TABLE 3.

Characteristics of VHH heterodimers and homodimers

HDa	VHH Pairingsb		Protectionc	IC50d
				nm
JJX21	RTA-E5	RTB-B7	+	1*
JNA10	RTA-F6	RTB-B7	+	0.1
JNA11	RTA-E5	RTB-D12	+	0.1
JNA8	RTA-F6	RTB-D12	−	0.1
JNA6	RTB-B7	RTB-B7	−	0.5
JNA2	RTA-D10	RTA-D10	−	10
JNA3	RTA-E5	RTA-E5	−	1
JNA14	RTA-D10	RTA-E5	−	2

^aHD, heterodimer or homodimer.

^bUnderlining indicates neutralizing VHHs.

^cPlus (+) symbol indicates VHHs that passively protected mice against a 10 × LD₅₀ ricin challenge and minus (−) symbol indicates VHHs that did not confer complete protection.

^dValue indicates the concentration of VHHs required to neutralize 50% of ricin in a Vero cell cytotoxicity assay. (*) Indicates IC₅₀ values previously published (12).

^eValue indicates the effective concentration of VHHs required to achieve 50% maximal binding to ricin, RTA, or RTB for competition ELISAs.