With the gradual development of large - scale breeding in animal husbandry, the hidden risks and harms of various viral infectious diseases, bacterial diseases, and parasitic diseases in livestock have become increasingly prominent and intensified. Examples of such pathogens include Porcine Epidemic Diarrhea Virus (PEDV), Bovine Viral Diarrhea - Mucosal Disease Virus (BVDV), Foot - and - Mouth Disease Virus (FMDV), and African Swine Fever Virus (ASFV)
Taking BVDV as an example: This virus has complex transmission routes, and most infections are latent and can lead to persistent infection. Susceptible livestock with persistent infection may suffer from reproductive diseases such as abortion, fetal death, and follicular dysfunction, and dairy cows may experience a decrease in milk production. After the virus enters the bovine fetus through the placental barrier, the resulting fetus becomes a Persistently Infected (PI) calf, which carries and sheds the virus throughout its life [2]. Since BVDV was first isolated and identified in China in 1980, it has caused severe economic losses to livestock farmers in more than 20 provinces and cities across the country.
Currently, both domestic and international prevention and control measures for this virus as well as other various viruses and bacterial diseases mainly rely on detection, culling of hosts with persistent infection, and prevention using inactivated vaccines. However, traditional detection methods and vaccine - based prevention still have various shortcomings, so researchers are urgently seeking new breakthroughs [3].
In terms of virus detection, researchers targeted the N protein of PEDV, biotinylated the purified Nb2 - Avi - tag fusion protein in vitro. Compared with commercial kits, this method exhibited extremely high sensitivity and specificity. The same approach was also used to develop a blocking Enzyme - Linked Immunosorbent Assay (bELISA) for the S protein of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), which greatly facilitated clinical detection. In addition, for PI calves with persistent BVDV infection, the indirect ELISA method for detecting BVDV antibodies fails to identify them. Researchers from Shihezi University in China have established a nanobody - based double - antibody sandwich ELISA for the detection of BVDV [4].
In the treatment of infectious diseases in livestock, nanobodies have also demonstrated satisfying capabilities. In 2015, Chinese researchers screened Variable Domain of Heavy - chain only Antibody (VHH) fragments against the BVDV - NADL strain using nanobodies, and these fragments showed a strong inhibitory effect on the replication of BVDV. In another study focusing on inhibiting BVDV replication, Chinese researchers used a nanobody named Nb - YT to study non - cytopathic BVDV1 (BVDV1b). It was found that the inhibition rate of this nanobody on viral replication in a mouse model was more than 10 times higher than that of the control group [5].
Based on the research conclusions from various domestic scientific research institutions, nanobodies represent a highly suitable research strategy for the detection of viral and bacterial pathogens causing infectious diseases in livestock, as well as for the development of new vaccines. This new strategy exhibits excellent and practical development value both in terms of utility and economy.
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