Parvoviruses are a group of very broad species-specific viruses that have been detected in cattle, pigs, dogs, cats, mink, geese, rats, mice, and humans. Abinati and Warfield identified BPV for the first time in the feces of calves in Maryland (USA) in 1961 [
1]. Bovine parvovirus (BPV) [
41] was classified as an autonomous parvovirus in 1970 and placed in the Parvoviridae family's bocaparvovirus genus [
4,
6,
41]. This virus group is very similar to other autonomous parvoviruses in terms of its viral properties, with the exception of subtle differences in its structural proteins. Furthermore, Bates and coworkers [
6] found little resemblance between bovine parvovirus and other animal parvoviruses [
36]. More importantly, such virus groups have the potential to produce visible-to-silent economic catastrophes in the livestock business. The prevalence and genetic variability of BPV across diverse ecosystems and geographical settings are rarely studied, despite the year of its announcement in 1960 as a veterinary important virus. It has coinfection potential with bacteria and nonparvoviruses, causing respiratory and gastrointestinal disease and challenging the cattle industry worldwide. However, only a few pieces of information and reports are available, with a very limited number of genetic resources (Additional file
1: Table S1) in public databases. Newborn calves infected with BPV often develop digestive and respiratory issues, while pregnant cows often experience spontaneous abortions and stillbirths [
5]. BPV infection has a prevalence of 83–100% in regions with cow herds around the world. The agent's prevalence across Africa is unknown, but it is likely widespread [
36]. However, Egyptian cattle with respiratory distress were found to be infected with bovine parvovirus-3 (BPV-3) for the first time by Nagy et al., and the whole-genome sequence of BPV-3 exhibited 93.02% nucleotide identity with the reference virus (Additional file
1: Table S1) [
25]. Calves from the United States (Maryland, South Dakota, Colorado and Oregon), Europe (England), Asia (Japan, China, and Korea), Oceania (Australia) and Africa (Algeria) all had bovine parvovirus (BPV) isolated from their feces, lymph nodes, tonsils, and conjunctival excretions at varying points in the infection course. According to historical records on BPV virus isolation from various nations [
31], there is a wide range in the start of clinical signs such as diarrhea, conjunctivitis, and respiratory diseases, from as early as 1 week of age in calves to as late as 1 year of age [
34]. Calves who were weaned at a younger age began excreting bovine parvovirus sooner, although this may be because they had a lower amount of maternally generated antibodies. An earlier-born calf without maternally acquired antibodies did not excrete parvovirus until four weeks after weaning. This demonstrates that most prevalence reports of bovine parvovirus are linked to calf diarrhea and that the virus causes economic losses in the cattle sector without causing any outward symptoms [
29]. For instance, Lee et al. reported from Korean dairy farms that viruses (117/164, 71.3%) were the most common causative agent of calf diarrhea, and of these, 5.5% of the calves were infected with bovine parvovirus [
21]. Concurrent infection with another enteric pathogen or other variables that stimulate intestinal epithelial proliferation may worsen the severity of the disease [
24]. However, antibodies against nonbovine parvovirus antigens are unlikely to be detected in serological surveys in cattle as a result of cross-infection [
6]. Cross-infection with nonbovine parvoviruses is therefore highly unlikely to be discovered in serological studies of cattle [
6]. BPV strain VR-767 was also detected in clave fecal samples from the Heilongjiang, Jilin, Liaoning, and Inner Mongolia provinces using PCR [
40]. An old serological study from North Queens Land, Australia, showed that calves could develop bovine parvovirus infection soon after weaning [
10]. Despite the considerable evidence indicating the frequently endemic nature of bovine parvovirus in cattle, relatively little investigation has been made on the role of the virus in causing enteric disease [
10]. There is a high prevalence of antibodies against bovine parvovirus 1 (BPoV-1) in naturally infected cattle across the globe [
34], and all BPV-1 isolates have been found to be closely related to or identical to the prototype strain described by Abinanti and Warfield [
1].
Physiochemically, parvoviruses are among the most stable viruses found in vertebrates [
33]. Bovine parvoviruses, like most other parvoviruses, are extremely resistant to chemical and physical inactivating factors. The most reliable disinfection is achieved with 0.5% chlorox or ethylene oxide in the form of a nonexplosive mixture of 10% ethylene oxide and 90% carbon dioxide [
25]. In addition, the virus can survive for up to six months when stored at − 20 °C [
1]. Bovine parvovirus can maintain a pH ranging from 6.2 to 9. This virus can be isolated from liquid manure [
26]. Hence, parvoviruses such as swine parvovirus [
28,
30]), human parvovirus [
2], canine parvovirus [
11], and BPV [
35] are currently playing a role in the nanoparticle vaccine sector, such as VLP chimeric vaccines against numerous infectious diseases. When used as a vaccination platform, virus-like particles (VLPs) can stimulate both humoral and cell-mediated immunity, leading to robust immune responses (Additional file
1: Fig. S1) [
19].
According to the molecular architecture and genome organization, BPV is an autonomously replicating virus with a linear single-stranded DNA (ssDNA) genome of 5.5 kb flanked by nonidentical palindromic terminal hairpins, similar to other bocaparvoviruses [
37]. Mature BPV virions are small, nonenveloped particles, 20–28 nm in diameter, with no known essential lipids, carbohydrates, accessory proteins or histones [
17]. The absence of an envelope readily helps with in vitro assembly and the formation of soluble homogeneous noneVLPs that can be expressed in both eukaryotic and prokaryotic systems [
37]. The whole genome encodes three ORFs (Additional file
1: Fig S2) [
22].
To make an icosahedral viral capsid of 60 monomers, VP1 and VP2 capsid proteins can either co-assemble in a ratio of 5–95% or self-assemble alone [
32]. The N-terminal region of VP1 is distinct for each species of parvovirus, with 411 and 227 residues for bovine and human parvovirus, respectively, in addition to VP2 amino acids. It is calculated that the mature virion has a buoyant density of 1.38 g/ml in a CsC density gradient [
17]. Understanding how the capsid structure relates to the function of viruses provides a platform for recombinant engineering of viral gene delivery vectors for the treatment of clinical diseases [
3]. Porcine parvovirus (PPV) VLPs produced by self-assembly through in vivo or in vitro methods could effectively display a foreign epitope [
14,
39] and are good particles to design and develop chimeric epitope-based vaccines against PPV and FMDV [
42] (Additional file
1: Table S2).
Despite the fact that parvovirals have good quality for such platforms, the potential of BPV VLP in displaying a foreign epitope for an epitope-based vaccination platform has barely been explored in comparison to that of other parvoviruses. Even less is known about the mechanisms by which BPV capsid proteins contribute to the successful production of VLPs in either prokaryotes or eukaryotes. No single experimental report on the role of VP1 of the BPV in the assembly and stability of VLPs is available. No previous study has evaluated the ability of recombinant BPV VP2 and VP1 VP2 Cap proteins to self-assemble into VLPs using an insect-baculovirus expression method. We believe that determining the stability and ease of generating BPV virus-like particles (VLPs) either from a single structural protein (VP2) or by combining both VP2 and VP1 proteins is critical to utilizing the VLPs of this virus as an anti-BPV vaccine and vaccine carrier.