Selection and characterization of protective anti-chikungunya virus single domain antibodies

•Developed CHIKV VLP immune phage display library of single domain antibodies.•Selected sdAb that bind to CHIKV VLPs and/or recombinant E1 with good affinity.•SdAb neutralized CHIKV in a plaque reduction neutralization test.•CC3 and CA6 yielded PRNT50 values of 0.6 and 45.6 nM, respectively.•Alkaline phosphatase fusion to CC3 and CA6 improved affinity to CHIKV VLP and E1. Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes an arthralgia febrile illness that has affected millions of people on three continents. Previously, neutralizing monoclonal antibodies that have prophylactic and therapeutic activity were found to remove virus in joint tissues, thereby reducing the severity of symptoms in mice and non-human primates. In this study, we sought to develop thermostable small recombinant antibodies against CHIKV for future diagnostic, prophylactic and therapeutic applications. To develop these single domain antibodies (sdAb) a CHIKV immune library was constructed by displaying the consortium of variable heavy domains (VHH) amplified from peripheral white blood cells isolated from llamas immunized with CHIKV virus-like particles (VLPs). Five anti-CHIKV sdAb isolated using bio-panning were evaluated for their affinity and thermal stability. Their ability to detect CHIKV VLPs was demonstrated in both MagPlex- and ELISA- based assays. Finally, the ability of two sdAb, CC3 and CA6, to inhibit CHIKV infection were tested using a plaque reduction and neutralization test (PRNT), yielding PRNT50 values of 0.6 and 45.6 nM, respectively.