Recombinant Antigen Preparation Research Articles

Heterologous Expression of Potato Virus Y Coat Protein, Isolate Pot187.

The advent of recombinant DNA technology has facilitated heterologous expression of proteins from various sources in different host systems including Escherichia coli. If a plant virus coat protein is expressed in the bacterium it can be used as the antigen for antibody preparation. Such a recombinant antigen preparation can be particularly useful where equipment such as ultracentrifuge is unavailable to purify virus particles to use as the antigen for conventional antibody preparation. Heterologous protein expression and purification of the full length Potato virus Y (PVY) coat protein (CP) from isolate pot187 (an affiliate of strain N) to be used as an antigen was the aim of the study. Reverse transcription Polymerase Chain Reaction (RT-PCR) was carried out to amplify an 801 bp fragment of the CP gene from PVY-infected potato leaves. The amplicon was cloned into pGEM-T Easy. The cloned fragment was restricted by BamHI + SacI and the purified fragment was cloned into the expression vector pET21a(+) which was restricted with the same enzymes. The generated plasmid was introduced into E. coli strain RosettaTM. The expression was induced with isopropyl-β-D-thiogalactopyranoside (IPTG) and its protein content was subjected to SDSPAGE and western blotting. SDS-PAGE analysis of protein from the induced bacteria showed a ~35 KDa protein corresponding to PVY CP. Expression of the recombinant protein was confirmed by anti-His anitibody. The full-length cDNA of PVY-CP was amplified from the infected potato leaves. The cDNA was heterologously expressed in E. coli. The produced recombinant CP can be used as an antigen to generate polyclonal antibody.

Detection of antibody responses against Mycobacterium avium subsp. paratuberculosis stress-associated proteins within 30 weeks after infection in cattle

In this study, humoral immune responses in cattle against Mycobacterium avium subsp. paratuberculosis (MAP) stress-associated recombinant proteins were assessed longitudinally by ELISA during the first 30 weeks after MAP infection. A total of 11 MAP genes previously identified by proteomic analysis were selected for cloning and expression. These included possible general stress-associated proteins of MAP and proteins expressed in vivo in MAP-infected sheep at an early stage of infection. An increase in the antibody levels against 5 recombinant antigen preparations (MAP1027c, MAP1339, MAP1588c, MAP1589c and MAP2411) was seen in MAP-infected calves (n=16) but not in control calves (n=3) over the time examined. Antibody responses were recorded as early as two weeks post-inoculation, and 87.5% of the inoculated cattle responded to at least one of the five immunogenic antigen preparations within the first 30 weeks of infection, suggesting that these proteins identified in the in vitro models of stress were also expressed in vivo in MAP-infected cattle at a relatively early stage after infection and therefore stimulate the host's immune system. It has been assumed that the sensitivity of antibody ELISA tests is dependent on the stage of infection and the age of the animals. However, we have provided some evidence that humoral immunity occurs at an early stage of paratuberculosis and can be detected using appropriate antigens such as MAP stress-associated proteins.

Exploring Technique for Pharmaceutical Target Using Antibody Technology

A monoclonal antibody (Mab), due to its specific binding ability to a target protein, can potentially be one of the most useful tools for the functional analysis of proteins in recent proteomics-based research. However, the production of Mab is a very time-consuming and laborious process (i.e., preparation of recombinant antigens, immunization of animals, preparation of hybridomas), making it the rate-limiting step in using Mabs in high-throughput proteomics research, which heavily relies on comprehensive and rapid methods. Therefore, there is a great demand for new methods to efficiently generate Mabs against a group of proteins identified by proteome analysis. Here, we describe a useful method called "Antibody proteomic technique" for the rapid generations of Mabs to pharmaceutical target, which were identified by proteomic analyses of disease samples (ex. tumor tissue, etc.). We also introduce another method to find profitable targets on vasculature, which is called "Vascular proteomic technique". Our results suggest that this method for the rapid generation of Mabs to proteins may be very useful in proteomics-based research as well as in clinical applications.

Evaluation of the immunogenicity of Mycobacterium avium subsp. paratuberculosis (MAP) stress-associated recombinant proteins

The aim of this study was to assess the humoral immune responses in MAP-infected and uninfected sheep against 27 MAP stress-associated recombinant proteins that were regulated in in vitro models of physiological stress. These include evaluation of 5 proteins, which were previously reported by Gumber et al. (2009b), using serum samples from sheep with a wide range of disease stages. For purification of recombinant his-tagged proteins expressed as an insoluble protein, on-column refolding purification was applied as well as one-step denaturing purification. All purifications together resulted in a total of 48 recombinant antigen preparations. In antibody ELISA tests, 23 of these, representing 18 MAP proteins, showed significant differences in responses between infected and uninfected sheep. Recombinant antigen preparations MAP2281c, MAP3555 (refolded form), and MAP0711c (refolded form) when incorporated in an ELISA, had similar sensitivity to a commercial antibody ELISA test at the cutpoint of 90% specificity, and showed relatively high values in receiver operating characteristic (ROC) curve analysis. However, as some of the sera from uninfected sheep also reacted to recombinant antigens, further development of the assays is necessary prior to practical application. Compared to the commercial antibody ELISA, MAP0593c, MAP2281c, MAP2411, MAP3555, and MAP3200 detected more infected sheep with a lower grade of lesion, suggesting that these proteins identified in the in vitro models of stress were also expressed in vivo in MAP-infected sheep at an early stage of infection. This is consistent with the hypothesis of latency or dormancy in subclinical mycobacterial infection.

Evaluation of the Efficacy of a Recombinant Subunit West Nile Vaccine in Syrian Golden Hamsters

The efficacy of a recombinant subunit West Nile (WN) vaccine candidate was determined in a hamster model of encephalitis. Animals included young, aged, and immunocompromised animals in an effort to simulate key groups at risk of WN virus-induced disease. Groups of aged (12 month old), weanling, and adult hamsters rendered leukopenic after immunization were immunized subcutaneously with a WN virus recombinant envelope protein (WN-80E) with or without WN virus non-structural protein 1 (NS1) mixed with adjuvant or adjuvant alone. A challenge dose of wild-type WN virus was administered to produce 40-100% mortality in the control hamsters. The recombinant antigen preparations containing WN-80E with or without WN NS1 gave similar results. Hamsters in both groups had a strong antibody response after immunization, and none of the aged or weanling animals became ill or developed detectable viremia after challenge with WN virus at 2 weeks after booster vaccination. However, mortality among the control animals (administered adjuvant without antigen) at 2 weeks after booster challenge was 40-60%. In hamsters rendered leukopenic after immunization, survival rates up to 80% were observed, and a low-level viremia was detected in the vaccinated and challenged hamsters. The survival rate was significantly (P<0.05) higher in animals vaccinated with a higher dose of WN-80E than a lower dose. The addition of NS1 did not significantly affect survival after challenge. In contrast, all of the control animals that received adjuvant only developed a very high level of viremia, and the mortality rate was 100%. These findings indicate that the recombinant WN vaccines induced antibody in and afforded protection to young and aged hamsters and immunosuppressed hamsters.

Antigen-specific T cell recognition of affinity-purified and recombinant thyroid peroxidase in autoimmune thyroid disease.

The T cell proliferative responses of peripheral blood lymphocytes from 20 patients with autoimmune thyroid disease (AITD) and 20 healthy controls were analysed to immunoaffinity-purified thyroid peroxidase (TPO) and recombinant antigen preparations generated in Escherichia coli as glutathione-s-transferase fusion proteins. The epitope specificity of the T cell response was investigated using a selection of eight discrete recombinant fragments encompassing the whole of the extracellular region of the TPO molecule. Significant differences in the proliferative responses between patients and controls were observed to the full length, affinity-purified TPO molecule (P less than 0.002) as well as to the recombinant fragments R1c (residues 145-250) (P less than 0.001) and R2b (residues 457-589) (P less than 0.001) suggesting the presence of at least two distinct T cell determinants on this autoantigen. One of these T cell epitopes, localized within the region R1c, has not previously been identified by studies with synthetic peptides.

Efficacy and durability of a recombinant subunit West Nile vaccine candidate in protecting hamsters from West Nile encephalitis

The efficacy of a new recombinant subunit West Nile virus (WNV) vaccine candidate was determined in a hamster model of meningoencephalitis. Groups of hamsters were immunized subcutaneously with a WNV recombinant envelope protein (80E) with or without WNV non-structural protein 1 (NS1) mixed with adjuvant or adjuvant alone. At 2 weeks, 6 months, and 12 months after two immunizations at 4 week intervals with the respective immunogens, groups of animals were challenged via the intraperitoneal route with a virulent strain of WNV. The two recombinant antigen preparations gave similar results; hamsters in both groups had a strong antibody response following immunization, and none of the animals became ill or developed detectable viremia after challenge with WNV at 2 weeks or 6 months post-booster vaccination. In contrast, mortality among the control animals at 2 weeks post-booster challenge was 73%, and at 6 months post-booster, the mortality was 53% among the control animals. When challenged 12 months after the booster vaccination, a low level viremia was detected in some of the vaccinated hamsters, and one hamster became sick, but recovered. In contrast, all of the control animals that received adjuvant only developed a viremia, and the mortality rate was 77%. These results with the recombinant subunit WNV vaccine are very encouraging and warrant further animal studies to evaluate its potential use to protect humans against WNV disease.

Evaluation of recombinant oocyst protein CP41 for detection of cryptosporidium-specific antibodies.

Cryptosporidium is an important cause of diarrhea in developed and developing countries, and its epidemiology is of interest. The methodologies used in the detection of Cryptosporidium-specific antibodies vary widely, which complicates comparison of results. This study assesses the performance of a Cryptosporidium recombinant protein (rCP41) in a serological assay compared to that of a crude antigen preparation. The 41-kDa protein from the oocyst wall was previously cloned and expressed in Escherichia coli. Sera from 192 healthy adults from the Texas Medical Center (Houston) were tested for anti-Cryptosporidium antibody reactivity using both crude and recombinant antigen preparations in an enzyme-linked immunosorbent assay. Immunoglobulin G reactivity was highly concordant (88%; P < 0.0001) between the two antigen preparations, with 110 positive (57%) and 59 negative (31%) by both tests. Regression analysis revealed a high correlation between the absorbance values generated with both antigen preparations and suggests that the rCP41 may be used in place of crude antigen. These results indicate that the use of the recombinant CP41 antigen in a standardized serodiagnostic assay could provide a reliable and cost-effective method for assessing human exposure to Cryptosporidium.

Purification of recombinant proteins with high isoelectric points.

The use of recombinant antigens is essential for the construction of robust and sensitive diagnostic assays. A critical step in the preparation of recombinant antigens is protein purification. Purification problems may be very different for related structural proteins expressed in the same host or for the same protein expressed in different hosts, because the biochemical characteristics of a recombinant protein, expressed in a heterologous system, are unique. In this chapter we make a brief introduction to protein purification procedures and we present a quick purification process suitable for the isolation of recombinant protein having high isoelectric points encoding non-conformational epitopes.

Production of recombinant SERA proteins of Plasmodium falciparum in Escherichia coli by using synthetic genes : Vaccine Volume 14 (11) (1996), Page 1069-1076

We expressed two regions of the serine repeat antigen (SERA) protein of Plasmodium falciparum in Escherichia coli by synthesizing the genes with a changed codon usage. One of the synthetic gene sequences encodes amino acid residues 17-382 (SE47') and the other encodes amino acid residues 586-802 (SE50A). The products produced by the synthetic gene sequences in E. coli accounted for 15-30% of the total bacterial protein. Antisera against both the purified gene products prepared in rats inhibited malaria parasite growth in vitro. The anti-SE47' serum was significantly more inhibitory than the anti-SE50A serum. The described methods provide a large scale preparation of recombinant antigens for improving and producing malaria vaccine.

Profile of antigen-specific antibody response detectable by Western blot in relation to diagnostic criteria for human immunodeficiency virus type-1 (HIV-1) infection

Background: Variability in the profile of antigen-reactive bands in Western blot for serodiagnosis of human immunodeficiency virus (HIV) infection may result in disagreement regarding interpretation of positive result, due to lack of consensus in the interpretive criteria laid down by various organisations. Objectives: The objectives of this study were (i) to find out the extent of disagreement over various criteria regarding interpretation of positivity in Western blot and (ii) to review the discordance by retesting the discordant specimens using recombinant antigens as well as by performing repeat Western blot in follow-up specimens. Study design: A total of 467 specimens from high-risk groups, diagnosed positive for HIV type-1 (HIV-1) infection by the criteria of at least one of the five organisations, viz. Association of State and Public Health Laboratories Directors (ASTPHLD), Consortium for Retrovirus Serology (CRSS), American Red Cross (ARC) and World Health Organisation (WHO), were analysed to find out the extent of discordance between various criteria for interpretation of Western blot positivity. The discordant specimens were subjected to line immunoassay (LIA) using recombinant antigens. Also, follow-up Western blots were performed in case of discordant specimens at 6, 12 and 24 weeks intervals. Results: We observed that criteria laid down by ASTPHLD, CDC and CRSS scored all the specimens as positive while ARC and WHO criteria scored 13 (2.8%) and 18 (3.8%) of specimens, respectively, as negatives which were detected as positives by other criteria (discordant specimens). The gp41 reactive band was the most frequently missing band, being undetectable in 11.6% of specimens while bands reactive to p24, p31, gp120 and gp160 could not be recorded in 1.9%, 9.4% and 3.2% and 1.5% of specimens, respectively. Testing of the discordant specimens with recombinant antigen preparation and with repeat Western blot in follow-up specimens collected at 6, 12 and 24 weeks demonstrated all bands undetectable in initial Western blot, except 25% of gp41 reactive bands. Conclusions: It is felt that before selecting any criterion for Western blot positivity, it should be evaluated in the local population at risk for HIV-1 infection with additional or follow-up tests.

Modulation of the immune response; recombinant antigen preparation by CD21 ligand, CD19 ligand or C3d fusion protein gene expression in host cell; application in improved recombinant vaccine : Lynxvale World 9617 625; 13 June 1996

Modulation of the immune response; recombinant antigen preparation by CD21 ligand, CD19 ligand or C3d fusion protein gene expression in host cell; application in improved recombinant vaccine : Lynxvale World 9617 625; 13 June 1996

Production of recombinant SERA proteins of Plasmodium falciparum in Escherichia coli by using synthetic genes

We expressed two regions of the serine repeat antigen (SERA) protein of Plasmodium falciparum in Escherichia coli by synthesizing the genes with a changed codon usage. One of the synthetic gene sequences encodes amino acid residues 17–382 (SE47′) and the other encodes amino acid residues 586–802 (SE50A). The products produced by the synthetic gene sequences in E. coli accounted for 15–30% of the total bacterial protein. Antisera against both the purified gene products prepared in rats inhibited malaria parasite growth in vitro. The anti-SE47′ serum was significantly more inhibitory than the anti-SE50A serum. The described methods provide a large scale preparation of recombinant antigens for improving and producing malaria vaccine.

Cloned antigens and antiidiotypes.

Both monoclonal and polyclonal antiidiotypic antibodies mimicking the human colorectal carcinoma (CRC) associated antigen CO17-1A/GA733 have induced antigen-specific humoral and cellular immunity in CRC patients. The immune responses may underlie the clinical responses observed in some of the treated patients. Recently, the CO17-1A/GA733 antigen has been molecularly cloned and expressed in baculo-, adeno-, and vaccinia viruses. In preclinical studies, these recombinant antigen preparations elicited specific humoral immunity (cytotoxic antibodies) and cellular immunity (DTH-reactive and proliferative T cells). Antibody titers elicited in animals by recombinant antigen were significantly higher than those elicited by antiidiotypes. The recombinant antigen has a potential as a vaccine for CRC patients.

Mapping epitope specificities of monoclonal antibodies to thyroid peroxidase using recombinant antigen preparations.

Five separate monoclonal antibodies (MoAbs) to human thyroid peroxidase (hTPO) were raised by immunising Balb/c mice with hTPO purified from detergent solubilised thyroid microsomes by high performance liquid chromatography (HPLC). The epitope specificities of these MoAbs were determined by assessing their ability to bind to purified recombinant fusion protein fragments of human TPO (TPO(r)) generated in E. coli. A total of seven small overlapping fragments (averaging 104 amino acid residues) of hTPO, encompassing over 90% of the extracellular region of the molecule, were generated as glutathione S-transferase (GST) fusion proteins. The sequential epitopes on TPO(r) recognised by these MoAbs were analysed by both immunoblotting and enzyme linked immunosorbent assay (ELISA). Two different MoAbs (A4 and A5) recognised sequential epitopes within the TPO(r) preparation termed R1a + b (residues 1-160) and more specifically, in the case of MoAb A4, within the subfragment R1b (residues 70-160). The inability of the other MoAbs (A1-A3) to recognise recombinant fragments, suggests they either recognise conformational determinants on the TPO molecule or epitopes that are present on the small regions of the TPO molecule which have not been expressed as recombinant proteins.

Detection Of Autoantibodies To Recombinant Human Thyroid Peroxidase By Sensitive Enzyme Immunoassay

Autoantibodies to thyroid peroxidase (TPO), the thyroid 'microsomal' antigen, are widely utilized in the diagnosis of human autoimmune thyroid disease. Crude human thyroid preparations of TPO are of differing potency, contain residual thyroglobulin (Tg) and other human membrane antigens, and are available in only limited amounts. Hence, immunoassays for anti-TPO are unstandardized and of variable sensitivity and specificity. We co-transfected the Chinese hamster ovary (CHO) cell line with a full-length human TPO cDNA expression plasmid. We selected a high expressing recombinant TPO positive cell population (CHO-TPO) by Northern blot analysis, then fluorescence laser flow cytometry using both human polyclonal and murine monoclonal anti-TPO antibodies. Solubilized 100,000 g membrane preparations from both CHO-TPO and CHO cells were used as antigens in a specific ELISA with CHO antigen serving as background control. In a selected series of known anti-TPO positive (n = 46) and negative (n = 73) sera there was a high correlation between ELISAs utilizing recombinant or natural-TPO antigen (r = 0.93). There appeared to be no difference in the affinity of high titre human anti-TPO for recombinant and natural-TPO antigen with both ELISAs able to detect 0.05 U/ml of anti-TPO activity (reference preparation NIBSC 66/387). These data predict a new era in standardized thyroid autoantibody testing utilizing recombinant antigen preparations.