Solid-phase radioimmunoassay for antibodies to flavivirus structural and nonstructural proteins

Beyond the Gut: The intratumoral microbiome's influence on tumorigenesis and treatment response

The intratumoral microbiome (TM) refers to the microorganisms in the tumor tissues, including bacteria, fungi, viruses, and so on, and is distinct from the gut microbiome and circulating microbiota. TM is strongly associated with tumorigenesis, progression, metastasis, and response to therapy. This paper highlights the current status of TM. Tract sources, adjacent normal tissue, circulatory system, and concomitant tumor co-metastasis are the main origin of TM. The advanced techniques in TM analysis are comprehensively summarized. Besides, TM is involved in tumor progression through several mechanisms, including DNA damage, activation of oncogenic signaling pathways (phosphoinositide 3-kinase [PI3K], signal transducer and activator of transcription [STAT], WNT/β-catenin, and extracellular regulated protein kinases [ERK]), influence of cytokines and induce inflammatory responses, and interaction with the tumor microenvironment (anti-tumor immunity, pro-tumor immunity, and microbial-derived metabolites). Moreover, promising directions of TM in tumor therapy include immunotherapy, chemotherapy, radiotherapy, the application of probiotics/prebiotics/synbiotics, fecal microbiome transplantation, engineered microbiota, phage therapy, and oncolytic virus therapy. The inherent challenges of clinical application are also summarized. This review provides a comprehensive landscape for analyzing TM, especially the TM-related mechanisms and TM-based treatment in cancer.

Characterization of dengue virus complex-specific neutralizing epitopes on envelope protein domain III of dengue 2 virus

The surface of the mature dengue virus (DENV) particle is covered with 180 envelope (E) proteins arranged as homodimers that lie relatively flat on the virion surface. Each monomer consists of three domains (ED1, ED2, and ED3), of which ED3 contains the critical neutralization determinant(s). In this study, a large panel of DENV-2 recombinant ED3 mutant proteins was used to physically and biologically map the epitopes of five DENV complex-specific monoclonal antibodies (MAbs). All five MAbs recognized a single antigenic site that includes residues K310, I312, P332, L389, and W391. The DENV complex antigenic site was located on an upper lateral surface of ED3 that was distinct but overlapped with a previously described DENV-2 type-specific antigenic site on ED3. The DENV complex-specific MAbs required significantly higher occupancy levels of available ED3 binding sites on the virion, compared to DENV-2 type-specific MAbs, in order to neutralize virus infectivity. Additionally, there was a great deal of variability in the neutralization efficacy of the DENV complex-specific MAbs with representative strains of the four DENVs. Overall, the differences in physical binding and potency of neutralization observed between DENV complex- and type-specific MAbs in this study demonstrate the critical role of the DENV type-specific antibodies in the neutralization of virus infectivity.

Antigenic Structure of Flavivirus Proteins

The increased activity of Dengue virus in the tropical regions of the world and the recent movement of West Nile virus from the eastern to the western hemisphere emphasize the fact that vector-borne flaviviruses are medically important emerging infectious diseases. These facts warrant continued efforts to decode all facets of flavivirus immunology. This chapter reviews current understanding of the antigenic fine structure of flaviviral structural and nonstructural (NS) proteins and their involvement in B- an T-cell host responses. The virion structural glycoprotein E elicits both virus-neutralizing antibodies and antiviral Th-cell responses. Consistent with the current hypothesis of the MHC class I pathway of protein processing, immunodominant flaviviral Tc-cell epitopes mainly reside on the NS proteins. To prepare effective and inexpensive subunit vaccines, we will need to continue to better understand these structure-function relationships of flavivirus proteins.

An enzyme-linked immunosorbent assay using a chaotropic agent (sodium thiocyanate) for serotype specific reaction between crude dengue viral antigen and anti-dengue mouse antibody

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect serotype specific reaction between crude dengue viral antigen and anti-dengue mouse hyperimmunized antibody under the stringent condition in the presence of a Chaotropic agent, sodium thiocyanate (NaSCN), in the reaction mixture of antigen and antibody. Rapidly sedimenting hemagglutinin (RHA) derived from type 2 dengue virus-infected mosquito cell culture fluid reacted to the antibody for both type 2 and type 3 dengue viruses in the ELISA. In contrast, its reactivity was reduced after the addition of NaSCN in the ELISA. Soluble complement-fixing antigen (SCF) derived from type 2 dengue virus-infected mosquito cell culture fluid reacted serotype specifically to anti-dengue type 2 antibody, and was relatively stable for the NaSCN treatment in the ELISA. Anti-type 2 RHA mouse antibody reacted to both type 1 and type 2 dengue viral antigens and its reactivity was reduced after the addition of NaSCN in the ELISA. Anti-type 2 SCF antibody reacted serotype specifically to type 2 dengue viral antigen with and without NaSCN in the ELISA.

A novel method for increased yield of immunocompetent virus for vaccine production

Cultured human cells exposed to the pesticide emulsifier Atlox, 6 to 8 h prior to Infection with influenza A virus, increased virus production approximately 10-fold. Antibodies against the 'enhanced virus' neutralized plaque formation and reacted equally well with non-enhanced virus in serological tests (haemagglutination-inhibition and radioimmunoassays). The procedure has great potential in cutting costs of production for some virus vaccines.

Induction of protective immunity in animals vaccinated with recombinant vaccinia viruses that express PreM and E glycoproteins of Japanese encephalitis virus

A cDNA clone representing the genome of structural proteins of Japanese encephalitis virus (JEV) was inserted into the thymidine kinase gene of vaccinia virus strains LC16mO and WR under the control of a strong early-late promoter for the vaccinia virus 7.5-kilodalton polypeptide. Indirect immunofluorescence and fluorescence-activated flow cytometric analysis revealed that the recombinant vaccinia viruses expressed JEV E protein on the membrane surface, as well as in the cytoplasm, of recombinant-infected cells. In addition, the E protein expressed from the JEV recombinants reacted to nine different characteristic monoclonal antibodies, some of which have hemagglutination-inhibiting and JEV-neutralizing activities. Radioimmunoprecipitation analysis demonstrated that two major proteins expressed in recombinant-infected cells were processed and glycosylated as the authentic PreM and E glycoproteins of JEV. Inoculation of rabbits with the infectious recombinant vaccinia virus resulted in rapid production of antiserum specific for the PreM and E glycoproteins of JEV. This antiserum had both hemagglutination-inhibiting and virus-neutralizing activities against JEV. Furthermore, mice vaccinated with the recombinant also produced JEV-neutralizing antibodies and were resistant to challenge with JEV.

Antigenicity of Japanese encephalitis virus envelope glycoprotein V3 (E) and its cyanogen bromide cleaved fragments examined by monoclonal antibodies and Western blotting

Purified Japanese encephalitis (JE) virus was solubilized under reducing condition by using 2-merceptoethanol (2 ME) or nonreducing condition without 2 ME and its structural proteins were separated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS-PAGE), followed by the Western blotting using polyclonal and monoclonal antibodies against JE. The mobilities and reactivities against polyclonal antiserum of V3 (E) and V2 (C) were reduced when virion was disrupted under reducing condition. The 54 K band corresponding to V3 was treated with cyanogen bromide (CNBr) and analyzed by the second SDS-PAGE and Western blotting. By Coomassie Blue staining multiple bands of molecular weight ranging from 54 K to 8 K daltons were revealed for CNBr-treated V3. For the specimens disrupted under reducing condition, uncleaved 54 K and cleaved 8 K, 14 K, 45 K, and 48 K bands were reactive by one of the JE and Murray Valley encephalitis (MVE) crossreactive monoclonal antibodies (NARMA 16), while other monoclones did not show any reactivity. The uncleaved V 3 prepared under nonreducing condition was reactive with several monoclones to almost similar levels. After CNBr treatment, the antigenic epitope(s) for a flavivirus-common monoclone (NARMA 24) and those for NARMA 16 appeared to locate on different fragments, while the epitopes for other monoclones lost their antigenicities. These results indicate the importance of disulfide bond and highly organized structure to maintain some of the epitopes on V 3.

Monoclonal antibodies distinguish between wild and vaccine strains of yellow fever virus by neutralization, hemagglutination inhibition, and immune precipitation of the virus envelope protein

Nineteen monoclonal antibodies were produced to the 17D strain of yellow fever virus (17D YF). Virus-specific structural and nonstructural proteins were identified for 17D YF and for the parent wild Asibi YF by radioimmunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fourteen of the monoclonal antibodies were directed against the envelope glycoprotein, E, and five against the nonstructural protein gp 48. The E protein of 17D YF was resolved as a double complex whereas the E protein of Asibi YF appeared as a single band of slightly lower molecular weight. The only IgM anti-E antibody obtained precipitated and neutralized 17D YF specifically with no activity against Asibi YF. This antibody also distinguished clearly by neutralization (N) between the 17D-204 derived vaccine strain to which the animal had been immunized and 17D YF strains of different origin. All 13 IgG anti-E monoclonal antibodies had hemagglutination-inhibition (HI) activity to 17D YF and all but one neutralized Asibi YF; however, only 3 of the 13 neutralized 17D YF. Four anti-E antibodies cross-reacted with other flaviviruses by HI or HI and N. Three of the five anti-gp 48 antibodies had complement-fixation (CF) titers against 17D YF and Asibi YF but none had N or HI activity.

Topographical analysis of antigenic determinants on envelope glycoprotein V3 (E) of Japanese encephalitis virus, using monoclonal antibodies

Ten monoclonal antibodies directed against envelope glycoprotein V3 (E) of Japanese encephalitis virus were obtained. They were characterized by hemagglutination inhibition (HI), neutralization, and enzyme-linked immunosorbent assay and divided into four types: flavivirus-cross-reactive HI and non-neutralizing antibody (group 1), subgroup-specific HI and non-neutralizing antibody (group 2), low HI and neutralizing antibody (group 3), and non-HI and neutralizing antibody (groups 4 and 5, respectively). Competitive binding assays were performed to analyze the topography of antigenic determinants by enzyme-linked immunosorbent assay. The results of the competitive binding assay separated non-HI and neutralizing antibody into groups 4 and 5, respectively, and demonstrated the existence of at least five distinct antigenic determinants on V3. The site of group 1 was distinct from any other site. The sites of groups 2 and 3 seemed to be located close together. Our results suggest the following relationship between HI and neutralization: (i) The HI sites are separated from the neutralization sites, and (ii) there are two distinct HI sites, one of which is flavivirus cross-reactive, the other subgroup specific.

Evaluation of the solid-phase radioimmunoassay for diagnosis of St. Louis encephalitis infection in humans

Since the use of highly purified viral proteins in the solid-phase radioimmunoassay (SPRIA) procedure is not practical for routine diagnostic serology, the procedure was adapted for use with the crude antigens now commonly used to diagnose St. Louis encephalitis (SLE) virus infections. SLE and various other alpha- and flavivirus antigens were tested by both the SPRIA procedure and conventional serological methods. Standards were established for use of the crude antigens in the SPRIA procedure. Reproducibility of the procedure was similar to that of conventional tests. The SPRIA procedure specifically differentiated SLE from clinically similar alphaviruses, but did not differentiate SLE from related flaviviruses very well. SPRIA diagnosis of SLE infections by the immunoglobulin G response in paired sera was good. Generally, the crude antigen SPRIA procedure was as sensitive as the conventional serological tests, but not as specific.

Protease treatment and chemical crosslinking of a flavivirus: tick borne encephalitis virus

Tick-borne encephalitis virus was treated with pronase or thermolysin. The resulting particles were banded in sucrose gradients and analyzed for polypeptide composition. Both enzymes caused a reduction in particle density from 1.19 to 1.15--1.16 g/cm3. No loss of viral lipid or nucleic acid could be observed. SDS-polyacrylamidegel electrophoresis showed that only the core protein V2 was unchanged whereas the envelope proteins V3 and V1 had disappeared from their original positions in the PAGE profile. Instead a new peptide(s) with molecular weight of 4000--6000 was found in which hydrophobic amino-acids were enriched. Crosslinking by dimethyl-3.3'-dithiobispropionimidate (DTBP) made the virus resistent to solubilization of the envelope proteins by TX-100. This could be interpreted by the formation of a dense envelope protein network around the nucleocapsid preventing its liberation by TX-100. Some data however indicate that direct crosslinking of at least one of the envelope proteins with the core cannot be excluded.

Delayed-type hypersensitivity responses in mice infected with St. Louis encephalitis virus: kinetics of the response and effects of immunoregulatory agents

Labeled monocyte infiltration techniques have been used to study delayed-type hypersensitivity responses in mice immunized with St. Louis encephalitis virus. A delayed 24- to 48-h inflammatory response occurred 6 to 7 days after immunization. This response can be potentiated by cyclophosphamide treatment, by BCG administration, or by splenectomy. Treatments known to selectivity inhibit T-cell function suppressed the response.