The genome of a new human polyomavirus, known as Merkel cell polyomavirus (MCV), has recently been reported to be integrated within the cellular DNA of Merkel cell carcinoma (MCC), a rare human skin cancer. To investigate MCV seroprevalence in the general population, we expressed three different MCV VP1 in insect cells using recombinant baculoviruses. Viruslike particles (VLPs) were obtained with only one of the three VP1 genes. High-titer antibodies against VP1 VLPs were detected in mice immunized with MCV VLPs, and limited crossreactivity was observed with BK polyomavirus (BKV) and lymphotropic polyomavirus (LPV). MCV antibodies were detected in 77% of the general population, with no variations according to age.Polyomaviruses are small, nonenveloped DNA viruses, with a double-stranded circular DNA genome of ϳ5 kbp packaged within a capsid about 45 nm in diameter. The polyomavirus capsid is composed of three structural proteins: VP1, the major capsid protein, and VP2 and VP3, the minor capsid proteins. Twenty members of the polyomavirus family have been identified to date (24) and, with the exception of the murine pneumotropic polyomavirus and the avian polyomavirus, primary infection is generally asymptomatic. Five polyomaviruses infect humans, including the ubiquitous BK polyomavirus (BKV) and JC polyomavirus (JCV), which cause persistent and/or latent infections and the recently identified KI and WU polyomaviruses isolated from pulmonary secretions (1, 6). A new polyomavirus, the Merkel cell polyomavirus (MCV), was recently discovered in human Merkel cell carcinomas (MCC) (4). MCC is a relatively rare skin cancer in elderly or immunosuppressed patients and is one of the most lethal skin cancers (8). The annual incidence rate of this aggressive primary cutaneous neuroendocrine carcinoma in the United States was reported to be 0.44 per 100,000 inhabitants in 2001 and tripled between 1986 and 2001 (8), and this trend is continuing (7). An incidence of 0.13 cases per 100,000 was recently reported in France (15). Clonal integration of the MCV genome within the tumor genome (4) and the deletions and/or mutations observed within the T antigen gene (17) have suggested a direct oncogenic role for MCV. However, the prevalence and pathogenicity of this newly discovered MCV have yet to be fully investigated.The aim of the study was to produce MCV viruslike particles (VLPs) and to investigate the presence of MCV antibodies in the general population of Europe. MCV VLPs were obtained with only one of the three MCV VP1 strains investigated, and these VLPs were used to investigate cross-reactivity against other polyomaviruses and for the determination of the prevalence of MCV antibodies in the general European population. MATERIALS AND METHODSGeneration of VLPs for MCV, BKV, and LPV polyomaviruses. Expression of the VP1 protein was performed using the MCC350 VP1 prototype sequence and the VP1 sequences amplified from two French MCC patients (MKT-21 and MKT-26) (EMBL FM864207 and FM864209, respectively) (21). MCC350 VP1 codi...

Genetic recombination in RNA viruses was discovered many years ago for poliovirus (PV), an enterovirus of the Picornaviridae family, and studied using PV or other picornaviruses as models. Recently, recombination was shown to be a general phenomenon between different types of enteroviruses of the same species. In particular, the interest for this mechanism of genetic plasticity was renewed with the emergence of pathogenic recombinant circulating vaccine-derived polioviruses (cVDPVs), which were implicated in poliomyelitis outbreaks in several regions of the world with insufficient vaccination coverage. Most of these cVDPVs had mosaic genomes constituted of mutated poliovaccine capsid sequences and part or all of the non-structural sequences from other human enteroviruses of species C (HEV-C), in particular coxsackie A viruses. A study in Madagascar showed that recombinant cVDPVs had been co-circulating in a small population of children with many different HEV-C types. This viral ecosystem showed a surprising and extensive biodiversity associated to several types and recombinant genotypes, indicating that intertypic genetic recombination was not only a mechanism of evolution for HEV-C, but an usual mode of genetic plasticity shaping viral diversity. Results suggested that recombination may be, in conjunction with mutations, implicated in the phenotypic diversity of enterovirus strains and in the emergence of new pathogenic strains. Nevertheless, little is known about the rules and mechanisms which govern genetic exchanges between HEV-C types, as well as about the importance of intertypic recombination in generating phenotypic variation. This review summarizes our current knowledge of the mechanisms of evolution of PV, in particular recombination events leading to the emergence of recombinant cVDPVs.

eWe have shown that the circulating vaccine-derived polioviruses responsible for poliomyelitis outbreaks in Madagascar have recombinant genomes composed of sequences encoding capsid proteins derived from poliovaccine Sabin, mostly type 2 (PVS2), and sequences encoding nonstructural proteins derived from other human enteroviruses. Interestingly, almost all of these recombinant genomes encode a nonstructural 3A protein related to that of field coxsackievirus A17 (CV-A17) strains. Here, we investigated the repercussions of this exchange, by assessing the role of the 3A proteins of PVS2 and CV-A17 and their putative cellular partners in viral replication. We found that the Golgi protein acyl-coenzyme A binding domain-containing 3 (ACBD3), recently identified as an interactor for the 3A proteins of several picornaviruses, interacts with the 3A proteins of PVS2 and CV-A17 at viral RNA replication sites, in human neuroblastoma cells infected with either PVS2 or a PVS2 recombinant encoding a 3A protein from CV-A17 [PVS2-3A(CV-A17)]. The small interfering RNA-mediated downregulation of ACBD3 significantly increased the growth of both viruses, suggesting that ACBD3 slowed viral replication. This was confirmed with replicons. Furthermore, PVS2-3A(CV-A17) was more resistant to the replication-inhibiting effect of ACBD3 than the PVS2 strain, and the amino acid in position 12 of 3A was involved in modulating the sensitivity of viral replication to ACBD3. Overall, our results indicate that exchanges of nonstructural proteins can modify the relationships between enterovirus recombinants and cellular interactors and may thus be one of the factors favoring their emergence.