ABSTRACT
The aim of this work was to study the Polymerase Chain Reaction (PCR) as a tool of quality control of bovine sera and cellular cultures used in the biotechnological industry. A total of 46 samples of bovine sera derived from two slaughterhouses and 33 samples of BHK21 cells derived from two biotechnological industries were evaluated using the primers GPO-3 (sense) and MGSO (antisense). The PCR technique sensibility analysis showed that 280 bp were amplified for the quantities of 50 ng to 0.006 ng of Micoplasma DNA. The primers specificity was confirmed in the test using Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Candida albicans; except by the positive control, none of the samples showed amplification. The presence of Mycoplasma in bovine sera and in the cultures of BHK21 cells showed that 56.5 and 15.2%, respectively, were contaminated. Thus, it was possible to conclude that PCR was a fast and confident technique to detect mycoplasma and that it could be used to control the quality of immunobiological products and inputs, such as sera and cultures of BHK21 cells.
ABSTRACT
Estudios previos han demostrado que la adaptación de diversos virus a crecer en líneas celulares de vertebrados, conduce a la selección de variantes virales que unen al heparán sulfato (HS) con alta afinidad. En el presente trabajo se determinó la susceptibilidad de cepas del virus dengue (DENV) a la heparina hipersulfatada un análogo al HS, después de pases seriados en células BHK-21. A aislados de campo de los cuatro serotipos de DENV, se les realizaron ocho pases seriados en células BHK-21. La adaptación de los DENV al cultivo celular seleccionó variantes virales con una aumentada capacidad replicativa en células BHK-21 y una incrementada susceptibilidad a la heparina, en relación a las respectivas cepas no adaptadas, obteniéndose una inhibición de la infectividad más significativa en DENV-2 y DENV-4. Las cepas de DENV adaptadas presentaron cambios en la secuencia de aminoácidos de la proteína de envoltura (E), en particular una substitución K204R para DENV-1, N67K para DENV-2, K308R y V452A para DENV-3 y E327G para DENV-4. Estas sustituciones implicaron ganancia de residuos básicos que incrementaron la carga neta positiva de la proteína. Los resultados sugieren, que la adaptación de cepas de DENV a células BHK-21 selecciona variantes virales sensibles a la heparina y que la efectividad de este compuesto varía dependiendo de la cepa viral. Además sugieren que el HS puede jugar un papel importante en la infectividad de las cepas de DENV adaptadas al cultivo celular, a diferencia de los aislados de DENV no adaptados.
Several studies have shown that adaptation of various viruses to grow in certain cell lines of vertebrates, leads to the selection of virus variants that bind heparan sulfate (HS) with high affinity. In this study we investigated the susceptibility of strains of dengue virus (DENV) to oversulfated heparin an analogue of HS after passages in BHK-21 cells. Field isolates of the four serotypes of DENV with a limited number of passes in mosquito cells C6/36HT were serially passaged eight times in BHK-21 cells. The adaptation of the DENV to the cell culture selected viral variants with an increased replicative capacity in BHK-21 cells and an increased susceptibility to heparin compared with the original not adapted strains, with a more significant inhibition of the infectivity in DENV-2 and DENV-4.The E protein of the adapted strains showed changes in the amino acid sequence, particularly at the position K204R to DENV-1, N67K to DENV-2, K308R and V452A for DENV-3 and E327G to DENV-4. These substitutions implicated a gain of basic residues that increased the net positive charge of the protein. These results suggest that adaptation of DENV strains to BHK-21 cells implies changes in the envelope protein, changes associated to the protein reactivity with heparin, the inhibitory effectiveness of this compound varying depending on the viral strain. In addition, these results suggest that the HS can play an important role in the infectivity of the DENV strains adapted to vertebrate cell culture, but not in the infectivity of non-adapted DENV isolates.
Subject(s)
Animals , Cricetinae , Dengue Virus/drug effects , Heparin/pharmacology , Selection, Genetic , Viral Envelope Proteins/genetics , Aedes/cytology , Cell Line , Chlorocebus aethiops , Dengue Virus/growth & development , Kidney/cytology , Mesocricetus , Models, Molecular , Mutation , Mutation, Missense , Protein Binding , Protein Conformation , RNA, Viral/genetics , Sequence Analysis, RNA , Vero Cells , Viral Plaque Assay , Virus Cultivation , Virus Replication , Viral Envelope Proteins/chemistry , Viral Envelope Proteins/physiologyABSTRACT
Objective To construct a eukaryotic expressing vector harboring human DC-SIGN, and establish a BHK21 cell line stably and highly expressing DC-SIGN. Methods The DC-SIGN gene fragment which contained Not I and BamH I sites was amplified by PCR from pUNO-hDCSIGN1Aa plasmid, digested with Not I and BamH I, and then cloned into an eukaryotic expression vector pIRES-neo to construct eukaryotic expression vector pIRES-neo-DC-SIGN. The recombined plasmid was identified with Not I and BamH I enzyme digestion and sequencing, the latter was then transfected to BHK21 cells by LipofectamineTM 2000. After screening culture by G418, BHK21 cell line stably expressing DC-SIGN was established. The expression of DC-SIGN was identified by flow cytometry, Western blotting and immunofluorescence method. Results The gene sequence of DC-SIGN was consistent with that of design. PCR and double enzyme digestion analysis showed that the recombinant plasmid pIRES-neo-DC-SIGN was constructed successfully. After transfection, positive clones were selected with G418. After limiting dilution assay, BKH21 cell lines stably expressing DC-SIGN were established. The detection result of flow cytometry showed that the expression ratio of DC-SIGN positive clones was close to 90%. The result of immunofluorescence displayed that the expression of DC-SIGN was mostly located on the surface of cell membrane. Western blotting displayed the specific band of DC-SIGN protein. It showed that the BHK21 cells stably expressing DC-SIGN were successfully established. Conclusion DC-SIGN eukaryotic expression vector has been successfully constructed. The successful establishment of BHK21 cell lines which can stably express DC-SIGN provides a substantial foundation for further study on the DC targeting vaccines.