Giant parapox infection in a two year old child

An Investigation of a Cluster of Parapoxvirus Cases in Missouri, Feb-May 2006: Epidemiologic, Clinical and Molecular Aspects

In the spring of 2006, four human cases of parapoxvirus infections in Missouri residents were reported to the Centers for Disease Control and Prevention (CDC), two of which were initially diagnosed as cutaneous anthrax. This investigation was conducted to determine the level of recognition of zoonotic parapoxvirus infections and prevention measures, the degree to which veterinarians may be consulted on human infections and what forces were behind this perceived increase in reported infections. Interviews were conducted and clinical and environmental sampling was performed. Swab and scab specimens were analyzed by real-time polymerase chain reaction (PCR), whereas serum specimens were evaluated for parapoxvirus antibodies. Three case patients were found to have fed ill juvenile animals without using gloves. Forty-six percent of veterinarians reported having been consulted regarding suspected human orf infections. Orf virus DNA was detected from five of 25 asymptomatic sheep. Analysis of extracellular envelope gene sequences indicated that sheep and goat isolates clustered in a species-preferential fashion. Parapoxvirus infections are common in Missouri ruminants and their handlers. Infected persons often do not seek medical care; some may seek advice from veterinarians rather than physicians. The initial perception of increased incidence in Missouri may have arisen from a reporting artifact stemming from heightened concern about anthrax. Asymptomatic parapoxvirus infections in livestock may be common and further investigation warranted.

Orf in South Africa: endemic but neglected

A survey amongst sheep and goat producers and veterinarians was undertaken to collect epidemiological data on orf in South Africa. Previous epidemiological studies on the presence of the disease in the country have not been documented and this report is the first descriptive epidemiological study of orf in South Africa. A seven-month investigation, realised by direct and indirect interviews and field observation, enabled us to outline incidence and risk factors of this disease and to better understand how the local farmers in rural areas relate to it. The results may contribute to better management of the disease in rural areas. By means of molecular analyses the phylogenetic relationships between field isolates from different areas have been identified. The findings gave a first important contribution to the general assessment of the economic impact of orf virus infections and the extent of the risk to human health.

Maturation and function of human dendritic cells are inhibited by orf virus-encoded interleukin-10

Orf virus (ORFV) is a parapoxvirus that infects sheep, goats and man. In humans, the virus induces acute, pustular skin lesions that can develop into a progressive disease. Humans are susceptible to reinfection with ORFV and rare cases of persistent infection have been reported. ORFV encodes several immunomodulators, including a homologue of interleukin-10 (ORFV IL-10), that may explain these phenomena. The immunosuppressive effects of ORFV IL-10 on immature human dendritic cells (DCs) cultured from blood-derived monocytes (MoDCs) were investigated. MoDCs exposed simultaneously to lipopolysaccharide and ORFV IL-10 showed enhanced ovalbumin-FITC uptake and reduced IL-12 expression, indicating inhibition of maturation. Moreover, ORFV IL-10 inhibited the upregulation of DC cell-surface activation and maturation markers MHC II, CD80, CD83 and CD86 and inhibited the capacity of MoDCs to activate CD4(+) T cells in an oxidative mitogenesis assay. These findings suggest that ORFV IL-10 may influence the development of acquired immunity in humans by impairing DC function.

Zoonotic poxvirus infections in humans

PURPOSE OF REVIEW

The 2003 USA monkeypox epidemic caused by imported African rodents, newly emergent poxvirus zoonoses in Brazil and the possible use of variola virus for biological warfare has led to renewed interest in poxviruses and anti-poxviral therapies. Increasing foreign travel and importation of exotic animal species increases the likelihood of poxvirus infections occurring outside their usual geographical range and diagnostic delay has important implications. The present review provides an overview of these rare zoonoses.

RECENT FINDINGS

Three genera of Poxviridae are known to cause human zoonoses: orthopoxviruses, parapoxviruses and yatapoxvirus. Most cases are occupational, sporadic and have few cutaneous lesions with low morbidity. The exception is monkeypox, similar to smallpox, with significant morbidity and childhood mortality. Molecular characterization using polymerase chain reaction (PCR) amplification and other methods provides accurate phylogenetic identification and suggests that a cowpox-like virus is the probable ancestor of variola and other zoonotic poxviruses. DNA genomic sequencing of the Brazilian Cantagalo and Araçatuba viruses shows a close relationship to vaccinia virus. Poxviruses have potential in cancer immunotherapy and their ability to evade host-cell immune responses may provide a basis for new antipoxvirus therapies. Other agents, particularly nucleoside phosphonates such as cidofovir, show therapeutic action against poxviruses.

SUMMARY

Human zoonotic poxvirus infections are rare but increasingly encountered outside their usual geographical range. The 2003 USA monkeypox outbreak emphasizes the importance of early accurate diagnosis, particularly because increasing numbers of immunosuppressed individuals increases the potential for severe or fatal infections. PCR methodology enables accurate phylogenetic typing and has identified new diseases, but rapid, reliable methods must be made available for clinicians. More research into therapeutic agents for the prevention and treatment of poxvirus infections is required.

Pseudocowpox virus encodes a homolog of vascular endothelial growth factor

We have identified a gene encoding a homolog of vascular endothelial growth factor (VEGF) in the Pseudocowpox virus (PCPV) genome. The predicted protein shows 27% amino acid identity to human VEGF-A. It also shows 41 and 61% amino acid identity to VEGFs encoded by orf virus (ORFV) strains NZ2 and NZ7, respectively. Assays of the expressed VEGF-like protein of PCPV (PCPV(VR634)VEGF) demonstrated that PCPV(VR634)VEGF is mitogenic for endothelial cells and is capable of inducing vascular permeability. PCPV(VR634)VEGF bound VEGF receptor-2 (VEGFR-2) but did not bind VEGFR-1 or VEGFR-3. These results indicate that PCPV(VR634)VEGF is a biologically active member of the VEGF family which shares with the ORFV-encoded VEGFs a receptor binding profile that differs from those of all cellular members of the VEGF family. It seems likely that the biological activities of PCPV(VR634)VEGF contribute to the proliferative and highly vascularized nature of PCPV lesions.

Parapoxviruses: from the lesion to the viral genome

Viruses of the genus parapoxvirus from the family poxviridae cause widespread but localized diseases of small and large ruminants. The economically most important disease is contagious pustular dermatitis or contagious ecthyma among sheep and goats, often simply called orf. The parapoxviruses (PPV) can be transmitted to man leading to localized lesions that are named pseudocowpox or milkers' node as being mostly restricted to the hands and fingers. In cattle two forms of PPV manifestation are commonly observed, the bovine papular stomatitis in young calves and the occurrence of lesions at the udder of cows. We here report about the recent efforts in molecular characterization of orf viruses and the state of the art about the generation of orf virus recombinants. In addition the current knowledge on immune responses against orf viruses and some new data on the behaviour of orf virus recombinants under non-permissive conditions are reported.

Parapoxviruses are strongly inhibited in vitro by cidofovir

Three parapoxviruses which cause orf or related diseases in humans and animals and the orthopoxvirus, vaccinia virus, were tested for their in vitro sensitivity to cidofovir. The 50% inhibitory concentration for the three parapoxviruses was between 0.21 and 0.27 microg/ml and for vaccinia was 1.32 microg/ml. The selectivity index varied from 198 to 264 for the parapoxviruses and was 42 for vaccinia virus. Virus yield assays confirmed the ability of cidofovir to reduce ortho- and parapoxvirus replication. The efficacy of cidofovir against parapoxviruses justifies its evaluation as a candidate drug for the treatment of parapoxvirus infections in humans and animals.