Characterization of Ovine A3Z1 Restriction Properties against Small Ruminant Lentiviruses (SRLVs).

Intrinsic factors of the innate immune system include the apolipoprotein B editing enzyme catalytic polypeptide-like 3 (APOBEC3) protein family. APOBEC3 inhibits replication of different virus families by cytosine deamination of viral DNA and a not fully characterized cytosine deamination-independent mechanism. Sheep are susceptible to small ruminant lentivirus (SRLVs) infection and contain three APOBEC3 genes encoding four proteins (A3Z1, Z2, Z3 and Z2-Z3) with yet not deeply described antiviral properties. Using sheep blood monocytes and in vitro-derived macrophages, we found that A3Z1 expression is associated with lower viral replication in this cellular type. A3Z1 transcripts may also contain spliced variants (A3Z1Tr) lacking the cytidine deaminase motif. A3Z1 exogenous expression in fully permissive fibroblast-like cells restricted SRLVs infection while A3Z1Tr allowed infection. A3Z1Tr was induced after SRLVs infection or stimulation of blood-derived macrophages with interferon gamma (IFN-γ). Interaction between truncated isoform and native A3Z1 protein was detected as well as incorporation of both proteins into virions. A3Z1 and A3Z1Tr interacted with SRLVs Vif, but this interaction was not associated with degradative properties. Similar A3Z1 truncated isoforms were also present in human and monkey cells suggesting a conserved alternative splicing regulation in primates. A3Z1-mediated retroviral restriction could be constrained by different means, including gene expression and specific alternative splicing regulation, leading to truncated protein isoforms lacking a cytidine-deaminase motif.

Diagnosing infection with small ruminant lentiviruses of genotypes A and B by combining synthetic peptides in ELISA.

The major challenges in diagnosing small ruminant lentivirus (SRLV) infection include early detection and genotyping of strains of epidemiological interest. A longitudinal study was carried out in Rasa Aragonesa sheep experimentally infected with viral strains of genotypes A or B from Spanish neurological and arthritic SRLV outbreaks, respectively. Sera were tested with two commercial ELISAs, three based on specific peptides and a novel combined peptide ELISA. Three different PCR assays were used to further assess infection status. The kinetics of anti-viral antibody responses were variable, with early diagnosis dependent on the type of ELISA used. Peptide epitopes of SRLV genotypes A and B combined in the same ELISA well enhanced the overall detection rate, whereas single peptides were useful for genotyping the infecting strain (A vs. B). The results of the study suggest that a combined peptide ELISA can be used for serological diagnosis of SRLV infection, with single peptide ELISAs useful for subsequent serotyping.

Modulation of the long terminal repeat promoter activity of small ruminant lentiviruses by steroids.

Production and excretion of small ruminant lentiviruses (SRLVs) varies with the stage of the host reproductive cycle, suggesting hormonal involvement in this variation. Stress may also affect viral expression. To determine if hormones affect SRLV transcriptional activity, the expression of green fluorescent protein (GFP) driven by the promoters in the U3-cap region of the long terminal repeats (LTRs) of different strains of SRLV was assessed in cell culture. High concentrations of steroids (progesterone, cortisol and dehydroepiandrosterone) inhibited expression of GFP driven by SRLV promoters. This effect decreased in a dose-dependent manner with decreasing concentrations of steroids. In some strains, physiological concentrations of cortisol or dehydroepiandrosterone (DHEA) induced the expression of GFP above the baseline. There was strain variation in sensitivity to hormones, but this differed for different hormones. The presence of deletions and a 43 base repeat in the U3 region upstream of the TATA box of the LTR made strain EV1 less sensitive to DHEA. However, no clear tendencies or patterns were observed when comparing strains of different genotypes and/or subtypes, or those triggering different forms of disease.

Small ruminant macrophage polarization may play a pivotal role on lentiviral infection.

Small ruminant lentiviruses (SRLV) infect the monocyte/macrophage lineage inducing a long-lasting infection affecting body condition, production and welfare of sheep and goats all over the world. Macrophages play a pivotal role on the host's innate and adaptative immune responses against parasites by becoming differentially activated. Macrophage heterogeneity can tentatively be classified into classically differentiated macrophages (M1) through stimulation with IFN-γ displaying an inflammatory profile, or can be alternatively differentiated by stimulation with IL-4/IL-13 into M2 macrophages with homeostatic functions. Since infection by SRLV can modulate macrophage functions we explored here whether ovine and caprine macrophages can be segregated into M1 and M2 populations and whether this differential polarization represents differential susceptibility to SRLV infection. We found that like in human and mouse systems, ovine and caprine macrophages can be differentiated with particular stimuli into M1/M2 subpopulations displaying specific markers. In addition, small ruminant macrophages are plastic since M1 differentiated macrophages can express M2 markers when the stimulus changes from IFN-γ to IL-4. SRLV replication was restricted in M1 macrophages and increased in M2 differentiated macrophages respectively according to viral production. Identification of the infection pathways in macrophage populations may provide new targets for eliciting appropriate immune responses against SRLV infection.

Mannose receptor may be involved in small ruminant lentivirus pathogenesis.

Thirty-one sheep naturally infected with small ruminant lentiviruses (SRLV) of known genotype (A or B), and clinically affected with neurological disease, pneumonia or arthritis were used to analyse mannose receptor (MR) expression (transcript levels) and proviral load in virus target tissues (lung, mammary gland, CNS and carpal joints). Control sheep were SRLV-seropositive asymptomatic (n = 3), seronegative (n = 3) or with chronic listeriosis, pseudotuberculosis or parasitic cysts (n = 1 in each case). MR expression and proviral load increased with the severity of lesions in most analyzed organs of the SRLV infected sheep and was detected in the affected tissue involved in the corresponding clinical disease (CNS, lung and carpal joint in neurological disease, pneumonia and arthritis animal groups, respectively). The increased MR expression appeared to be SRLV specific and may have a role in lentiviral pathogenesis.

The extradomain a of fibronectin enhances the efficacy of lipopolysaccharide defective Salmonella bacterins as vaccines in mice.

The Extradomain A from fibronectin (EDA) has an immunomodulatory role as fusion protein with viral and tumor antigens, but its effect when administered with bacteria has not been assessed. Here, we investigated the adjuvant effect of EDA in mice immunizations against Salmonella enterica subspecies enterica serovar Enteritidis (Salmonella Enteritidis). Since lipopolysaccharide (LPS) is a major virulence factor and the LPS O-polysaccharide (O-PS) is the immunodominant antigen in serological diagnostic tests, Salmonella mutants lacking O-PS (rough mutants) represent an interesting approach for developing new vaccines and diagnostic tests to differentiate infected and vaccinated animals (DIVA tests). Here, antigenic preparations (hot-saline extracts and formalin-inactivated bacterins) from two Salmonella Enteritidis rough mutants, carrying either intact (SEΔwaaL) or deep-defective (SEΔgal) LPS-Core, were used in combination with EDA. Biotinylated bacterins, in particular SEΔwaaL bacterin, decorated with EDAvidin (EDA and streptavidin fusion protein) improved the protection conferred by hot-saline or bacterins alone and prevented significantly the virulent infection at least to the levels of live attenuated rough mutants. These findings demonstrate the adjuvant effect of EDAvidin when administered with biotinylated bacterins from Salmonella Enteritidis lacking O-PS and the usefulness of BEDA-SEΔwaaL as non-live vaccine in the mouse model.

The extradomain A of fibronectin (EDA) combined with poly(I:C) enhances the immune response to HIV-1 p24 protein and the protection against recombinant Listeria monocytogenes-Gag infection in the mouse model.

The development of effective vaccines against HIV-1 infection constitutes one of the major challenges in viral immunology. One of the protein candidates in vaccination against this virus is p24, since it is a conserved HIV antigen that has cytotoxic and helper T cell epitopes as well as B cell epitopes that may jointly confer enhanced protection against infection when used in immunization-challenge approaches. In this context, the adjuvant effect of EDA (used as EDAp24 fusion protein) and poly(I:C), as agonists of TLR4 and TLR3, respectively, was assessed in p24 immunizations using a recombinant Listeria monocytogenes HIV-1 Gag proteins (Lm-Gag, where p24 is the major antigen) for challenge in mice. Immunization with EDAp24 fusion protein together with poly(I:C) adjuvant induced a specific p24 IFN-γ production (Th1 profile) as well as protection against a Lm-Gag challenge, suggesting an additive or synergistic effect between both adjuvants. The combination of EDA (as a fusion protein with the antigen, which may favor antigen targeting to dendritic cells through TLR4) and poly(I:C) could thus be a good adjuvant candidate to enhance the immune response against HIV-1 proteins and its use may open new ways in vaccine investigations on this virus.

Identification of the ovine mannose receptor and its possible role in Visna/Maedi virus infection.

This study aims to characterize the mannose receptor (MR) gene in sheep and its role in ovine visna/maedi virus (VMV) infection. The deduced amino acid sequence of ovine MR was compatible with a transmembrane protein having a cysteine-rich ricin-type amino-terminal region, a fibronectin type II repeat, eight tandem C-type lectin carbohydrate-recognition domains (CRD), a transmembrane region, and a cytoplasmic carboxy-terminal tail. The ovine and bovine MR sequences were closer to each other compared to human or swine MR. Concanavalin A (ConA) inhibited VMV productive infection, which was restored by mannan totally in ovine skin fibroblasts (OSF) and partially in blood monocyte-derived macrophages (BMDM), suggesting the involvement of mannosylated residues of the VMV ENV protein in the process. ConA impaired also syncytium formation in OSF transfected with an ENV-encoding pN3-plasmid. MR transcripts were found in two common SRLV targets, BMDM and synovial membrane (GSM) cells, but not in OSF. Viral infection of BMDM and especially GSM cells was inhibited by mannan, strongly suggesting that in these cells the MR is an important route of infection involving VMV Env mannosylated residues. Thus, at least three patterns of viral entry into SRLV-target cells can be proposed, involving mainly MR in GSM cells (target in SRLV-induced arthritis), MR in addition to an alternative route in BMDM (target in SRLV infections), and an alternative route excluding MR in OSF (target in cell culture). Different routes of SRLV infection may thus coexist related to the involvement of MR differential expression.

Association of CD80 and CD86 expression levels with disease status of Visna/Maedi virus infected sheep.

In small ruminant lentivirus infections, cellular immune responses are diminished in clinically affected animals. The underlying mechanisms for this are unknown. In this study, we tested the hypothesis that alterations in expression of the co-stimulatory molecules B7-1 and B7-2 are involved in infections with Visna/Maedi virus (VMV), the prototype lentivirus of sheep. We studied B7 expression levels ex vivo in peripheral blood mononuclear cells (PBMCs), determining B7 RNA levels by real time reverse transcriptase polymerase chain reaction in asymptomatic as well as clinically affected VMV-seropositive sheep. The levels of both B7 molecules were increased in VMV-seropositive asymptomatic sheep. However, in VMV clinically affected sheep, the level of CD80 (but not CD86) was low compared with the level in uninfected sheep (p < 0.05). CD80 and CD86 RNA levels were associated with the ability of PBMCs to respond to VMV gag antigens (p14, p17, and p25) by proliferation, with most seropositive asymptomatic sheep showing positive proliferative responses but clinically affected sheep showing no response. The response to p25 in clinically affected animals was increased by the addition of interleukin-2 to the cultures. Decreased recall responses to unrelated antigens (assessed by production of interferon-gamma) were also found in clinically affected sheep. Thus, among seropositive sheep, decreased B7-1 (CD80) RNA levels and diminished antigen-specific cellular immune responses in PBMCs point to a VMV disease status, whereas increased CD80 and CD86 levels and augmented cellular responses are linked to asymptomatic infection.

Expression of the gp150 maedi visna virus envelope precursor protein by mammalian expression vectors.

There are very few previous reports of expression of native full-length maedi visna virus (MVV) Env gp150 protein in the literature. Therefore the use of different plasmid and viral expression vectors to obtain full-length gp150 was investigated. A mammalian expression plasmid, pN3-Env, was constructed containing the MVV env gene encoding the precursor protein gp150 Env. The functionality of the recombinant plasmid was tested for expression in HEK293 cells. A recombinant modified vaccinia Ankara virus, MVA-Env, with expression detected in avian cells was also made. The expression of the MVV gp150 Env precursor protein was shown for the first time upon transfection of the eukaryotic HEK293 cells by the pN3-Env plasmid DNA as demonstrated by Western blot analysis. These plasmid or viral expression vectors are of potential use in MVV vaccines.

Interleukin-1, interleukin-6, and interleukin-10 responses after antibiotic treatment in experimental chronic Staphylococcus aureus osteomyelitis.

BACKGROUND: Staphylococcal implant infections' response to treatment may be correlated with cytokine production. We investigated the effect of certain antibiotics on the cytokine response in experimental osteomyelitis. METHODS: A stainless steel needle with an adherent slime-producing Staphylococcus aureus was implanted intramedullarly in the left tibia of 40 adult male Wistar rats. At 42 days after implantation, cefuroxime, vancomycin, tobramycin, and ciprofloxacin were administered intramuscularly every 12 h for 21 days. The control group was given no antibiotic. At the end of the treatment, implants and tibias were retrieved, and the bacterial numbers were estimated. Cytokines [interleukin-1alpha (IL-1alpha), IL-6, and IL-10] were determined (ELISA) in the tibial extract. RESULTS: Vancomycin and cefuroxime inhibited bone colonization in all tibias, and tobramycin and ciprofloxacin inhibited it only partially. Cefuroxime reduced the number of bacteria that adhered to the implants more than the other antibiotics. IL-1alpha and IL-6 showed higher levels in the ciprofloxacin-treated group than in the cefuroxime-treated and control groups. IL-6 levels in rats treated with cefuroxime were lower than in rats treated with tobramycin or vancomycin and the control group. Cefuroxime decreased IL-10 levels more than ciprofloxacin or vancomycin or those seen in the control group. CONCLUSIONS: The cefuroxime group showed the greatest decrease of pro-inflammatory cytokines. Different antibiotics produce different cytokine reactions that should be studied to choose the best treatment.

Maedi-visna virus infection of ovine mammary epithelial cells.

The aim of this work was to perform a complete study of maedi-visna virus (MVV) infected mammary glands of naturally-infected sheep, and to determine if cells other than macrophages undergo a productive viral infection in this organ. Fifteen seropositive and two seronegative ewes were selected from MVV-infected flocks on the basis of clinical indurative mastitis and three sheep from an MVV-free flock. Within the mammary gland, MVV-positive cells were located by immunohistochemistry in the stroma and the epithelial alveolar barrier, most likely the ovine mammary epithelial cells (OMEC) of the acini. In situ hybridization confirmed these findings. Ultrastructural studies showed the presence of lentivirus-like particles budding off the cell surface in the alveolar barrier and also free in the acinar lumen. The presence of mammary histopathological lesions and MVV together with clear indications of productive infection (demonstration of a cytopathic effect in OMEC cultures and infection of co-cultures) were observed in the 15 seropositive and one of the seronegative sheep from the infected flock. These findings demonstrate that the OMEC were infected in vivo and probably underwent productive infection when studied ex-vivo. The OMEC of MVV-free sheep, which had subsequently been infected in vitro with MVV, also showed productive infection when challenged in vitro, confirming the replication of MVV in OMEC in vitro. The presence of MVV-infected OMEC in the mammary gland from infected animals, the productive infection in these OMEC and the release of lentiviral particles to the acinar lumen may have relevance in the pathogenesis and transmission of MVV infection.

Mucosal immunization of sheep with a Maedi-Visna virus (MVV) env DNA vaccine protects against early MVV productive infection.

Gene gun mucosal DNA immunization of sheep with a plasmid expressing the env gene of Maedi-Visna virus (MVV) was used to examine the protection against MVV infection in sheep from a naturally infected flock. For immunization, sheep were primed with a pcDNA plasmid (pcDNA-env) encoding the Env glycoproteins of MVV and boosted with combined pcDNA-env and pCR3.1-IFN-gamma plasmid inoculations. The pcDNA plasmid used in the control group contained the lacZ coding sequences instead of the env gene. Within a month post-challenge, the viral load in the vaccinated group was lower (p < or = 0.05) and virus was only detected transiently compared with the control group. Furthermore, 2 months later, neutralizing antibodies (NtAb) were detected in all the control animals and none of the vaccinated animals (p < or = 0.01). These results demonstrated a significant early protective effect of this immunization strategy against MVV infection that restricts the virus replication following challenge in the absence of NtAb production. This vaccine protective effect against MVV infection disappeared after two years post-challenge, when active replication of MVV challenge strain was observed. Protection conferred by the vaccine could not be explained by OLA DRB1 allele or genotype differences. Most of the individuals were DRB1 heterozygous and none was totally resistant to infection.

Evaluation of four experimental osteomyelitis infection models by using precolonized implants and bacterial suspensions.

Staphylococcus aureus osteomyelitis, a major problem in orthopedic surgery, often involves biofilm bacteria adhering to implants and surrounding bone and tissues. The inadequacy of therapy or immunological surveillance has encouraged studies using animal models which simulate natural osteomyelitic infections, ensure the development of infections and avoid mortality. We evaluated 4 models for infection (8 animals/model) in rats, using stainless-steel implants in tibiae and a very adherent slime-producing bacterial strain. Each animal received: an implant containing a 12 h-biofilm with about 10(6) cfu (Model 1); an implant containing this biofilm and a suspension with about 10(4) cfu (Model 2): a sterile implant and a suspension with about 10(5) cfu (Model 3); or a sterile implant and a suspension with about 10(6) cfu (Model 4). 63 days after surgery we found 100% rat survival, colonization of bone by implant biofilm bacteria in some animals and local, but not systemic infections. Model 1 (but not Models 2-4) reproduced an infection in both, tibiae and implants, most reliably (in 100% of the animals). Model 3 was the least reliable (p < 0.01, 25% infected implants, 12% infected tibiae).