In the late 1980s, Dr. Hamers’ team in Belgium discovered that, besides conventional IgG1 antibodies, camel serum contains about 75% antibodies made of only heavy chains without light chains — the Heavy Chain-Only Antibodies (HCAbs). These are also present in llamas and alpacas. The N-terminal domain of HCAbs, capable of directly binding antigens, was later defined as a single-domain antibody (sdAb, VHH, or Nanobody) and has since been widely used in antibody drug development. Comparing to other antibodies, VHH antibodies have several advantages as follows:

• High stability and solubility: Evolution increased hydrophilicity to compensate for the missing light chain, allowing them to remain stable even at 70 °C.
• Low immunogenicity: Despite evolutionary distance, camelid antibodies share higher homology with human antibodies than rodent ones.
• Deep epitope access: Longer CDR3 regions enable binding to recessed antigen sites.
• Easy engineering: Their simple structure facilitates affinity maturation, humanization, and bispecific antibody design.
• Small size: Llama-derived nanobodies (~15 kDa) can penetrate tissues more effectively.

Nanobody® is a registered trademark of Ablynx N.V., a Sanofi company.

Stage	Service Content	Time Frame	Deliverables
I	Antigen preparation (or provided by the client)	2-3 weeks	Quality Control Data
II	Animal immunization (Alpacas)	8-10 weeks	Serum titer report, Serum
III	Library construction	2-3 weeks	library quality assessment report(capacity≥107)
IV	Antibody screening(solid-phase, liquid-phase, etc.)	3-5weeks	ELISA assay report, positive nanobody sequences
V	Antibody expression and evaluation (ELISA, FACS, SPR,etc.)	3 weeks	assessment report
VI	Report compilation	1 weeks	project report