Danilo Bretas de Oliveira

The large marseillevirus explores different entry pathways by forming giant infectious vesicles

ABSTRACT Triggering the amoebal phagocytosis process is a sine qua non condition for most giant viruses to initiate their replication cycle and consequently to promote their progeny formation. It is well known that the amoebal phagocytosis process requires the recognition of particles of >500 nm, and most amoebal giant viruses meet this requirement, such as mimivirus, pandoravirus, pithovirus, and mollivirus. However, in the context of the discovery of amoebal giant viruses in the last decade, Marseillevirus marseillevirus (MsV) has drawn our attention, because despite its ability to successfully replicate in Acanthamoeba, remarkably it does not fulfill the >500-nm condition, since it presents an ∼250-nm icosahedrally shaped capsid. We deeply investigated the MsV cycle by using a set of methods, including virological, molecular, and microscopic (immunofluorescence, scanning electron microscopy, and transmission electron microscopy) assays. Our results revealed that MsV is able to form giant vesicles containing dozens to thousands of viral particles wrapped by membranes derived from amoebal endoplasmic reticulum. Remarkably, our results strongly suggested that these giant vesicles are able to stimulate amoebal phagocytosis and to trigger the MsV replication cycle by an acidification-independent process. Also, we observed that MsV entry may occur by the phagocytosis of grouped particles (without surrounding membranes) and by an endosome-stimulated pathway triggered by single particles. Taken together, not only do our data deeply describe the main features of MsV replication cycle, but this is the first time, to our knowledge, that the formation of giant infective vesicles related to a DNA virus has been described. IMPORTANCE Triggering the amoebal phagocytosis process is a sine qua non condition required by most giant viruses to initiate their replication cycle. This process requires the recognition of particles of >500 nm, and many giant viruses meet this requirement. However, MsV is unusual, as despite having particles of ∼250 nm it is able to replicate in Acanthamoeba. Our results revealed that MsV is able to form giant vesicles, containing dozens to thousands of viral particles, wrapped in membranes derived from amoebal endoplasmic reticulum. Remarkably, our results strongly suggest that these giant vesicles are able to stimulate phagocytosis using an acidification-independent process. Our work not only describes the main features of the MsV replication cycle but also describes, for the first time to our knowledge, the formation of huge infective vesicles in a large DNA viruses.

Fluconazole Alters the Polysaccharide Capsule of Cryptococcus gattii and Leads to Distinct Behaviors in Murine Cryptococcosis

Cryptococcus gattii is an emergent human pathogen. Fluconazole is commonly used for treatment of cryptococcosis, but the emergence of less susceptible strains to this azole is a global problem and also the data regarding fluconazole-resistant cryptococcosis are scarce. We evaluate the influence of fluconazole on murine cryptococcosis and whether this azole alters the polysaccharide (PS) from cryptococcal cells. L27/01 strain of C. gattii was cultivated in high fluconazole concentrations and developed decreased drug susceptibility. This phenotype was named L27/01F, that was less virulent than L27/01 in mice. The physical, structural and electrophoretic properties of the PS capsule of L27/01F were altered by fluconazole. L27/01F presented lower antiphagocytic properties and reduced survival inside macrophages. The L27/01F did not affect the central nervous system, while the effect in brain caused by L27/01 strain began after only 12 hours. Mice infected with L27/01F presented lower production of the pro-inflammatory cytokines, with increased cellular recruitment in the lungs and severe pulmonary disease. The behavioral alterations were affected by L27/01, but no effects were detected after infection with L27/01F. Our results suggest that stress to fluconazole alters the capsule of C. gattii and influences the clinical manifestations of cryptococcosis.

A resourceful giant: APMV is able to interfere with the human type I interferon system

Acanthamoeba polyphaga mimivirus (APMV) is a giant, double-stranded virus of the Mimiviridae family that was discovered in 2003. Recent studies have shown that this virus is able to replicate in murine and human phagocytes and might be considered a putative human pathogen that causes pneumonia. However, there is little data regarding APMV and its host defense relationship. In the present study, we investigated how some components of the interferon (IFN) system are stimulated by APMV in human peripheral blood mononuclear cells (PBMCs) and how APMV replication is affected by IFN treatment. Our results demonstrated that APMV is able to replicate in human PBMCs, inducing type I Interferons (IFNs) but inhibiting interferon stimulated genes (ISG) induction by viroceptor and STAT-1 and STAT-2 dephosphorylation independent mechanisms. We also showed that APMV is resistant to the antiviral action of interferon-alpha2 (IFNA2) but is sensitive to the antiviral action of interferon-beta (IFNB1). Our results demonstrated the productive infection of professional phagocytes with APMV and showed that this virus is recognized by the immune system of vertebrates and inhibits it. It provides the first data regarding APMV and the IFN system interaction and raise new and relevant evolutional questions about the relationship between APMV and vertebrate hosts.

Mimivirus Fibrils Are Important for Viral Attachment to the Microbial World by a Diverse Glycoside Interaction Repertoire.

ABSTRACT Acanthamoeba polyphaga mimivirus (APMV) is a giant virus from the Mimiviridae family. It has many unusual features, such as a pseudoicosahedral capsid that presents a starfish shape in one of its vertices, through which the ∼1.2-Mb double-stranded DNA is released. It also has a dense glycoprotein fibril layer covering the capsid that has not yet been functionally characterized. Here, we verified that although these structures are not essential for viral replication, they are truly necessary for viral adhesion to amoebae, its natural host. In the absence of fibrils, APMV had a significantly lower level of attachment to the Acanthamoeba castellanii surface. This adhesion is mediated by glycans, specifically, mannose and N-acetylglucosamine (a monomer of chitin and peptidoglycan), both of which are largely distributed in nature as structural components of several organisms. Indeed, APMV was able to attach to different organisms, such as Gram-positive bacteria, fungi, and arthropods, but not to Gram-negative bacteria. This prompted us to predict that (i) arthropods, mainly insects, might act as mimivirus dispersers and (ii) by attaching to other microorganisms, APMV could be ingested by amoebae, leading to the successful production of viral progeny. To date, this mechanism has never been described in the virosphere. IMPORTANCE APMV is a giant virus that is both genetically and structurally complex. Its size is similar to that of small bacteria, and it replicates inside amoebae. The viral capsid is covered by a dense glycoprotein fibril layer, but its function has remained unknown, until now. We found that the fibrils are not essential for mimivirus replication but that they are truly necessary for viral adhesion to the cell surface. This interaction is mediated by glycans, mainly N-acetylglucosamine. We also verified that APMV is able to attach to bacteria, fungi, and arthropods. This indicates that insects might act as mimivirus dispersers and that adhesion to other microorganisms could facilitate viral ingestion by amoebae, a mechanism never before described in the virosphere.

Spread of Vaccinia Virus to Cattle Herds, Argentina, 2011

To the Editor: Since 1999, several zoonotic outbreaks of vaccinia virus (VACV) infection have been reported in cattle and humans in rural areas of Brazil. The infections have caused exanthematous lesions on cows and persons who milk them, and thus are detrimental to the milk industry and public health services (1,2). In Brazil during the last decade, VACV outbreaks have been detected from the north to the extreme south of the country (1–4). Because Brazil shares extensive boundaries with other South American countries, humans and cattle on dairy and beef-producing farms in those countries may be at risk of exposure to VACV. To determine if VACV has spread from Brazil to Argentina, we investigated the presence of VACV in serum samples from cattle in Argentina. During 2011, we obtained serum samples from 100 animals (50 dairy and 50 beef cattle) on farms in Cordoba, Corrientes, Entre Rios, and Santa Fe Provinces in Argentina (Technical Appendix, panel A). No VACV cases had been reported in humans or cattle in these provinces. However, Corrientes Province borders the Brazilian state of Rio Grande do Sul, where VACVs (Pelotas 1 and Pelotas 2 viruses) were isolated during an outbreak affecting horses in 2008 (2). To determine the presence of neutralizing antibodies in the serum samples, we used an orthopoxvirus 70% plaque-reduction neutralization test as described (4). On the basis of previous studies that detected viral DNA in serum samples (4–6), we used real-time PCR to amplify the highly conserved orthopoxvirus vaccinia growth factor (vgf) gene DNA (P.A. Alves, unpub. methods). To amplify the hemagglutinin (HA) gene DNA from the serum samples, we used real-time PCR with primers as described by de Souza Trindade et al. 2008 (7). The HA PCR products were directly sequenced in both orientations by using specific primers and capillary electrophoresis (Genetic Analyzer 3130; Applied Biosystems, Grand Island, NY, USA). We used ClustalW (http://www.clustal.org) and MEGA4 software (http://megasoftware.net/) to align nucleotide sequences and construct a phylogenetic tree (neighbor-joining method, 1,000 bootstraps) from the obtained HA fragment. Of the 50 dairy cattle samples, 4 (8.0%) had neutralizing antibodies against orthopoxvirus; of these, 3 (75.0%) had titers of 100 neutralizing units (NU)/mL, and 1 (25.0%) had a titer of 400 NU/mL. Of the 50 beef cattle, 8 (16.0%) had antibodies to orthopoxvirus, 1 (12.5%) of which had a titer of 800 NU/mL. Most of the positive samples were from cattle in Corrientes and Entre Rios Provinces (Table). Table Diagnosis of Orthopoxvirus infection in beef and dairy cattle during a study of the spread of vaccinia virus to cattle herds, Argentina, 2011* Of the 100 serum samples, 5 (3 from beef and 2 from dairy cattle) were positive for vgf by real-time PCR. HA DNA was amplified from 2 of the 3 vgf PCR–positive beef cattle samples; plaque-reduction neutralization test results were also positive for the 2 samples (Table). Alignment of the HA fragment nucleotide sequence of the isolates from Argentina showed that the sequence was highly similar to that of the homologous gene of VACV isolates from Brazil. Furthermore, the sequences showed a signature deletion that is also present in the sequences of VACV isolates from Brazil. Compared with sequences for other VACV isolates, those from Argentina had 2 polymorphisms (Technical Appendix, panel C). The HA sequences from the isolates from Argentina demonstrated 100% identity among themselves and exhibited higher identity with group 1 (98.2% identity) versus group 2 (93.6% identity) isolates from Brazil (Technical Appendix, panel D). In the phylogenetic tree based on the HA nucleotide sequences (Technical Appendix, panel B), the VACVs from Argentina clustered with several group 1 VACVs detected during outbreaks in Brazil. Although no outbreaks of exanthematous VACV infection have been described in cattle or humans in Argentina, we detected neutralizing antibodies against orthopoxvirus and detected VACV DNA in serum samples from cattle in the country. Most of the seropositive samples were from cattle in Entre Rios Province, which shares a border with Uruguay, and Corrientes Province, which shares a border with Rio Grande do Sul State in Brazil, where Pelotas VACVs have been isolated (2). We believe that the seropositive cattle in this study may have been exposed to VACV, the only orthopoxvirus known to be circulating in South America (1–4,8–10). Despite veterinary surveillance efforts of border control organizations, VACV control may be hampered by the circulation of infected rural workers and the misdiagnosis of VACV infection; misdiagnoses occur because VACV lesions resemble those of other exanthematous diseases. Moreover, peridomestic rodents have been hypothesized to act as VACV hosts, and could facilitate the spread of VACV in border areas (10). In addition, we could not rule out the circulation of autochthonous VACV in Argentina, but this is a less likely explanation. Our findings suggest that cattle herds in areas of Argentina near the border with Brazil may be exposed to VACV from Brazil and, thus, may be at risk for VACV infection. Further research is needed to determine the risk factors for VACV infection and to assess the circulation of VACV in South America Technical Appendix: Map of Argentina, indicating locations where blood samples were collected from cattle and results of phylogenetic analysis of vaccine virus isolated from the samples. Click here to view.(611K, pdf)

Group 1 Vaccinia virus Zoonotic Outbreak in Maranhão State, Brazil

In Brazil, several exanthematic autochthone Vaccinia virus (VACV) outbreaks affecting dairy cattle and rural workers have been reported since 1999. Although outbreaks had been first described in the Brazilian Southeast, VACV outbreaks were notified in all Brazilian regions in < 10 years. However, in this context, VACV outbreaks had not been described in some Brazilian States, likely because of a lack of notification, or yet unknown epidemiological reasons. Here, we describe the first VACV outbreak in Maranhão State, northeastern Brazil. The virus isolated from this outbreak showed several biological and molecular features that resemble other Group 1 Brazilian VACV, including a deletion signature in the A56R gene. This study raises new questions about diversity and epidemiology of Brazilian VACV.

Increased expression of 2′5′oligoadenylate synthetase and double-stranded RNA dependent protein kinase messenger RNAs on affected skin of systemic sclerosis patients

Scleroderma or systemic sclerosis (SSc) is an autoimmune disorder of unknown aetiology characterized by excessive collagen synthesis and subsequent deposition on the skin and various internal organs. Interferons (IFNs) are well-known immunomodulators and inhibitors of collagen production. However, IFN therapy has been implicated in the development or exacerbation of several autoimmune diseases, including SSc. We analyzed the expression of several interferon-stimulated genes (ISGs) in affected skin of SSc patients (skin tissue and cultured skin fibroblasts). A set of ISGs (PKR, 2′5′OAS, M×A, and 6–16) was analyzed by real-time PCR using RNA extracted from cultured skin fibroblasts and skin tissue of normal individuals and SSc patients. Both normal and SSc affected skin cultured fibroblasts were sensitive to the IFN treatment and presented similar levels of all ISGs tested. However, PKR and 2′5′OAS mRNA expression levels were significantly higher in the affected skin tissue of SSc patients when compared to normal controls. These data suggest that the IFN system plays a role in the pathogenesis of SSc.

Detection of Vaccinia Virus in Dairy Cattle Serum Samples from 2009, Uruguay.

We detected orthopoxvirus in 28 of 125 serum samples collected during 2009 from cattle in Uruguay. Two samples were PCR-positive for vaccinia virus and had sequences similar to those for vaccinia virus associated with outbreaks in Brazil. Autochthonous circulation of vaccinia virus in Uruguay and other South American countries cannot be ruled out.

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.

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.