(p125) protein in Ncp and Cp BVDV-infected cells are 120 kDa. The cleavage of NS2-NS3 is connected to the replication of the virus in the early stages of virus infection. A complex known as NS2-NS3/NS4A (NS2-3/4A) is created when NS4A joins with uncleaved NS2-NS3 (NS2-3) or NS3/NS4A. It can be utilized to support RNA replication and virus assembly as the fundamental element of virus particles. In the NS3/NS4A serine protease complex, NS4A functions as a protease cofactor, engaging with NS3 to catalyze the cleavage of downstream proteins NS4B, NS5A, and NS5B. In particle assembly, NS2 and NS3 can replace uncut NS2-NS3 molecules, but the precise mechanism is still unknown. A 35 kDa hydrophobic protein with NTPase activity called NS4B (p30) is involved in the replication of the BVDV genome. Due to interactions between the viral Npro, Erns, and NS4B and the host immune signaling pathways, BVDV can bypass the host immune response and cause persistent infection in cattle by blocking their innate immune responses. The primary target for the diagnosis of diseases, the creation of vaccines, and the management of infections is NS4B. After viral infection, NS4B can trigger humoral and cellular immune responses thanks to its highly conserved epitopes. NS5B (p75), which features a functional motif typical of viral RNA-dependent RNA polymerase, is roughly 77 kDa in size (RdRp). It primarily participates in the process of virus-infected cell membrane rearrangement and catalyzes the creation of viral RNA. The C-terminus of the BVDV polyprotein is where the NS5A (p58) and NS5B (p75) are separated. Infected cells typically contain NS5A (p58) as a single protein or as an uncleaved NS5A-NS5B complex. A hydrophilic, phosphorylated protein with a molecular weight of 58 kDa called NS5A is a part of the viral replicase. Although NS5B has a significant impact on RNA replication, its lack of specificity may have an impact on the design of viral replicase. A number of issues, including the pathogenic mechanism, the regulation of virus replication, and the interaction between p7, NS4B, NS5A, and other NSP, remain unresolved. Species Pestivirus A or Bovine viral diarrhea virus 1 (BVDV-1), causes Bovine viral diarrhea and Mucosal disease Pestivirus B or Bovine viral diarrhea virus 2 or (BVDV-2), causes Bovine viral diarrhea and Mucosal disease Pestivirus C or Classical swine fever virus (CSFV), causes Classical swine fever Pestivirus D or Border disease virus (BDV), causes Border disease Pestivirus E or pronghorn pestivirus Pestivirus