Prokaryotic Expression, Purification, and Polyclonal Antibody Production of a Truncated Recombinant Rabies Virus L Protein

Development of Monoclonal Antibodies for Detection of Conserved and Variable Epitopes of Large Protein of Rabies Virus

Rabies virus (RABV) causes fatal neurological encephalitis and results in approximately 6000 human death cases worldwide every year. The large (L) protein of RABV, possessing conserved domains, is considered as the target for detection. In this study, three monoclonal antibodies (mAbs), designated as 3F3, 3A6 and L-C, against L protein were generated by using the recombinant truncated L protein (aa 1431-1754) and the epitopes were also identified using a series of overlapping truncated polypeptides for testing the reactivity of mAbs with different RABV strains. The ¹⁴⁷⁹EIFSIP¹⁴⁸⁴, ¹⁶⁵⁹RALSK¹⁶⁶³ and ¹⁷²⁴VFNSL¹⁷²⁸ were identified as the minimal linear epitopes recognized by mAbs 3F3, 3A6 and L-C, respectively. Amino acid alignment showed epitope ¹⁷²⁴VFNSL¹⁷²⁸ recognized by mAb L-C is completely conserved among RABV strains, indicating that mAb L-C could be used to detect all of the RABV strains. Epitope ¹⁴⁷⁹EIFSIP¹⁴⁸⁴ is highly conserved among RABV strains except for a P1484S substitution in a China I sub-lineage strain of Asian lineage, which eliminated the reactivity of the epitope with mAb 3F3. However, the epitope ¹⁶⁵⁹RALSK¹⁶⁶³ was only completely conserved in the Africa-2 and Indian lineages, and a single A1660T substitution, mainly appeared in strains of the China I belonging to Asian lineage and a Cosmopolitan lineage strain, still retained the reactivity of the epitope with mAb 3A6. While both A1660T and K1663R substitutions in a China I lineage strain, single K1663R/Q substitution in some China II strains of Asian lineage and some Arctic-like lineage strains and R1659Q mutation in a strain of Africa-3 lineage eliminated the reactivity of the epitope with mAb 3A6, suggesting mAb 3A6 could be used for differentiation of variable epitopes of some strains in different lineages. Thus, variability and conservation of the three epitopes of L protein showed the reactive difference of mAbs among RABV strains of different lineages. These results may facilitate future studies in development of detection methods for RABV infection, the structure and function of RABV L protein.

Production and Partial Purification of the Grapevine Fanleaf Virus Coat Protein 42 Polyclonal Antibody Against Inclusion Body Expressed in Escherichia coli

Background

Expression of virus coat protein (CP) in Escherichia coli often leads to production of partially folded aggregated proteins which are called inclusion bodies. Grapevine fanleaf virus (GFLV) is one of the most serious and widespread grapevine virus diseases around the world and in Iran.

Objective

The main objective of this study was to find a simple and brief method for producing polyclonal antibodies (PAbs) to be used for immunodiagnosis of GFLV.

Material and Methods

An antigenic determinant in GFLV CP gene was inserted into pET-28a bacterial expression vector and the construct (pET-28a CP42) was cloned into E. coli strain BL21 (DE3).

The recombinant coat protein of GFLV (CP42) was expressed and characterized by SDS-PAGE and western blot analysis using commercial anti-GFLV antibody. Expression of the CP was detected in the form of inclusion bodies in insoluble cytoplasmic fraction. Then, the inclusion bodies were isolated from the bacterial cells and injected into rabbits for PAbs production. The reaction of the antiserum was checked by ELISA assay. In order to analyze efficiency of the produced PAbs, first the infected and uninfected grapevine samples were confirmed based on morphological symptoms then the indirect plate- trapped antigen Enzyme-linked Immunosorbent Assay (IPTA-ELISA) was applied using the commercial anti GFLV antibody. In the next ELISA assay, efficiency of the raised polyclonal antibody was compared with commercial one.

Results

The expression of recombinant CP42 induced by IPTG was confirmed by the band of 42 kDa in SDS-PAGE and western blot. The antiserum of purified inclusion body immunized rabbit was reacted with CP42 and GFLV infected Grapevine samples. The results revealed an acceptable efficacy for prepared antibodies compared to that of commercial antibody.

Conclusions

It was evident that the recombinant coat protein in the form of inclusion bodies can be prepared and used as the antigen for immunizing animals in order to produce PAbs.

MitoKATP channels promote the proliferation of hypoxic human pulmonary artery smooth muscle cells via the ROS/HIF/miR-210/ISCU signaling pathway

Previous results have indicated that mitochondrial ATP-sensitive potassium (mitoK_ATP) channels are associated with the hypoxic proliferation of pulmonary artery smooth muscle cells (PASMCs). However, the mechanism underlying the promotive effects of mitoK_ATP channels on cell proliferation in response to hypoxia remains unknown. mitoK_ATP channel opening results in a collapse of mitochondrial membrane potential and generation of mitochondrial reactive oxygen species (ROS). As hypoxia-inducible factor-1α (HIF-1α) is a critical oxygen sensor and major transcriptional regulator of the hypoxic adaptive response, the current study assessed whether mitoK_ATP opening contributes to the chronic proliferation of human PASMCs (hPASMCs) in collaboration with HIF-1α and its downstream targets under hypoxic conditions. The present study demonstrated that there was crosstalk between mitoK_ATP channels and HIF-1α signaling in PASMCs under hypoxic conditions. The results suggest that mitoK_ATP channels are involved in the proliferation of PASMCs during hypoxia through upregulation of the ROS/HIF/microRNA-210/iron-sulfur cluster protein signaling pathway.

Enzymatic Kinetic Properties of the Lactate Dehydrogenase Isoenzyme C₄ of the Plateau Pika (Ochotona curzoniae)

Testis-specific lactate dehydrogenase (LDH-C₄) is one of the lactate dehydrogenase (LDH) isozymes that catalyze the terminal reaction of pyruvate to lactate in the glycolytic pathway. LDH-C₄ in mammals was previously thought to be expressed only in spermatozoa and testis and not in other tissues. Plateau pika (Ochotona curzoniae) belongs to the genus Ochotona of the Ochotonidea family. It is a hypoxia-tolerant species living in remote mountain areas at altitudes of 3000-5000 m above sea level on the Qinghai-Tibet Plateau. Surprisingly, Ldh-c is expressed not only in its testis and sperm, but also in somatic tissues of plateau pika. To shed light on the function of LDH-C₄ in somatic cells, Ldh-a, Ldh-b, and Ldh-c of plateau pika were subcloned into bacterial expression vectors. The pure enzymes of Lactate Dehydrogenase A₄ (LDH-A₄), Lactate Dehydrogenase B₄ (LDH-B₄), and LDH-C₄ were prepared by a series of expression and purification processes, and the three enzymes were identified by the method of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and native polyacrylamide gel electrophoresis (PAGE). The enzymatic kinetics properties of these enzymes were studied by Lineweaver-Burk double-reciprocal plots. The results showed the Michaelis constant (Km) of LDH-C₄ for pyruvate and lactate was 0.052 and 4.934 mmol/L, respectively, with an approximate 90 times higher affinity of LDH-C₄ for pyruvate than for lactate. At relatively high concentrations of lactate, the inhibition constant (Ki) of the LDH isoenzymes varied: LDH-A₄ (Ki = 26.900 mmol/L), LDH-B₄ (Ki = 23.800 mmol/L), and LDH-C₄ (Ki = 65.500 mmol/L). These data suggest that inhibition of lactate by LDH-A₄ and LDH-B₄ were stronger than LDH-C₄. In light of the enzymatic kinetics properties, we suggest that the plateau pika can reduce reliance on oxygen supply and enhance its adaptation to the hypoxic environments due to increased anaerobic glycolysis by LDH-C₄.