Identification of the Porcine Cytomegalovirus Major Capsid Protein Gene.

Abstract

ABSTRACT. A major capsid protein (MCP) gene homologue of porcine cytomegalovirus (PCMV) was identified. Sequence analysis indicated that the PCMV MCP gene is 4,026 nucleotides in length encoding a protein of 1,341 amino acid residues. The predicted molecular weight of the PCMV MCP is 151,456 Da, equivalent to those of other herpesvirus MCP counterparts. Phylogenetic analysis using herpesviral MCP gene sequences confirmed that PCMV is a betaherpesvirus with higher homology with human herpesvirus-6 and -7 than human and mouse cytomegaloviruses. The serum of pig experimentally infected with PCMV did not react with bacterially expressed MCP, suggesting that the PCMV MCP may not be related to the humoral immune response in the course of PCMV infection. Also, we established polymerase chain reaction (PCR) protocols using primers corresponding to MCP gene sequences for detection of PCMV infection. The PCR protocol would be effective for the diagnosis of slow-growing PCMV infection, for which traditional methods involving virus-isolation are not useful. KEY WORDS: betaherpesvirus, major capsid protein, polymerase chain reaction, porcine cytomegalovirus.J. Vet. Med. Sci. 63(6): 609-618, 2001 Porcine cyomegalovirus (PCMV), first described in 1955 [6], usually induces a silent infection in adult pigs but often a fatal, generalized infection in piglets. In utero infection in sows can cross the placenta and infect the fetuses leading to fetal death or birth of weak piglets [3,17]. As PCMV exhibits a relatively protracted replication cycle, a slowly developing cytopathology characterized by cytomegaly, and a restricted host range, it is grouped into the subfamily Betaherpesvirinae [18]. Recently, we and other research groups confirmed that PCMV is a betaherpesvirus based on sequence analyses of DNA polymerase gene fragments [19,29].The major capsid protein (MCP) gene appears to be conserved among the herpesviruses [5,15], suggesting that MCP should play essential roles in vital processes in the viral replication cycle such as assembly and maturation. Herpes simplex virus-1 (HSV-1) has been shown to encode seven capsid proteins. Of these, MCP is the structural subunit of the hexons and pentons, and is the principal structural element making up the matrix of the icosahedral capsid [16]. In addition, in some herpesviruses such as HSV-1 and varicella-zoster virus (VZV), MCPs serve as an antigen for the humoral immune response during the course of infection, being highly reactive with human antisera as well as being responsible for cell-mediated immunity [7,20,27].The MCPs of many herpesviruses have been shown to have similar molecular masses, e.g., between 135 kDa and 160 kDa for human herpesviruses [2,4,10,14,15]. In this study, we identified the MCP gene of PCMV and expressed the protein in a bacterial expression system. In addition, we also analyzed the evolutionary position of PCMV in the herpesvirus group using MCP sequence information. We also established a polymerase chain reaction (PCR) protocol for specific detection ...

Molecular Epidemiology of Porcine Cytomegalovirus (PCMV) in Sichuan Province, China: 2010–2012

“…Previous work has primarily concentrated on the DNA polymerase ( DPOL ) gene, glycoprotein B ( gB ) gene, and the ORF 40-like protein gene, and sequences for these regions are available in GenBank. Genetic diversity has been noted in the DPOL and gB genes of different PCMV strains, resulting in antigenic variation; however, there is no evidence to confirm that PCMV has evolved significantly different serotypes or genotypes [9], [10], [11].…”

Susceptibility of porcine cytomegalovirus to antiviral drugs

“…3 Porcine cytomegalovirus (PCMV) is a β-herpesvirus showing sequence homology to human herpesviruses 6, 7 and human cytomegalovirus (HCMV). [4][5][6] It causes generalized infection in newborn piglets, with 90% of pigs being seropositive in the UK. 7 PCMV represents a potential risk in xenotransplantation since its human counterpart, HCMV, is frequently transmitted from the organ donor and re-activates post-transplant, where it is associated with end-organ disease and graft rejection.…”

Porcine cytomegalovirus in pigs being bred for xenograft organs: progress towards control

“…Porcine cytomegalovirus is a member of the β‐ herpesvirinae , and is endemic in the world pig population, with over 90% of pigs being seropositive in the UK, many of which are from high health status farms [19]. Recent molecular analysis of the DNA polymerase and major capsid protein genes of PCMV suggests that the virus is closely related to HHV‐6 and HHV‐7, and to HCMV [20,21]. As a herpesvirus, PCMV has the ability to remain in the host lifelong following primary infection including a latent phase and may reactivate periodically to produce infectious virus and potentially cause disease.…”