Diagnostic and Epitope Mapping Potential of Single-Chain Antibody Fragments Against Foot-and-Mouth Disease Virus Serotypes A, SAT1, and SAT3

Foot-and-mouth disease (FMD) affects cloven-hoofed domestic and wildlife animals and an outbreak can cause severe losses in milk production, reduction in meat production and death amongst young animals. Several parts of Asia, most of Africa, and the Middle East remain endemic, thus emphasis on improved FMD vaccines, diagnostic assays, and control measures are key research areas. FMD virus (FMDV) populations are quasispecies, which pose serious implications in vaccine design and efficacy where an effective vaccine should include multiple independent neutralizing epitopes to elicit an adequate immune response. Further investigation of the residues that comprise the antigenic determinants of the virus will allow the identification of mutations in outbreak strains that potentially lessen the efficacy of a vaccine. Additionally, of utmost importance in endemic regions, is the accurate diagnosis of FMDV infection for the control and eradication of the disease. To this end, a phage display library was explored to identify FMDV epitopes for recombinant vaccines and for the generation of reagents for improved diagnostic FMD enzyme-linked immunosorbent assays (ELISAs). A naïve semi-synthetic chicken single chain variable fragment (scFv) phage display library i.e., the Nkuku ^® library was used for bio-panning against FMD Southern-African Territories (SAT) 1, SAT3, and serotype A viruses. Biopanning yielded one unique scFv against SAT1, two for SAT3, and nine for A22. SAT1 and SAT3 specific scFvs were exploited as capturing and detecting reagents to develop an improved diagnostic ELISA for FMDV. The SAT1 soluble scFv showed potential as a detecting reagent in the liquid phase blocking ELISA (LPBE) as it reacted specifically with a panel of SAT1 viruses, albeit with different ELISA absorbance signals. The SAT1svFv1 had little or no change on its paratope when coated on polystyrene plates whilst the SAT3scFv's paratope may have changed. SAT1 and SAT3 soluble scFvs did not neutralize the SAT1 and SAT3 viruses; however, three of the nine A22 binders i.e., A22scFv1, A22scFv2, and A22scFv8 were able to neutralize A22 virus. Following the generation of virus escape mutants through successive virus passage under scFv pressure, FMDV epitopes were postulated i.e., RGD+3 and +4 positions respectively, proving the epitope mapping potential of scFvs.

Improving the characteristics of a mycobacterial 16 kDa-specific chicken scFv

Recombinant antibodies can be engineered to improve their binding or other characteristics. A chicken single chain variable fragment (scFv) phage display library was panned against the mycobacterial 16 kDa antigen. Three fusion phages which bound specifically to the antigen were selected, each of which produced low signals in ELISA when secreted as a soluble scFv. One scFv was therefore chosen to be modified in an attempt to improve its binding. Firstly, a mutant sublibrary was created by random mutagenesis. High stringency panning of this sublibrary yielded binders which produced ELISA signals up to eleven times higher than the parent scFv. An increase in the intrinsic affinity was confirmed by surface plasmon resonance. Secondly, the flexible linker between the heavy and light chains of the parent scFv was either shortened to one glycine residue or deleted entirely. No ELISA signal was obtained when the linker was absent, but the glycine-linked scFv showed enhanced binding. Size exclusion chromatography revealed that the enhanced binder had aggregated to form tetramers. This study confirms that the strategies used to improve the binding of human and mouse scFvs can also enhance chicken scFvs.

[Choroid melanoma. A retrospective randomized comparative study of ruthenium irradiation vs enucleation]

A randomized retrospective study concerning survival of Ruthenium treatment and enucleation in melanoma patients has been performed. For 112 patients from Hamburg who underwent Ruthenium therapy individual match partners were selected in Copenhagen where during the same period of time enucleation was the standard procedure. Selection took place concerning patient's age and sex at the time of treatment, initial tumor volume and the time of treatment. The present status of the patients was not known during the selection process. During the observation time of 12 years there was a survival rate after irradiation of 77.9% and after enucleation of 78.6%. Cox' regression disclosed a coefficient of 0.049 with a standard aviation of 0.293 and a P-value of 0.867. All parameters were showing no statistical difference between Ruthenium treated and enucleated patients. The survival rate in males was 69.2%, female patients 87.2%. For male patients there was a 2,4-fold higher risk to develop metastasis compared with female patients. Patient's age at the time of treatment correlated significantly with the prognosis. There was an increase in mortality risk by factor 1.4 per decade.