A nanobody-based blocking enzyme-linked immunosorbent assay for detecting antibodies against pseudorabies virus glycoprotein E

Pseudorabies(PR)is an acute infectious disease of pigs caused by the PR virus(PRV)and results in great economic losses to the pig industry worldwide.PRV glycoprotein E(gE)-based enzyme-linked immunosorbent assay(ELISA)has been used to distinguish gE-deleted vaccine-immunized pigs from wild-type virus-infected pigs to eradicate PR in some countries.Nanobody has the advantages of small size and easy genetic engineering and has been a promising diagnostic reagent.However,there were few reports about developing nanobody-based ELISA for detecting anti-PRV-gE antibodies.In the present study,the recombinant PRV-gE was expressed with a bacterial system and used to immunize the Bactrian camel.Then,two nanobodies against PRV-gE were screened from the immunized camel by phage display technique.Subsequently,two nanobody-HRP fusion proteins were expressed with HEK293T cells.The PRV-gE-Nb36-HRP fusion protein was selected as the probe for developing the blocking ELISA(bELISA)to detect anti-PRV-gE antibodies.Through optimizing the conditions of bELISA,the amount of coated antigen was 200 ng per well,and dilutions of the fusion protein and tested pig sera were separately 1:320 and 1:5.The cut-off value of bELISA was 24.20%,and the sensitivity and specificity were 96.43 and 92.63%,respectively.By detecting 233 clinical pig sera with the developed bELISA and a commercial kit,the results showed that the coincidence rate of two assays was 93.99%.Additionallly,epitope mapping showed that PRV-gE-Nb36 recognized a conserved conformational epitope in different reference PRV strains.Simple,great stability and low-cost nanobody-based bELISA for detecting anti-PRV-gE antibodies were developed.The bELISA could be used for monitoring and eradicating PR.

Cross-species recognition of bat coronavirus RsYN04 and cross-reaction of SARS-CoV-2 antibodies against the virus

Following the outbreak of coronavirus disease 2019(COVID-19),several severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)-related coronaviruses have been discovered.Previous research has identified a novel lineage of SARS-CoV-2-related CoVs in bats,including RsYN04,which recognizes human angiotensin-converting enzyme 2(ACE2)and thus poses a potential threat to humans.Here,we screened the binding of the RsYN04receptor-binding domain(RBD)to ACE2 orthologs from 52animal species and found that the virus showed a narrower ACE2-binding spectrum than SARS-CoV-2.However,the presence of the T484W mutation in the RsYN04 RBD broadened its range.We also evaluated 44 SARS-CoV-2antibodies targeting seven epitope communities in the SARS-CoV-2 RBD,together with serum obtained from COVID-19 convalescents and vaccinees,to determine their cross-reaction against RsYN04.Results showed that no antibodies,except for the RBD-6 and RBD-7 classes,bound to the RsYN04 RBD,indicating substantial immune differences from SARS-CoV-2.Furthermore,the structure of the RsYN04 RBD in complex with cross-reactive antibody S43 in RBD-7 revealed a potently broad epitope for the development of therapeutics and vaccines.Our findings suggest RsYN04 and other viruses belonging to the same clade have the potential to infect several species,including humans,highlighting the necessity for viral surveillance and development of broad anticoronavirus countermeasures.

Generation of Antibodies Against DMRT1 and DMRT4 of Oreochromis aurea and Analysis of Their Expression Profile in Oreochromis aurea Tissues

Sex determination is composed of somatic and germ-line sex differentiation hierarchies whose interaction is poorly understood. A single gene known to control somatic sex determination, the DM-domain containing （Doublesex/Mab-3 DNA-binding motif） gene, is highly conserved across species. Vertebrate DMRT1 （DM-related transcription factor 1） expression occurs predominantly in the testis. Here, however, isolated two distinct DM-domain cDNA from Oreochromis aurea ovary and testis have been named DMRT4 （DM-related transcription factor 4） and DMRT1 by BLAST, respectively. Despite high homology in the DM-domain there is little similarity outside the DM-domain.To better understand the structure, function, and possible roles of DMRT4 and DMRT1 as potential candidates for sex differentiation and sex determination, the intact regions encoding DMRT4 and DMRT1 obtained by PCR were sub-cloned into the vector pMAL-c2x and introduced into the Escherichia coli TB1 cell for efficient fusion expression. After purification and cleavage, DMRT4 and DMRT1 proteins were used to immunize adult rabbits following standard protocols. Consequently, it was found by using Western blot analysis that polyclonal antibodies against DMRT4 and DMRT1 had high specificity. The relative expression levels of DMRT4 and DMRT1 mRNA were determined by fluorescent Real-time RT-PCR in female and male Oreochromis aurea with 13-actin as the internal standard. DMRT1 was expressed only in testis, whereas DMRT4 was over expressed in the ovary, but in both female and male, a slight expression in the brain was also detected. Statistical analysis showed that in the brain, mean DMRT4 mRNA levels in female were significantly higher than in male. Meanwhile, the expression of DMRT4 and DMRT1 protein was also analyzed using the purified antibodies through Western blot and immunohistochemistry. It was found that DMRT4 was exclusively expressed in the ovary and DMRT1 in the testis. Study on DMRT4 and DMRT1 expression facilitated the elucidation of their roles and the understanding of sex differentiation of fish.

Effects of monoclonal antibodies against human stathmin 1 combined paclitaxel on proliferation of human hepatocellular carcinoma cell lines

Objective： We investigated the effects of monoclonal antibodies against stathmin 1 combined paclitaxel on the proliferation of HCC cells. Methods： HepG2 cells were treated with monoclonal antibodies against stathmin 1, paclitaxel alone or their combination, with the untreated cells used as the control, 24, 48, 72, 96 h later, the cell growth condition was observed by invert microscope and inhabitation rate was studied by MTT assay; The apoptosis was analyzed by flow cytometry with Annexin V/PI. Results： The population decreased and shape, size changed after treating with different concentration of experimental groups. Monoclonal antibodies against stathmin 1 and paclitaxel used alone or in combination both inhibited the proliferation of HepG2 cells, the inhibition ratio of their combination was more higher （P 〈 0.05）, and a synergistic effect of the two agents was noted in their combined action （P 〈 0.05）. Combined treatment of the cells resulted in significantly higher apoptosis rate than that in the other groups （P 〈 0.05）. Conclusion： Monoclonal antibodies against stathmin 1 and paclitaxel used alone or in combination both can inhibit proliferation of HepG2 cells and induce apoptosis. A synergistic effect is obsewed between the monoclonal antibodies against stathmin 1 and paclitaxel in their inhibition of HepG2 cell proliferation.

MONOCLONAL ANTIBODIES AGAINST HUMAN GASTRIC CANCER

Spleen cells from Balb/c mice immunized with five human gastric cancer cell lines in sequence were fused with murine myeloma cell line SP2/0, and hybridomas 3F4, 3G9 and 3H11, secreting monoclonal antibodiees (MoAbs) against gastric cancer, were obtained through selective culture and screening. These MoAbs have both good selectivity and a high positive rate of reaction for gastric cancer, reaching 5/5 and 84.8% to 93.5% for gastric cancer cells and tissues respectively. The reaction of MoAbs with normal cells and tissues was neglible.The corresponding antigens of the MoAbs were sensitive to digestion by trypsin and pronase and resistant to treatment with sodium periodate, indicating their nature as proteins. The antigen 3G9 could be visualized with Western blotting as two bands with molecular weights of 100KD and 70KD, however no band was found for antigens 3F4 and 3H11. There was a high expression of antigens in the majority of gastric cancer cells and tissues independent of his-topathological type of gastric cancer. A low expression of antigens was seen with other tumors and fetal gastrointestinal tissues. These could be considered as gastric cancer-associated antigens or on-cofetal antigens with a quite extensive distribution.

PREPARATION AND CHARACTERIZATION OF TWO MONOCLONAL ANTIBODIES AGAINST A_α CHAIN'S C TERMINUS OF FIBRINOGEN

Two monoclonal antibodies (McAbs) against Aα chain's C terminus offibrinogen (Fg) have been prepared and designated SZ-78 and SZ-79. Both theantigens in binding assay and immunoblot analysis showed that the two McAbs recognized the epitopes located in residues 549-560 of the Aαchain. The two McAbs couldaccelerate rate of fibrin polymer assembly both in the purified system and in the humanplasma. From the pictures of transmission electronmicroscope, the average diametersof the fibers increase significantly to an average diameters of 375 nm after incubationwith the McAbs, while it was only 75nm without addition of the McAbs. There were al-so more branchings of fibers with addition of McAbs. These observations demonstratethat the amino acid sequences ofα 549-560 in the COOH terminus of the Aα chain mayplay an important role in the assembly of a fibrin clot, presumably being involved in lat-eral aggregation of protofibrils. The preparation of the McAbs supplies a usuful probe for the investigation of the

GENERATION AND CHARACTERIZATION OF TWO MONOCLONAL ANTIBODIES AGAINST CYTOKERATINS

Thirty-five hybridoma cell lines against cytoke-ratins, isolated from Hela cells and human cellus respectively, were generated by fusion of immunized spleen cells of BALB/C mice with P3×63-Ag8.653, a mouse myeloma cell line. Two of them (HI and C53) were characterized by indirect immu-nofluorescence, ABC immunostaining and immuno-blotting. The results of immunofluorescence and ABC immunostaining suggested that both monoclonal antibodies were specific for keratin-type intermediate filaments. However, the two monoclonal antibodies showed different specificities in normal tissues and neoplasms as observed on both frozen and deparaf-finized sections. In normal tissues, H1 stained transitional epithelium and all types of simple epithelium except endothelium and mesothelium but did not stain stratified squamous epithelium. In contrast, C35 recognized only stratified squamous epithelium, but failing to react with simple epithelium. Both monoclonal antibodies did not react with nonepithelia cells and tissues. In neoplasms, H1 stained varieties of adenocaroinomas and C35 recognized merely squamous cell carcinomas. Therefore, all the epithelial tissues can nearly be recognized by combination of the two monoclonal antibodies. All the results indicated that H1 and C35 can be used in cell biology and histology studies, and can be used in differential diagnosis of adenocarcinoma and squamous cell carcinoma in pathology.

CLINICAL EVALUATION OF MONOCLONAL ANTIBODIES AGAINST ALDOLASE-A IN THE DIAGNOSIS OF HEPATO-CELLULAR CARCINOMA

Serum ALD-A of 57 patients with HCC and 43 of other diseases were measured by ALD-A-McAb linked with 425I-staphylococcus A protein. The results showed that the ALD-A in patient with HCC was significantly elevated as compared with controls and that in patients with cholangiocarcinoma, gastrointestinal cancer without hepatic metastasis, cirrhosis. CAH and benign GI diseases. There was no statistical difference between ALD-A in patients with HCC and that in cases of cirrhosis with liver failure and that in cases of metastatic liver carcinoma. It was noted that diagnostic sensitivity of ALD-A in AFP (+) HCC was 73.9% and that in AFP (-) HCC was 81.8% 1-6 patients with HCC were treated by hepatic arterial embolization combined with chemotherapy. ALD-A in patients after the treatment decreased significantly than that before treatment, furthermore, advantages of the method are discussed.

Development and detection application of monoclonal antibodies against Zucchini yellow mosaic virus

Aphid-borne Zucchini yellow mosaic virus （ZYMV） is one of the most economically important viruses of cucurbitaceous plants. To survey and control this virus, it is necessary to develop an efficient detection technique. Using purified ZYMV virion and the conventional hybridoma technology, three hybridoma cell lines （16A11, 5A7 and 3B8） secreting monoclonal antibodies （MAbs） against ZYMV Zhejiang isolate were obtained. The working titers of the ascitic fluids secreted by the three hybridoma cell lines were up to 10^-7 by indirect enzyme-linked immunosorbent assay （ELISA）. All MAbs were isotyped as IgG1, kappa light chain. Western blot analysis indicated that the MAb 3B8 could specifically react with the coat protein of ZYMV while MAbs 5A7 and 16A11 reacted strongly with a protein of approximately 51 kDa from the ZYMV-infected leaf tissues. According to this molecular weight, we consider this reactive protein As likely to be the HC-Pro protein. Using these three MAbs, we have now developed five detection assays, i.e., antigen-coated-plate ELISA （ACP-ELISA）, dot-ELISA, tissue blot-ELISA, double-antibody sandwich ELISA （DAS-ELISA）, and immunocapture-RT-PCR （IC-RT-PCR）, for the sensitive, specific, and easy detection of ZYMV. The sensitivity test revealed that ZYMV could be readily detected respectively by ACP-ELISA, dot-ELISA, DAS-ELISA and IC-RT-PCR in 1：163840, 1：2560, 1：327680 and 1：1 310720 （w/v, g mL-1） diluted crude extracts from the ZYMV-infected plants. We demonstrated in this study that the dot-ELISA could also be used to detect ZYMV in individual viruliferous aphids. A total of 275 cucurbitaceous plant samples collected from the Zhejiang, Jiangsu, Shandong and Hainan provinces, China, were screened for the presence of ZYMV with the described assays. Our results showed that 163 of the 275 samples （59%） were infected with ZYMV. This finding indicates that ZYMV As now widely present in cucurbitaceous crops in China. RT-PCR followed by DNA sequencing and sequence analyses confirmed the accuracy of the five assays. We consider that these detection assays can significantly benefit the control of ZYMV in China.

Production and Identification of High Affinity Monoclonal Antibodies Against Pesticide Carbofuran

To produce high-affinity monoclonal antibodies against pesticide carbofuran, and the develop immunochemical assays for people＇s health and environmental protection, the hapten 4-[[（2,3-dihydro-2,2-dimethyl-7-benzofuranyloxy） carbonyl]- amino]-butanoic acid （BFNB） of carbofuran was synthesized and Balb/c mice were immunized by the hapten-carrier （BFNB-bovine serum albumin, BFNB-BSA） conjugates. The splenocytes of immunized mice were fused with Sp2/0 cells and the cultural supernatants of hybridoma cells were screened by the indirect enzyme-linked immunoabsorbent assay （ELISA）, based on BFNB-ovoalbumin conjugates （BFNB-OVA）. Purified monoclonal antibody （McAb） was obtained from fluids of ascites, deposited by octanoic acid and ammonium sulfate. The affinity and the specificity of McAb were characterized by ELISA or indirect competitive ELISA. A hybridoma cell line （5D3） secreting anti-carbofuran McAb had been established. The titer of culture medium and ascites was up to 1：2.048 × 10^3 and 1：1.024 × 10^6, respectively, and the subtype of the McAb was IgG1. The affinity constant of the McAb was about 2.54 × 10×9 L mol^-1, with an IC50 value of 1.18 ng mL^-1 and a detection limit of 0.01 ng mL^-1. Cross-reactivity studies showed that the McAb was quiet specific for carbofuran, as among the four analogous compounds, they were all hardly recognized （4.59 × 10^-4% for 2,3-dihydro-2,2- dimethyl-7-benzofuranol and less than 3.0 × 10^4% for others）. The prepared McAb had a very high affinity and specificity, and it could be used to develop ELISA for rapid determination of carbofuran.

Antibodies Against Annexin V and Prothrombin,Their Correlation with Other Anti-phospholipid Antibodies in Recurrent Pregnancy Loss

Objective To study the findings of serum antibodies against annexin V, prothrombin, ph-inositol, ph-acid, ph-ethanolamine, ph-serine, ph-glycerol, cardiolipin, and beta2-glycoprotein I and analyze the trophoblast annexin V receptors Methods Sera from 156patients aged 26-41 years with recurrent pregnancy loss （3-7 times） were investigated. Eighty-four fertile healthy women aged 24-38 years were included in a control group. ELISA methods were used for detecting a panel of sera anti-phospholipid antibodies. Immunolocalization of annexin V receptors in 143 trophoblast specimens of 156 patients was investigated by the immunofluorescence technique using Annexin V-FITC, Apoptosis and Annexin V-CY3 commercial kits. Results Positivity for anti-phospholipid antibodies mainly against ph-serine, ph- ethanolamine, and ph-inositol was found together in 80. 8%（126 out of 156 patients）, anti-prothrombin antibodies in 12% （18）, and anti-annexin V antibodies in 13. 5% （21） women. No significant levels of anti-phospholipid antibodies were found in 6 controls. Placenta immunohistopathology also exhibited some changes manifested by the presence of apoptotic and necrotic cells in trophoblast, and very few microthrombotization in some intervillous spaces. Conclusion Our detailed study demonstrated the prevalence of majority of antiphospholipid antibodies as a high risk factor for repeated reproductive failure. Very low microthrombosis in placentas could be explained by the changes of haemocoagulation properties out of uterus.

Monoclonal Antibodies Against the Whitefly-Transmitted Tomato Yellow Leaf Curl Virus and Their Application in Virus Detection

Tomato yellow leaf curl virus（TYLCV）is a species of the family Geminiviridae,causing serious yield losses in tomato production.The coat protein（CP）gene of TYLCV isolate SH2 was expressed in Escherichia coli BL21（DE3）using pET-32a as the expression vector.The recombinant protein was purified through Ni＋-NTA affinity column and used to immunize BALB/c mice.Three hybridoma cell lines（2B2,2E3 and 3E10）secreting monoclonal antibodies（MAbs）against TYLCV CP were obtained by fusing mouse myeloma cells（Sp 2/0）with spleen cells from the immunized BALB/c mouse.The titers of ascitic fluids of three MAbs ranged from 10-6 to 10-7 in indirect-ELISA.Isotypes and subclasses of all the MAbs belonged to IgG1,κ light chain.Triple antibody sandwich enzyme-linked immunosorbent assay（TAS-ELISA）showed that the MAb 3E10 could react with five begomoviruses infecting tomato,while the other two（2B2 and 2E3）mainly reacted with TYLCV.TAS-ELISA was set up using the MAb 3E10,and the established method could successfully detect virus in plant sap at 1：2 560（w/v,g mL-1）.Detection of field samples showed that begomoviruses were common in tomato crops in Zhejiang Province,China.

Characterization and application of monoclonal antibodies against Shewanella marisflavi, a novel pathogen of Apostichopus japonicus

Shewanella marisflavi strain AP629 was certified as a novel pathogen of the sea cucumber Apostichopusjaponicus. In this study, four monoclonal antibodies （MAbs） （3C1, 3D9, 2F2, 2A8） against strain AP629 were developed by immunizing Balb/C mice. 3C1 and 3D9 recognized S. marisflavi only, showing no cross reactivity to other gram-negative bacteria, However, 2F2 and 2A8 showed cross reactivity to all tested bacteria. Indirect immunofluorescence, and immunogold electron microscopy, showed the binding antigens of 3C1 and 3D9 were located at the secretion on the surface of strain AP629. The binding antigens of 2F2 and 2A8 were noted on the membrane of the cells. MAbs 3C1 and 3D9 recognized the lipopolysaccharide fraction of strain AP629, and 2F2 and 2A8 recognized in western-blotting protein antigens with molecular weights of 113 and 128 kDa respectively. MAbs 3C1 and 3D9 have the potential for use in pathogen diagnosis, epidemiology and studies on the mechanism of how S. marisflavi infects A. japonicus. Imrnunohistochemistry with 3C1 or 3D9 identified strain AP629 in the body wall of infected A. japonicus. In the adult sea cucumbers that were infected via body wall injection, positive signals were observed at the site of skin ulceration, and at the connective tissue of the non-ulcerated body wall. In addition, some large blue-stained cells aggregated at the connective tissue colonized by large numbers of bacteria. In juveniles infected via immersion infection, positive signals were observed at the cuticle of the body wall only. Our results suggest that 3C1 and 3D9 could be used in various immunological assays to study the invasion mechanism of strain AP629 in A. japonicus, the law of bacterial colonization, proliferation in different tissues of A. japonicus, and correlation between secretion on the surface of strain AP629 and its pathogenesis to A. japonicus.

Effects of the Sheep Polyclonal Antibodies Against the Porcine Adipocyte Plasma Membrane Proteins on Porcine Carcass Composition and Meat Quality

To detect the effects of the polyclonal antibodies raised in sheep against porcine adipocyte plasma membranes on the porcine carcass composition and meat quality, 30 pigs assigned into 6 treatment groups were given intraperitoneal injections of sheep antipig adipocyte plasma membrane immunoglobulin （ASIg） or sheep nonimmune serum immunoglobulin （NSIg）. At the end of the experiment, the pigs were slaughtered at 90 kg body weight, and carcasses and meat quality were evaluated. The results showed that when pigs intraperitoneally immunized with 20 or 30 mg ASIg at 15 kg body weight, 20 mg purified ASIg twice at 15 and 60 kg body weight, or 20 mg purified ASIg at 60 kg body weight, respectively, their lean meat percentage, fat meat percentage, backfat thickness, loin eye area leaf fat weight, caul fat weight, heart weight, liver weight, and kidney weight were significantly affected. However, the kidney weight, lurrg weight, dressing percentage, and spleen weight did not remarkably change. Our results indicated that pigs intraperitoneally immunized with 20 or 30 mg ASIg at 15 kg body weight, and 20 mg ASIg twice at 15 and 60 kg body weight, have significantly different drip loss rate, cooked meat ratio, tenderness, storage loss rate, muscle fiber diameter, moisture content, dry matter content, crude protein content, and crude fat content from the control group that received 20 mg NSIg at 15 kg body weight. However, meat pH, meat color value, meat marbling score, inosinate, and myohemoglobin were not significantly affected. Our results indicated ASIg could not significantly affect the content of most muscular amino acids and intramuscular fatty acids.

A panel of monoclonal antibodies against the prion protein proves that there is no prion protein in human pancreatic ductal epithelial cells

Prion diseases are a group of neurodegenerative diseases that are fatal. The study of these unique diseases in China is hampered by a lack of resources. Amongst the most important resources for biological study are monoclonal antibodies. Here, we characterize a panel of monoclonal antibodies specific for cellular prion protein by enzyme-linked immunosorbent assay(ELISA), immunofluorescent staining, flow cytometry, and western blotting. We identify several antibodies that can be used for specific applications and we demonstrate that there is no prion protein expression in human pancreatic ductal epithelial cells(HPDC).

Production and Characterisation of Monoclonal Antibodies against 19-Nortestosterone

Objective To produce anti‐19‐Nortestosterone （NT） monoclonal antibodies and identify their immunological characteristics. Methods Hybridomas were prepared by fusing NS0 mouse myeloma cells with splenocytes isolated from immunized BALB/c mice. Noncompetitive and competitive indirect ELISA were employed to screen positive cell clones. A caprylic acid ammonium sulphate （CAAP） method was used to purify NT mAb, and the Batty saturation method was used to determine the affinity constant （Kaff）. Results Five hybridoma cell lines, named NT‐1, NT‐2, NT‐3, NT‐4, and NT‐5, were identified and their corresponding mAbs were of the IgG 1 isotype with a k light chain. The Kaffs of all mAbs were between 2.6 and 4.7×10 9 L/mol. The titers and IC 50 values of purified ascite fluids were in the range of （0.64–2.56）×10 5 and （0.55–1.0） ng/mL, respectively. Of all the cross‐reacting steroids, α ‐NT was the most reactive with the mAbs at 62% with NT‐1 mAb and 64% with NT‐2 mAb. Negligible cross‐reactivity （0.01%） with other steroids was observed. Conclusion The establishment of these hybridomas allows the potential development of a rapid test kit, and may provide an alternative method for the detection of NT residues in food producing animals.

In vivo neutralization assays by monoclonal antibodies against white spot syndrome virus in crayfish (Cambarus proclarkii)

The neutralizing activities of eight monoclonal antibodies （MAbs） against white spot syndrome virus （WSSV） （2D2, 2B2,1D2, 1D5, 1C2, 4A1, 6A4 and 6B4） were analyzed by in vivo experiments. Gills from WSSV-infected shrimp were homogenized and ten-fold serially diluted by PBS, and then incubated with MAbs （hybridoma culture supernatant）, respectively. The mixture of WSSV and MAbs were injected into crayfish （Procambarus clarkii）. After challenge, the death rates of crayfish were counted to determine the neutralizing activities of MAbs. At the same time, the mixture of myeloma culture supernatant and WSSV or PBS was served as positive or negative control, respectively. The results showed that, at each virus dilution, the mean time to death of the crayfish injected with MAb-treated virus was significantly longer than that in the positive control, though they all showed 100% mortality within 25 d, and meanwhile, few crayfish died in the negative control. Among the eight MAbs, 2D2, 2B2, 1D2 and 1D5, especially the former two, delayed the mortality significantly, and 1 C2, 4A1 and 6A4 delayed the mortality as well but not so efficiently, while MAb 6IM was efficient only when the virus concentration increased. The results indicated that the anti-WSSV MAbs can neutralize WSSV in different virus dilutions.

Understanding neutralising antibodies against SARS-CoV-2 and theirimplications in clinical practice

Severe acute respiratory syndrome coronavirus (SARS-CoV-2) is a newly identified member of the coronavirus family that has caused the coronavirus disease 2019 (COVID-19) pandemic. This rapidly evolving and unrelenting SARS-CoV-2has disrupted the lives and livelihoods of millions worldwide. As of 23 August 2021, a total of 211,373,303 COVID-19cases have been confirmed globally with a death toll of 4,424,341. A strong understanding of the infection pathway of SARS-CoV-2, and how our immune system responds to the virus is highly pertinent for guiding the development and improvement of effective treatments. In this review, we discuss the current understanding of neutralising antibodies(NAbs) and their implications in clinical practice. The aspects include the pathophysiology of the immune response,particularly humoral adaptive immunity and the roles of NAbs from B cells in infection clearance. We summarise the onset and persistence of IgA, IgM and IgG antibodies, and we explore their roles in neutralising SARS-CoV-2, their persistence in convalescent individuals, and in reinfection. Furthermore, we also review the applications of neutralising antibodies in the clinical setting—from predictors of disease severity to serological testing to vaccinations, and finally in therapeutics such as convalescent plasma infusion.

Application of Current Hapten in the Production of Broad Specificity Antibodies Against Organophosphorus Pesticides

Diethylphosphono acetic acid （DPA） was used as a current hapten to generate broad specificity polycolonal antibodies against a group of organophosphorus pesticides. Six New Zealand white rabbits were immunized with immunogens synthesized by the active ester method （AEM） or 1-ethyl-3-（3-dimethylaminopropyl）-carbodimide method （EDC）. The titers of antisera reached 25 600 by AEM and 6 400 by EDC, respectively. Polyclonal antibodies raised against DPA were screened and selected for the competitive indirect enzyme-linked immunosorbent assay （CI-ELISA）. A CI-ELISA for DPA was developed with a detection limit of 3.536 ng mL^-1and an I50 value of 0.182 μg mL^-1. The assay specificity was evaluated by obtaining competitive curves for several structurally related compounds as competitors. The antiserum showed high affinities to chlorpyrifos, diazinon, omethoate, parathion-ethyl and profenofos with I50 of 0.12, 0.15, 0.21, 0.88, 0.97 and 2.5 μg mL^-1, respectively. The results indicate that the assay could be a screening tool for quantitation and semiquantitation determination of the above former five organophosphorus pesticides.

Generation of antibodies against disintegrin and cysteine-rich domains by DNA immunization: An approach to neutralize snake venom-induced haemorrhage

Objective: To explore whether a DNA immunization approach targeting the major haemorrhage molecule of a prothrombin activator-like metalloproteinase from Echis ocellatus(E. ocellatus) venom could be conceived to inspire antibodies with more prominent specificity and equal adequacy to current conventional antivenoms systems.Methods: The isolated DNA Eo MP-6 was used as the template for PCR amplification using the Eo DC-2-specific forward and reverse primers. A PCR product of approximately700 bp was obtained and cloned into p Sec Tag-B expression vector where anti-Eo DC-2antibodies were generated and analysed for their efficacy to neutralise local haemorrhage in vitro and in vivo.Results: Our results suggest that the generated anti-Eo DC-2 showed a remarkable efficacy by(a) interfering with the interaction of the recombinant disintegrin "Eo DC-2" isolated from the E. ocellatus as well as other viper species to the a2b1-integrins on platelets;(b) complete inhibition of the catalytic site of the metalloproteinase molecules in vitro using an adaptation antibody zymography assay. Furthermore, it has a polyspecific potential and constitutively expressed significant inhibition by cross-reaction and neutralised venom-induced local haemorrhage exerted by different viper species in vivo. The potential characteristic of Eo DC-2 against one part(the non-catalytic domain) as opposed to the whole molecule to neutralise its haemorrhagic activity is of crucial importance as it represents a novel approach with greater immunological specificity and fewer hazards, if any, than conventional systems of antivenom production, by exposure large animals that usually being used for the current antivenom production to a less injurious than expression of the whole molecule containing the catalytic metalloprotease domain. Hence, we report for the first time that our preliminary results hold a promising future for antivenom development.Conclusions: Antibodies generated against the E. ocellatus venom prothrombin activatorlike metalloprotease and disintegrin-cysteine-rich domains modulated and inhibited the catalytic activity both in vitro and in vivo of venom metalloproteinase disintegrin cysteine rich molecules. Thus, generating of venom specific-toxin antibodies by DNA immunization offer a more rational treatment of snake envenoming than conventional antivenom.