Part One. X-ray crystallography has benefited from the synthetic introduction of selenium to different positions within nucleic acids by easing the solving of the phase problem. Interestingly, its addition to the 2' position of the ribose ring also significantly enhances crystal formation. This phenomenon was investigated to describe the effect of selenium-based and other 2' modifications to the ribose ring of nucleosides in solution, as well as the incorporation of the selenium-modified nucleotides into a helical structure. This work correlates the difference in conformation propensity between the selenium containing nucleosides and oligomers towards a rationale behind the enhanced crystal forming behavior. Part Two. Recombinant protein production is a critical tool in laboratories and industries, and inducing extracellular transport of these products to the culture medium shows potential for improving cases where the yields are not sufficient in quality or quantity. This review incorporates current practices and systems with future perspectives.

Downstream purification often represents the most cost-intensive step in the manufacturing of recombinant proteins. Conventional purification processes are lengthy, technically complicated, product specific and time-consuming. To address this issue, herein we develop a one step purification system that due to the nature of the non-selective secretion system and the versatility of ion-exchange membrane chromatography can be widely applied to the production of many recombinant proteins. This was achieved through the integration of the intrinsically coupled upstream, midstream and downstream processes, a connection that is rarely exploited. A bioprocess for effective production and purification of penicillin G acylase (PAC) was developed. PAC was overexpressed in a genetically engineered Escherichia coli strain, secreted into the cultivation medium, harvested, and purified in a single step by anion-exchange chromatography. The cultivation medium developed had a sufficiently low conductivity to allow direct application of the extracellular fraction to the anion-exchange chromatography medium while providing all of the required nutrients for sustaining cell growth and PAC overexpression. It was contrived with the purposes of (i) providing sufficient osmolarity and buffering capacity, (ii) minimizing ionic species to facilitate the binding of extracellular proteins to anion-exchange medium, and (iii) enhancing PAC expression level and secretion efficiency. Employing this medium recipe the specific PAC activity reached a high level of 487 U/L/OD600, with more than 90% was localized in the extracellular medium. Both, the osmotic pressure and induction conditions were found to be critical for optimal culture performance. Furthermore, formation of inclusion bodies associated with PAC overexpression tended to arrest cell growth, leading to potential cell lysis. iv At harvest, the whole non-clarified culture broth was applied directly to a tangential flow filtration anion-exchange membrane chromatography system. One-step purification of recombinant PAC was achieved based on the dual nature of membrane chromatography (i.e. microfiltration-sized pores and anion-exchange chemistry). Due to their size, cells remained in the retentate while the extracellular medium penetrated the membrane. Most contaminate proteins were captured by the anion-exchange membrane, whereas the purified PAC was collected in the filtrate. The batch time for both cultivation and purification was less than 24 h and recombinant PAC with high purity (19 U/mg), process yield (74%), and productivity (41 mg/L) was obtained.

Hepatitis B virus (HBV), which belongs to the family Hepadnaviridae, is responsible for acute and chronic hepatitis. The vaccines presently used to immunize patients against HBV are recombinant subunit vaccines consisting of viral surface antigens (S protein). However, they are expensive and their use is limited in poor countries. For that reason, HBV remains an important worldwide health problem. Of the 2 billion people who have been infected with the HBV, more than 350 million have chronic (lifelong) infections, who face increased risk of developing cirrhosis and hepatocellular carcinoma. In this study, high-level expression of recombinant Hepatitis B surface Antigen (rHBsAg), PreS2-S was achieved in the methylotrophic yeast, Pichia pastoris. For this aim, a single copy of HBV M gene (PreS2-S) was inserted at the downstream of the alcohol oxidase (AOX1) promoter of the pPICZA vector. rHBsAg protein could then be expressed intracellularly by induction with methanol. High cell density fermentation was followed by chromatographic separation to obtain pure rHBsAg. Humoral response after immunization with the purified protein was observed in mice using commercial Hepatitis B surface antigen kits. It was verified by the atomic force microscopy that rHBsAg has been produced in the desired conformation.

A platform for vaccine development has been developed at Georgia State University utilizing recombinant Salmonella typhimurium flagellin (FliC) fused to an antigen that can be overexpressed in Escherichia coli grown in a two-stage fermentation. The flagellin acts as an adjuvant to increase the immunopotency of the fused antigen. Flagellin is the ligand for Toll-like Receptor 5 (TLR5), a part of the innate immune system. Binding of the flagellin:antigen recombinant protein to TLR5 triggers a strong innate and adaptive immune response to the fused antigen leading to a potentially strong protective immunity to the antigen. Purification of the recombinant FliC fusion protein must meet rigorous criteria in order to be used as a vaccine. One of the major issues in purifying recombinant proteins expressed in a Gram-negative bacterium is the removal of endotoxin. Small amounts of endotoxin present in a vaccine can lead to serious complications, including death. Recombinant proteins are also expressed as either soluble or insoluble protein when over expressed in E. coli. Soluble proteins expressed by the bacterium are properly folded and biologically active, however removal of contaminants such as endotoxin, can be problematic. Insoluble protein is improperly folded and biologically inactive. The insoluble proteins aggregate into inclusion bodies with little or no contaminants associated with the protein, making purification easier. However, in order to restore the biological activity of the insoluble protein, it must first be solubilized and then refolded. This process is often expensive and time consuming, as there is currently no standardized method for protein refolding. In this study a purification method for the soluble protein of two FliC constructs, full-length FliC and FliC fused to a Marburg virus antigen, was evaluated for effectiveness in purification, removal of endotoxin and maintaining TLR5 activity. The proteins of interest were purified utilizing only the soluble protein containing the properly folded and biologically active recombinant protein. Utilizing methods for purification that take advantage of physical and chemical properties of the protein the recombinant proteins were purified and the level of endotoxin reduced to levels acceptable for use as a vaccine. The TLR5 activity of the soluble recombinant proteins was compared to recombinant protein that had been purified using a denaturing and refolding step. The soluble protein elicited a higher TLR5 response at a lower concentration of protein than the refolded protein. Purification of the soluble fraction also involved fewer step and less time than purification of both the soluble and insoluble protein.

African horsesickness (AHS) is one of the most deadly diseases of horses, with a mortality rate of over 90% in horses that have not been exposed to any African horsesickness virus (AHSV) serotype previously (Howell, 1960; Darpel et al., 2011). The Orbiviruses, African horsesickness virus (AHSV) and Bluetongue virus (BTV), are primarily transmitted to their mammalian hosts through certain haematophagous midge vectors (Culicoides spp.) (Erasmus, 1973). The selective cleavage of BTV and AHSV VP2 by trypsin-like serine proteases (Marchi et al., 1995) resulted in the generation of subsequent infectious sub-viral particles (ISVP) (Marchi et al., 1995; van Dijk & Huismans, 1982). It is believed that this cleavage affects the ability of the virus to infect cells of the mammalian and vector host (Darpel et al., 2011). Darpel et al (2011) identified a trypsinlike serine protease in the saliva of Culicoides sonorensis (C. sonorensis), which also cleaves the serotype determinant viral protein 2 (VP2) of BTV. And, a similar cleavage pattern was also observed by van Dijk & Huismans (1982) and Marchi et al (1995) with the use of trypsin and chymotrypsin. Manole et al (2012) recently determined the structure of a naturally occurring African horsesickness virus serotype 7 (AHSV7) strain with a truncated VP2. Upon further investigation, this strain was also shown to be more infective than the AHSV4 HS32/62 strain, since it outgrew AHSV4 in culture (Manole et al., 2012). Therefore, through proteolytic cleavage of these viral particles, the ability of the adult Culicoides to transmit the virus might be significantly increased (Dimmock, 1982; Darpel et al., 2011). Based on these findings, it is important to investigate the factors that influence the capability of arthropod-borne viruses to infect their insect vectors, mammalian hosts and their known reservoirs. In this study, we postulated that one of the vectors for AHSV, Culicoides imicola (C. imicola), has a protease similar to the 29 kDa C. sonorensis trypsin-like serine protease identified by Darpel et al (2011). Proteins in the total homogenate of C. imicola were separated on SDS-PAGE and yielded several protein bands, one of which also had a molecular mass of around 29 kDa. Furthermore, proteolytic activity was observed on a gelatin-based sodium dodecyl sulfate polyacryamide gel electrophoresis (SDS-PAGE) gel. The activity of the protein of interest was also confirmed to be a trypsin-like serine protease with the use of class-specific protease inhibitors. A recombinant trypsin-like serine protease of C. sonorensis was generated using the pColdIII bacterial expression vector. The expressed protein was partially purified with nickel ion affinity chromatography. Zymography also confirmed proteolytic activity. With the use of the protease substrates containing fluorescent tags and class specific protease inhibitors, the expressed protein was classified as a serine protease. It was also proposed that incubation of purified AHSV4 with the recombinant protease would result in the cleavage of AHSV4 VP2, resulting in similar VP2 digestion patterns as observed in BTV by Darpel et al (2011) or the truncated VP2 of AHSV7 by Manole et al (2012). BHK-21 cell cultured AHSV4 was partially purified through Caesium chloride gradient ultracentrifugation after which the virus was incubated with the recombinant protease. Since not enough virus sample was obtained, the outcome of VP2 digestion was undetermined. In the last part of this study, it was postulated that C. imicola and C. sonorensis have the same trypsin-like serine protease responsible for the cleavage of VP2 based on the protease activity visualised in the whole midge homogenate. Since the genome of C. imicola is not yet sequenced, the sequence of this likely protease is still unknown. Therefore, we attempted to identify this C. imicola protease through polymerase chain reaction (PCR) amplification. Total isolated ribonucleic acid (RNA) of C. imicola was used to synthesize complementary deoxyribonucleic acid (cDNA). The cDNA was subjected to PCR using C. sonorensis trypsin-like serine protease-based primers. An 830 bp DNA fragment was amplified. However, sequence alignment and the basic local alignment software tool (BLAST), revealed that DNA did not encode with any other known proteins or proteases. From the literature it seems that there is a correlation between the proteases in the vector and the mammalian species that succumb to AHS (Darpel et al., 2011, Wilson et al., 2009, Marchi et al., 1995). Based on the work performed in the study, a proteolytically active protein similar to the 29 kDa protein of C. sonorensis is present in C. imicola. The 29 kDa protease of C. sonorensis can also be expressed in bacteria which could aid in future investigations on how proteolytic viral modifications affect infectivity between different host species. / MSc (Biochemistry), North-West University, Potchefstroom Campus, 2014

Disposable technology has gained increasing acceptance in the biopharmaceutical industry over the last decade, and provides many advantages over conventional stainless steel equipment. Disposable rocking bioreactors (RBs) are widely employed for cultivation of recombinant mammalian and insect cell lines, although the perception of inadequate mass transfer has prevented their application to bioprocesses based on microbial platforms. In an effort to thoroughly evaluate the suitability of disposable RBs for cultivation of aerobic microorganisms, a comparative study of one-dimensional (1D) and two-dimensional (2D) disposable RBs, and the conventional stirred tank reactor (STR) was performed. The comparison involved: 1) physical characterization of oxygen mass transfer efficiency and mixing intensity, 2) batch cultivation of Escherichia coli BL21 for comparison of growth characteristics, and 3) batch cultivation of recombinant E. coli BL21 expressing a clinical therapeutic, hCD83ext (the extracytoplasmic domain of human CD83). Oxygen mass transfer (evaluated as the mass transfer coefficient, kLa) was comparable between the 1D RB and STR (approximately 150 h-1) at low working volume (WV), declining linearly with increasing WV, while kLa was highest in the 2D RB for all tested WVs, providing the maximum kLa (394 h-1) at 3 L WV. Fast mixing (t95 of 8-20 s) was observed in all three systems for water and aqueous carboxymethylcellulose (CMC) solutions. Batch growth characteristics of E. coli BL21 were similar in each system, although acetate accumulation was significant in the 1D RB. Batch production of GST-hCD83ext (glutathione S-transferase-hCD83ext fusion protein) resulted in similar soluble protein yields and inclusion body formation between bioreactors. Although cell growth and protein expression were comparable between all bioreactors, the 1D RB is not considered a suitable cultivation system for E. coli under experimental conditions given the significant acetate accumulation observed and high supplemental oxygen requirement for low cell density cultures. On the other hand, considering its formidable mass transfer capacity and overall performance in batch cultivations, the CELL-tainer® is an attractive alternative to the STR for cultivation of recombinant E. coli expressing high value therapeutic proteins.

Downstream purification often represents the most cost-intensive step in the manufacturing of recombinant proteins. Conventional purification processes are lengthy, technically complicated, product specific and time-consuming. To address this issue, herein we develop a one step purification system that due to the nature of the non-selective secretion system and the versatility of ion-exchange membrane chromatography can be widely applied to the production of many recombinant proteins. This was achieved through the integration of the intrinsically coupled upstream, midstream and downstream processes, a connection that is rarely exploited. A bioprocess for effective production and purification of penicillin G acylase (PAC) was developed. PAC was overexpressed in a genetically engineered Escherichia coli strain, secreted into the cultivation medium, harvested, and purified in a single step by anion-exchange chromatography. The cultivation medium developed had a sufficiently low conductivity to allow direct application of the extracellular fraction to the anion-exchange chromatography medium while providing all of the required nutrients for sustaining cell growth and PAC overexpression. It was contrived with the purposes of (i) providing sufficient osmolarity and buffering capacity, (ii) minimizing ionic species to facilitate the binding of extracellular proteins to anion-exchange medium, and (iii) enhancing PAC expression level and secretion efficiency. Employing this medium recipe the specific PAC activity reached a high level of 487 U/L/OD600, with more than 90% was localized in the extracellular medium. Both, the osmotic pressure and induction conditions were found to be critical for optimal culture performance. Furthermore, formation of inclusion bodies associated with PAC overexpression tended to arrest cell growth, leading to potential cell lysis. iv At harvest, the whole non-clarified culture broth was applied directly to a tangential flow filtration anion-exchange membrane chromatography system. One-step purification of recombinant PAC was achieved based on the dual nature of membrane chromatography (i.e. microfiltration-sized pores and anion-exchange chemistry). Due to their size, cells remained in the retentate while the extracellular medium penetrated the membrane. Most contaminate proteins were captured by the anion-exchange membrane, whereas the purified PAC was collected in the filtrate. The batch time for both cultivation and purification was less than 24 h and recombinant PAC with high purity (19 U/mg), process yield (74%), and productivity (41 mg/L) was obtained.

Over the past decade, plants have been used as expression hosts for the production of pharmaceutically important and commercially valuable proteins. Plants offer many advantages over other expression systems such as lower production costs, rapid scale up of production, similar post-translational modification as animals and the low likelihood of contamination with animal pathogens, microbial toxins or oncogenic sequences. However, improving recombinant protein yield remains one of the greatest challenges to molecular farming. In-Plant Activation (InPAct) is a newly developed technology that offers activatable and high-level expression of heterologous proteins in plants. InPAct vectors contain the geminivirus cis elements essential for rolling circle replication (RCR) and are arranged such that the gene of interest is only expressed in the presence of the cognate viral replication-associated protein (Rep). The expression of Rep in planta may be controlled by a tissue-specific, developmentally regulated or chemically inducible promoter such that heterologous protein accumulation can be spatially and temporally controlled. One of the challenges for the successful exploitation of InPAct technology is the control of Rep expression as even very low levels of this protein can reduce transformation efficiency, cause abnormal phenotypes and premature activation of the InPAct vector in regenerated plants. Tight regulation over transgene expression is also essential if expressing cytotoxic products. Unfortunately, many tissue-specific and inducible promoters are unsuitable for controlling expression of Rep due to low basal activity in the absence of inducer or in tissues other than the target tissue. This PhD aimed to control Rep activity through the production of single chain variable fragments (scFvs) specific to the motif III of Tobacco yellow dwarf virus (TbYDV) Rep. Due to the important role played by the conserved motif III in the RCR, it was postulated that such scFvs can be used to neutralise the activity of the low amount of Rep expressed from a “leaky” inducible promoter, thus preventing activation of the TbYDV-based InPAct vector until intentional induction. Such scFvs could also offer the potential to confer partial or complete resistance to TbYDV, and possibly heterologous viruses as motif III is conserved between geminiviruses. Studies were first undertaken to determine the levels of TbYDV Rep and TbYDV replication-associated protein A (RepA) required for optimal transgene expression from a TbYDV-based InPAct vector. Transient assays in a non-regenerable Nicotiana tabacum (NT-1) cell line were undertaken using a TbYDV-based InPAct vector containing the uidA reporter gene (encoding GUS) in combination with TbYDV Rep and RepA under the control of promoters with high (CaMV 35S) or low (Banana bunchy top virus DNA-R, BT1) activity. The replication enhancer protein of Tomato leaf curl begomovirus (ToLCV), REn, was also used in some co-bombardment experiments to examine whether RepA could be substituted by a replication enhancer from another geminivirus genus. GUS expression was observed both quantitatively and qualitatively by fluorometric and histochemical assays, respectively. GUS expression from the TbYDV-based InPAct vector was found to be greater when Rep was expected to be expressed at low levels (BT1 promoter) rather than high levels (35S promoter). GUS expression was further enhanced when Rep and RepA were co-bombarded with a low ratio of Rep to RepA. Substituting TbYDV RepA with ToLCV REn also enhanced GUS expression but more importantly highest GUS expression was observed when cells were co-transformed with expression vectors directing low levels of Rep and high levels of RepA irrespective of the level of REn. In this case, GUS expression was approximately 74-fold higher than that from a non-replicating vector. The use of different terminators, namely CaMV 35S and Nos terminators, in InPAct vectors was found to influence GUS expression. In the presence of Rep, GUS expression was greater using pInPActGUS-Nos rather than pInPActGUS-35S. The only instance of GUS expression being greater from vectors containing the 35S terminator was when comparing expression from cells transformed with Rep, RepA and REnexpressing vectors and either non-replicating vectors, p35SGS-Nos or p35SGS-35S. This difference was most likely caused by an interaction of viral replication proteins with each other and the terminators. These results indicated that (i) the level of replication associated proteins is critical to high transgene expression, (ii) the choice of terminator within the InPAct vector may affect expression levels and (iii) very low levels of Rep can activate InPAct vectors hence controlling its activity is critical. Prior to generating recombinant scFvs, a recombinant TbYDV Rep was produced in E. coli to act as a control to enable the screening for Rep-specific antibodies. A bacterial expression vector was constructed to express recombinant TbYDV Rep with an Nterminal His-tag (N-His-Rep). Despite investigating several purification techniques including Ni-NTA, anion exchange, hydrophobic interaction and size exclusion chromatography, N-His-Rep could only be partially purified using a Ni-NTA column under native conditions. Although it was not certain that this recombinant N-His-Rep had the same conformation as the native TbYDV Rep and was functional, results from an electromobility shift assay (EMSA) showed that N-His-Rep was able to interact with the TbYDV LIR and was, therefore, possibly functional. Two hybridoma cell lines from mice, immunised with a synthetic peptide containing the TbYDV Rep motif III amino acid sequence, were generated by GenScript (USA). Monoclonal antibodies secreted by the two hybridoma cell lines were first screened against denatured N-His-Rep in Western analysis. After demonstrating their ability to bind N-His-Rep, two scFvs (scFv1 and scFv2) were generated using a PCR-based approach. Whereas the variable heavy chain (VH) from both cell lines could be amplified, only the variable light chain (VL) from cell line 2 was amplified. As a result, scFv1 contained VH and VL from cell line 1, whereas scFv2 contained VH from cell line 2 and VL from cell line 1. Both scFvs were first expressed in E. coli in order to evaluate their affinity to the recombinant TbYDV N-His-Rep. The preliminary results demonstrated that both scFvs were able to bind to the denatured N-His-Rep. However, EMSAs revealed that only scFv2 was able to bind to native N-His-Rep and prevent it from interacting with the TbYDV LIR. Each scFv was cloned into plant expression vectors and co-bombarded into NT-1 cells with the TbYDV-based InPAct GUS expression vector and pBT1-Rep to examine whether the scFvs could prevent Rep from mediating RCR. Although it was expected that the addition of the scFvs would result in decreased GUS expression, GUS expression was found to slightly increase. This increase was even more pronounced when the scFvs were targeted to the cell nucleus by the inclusion of the Simian virus 40 large T antigen (SV40) nuclear localisation signal (NLS). It was postulated that the scFvs were binding to a proportion of Rep, leaving a small amount available to mediate RCR. The outcomes of this project provide evidence that very high levels of recombinant protein can theoretically be expressed using InPAct vectors with judicious selection and control of viral replication proteins. However, the question of whether the scFvs generated in this project have sufficient affinity for TbYDV Rep to prevent its activity in a stably transformed plant remains unknown. It may be that other scFvs with different combinations of VH and VL may have greater affinity for TbYDV Rep. Such scFvs, when expressed at high levels in planta, might also confer resistance to TbYDV and possibly heterologous geminiviruses.

Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2013-04-18T18:08:55Z No. of bitstreams: 1 Ana Paula Almeida de Souza Validação de proteinas...pdf: 2348379 bytes, checksum: 16135e91d8da506bd6d51b00312ae853 (MD5) / Made available in DSpace on 2013-04-18T18:08:55Z (GMT). No. of bitstreams: 1 Ana Paula Almeida de Souza Validação de proteinas...pdf: 2348379 bytes, checksum: 16135e91d8da506bd6d51b00312ae853 (MD5) Previous issue date: 2013 / Universidade Federal da Bahia. Fundação Oswaldo Cruz. Centro de Pesquisas Gonçalo Moniz / O controle das populações de flebotomíneos, a contenção das epidemias nas fases iniciais e a facilitação do diagnóstico precoce dos indivíduos parasitados são estratégias traçadas pela OMS para a vigilância e controle da leishmaniose. Neste contexto, os testes sorológicos utilizando tanto o sonicado de glândula salivar (SGS) dos flebotomíneos quanto o antígeno solúvel de Leishmania (SLA) são importantes ferramentas para o controle/diagnóstico das Leishmanioses. No entanto, os testes realizados a partir da utilização de antígenos obtidos de frações brutas, apesar de apresentarem alta sensibilidade, alguns destes antígenos apresentam reação cruzada com epítopos compartilhados por outros patógenos/vetores. Além disso, o preparo dos antígenos não tem adequada reprodutibilidade devido a grande dificuldade de obtenção e/ou padronização destes. No presente trabalho, objetivamos identificar biomarcadores para a vigilância e o controle das Leishmanioses, utilizando proteínas recombinantes da saliva dos flebotomíneos como biomarcadores de exposição ao vetor e proteínas recombinantes da Leishmania para obtenção de um diagnóstico sorológico mais preciso para a Leishmaniose Tegumentar humana. Numa primeira etapa, foram realizados testes imunoenzimáticos contra as proteínas recombinante da saliva do vetor L. longipalpis (rLJM11 e rLJM17) para estimar a positividade anti-saliva num pequeno número de soros de crianças de uma área endêmica para Leishmaniose Visceral. Foi observado que os soros que reconhecem o SGS do L. longipalpis também reconhecem em diferentes proporções as proteínas rLJM17 e rLJM11. Ademais, as proteína recombinantes foram capazes de detectar a soroconversão anti-saliva de soros de uma segunda área endêmica para LV, havendo aumento no reconhecimento quando utilizadas as duas proteínas recombinantes de forma combinada. Além disso, a análise das curvas ROC evidenciou o desempenho superior da combinação das proteínas rLJM17 + rLJM11. Estes dados foram confirmados com a avaliação das proteínas frente um grande painel de 1.077 amostras de soro de indivíduos de uma outra área endêmica para LV. Nesta etapa, nossos resultados indicam que as proteínas rLJM11+rLJM17 representam uma ferramenta epidemiológica promissora que pode auxiliar na implementação de medidas de controle contra a Leishmaniose Visceral. Numa segunda etapa, testes imunoenzimáticos foram realizados contra uma série de proteínas recombinantes da Leishmania (HSP70, H2A, H2B, H3, H4 e KMP11) a fim de selecionarmos proteínas antigênicas contra soros de pacientes com Leishmaniose Cutânea (LC) e Leishmaniose Mucosa (LM) e que apresentassem elevada especificidade quando testadas contra soros de indivíduos com outras patologias (doença de Chagas, Lúpus Eritematoso Sistêmico, Hanseníase e Tuberculose). Para avaliar a eficácia das proteínas recombinantes foram utilizadas curvas ROC, possibilitando a seleção de antígenos possivelmente mais eficientes que o SLA no imunodiagnóstico da Leishmaniose. As proteínas recombinantes HSP70 e H2A foram selecionadas por apresentarem elevada sensibilidade, sendo reconhecida por anticorpos dos soros de pacientes com LM e LC respectivamente. Na última etapa dos experimentos, utilizando soros de indivíduos que apresentavam outras patologias, observou-se que a reação cruzada diminui frente aos antígenos recombinantes, especialmente para a rHSP70, quando comparamos à observada para o SLA. Nossos resultados mostram a elevada antigenicidade da rHSP70, sugerindo a possibilidade de utilização desta proteína recombinante para o sorodiagnóstico da Leishmaniose Tegumentar. Neste trabalho foi possível identificar e validar o uso de proteínas recombinantes do parasito e da saliva dos flebotomíneos como biomarcadores para o sorodiagnóstico e avaliação da exposição às leishmanioses. / The population control of sand flies, containment of epidemics in the early stages and facilitating early diagnosis of infected individuals are strategies outlined by WHO for surveillance and control of Leishmaniasis. In this context, serologic tests using both the salivary gland sonicate (SGS) of sandflies as soluble Leishmania antigen (SLA) are important tools for the control / diagnosis of Leishmaniasis. However, tests based on the use of antigens derived from crude fractions, despite showing high sensitivity, some of these antigens cross-react with epitopes shared by other pathogens / vectors. Moreover, the preparation of antigens has adequate reproducibility due to difficulty in obtaining and / or standardization of these. In this study, we aimed to identify biomarkers for the surveillance and control of Leishmaniasis, through use of recombinant proteins from the saliva of sandflies as biomarkers of exposure to vector and through the use of recombinant proteins of Leishmania to get a more accurate serodiagnosis for human leishmaniasis. On the first step, ELISAs were performed against the recombinant protein from the saliva of the vector L. longipalpis (rLJM11 and rLJM17) to estimate the positive anti-saliva on a small number of sera from children from an endemic area for VL. It was observed that the sera that recognize the SGS of L. longipalpis also recognize in different proportions of rLJM17 and rLJM11 proteins. Further, each recombinant protein was able to detect anti-saliva seroconversion in sera from a second endemic area for VL, with increase in recognizing when the two recombinant proteins were used in combination. Furthermore, the ROC analysis showed the superior performance of the combination of rLJM17 + rLJM11, these data confirmed using a large panel of 1077 serum samples from individuals from another endemic area for LV. At this stage, our results indicate that proteins rLJM11 + rLJM17 represent a promising epidemiological tool that can assist in the implementation of control measures against Visceral Leishmaniasis. In a second step, ELISAs were performed against a series of recombinant proteins of Leishmania (HSP70, H2A, H2B, H3, and H4 KMP11) so antigenic proteins were selected against serum from patients with cutaneous leishmaniasis (CL) and mucocutaneous leishmaniasis (MCL) and that presented high specificity when tested against sera from patients with other diseases (Chagas disease, Systemic Lupus Erythematosus, Leprosy and Tuberculosis). To identify the effectiveness of recombinant proteins, ROC curves were used to select antigens possibly more efficient than SLA. Recombinant proteins HSP70 and H2A were selected for having high sensitivity in recognizing sera from patients with LM and LC respectively. In the last experimental stage using sera from individuals with other pathologies, it was observed that the reduced cross-reactivity against the recombinant antigen, especially for rHSP70 when compared to that observed for the SLA. Our results show the high antigenicity of rHSP70, suggesting the possibility of using this recombinant protein for serodiagnosis of Leishmaniasis. In this work, it was possible to identify and validate the use of recombinant proteins of the parasite and of the saliva of sandflies as biomarkers for serodiagnosis and assessment of exposure to Leishmaniasis.

abstract: Plants are a promising upcoming platform for production of vaccine components and other desirable pharmaceutical proteins that can only, at present, be made in living systems. The unique soil microbe Agrobacterium tumefaciens can transfer DNA to plants very efficiently, essentially turning plants into factories capable of producing virtually any gene. While genetically modified bacteria have historically been used for producing useful biopharmaceuticals like human insulin, plants can assemble much more complicated proteins, like human antibodies, that bacterial systems cannot. As plants do not harbor human pathogens, they are also safer alternatives than animal cell cultures. Additionally, plants can be grown very cheaply, in massive quantities. In my research, I have studied the genetic mechanisms that underlie gene expression, in order to improve plant-based biopharmaceutical production. To do this, inspiration was drawn from naturally-occurring gene regulatory mechanisms, especially those from plant viruses, which have evolved mechanisms to co-opt the plant cellular machinery to produce high levels of viral proteins. By testing, modifying, and combining genetic elements from diverse sources, an optimized expression system has been developed that allows very rapid production of vaccine components, monoclonal antibodies, and other biopharmaceuticals. To improve target gene expression while maintaining the health and function of the plants, I identified, studied, and modified 5’ untranslated regions, combined gene terminators, and a nuclear matrix attachment region. The replication mechanisms of a plant geminivirus were also studied, which lead to additional strategies to produce more toxic biopharmaceutical proteins. Finally, the mechanisms employed by a geminivirus to spread between cells were investigated. It was demonstrated that these movement mechanisms can be functionally transplanted into a separate genus of geminivirus, allowing modified virus-based gene expression vectors to be spread between neighboring plant cells. Additionally, my work helps shed light on the basic genetic mechanisms employed by all living organisms to control gene expression. / Dissertation/Thesis / Doctoral Dissertation Microbiology 2017