Post-exposure prophylactic (PEP) neutralizing antibodies against Rabies are the most effective way to prevent infection-related fatality. The outer envelope glycoprotein of the Rabies virus (RABV) is the most significant surface antigen for generating virus-neutralizing antibodies. The small size and uncompromised functional specificity of single domain antibodies (sdAbs) can be exploited in the fields of experimental therapeutic applications for infectious diseases through formatting flexibilities to increase their avidity towards target antigens. In this study, we used phage display technique to select and identify sdAbs that were specific for the RABV glycoprotein from a naïve llama-derived antibody library. To increase their neutralizing potencies, the sdAbs were fused with a coiled-coil peptide derived from the human cartilage oligomeric matrix protein (COMP48) to form homogenous pentavalent multimers, known as combodies. Compared to monovalent sdAbs, the combodies, namely 26424 and 26434, exhibited high avidity and were able to neutralize 85-fold higher input of RABV (CVS-11 strain) pseudotypes in vitro, as a result of multimerization, while retaining their specificities for target antigen. 26424 and 26434 were capable of neutralizing CVS-11 pseudotypes in vitro by 90–95% as compared to human rabies immunoglobulin (HRIG), currently used for PEP in Rabies. The multimeric sdAbs were also demonstrated to be partially protective for mice that were infected with lethal doses of rabies virus in vivo. The results demonstrate that the combodies could be valuable tools in understanding viral mechanisms, diagnosis and possible anti-viral candidate for RABV infection.

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Rabies virus (RABV) causes a fatal infectious disease, but effective protection may be achieved with the use of rabies immunoglobulin and a rabies vaccine. Virus-neutralizing antibodies (VNA), which play an important role in the prevention of rabies, are commonly evaluated by the RABV neutralizing test. For determining serum VNA levels or virus titers during the RABV vaccine manufacturing process, reliability of the assay method is highly important and mainly dependent on the diagnostic antibody. Most diagnostic antibodies are monoclonal antibodies (mAbs) made from hybridoma cell lines and are costly and time consuming to prepare. Thus, production of a cost-effective mAb for determining rabies VNA levels or RABV titers is needed. In this report, we describe the prokaryotic production of a RABV-specific single-chain variable fragment (scFv) protein with a His-tag (scFv98H) from a previously constructed plasmid in a bioreactor, including the purification and refolding process as well as the functional testing of the protein. The antigen-specific binding characteristics, affinity, and relative affinity of the purified protein were tested. The scFv98H antibody was compared with a commercial RABV nucleoprotein mAb for assaying the VNA level of anti-rabies serum samples from different sources or testing the growth kinetics of RABV strains for vaccine manufactured in China. The results indicated that scFv98H may be used as a novel diagnostic tool to assay VNA levels or virus titers and may be used as an alternative for the diagnostic antibody presently employed for these purposes.

The objective of this study was to develop rat model of second-degree burn pain and test analgesic efficacy of local thiamine administration. Automatic temperature-controlled hot plate was set at 85 ± 0.1°C with a filter paper on the top. Rats were thrust on hot plate landing on plantar surface for 4 to 7 and 10 seconds, respectively. Burnt skin was observed. Hematoxylin and eosin staining and Masson staining were used to monitor burn degree. Gait analysis detected change of locomotion. Allodynia and hyperalgesia in the burnt area were evaluated with von Frey test and Hargreaves Test, and ongoing pain was detected with conditional place preference test. Markers for the activity of microglia (Iba1), astrocytes (GFAP), and neurons (c-fos) were detected with immunofluorescence. Finally, thiamine was injected into blisters to observe its effect on burn pain. Blisters on burnt skin, space between dermal and epidermal layers in hematoxylin and eosin staining and burn injury limiting in dermal layer in Masson stain all indicated that burn injury lasting for 7 seconds matched second-degree burn. Behavioral tests revealed allodynia, ongoing pain, and increased expression of c-fos, GFAP, and Iba1, as well as the absence of hyperalgesia in Burn7s. Burn injury reduced distance of second and fourth digits. MK801 could relieve allodynia in Burn7s. Local administration of 1, 2, and 4 mg of thiamine had no effect on the allodynia, but 2 and 4 mg of thiamine also could induce conditional place preference (CPP) in Burn7s. A rat model of second-degree burn pain was developed and local administration of thiamine provided relief from pain.