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@#Objective To compare three methods for detection of antibody level in serum immunized with SARS-CoV-2mRNA vaccine. Methods Enzyme-linked immunosorbent assay(ELISA),pseudo virus-based neutralization assay(PBNA)and micro-cytopathic effect neutralization test(MCPENT)were used to detect the antibody levels of a total of 120 serum samples(40 before immunization and 80 after immunization)before and after 2 doses of mRNA vaccine immunization,and the consistency and correlation of the three methods were analyzed. Results The consistency rates of the three methods detecting 120 serum samples were all over 90%,the Kappa coefficients were all more than 0. 7,and each P was less than0. 01. The correlation coefficient(r)between the antibody potency results of positive serum samples detected by the three methods was 0. 825～0. 902,and each P was less than 0. 01. Conclusion The three methods have good consistency and correlation in detecting antibody level of serum immunized with SARS-CoV-2 mRNA vaccine.
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Objective:To study the protective effects of bicistronic DNA vaccines carrying herpes simplex virus type 2 glycoprotein D (HSV-2 gD) and adjuvant CCL28 sequences that were connected by internal ribosome entry site (IRES) sequence in mouse model.Methods:The recombinant DNA vaccines, pgD-IRES-CCL28 and pCCL28-IRES-gD, encoding HSV-2 gD and adjuvant CCL28 were constructed with IRES sequence. After verified by sequencing, they were intramuscularly injected twice into BALB/c mice. Serum samples and vaginal lavage fluids were collected regularly. Splenocytes, mesenteric lymph node cells and rectal mucosa tissues were separated and collected. The titers of antigen-specific antibodies in immunized mice were analyzed with end-point ELISA. In vitro neutralization assay was used to measure neutralizing antibody titers in serum and vaginal lavage fluid after vaccination and virus challenge. CCL28-responsive immune cells in splenocytes, mesenteric lymph node cells and rectal tissues were detected by chemotaxis experiment and immunohistochemical staining. The protective effects of the bicistronic DNA vaccines were evaluated by fluorescent quantitative PCR, weighing and disease severity assessment. Humoral and cellular immune responses induced by the bicistronic DNA vaccines and their efficacy in immunoprotection were analyzed by comparing with pgD+ pCCL28 group. Results:IgG titers in serum samples and IgA antibody titers in vaginal lavage fluids of mice immunized with pCCL28-IRES-gD were similar to those in pgD+ pCCL28 group. The neutralizing ability of antibodies, the number of rectal mucosal IgA+ plasma cells and CCL28-responsive immune cells in mucosal tissues were increased in pCCL28-IRES-gD group. Serum neutralizing antibodies were not produced immediately in the mice challenged with HSV-2, but no weight loss, disease symptoms or death was observed. However, pgD+ pcDNA3.1 and pgD-IRES-CCL28 were ineffective against HSV-2 infection in mice.Conclusions:The recombinant bicistronic DNA vaccine of pCCL28-IRES-gD could induce stronger mucosal immune response in mice and provide better protective effects.
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Objective:To compare the immune responses to simply mixed and fused recombinant DNA vaccines of herpes simplex virus type 2 glycoprotein D (HSV-2 gD) and molecular adjuvant CCL19 in mice and to evaluate the protective effects.Methods:Gene recombination technology was used to construct recombinant DNA vaccines expressing HSV-2 gD and CCL19 alone or fused together. After verification by sequencing, Western blot and ELISA, BALB/c mice were immunized twice by intramuscular injection. Serum samples and vaginal lavage fluids were collected regularly after immunization. Splenocytes, mesenteric lymph node cells and rectal tissues were collected after immunization. Differences in humoral and cellular immune responses to the two forms of vaccines and their protective effects in mice were analyzed using end-point ELISA, in vitro neutralization assay, immunohistochemical staining, chemotaxis assay, vaginal virus challenge, fluorescence quantitative PCR, weighing and disease severity assessment. Results:The fused recombinant pgD-IZ-CCL19 plasmid could express gD protein and CCL19 protein in vitro, but the level of expressed CCL19 protein by pCCL19-IZ-gD plasmid was less than that by pgD-IZ-CCL19. The mice immunized with pgD-IZ-CCL19 showed higher levels of IgG in sera and IgA in vaginal lavage fluids ( P<0.01) and stronger neutralization ability than the mice vaccinated with pgD+ pCCL19. Compared with other groups, more lymphocytes were recruited in the rectal mucosa, the spleen and mesenteric lymph nodes of mice immunized with pgD-IZ-CCL19. Weight loss or disease symptoms were not observed in the pgD-IZ-CCL19 group after virus challenge. In addition, the positive rate of HSV-2 in vaginal mucosa and the mortality rate in the pgD-IZ-CCL19 group were the lowest. However, pCCL19-IZ-gD turned out ineffective in preventing HSV-2 infection. Conclusions:The fused recombinant DNA vaccine pgD-IZ-CCL19 could induce stronger immune responses in mice and provide better protective effects, which was superior to the simply mixed DNA vaccine.
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Objective:To improve the consistency of test results through reducing inter-laboratory variation in SARS-CoV-2 antibody detection with WHO SARS-CoV-2 antibody candidate international standard (IS, sample G) and antibody reference panel (samples E, F, H, I, J).Methods:Ten WHO samples (A-J) including the candidate IS and reference panel were evaluated using different methods, such as microneutralization tests based on live SARS-CoV-2, pseudovirus neutralization assay and commercial ELISA kits. The test results were compared using statistical analysis.Results:Using IS (sample G) as a reference, the relative concentrations of other samples could be determined with less variation. ELISA and pseudovirus neutralization assay had consistent results with those obtained with the microneutralization test based on SARS-COV-2 strain HB02. Weakly positive samples could be detected only by a certain kit.Conclusions:The availability of an IS for antibodies would facilitate the standardization of SARS-CoV-2 antibody detection methods. The reference panel fitted all the assays based on the SARS-CoV-2 prototype Wuhan strain. Pseudovirus neutralization assay and ELISA could be used as alternatives to live SARS-CoV-2-based neutralization test to some extent.
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Objective: To establish a pseudovirus reporting system was established for anti-WNV drug screening in order to by-pass security risk caused by live viruses in West Nile virus(WNV)research. Methods: 293T Cells were co-transfected with WNV replicon recombinant plasmid prWNV-Rluc containing Renilla luciferase reporter gene and recombinant plasmid pcDNA3.1-CME expressing WNV structural proteins C, M and E;and the cell culture supernatant containing pseudovirus was obtained at 72 h post-cotransfection. Results: After pseudovirus infection with the supernatant, BHK21 cells produced fluorescence with the intensity that increased dose-dependently with the supernatant containing pseudovirus. The WNV NS1 Protein expressed in the infected BHK21 cells was identified by Western blot, confirming the presence of WN pseudovirus in the supernatant. Neutralization assay showed that the WNV neutralizing antibody could effectively block the infection of BHK21 cells by the WN pseudovirus in the supernatant. Conclusion: The West Nile pseudovirus reporting system established in this study might be used without the biosafety level 3 laboratory (BSL-3) and could be applied to the screening of anti-WNV drugs.
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Rift Valley fever (RVF) is an acute, febrile zoonotic disease that is caused by the RVF virus (RVFV). RVF is mainly prevalent on the Arabian Peninsula, the African continent, and several islands in the Indian Ocean near southeast Africa. RVFV has been classified by the World Organisation for Animal Health (OIE) as a category A pathogen. To avoid biological safety concerns associated with use of the pathogen in RVFV neutralization assays, the present study investigated and established an RVFV pseudovirus-based neutralization assay. This study used the human immunodeficiency virus (HIV) lentiviral packaging system and RVFV structural proteins to successfully construct RVFV pseudoviruses. Electron microscopy observation and western blotting indicated that the size, structure, and shape of the packaged pseudoviruses were notably similar to those of HIV lentiviral vectors. Infection inhibition assay results showed that an antibody against RVFV inhibited the infective ability of the RVFV pseudoviruses, and an antibody neutralization assay for RVFV detection was then established. This study has successfully established a neutralization assay based on RVFV pseudoviruses and demonstrated that this method can be used to effectively evaluate antibody neutralization.
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Animals , Africa , Blotting, Western , HIV , Indian Ocean , Islands , Methods , Microscopy, Electron , Product Packaging , Rift Valley fever virus , Rift Valley Fever , ZoonosesABSTRACT
Objective To establish neutralization assay based on H5N1 avian influenza pseudotyped virus in vitro and to evaluate neutralizing titer of convalescent serum from 2 patients with H5N1 avian influenza.Methods pHR-Luc,pCMV△8.2 and CMV/R-SH or CMV/R-TH were cotransfected into 293T cell by co-precipitation with calcium phosphate.Pseudotyped virus supernatant was harvested 72 h posttranofection and identified the expression of HA and P24 by Western blot,and then we analyzed infective activity of 200 μL supernatant of pseudotyped virus.293T cell integrated HA was prepared and anti-HA antibodies in convalescent serum were measured with FACS assay.Neutralizing titers of convalescent serums against Shenzhen and Thailand pseudotyped virus were determined based on calculating IC50 with neutralizing assay.Results Pseudotyped virus involved P24 and HA,and precursor protein HA0 could cleavage into HA1 and HA2 with biological activity.Pseudotyped virus possessed better infective activity,and RLA value was about 2 × 104 with 200 μL supernatant.Both convalescent serums contained anti-HA antibodies and had cross-reactivity against different virus clades with FACS assay.Both convalescent serums had neutralizingactivity and could cross-neutralize different virus clades.However,both serums'neutralizing titers against Shenzhen virus were higher than Thailand.Conclusion We successfully constructed infectious pseudotyped virus which integrated HA of Shenzhen or Thailand virus,and it could be used for evaluation of serum neutralizing activity fast,efficiently and safely with broadly application prospect.
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Objective To pan and characterize anti-HIV-1 Fab by the phage antibody library technology. Methods Total RNA were extracted from lymphocytes which were isolated from peripheral blood collected from asymptomatic HIV-1 infected donors with high titer antibody against HIV-1. The genes of heavy chains Fd fragment and light chains of antibody were amplified by RT-PCR. The phagmids pComb3X cloned Fd and light chain genes were transformed into E. coli XL1-Blue by electroporation to construct phage Fab library. By three runs of "absorption-elution-neutralization-enrichment", the clones were induced by IPTG and characterized by ELISA. The positive clones were sequenced and analyzed the sequences. Subsequently, Fab antibodies of these positive clones were induced to expressed and purified, then the recombinant virus neutralization assay was performed. Results A phage Fab library was constructed with 8×106 members, and 11 positive clones were obtained by detecting IPTG-induced-expressing Fabs with ELISA. By analysis of the sequences, 10 light chain genes and 8 Fd genes were ensured to be obtained. Compared with the genes of anti-HIV-1 antibodies in HIV sequence database, the gene sequences we obtained were highly homologous to some patent genes of anti-HIV-1 gp120 antibodies in HIV sequence database( light chains with 60%-90% identity, Fd with 71%-85% identity); The CDRs of these positive clones were determined by comparing the positive clone genes with antibodies' genes in V base database, furthermore, CDRH3 of these positive clones has the length of 12-22 aa. Strand shift had little effect to improving affinity of our Fab clones. Fab antibodies were induced to express at the concentration of ＞ 10 mg/L. Three Fab antibodies neutralize HIV-1 virus to some extent. Conclusion The studies will provide the basis on further study on the anti-HIV-1 Fabs obtained successfully.
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Aino virus infection is characterized by abortion, stillbirth, and congenital abnormalities such as arthropgryposis-hydranencephaly syndrome in calves. In Korea, Aino virus infection was first reported in 1997 by researchers who were investigating the cause of newborn calf deformities. Given the incidence of Aino-related deformities, the need for a study of the Aino virus infection status in Korea was recognized. In this study, we investigated the nationwide seroepidemiological status of Aino virus infection. A total of 9,921 serum samples collected between 1993 and 2001, and 23,760 serum samples between 2002 and 2007 were tested using a virus neutralization assay. The seroprevalence of Aino virus was 73.1, 63.8, 44.9, 56.0, 38.5, 28.4 18.3, 19.6, and 23.2%, respectively, between 1993 and 2001, and 43.8, 42.9, 50.7, 55.3, 31.4, and 25.4%, respectively, between 2002 and 2007. Aino virus infection does not pose a major threat to the bovine industry in Korea till now. The future prospects for Aino virus infection in cattle, however, may change with the global warming phenomena. The results of this study may serve as a basis for future epidemiological studies on Aino virus infection.
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Animals , Cattle , Humans , Infant, Newborn , Congenital Abnormalities , Epidemiologic Studies , Global Warming , Incidence , Korea , Seroepidemiologic Studies , Stillbirth , VirusesABSTRACT
Many flaviviruses are emerging and reemerging pathogens, such as West Nile virus (WNV), dengue virus (DENV), yellow fever virus (YFV), and Japanese encephalitis virus. Serological assay is the dominant method for diagnosis of flavivirus infections in human. Because antibodies generated during flavivirus infections cross-react with other flavivirus members, plaque reduction neutralization test (PRNT) is the only available assay to determine the infecting flavivirus type.Since PRNT requires culturing raw viruses, it must be performed in biosafety level-3 or level-4 containment for many flaviviruses, and takes more than ten days to complete. To overcome these problems, we have developed flavivirus viral-like particles (VLPs) that could be used to replace raw viruses in the neutralization assay. The VLPs were prepared by trans packaging a luciferase-reporting replicon with viral structural proteins. This novel assay involves three simple steps: (ⅰ) VLPs from a panel of flaviviruses are incubated with flavivirus-infected sera at 37℃ for 1 h; (ⅱ)the neutralized VLPs are used to infect Vero cells; and (ⅲ) the infected cells are measured for luciferase activities at 22 h post-infection. The virus type whose VLP is most efficiently neutralized by the serum specimen (as quantified by the luciferase activities) is the etiologic agent. As a proof-of-concept, we show that a WNV-infected mouse serum neutralized the WNV VLP more efficiently and selectively than the DENV and YFV VLPs. Our results demonstrate that the VLP neutralization assay maintains the "gold standard" of the classic PRNT; importantly, it shortens the assay time from ＞10 days to ＜1 day, and can be performed in biosafety level-2 facility.
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Objective To study the influence of site-directed deglycosylation of the HIV-1 envelope (Env) on its immunogenicity and assembly of functional pseudovirus. Methods Site-directed deglycosylation were performed using cycling mutagenesis and selection of mutants with DpnⅠ. Single-cycle infection assay was employed to analyze the effect of the mutations on the ability of functional pseudovirus assembly. The influence of deglycosylations on the immunodeficiency of Env was evaluated using pseudovirusbased neutralization assay and ELISPOT assay. Results Mutant N197Q induced higher neutralization activities for both pseudoviruses, but lower Env-specific T-cell response. And N197Q rendered the Env to lose the ability of functional pseudovirus assembly. Mutant G2 induced higher neutralization activities for pseudovirus 74-2 but lower for pseudovirus Wt, and had almost no influence on Env-specific T-cell response and functional pseudovirus forming. Conclusion The site-directed deglycosylation of the HIV-1 Env affects the pseudovirus forming and its immunogenicity.
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Eleven env mutants were designed and generated by site-directed mutagenesis of the regions around Nab epitopes and deletions of variable regions in env.The immunogenicities of the generated mutants were evaluated using single-cycle infection neutralization assays with two pseudoviruses and IFN-γELISPOT.Overall,five mutants(dWt,M2,M5-2,M5-1 and dM7)induced highed neutralization activities for both pseudoviruses than plasmid Wt,while only two of the mutants(dWt and M5-2)showed significant differences(P<0.05).Two mutants(M2 and dM2)induced more Env-specific T cells than plasmid Wt.Statistically however,significance was only reached for mutant M2.Thus,properly modified HIV-1 Env may have the potential to induce potent cellular and humoral immune responses.