Current knowledge on epidemiology and evolution of novel porcine circovirus 4

Abstract

Porcine circovirus type 4 (PCV4) is a newly emerging virus, with both PCV4 genomic DNA and specific antibodies detected in swine herds in several provinces in China and South Korea. Although the virus was first identified in 2019 in Hunan, China, retrospective research suggests that serum samples collected as early as 2008 were positive for PCV4 antibody. Infections with only PCV4 or co-infections with other pathogens have been associated with several clinical manifestations, but its pathogenesis remains to be determined. The purpose of this review was the following: (1) to characterize PCV4 epidemiology by assessing evolutionary dynamics and genetic diversity of PCV4 strains circulating in swine herds; (2) to reconstruct a computerized 3D model to analyze PCV4 Cap properties; (3) and to summarize the current evidence of PCV4-associated clinical-pathological manifestations. The origin of PCV4 is apparently distinct from other PCV, based on analysis of phylogenetic trees. Of note, PCV4 shares an ancient common ancestor with mink circoviruses. Furthermore, the amino acid residue at position 27 of the PCV4 Cap is a key benchmark to distinguish PCV4a (27S) from PCV4b (27 N), based on PCV4 strains currently available, and variation of this residue may alter Cap antigenicity. In addition, the capsid surface of PCV4 has characteristics of increased polar residues, compared to PCV2, which raises the possibility that PCV4 may target negatively charged host receptors to promote virus infection. Further studies are required, including virus isolation and culture, and more detailed characterization of molecular epidemiology and genetic diversity of PCV4 in swine herds.

Circovirus Hepatitis Infection in Heart-Lung Transplant Patient, France

“…Animal circoviruses, such as porcine circoviruses (PCV) 1–4, have been responsible for reproductive failure, dermatitis, nephropathy, and respiratory diseases in animals ( 17 , 18 ), manifestations not found in the case we report. However, PCV2 associated with cases of jaundice in pigs ( 19 – 21 ) and hepatitis in a horse have been demonstrated ( 22 ).…”

Molecular detection and genetic characterization of porcine circovirus 4 (PCV4) in Thailand during 2019–2020

“…Further investigation is required www.nature.com/scientificreports/ to establish the standardized criteria for genotyping PCV4, given the current paucity of sequence information. As mentioned above, previous reports showed that the amino acid at the position 27 of the Cap gene could be used as a marker to distinguish between PCV4a (27S) and PCV4b (27N) 19,20 . However, the results in this study showed that the amino acid residue at position 27 cannot be used to differentiate between PCV4a and PCV4b since the Thai PCV4b strains and the Korean PCV4b strains (KU-02010 and KU-02011) showed N27S (Fig.…”

“…This is in contrast with PCV2 genotyping that a unified classification scheme based on Cap gene was proposed 18 . For PCV4 genotyping, there have been several studies proposing different criteria and markers to differentiate PCV4 genotypes, such as 2-group classification (PCV4a and PCV4b) and 3-group classification (PCV4a, PCV4b, and PCV4c) 10,[19][20][21] . Among these studies, the residue at 27 and 212 of capsid gene were also proposed to be used in distinguishing PCV4a (27S and 212L) from PCV4b (27N and 212M) 19,20 .…”

“…However, the effects of genetic mutation on pathogenicity need further investigation. In terms of the genetic variation of PCV4 and its genotypes, a study conducted in various regions in China found that PCV4a was the most common genotype followed by PCV4b 10,11,[19][20][21] . However, in pig populations from Korea and Thailand, only the PCV4b genotype was detected 8 .…”

Seroprevalence of Porcine Circovirus Type 2 in Domestic Pigs of Thailand: Two Decades After Nationwide Vaccines Application

“…The multiple disease syndromes are ascribable to PCV2 infection and are summarized under the term of porcine circovirus diseases (PCVD) (Palinski et al, 2017). Recently, novel types of PCV has been identified, including PCV3 (Klaumann et al, 2018;Saporiti et al, 2021) and PCV4 (Li et al, 2022;Wang et al, 2022). It is currently under surveillance for its impact on swine industry.…”