Malignant catarrhal fever of cattle is associated with low abundance of IL-2 transcript and a predominantly latent profile of ovine herpesvirus 2 gene expression

The Impact of Whole Sesame Seeds on the Expression of Key-Genes Involved in the Innate Immunity of Dairy Goats

Whole sesame seeds (WSS) are rich in both linoleic acid (LA) and lignans. However, their impact on the innate immunity of goats is not well studied. Twenty-four goats were divided into three homogeneous sub-groups; comprise one control (CON) and two treated (WWS5 and WWS10). In the treated groups, WSS were incorporated in the concentrates of the CON at 5 (WSS5) and 10% (WSS10) respectively, by partial substitution of both soybean meal and corn grain. The expression levels of MAPK1, IL6, TRIF, IFNG, TRAF3, and JUND genes in the neutrophils of WSS10 fed goats were reduced significantly compared with the CON. The same was found for the expression levels of IFNG and TRAF3 genes in the neutrophils of WSS5 fed goats. Both treated groups primarily affected the MYD88-independent pathway. The dietary supplementation of goats with WSS might be a good nutritional strategy to improve their innate immunity.

Herpesvirus surveillance and discovery in zoo-housed ruminants

Gammaherpesvirus infections are ubiquitous in captive and free-ranging ruminants and are associated with a variety of clinical diseases ranging from subclinical or mild inflammatory syndromes to fatal diseases such as malignant catarrhal fever. Gammaherpesvirus infections have been fully characterized in only a few ruminant species, and the overall diversity, host range, and biologic effects of most are not known. This study investigated the presence and host distribution of gammaherpesviruses in ruminant species at two facilities, the San Diego Zoo and San Diego Zoo Safari Park. We tested antemortem (blood, nasal or oropharyngeal swabs) or postmortem (internal organs) samples from 715 healthy or diseased ruminants representing 96 species and subspecies, using a consensus-based herpesvirus PCR for a segment of the DNA polymerase (DPOL) gene. Among the 715 animals tested, 161 (22.5%) were PCR and sequencing positive for herpesvirus, while only 11 (6.83%) of the PCR positive animals showed clinical signs of malignant catarrhal fever. Forty-four DPOL genotypes were identified of which only 10 have been reported in GenBank. The data describe viral diversity within species and individuals, identify host ranges of potential new viruses, and address the proclivity and consequences of interspecies transmission during management practices in zoological parks. The discovery of new viruses with wide host ranges and presence of co-infection within individual animals also suggest that the evolutionary processes influencing Gammaherpesvirus diversity are more complex than previously recognized.

Implementation of next-generation sequencing for virus identification in veterinary diagnostic laboratories

The value of next-generation sequencing (NGS)-based applications for testing purposes in human medicine is widely recognized. Although NGS-based metagenomic screening may be of interest in veterinary medicine, in particular for intensively farmed livestock species such as pigs, there is a lack of protocols tailored to veterinary requirements, likely because of the high diversity of species and samples. Therefore, we developed an NGS-based protocol for use in veterinary virology and present here different applications in porcine medicine. To develop the protocol, each step of sample preparation was optimized using porcine samples spiked with various RNA and DNA viruses. The resulting protocol was tested with clinical samples previously confirmed to be positive for specific viruses by a diagnostic laboratory. Additionally, we validated the protocol in an NGS viral metagenomics ring trial and tested the protocol on viral multiplex reference material (NIBSC, U.K.). We applied our ViroScreen protocol successfully for 1) virus identification, 2) virus characterization, and 3) herd screening. We identified torque teno sus virus and atypical porcine pestivirus in a neurologic case, determined the full-length genome sequence of swine influenza A virus in field samples, and screened pigs using pen floor fecal samples and chewing rope liquid.

Sheep-Associated Malignant Catarrhal Fever: Role of Latent Virus and Macrophages in Vasculitis

Malignant catarrhal fever (MCF) is a sporadic, generally fatal disease caused by gammaherpesviruses in susceptible dead-end hosts. A key pathological process is systemic vasculitis in which productively infected cytotoxic T cells play a major role. Nonetheless, the pathogenesis of MCF vasculitis is not yet clear. We hypothesized that it develops due to an interaction between virus-infected cells and immune cells, and we undertook a retrospective in situ study on the rete mirabile arteries of confirmed ovine gammaherpesvirus-2 (OvHV-2)-associated MCF cases in cattle, buffalo, and bison. Our results suggest that the arteritis develops from an adventitial infiltration of inflammatory cells from the vasa vasorum, and recruitment of leukocytes from the arterial lumen that leads to a superimposed infiltration of the intima and media that can result in chronic changes including neointimal proliferation. We found macrophages and T cells to be the dominant infiltrating cells, and both could proliferate locally. Using RNA in situ hybridization and immunohistology, we showed that the process is accompanied by widespread viral infection, not only in infiltrating leukocytes but also in vascular endothelial cells, medial smooth muscle cells, and adventitial fibroblasts. Our results suggest that OvHV-2-infected T cells, monocytes, and locally proliferating macrophages contribute to the vasculitis in MCF. The initial trigger or insult that leads to leukocyte recruitment and activation is not yet known, but there is evidence that latently infected, activated endothelial cells play a role in this. Activated macrophages might then release the necessary pro-inflammatory mediators and, eventually, induce the characteristic vascular changes.

Cerebral Ovine Herpesvirus 2 Infection of Cattle Is Associated With a Variable Neuropathological Phenotype

Cross-species infection with ovine herpesvirus 2 (OvHV-2) in cattle causes malignant catarrhal fever (MCF). MCF may involve the central nervous system (CNS) with necrotizing arteritis and/or vasculitis described to be unique to MCF and discriminatory compared to other viral CNS infections. However, a systematic histopathological characterization of the neural form of MCF in cattle is lacking. We examined medulla oblongata (n = 9) or the entire brain (n = 9) of 18 cattle in which OvHV-2 was identified by quantitative polymerase chain reaction (qPCR), in order to pinpoint potential variations in neuropathology. In 2/18 animals (11%) no lesions were identified, while 16/18 cattle (89%) had brain lesions of varying severity. Presence and quantities of OvHV-2 nucleic acid were determined by in situ hybridization and qPCR, respectively, and were related to the severity of lesions. Fifteen of 18 animals (83%) showed vasculitis, which was mainly of the lymphohistiocytic type, while pathognomonic necrotizing arteritis was only rarely present. Neuroparenchymal lesions included gliosis and/or neuronal changes in 7/16 brains with lesions (44%). The number of CD3+ lymphocytes was highest in animals with simultaneous vascular and neuroparenchymal lesions and high viral genome load. In one animal, OvHV-2 was exclusively observed in CD3+ lymphocytes but not in neurons or microglia. In conclusion, the neuropathological phenotype of bovine MCF in the brain was variable. In some cases, lesions mimicked neurotropic viral encephalitis, while pathognomonic necrotizing arteritis was not a consistent feature of neural MCF. Therefore, molecular detection of OvHV-2 is warranted in the presence of nonsuppurative encephalitis and in the absence of necrotizing arteritis.

Identification and Prevalence of Phascolarctid Gammaherpesvirus Types 1 and 2 in South Australian Koala Populations

To determine Phascolarctid gammaherpesviruses (PhaHV) infection in South Australian koala populations, 80 oropharyngeal swabs from wild-caught and 87 oropharyngeal spleen samples and swabs from euthanased koalas were tested using two specific PCR assays developed to detect PhaHV-1 and PhaHV-2. In wild-caught koalas, active shedding of PhaHV was determined by positive oropharyngeal samples in 72.5% (58/80) of animals, of which 44.8% (26/58) had PhaHV-1, 20.7% (12/58) PhaHV-2 and 34.5% (20/58) both viral subtypes. In the euthanased koalas, systemic infection was determined by positive PCR in spleen samples and found in 72.4% (63/87) of koalas. Active shedding was determined by positive oropharyngeal results and found in 54.0% (47/87) of koalas. Koalas infected and actively shedding PhaHV-1 alone, PhaHV-2 alone or shedding both viral subtypes were 48.9% (23/47), 14.9% (7/47) and 36.2% (17/47), respectively. Only 45.9% (40/87) were not actively shedding, of which 40.0% (16/40) of these had systemic infections. Both wild-caught and euthanased koalas actively shedding PhaHV-2 were significantly more likely to be actively shedding both viral subtypes. Active shedding of PhaHV-2 had a significant negative correlation with BCS in the euthanased cohort, and active shedding of PhaHV-1 had a significant positive relationship with age in both wild-caught and euthanased cohorts.

Ovine Herpesvirus 2 Encodes a Previously Unrecognized Protein, pOv8.25, That Targets Mitochondria and Triggers Apoptotic Cell Death

Ovine herpesvirus 2 (OvHV-2) circulates among sheep without causing disease. However, upon transmission to cattle, the same virus instigates a frequently lethal disease, malignant catarrhal fever (MCF). While the cause of death and pathogenesis of tissue lesions are still poorly understood, MCF is characterized by the accumulation of lymphocytes in various tissues, associated with vasculitis and cell death. As infectious virus is hardly present in these lesions, the cause of cell death cannot be explained simply by viral replication. The significance of our research is in identifying and characterizing a previously overlooked gene of OvHV-2 (Ov8.25), which is highly expressed in animals with MCF. Its encoded protein targets mitochondria, causing apoptosis and necrosis, thus contributing to an understanding of the source and nature of cell death. As the corresponding genetic locus is also active in the context of MCF due to a different macavirus, we may have detected a common denominator of the disease phenotype.

Malignant catarrhal fever (MCF) is a rare but frequently lethal disease of certain cloven-hoofed animals. At least 10 different viruses, all members of the Macavirus genus in the subfamily Gammaherpesvirinae, are known as causative agents of MCF. Among these, ovine herpesvirus 2 (OvHV-2) is the most frequent and economically most important MCF agent. Phenotypically, MCF is characterized by severe lymphocytic arteritis-periarteritis, which leads to the accumulation of activated lymphocytes accompanied by apoptosis and necrosis in a broad range of tissues. However, a viral factor that might be responsible for tissue damage has not yet been identified. We have studied a seemingly intergenic locus on the OvHV-2 genome, which was previously shown to be transcriptionally highly active in MCF-affected tissue. We identified by 5′ and 3′ rapid amplification of cDNA ends (RACE) a conserved, double-spliced transcript that encoded a 9.9-kDa hydrophobic protein. The newly detected gene, Ov8.25, and its splicing pattern were conserved among OvHV-2 strains of different origins. Upon transient expression of synthetic variants of this gene in various cell types, including bovine lymphocytes, the protein (pOv8.25) was shown to target mitochondria, followed by caspase-dependent apoptosis and necrosis. Notably, a deletion mutant of the same protein lost these abilities. Finally, we detected pOv8.25 in brain-infiltrating lymphocytes of cattle with MCF. Thus, the cell death-causing properties of pOv8.25 in affected cells may be involved in the emergence of typical MCF-associated apoptosis and necrosis. Thus, we have identified a novel OvHV-2 protein, which might contribute to the phenotype of MCF-related lesions.

IMPORTANCE Ovine herpesvirus 2 (OvHV-2) circulates among sheep without causing disease. However, upon transmission to cattle, the same virus instigates a frequently lethal disease, malignant catarrhal fever (MCF). While the cause of death and pathogenesis of tissue lesions are still poorly understood, MCF is characterized by the accumulation of lymphocytes in various tissues, associated with vasculitis and cell death. As infectious virus is hardly present in these lesions, the cause of cell death cannot be explained simply by viral replication. The significance of our research is in identifying and characterizing a previously overlooked gene of OvHV-2 (Ov8.25), which is highly expressed in animals with MCF. Its encoded protein targets mitochondria, causing apoptosis and necrosis, thus contributing to an understanding of the source and nature of cell death. As the corresponding genetic locus is also active in the context of MCF due to a different macavirus, we may have detected a common denominator of the disease phenotype.

The effects of dietary supplementation with rumen-protected amino acids on the expression of several genes involved in the immune system of dairy sheep

Amino acids might be a tool to transform animals from a pro- to an anti-inflammatory phenotype through the downregulation of several genes (TLR-4, NF-κB, TNFa, IL-1β, IL-2, IL-6, IL-8, CCL-5 and CXCL-16) whose expression increases during inflammation. To examine this possibility, each of sixty Chios dairy sheep was assigned to one of the following five dietary treatments: A: basal diet (control group); B: basal diet +6.0 g/head rumen-protected methionine (MetaSmart^™ ); C: basal diet +5.0 g/head rumen-protected lysine (LysiGEM^™ ); D: basal diet +6.0 g/head MetaSmart^™  + 5.0 g/head LysiGEM^™ ; and E: basal diet +12.0 g/head MetaSmart^™  + 5.0 g/head LysiGEM. The results showed a significant downregulation in the expression of the TLR-4 gene in both the macrophages and the neutrophils of ewes fed rumen-protected amino acids. Significantly lower mRNA transcript accumulation was also observed for the TNFa, IL-1β and CXCL-16 genes in the macrophages and for the IL-1β gene in the neutrophils of ewes supplemented with amino acids. The ewes that received dietary supplementation with rumen-protected lysine alone (C) had significantly lower CCL-5 transcript levels in their macrophages than the ewes fed the other supplemented diets. Diet D enhanced the mRNA expression of the IL-2 gene in ewe neutrophils. Negative correlations were found between: a. TLR-4, TNFa, IL-1β and CXCL-16 gene expression in macrophages and the milk fat and total solids content; b. CCL-5 gene expression in neutrophils and the milk yield and FCM_(6%) ; and c. CXCL-16 gene expression and the milk protein content. Moreover, positive correlations were found between the BHBA concentration and the expression of the TLR-4 and CXCL-16 genes in macrophages. In conclusion, the rumen-protected amino acids improved sheep metabolism (as indicated by reduced blood BHBA and urea concentrations), milk chemical composition and immune system function.

The A2 gene of alcelaphine herpesvirus-1 is a transcriptional regulator affecting cytotoxicity in virus-infected T cells but is not required for malignant catarrhal fever induction in rabbits

Alcelaphine herpesvirus-1 (AlHV-1) causes malignant catarrhal fever (MCF). The A2 gene of AlHV-1 is a member of the bZIP transcription factor family. We wished to determine whether A2 is a virulence gene or not and whether it is involved in pathogenesis by interference with host transcription pathways. An A2 gene knockout (A2ΔAlHV-1) virus, revertant (A2revAlHV-1) virus, and wild-type virus (wtAlHV-1) were used to infect three groups of rabbits. A2ΔAlHV-1-infected rabbits succumbed to MCF, albeit with a delayed onset compared to the control groups, so A2 is not a critical virulence factor. Differential gene transcription analysis by RNAseq and qRT-PCR validation of a selection of these was performed in infected large granular lymphocyte (LGL) T cells obtained in culture from the MCF-affected animals. A2 was involved in the transcriptional regulation of immunological, cell cycle and apoptosis pathways. In particular, there was a bias towards γδ T cell receptor (TCR) expression and downregulation of αβ TCR. TCR signalling, apoptosis, cell cycle, IFN-γ and NFAT pathways were affected. Of particular interest was partial inhibition of the cytotoxicity-associated pathways involving perforin and the granzymes A and B in the A2ΔAlHV-1-infected LGLs compared to controls. In functional assays, A2ΔAlHV-1-infected LGLs were significantly less cytotoxic than wtAlHV-1- and A2revAlHV-1-infected LGLs using rabbit corneal epithelial cells (SIRC) as targets. This implies that A2 is involved in a pathway enhancing the expression of LGL cytotoxicity. This is important as virus-infected T cell cytotoxicity in vivo has been suggested as a potential mechanism of disease induction in MCF.

The pathology of malignant catarrhal fever, with an emphasis on ovine herpesvirus 2

The enigmatic pathogenesis of malignant catarrhal fever (MCF) involves dysregulated immune responses in susceptible ruminant species. Economically important outbreaks of MCF are due to 2 of the 10 viruses currently comprising the malignant catarrhal fever virus group: ovine herpesvirus 2 (OvHV-2) and alcelaphine herpesvirus 1 (AlHV-1). Attempts to develop effective vaccines for this group of viruses in the 1970s were sufficiently discouraging that they were temporarily abandoned. This review focuses on recent efforts to understand the pathogenesis of MCF, particularly the sheep-associated form of the disease, with the goal of developing rational control methods, including vaccination. The past 2 decades have seen several advances, including recognition of new members of the MCF virus group, better diagnostic assays, induction of disease by a natural route (aerosol), and clearer understanding of OvHV-2's shedding patterns by domestic sheep. A consistent theme in experimental studies of OvHV-2 in susceptible species is that there are 2 peaks of OvHV-2 gene expression: a preclinical peak involving the respiratory tract and a second in multiple organ systems leading to clinical disease. Latent and lytic gene expression may coexist in tissues during clinical stages in symptomatic animals.

Malignant catarrhal fever: inching toward understanding

Malignant catarrhal fever (MCF) is an often lethal infection of many species in the order Artiodactyla. It is caused by members of the MCF virus group within Gammaherpesvirinae. MCF is a worldwide problem and has a significant economic impact on highly disease-susceptible hosts, such as cattle, bison, and deer. Several epidemiologic forms of MCF, defined by the reservoir ruminant species from which the causative virus arises, are recognized. Wildebeest-associated MCF (WA-MCF) and sheep-associated MCF (SA-MCF) are the most prevalent and well-studied forms of the disease. Historical understanding of MCF is largely based on WA-MCF, in which the causative virus can be propagated in vitro. Characterization of SA-MCF has been constrained because the causative agent has never been successfully propagated in vitro. Development of molecular tools has enabled more definitive studies on SA-MCF. The current understanding of MCF, including its etiological agents, epidemiology, pathogenesis, and prevention, is the subject of the present review.

An essential role for γ-herpesvirus latency-associated nuclear antigen homolog in an acute lymphoproliferative disease of cattle

Wildebeests carry asymptomatically alcelaphine herpesvirus 1 (AlHV-1), a γ-herpesvirus inducing malignant catarrhal fever (MCF) to several ruminant species (including cattle). This acute and lethal lymphoproliferative disease occurs after a prolonged asymptomatic incubation period after transmission. Our recent findings with the rabbit model indicated that AlHV-1 infection is not productive during MCF. Here, we investigated whether latency establishment could explain this apparent absence of productive infection and sought to determine its role in MCF pathogenesis. First, whole-genome cellular and viral gene expression analyses were performed in lymph nodes of MCF-developing calves. Whereas a severe disruption in cellular genes was observed, only 10% of the entire AlHV-1 genome was expressed, contrasting with the 45% observed during productive infection in vitro. In vivo, the expressed viral genes included the latency-associated nuclear antigen homolog ORF73 but none of the regions known to be essential for productive infection. Next, genomic conformation analyses revealed that AlHV-1 was essentially episomal, further suggesting that MCF might be the consequence of a latent infection rather than abortive lytic infection. This hypothesis was further supported by the high frequencies of infected CD8(+) T cells during MCF using immunodetection of ORF73 protein and single-cell RT-PCR approaches. Finally, the role of latency-associated ORF73 was addressed. A lack of ORF73 did not impair initial virus replication in vivo, but it rendered AlHV-1 unable to induce MCF and persist in vivo and conferred protection against a lethal challenge with a WT virus. Together, these findings suggest that a latent infection is essential for MCF induction.

Host gene expression changes in cattle infected with Alcelaphine herpesvirus 1

Malignant catarrhal fever is a lymphoproliferative disease of cattle and other ungulates caused by infection with gamma-herpesviruses of the genus Macavirus. These viruses do not establish a productive infection but instead replicate in a cell-associated fashion in T lymphocytes, leading to systemic immune dysregulation and a generally fatal outcome. Despite significant progress in understanding the pathology of this disease, its pathogenesis remains unclear. To identify genes and pathways affected in clinical MCF, sixteen bovine GeneCHIP microarrays were used to assay RNA from kidney and lymph node of four MCF-affected and four control Bos taurus steers. This is the first expression study of AlHV-1-MCF in the bovine host. Over 250 genes showed significant changes in gene expression in either lymph node or kidney, while expression of 35 genes was altered in both tissues. Pathway and annotation analysis of the microarray data showed that immune response and inflammatory genes were up-regulated in the kidney while proliferation-associated transcripts were additionally increased in the lymph node. The genes that showed the largest expression rises in both diseased tissues included cytotoxic enzymes and pro-inflammatory chemokines. These data are consistent with disease-induced stimulation of inflammatory responses involving interferon-γ, including cytotoxic T cell recruitment and activation in peripheral tissues containing virus-infected cells. However it remains unclear whether the tissue damage in MCF lesions is due entirely to the activity of infected cells or whether uninfected T cells, recruited and activated at lesion sites through the action of infected cells, contribute to the pathogenesis of MCF.

Duration of protective immunity and antibody responses in cattle immunised against alcelaphine herpesvirus-1-induced malignant catarrhal fever

Protection of cattle from alcelaphine herpesvirus-1 (AlHV-1)-induced malignant catarrhal fever (MCF) has been described previously, using an attenuated virus vaccine in an unlicensed adjuvant. The vaccine was hypothesised to induce a protective barrier of virus-neutralising antibody in the oro-nasal region, supported by the observation of high titre neutralising antibodies in nasal secretions of protected animals. Here we describe further analysis of this vaccine strategy, studying the effectiveness of the vaccine formulated with a licensed adjuvant; the duration of immunity induced; and the virus-specific antibody responses in plasma and nasal secretions. The results presented here show that the attenuated AlHV-1 vaccine in a licensed adjuvant protected cattle from fatal intranasal challenge with pathogenic AlHV-1 at three or six months. In addition, animals protected from MCF had significantly higher initial anti-viral antibody titres than animals that succumbed to disease; and these antibody titres remained relatively stable after challenge, while titres in vaccinated animals with MCF increased significantly prior to the onset of clinical disease. These data support the view that a mucosal barrier of neutralising antibody blocks infection of vaccinated animals and suggests that the magnitude of the initial response may correlate with long-term protection. Interestingly, the high titre virus-neutralising antibody responses seen in animals that succumbed to MCF after vaccination were not protective.

Novel virus-encoded microRNA molecules expressed by ovine herpesvirus 2-immortalized bovine T-cells

A number of herpesviruses have now been shown to encode microRNAs (miRNAs) that have roles in control of both viral and cellular gene expression. Ovine herpesvirus 2 (OvHV-2) is the causative agent of sheep-associated malignant catarrhal fever, a fatal lymphoproliferative disease of cattle. Using massively parallel sequencing and Northern hybridization we have identified eight putative miRNAs encoded by OvHV-2 expressed in an OvHV-2-immortalized bovine lymphocyte cell line. These eight miRNAs are encoded in two areas of the OvHV-2 genome that contain no predicted protein coding regions and show no sequence similarity with other herpesvirus or cellular miRNAs. This represents the first report of the expression of virally encoded miRNAs in the genus Macavirus of herpesviruses.

Malignant catarrhal fever induced by Alcelaphine herpesvirus 1 is characterized by an expansion of activated CD3+CD8+CD4- T cells expressing a cytotoxic phenotype in both lymphoid and non-lymphoid tissues

Alcelaphine herpesvirus 1 (AlHV-1) is carried by wildebeest asymptomatically. It causes a fatal lymphoproliferative disease named wildebeest-derived malignant catarrhal fever (WD-MCF) when cross-species transmitted to a variety of susceptible species of the Artiodactyla order. WD-MCF can be reproduced experimentally in rabbits. In a previous report, we demonstrated that WD-MCF induced by AlHV-1 is associated with a severe proliferation of CD8(+) T cells in the lymphoid tissues. Here, we further studied the mononuclear leukocytic populations in both the lymphoid (throughout the infection and at time of euthanasia) and non-lymphoid (at time of euthanasia) organs during WD-MCF induced experimentally in rabbits. To reach that goal, we performed multi-colour flow cytometry stainings. The results obtained demonstrate that the development of WD-MCF correlates in peripheral blood with a severe increase of CD8(+) cell percentages; and that CD3(+)CD8(+)CD4(-) T cells were the predominant cell type in both lymphoid and non-lymphoid organs at time of euthanasia. Further characterization of the mononuclear leukocytes isolated from both lymphoid and non-lymphoid tissues revealed that the CD8(+) T cells express high levels of the activation markers CD25 and CD44, produce high amount of gamma-interferon (IFN-γ) and perforin, and showed a reduction of interleukin-2 (IL-2) gene expression. These data demonstrate that the development of WD-MCF is associated with the expansion and infiltration of activated and cytotoxic CD3(+)CD8(+)CD4(-) T cells secreting high amount of IFN-γ but low IL-2.

Ex vivo bioluminescence detection of alcelaphine herpesvirus 1 infection during malignant catarrhal fever

Alcelaphine herpesvirus 1 (AlHV-1), carried by wildebeest asymptomatically, causes malignant catarrhal fever (WD-MCF) when cross-species transmitted to a variety of susceptible species of the Artiodactyla order. Experimentally, WD-MCF can be reproduced in rabbits. WD-MCF is described as a combination of lymphoproliferation and degenerative lesions in virtually all organs and is caused by unknown mechanisms. Recently, we demonstrated that WD-MCF is associated with the proliferation of CD8(+) cells supporting a latent type of infection in lymphoid tissues. Here, we investigated the macroscopic distribution of AlHV-1 infection using ex vivo bioluminescence imaging in rabbit to determine whether it correlates with the distribution of lesions in lymphoid and nonlymphoid organs. To reach that goal, a recombinant AlHV-1 strain was produced by insertion of a luciferase expression cassette (luc) in an intergenic region. In vitro, the reconstituted AlHV-1 luc(+) strain replicated comparably to the parental strain, and luciferase activity was detected by bioluminescence imaging. In vivo, rabbits infected with the AlHV-1 luc(+) strain developed WD-MCF comparably to rabbits infected with the parental wild-type strain, with hyperthermia and increases of both CD8(+) T cell frequencies and viral genomic charge over time in peripheral blood mononuclear cells and in lymph nodes at time of euthanasia. Bioluminescent imaging revealed that AlHV-1 infection could be detected ex vivo in lymphoid organs but also in lung, liver, and kidney during WD-MCF, demonstrating that AlHV-1 infection is prevalent in tissue lesions. Finally, we show that the infiltrating mononuclear leukocytes in nonlymphoid organs are mainly CD8(+) T cells and that latency is predominant during WD-MCF.

Mastitis associated transcriptomic disruptions in cattle

Mastitis is ranked as the top disease for dairy cattle based on traditional cost analysis. Greater than 100 organisms from a broad phylogenetic spectrum are able to cause bovine mastitis. Transcriptomic characterization facilitates our understanding of host-pathogen relations and provides mechanistic insight into host resistance to mastitis. In this review, we discuss effector mechanisms and transcriptomic changes within the mammary gland in response to experimental infections. We compare temporal, spatial and pathogen-specific local transcriptomic disruptions in the mammary gland as well as pathogen-induced systemic responses and transcriptional changes in distant organs. We attempt to explain why studies on transcriptomic changes during critical physiological periods and in response to non-mastitic pathogens may have important implications for mastitis studies. Future perspectives on revealing bidirectional molecular cross-talk between mastitis pathogens and host cells using cutting-edge genomic technologies are also discussed.