Virulence in murine model shows the existence of two distinct populations of Brazilian Vaccinia virus strains

Single Immunization of a Vaccine Vectored by a Novel Recombinant Vaccinia Virus Affords Effective Protection Against Respiratory Syncytial Virus Infection in Cotton Rats

Respiratory syncytial virus (RSV) is a leading cause of respiratory infections worldwide and disease management measures are hampered by the lack of a safe and effective vaccine against the infection. We constructed a novel recombinant RSV vaccine candidate based on a deletion mutant vaccinia virus platform, in that the host range genes E3L and K3L were deleted (designated as VACVΔE3LΔK3L) and a poxvirus K3L ortholog gene was used as a marker for the rapid and efficient selection of recombinant viruses. The safety of the modified vaccinia virus was investigated by intranasal administration of BALB/c mice with the modified vaccinia vector using a dose known to be lethal in the wild-type Western Reserve. Only a minor loss of body weight by less than 5% and mild pulmonary inflammation were observed, both of which were transient in nature following nasal administration of the high-dose modified vaccinia virus. In addition, the viruses were cleared from the lung in 2 days with no viral invasions of the brain and other vital organs. These results suggest that the virulence of the virus has been essentially abolished. We then investigated the efficiency of the vector for the delivery of vaccines against RSV through comparison with another RSV vaccine delivered by the widely used Modified Vaccinia virus Ankara (MVA) backbone. In the cotton rats, we found a single intramuscular administration of VACVΔE3LΔK3L-vectored vaccine elicited immune responses and protection at a level comparable to the MVA-vectored vaccine against RSV infection. The distinct features of this novel VACV vector, such as an E3L deletion for attenuation and a K3L ortholog for positive selection and high efficiency for vaccine delivery, could provide unique advantages to the application of VACV as a platform for vaccine development.

Zoonotic vaccinia virus strains belonging to different genetic clades exhibit immunomodulation abilities that are proportional to their virulence

BACKGROUND

The vaccinia virus (VACV) isolates, Guarani P1 virus (GP1V) and Passatempo virus (PSTV), were isolated during zoonotic outbreaks in Brazil. Each one of them belongs to two different VACV clades, defined by biological aspects that include virulence in mice and phylogenetic analysis. Considering that information about how vaccinia viruses from different groups elicit immune responses in animals is scarce, we investigated such responses in mice infected either by GP1V (group 2) or PSTV (group 1), using VACV Western Reserve strain (VACV-WR) as control.

METHODS

The severity of the infections was evaluated in BALB/c mice considering diverse clinical signs and defined scores, and the immune responses triggered by GP1V and PSTV infections were analysed by immune cell phenotyping and intra-cytoplasmic cytokines detection.

RESULTS

We detected a reduction in total lymphocytes (CD3 +), macrophages (CD14 +), and NK cells (CD3-CD49 +) in animals infected with VACV-WR or GP1V. The VACV-WR and GP1V viruses, belonging to the most virulent group in a murine model, were able to down-modulate the cell immune responses upon mice infection. In contrast, PSTV, a virus considered less virulent in a murine model, showed little ability to down-modulate the mice immune responses. Mice infected with VACV-WR and GP1V viruses presented significant weight loss and developed lesions in their spleens, as well as damage to liver and lungs whereas mice infected with PSTV developed only moderate clinical signs.

CONCLUSIONS

Our results suggest that VACV immunomodulation in vivo is clade-related and is proportional to the strain's virulence upon infection. Our data corroborate the classification of the different Brazilian VACV isolates into clades 1 and 2, taking into account not only phylogenetic criteria, but also clinical and immunological data.

Twenty Years after Bovine Vaccinia in Brazil: Where We Are and Where Are We Going?

Orthopoxvirus (OPV) infections have been present in human life for hundreds of years. It is known that Variola virus (VARV) killed over 300 million people in the past; however, it had an end thanks to the physician Edward Jenner (who developed the first vaccine in history) and also thanks to a massive vaccination program in the 20th century all over the world. Although the first vaccine was created using the Cowpox virus (CPXV), it turned out later that the Vaccinia virus was the one used during the vaccination program. VACV is the etiological agent of bovine vaccinia (BV), a zoonotic disease that has emerged in Brazil and South America in the last 20 years. BV has a great impact on local dairy economies and is also a burden to public health. In this review, we described the main events related to VACV and BV emergence in Brazil and South America, the increase of related scientific studies, and the issues that science, human and animal medicine are going to face if we do not be on guard to this virus and its disease.

Here, There, and Everywhere: The Wide Host Range and Geographic Distribution of Zoonotic Orthopoxviruses

The global emergence of zoonotic viruses, including poxviruses, poses one of the greatest threats to human and animal health. Forty years after the eradication of smallpox, emerging zoonotic orthopoxviruses, such as monkeypox, cowpox, and vaccinia viruses continue to infect humans as well as wild and domestic animals. Currently, the geographical distribution of poxviruses in a broad range of hosts worldwide raises concerns regarding the possibility of outbreaks or viral dissemination to new geographical regions. Here, we review the global host ranges and current epidemiological understanding of zoonotic orthopoxviruses while focusing on orthopoxviruses with epidemic potential, including monkeypox, cowpox, and vaccinia viruses.

The Virulence of Different Vaccinia Virus Strains Is Directly Proportional to Their Ability To Downmodulate Specific Cell-Mediated Immune Compartments In Vivo

Vaccinia virus (VACV) is a notorious virus for a number of scientific reasons; however, most of its notoriety comes from the fact that it was used as a vaccine against smallpox, being ultimately responsible for the eradication of that disease. Nonetheless, many different vaccinia virus strains have been obtained over the years; some are suitable to be used as vaccines, whereas others are virulent and unsuitable for this purpose. Interestingly, different vaccinia virus strains elicit different immune responses in vivo, and this is a direct result of the genomic differences among strains. In order to evaluate the net result of virus-encoded immune evasion strategies of vaccinia viruses, we compared antiviral immune responses in mice intranasally infected by the highly attenuated and nonreplicative MVA strain, the attenuated and replicative Lister strain, or the virulent WR strain. Overall, cell responses elicited upon WR infections are downmodulated compared to those elicited by MVA and Lister infections, especially in determined cell compartments such as macrophages/monocytes and CD4⁺ T cells. CD4⁺ T cells are not only diminished in WR-infected mice but also less activated, as evaluated by the expression of costimulatory molecules such as CD25, CD212, and CD28 and by the production of cytokines, including tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), interleukin-4 (IL-4), and IL-10. On the other hand, MVA infections are able to induce strong T-cell responses in mice, whereas Lister infections consistently induced responses that were intermediary between those induced by WR and MVA. Together, our results support a model in which the virulence of a VACV strain is proportional to its potential to downmodulate the host's immune responses.IMPORTANCE Vaccinia virus was used as vaccine against smallpox and was instrumental in the successful eradication of that disease. Although smallpox vaccination is no longer in place in the overall population, the use of vaccinia virus in the development of viral vector-based vaccines has become popular. Nonetheless, different vaccinia virus strains are known and induce different immune responses. To look into this, we compared immune responses triggered by mouse infections with the nonreplicative MVA strain, the attenuated Lister strain, or the virulent WR strain. We observed that the WR strain was capable of downmodulating mouse cell responses, whereas the highly attenuated MVA strain induced high levels of cell-mediated immunity. Infections by the intermediately attenuated Lister strain induced cell responses that were intermediary between those induced by WR and MVA. We propose that the virulence of a vaccinia virus strain is directly proportional to its ability to downmodulate specific compartments of antiviral cell responses.

Respiratory infection due to direct contact with rabbit-skin powder contaminated by vaccinia virus

Vaccinia virus infection was diagnosed in five male workers directly exposed to rabbit-skin powder contaminated by vaccinia virus via skin contact and inhalation. Four of the workers had been vaccinated against smallpox. Their clinical symptoms were severe, especially in the lungs; however, all symptoms improved after treatment.

Bovine Vaccinia: Insights into the Disease in Cattle

Bovine vaccinia (BV), caused by Vaccinia virus (VACV), is a zoonosis characterized by exanthematous lesions in the teats of dairy cows and the hands of milkers and is an important public health issue. Severe VACV-induced lesions in the teats and udder of cows and buffaloes could lead to mastitis and other secondary infections, thereby reducing productivity and resulting in economic losses to the dairy industry. In Brazil, BV re-emerged in the late 1990s and is now endemic in most of the Brazilian territory. In the last 15 years, much effort has been made to know more about this disease and its epidemiology, etiologic agents, and interactions with the host and the environment. In this review, we describe the known dynamics of VACV infection in cattle and the viral shedding routes, as well as the relevance of BV for animal and public health.

In vitro susceptibility to ST-246 and Cidofovir corroborates the phylogenetic separation of Brazilian Vaccinia virus into two clades

The Orthopoxvirus (OPV) genus of the Poxviridae family contains several human pathogens, including Vaccinia virus (VACV), which have been implicating in outbreaks of a zoonotic disease called Bovine Vaccinia in Brazil. So far, no approved treatment exists for OPV infections, but ST-246 and Cidofovir (CDV) are now in clinical development. Therefore, the objective of this work was to evaluate the susceptibility of five strains of Brazilian VACV (Br-VACV) to ST-246 and Cidofovir. The susceptibility of these strains to both drugs was evaluated by plaque reduction assay, extracellular virus's quantification in the presence of ST-246 and one-step growth curve in cells treated with CDV. Besides that, the ORFs F13L and E9L were sequenced for searching of polymorphisms associated with drug resistance. The effective concentration of 50% (EC₅₀) from both drugs varies significantly for different strains (from 0.0054 to 0.051 μM for ST-246 and from 27.14 to 61.23 μM for CDV). ST-246 strongly inhibits the production of extracellular virus for all isolates in concentrations as low as 0.1 μM and it was observed a relevant decrease of progeny production for all Br-VACV after CDV treatment. Sequencing of the F13L and E9L ORFs showed that Br-VACV do not present the polymorphism(s) associated with resistance to ST-246 and CDV. Taken together, our results showed that ST-246 and CDV are effective against diverse, wild VACV strains and that the susceptibility of Br-VACV to these drugs mirrored the phylogenetic split of these isolates into two groups. Thus, both ST-246 and CDV are of great interest as compounds to treat individuals during Bovine Vaccinia outbreaks in Brazil.

A Model to Detect Autochthonous Group 1 and 2 Brazilian Vaccinia virus Coinfections: Development of a qPCR Tool for Diagnosis and Pathogenesis Studies

Vaccinia virus (VACV) is the etiological agent of bovine vaccinia (BV), an emerging zoonosis that has been associated with economic losses and social effects. Despite increasing reports of BV outbreaks in Brazil, little is known about the biological interactions of Brazilian VACV (VACV-BR) isolates during coinfections; furthermore, there are no tools for the diagnosis of these coinfections. In this study, a tool to co-detect two variants of VACV was developed to provide new information regarding the pathogenesis, virulence profile, and viral spread during coinfection with VACV-BR isolates. To test the quantitative polymerase chain reactions (qPCR) tool, groups of BALB/c mice were intranasally monoinfected with Pelotas virus 1-Group II (PV1-GII) and Pelotas virus 2-Group I (PV2-GI), or were coinfected with PV1-GII and PV2-GI. Clinical signs of the mice were evaluated and the viral load in lung and spleen were detected using simultaneous polymerase chain reactions (PCR) targeting the A56R (hemagglutinin) gene of VACV. The results showed that qPCR for the quantification of viral load in coinfection was efficient and highly sensitive. Coinfected mice presented more severe disease and a higher frequency of VACV detection in lung and spleen, when compared to monoinfected groups. This study is the first description of PV1 and PV2 pathogenicity during coinfection in mice, and provides a new method to detect VACV-BR coinfections.

Serologic and Molecular Evidence of Vaccinia Virus Circulation among Small Mammals from Different Biomes, Brazil

Vaccinia virus (VACV) is a zoonotic agent that causes a disease called bovine vaccinia, which is detected mainly in milking cattle and humans in close contact with these animals. Even though many aspects of VACV infection have been described, much is still unknown about its circulation in the environment and its natural hosts/reservoirs. To investigate the presence of Orthopoxvirus antibodies or VACV DNA, we captured small rodents and marsupials in 3 areas of Minas Gerais state, Brazil, and tested their samples in a laboratory. A total of 336 animals were tested; positivity ranged from 18.1% to 25.5% in the 3 studied regions located in different biomes, including the Atlantic Forest and the Cerrado. Analysis of nucleotide sequences indicated co-circulation of VACV groups I and II. Our findings reinforce the possible role played by rodents and marsupials in VACV maintenance and its transmission chain.

Serro 2 Virus Highlights the Fundamental Genomic and Biological Features of a Natural Vaccinia Virus Infecting Humans

Vaccinia virus (VACV) has been implicated in infections of dairy cattle and humans, and outbreaks have substantially impacted local economies and public health in Brazil. During a 2005 outbreak, a VACV strain designated Serro 2 virus (S2V) was collected from a 30-year old male milker. Our aim was to phenotypically and genetically characterize this VACV Brazilian isolate. S2V produced small round plaques without associated comets when grown in BSC40 cells. Furthermore, S2V was less virulent than the prototype strain VACV-Western Reserve (WR) in a murine model of intradermal infection, producing a tiny lesion with virtually no surrounding inflammation. The genome of S2V was sequenced by primer walking. The coding region spans 184,572 bp and contains 211 predicted genes. Mutations in envelope genes specifically associated with small plaque phenotypes were not found in S2V; however, other alterations in amino acid sequences within these genes were identified. In addition, some immunomodulatory genes were truncated in S2V. Phylogenetic analysis using immune regulatory-related genes, besides the hemagglutinin gene, segregated the Brazilian viruses into two clusters, grouping the S2V into Brazilian VACV group 1. S2V is the first naturally-circulating human-associated VACV, with a low passage history, to be extensively genetically and phenotypically characterized.

Natural Vaccinia Virus Infection: Diagnosis, Isolation, and Characterization

Natural infections of Vaccinia virus (VACV)-the prototype species of the Orthopoxvirus genus, from the family Poxviridae and subfamily Chordopoxvirinae-cause an occupational emergent zoonotic disease that is primarily associated with the handling of infected dairy cattle. In humans, VACV infection is characterized by skin lesions, primarily on the hands, and accompanied by systemic symptoms such as fever, myalgia, headache, and lymphadenopathy. The diagnosis of VACV is usually performed according to the methods described for other orthopoxviruses. This unit describes the methods utilized to obtain clinical samples, the serological and molecular techniques used for diagnosis, and the isolation methods and techniques used for molecular and biological characterization of the viruses. © 2016 by John Wiley & Sons, Inc.

Genomic Analysis, Phenotype, and Virulence of the Historical Brazilian Smallpox Vaccine Strain IOC: Implications for the Origins and Evolutionary Relationships of Vaccinia Virus

Smallpox was declared eradicated in 1980 after an intensive vaccination program using different strains of vaccinia virus (VACV; Poxviridae). VACV strain IOC (VACV-IOC) was the seed strain of the smallpox vaccine manufactured by the major vaccine producer in Brazil during the smallpox eradication program. However, little is known about the biological and immunological features as well as the phylogenetic relationships of this first-generation vaccine. In this work, we present a comprehensive characterization of two clones of VACV-IOC. Both clones had low virulence in infected mice and induced a protective immune response against a lethal infection comparable to the response of the licensed vaccine ACAM2000 and the parental strain VACV-IOC. Full-genome sequencing revealed the presence of several fragmented virulence genes that probably are nonfunctional, e.g., F1L, B13R, C10L, K3L, and C3L. Most notably, phylogenetic inference supported by the structural analysis of the genome ends provides evidence of a novel, independent cluster in VACV phylogeny formed by VACV-IOC, the Brazilian field strains Cantagalo (CTGV) and Serro 2 viruses, and horsepox virus, a VACV-like virus supposedly related to an ancestor of the VACV lineage. Our data strongly support the hypothesis that CTGV-like viruses represent feral VACV that evolved in parallel with VACV-IOC after splitting from a most recent common ancestor, probably an ancient smallpox vaccine strain related to horsepox virus. Our data, together with an interesting historical investigation, revisit the origins of VACV and propose new evolutionary relationships between ancient and extant VACV strains, mainly horsepox virus, VACV-IOC/CTGV-like viruses, and Dryvax strain.

IMPORTANCE

First-generation vaccines used to eradicate smallpox had rates of adverse effects that are not acceptable by current health care standards. Moreover, these vaccines are genetically heterogeneous and consist of a pool of quasispecies of VACV. Therefore, the search for new-generation smallpox vaccines that combine low pathogenicity, immune protection, and genetic homogeneity is extremely important. In addition, the phylogenetic relationships and origins of VACV strains are quite nebulous. We show the characterization of two clones of VACV-IOC, a unique smallpox vaccine strain that contributed to smallpox eradication in Brazil. The immunogenicity and reduced virulence make the IOC clones good options for alternative second-generation smallpox vaccines. More importantly, this study reveals the phylogenetic relationship between VACV-IOC, feral VACV established in nature, and the ancestor-like horsepox virus. Our data expand the discussion on the origins and evolutionary connections of VACV lineages.

Extent of Systemic Spread Determines CD8+ T Cell Immunodominance for Laboratory Strains, Smallpox Vaccines, and Zoonotic Isolates of Vaccinia Virus

CD8(+) T cells that recognize virus-derived peptides presented on MHC class I are vital antiviral effectors. Such peptides presented by any given virus vary greatly in immunogenicity, allowing them to be ranked in an immunodominance hierarchy. However, the full range of parameters that determine immunodominance and the underlying mechanisms remain unknown. In this study, we show across a range of vaccinia virus strains, including the current clonal smallpox vaccine, that the ability of a strain to spread systemically correlated with reduced immunodominance. Reduction in immunodominance was observed both in the lymphoid system and at the primary site of infection. Mechanistically, reduced immunodominance was associated with more robust priming and especially priming in the spleen. Finally, we show this is not just a property of vaccine and laboratory strains of virus, because an association between virulence and immunodominance was also observed in isolates from an outbreak of zoonotic vaccinia virus that occurred in Brazil.

Vaccinia virus Transmission through Experimentally Contaminated Milk Using a Murine Model

Bovine vaccinia (BV) is a zoonosis caused by Vaccinia virus (VACV), which affects dairy cattle and humans. Previous studies have detected the presence of viable virus particles in bovine milk samples naturally and experimentally contaminated with VACV. However, it is not known whether milk contaminated with VACV could be a route of viral transmission. However, anti-Orthopoxvirus antibodies were detected in humans from BV endemic areas, whom had no contact with affected cows, which suggest that other VACV transmission routes are possible, such as consumption of contaminated milk and dairy products. Therefore, it is important to study the possibility of VACV transmission by contaminated milk. This study aimed to examine VACV transmission, pathogenesis and shedding in mice orally inoculated with experimentally contaminated milk. Thirty mice were orally inoculated with milk containing 107 PFU/ml of VACV, and ten mice were orally inoculated with uncontaminated milk. Clinical examinations were performed for 30 consecutive days, and fecal samples and oral swabs (OSs) were collected every other day. Mice were euthanized on predetermined days, and tissue and blood samples were collected. Nested-PCR, plaque reduction neutralization test (PRNT), viral isolation, histopathology, and immunohistochemistry (IHC) methods were performed on the collected samples. No clinical changes were observed in the animals. Viral DNA was detected in feces, blood, OSs and tissues, at least in one of the times tested. The lungs displayed moderate to severe interstitial lymphohistiocytic infiltrates, and only the heart, tonsils, tongue, and stomach did not show immunostaining at the IHC analysis. Neutralizing antibodies were detected at the 20th and 30th days post infection in 50% of infected mice. The results revealed that VACV contaminated milk could be a route of viral transmission in mice experimentally infected, showing systemic distribution and shedding through feces and oral mucosa, albeit without exhibiting any clinical signs.

From lesions to viral clones: biological and molecular diversity amongst autochthonous Brazilian vaccinia virus

Vaccinia virus (VACV) has had an important role for humanity because of its use during the smallpox eradication campaign. VACV is the etiologic agent of the bovine vaccinia (BV), an emerging zoonosis that has been associated with economic, social, veterinary and public health problems, mainly in Brazil and India. Despite the current and historical VACV importance, there is little information about its circulation, prevalence, origins and maintenance in the environment, natural reservoirs and diversity. Brazilian VACV (VACV-BR) are grouped into at least two groups based on genetic and biological diversity: group 1 (G1) and group 2 (G2). In this study, we went to the field and investigated VACV clonal diversity directly from exanthemous lesions, during BV outbreaks. Our results demonstrate that the G1 VACV-BR were more frequently isolated. Furthermore, we were able to co-detect the two variants (G1 and G2) in the same sample. Molecular and biological analysis corroborated previous reports and confirmed the co-circulation of two VACV-BR lineages. The detected G2 clones presented exclusive genetic and biological markers, distinct to reference isolates, including VACV-Western Reserve. Two clones presented a mosaic profile, with both G1 and G2 features based on the molecular analysis of A56R, A26L and C23L genes. Indeed, some SNPs and INDELs in A56R nucleotide sequences were observed among clones of the same virus population, maybe as a result of an increased mutation rate in a mixed population. These results provide information about the diversity profile in VACV populations, highlighting its importance to VACV evolution and maintenance in the environment.

Serological study of vaccinia virus reservoirs in areas with and without official reports of outbreaks in cattle and humans in São Paulo, Brazil

Vaccinia virus (VACV), the etiological agent of an exanthematic disease, has been associated with several bovine outbreaks in Brazil since the end of the global vaccination campaign against smallpox. It was previously believed that the vaccine virus used for the WHO global campaign had adapted to an unknown wild reservoir and was sporadically re-emerging in outbreaks in cattle and milkers. At present, it is known that Brazilian VACV is phylogenetically different from the vaccinia virus vaccinal strain, but its origin remains unknown. This study assessed the seroprevalence of orthopoxviruses in domestic and wild animals and farmers from 47 farms in three cities in the southwest region of the state of São Paulo with or without official reports of outbreaks in cattle or humans. Our data indicate a low seroprevalence of antibodies in wild animals and raise interesting questions about the real potential of wild rodents and marsupials as VACV reservoirs, suggesting other routes through which VACV can be spread.

Group 2 vaccinia virus, Brazil

In 2011, vaccinia virus caused an outbreak of bovine vaccinia, affecting dairy cattle and dairy workers in Brazil. Genetic and phenotypic analyses identified this isolate as distinct from others recently identified, thereby reinforcing the hypothesis that different vaccinia virus strains co-circulate in Brazil.

Characterization of a new Vaccinia virus isolate reveals the C23L gene as a putative genetic marker for autochthonous Group 1 Brazilian Vaccinia virus

Since 1999, several Vaccinia virus (VACV) isolates, the etiological agents of bovine vaccinia (BV), have been frequently isolated and characterized with various biological and molecular methods. The results from these approaches have grouped these VACV isolates into two different clusters. This dichotomy has elicited debates surrounding the origin of the Brazilian VACV and its epidemiological significance. To ascertain vital information to settle these debates, we and other research groups have made efforts to identify molecular markers to discriminate VACV from other viruses of the genus Orthopoxvirus (OPV) and other VACV-BR groups. In this way, some genes have been identified as useful markers to discriminate between the VACV-BR groups. However, new markers are needed to infer ancestry and to correlate each sample or group with its unique epidemiological and biological features. The aims of this work were to characterize a new VACV isolate (VACV DMTV-2005) molecularly and biologically using conserved and non-conserved gene analyses for phylogenetic inference and to search for new genes that would elucidate the VACV-BR dichotomy. The VACV DMTV-2005 isolate reported in this study is biologically and phylogenetically clustered with other strains of Group 1 VACV-BR, the most prevalent VACV group that was isolated during the bovine vaccinia outbreaks in Brazil. Sequence analysis of C23L, the gene that encodes for the CC-chemokine-binding protein, revealed a ten-nucleotide deletion, which is a new Group 1 Brazilian VACV genetic marker. This deletion in the C23L open reading frame produces a premature stop-codon that is shared by all Group 1 VACV-BR strains and may also reflect the VACV-BR dichotomy; the deletion can also be considered to be a putative genetic marker for non-virulent Brazilian VACV isolates and may be used for the detection and molecular characterization of new isolates.

Bovine vaccinia, a systemic infection: evidence of fecal shedding, viremia and detection in lymphoid organs

Bovine vaccinia (BV) is a zoonosis caused by Vaccinia virus (VACV) that affects dairy cattle and milkers, causing economic losses and impacting animal and human health. Based on the clinical presentation, BV appears to be a localized disease, with lesions restricted to the skin of affected individuals. However, there are no studies on the pathogenesis of the disease in cows to determine if there is a systemic spread of the virus and if there are different ways of VACV shedding. The objective of this work was to study if there is a systemic spread of VACV in experimentally infected cows and to study the kinetics of VACV circulation in the blood and shedding in the feces of these animals. To this end, eight crossbred lactating cows were used. Three teats of each cow were inoculated with the GP2V strain of VACV. All animals were monitored daily, and blood and fecal samples were collected for 67 days post-infection (dpi). After this period, four of these previously infected cows were immunosuppressed using dexamethasone. Viral DNA was continuously detected and quantified in the blood and feces of these animals in an intermittent way, even after the resolution of the lesions. At slaughter, tissues were collected, and viral DNA was detected and quantified in the mesenteric and retromammary lymph nodes, ileum, spleen and liver. The detection of VACV DNA in the feces for a longer period (67 dpi) and in the lymphatic organs provides new evidence about VACV elimination and suggests that BV could be a systemic infection with a chronic course and viral shedding through the feces.

Vaccinia viruses isolated from skin infection in horses produced cutaneous and systemic disease in experimentally infected rabbits

The susceptibility of rabbits to two isolates of Vaccinia virus (VACV) recovered from cutaneous disease in horses in Southern Brazil was investigated. Rabbits were inoculated in the ear skin with both VACV isolates, either in single or mixed infection. All inoculated animals presented local skin lesions characterized by hyperaemia, papules, vesicles, pustules and ulcers. Infectious virus was detected in the lungs and intestine of rabbits that died during acute disease. Histological examination of the skin revealed changes characteristic of those associated with members of the genus Orthopoxvirus. These results demonstrate that rabbits develop skin disease accompanied by systemic signs upon intradermal inoculation of these two equine VACV isolates, either alone or in combination, opening the way for using rabbits to study selected aspects of the biology and pathogenesis of VACV infection.

An intradermal model for vaccinia virus pathogenesis in mice

Intradermal injection of vaccinia virus in the ear pinnae of mice provides a model of dermal infection and vaccination. The key features of this model are the appearance of a lesion on the surface of the ear that can be measured as a clinical sign of disease and substantial growth of virus in the infected skin in the absence of systemic spread. In addition, infected ears can be easily removed to allow virological, histological, and cellular analyses. Finally, evaluation of the roles of virus (and presumably also host) genes in vaccinia virus pathogenesis in the intradermal model can yield different results than similar experiments using other routes and may reveal otherwise unknown functions.

Vaccinia viruses isolated from cutaneous disease in horses are highly virulent for rabbits

Two genotypically distinct Vaccinia viruses (VACV), named P1V and P2V, were isolated from an outbreak of cutaneous disease in horses in Southern Brazil. We herein investigated the susceptibility of rabbits, a proposed animal model, to P1V and P2V infection. Groups of weanling rabbits were inoculated intranasally (IN) with P1V or P2V at low (10(2.5) TCID50), medium (10(4.5)TCID50), or high titer (10(6.5)TCID50). Rabbits inoculated with medium and high titers shed virus in nasal secretions and developed serous to hemorrhagic nasal discharge and severe respiratory distress, followed by progressive apathy and high lethality. Clinical signs appeared around days 3-6 post-inoculation (pi) and lasted up to the day of death or euthanasia (around days 5-10). Virus shedding and clinical signs were less frequent in rabbits inoculated with low virus titers. Viremia was detected in all groups, with different frequencies. Viral DNA was detected in the feces of a few animals inoculated with P1V and P2V, low titer, and with P2V at high titer. Gross necropsy findings and histological examination showed diffuse interstitial fibrousing pneumonia with necrosuppurative bronchopneumonia and intestinal liquid content. Neutralizing antibodies were detected in all inoculated animals surviving beyond day 9 pi. These results show that rabbits are highly susceptible to VACV isolated from horses, and develop severe respiratory and systemic disease upon IN inoculation. Thus, rabbits may be used to study selected aspects of VACV infection and disease.

Filling one more gap: experimental evidence of horizontal transmission of Vaccinia virus between bovines and rodents

Vaccinia virus (VACV) has been associated with several exanthematic outbreaks in bovine, human, and equine species in Brazilian rural areas. Little is known about VACV reservoirs, although it is believed that rodents could be associated with VACV outbreaks. With the goal of filling one more gap in the VACV ecological puzzle, the present work aimed at mimicking a potential transmission route of VACV between cows and rodents, both known as natural VACV hosts. Balb/c mice were exposed to feces of experimentally VACV infected cows for 20 days, and samples from these mice were examined by using molecular and serological tests. VACV DNA was detected in feces and blood samples after several days of exposure; infectious VACV particles were also detected in the feces. The presence of anti-VACV neutralizing antibodies in murine sera further suggested horizontal transmission. If the transmission model described here can be applied to natural environments, exposure to bovine feces could be considered a risk factor for the spread of VACV; consequently, the traditional use of bovine manure as a fertilizer in agricultural activities may be promoting the infection of rodents.

Zoonotic Brazilian Vaccinia virus: from field to therapy

Vaccinia virus (VACV), the prototype species of the Orthopoxvirus (OPV) genus, causes an occupational zoonotic disease in Brazil that is primarily associated with the handling of infected dairy cattle. Cattle and human outbreaks have been described in southeastern Brazil since 1999 and have now occurred in almost half of the territory. Phylogenetic studies have shown high levels of polymorphisms among isolated VACVs, which indicate the existence of at least two genetically divergent clades; this has also been proven in virulence assays in a mouse model system. In humans, VACV infection is characterized by skin lesions, primarily on the hands, accompanied by systemic symptoms such as fever, myalgia, headache and lymphadenopathy. In this review, we will discuss the virological, epidemiological, ecological and clinical aspects of VACV infection, its diagnosis and compounds that potentially could be used for the treatment of severe cases.

The interplay between Araçatuba virus and host signaling pathways: role of PI3K/Akt in viral replication

In this study, we describe the interaction between Araçatuba virus (ARAV), a naturally occurring Brazilian vaccinia virus isolated from an outbreak at a dairy farm, and the host cell's signal transduction pathways. Even though ARAV infection led to phosphorylation of MAPKs MEK/ERK, JNK, and p38MAPK, genetic or pharmacological inhibition of these pathways had no impact on viral replication. We also provide evidence that ARAV stimulated the phosphorylation of Akt (PKB) at serine 473 (S473-P), a signaling event that is required for full activation of Akt during the infectious cycle. Furthermore, pharmacological inhibition of PI3K (LY294002) abrogated ARAV-induced Akt activation (S473-P) and affected early and late viral gene expression, which was followed by a decrease in virus yield (~1 log). Taken together, our data shed some light onto the biological differences between ARAV and vaccinia virus strain WR (VACV-WR), which could contribute, at least in part, to the low-virulence phenotype displayed by ARAV. Thus, while the requirement for the PI3K/Akt pathway for successful ARAV replication is also shared with VACV-WR and cowpox virus strain BR (CPXV-BR), ARAV showed a lower replicative capacity, as well as a smaller plaque-size phenotype after infection of A31 cells when compared to VACV-WR.

Zoonotic vaccinia virus outbreaks in Brazil

The vaccinia virus (VACV) was used as a live vaccine during the WHO-led smallpox eradication campaign in the second half of the 20th century. The program culminated with the obliteration of the disease, one of the most important achievements in modern medicine. Interestingly, one of the key factors in the successful vaccination campaign – the VACV itself – is poorly understood in relation to its natural reservoirs, evolutionary history and origins, being frequently considered extinct as a naturally occurring virus. Nevertheless, orthopoxviruses other than variola virus have been known to circulate in Brazil since the early 1960s. More specifically, VACV has been associated with naturally acquired infections in humans, cattle and possibly other reservoirs since 1999, when bovine vaccinia outbreaks started to be consistently described year after year. In this article, we list and discuss the most important VACV outbreaks that have occurred in Brazil in the last 20 years. Phylogenetic issues are considered, as the latest studies point to large genetic variance among isolates. Clinical and epidemiological data, both published and new, are presented.

A-type inclusion bodies: a factor influencing cowpox virus lesion pathogenesis

The family Poxviridae comprises the most complex animal DNA viruses. During some poxvirus infections, A-type inclusion bodies (ATIs), codified by the ati gene, are produced. Although some studies have compared poxviruses that encode these inclusion bodies with those that do not, the biological function of ATIs is poorly understood. A recombinant ati-deleted cowpox virus was constructed and compared with the wild-type virus in in vitro experiments including electron microscopy and plaque and viral growth assays. No significant differences were observed in vitro. This reinforces the conclusion that the inclusion body is not essential for in vitro viral replication and morphogenesis. Additionally, different lesion progressions in vivo were observed by macroscopic and histological analysis, suggesting that the presence or absence of ATIs could result in different healing dynamics. This is the first time that the role of ATIs during viral replication has been studied based solely on one variable, the presence or absence of ATIs.

Bovine vaccinia outbreaks: detection and isolation of vaccinia virus in milk samples

The vaccinia virus (VACV), which causes exanthemous lesions in dairy cattle and humans, has been associated with several bovine vaccinia outbreaks in Brazil. Currently, no data are available about the safety of milk produced in VACV-affected areas. In this study, 47 milk samples were collected during bovine vaccinia outbreaks and submitted to viral isolation, DNA detection, and nucleotide sequencing of the conserved tk gene. The appearance of characteristic white pocks on the chorioallantoic membranes of chicken eggs, in association with viral cytopathic effects in chicken embryo fibroblasts and phylogenetic data, strongly suggest milk contamination by VACV. This is the first report of VACV detection in and isolation from milk.

One more piece in the VACV ecological puzzle: could peridomestic rodents be the link between wildlife and bovine vaccinia outbreaks in Brazil?

Background

Despite the fact that smallpox eradication was declared by the World Health Organization (WHO) in 1980, other poxviruses have emerged and re-emerged, with significant public health and economic impacts. Vaccinia virus (VACV), a poxvirus used during the WHO smallpox vaccination campaign, has been involved in zoonotic infections in Brazilian rural areas (Bovine Vaccinia outbreaks – BV), affecting dairy cattle and milkers. Little is known about VACV's natural hosts and its epidemiological and ecological characteristics. Although VACV was isolated and/or serologically detected in Brazilian wild animals, the link between wildlife and farms has not yet been elucidated.

Methodology/Principal Findings

In this study, we describe for the first time, to our knowledge, the isolation of a VACV (Mariana virus - MARV) from a mouse during a BV outbreak. Genetic data, in association with biological assays, showed that this isolate was the same etiological agent causing exanthematic lesions observed in the cattle and human inhabitants of a particular BV-affected area. Phylogenetic analysis grouped MARV with other VACV isolated during BV outbreaks.

Conclusion/Significance

These data provide new biological and epidemiological information on VACV and lead to an interesting question: could peridomestic rodents be the link between wildlife and BV outbreaks?