Protective effect of surfactant protein d in pulmonary vaccinia virus infection: implication of A27 viral protein

Vaccinia virus (VACV) was used as a surrogate of variola virus (VARV) (genus Orthopoxvirus), the causative agent of smallpox, to study Orthopoxvirus infection. VARV is principally transmitted between humans by aerosol droplets. Once inhaled, VARV first infects the respiratory tract where it could encounter surfactant components, such as soluble pattern recognition receptors. Surfactant protein D (SP-D), constitutively present in the lining fluids of the respiratory tract, plays important roles in innate host defense against virus infection. We investigated the role of SP-D in VACV infection and studied the A27 viral protein involvement in the interaction with SP-D. Interaction between SP-D and VACV caused viral inhibition in a lung cell model. Interaction of SP-D with VACV was mediated by the A27 viral protein. Binding required Ca2+ and interactions were blocked in the presence of excess of SP-D saccharide ligands. A27, which lacks glycosylation, directly interacted with SP-D. The interaction between SP-D and the viral particle was also observed using electron microscopy. Infection of mice lacking SP-D (SP-D-/-) resulted in increased mortality compared to SP-D+/+ mice. Altogether, our data show that SP-D participates in host defense against the vaccinia virus infection and that the interaction occurs with the viral surface protein A27.

A small molecule screen in yeast identifies inhibitors targeting protein-protein interactions within the vaccinia virus replication complex

Genetic and biochemical data have identified at least four viral proteins essential for vaccinia virus (VACV) DNA synthesis: the DNA polymerase E9, its processivity factor (the heterodimer A20/D4) and the primase/helicase D5. These proteins are part of the VACV replication complex in which A20 is a central subunit interacting with E9, D4 and D5. We hypothesised that molecules able to modulate protein-protein interactions within the replication complex may represent a new class of compounds with anti-orthopoxvirus activities. In this study, we adapted a forward duplex yeast two-hybrid assay to screen more than 27,000 molecules in order to identify inhibitors of A20/D4 and/or A20/D5 interactions. We identified two molecules that specifically inhibited both interactions in yeast. Interestingly, we observed that these compounds displayed a similar antiviral activity to cidofovir (CDV) against VACV in cell culture. We further showed that these molecules were able to inhibit the replication of another orthopoxvirus (i.e. cowpox virus), but not the herpes simplex virus type 1 (HSV-1), an unrelated DNA virus. We also demonstrated that the antiviral activity of both compounds correlated with an inhibition of VACV DNA synthesis. Hence, these molecules may represent a starting point for the development of new anti-orthopoxvirus drugs.

Necrotic ulcerated lesion in a young boy caused by cowpox virus infection

The case presented here points towards the fact that skin lesion observed with a cowpox virus is a rare event but should be considered more as the number of cases has increased in the last years. Cowpox virus (CPXV) belongs to the Poxviridae family. The transmission of CPXV to humans is caused by wild rodents or mostly by domestic animals and pet rats. In humans, CPXV is responsible for localized skin lesions regularly accompanied by lymphadenopathy. The lesions remain localized but self-inoculation from the primary lesions could occur. Then physicians have to be vigilant concerning bandages. In this case report, a necrotic and ulcerated lesion of a CPXV infection in a young boy is reported. The CPXV was possibly transmitted by wild rodents. The importance of performing the diagnosis is also pointed out. Virus information was obtained from phylogenetic analyses showing that the CPXV isolate was distinct from outbreaks of human cowpox which occurred in 2009 in France and Germany but was close to the CPXV Brighton Red strain. For several years, cases of viral zoonosis caused by CPXV have increased and physicians should be made aware that people could be infected without history of direct contact with animals.

Severe ear chondritis due to cowpox virus transmitted by a pet rat

We describe a case of cowpox virus infection leading to severe acute inflammation and chondritis of the outer ear, complicated by local necrosis and facial cellulitis. Secondary lesions occurred on a finger and the abdomen. Apart from scarring, outcome was favorable after repeated surgical excision of necrotic tissue.

Inhibition of Hazara nairovirus replication by small interfering RNAs and their combination with ribavirin

Background

The genus Nairovirus in the family Bunyaviridae contains 34 tick-borne viruses classified into seven serogroups. Hazara virus (HAZV) belongs to the Crimean-Congo hemorrhagic fever (CCHF) serogroup that also includes CCHF virus (CCHFV) a major pathogen for humans. HAZV is an interesting model to study CCHFV due to a close serological and phylogenetical relationship and a classification which allows handling in a BSL2 laboratory. Nairoviruses are characterized by a tripartite negative-sense single stranded RNA genome (named L, M and S segments) that encode the RNA polymerase, the Gn-Gc glycoproteins and the nucleoprotein (NP), respectively. Currently, there are neither vaccines nor effective therapies for the treatment of any bunyavirus infection in humans. In this study we report, for the first time, the use of RNA interference (RNAi) as an approach to inhibit nairovirus replication.

Results

Chemically synthesized siRNAs were designed to target the mRNA produced by the three genomic segments. We first demonstrated that the siRNAs targeting the NP mRNA displayed a stronger antiviral effect than those complementary to the L and M transcripts in A549 cells. We further characterized the two most efficient siRNAs showing, that the induced inhibition is specific and associated with a decrease in NP synthesis during HAZV infection. Furthermore, both siRNAs depicted an antiviral activity when used before and after HAZV infection. We next showed that HAZV was sensitive to ribavirin which is also known to inhibit CCHFV. Finally, we demonstrated the additive or synergistic antiviral effect of siRNAs used in combination with ribavirin.

Conclusions

Our study highlights the interest of using RNAi (alone or in combination with ribavirin) to treat nairovirus infection. This approach has to be considered for the development of future antiviral compounds targeting CCHFV, the most pathogenic nairovirus.

[Crimean-Congo hemorrhagic fever: basics for general practitioners]

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease described in more than 30 countries in Europe, Asia and Africa. The causative agent is the Crimean-Congo hemorrhagic fever virus (CCHFV) that is a member of the genus Nairovirus of the family Bunyaviridae. CCHFV that is characterized by a high genetic variability is transmitted to humans by tick bites or contact with fluids from an infected individual or animal. The initial symptoms of CCHF are nonspecific and gradually progress to a hemorrhagic phase that can be lethal (case-fatality rate: 10 to 50%). Characteristic laboratory findings of CCHF are thrombocytopenia, elevated liver and muscle enzymes, and coagulation defects. The pathogenesis of CCHF remains unclear but might involve excessive pro-inflammatory cytokine production and dysfunction of the innate immune response. Diagnosis of CCHF is based mainly on isolation of the virus, identification of the viral genome by molecular techniques (RT-PCR), and serological detection of anti-CCHFV antibodies. There is currently no specific treatment for CCHFV infection and the efficacy of ribavirin is controversial. In absence of an effective vaccine, prevention is based mainly on vector control, protection measures, and information to increase the awareness of the population and of healthcare workers.

Lung surfactant DPPG phospholipid inhibits vaccinia virus infection

Vaccinia virus (VACV) was used as a surrogate of Variola virus (genus Orthopoxvirus), the causative agent of smallpox, to study orthopoxvirus infection via the respiratory airway. Lung surfactant, a physiological barrier to infection encountered by the virus, is predominantly composed of phospholipids whose role during orthopoxvirus infection has not been investigated. An attenuated Lister strain, derived from the traditional smallpox vaccine and the Western Reserve (WR) strain, lethal for mice infected by the respiratory route, were examined for their ability to bind various surfactant phospholipids. Dipalmitoyl phosphatidylglycerol (DPPG) was found to interact with both VACV strains. DPPG incorporated in small unilamellar vesicle (SUV-DPPG) inhibited VACV cell infection, unlike other phospholipids tested. Both pre-incubation of virus with SUV-DPPG and pretreatment of the cell with SUV-DPPG inhibited cell infection. This specific DPPG effect was shown to be concentration and time dependent and to prevent the first step of the viral cycle, i.e. virus cell attachment. Cryo-electron microscopy highlighted the interaction between the virus and SUV-DPPG. In the presence of the phospholipid, virus particles displayed a hedgehog-like appearance due to the attachment of lipid vesicles. Mice infected intranasally with VACV-WR pre-incubated with SUV-DPPG survived a lethal infection. These data suggest that DPPG in lung surfactant could reduce the amount of orthopoxvirus particles able to infect pneumocytes at the beginning of a respiratory poxvirus infection. The knowledge acquired during this study of virus-DPPG interactions may be used to develop novel chemotherapeutic strategies for smallpox.

Control of vaccinia virus skin lesions by long-term-maintained IFN-gamma+TNF-alpha+ effector/memory CD4+ lymphocytes in humans

Vaccinia virus (VV) vaccination is used to immunize against smallpox and historically was considered to have been successful if a skin lesion formed at the vaccination site. While antibody responses have been widely proposed as a correlate of efficacy and protection in humans, the role of cellular and humoral immunity in VV-associated skin lesion formation was unknown. We therefore investigated whether long-term residual humoral and cellular immune memory to VV, persisting 30 years after vaccination, could control VV-induced skin lesion in revaccinated individuals. Here, we have shown that residual VV-specific IFN-gamma+TNF-alpha+ or IFN-gamma+IL-2+ CD4+ lymphocytes but not CD8+ effector/memory lymphocytes expressing a skin-homing marker are inversely associated with the size of the skin lesion formed in response to revaccination. Indeed, high numbers of residual effector T cells were associated with lower VV skin lesion size after revaccination. In contrast, long-term residual VV-specific neutralizing antibody (NAbs) titers did not affect skin lesion formation. However, the size of the skin lesion strongly correlated with high levels of NAbs boosted after revaccination. These findings demonstrate a potential role for VV-specific CD4+ responses at the site of VV-associated skin lesion, thereby providing new insight into immune responses at these sites and potentially contributing to the development of new approaches to measure the efficacy of VV vaccination.

Differential activation profiles of Crimean-Congo hemorrhagic fever virus- and Dugbe virus-infected antigen-presenting cells

Crimean-Congo hemorrhagic fever virus (CCHFV) is a highly pathogenic, tick-borne member of the family Bunyaviridae and the genus Nairovirus. To better elucidate the pathogenesis of CCHFV, we analysed the host innate immune response induced in antigen-presenting cells (APCs) infected in vitro by CCHFV. Monocyte-derived dendritic cells (DCs) and macrophages (MPs) were both shown to be permissive for CCHFV and to replicate the virus, as monitored by genomic and antigenomic strand quantification. Virus replication was, however, controlled, corroborating an efficient alpha interferon-induced response. The upregulation of CD-83 and CD-86 indicated that CCHFV induced a partial maturation of DCs, which were also shown to activate the secretion of interleukin (IL)-6 and IL-8, but no tumour necrosis factor alpha (TNF-alpha). On the other hand, in MPs, CCHFV infection elicited a high IL-6 and TNF-alpha response and a moderate chemokine response. Nevertheless, when we compared these APC responses with those seen after infection with Dugbe virus (DUGV), a mildly pathogenic virus genetically close to CCHFV, we found that, in spite of some similarities, DUGV induced a higher cytokine/chemokine response in MPs. These results suggest that CCHFV is able to inhibit the activation of inflammatory mediators selectively in infection in vitro and that these differences could be relevant in pathogenesis.

Inhibition of Epstein–Barr virus replication by small interfering RNA targeting the Epstein–Barr virus protease gene

Background

The Epstein–Barr virus (EBV) protease (PR), coded by the BVRF2 gene, is essential for the maturation of the viral capsid and viral DNA packaging during the late stage of the EBV lytic cycle. Like the other herpesvirus serine PRs, EBV PR could be a target for the inhibition of EBV replication. To date, no data have been reported on the inhibition of EBV PR messenger RNA (mRNA) by small interfering RNA (siRNA).

Methods

In this study, siRNAs targeting EBV PR were delivered to the epithelial 293 cell line stably transfected with the complete B95-8 EBV episome. EBV DNA and PR mRNA were quantified by real-time PCR in cells and supernatant, protein expression was assessed by immunoblotting, and production of EBV infectious particles in the culture medium was measured by Raji cell superinfection.

Results

The EBV PR mRNA within the cells was reduced by 73%, the PR protein by 35% and the amount of virus in the cell supernatant was drastically decreased by 86% or 95%, depending on the method.

Conclusions

The strong effect of the siRNA targeting EBV PR on EBV replication attests to the crucial role played by EBV PR in the production of infectious particles and suggests that targeting this enzyme can be a new strategy against EBV-associated diseases where virus replication occurs.

Inhibition of Epstein-Barr virus replication by small interfering RNA targeting the Epstein-Barr virus protease gene

BACKGROUND

The Epstein-Barr virus (EBV) protease (PR), coded by the BVRF2 gene, is essential for the maturation of the viral capsid and viral DNA packaging during the late stage of the EBV lytic cycle. Like the other herpesvirus serine PRs, EBV PR could be a target for the inhibition of EBV replication. To date, no data have been reported on the inhibition of EBV PR messenger RNA (mRNA) by small interfering RNA (siRNA).

METHODS

In this study, siRNAs targeting EBV PR were delivered to the epithelial 293 cell line stably transfected with the complete B95-8 EBV episome. EBV DNA and PR mRNA were quantified by real-time PCR in cells and supernatant, protein expression was assessed by immunoblotting, and production of EBV infectious particles in the culture medium was measured by Raji cell superinfection.

RESULTS

The EBV PR mRNA within the cells was reduced by 73%, the PR protein by 35% and the amount of virus in the cell supernatant was drastically decreased by 86% or 95%, depending on the method.

CONCLUSIONS

The strong effect of the siRNA targeting EBV PR on EBV replication attests to the crucial role played by EBV PR in the production of infectious particles and suggests that targeting this enzyme can be a new strategy against EBV-associated diseases where virus replication occurs.

Demographic and clinical factors associated with response to smallpox vaccine in preimmunized volunteers

Context

In March 2003, the French Ministry of Health implemented a program on preparedness and response to a biological attack using smallpox as weapon. This program included the establishment of a preoutbreak national team that could be revaccinated against smallpox.

Objective

To identify demographic and clinical factors associated with vaccination success defined as the presence of a pustule at the inoculation site at day 8 (days 7–9), with an undiluted vaccinia virus derived from a Lister strain among preimmunized volunteers.

Volunteers and Methods

From March 2003 to November 2006, we have studied prospectively 226 eligible volunteers. Demographic data were recorded for each volunteer (age, sex, number of previously smallpox vaccinations and date of the last vaccination). Smallpox vaccine adverse reactions were diagnosed on the basis of clinical examination performed at days 0, 7, 14, 21 and 28 after revaccination.

Results

A total of 226 volunteers (sex ratio H/F = 2.7) were revaccinated. Median age was 45 years (range: 27–63 yrs). All volunteers completed follow-up. Median number of vaccinations before revaccination was 2 (range: 1–8). The median delay between time of the study and the last vaccination was 29 years (range; 18–60 yrs). Sixty-one volunteers (27%) experienced one (n = 40) or more (n = 21) minor side effects during the 2–14 days after revaccination. Successful vaccination was noted in 216/226 volunteers (95.6%) at day 8 and the median of the pustule diameter was 5 mm (range: 1–20 mm). Size of the pustule at day 8 was correlated with age (p = 0.03) and with the presence of axillary adenopathy after revaccination (p = 0.007). Sex, number of prior vaccinations, delay between the last vaccination and revaccination, and local or systemic side effects with the exception of axillary adenopathy, were not correlated with the size of the pustule at day 8.

Conclusions

Previously vaccinated volunteers can be successfully revaccinated with the Lister strain.

Specific Targeting of the F13L Protein by St-246 Affects Orthopoxvirus Production Differently

Background

ST-246 is a potent anti-orthopoxviral molecule targeting the F13L protein of vaccinia virus, which is involved in the wrapping of viruses. The discrepancy in sensitivities of several orthopoxviruses to ST-246 has raised questions about potential differences in their replicative cycles and/or the presence of another drug target.

Methods

Density gradients were used to evaluate the differences between the viral cycles of vaccinia, cow-pox and camelpox viruses. Also, to investigate if ST-246 inhibits a single target, we compared its activity to that of small interfering RNAs designed to silence the F13L gene (siF13Ls).

Results

We showed that the spread of vaccinia virus involved both intracellular and extracellular enveloped viruses, whereas both cowpox and camelpox viruses seemed to propagate via non-enveloped intracellular forms and cell-associated viral particles. Although ST-246 exerted a clear antiviral activity by interfering with the egress of the virus from infected cells, we observed that cowpox and camelpox viruses, in contrast to vaccinia virus, could be directed towards a lytic cycle under ST-246 treatment. We specifically knocked down the F13L transcripts of vaccinia and camelpox viruses by >85%, reduced virus progeny by 90% and showed that siF13Ls affect camelpox and vaccinia virus propagation differently. Flow cytometry data validated that ST-246 interfered with the activity of the F13L protein, whereas siF13Ls silenced the F13L gene.

Conclusions

Our observations support that vaccinia, cow-pox and camelpox viruses exhibit different levels of sensitivity to ST-246 because of dissimilarities between their ways of propagation, and provide a better understanding of the mode of action of ST-246.

Specific Inhibition of Orthopoxvirus Replication by a Small Interfering RNA Targeting the D5R Gene

Background

Concerns about the potential use of smallpox in bioterrorism have stimulated interest in the development of novel antiviral treatments. Currently, there are no effective therapies against smallpox and new treatment strategies are greatly needed.

Methods

In this study, specifically designed small interfering RNAs (siRNAs), targeting five proteins essential for orthopoxvirus replication, were investigated for their ability to inhibit vaccinia virus strain Western Reserve (VACVWR) replication.

Results

Among these siRNAs, 100 nM siD5R-2, an siRNA targeting the D5 protein, decreased VACVWR replication up to 90% when used either prophylactically or therapeutically in human lung carcinoma A549 cells. This siRNA induced a striking concentration-dependent inhibition of VACVWR replication and a prolonged prophylactic antiviral effect that lasted for 72 h, at a concentration of 100 nM. Confocal microscopy of Alexa–siD5R-2-treated VACVWR-infected cells confirmed a decrease in viral replication. Furthermore, siD5R-2 was shown to specifically reduce the D5R mRNA and protein expression using real-time reverse tran-scriptase-PCR and western blotting analysis, without inducing interferon-β in A549 cells. We also demonstrated the antiviral potency of siD5R-2 against different pathogenic orthopoxviruses, such as cowpox and monkeypox viruses, which were inhibited up to 70% at the lowest concentration (1 nM) tested. Finally, siD5R-2 showed antiviral effects in VACVWR-infected human keratinocyte and fibroblast cell cultures.

Conclusions

These results suggest that siD5R-2 could be a potential candidate to treat poxvirus infections.

Short- and long-term immunogenicity and protection induced by non-replicating smallpox vaccine candidates in mice and comparison with the traditional 1st generation vaccine

This study assessed three non-replicating smallpox vaccine candidates (modified vaccinia Ankara (MVA), NYVAC and HR) for their immunogenicity and ability to protect mice against an intranasal cowpox virus challenge and compared them with the traditional replicating vaccine. A single immunisation with the non-replicating vaccines induced a complete protection from death at short-term, but was not fully protective when mice were challenged 150 days post-vaccination with protection correlated with the specific neutralizing antibodies and CD4(+) T-cells responses. Prime-boost vaccination enabled effective long-term protection from death for mice vaccinated with MVA, but protection from disease and CD4(+) T-cell level were lower than the ones induced by the traditional vaccine over the long-term period. Further investigations are necessary with MVA to determine the optimal conditions of immunisation to induce at long-term immunogenicity and protection observed with the 1st generation smallpox vaccine.

Specific targeting of the F13L protein by ST-246 affects orthopoxvirus production differently

BACKGROUND

ST-246 is a potent anti-orthopoxviral molecule targeting the F13L protein of vaccinia virus, which is involved in the wrapping of viruses. The discrepancy in sensitivities of several orthopoxviruses to ST-246 has raised questions about potential differences in their replicative cycles and/or the presence of another drug target.

METHODS

Density gradients were used to evaluate the differences between the viral cycles of vaccinia, cowpox and camelpox viruses. Also, to investigate if ST-246 inhibits a single target, we compared its activity to that of small interfering RNAs designed to silence the F13L gene (siF13Ls).

RESULTS

We showed that the spread of vaccinia virus involved both intracellular and extracellular enveloped viruses, whereas both cowpox and camelpox viruses seemed to propagate via non-enveloped intracellular forms and cell-associated viral particles. Although ST-246 exerted a clear antiviral activity by interfering with the egress of the virus from infected cells, we observed that cowpox and camelpox viruses, in contrast to vaccinia virus, could be directed towards a lytic cycle under ST-246 treatment. We specifically knocked down the F13L transcripts of vaccinia and camelpox viruses by > 85%, reduced virus progeny by 90% and showed that siF13Ls affect camelpox and vaccinia virus propagation differently. Flow cytometry data validated that ST-246 interfered with the activity of the F13L protein, whereas siF13Ls silenced the F13L gene.

CONCLUSIONS

Our observations support that vaccinia, cowpox and camelpox viruses exhibit different levels of sensitivity to ST-246 because of dissimilarities between their ways of propagation, and provide a better understanding of the mode of action of ST-246.

Specific inhibition of orthopoxvirus replication by a small interfering RNA targeting the D5R gene

BACKGROUND

Concerns about the potential use of smallpox in bioterrorism have stimulated interest in the development of novel antiviral treatments. Currently, there are no effective therapies against smallpox and new treatment strategies are greatly needed.

METHODS

In this study, specifically designed small interfering RNAs (siRNAs), targeting five proteins essential for orthopoxvirus replication, were investigated for their ability to inhibit vaccinia virus strain Western Reserve (VACVWR) replication.

RESULTS

Among these siRNAs, 100 nM siD5R-2, an siRNA targeting the D5 protein, decreased VACVWR replication up to 90% when used either prophylactically or therapeutically in human lung carcinoma A549 cells. This siRNA induced a striking concentration-dependent inhibition of VACVWR replication and a prolonged prophylactic antiviral effect that lasted for 72 h, at a concentration of 100 nM. Confocal microscopy of Alexa-siD5R-2-treated VACVWR-infected cells confirmed a decrease in viral replication. Furthermore, siD5R-2 was shown to specifically reduce the D5R mRNA and protein expression using real-time reverse transcriptase-PCR and western blotting analysis, without inducing interferon-13 in A549 cells. We also demonstrated the antiviral potency of siD5R-2 against different pathogenic orthopoxviruses, such as cowpox and monkeypox viruses, which were inhibited up to 70% at the lowest concentration (1 nM) tested. Finally, siD5R-2 showed antiviral effects in VACVWR-infected human keratinocyte and fibroblast cell cultures.

CONCLUSIONS

These results suggest that siD5R-2 could be a potential candidate to treat poxvirus infections.

Activity of the Anti-Orthopoxvirus Compound ST-246 against Vaccinia, Cowpox and Camelpox Viruses in Cell Monolayers and Organotypic Raft Cultures

Background

The potential use of variola virus as a biological weapon has renewed efforts in the development of antiviral agents against orthopoxviruses. ST-246 [4-trifluoromethyl-W-(3,3a,4,4a,5,5a,6,6a-octahydro-1,3-dioxo-4,6-ethenocycloprop [f]isoindol-2(1H)-yl)-benza-mide] is an anti-orthopoxvirus compound active against several orthopoxviruses including vaccinia virus (VV), cowpox virus (CPV), camelpox virus (CMLV), ectromelia virus (ECTV) and variola virus in cell culture. The compound has been shown to inhibit the release of extracellular virus by targeting the F13L VV protein and to protect mice from VV, CPV and ECTV orthopoxvirus-induced disease.

Methods

The antiviral activity of ST-246 was assessed against extracellular and intracellular VV, CPV and CMLV production in human embryonic lung (HEL) fibroblasts and primary human keratinocyte (PHK) cell monolayers, as well as in three-dimensional raft cultures.

Results

ST-246 inhibited preferentially the production of extracellular virus compared with intracellular virus production in HEL and PHK cells (for VV) and in PHK cells (for CMLV). In organotypic epithelial raft cultures, ST-246 at 20 μg/ml inhibited extracellular VV and CMLV production by 6 logs, whereas intracellular virus yield was reduced by 2 logs. In the case of CPV, both extracellular and intracellular virus production were completely inhibited by ST-246 at 20 μg/ml. Histological sections of the infected rafts, treated with increasing amounts of drug, confirmed the antiviral activity of ST-246: the epithelium was protected and there was no evidence of viral infection. Electron microscopic examination confirmed the absence of intracellular enveloped virus forms in VV-, CPV- and CMLV-infected cells treated with 10 μg/ml of ST-246.

Conclusions

These data indicate that ST-246 is a potent anti-orthopoxvirus compound; the mode of inhibition is dependent on the virus and cell type.

Substrate specificity of homogeneous monkeypox virus uracil-DNA glycosylase

Weak or nonexistent smallpox immunity in today's human population raises concerns about the possibility of natural or provoked genetic modifications leading to re-emergence of variola virus and other poxviruses. Thus, the development of new antiviral strategies aimed at poxvirus infections in humans is a high priority. The DNA repair protein uracil-DNA glycosylase (UNG) is one of the viral enzymes important for poxvirus pathogenesis. Consequently, the inhibition of UNG is a rational therapeutic strategy for infections with poxviruses. Monkeypox virus, which occurs naturally in Africa, can cause a smallpox-like disease in humans. Here, the monkeypox virus UNG (mpUNG) is characterized and compared to vaccinia virus UNG (vUNG) and human UNG (hUNG). The mpUNG protein excises uracil preferentially from single-stranded DNA. Furthermore, mpUNG prefers the U.G pair over the U.A pair and does not excise oxidized bases. Both mpUNG and vUNG viral proteins are strongly inhibited by physiological concentrations of NaCl and MgCl2. Although the two viral DNA repair enzymes have similar substrate specificities, the kcat/KM values of mpUNG are higher than those of vUNG. The mpUNG protein was strongly inhibited by 5-azauracil and to a lesser extent by 4(6)-aminouracil and 5-halogenated uracil analogues, whereas uracil had no effect. To develop antiviral drugs toward mpUNG, we also validated a repair assay using the molecular beacons containing multiple uracil residues. Potential targets and strategies for combating pathogenic orthopoxviruses, including smallpox, are discussed.

Activities of several classes of acyclic nucleoside phosphonates against camelpox virus replication in different cell culture models

Camelpox virus (CMLV) is the closest known virus to variola virus. Here we report on the anti-CMLV activities of several acyclic nucleoside phosphonates (ANPs) related to cidofovir [(S)-1-(3-hydroxy-2-phosphonomethoxypropyl)cytosine (HPMPC; Vistide)] against two CMLV strains, CML1 and CML14. Cytopathic effect (CPE) reduction assays performed with human embryonic lung fibroblast monolayers revealed the selectivities of the first two classes of ANPs (cHPMPA, HPMPDAP, and HPMPO-DAPy) and of the hexadecyloxyethyl ester of 1-{[(5S)-2-hydroxy-2-oxido-1,4,2-dioxaphosphinan-5-yl]methyl}-5-azacytosine (HDE-cHPMP-5-azaC), belonging to the newly synthesized ANPs, which are HPMP derivatives containing a 5-azacytosine moiety. The inhibitory activities of ANPs against both strains were also confirmed with primary human keratinocyte (PHK) monolayers, despite the higher toxicity of those molecules on growing PHKs. Virus yield assays confirmed the anti-CML1 and anti-CML14 efficacies of the compounds selected for the highest potencies in CPE reduction experiments. Ex vivo studies were performed with a 3-dimensional model of human skin, i.e., organotypic epithelial raft cultures of PHKs. It was ascertained by histological evaluation, as well as by virus yield assays, that CMLV replicated in the human skin equivalent. HPMPC and the newly synthesized ANPs proved to be effective at protecting the epithelial cells against CMLV-induced CPE. Moreover, in contrast to the toxicity on PHK monolayers, signs of toxicity in the differentiated epithelium were seen only at high ANP concentrations. Our results demonstrate that compounds belonging to the newly synthesized ANPs, in addition to cidofovir, represent promising candidates for the treatment of poxvirus infections.

Genomic sequence of a clonal isolate of the vaccinia virus Lister strain employed for smallpox vaccination in France and its comparison to other orthopoxviruses

Since 1980 there has been global eradication of smallpox due to the success of the vaccination programme using vaccinia virus (VACV). During the eradication period, distinct VACV strains circulated, the Lister strain being the most commonly employed in Europe. Analysis of the safety of smallpox vaccines has suggested that they display significant heterogeneity. To gain a more detailed understanding of the diversity of VACV strains it is important to determine their genomic sequences. Although the sequences of three isolates of the Japanese Lister original strain (VACV-LO) are available, no analysis of the relationship of any Lister sequence compared to other VACV genomes has been reported. Here, we describe the sequence of a representative clonal isolate of the Lister vaccine (VACV-List) used to inoculate the French population. The coding capacity of VACV-List was compared to other VACV strains. The 201 open reading frames (ORFs) were annotated in the VACV-List genome based on protein size, genomic localization and prior characterization of many ORFs. Eleven ORFs were recognized as pseudogenes as they were truncated or fragmented counterparts of larger ORFs in other orthopoxviruses (OPVs). The VACV-List genome also contains several ORFs that have not been annotated in other VACVs but were found in other OPVs. VACV-List and VACV-LO displayed a high level of nucleotide sequence similarity. Compared to the Copenhagen strain of VACV, the VACV-List sequence diverged in three main regions, one of them corresponding to a substitution in VACV-List with coxpox virus GRI-90 strain ORFs, suggestive of prior genetic exchanges. These studies highlight the heterogeneity between VACV strains and provide a basis to better understand differences in safety and efficacy of smallpox vaccines.

Intranasal cowpox virus infection of the mouse as a model for preclinical evaluation of smallpox vaccines

The intranasal infection of mice with cowpox virus (CPXV) has been evaluated as a model for smallpox infection in man. Administration of a lethal dose of CPXV allowed time for development of T-cell responses but antibodies could not be detected before death occurred. In contrast, infection with a sublethal dose was associated with an early T-cell response followed by neutralising antibodies which correlated with virus clearance. Comparison of two first generation smallpox vaccines revealed no significant differences in terms of immunogenicity, protection and post-challenge virus clearance. These studies show that the CPXV/mouse model is valuable for the initial assessment of smallpox vaccines.

Real-time PCR to identify variola virus or other human pathogenic orthopox viruses

BACKGROUND

Variola virus (family Poxviridae, genus Orthopoxvirus) and the closely related cowpox, vaccinia, and monkeypox viruses can infect humans. Efforts are mounting to replenish the smallpox vaccine stocks, optimize diagnostic methods for poxviruses, and develop new antivirals against smallpox, because it is feared that variola virus might be used as a weapon of bioterrorism.

METHODS

We developed an assay for the detection of variola virus DNA. The assay is based on TaqMan chemistry targeting the 14-kD protein gene. For the 1st stage of the assay we used genus consensus primers and a mixture of 2 probes (14-kD POX and 14-kD VAR) spanning the 14-kD protein-encoding gene for detection of all human pathogenic orthopoxviruses. We then tested positive samples with the specific orthopoxvirus-specific probe 14-kD POX to identify monkeypox, cowpox, and vaccinia viruses and with the 14-kD VAR probe to identify variola viruses. The assay was established on 4 different PCR cycler platforms. It was assessed in a study with 85 different orthopoxvirus species and strains that included variola, camelpox, cowpox, monkeypox, and vaccinia viruses at concentrations ranging from 100 ng/L to 1 microg/L.

RESULTS

The assay detected as little as 0.05 fg of DNA, corresponding to 25 copies of DNA, and enabled differentiation of variola virus from the other orthopoxviruses.

CONCLUSIONS

This real-time PCR assay provides a rapid method for the early detection and differentiation of smallpox and other human pathogenic orthopoxvirus infections.

Activity of the anti-orthopoxvirus compound ST-246 against vaccinia, cowpox and camelpox viruses in cell monolayers and organotypic raft cultures

BACKGROUND

The potential use of variola virus as a biological weapon has renewed efforts in the development of antiviral agents against orthopoxviruses. ST-246 [4-trifluoromethyl-N-(3,3a,4,4a,5,5a,6,6a-octahydro-1,3-di oxo-4,6-ethenocycloprop [f]isoindol-2(1 H)-yl)-benzamide] is an anti-orthopoxvirus compound active against several orthopoxviruses including vaccinia virus (VV), cowpox virus (CPV), camelpox virus (CMLV), ectromelia virus (ECTV) and variola virus in cell culture. The compound has been shown to inhibit the release of extracellular virus by targeting the F13L W protein and to protect mice from W, CPV and ECTV orthopoxvirus-induced disease.

METHODS

The antiviral activity of ST-246 was assessed against extracellular and intracellular W, CPV and CMLV production in human embryonic lung (HEL) fibroblasts and primary human keratinocyte (PHK) cell monolayers, as well as in three-dimensional raft cultures.

RESULTS

ST-246 inhibited preferentially the production of extracellular virus compared with intracellular virus production in HEL and PHK cells (for W) and in PHK cells (for CMLV). In organotypic epithelial raft cultures, ST-246 at 20 microg/ml inhibited extracellular W and CMLV production by 6 logs, whereas intracellular virus yield was reduced by 2 logs. In the case of CPV, both extracellular and intracellular virus production were completely inhibited by ST-246 at 20 microg/ml. Histological sections of the infected rafts, treated with increasing amounts of drug, confirmed the antiviral activity of ST-246: the epithelium was protected and there was no evidence of viral infection. Electron microscopic examination confirmed the absence of intracellular enveloped virus forms in W-, CPV- and CMLV-infected cells treated with 10 microg/ml of ST-246.

CONCLUSIONS

These data indicate that ST-246 is a potent anti-orthopoxvirus compound; the mode of inhibition is dependent on the virus and cell type.

Viral suppressors of RNA interference impair RNA silencing induced by a Semliki Forest virus replicon in tick cells

It was recently shown that infection of ISE6 tick cells by a recombinant Semliki Forest virus (SFV) expressing a heterologous gene induced small interfering RNAs (siRNAs) and silencing of the gene. To gain information on RNA interference (RNAi) in ticks, three known viral inhibitors that act in different ways, the NS1 protein of Influenza virus, NSs of Tospovirus Tomato spotted wilt virus and HC-Pro of Zucchini yellow mosaic virus were expressed and investigated to determine if they antagonize induced RNAi. Using the recombinant SFV replicon expressing firefly luciferase, silencing was induced and the suppressor activity of these inhibitors during or after initiation of siRNA synthesis was tested, to determine which step of the RNAi pathway is impaired. It was found that these proteins, identified in mammalian or plant systems, also display activity in tick cells. These data suggest that ticks utilize a mechanism similar to the one found in other eukaryotes.

Evaluation of a Crimean-Congo hemorrhagic fever virus recombinant antigen expressed by Semliki Forest suicide virus for IgM and IgG antibody detection in human and animal sera collected in Iran

Crimean-Congo hemorrhagic fever virus (CCHFV) is transmitted to humans by ticks or by direct contact with infected blood. It causes severe, often fatal, hemorrhagic diseases in humans but infection in animals is asymptomatic. CCHFV can spread from person to person and has caused many nosocomial outbreaks. Because the virus is very pathogenic for humans it must be manipulated in a biosafety level 4 (BSL4) laboratory, rendering the production of antigen for serological diagnosis difficult. To replace the native antigen, we produced a recombinant nucleoprotein expressed in mammalian cells via the recombinant Semliki Forest alphavirus replicon and developed an indirect immunofluorescence assay (IFA) as well as an enzyme-linked immunosorbent assay (ELISA) by immunocapture to detect IgM and IgG in human and animal serum. Using these methods, we analyzed clinical samples from human patients and sera from domestic animals collected in Iran and we show that this novel antigen provides a novel, sensitive and specific tool for CCHF diagnosis.

Establishment of a national network of validated and qualified laboratories for neutralizing anti-vaccinia antibodies titration

A Proficiency Testing Study (PTS) was organized in France by the French Health Products Safety Agency (Afssaps) aiming at assessing the performance of laboratories in performing a neutralizing anti-vaccinia antibodies titration method by plaque reduction neutralization test (PRNT). The ultimate goal was to establish a national network of qualified and validated laboratories. Five laboratories were included in the PTS and four submitted their data. Three samples of human sera containing various immunoglobulin concentrations (a "high" serum: s-576, a "medium" serum: Ref-19584 and a "low" serum: s-483) were tested by PRNT as described in a procedure supplied by Afssaps and developed in each laboratory during preliminary assays. Data were sent to Afssaps which performed the statistical analysis. The overall performance of the four participating laboratories was satisfactory. This allowed the four participating laboratories to be validated and then to be qualified by the Ministry of Health. Finally a national network for anti-vaccinia immunoglobulins titration was established.

Nairovirus RNA sequences expressed by a Semliki Forest virus replicon induce RNA interference in tick cells

We report the successful infection of the cell line ISE6 derived from Ixodes scapularis tick embryos by the tick-borne Hazara virus (HAZV), a nairovirus in the family Bunyaviridae. Using a recombinant Semliki Forest alphavirus replicon that replicates in these cells, we were able to inhibit replication of HAZV, and we showed that this blockage is mediated by the replication of the Semliki Forest alphavirus replicon; the vector containing the HAZV nucleoprotein gene in sense or antisense orientation efficiently inhibited HAZV replication. Moreover, expression of a distantly related nucleoprotein gene from Crimean-Congo hemorrhagic fever nairovirus failed to induce HAZV silencing, indicating that the inhibition is sequence specific. The resistance of these cells to replicate HAZV correlated with the detection of specific RNase activity and 21- to 24-nucleotide-long small interfering RNAs. Altogether, these results strongly suggest that pathogen-derived resistance can be established in the tick cells via a mechanism of RNA interference.

Standardization of a neutralizing anti-vaccinia antibodies titration method: an essential step for titration of vaccinia immunoglobulins and smallpox vaccines evaluation

The possibility of mass population vaccination with smallpox vaccine implies the development of anti-vaccinia immunoglobulins for the treatment of severe side effects following vaccination. We have chosen to develop and validate the "gold standard method" (plaque reduction neutralization assay) to titrate neutralizing anti-vaccinia antibodies in two different French laboratories belonging to the Department of Defense (CRSSA) and to the French Health Products Safety Agency (Afssaps). The results of precision, linearity and accuracy of the method led to consider the method as validated. In parallel, we have prepared and lyophilized a pool of anti-vaccinia plasma samples issued from a unique donor and qualified this preparation versus the first British standard to use it as an in-house standard with a titer of 25 international units (IU). This work will allow to titrate, in IU, sera from vaccinated persons in order (i) to titrate purified anti-vaccinia immunoglobulin preparations for vaccine severe side effect treatments; (ii) to investigate the level of neutralizing antibodies in the general population; and (iii) to investigate clinical trials of new generation smallpox vaccines. In the future, this will allow comparability of studies on either smallpox vaccines or on the serological status of the population.

[Update on smallpox vaccines]

Smallpox is among the most dangerous pathogens that could be used by bioterrorists. The former vaccines produced by scarification on the flanks of calves or sheep could be used to protect the whole French population when used with bifurcated needles. They should be replaced by a second-generation vaccine grown in cell culture and, eventually later by new and safer third-generation vaccines using non-replicative viral strains.

Rapid inactivation of vaccinia virus in suspension and dried on surfaces

A bioterrorist attack with smallpox virus would be disastrous with a 30% disease fatality rate. Such an outbreak would require biomedical laboratories for diagnosis and analyses and extensive use of clinical care facilities for patient quarantine. Safe decontamination procedures will have to be in place in order to limit the spread of the disease. In order to fulfil this need, Sanytex, a new non-corrosive commercial solution containing quaternary ammonium, aldehydes, alcohol and detergent, was tested with a view to using it in decontamination procedures. Vaccinia virus was used in this investigation as a model for smallpox virus. We determined exposure time and the concentration of Sanytex required to inactivate the virus in suspension and dried on surfaces in the presence of protein (up to 70 mg/mL). After 3 min incubation, Sanytex at a concentration of 3% led to a complete inactivation (virus titre reduction >10(4)-fold of vaccinia virus in suspension containing protein up to 30 mg/mL. A virus suspension containing 70 mg protein/mL, simulating biological fluids, was decontaminated with 10% Sanytex after 3 min. After 10 min, Sanytex at a concentration of 30%, applied on to a dried vaccinia virus contaminated surface in the presence of protein (10 mg/mL before desiccation), led to complete decontamination of the surface. Thirty minutes exposure with 30% Sanytex was necessary for a virus titre reduction of >10(4)-fold on a surface contaminated with a dried suspension of vaccinia virus in the presence of protein at 70 mg/mL. Sanytex is not corrosive, not toxic to environment and stable for up to three months even diluted. Its virucidal effect was preserved when used under pressure in a fire-hose nozzle. These results support the use of Sanytex for decontamination of biological fluids and surfaces contaminated by the smallpox virus.

In vitro inhibition of Chikungunya and Semliki Forest viruses replication by antiviral compounds: synergistic effect of interferon-alpha and ribavirin combination

Chikungunya virus (CHIKV) and Semliki Forest virus (SFV) were used in our laboratory to screen active antiviral compounds against viruses of the Alphavirus genus. Antiviral activity was estimated by the reduction of the cytopathic effect of each alphavirus on infected Vero cells and by virus titer reduction. Cytotoxicity was evaluated by determining the inhibition of Trypan blue exclusion in confluent cell cultures and by the evaluation of the inhibitory effect on cell growth. With CHIKV and SFV, the selectivity indices of human recombinant interferon-alpha and iota-carrageenan were much higher than that of ribavirin, which has been previously investigated for its inhibitory effect on alphavirus infections. Compared to ribavirin, 6-azauridine was more effective against CHIKV and showed a similar antiviral activity against SFV. IFN-alpha2b, glycyrrhizin, 6-azauridine, and ribavirin caused a concentration-dependent reduction in the virus yield with CHIKV and SFV. Moreover, the combination of IFN-alpha2b and ribavirin had a subsynergistic antiviral effect on these two alphaviruses and should be evaluated for the treatment of these infections.

Polystyrene derivatives substituted with arginine interact with Babanki (Togaviridae) and Kedougou (Flaviviridae) viruses

Outbreaks of new or old diseases appear primarily in tropical zones such as Africa, south and central America, or Asia. Among these diseases, those induced by Arboviruses (the best known of which are being yellow fever, dengue, Ebola, and Sindbis) are under intensive observation by the World Health Organization. Rapid isolation and identification of the viral species is the first step in the diagnosis, study, and control of epidemics. One major problem with the isolation of viruses is capturing sufficient numbers of viral particles to test. The work presented in this report addresses this question. We have tested the interaction between Babanki (Togaviridae), Kedougou (Flaviviridae) viruses, and a range of insoluble polystyrene derivatives substituted with arginine groups. Insoluble functionalized copolymers were found to develop specific interactions with viruses through chemical groups present on their surfaces. The adsorption of viruses varied according to the percentage of arginine substituted onto the polymer, with a maximum value for both viruses of about 20% of grafting rate. It was also found that the Kedougou virus displayed the highest affinity for this polymer.

Cellular glycosaminoglycans and low density lipoprotein receptor are involved in hepatitis C virus adsorption

The initial binding of Hepatitis C virus (HCV) to the cell membrane is a critical determinant of pathogenesis. Two putative HCV receptors have been identified, CD81 and low-density lipoprotein receptor (LDLr). CD81 interacts in vitro with the HCV E2 envelope glycoprotein, and LDLr interacts with HCV present in human plasma. In order to characterize these potential receptors for HCV, virus from plasma, able to replicate in cell culture, was inoculated on Vero cells or human hepatocarcinoma cells. HCV adsorption was assessed by quantitating cell-associated viral RNA by a real-time RT-PCR method. Anti-LDLr antibody, low and very low density lipoproteins inhibited significantly HCV adsorption, confirming the role of LDLr as HCV receptor. Only one out of the two anti-CD81 antibodies used in this study led to a partial inhibition of HCV binding. This study also highlights a role for glycosaminoglycans (GAGs) in HCV adsorption: treatment of virus with heparin led to 70% inhibition of attachment, as did desulfation of cellular GAGs. Treatment of Vero cells with heparin-lyase significantly inhibited virus attachment but by only 30%. These results demonstrate the complexity of the HCV binding step in which LDLr interacts strongly with HCV, whereas the interaction of HCV with GAGs and particularly with CD81 seem to be more moderate.

NS3 protease of Langat tick-borne flavivirus cleaves serine protease substrates

Langat (LGT) virus, initially isolated in 1956 from ticks in Malaysia, is a naturally occurring nonpathogenic virus with a very close antigenicity to the highly pathogenic tick-borne encephalitis (TBE) Western subtype virus and TBE Far Eastern subtype virus. NS3, the second largest viral protein of LGT virus, is highly conserved among flaviviruses and contains a characteristic protease moiety (NS3 pro). NS3 pro represents an attractive target for anti-protease molecules against TBE virus. We report herein a purification method specially designed for NS3 pro of LGT using a strategy for proper refolding coupled with the enzymatic characterisation of the protein. Different p-nitroanilide substrates, defined on canonic sequences for their susceptibility to Ser-protease, were applied to the proteolytic assays of the protein. The highest values were obtained from substrates containing an Arg or Lys (amino acid) residue at the P1 position. This purification method will facilitate the future development of reliable testing procedures for anti-proteases directed to NS3 proteins.

Heparan sulfate-mediated binding of infectious dengue virus type 2 and yellow fever virus

Dengue virus type 2 and Yellow fever virus are arthropod-borne flaviviruses causing hemorrhagic fever in humans. Identification of virus receptors is important in understanding flavivirus pathogenesis. The aim of this work was to study the role of cellular heparan sulfate in the adsorption of infectious Yellow fever and Dengue type 2 viruses. Virus attachment was assessed by adsorbing virus to cells, washing unbound virus away, releasing cell-bound virus by freezing/thawing, and then titrating the released infectious virus. Treatment of cells by heparin-lyase, desulfation of cellular heparan sulfate, or treatment of the virus with heparin inhibited cell binding of both viruses. Heparin also inhibited Yellow fever virus infection by 97%. Using infectious virus, the present work shows the importance of heparan sulfate in binding and infection of these two flaviviruses.

Quantitative real-time PCR detection of Rift Valley fever virus and its application to evaluation of antiviral compounds

The Rift Valley fever virus (RVFV), a member of the genus Phlebovirus (family Bunyaviridae) is an enveloped negative-strand RNA virus with a tripartite genome. Until 2000, RVFV circulation was limited to the African continent, but the recent deadly outbreak in the Arabian Peninsula dramatically illustrated the need for rapid diagnostic methods, effective treatments, and prophylaxis. A method for quantifying the small RNA segment by a real-time detection reverse transcription (RT)-PCR using TaqMan technology and targeting the nonstructural protein-coding region was developed, and primers and a probe were designed. After optimization of the amplification reaction and establishment of a calibration curve with synthetic RNA transcribed in vitro from a plasmid containing the gene of interest, real-time RT-PCR was assessed with samples consisting of RVFV from infected Vero cells. The method was found to be specific for RVFV, and it was successfully applied to the detection of the RVFV genome in animal sera infected with RVFV as well as to the assessment of the efficiency of various drugs (ribavirin, alpha interferon, 6-azauridine, and glycyrrhizin) for antiviral activity. Altogether, the results indicated a strong correlation between the infectious virus titer and the amount of viral genome assayed by real time RT-PCR. This novel method could be of great interest for the rapid diagnosis and screening of new antiviral compounds, as it is sensitive and time saving and does not require manipulation of infectious material.

Highly sensitive Taqman PCR detection of Puumala hantavirus

An increasing number of clinical cases of Hantavirus infections have been reported from various regions in Asia, Europe and North America. Hantaviruses (family Bunyaviridae, genus Hantavirus) are enveloped and possess a single-stranded trisegmented RNA genome of negative polarity. Rodents or insectivores are natural hosts of hantaviruses and transmit the virus to humans chiefly by aerosolisation. These viruses are the causative agents of haemorrhagic fever with renal and pulmonary syndromes. In the northeast of France, Puumala hantavirus causes, every year, more than 150 mild forms of haemorrhagic fever with a renal syndrome known as nephropathia epidemica. Serological tests may lack sensitivity for diagnosing early stages of infection and virus isolation is limited because it grows poorly in cell culture. Since reverse transcription (RT)-PCR amplification is an efficient method for detecting viral genomes in patient specimens, we developed an assay using a Taqman probe and compared it with the classical RT-PCR amplification. To achieve this goal, a Puumala strain was grown in Vero E6 cells and RNA extracted from the culture supernatant. We found that the semi-nested RT-PCR detected a minimal amount of 300 TCID(50) mL(-1), while the Taqman PCR allowed detection of less than 10 TCID(50) mL(-1 )and provided a quantitative analysis.

[Hepatitis C virus culture systems]

Hepatitis C virus pathogenesis and cycle are difficult to study because of the lack of culture system able to replicate efficiently the virus. Furthermore such a system will permit screen new antiviral drugs. Studies were realized to select cell culture system able to allow hepatitis C virus replication. Primary cell cultures and cell lines were used to performed HCV culture. Most of these works used lymphocyte and hepatocyte primary cultures or cell lines because of HCV tropism in these cells in vivo. Animals and arthropods cell lines were used as well for their capacity to bind and replicate HCV. The aim of this review is to present the different cell systems used to replicate HCV in culture and the results obtained.

Comparison of flavivirus universal primer pairs and development of a rapid, highly sensitive heminested reverse transcription-PCR assay for detection of flaviviruses targeted to a conserved region of the NS5 gene sequences

Arthropod-transmitted flaviviruses are responsible for considerable morbidity and mortality, causing severe encephalitic, hemorrhagic, and febrile illnesses in humans. Because there are no specific clinical symptoms for infection by a determined virus and because different arboviruses could be present in the same area, a genus diagnosis by PCR would be a useful first-line diagnostic method. The six published Flavivirus genus primer pairs localized in the NS1, NS3, NS5, and 3' NC regions were evaluated in terms of specificity and sensitivity with flaviviruses (including the main viruses pathogenic for humans) at a titer of 10(5) 50% tissue culture infectious doses (TCID(50)s) ml(-1) with a common identification step by agarose gel electrophoresis. Only one NS5 primer pair allowed the detection of all tested flaviviruses with the sensitivity limit of 10(5) TCID(50)s ml(-1). Using a heminested PCR with new primers designed in the same region after an alignment of 30 different flaviviruses, the sensitivity of reverse transcription-PCR was improved and allowed the detection of about 200 infectious doses ml(-1) with all of the tick- and mosquito-borne flaviviruses tested. It was confirmed that the sequenced amplified products in the NS5 region allowed predictability of flavivirus species by dendrogram, including the New York 99 West Nile strain. This technique was successfully performed with a cerebrospinal fluid sample from a patient hospitalized with West Nile virus encephalitis.

Mosquito cells bind and replicate hepatitis C virus

Several studies have demonstrated some hepatitis C virus (HCV) replication in lymphocyte and hepatocyte cell lines such as in African green monkey Vero cells. The aim of the present study was to select other cell lines able to bind and replicate HCV. Human hepatoma PLC/PRF/5 cells, human lymphoma Namalwa cells, Vero and mosquito AP61 cells were inoculated with HCV-positive plasma, washed six times and examined for the presence of the viral genome at different times post infection, using an RT-PCR method. Binding of HCV to cells was estimated by HCV RNA detection in cells 2 hr after inoculation and in the last wash of these cells. Successive virus passages in cells were carried out. All the cells studied were able to bind HCV but only AP61 and Vero cells provided evidence of replication and production of infectious virus: virus RNA was detected during 28 days post-infection in four successive virus passages. CD81 molecules, a putative HCV receptor, were detected by cytofluorometric analysis. Vero cells express CD81 molecules whereas these molecules were not detected on AP61 cells. It is suggested that other receptors are involved in HCV binding to Vero and AP61 cells.

Diagnostic moléculaire en pathologie infectieuse: intérêt d'un diagnostic multiplex dans les pneumopathies atypiques

Parmi les pathogènes responsables de pneumopathies atypiques, Mycoplasma pneumoniae, Chlamydia pneumoniae, et Legionella pneumophila sont trois bactéries fréquentes pour lesquelles un diagnostic étiologique rapide est difficile à obtenir. L'amplification génique in vitro offre une possibilité de rendu de résultats dans la journée, mais souvent au détriment d'un temps de réalisation important du fait du manque d'automatisation. Cet inconvénient est réduit en cas d'utilisation de techniques d'amplification génique multiplex, dont un exemple de réalisation est présenté dans cet article.

Persistence of infectious hepatitis A virus and its genome in artificial seawater

The stability of the hepatitis A virus (HAV) genome detectable by RT-PCR in artificial sterile seawater seeded with HAV has been compared to that of HAV detectable in cell culture. The HAV genome was detectable by RT-PCR for 232 days while virus particles were detectable in cell culture for only 35 days. This difference in stability indicates that detection of the HAV genome by RT-PCR is not a reliable indicator of the survival of HAV detectable in cell cultures. However, before these results can be extrapolated to stability in natural seawater, the effect of additional elements in the natural environment, such as bacteria, fungi and suspended matter, on the stability of the HAV genome and cell culture infectious HAV particles, will have to be examined.

Inhibition of sandfly fever Sicilian virus (Phlebovirus) replication in vitro by antiviral compounds

Sandfly fever Sicilian virus (SFSV) was used in our laboratory to screen antiviral substances active toward viruses of the Bunyaviridae family. Antiviral activity was estimated by the reduction of the cytopathic effect of SFSV on infected Vero cells. Cytotoxicity was evaluated by determining the inhibition of Trypan blue exclusion. The specificity of action of each tested compound was estimated by the selectivity index (CD50/ED50). Selectivity indices of human recombinant interferon-alpha (IFN alpha) (Roferon and Introna), iota-, kappa- and lambda- carrageenans, fucoidan and 6-azauridine were much higher than that of ribavirin, the only antiviral substance which has been previously investigated for its inhibitory effects on Phlebovirus infections. Other compounds showed significant antiviral activity: glycyrrhizin, suramin sodium, dextran sulphate and pentosan polysulphate. All these compounds caused a concentration-dependent reduction in the virus yield. Ribavirin, 6-azauridine and IFN alpha have been shown to inhibit a late step of the virus replicative cycle, whereas glycyrrhizin and suramin sodium were active at an early step and the sulphated polysaccharides inhibited adsorption of SFSV on the cells. The antiviral compounds selected in this study as specific inhibitors of in vitro replication of SFSV are promising candidates for the chemotherapy of haemorrhagic fevers caused by viruses of the Bunyaviridae family. The combination of IFN alpha and ribavirin, which showed a synergistic antiviral effect, should be evaluated for the treatment of these infections.