hsp70 gene was determined after isolation of genomic clones. This protein shows a high degree of sequence conservation with the homologous protein from other organisms. To test its antigenicity a recombinant Hsp70 protein fused to the maltose-binding protein was produced in Escherichia coli using the expression vector pMAL-cRI. By FAST-ELISA assays it was observed that while the complete recombinant protein was recognized by 100% of the sera, the 20 carboxyl-terminal amino acids of the protein were only recognized by 30% of those sera. Thus, although a B-cell epitope must be present within the carboxyl terminal end of the protein other antigenic determinant(s) must reside out of this region. The analysis of the cross-reactivity with mouse Hsp70 by Western blotting strongly suggests that the anti-Hsp70 antibodies generated by infection with L. infantum are directed at specific determinants of the L. infantum Hsp70. Thus, our results indicate that anti-Hsp70 autoantibodies are not induced during Leishmania infection.

Heat shock proteins as immunological carriers and vaccines

HSPs are among the major targets of the immune response to bacterial, fungal and parasitic pathogens. The antigenic nature of HSPs is emphasized by evidence that mammals are capable of recognizing multiple B- and T cell epitopes in these proteins. The powerful immunological features of HSPs have led to their experimental use as immunomodulators and as subunit vaccine candidates. Mycobacterial hsp70 and hsp60 have been found to be excellent immunological carriers of molecules against which an immune response is desired; in the absence of adjuvants, the HSPs can stimulate strong and long-lasting immune responses against molecules which have been covalently attached to the HSPs. When used as subunit vaccines, HSPs derived from a variety of bacterial and fungal pathogens have been found to stimulate protective immunity in animal models. These studies suggest that HSPs might be used as immunomodulators or subunit vaccines against infectious disease in man.

Immune responses of leishmaniasis patients to heat shock proteins of Leishmania species and humans

The course of human infection with Leishmania braziliensis is variable, ranging from self-healing infection to chronic disease. It is therefore a useful system in which to study immunoregulatory aspects of leishmaniasis, including the effects of parasite antigens on host responses. In the present study, we report on the cloning of, expression of, and comparative analyses of patient immune response to two different L. braziliensis genes homologous to the genes for the eukaryotic 83- and 70-kDa heat shock proteins. rLbhsp83 contains a potent T-cell epitope(s) which stimulated peripheral blood mononuclear cells (PBMC) from all L. braziliensis-infected individuals to proliferate and to produce interleukin-2 (IL-2) gamma interferon, and tumor necrosis factor alpha. The elicitation of IL-4 and IL-10 mRNAs was found to differ depending on the portion of the rLbhsp83 used to stimulate PBMC. rLbhsp83a, which represents the nearly full-length protein, stimulated IL-10 but not IL-4 mRNA. In contrast, a approximately 43-kDa protein representing the C-terminal region of Lbhsp83 stimulated the production of IL-4 but not IL-10 mRNA. rLbhsp70 stimulated PBMC proliferation from patients with mucosal disease but, unlike rLbhsp83, did not stimulate PBMC from self-healing individuals. PBMC from mucosal patients were not stimulated by rHuhsp70 to either proliferate or produce cytokines. This suggests that the hyperresponsiveness of mucosal patient PBMC to Leishmania heat shock proteins does not involve an auto-immune phenomenon resulting from cross-reactivity with self hsp70. In general, although the cytokine profile of patient PBMC in response to both of these Leishmania heat shock proteins represents a mixed Th1-Th2 pattern, the levels of gamma interferon and IL-2 were significantly higher than those of the Th2 cytokines IL-4 and IL-10. Patients with active mucosal and cutaneous disease but not self-healing individuals had significant anti-immunoglobulin G antibody titers to both rLbhsp83 and rLbhsp70 but not to the homologous rHuhsp70. It therefore appears that differential patient immune responses to Leishmania hsp83 and hsp70 may be of particular significance in the induction of protective immune responses as well as in the development of tissue damage in cases with particularly strong hypersensitive reactions.

Lack of serological specificity of recombinant heat shock protein of Leishmania donovani

In order to identify a specific recombinant antigen of Leishmania donovani with potential use for diagnosis, a cDNA library was constructed in lambda ZAP II expression vector. On screening the cDNA library using pooled sera from Indian patients with kala azar, 20 antibody reactive clones were identified. These were subcloned into pBluescript phagemid by an in vivo excision procedure. The molecular weights of the expressed recombinant proteins varied from 15 to 70 kDa and the cDNA insert sizes varied from 0.5 kb to the largest size of approximately 2.0 kb which was designated as the E2b clone. The nucleotide sequencing revealed that 50% of the clones had sequence homology to the heat shock protein gene of L. donovani. The serological studies conducted with the kala azar positive sera and sera from healthy laboratory workers using the recombinant protein from the E2b clone and having sequence homology to Ldhsp 70, indicated that although all the kala azar sera was positive, 12 of 20 healthy individuals also showed antibodies against the recombinant hsp70, indicating that this antigen is not suitable for serological diagnosis of kala azar.

Tumour necrosis factor-alpha induces preferential expression of stress proteins in virulent promastigotes of Leishmania donovani

Intracellular replication of Leishmania donovani inside macrophages is essential for production of disease and development of the parasite. Tumour necrosis factor-alpha (TNF) plays an integral role in host response to Leishmania. The effect of TNF on expression of heat-shock proteins (Hsp) was examined in promastigotes of L. donovani. TNF treatment led to an increased expression of Hsp83, Hsp70 and Hsp65 in virulent, but not avirulent, parasites. In response to stress by H2O2 or sodium arsenite, an increased expression of Hsp60 was observed in the virulent, but not avirulent, parasites. The virulent promastigotes were found to be more resistant to the toxic effects of TNF and other stresses. The data indicated that Hsp expressed in response to stress encountered in macrophages may confer protection to parasites and play a crucial role in their survival in the mammalian host.

Hsp70 in parasites: as an inducible protective protein and as an antigen

The heat shock (HS) response is a general homeostatic mechanism that protects cells and the entire organism from the deleterious effects of environmental stresses. It has been demonstrated that heat shock proteins (HSP) play major roles in many cellular processes, and have a unique role in several areas of cell biology, from chronic degenerative diseases to immunology, from cancer research to interaction between host and parasites. This review deals with the hsp70 gene family and with its protein product, hsp70, as an antigen when pathogens infect humans. Members of HSP have been shown to be major antigens of many pathogenic organisms when they experience a major temperature shift upwards at the onset of infection and become targets for host B and T cells.

Serodiagnosis of Asian leishmaniasis with a recombinant antigen from the repetitive domain of a Leishmania kinesin

rK39 is a recombinant product of the 39 amino acid repeats found in a kinesin-like gene of visceral Leishmania spp. This and other antigens were compared for immunodiagnostic potential by enzyme-linked immunosorbent assay with sera from confirmed cases of Asian cutaneous and visceral leishmaniasis. In preliminary trials, rK39 proved superior to 2 purified Leishmania antigens, a cytosolic protein (p36) and a membrane protein (gp63), for immunodiagnosis of visceral leishmaniasis. Of the 53 visceral cases from China and Pakistan assayed, 52 were seropositive (98%) at a 10(-1) dilution with 36 ng of rK39. End point titrations of 27 highly positive samples yielded anti-rK39 antibody titres ranging from c. 10(-3) to beyond 10(-4). Antigen titrations with one positive serum further revealed that rK39 was 25-fold more sensitive than Leishmania whole cell soluble lysates. 31 cutaneous leishmaniasis cases from Turkey assayed for anti-rK39 antibody gave reactions ranging from negative or marginally positive to positive. In Brazil, all cutaneous and mucocutaneous leishmaniasis cases gave negative results in this assay.

Conservation of heat-shock proteins in Trypanosoma cruzi

Heat shock is an integral part of the life cycle of Trypanosoma cruzi. Here, Edson Rondinelli reviews the parasite's response to stress.

Immunoblotting as a valuable tool to differentiate human visceral leishmaniasis from lymphoproliferative disorders and other clinically similar diseases

Diseases presenting with splenomegaly, fever and pancytopenia require intensive differential diagnostic considerations. These diseases include lymphoproliferative and autoimmune diseases, but also chronic infections like mansonian schistosomiasis or visceral leishmaniasis (kala-azar). Diagnosis for the latter is usually performed by testing for the presence of antileishmanial antibodies using the immunofluorescence test (IFT) or the enzyme-linked immunosorbent assay (ELISA) technique. Here, we report on patients who displayed positive antileishmanial antibody titres in the IFT and/or ELISA, but did not develop kala-azar and were eventually diagnosed as having one of the non-kala-azar diseases listed above. These false-positive sera proved to be seronegative when tested on a Leishmania immunoblot. Our studies lead us to recommend the immunoblot technique as a confirmatory test in cases with doubtful IFT or ELISA antibody titres.