ABSTRACT
With the advantages of low immunogenicity and long half-life, human monoclonal antibody has become an indispensable biological agent in vivo. Immortalization of human B cells is a potential and effective method to obtain natural human antibody library, which can provide a rich source for the preparation of human monoclonal antibodies. As there are urgent problems to be solved in each platform, the preparation of antibodies based on human B cell immortalization is still limited to the laboratory research stage. At present, there is a lack of a systematic review to clarify the advantages and disadvantages of the existing human B cell immortalization antibody preparation platform and its feasibility analysis. This paper reviews the research on the preparation of human monoclonal antibody based on human B cells immortalization, and describes an in vitro cell culture method, in which hCD40L vesicles are used instead of feeder cells, in order to provide references for the further development of human monoclonal antibody preparation technology.
Subject(s)
Humans , Antibodies, Monoclonal , B-Lymphocytes , Cell Culture TechniquesABSTRACT
Background & objectives: Infection with Salmonella enterica serovar Typhi (hereafter S. Typhi) is an important public health problem in India. There has been an increase in the number of reported clinical failures to ciprofloxacin treatment but the data on possible mechanism of failure are limited. One mechanism that has been widely reported and found associated with ciprofloxacin resistance, is the mutations in target genes in QRDR (quinolone resistance determining region). It is hypothesized that mutations in DNA gyrase or topoisomerase IV result in therapeutic failure under selective pressure of antibiotic while the patient is on treatment. We undertook in vitro sequential selection studies to expose the clinical isolates of S. Typhi to different concentration of ciprofloxacin to study the role of antibiotic selective pressure in the development of mutations in QRDR. Methods: Total 26 clinical isolates were divided in to two parts: part I included six isolates obtained from three patients with relapse of enteric fever and part II included 20 isolates with different ciprofloxacin MIC levels. For in vitro induction of mutation experiment, five S. Typhi isolates were selected which included three NAS (nalidixic acid sensitive) and 2 NAR (nalidixic acid resistant) S. Typhi. These isolates were grown under increasing concentrations of ciprofloxacin and mutations acquired in QRDR of DNA gyrase (gyrA and gyrB) and topoisomerase IV (parC and parE) were investigated by sequencing. Results: For the isolates included in the part I of the study, it was found that the MIC to ciprofloxacin increased in the isolates obtained during the relapse of enteric fever as compare to the first isolate. All isolates had single mutation in gyrA gene at S83 without additional mutation in the second isolate. In the second part of the study, the nine isolates with varying MICs to ciprofloxacin also had single mutation in gyrA gene at S83 and another six had triple mutations, two mutations in gyrA gene (at S83 and D87) and one mutation in parC gene (at S80). In in vitro induction of mutation experiment, all mutated isolates showed triple mutation (two mutation in gyrA and one in parC gene) while no mutations were found in wild isolates. Interpretation & conclusions: Upon exposure to the step-wise increased concentration of ciprofloxacin, isolates become more tolerant to the ciprofloxacin and showed 2-4 fold higher MICs without new mutation after 8 μg/ml. So the accumulation of mutations under continuous ciprofloxacin pressure and tolerance of the mutant isolates led to the clinical failure. These results also suggested that there could be another mechanism responsible for resistance.
ABSTRACT
Objective: In order to find the suitable concentration and combination of plant growth regulators, the effects of plant growth regulators (NAA, 2, 4-D, 6-BA, KT, and PP333) on in vitro induction formation for the plantlet microtuber of Dioscorea bulbifera was studied. Methods: Through plant tissue culture technique, single factor test, and orthogonal test, taking the stems with a bud of D. bulbifera plantlets as explants, the effects of plant growth regulators on the in vitro induction formation for the microtubers of D. bulbifera were investigated. Results: Auxin using alone was conducive to the induction formation for the microtuber of D. bulbifera. The suitable concentration of both NAA and 2, 4-D inducing the microtuber formation was 0.5 mg/L, but the inducing effects of NAA and 2, 4-D had no significant difference. Cytokinin using alone was not conducive to the induction formation for the microtuber of D. bulbifera. The suitable concentration of both KT and 6-BA inducing microtuber formation was 2 mg/L, but the inducing effect of KT is better than that of 6-BA. The combination of auxin, cytokinin, and PP333 could significantly promote the in vitro induction formation for the microtuber of D. bulbifera, the better combination was MS+NAA 0.5 mg/L+6-BA 2.0 mg/L+PP333 0.5 mg/L. Conclusion: Based on these experimental results, the paper selects the suitable concentration of plant growth regulators conducive to the in vitro induction formation for the microtuber of D. bulbifera, which has laid the technical foundation for their in vitro induction formation of microtuber and factory production.
ABSTRACT
Objective Antibiotic resistance has increasingly been recognized as the major cause of treatment failure for Helicobacter pylori infection. The study was designed to compare the propensity of Helicobacter pylori to develop in vitro resistance to five commonly used antibiotics and to investigate the rates of resistance to these five antibiotics. Methods The serial passage tests were done in 7 sensitive Helicobacter pylori strains (2 type strains and 5 clinical isolates) to induce the resistance to amoxycillin, tetracycline, furazolidone, metronidazole or clarithromycin in vitro. The agar dilution tests detecting the minimal inhibitory concentration (MIC) were performed in 165 strains of Helicobacter pylori isolated from 2000 to 2001 to determine the resistance rates to the 5 antibiotics mentioned above. Results Serial passage tests showed that 5 of 7 strains of Helicobacter pylori were induced to be resistant to metronidazole and tetracycline; the inducible multiple of metronidazole was the highest. No strain was induced to be resistant to clarithromycin, but the inducible multiple of one strain was relatively high. No strain was induced to be resistant to amoxycillin or furazolidone, and the inducible multiple of furazolidone was the lowest. The resistance rates of Helicobacter pylori to metronidazole, clarithromycin, amoxycillin, tetracycline and furazolidone were 49.7% (82/165), 7.3%(12/165), 1.2% (2/165), 2.4%(4/165) and 1.2%(2/165), respectively. Conclusions Our study indicate that it is quite easy to induce the resistance to metronidazole,not difficult to clarithromycin, and relatively difficult to furazolidone or amoxycillin. The relative degree of difficulty in inducing the resistance to the drugs other than tetracycline is associated with the resistance rates detected, the fact that may help predict the changing trend of resistance rates in general population.