Canine parvovirus (CPV) can cause acute and highly contagious bloody enteritis in dog. To obtain antibodies against CPV, hens were immunized with virus-like particles (VLP) of CPV-VP2. The IgY single chain fragment variables (scFv) were generated by T7 phage display system and expressed in E. coli system. The titer of the primary scFv library reached to 1.5 × 10⁶ pfu/mL, and 95% of the phages contained the target fragments. The CPV-VLP and CPV-VP2 protein showed similar reaction values to the purified scFv in the ELISA test, and the results of ELISA analysis using IgY-scFv toward CPV clinical samples were consistent with commercial immunochromatographic assay (ICA) and PCR detection, the scFv did not show cross reactivity with canine distemper virus (CDV) and canine coronavirus (CCV). IgY-scFv was successfully expressed in CRFK cells, and in the virus suppression assay, 55% of CPV infections were eliminated within 24 h. Docking results demonstrated that the number of amino acids of the binding sides between scFv and VP2 were AA37 and AA40, respectively. This study revealed the feasibility of a novel functional antibody fragment development strategy by generating diversified avian IgY-scFv libraries towards the pathogenic target of interest for both detection and therapeutic purposes in veterinary medicine.

As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to spread globally, a series of vaccines, antibodies and drugs have been developed to combat coronavirus disease 2019 (COVID-19). High specific antibodies are powerful tool for the development of immunoassay and providing passive immunotherapy against SARS-CoV-2 and expected with large scale production. SARS-CoV-2 S1 protein was expressed in E. coli BL21 and purified by immobilized metal affinity chromatography, as antigen used to immunize hens, the specific IgY antibodies were extracted form egg yolk by PEG-6000 precipitation, and the titer of anti-S1 IgY antibody reached 1:10,000. IgY single chain variable fragment antibody (IgY-scFv) was generated by using phage display technology and the IgY-scFv showed high binding sensitivity and capacity to S1 protein of SARS-CoV-2, and the minimum detectable antigen S1 protein concentration was 6 ng/µL. The docking study showed that the multiple epitopes on the IgY-scFv interacted with multiple residues on SARS-CoV-2 S1 RBD to form hydrogen bonds. This preliminary study suggests that IgY and IgY-scFv are suitable candidates for the development of immunoassay and passive immunotherapy for COVID-19 to humans and animals.

Antibody mimetics may be used for various biomedical applications, especially those for which conventional antibodies are ineffective. In this study, we developed a smaller molecular chicken IgY mimetic peptide (IgY-peptide) based on the complementarity-determining regions (CDRs) of the anti-canine parvovirus (CPV) IgY-scFv prepared previously. The mimetic peptide showed no cross-reactivity with canine distemper virus (CDV) and canine coronavirus (CCV) and showed excellent protective properties for Crandell-Rees Feline Kidney (CRFK) cells against CPV. This study is the first attempt to develop a mimetic IgY-peptide and demonstrates the ease and feasibility in generating such a novel antibody-like functional molecule for biomedical purposes.

The global epidemic of diabetes mellitus the limitations of current therapies-including waning efficacy, adverse effects, and inability to modify disease progression-have accelerated the shift from conventional pharmacotherapy toward biologic agents. This review examines the emergence of single-chain variable fragments (scFv) as a versatile and engineerable class of biotherapeutics for precision diabetes management. Distinguished from full-length monoclonal antibodies (mAbs) by their compact size, enhanced tissue penetration, and modular design, scFv enable precise targeting of both autoimmune and metabolic pathways underlying type 1 diabetes and type 2 diabetes. We summarize advances in scFv applications spanning immunomodulation (e.g., via CTLA-4 and PD-1) and metabolic regulation (e.g., through insulin-degrading enzyme and GLP-1 receptor). Furthermore, we highlight the unique value of avian-derived scFv in recognizing conserved epitopes and overcoming immune tolerance, along with engineering strategies-such as Fc fusion, PEGylation, and multispecific formatting-that enhance pharmacokinetics and therapeutic efficacy. The clinical success of antibodies like Teplizumab underscores the translational potential of antibody-based platforms. Looking forward, scFv-based biologics, particularly when integrated with humanized Fc domains and half-life extension technologies, offer a promising and customizable strategy for next-generation diabetes therapy, bridging innovative drug design with clinically meaningful metabolic and immune modulation.