Fast conversion of scFv to Fab antibodies using type IIs restriction enzymes.

Single chain variable fragment (scFv) antibody libraries are widely used for developing novel bioaffinity reagents, although Fab or IgG molecules are the preferred antibody formats in many final applications. Therefore, rapid conversion methods for combining multiple DNA fragments are needed to attach constant domains to the scFv derived variable domains. In this study we describe a fast and easy cloning method for the conversion of single framework scFv fragments to Fab fragments using type IIS restriction enzymes. All cloning steps excluding plating of the Fab transformants can be done in 96 well plates and the procedure can be completed in one working day. The concept was tested by converting 69 scFv clones into Fab format on 96 well plates, which resulted in 93% success rate. The method is particularly useful as a high-throughput tool for the conversion of the chosen scFv clones into Fab molecules in order to analyze them as early as possible, as the conversion can significantly affect the binding properties of the chosen clones.

Phage display aided improvement of a unique prostate-specific antigen (PSA) antibody unreactive with Lys(145)-Lys(146) internally cleaved forms.

Prostate specific antigen (PSA) is a commonly used marker of prostate cancer. A panel of four kallikrein immunoassays has been reported to improve the prediction of prostate biopsy outcome (cancer vs benign) in men with elevated PSA in the circulation. Assay of one of the kallikrein forms, intact free PSA (fPSA-I), is based on a unique monoclonal antibody (4D4), which is specific for PSA without the internal cleavage at Lys(145)-Lys(146). Due to high dissociation rate the 4D4 antibody is less than optimal for achieving a highly sensitive robust assay. In this study, we cloned the 4D4 Mab into a recombinant fragment (Fab) format and constructed three mutant libraries with the aim to increase its binding affinity. The libraries contained targeted mutations either in the CDR-H1, CDR-H2 or CDR-L3 region. PSA-I specific antibodies were enriched from the libraries by phage display technology. We identified fourteen unique clones with 1-5 mutated amino acids showing reduced dissociation of the PSA conjugate compared to the wt-4D4 Fab. Five of these mutant antibodies had 2-6 times higher binding affinity compared to the wt-4D4 Fab yet retaining the original specificity for PSA-I. The analytical sensitivity of fPSA-I assay with mutant L3-2 Fab was 0.12 µg/L compared to 4.46 µg/L with the original wt-4D4 Fab. In the method comparison study, the developed assay showed an excellent correlation to the existing fPSA-I assay. The high affinity and specificity of these mutant antibodies have potential to provide sensitive and robust detection of intact and nicked PSA from patient samples in different test formats.

Comparison of polyethylene glycol with and without electrolytes in the treatment of constipation in elderly institutionalized patients: a randomized, double-blind, parallel-group study.

BACKGROUND: Polyethylene glycol (PEG) is a commonly used osmotic laxative. PEG with electrolytes is mixed with water, but PEG without electrolytes can also be mixed with, for example, juice, coffee or tea, making it more palatable. Laxatives, including PEG, are commonly used by the elderly, particularly those living in institutions. Few clinical studies, however, have investigated the use of PEG in this population. OBJECTIVE: To test whether PEG 4000 without electrolytes (hypotonic PEG) is at least as effective and safe as PEG 4000 with electrolytes (isotonic PEG) in elderly institutionalized constipated patients. The acceptability of the treatments was also compared. METHODS: This randomized, double-blind, parallel-group study was conducted at ten private assisted-living facilities or communal nursing homes in Finland. Eligible patients were required to have used isotonic PEG at a stable dose without any other treatment for constipation (except for Plantago ovata seeds) for at least 2 weeks prior to a run-in period. After the 1-week run-in, 62 patients (mean age 86 years; range 66-99 years) were randomly either switched to receive hypotonic PEG or continued to receive isotonic PEG, both dissolved in water, 12 g once or twice daily or once every other day, for 4 weeks. Stool frequency, stool consistency, stool straining and gastrointestinal symptoms were recorded. Safety laboratory tests were conducted before and after the treatment period. Acceptability was assessed at the end of the study. RESULTS: At week 4, mean (SD) weekly stool frequencies in the hypotonic and isotonic PEG groups were 8.5 (4.5) and 8.4 (3.6), respectively. The mean stool frequency ratio (95% CI) was 0.90 (0.74, 1.10); thus, the PEG products were considered equally effective. At week 4, the proportion of patients with soft or normal stool consistency was higher in the hypotonic PEG group than in the isotonic PEG group (70% vs 52%), but this difference was not statistically significant. There were no differences between the groups in stool straining or gastrointestinal symptoms. In the safety laboratory tests, no clinically significant differences between the groups were detected, although plasma sodium level was statistically significantly lower in the hypotonic PEG group at the end of the study (137.7 vs 138.9 mmol/L, respectively; p = 0.012). Most patients were willing to continue their study treatment (85% in the hypotonic PEG and 63% in the isotonic PEG group; p = 0.070). Compared with only 12% of the patients receiving hypotonic PEG, however, 31% of the patients in the isotonic PEG group rated the taste of the study treatment as bad or very bad (p = 0.101). CONCLUSION: Hypotonic PEG solution is as effective as isotonic PEG in the treatment of constipation in elderly institutionalized patients. Both treatments appear safe, well tolerated and, when dissolved in water, well accepted by the majority of the patients. When desired, switching from isotonic to hypotonic PEG can safely take place in elderly individuals without compromising efficacy.