Picornaviruses (family Picornaviridae) are small, non-enveloped viruses with positive sense, single-stranded RNA genomes. The numbers of the novel picornavirus species and genera are continuously increasing. Picornaviruses infect numerous vertebrate species from fish to mammals, but have not been identified in a member of the Lagomorpha order (pikas, hares and rabbits). In this study, a novel picornavirus was identified in 16 (28.6%) out of 56 faecal samples collected from clinically healthy rabbits (Oryctolagus cuniculus var. domestica) in two (one commercial and one family farms) of four rabbit farms in Hungary. The 8364 nucleotide (2486 amino acid) long complete genome sequence of strain Rabbit01/2013/HUN (KT325852) has typical picornavirus genome organization with type-V IRES at the 5'UTR, encodes a leader (L) and a single 2A(H-box/NC) proteins, contains a hepatitis-A-virus-like cis-acting replication element (CRE) in the 2A, but it does not contain the sequence forming a "barbell-like" secondary structure in the 3'UTR. Rabbit01/2013/HUN has 52.9%, 52% and 57.2% amino acid identity to corresponding proteins of species Aichivirus A (genus Kobuvirus): to murine Kobuvirus (JF755427) in P1, to canine Kobuvirus (JN387133) in P2 and to feline Kobuvirus (KF831027) in P3, respectively. The sequence and phylogenetic analysis indicated that Rabbit01/2013/HUN represents a novel picornavirus species possibly in genus Kobuvirus. This is the first report of detection of picornavirus in rabbit. Further study is needed to clarify whether this novel picornavirus plays a part in any diseases in domestic or wild rabbits.

Retroviruses (family Retroviridae) are important agents of humans and animals. This study reports the detection and complete genome characterization of a novel endogenous retrovirus from the black Syrian hamster (Mesocricetus auratus) with a squamous cell skin tumor. The proviral genome, tentatively named black Syrian hamster retrovirus (BSHRV/2013/HUN, MK304634), was 8784 nucleotide in length with typical full-length betaretrovirus genome organization of 5'LTR-gag-pro-pol-env-3'LTR and with a characteristic mouse mammary tumor virus-like (MMTV) betaretrovirus dUTPase domain but without a sag gene. The BSHRV gag (534aa), pro/ pol (~1099aa) and env (672aa) proteins had 56%/63%/50% aa identity to the corresponding proteins of MMTV (AF228552). The proviral DNA is detectable in tumor as well as in tumor-free cells by conventional PCR and qPCR but only visible in the tumor cells by in situ hybridization. Low level retroviral RNA expression was found only in the DNase-treated RNA tumor samples using RT/nested PCR. BSHRV/2013/HUN-like betaretrovirus DNA was also identified from a faecal and tissue samples from 1 of the further 3 tested individuals by nested-PCR and qPCR. Further research is needed to investigate the distribution, activity and etiological role of this novel MMTV-like betaretrovirus species in hamster.

Approximately 20% of the tumours in humans are associated with contagious viral agents. Merkel cell carcinoma is a rare and highly aggressive tumour which may originate from the epidermal stratum basale, although the origin is still controversial. This tumour is most commonly found in elderly and immunocompromised patients in sun exposed areas, especially in the head and neck regions. Merkel cell carcinoma often causes a diagnostic challenge with a dramatically increasing incidence. In 2008, a DNA tumour virus, a polyomavirus (Merkel cell polyomavirus) was detected in Merkel cell carcinomas, and this finding helped to understand the etiological background of the disease. The infectious - probably viral - etiology resulted in a paradigm shift in pathogenesis and, hopefully, in therapy as well. This review summarizes the current knowledge related to Merkel cell carcinoma and the first oncogenic human polyomavirus, the Merkel cell polyomavirus, to promote the clinical adaptation of the information.

Merkel cell carcinoma (MCC) is a rare, highly aggressive skin tumour. In 2008, a Merkel cell polyomavirus (MC) was identified in MCCs as a potential etiological factor of MCC. The aims of this retrospective study were to investigate the epidemiological, clinicopathological and virological features of MCCs. Between 2007 and 2012, 11 patients had been diagnosed with MCC by histological methods in University of Pécs, Hungary. In eight MCC cases MC was tested by PCR (in primary skin lesions, lymph nodes/cutan metastases, MCC neighboring carcinomas). Clinicopathological characteristics (age, histological pattern, lymphovascular invasion, co-morbidities) of MC-positive and MC-negative cases were compared. MC was detected in three (37.5%) out of eight patients' primary tumour or metastasis. The average age was 73.8 (64.3 in MC-positive group). Except the youngest, 55 year-old patient (the primary tumour appeared on his leg), all tumours were found at the head and neck region. Immunosuppression (steroid therapy, chronic lymphoid leukaemia, chronic obstructive pulmonary disease) and/or old age were characteristic for all cases. Histological pattern was different in MC-positive and in MC-negative groups: MCCs with MC showed more homogeneous histological pattern, lack of lymphovascular invasion and were associated with better prognosis (mortality rate: 33% versus 80%). MCC associated with oncogenic virus is a newly recognized clinical entity. However, MC could not be detected in all histologically proven MCCs. The well-defined selection of patients/disease groups and better characterization of differences between MC-positive and negative cases is an important step towards the recognition of the etiology and pathogenesis of all MCCs.