Inflammation and changes in cytokine levels in neurological feline infectious peritonitis

Comparison of Antiviral Immune Responses in Healthy Cats Induced by Two Immune Therapeutics

BACKGROUND

Effective immunotherapeutic agents for use in cats are needed to aid in the management of intractable viral diseases, including feline infectious peritonitis (FIP) infection. The objectives of this study were to compare two different immune stimulants for antiviral activity in cats: (1) TLR 2/6-activating compound polyprenyl immunostimulant; (PI) and (2) liposome Toll-like receptor 3/9 agonist complexes (LTCs) to determine relative abilities to stimulate the induction of type I (IFN-α, IFN-β) and type II (IFN-γ) interferon immune responses in vitro and to study the effects of treatment on immune responses in healthy cats.

METHODS

Cytokine and cellular immune responses to PI and LTC were evaluated using peripheral blood mononuclear cells (PBMCs) from healthy cats incubated with LTC and PI at indicated concentrations using reverse transcriptase polymerase chain reaction assays and ELISA assays. The effects of the immune stimulants on inhibiting FIPV replication were assessed using a feline macrophage cell line (fcwf-4). Cytokine and cellular immune responses to PI and LTC were evaluated in blood samples from healthy cats treated with PI and LTC, using reverse transcriptase polymerase chain reaction (RT-PCR) and ELISA assays.

RESULTS

In the in vitro studies, both compounds triggered the upregulated expression of IFN-α, IFN-γ, and IL-1β genes in cat PBMC, whereas treatment with LTC induced significantly greater expression of IFN-α and IFN-γ on Day 1 and IL-1b on Day 3. There was significant protection from FIPV-induced cytopathic effects when fcwf-4 cells were treated with conditioned medium from LTC-activated leukocytes. In the healthy cat study (in vivo), both PI and LTC increased the mRNA signal for IFN-α, IFN-γ, and IL-1β above baseline at multiple time points with statistically greater increases in the LTC group on either Day 1 (IFN-α, IFN-γ) or Day 3 (IL-1β). In addition, RANTES increased over time in cats treated with the LTC.

CONCLUSIONS

Both LTC and PI protocols induced immune-enhancing effects, suggesting a possible clinical use for the management of chronic infectious diseases like FIP. Activating the TLR 3 and 9 pathways (LTC) induced superior broad interferon production in vitro than the activation of the TLR 2 and 6 pathways (PI).

An Aptamer-Based Proteomic Analysis of Plasma from Cats (Felis catus) with Clinical Feline Infectious Peritonitis

Feline infectious peritonitis (FIP) is a systemic disease manifestation of feline coronavirus (FCoV) and is the most important cause of infectious disease-related deaths in domestic cats. FIP has a variable clinical manifestation but is most often characterized by widespread vasculitis with visceral involvement and/or neurological disease that is typically fatal in the absence of antiviral therapy. Using an aptamer-based proteomics assay, we analyzed the plasma protein profiles of cats who were naturally infected with FIP (n = 19) in comparison to the plasma protein profiles of cats who were clinically healthy and negative for FCoV (n = 17) and cats who were positive for the enteric form of FCoV (n = 9). We identified 442 proteins that were significantly differentiable; in total, 219 increased and 223 decreased in FIP plasma versus clinically healthy cat plasma. Pathway enrichment and associated analyses showed that differentiable proteins were related to immune system processes, including the innate immune response, cytokine signaling, and antigen presentation, as well as apoptosis and vascular integrity. The relevance of these findings is discussed in the context of previous studies. While these results have the potential to inform diagnostic, therapeutic, and preventative investigations, they represent only a first step, and will require further validation.

The association of astrogliosis and microglial activation with aging and Alzheimer's disease pathology in the chimpanzee brain

Aging and neurodegenerative disorders, such as Alzheimer's disease (AD), trigger an immune response known as glial activation in the brain. Recent evidence indicates species differences in inflammatory responses to AD pathology, highlighting the need for additional comparative studies to further understand human-specific neuropathologies. In the present study, we report on the occurrence of astrogliosis, microglial activation, and their relationship with age and AD-like pathology in a cohort of male and female chimpanzees (Pan troglodytes). Chimpanzees with severe astrogliosis exhibited widespread upregulation of hypertrophic astrocytes immunoreactive for glial fibrillary acidic protein (GFAP) throughout all layers of the dorsolateral prefrontal cortex and a loss of the interlaminar palisade. In addition, extreme astrogliosis was associated with increased astrocyte density in the absence of significant microglial activation and AD lesions. A shift from decreased resting to increased phagocytotic microglia occurred with aging, although proliferation was absent and no changes in astrogliosis was observed. Vascular amyloid correlated with decreased astrocyte and microglia densities, while tau lesions were associated with morphological changes in microglia and greater total glia density and glia: neuron ratio. These results further our understanding of inflammatory processes within the chimpanzee brain and provide comparative data to improve our understanding of human aging and neuropathological processes.

Role Of Retroelements In The Development Of COVID-19 Neurological Consequences

Retroelements play a key role in brain functioning in humans and other animals, since they represent dynamic regulatory elements controlling the expression of specific neuron types. The activity of retroelements in the brain is impaired under the influence of SARS-CoV-2, penetrating the blood-brain barrier. We propose a new concept, according to which the neurological complications of COVID-19 and their long-term effects are caused by modified expression of retroelements in neurons due to viral effect. This effect is implemented in several ways: a direct effect of the virus on the promoter regions of retroelement-encoding genes, virus interaction with miRNAs causing silencing of transposons, and an effect of the viral RNA on the products of retroelement transcription. Aging-related physiological activation of retroelements in the elderly is responsible for more severe course of COVID-19. The associations of multiple sclerosis, Parkinson’s disease, Guillain-Barré syndrome, acute disseminated encephalomyelitis with coronavirus lesions also indicate the role of retroelements in such complications, because retroelements are involved in the mechanisms of the development of these diseases. According to meta-analyses, COVID-19-caused neurological complications ranged 36.4-73%. The neuropsychiatric consequences of COVID-19 are observed in patients over a long period after recovery, and their prevalence may exceed those during the acute phase of the disease. Even 12 months after recovery, unmotivated fatigue, headache, mental disorders, and neurocognitive impairment were observed in 82%, 60%, 26.2-45%, and 16.2-46.8% of patients, correspondingly. These manifestations are explained by the role of retroelements in the integration of SARS-CoV-2 into the human genome using their reverse transcriptase and endonuclease, which results in a long-term viral persistence. The research on the role of specific retroelements in these changes can become the basis for developing targeted therapy for neurological consequences of COVID-19 using miRNAs, since epigenetic changes in the functioning of the genome in neurons, affected by transposons, are reversible.

Neurological and neuropsychological adverse effects of SARS-CoV-2 vaccines - where do we stand?

The devastating characteristic of COVID-19 pandemic calls for immediate and effective solutions to tackle it. Vaccines seem to be the only promising and effective way to fight against the novel coronavirus - even against new mutated variants. Because of the rapid development and distribution of numerous COVID-19 vaccines in different platforms, meticulous evaluation of vaccines' safety is more critical than ever - especially given the fact that most of the candidates have not completed the clinical phase. Therefore, to optimize the vaccines' safety and efficacy, it is highly important to carefully report and scientifically discuss the serious adverse effects following vaccination. In this respect, we discuss different neurological and neuropsychological adverse effects of COVID-19 vaccines including demyelinating diseases, Bell's palsy (BP), cerebrovascular complications, seizures, functional neurological disorders (FNDs), and some other rare adverse events, and hypothetical mechanisms which can lead to the reported side effects. Given the fact that the incidence of such events are rare and most of them are treatable, the current review aims to shed light on how much the relationship between COVID-19 vaccines and these complications can be reliable and provide an insight for future studies with much more meticulous methodologies to discuss the possible correlational or causal relationship between these complications and COVID-19 vaccines and elucidate whether or not the neurological side effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines can count as a considerable threat to public health.

Streptococcus equi subsp. zooepidemicus finding in confirmed feline infectious peritonitis cat patient

BACKGROUND

Feline infectious peritonitis (FIP) is a fatal immune-mediated disease in cat, caused by mutated feline coronavirus (FCoV). Due to its difficulties in diagnosis, FIP is sometimes underdiagnosed. Therefore, several laboratory procedures were performed to gain high index suspicion of FIP. However, through several laboratory findings, not only FIP but also SEZ infection was confirmed in this case.

CASE DESCRIPTION

A-year-old male, domestic cat was admitted to Veterinary Medicine Clinical Pathology Laboratory, Universitas Gadjah Mada, for further effusion examination due to its high suspicion of feline infectious peritonitis (FIP). Further examination using molecular and post-mortem analysis resulted on confirmed SEZ infection and FIP. This study informed the manifestation and pathological changes in patient with SEZ and FIP in the same time.

CONCLUSIONS

This study showed that viral infection followed by bacterial infection could be fatal and untreatable. After these findings, clinicians may consider SEZ infection in cat with respiratory disorder followed by thoracic effusion besides FIP. Companion animal, especially outdoor-kept animal, possibly become infected from its contact to another human or animal in the environment.

Therapeutic approaches to coronavirus infection according to "One Health" concept

Coronaviridae constantly infect human and animals causing respiratory, gastroenteric or systemic diseases. Over time, these viruses have shown a marked ability to mutate, jumping over the human-animal barrier, thus becoming from enzootic to zoonotic. In the last years, numerous therapeutic protocols have been developed, mainly for severe acute respiratory syndromes in humans. The aim of this review is to summarize drugs or other approaches used in coronavirus infections focusing on different roles of these molecules or bacterial products on viral adhesion and replication or in modulating the host's immune system. Within the "One Health" concept, the study of viral pathogenic role and possible therapeutic approaches in both humans and animals is essential to protect public health.

Diagnostic Value of Detecting Feline Coronavirus RNA and Spike Gene Mutations in Cerebrospinal Fluid to Confirm Feline Infectious Peritonitis

BACKGROUND

Cats with neurologic feline infectious peritonitis (FIP) are difficult to diagnose. Aim of this study was to evaluate the diagnostic value of detecting feline coronavirus (FCoV) RNA and spike (S) gene mutations in cerebrospinal fluid (CSF).

METHODS

The study included 30 cats with confirmed FIP (six with neurological signs) and 29 control cats (eleven with neurological signs) with other diseases resulting in similar clinical signs. CSF was tested for FCoV RNA by 7b-RT-qPCR in all cats. In RT-qPCR-positive cases, S-RT-qPCR was additionally performed to identify spike gene mutations.

RESULTS

Nine cats with FIP (9/30, 30%), but none of the control cats were positive for FCoV RNA in CSF. Sensitivity of 7b-RT-qPCR in CSF was higher for cats with neurological FIP (83.3%; 95% confidence interval (95% CI) 41.8-98.9) than for cats with non-neurological FIP (16.7%; 95% CI 6.1-36.5). Spike gene mutations were rarely detected.

CONCLUSIONS

FCoV RNA was frequently present in CSF of cats with neurological FIP, but only rarely in cats with non-neurological FIP. Screening for spike gene mutations did not enhance specificity in this patient group. Larger populations of cats with neurological FIP should be explored in future studies.

Safety and Efficacy of Felid Herpesvirus-1 Deletion Mutants in Cats

Felid herpesvirus-1 (FeHV-1) is an important respiratory and ocular pathogen of cats and current vaccines are limited in duration and efficacy because they do not prevent infection, viral nasal shedding and latency. To address these shortcomings, we have constructed FeHV-1 gE-TK- and FeHV-1 PK- deletion mutants (gE-TK- and PK-) using bacterial artificial chromosome (BAC) mutagenesis and shown safety and immunogenicity in vitro. Here, we compare the safety and efficacy of a prime boost FeHV-1 gE-TK- and FeHV-1 PK- vaccination regimen with commercial vaccination in cats. Cats in the vaccination groups were vaccinated at 3-week intervals and all cats were challenge infected 3 weeks after the last vaccination. Evaluations included clinical signs, nasal shedding, virus neutralizing antibodies (VN), cytokine mRNA gene expression, post-mortem histology and detection of latency establishment. Vaccination with gE-TK- and PK- mutants was safe and resulted in significantly reduced clinical disease scores, pathological changes, viral nasal shedding, and viral DNA in the trigeminal ganglia (the site of latency) following infection. Both mutants induced VN antibodies and interferons after immunization. In addition, after challenge infection, we observed a reduction of IL-1β expression, and modulation of TNFα, TGFβ and IL10 expression. In conclusion, this study shows the merits of using FeHV-1 deletion mutants for prevention of FeHV-1 infection in cats.

Lifting the mask on neurological manifestations of COVID-19

As the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic spreads, it is becoming increasingly evident that coronavirus disease 2019 (COVID-19) is not limited to the respiratory system, and that other organs can be affected. In particular, virus-related neurological manifestations are being reported more and more frequently in the scientific literature. In this article, we review the literature on the association between COVID-19 and neurological manifestations, present evidence from preclinical research suggesting that SARS-CoV-2 could be responsible for many of these manifestations, and summarize the biological pathways that could underlie each neurological symptom. Understanding the mechanisms that lead to neurological manifestations in patients with COVID-19 and how these manifestations correlate with clinical outcomes will be instrumental in guiding the optimal use of targeted therapeutic strategies.

Coronavirus Infection of the Central Nervous System: Animal Models in the Time of COVID-19

Naturally occurring coronaviral infections have been studied for several decades in the context of companion and production animals, and central nervous system involvement is a common finding, particularly in cats with feline infectious peritonitis (FIP). These companion and production animal coronaviruses have many similarities to recent human pandemic-associated coronaviruses such as SARS-CoV, MERS-CoV, and SARS-CoV2 (COVID-19). Neurological involvement is being increasingly recognized as an important clinical presentation in human COVID-19 patients, often associated with para-infectious processes, and potentially with direct infection within the CNS. Recent breakthroughs in the treatment of coronaviral infections in cats, including neurological FIP, have utilized antiviral drugs similar to those currently in human COVID-19 clinical trials. Differences in specific coronavirus and host factors are reflected in major variations in incidence and mechanisms of CNS coronaviral infection and pathology between species; however, broad lessons relating to treatment of coronavirus infection present within the CNS may be informative across species.

Neurological Damage by Coronaviruses: A Catastrophe in the Queue!

Neurological disorders caused by neuroviral infections are an obvious pathogenic manifestation. However, non-neurotropic viruses or peripheral viral infections pose a considerable challenge as their neuropathological manifestations do not emerge because of primary infection. Their secondary or bystander pathologies develop much later, like a syndrome, during and after the recovery of patients from the primary disease. Massive inflammation caused by peripheral viral infections can trigger multiple neurological anomalies. These neurological damages may range from a general cognitive and motor dysfunction up to a wide spectrum of CNS anomalies, such as Acute Necrotizing Hemorrhagic Encephalopathy, Guillain-Barré syndrome, Encephalitis, Meningitis, anxiety, and other audio-visual disabilities. Peripheral viruses like Measles virus, Enteroviruses, Influenza viruses (HIN1 series), SARS-CoV-1, MERS-CoV, and, recently, SARS-CoV-2 are reported to cause various neurological manifestations in patients and are proven to be neuropathogenic even in cellular and animal model systems. This review presents a comprehensive picture of CNS susceptibilities toward these peripheral viral infections and explains some common underlying themes of their neuropathology in the human brain.

How SARS-Cov-2 can involve the central nervous system. A systematic analysis of literature of the department of human neurosciences of Sapienza University, Italy

Italy is currently one of the countries most affected by the global emergency of COVID-19, a lethal disease of a novel coronavirus renamed as SARS-CoV-2. SARS-CoV-2 shares highly homological sequence with the most studied SARS-CoV, and causes acute, highly deadly pneumonia (COVID-19) with clinical symptoms similar to those reported for SARS-CoV and MERS-CoV. Increasing evidence shows that these coronaviruses are not always confined to the respiratory tract and that they may also neuroinvasive and neurotropic, with potential neuropathological consequences in vulnerable populations. The aim of this study is to predict a likely CNS involvement by SARS-CoV-2 by studying the pathogenic mechanisms in common with other better known and studied coronaviruses with which it shares the same characteristics. Understanding the mechanisms of neuroinvasion and interaction of HCoV (including SARS-Cov-2) with the CNS is essential to evaluate potentially pathological short- and long-term consequences. Autopsies of the COVID-19 patients, detailed neurological investigation, and attempts to isolate SARS-CoV-2 from the endothelium of cerebral microcirculation, cerebrospinal fluid, glial cells, and neuronal tissue can clarify the role played by COVID-19 in CNS-involvement and in the ongoing mortalities as has been in the recent outbreak.

Central nervous system involvement by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)

Neurologic sequelae can be devastating complications of respiratory viral infections. We report the presence of virus in neural and capillary endothelial cells in frontal lobe tissue obtained at postmortem examination from a patient infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Our observations of virus in neural tissue, in conjunction with clinical correlates of worsening neurologic symptoms, pave the way to a closer understanding of the pathogenic mechanisms underlying central nervous system involvement by SARS-CoV-2.

SARS-CoV-2 Infection Leads to Neurological Dysfunction

A number of neurological disease complications have been seen following infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While most person with COVID-19 respiratory disease demonstrate headache, nausea and vomiting, up to 40% present also experience dizziness, confusion, cerebrovascular disease, muscle pain, ataxia and seizures. Loss of taste and smell, defects in visual acuity and pain occur in parallel. Such central nervous system (CNS) signs and symptoms linked to laboratory-confirmed SARS-CoV-2 infection is often life threatening. Health care providers currently evaluating patients with neurologic symptoms need consider COVID-19 in any differential diagnosis. These considerations will facilitate prompt testing, isolation and prevention of viral transmission speeding best clinical outcomes.

Human Coronaviruses and Other Respiratory Viruses: Underestimated Opportunistic Pathogens of the Central Nervous System?

Respiratory viruses infect the human upper respiratory tract, mostly causing mild diseases. However, in vulnerable populations, such as newborns, infants, the elderly and immune-compromised individuals, these opportunistic pathogens can also affect the lower respiratory tract, causing a more severe disease (e.g., pneumonia). Respiratory viruses can also exacerbate asthma and lead to various types of respiratory distress syndromes. Furthermore, as they can adapt fast and cross the species barrier, some of these pathogens, like influenza A and SARS-CoV, have occasionally caused epidemics or pandemics, and were associated with more serious clinical diseases and even mortality. For a few decades now, data reported in the scientific literature has also demonstrated that several respiratory viruses have neuroinvasive capacities, since they can spread from the respiratory tract to the central nervous system (CNS). Viruses infecting human CNS cells could then cause different types of encephalopathy, including encephalitis, and long-term neurological diseases. Like other well-recognized neuroinvasive human viruses, respiratory viruses may damage the CNS as a result of misdirected host immune responses that could be associated with autoimmunity in susceptible individuals (virus-induced neuro-immunopathology) and/or viral replication, which directly causes damage to CNS cells (virus-induced neuropathology). The etiological agent of several neurological disorders remains unidentified. Opportunistic human respiratory pathogens could be associated with the triggering or the exacerbation of these disorders whose etiology remains poorly understood. Herein, we present a global portrait of some of the most prevalent or emerging human respiratory viruses that have been associated with possible pathogenic processes in CNS infection, with a special emphasis on human coronaviruses.

A retrospective study of the neuropathology and diagnosis of naturally occurring feline infectious peritonitis

Feline infectious peritonitis (FIP) is one of the most important viral diseases of cats worldwide. Our study describes the neuropathology and the diagnostic features of 26 cases of FIP in domestic cats. The average age of affected individuals was 11.8 mo, and there was no sex or breed predisposition. Clinical neurologic signs were noted in 22 cases, and rabies was clinically suspected in 11 cases. Twenty cats had lesions in multiple organs, and 6 cats had lesions only in the brain. Gross neuropathologic changes occurred in 15 cases and consisted of hydrocephalus (10 cases), cerebellar herniation through the foramen magnum (6 cases), cerebral swelling with flattening of gyri (2 cases), and accumulation of fibrin within ventricles (2 cases) or leptomeninges (1 case). Histologically, 3 main distinct distributions of neuropathologic changes were observed, namely periventricular encephalitis (12 cases), rhombencephalitis (8 cases), and diffuse leptomeningitis with superficial encephalitis (6 cases). Fresh tissue samples were submitted for fluorescent antibody testing (FAT) after autopsy in 17 cases, and positive results were found in only 7 cases. Immunohistochemistry (IHC) for feline coronavirus confirmed the diagnosis in all 26 cases. IHC appears to be a more sensitive and reliable test for confirmation of FIP than is FAT.

Expression profiles of immune mediators in feline Coronavirus-infected cells and clinical samples of feline Coronavirus-positive cats

Background

There are two biotypes of feline coronavirus (FCoV): the self-limiting feline enteric coronavirus (FECV) and the feline infectious peritonitis virus (FIPV), which causes feline infectious peritonitis (FIP), a fatal disease associated with cats living in multi-cat environments. This study provides an insight on the various immune mediators detected in FCoV-positive cats which may be responsible for the development of FIP.

Results

In this study, using real-time PCR and multiplex bead-based immunoassay, the expression profiles of several immune mediators were examined in Crandell-Reese feline kidney (CRFK) cells infected with the feline coronavirus (FCoV) strain FIPV 79–1146 and in samples obtained from FCoV-positive cats. CRFK cells infected with FIPV 79–1146 showed an increase in the expression of interferon-related genes and pro-inflammatory cytokines such as MX1, viperin, CXCL10, CCL8, RANTES, KC, MCP1, and IL8. In addition, an increase in the expression of the above cytokines as well as GM-CSF and IFNγ was also detected in the PBMC, serum, and peritoneal effusions of FCoV-positive cats. Although the expression of MX1 and viperin genes was variable between cats, the expression of these two genes was relatively higher in cats having peritoneal effusion compared to cats without clinically obvious effusion. Higher viral load was also detected in the supernatant of peritoneal effusions compared to in the plasma of FCoV-positive cats. As expected, the secretion of IL1β, IL6 and TNFα was readily detected in the supernatant of peritoneal effusions of the FCoV-positive cats.

Conclusions

This study has identified various pro-inflammatory cytokines and interferon-related genes such as MX1, viperin, CXCL10, CCL8, RANTES, KC, MCP1, IL8, GM-CSF and IFNγ in FCoV-positive cats. With the exception of MX1 and viperin, no distinct pattern of immune mediators was observed that distinguished between FCoV-positive cats with and without peritoneal effusion. Further studies based on definitive diagnosis of FIP need to be performed to confirm the clinical importance of this study.

Glial response in the central nervous system of cats with feline infectious peritonitis

OBJECTIVES

The aim of the study was to evaluate central nervous system (CNS) lesions in non-effusive and effusive cases of feline infectious peritonitis (FIP) regarding aspects related to astrocytic and microglial reactions.

METHODS

Five necropsied cats that were naturally infected with FIP virus, confirmed by reverse transcriptase polymerase chain reaction and immunohistochemistry, with different intensities of CNS lesions, were studied. Brain and cerebellum were evaluated by light microscopy and immunohistochemistry for glial fibrillary acidic protein (GFAP) and vimentin to assess astrocytic morphology, and lectin histochemistry for Ricinus communis agglutinin-I (RCA-I) to detect microglia was performed to evaluate the glial response in the CNS of cats with FIP.

RESULTS

An important astrocytic response in many areas of the CNS of all cats, including the periventricular areas of lateral ventricles and fourth ventricle, the molecular layer of the cerebellum and cerebral cortex, was visualized. This astrocytic reactivity was associated with areas of granulomatous or pyogranulomatous vasculitis/perivasculitis in most cases, and it was characterized by multifocal to coalescing astrocytosis and astrogliosis with an increase in the expression of intermediate filaments, such as GFAP. However, astrocytes exhibited strong vimentin expression in neuroparenchyma with severe inflammatory and necrotic changes, but GFAP expression was mild or absent in these cases. A microglial response was present only in severe lesions, and RCA-I expression was detected primarily in gitter cells and resting microglia.

CONCLUSIONS AND RELEVANCE

The present study indicates a strong astrocytic response, including the presence of many less differentiated vimentin-positive astrocytes and gitter cells positive for RCA-1 in severe lesions in the CNS of cats with FIP.

Use of a feline respiratory epithelial cell culture system grown at the air-liquid interface to characterize the innate immune response following feline herpesvirus 1 infection

Infection with feline herpesvirus-1 (FHV-1) accounts for 50% of viral upper respiratory diseases in domestic cats and is a significant cause of ocular diseases. Despite the clinical significance and high prevalence of FHV-1 infection, currently available vaccines cannot completely protect cats from infection and lifelong latency. FHV-1 infects via the mucous membranes and replicates in respiratory epithelial cells, but very little is known about the early innate immunity at this site. To address questions about immunity to FHV-1, feline respiratory epithelial cells cultured at air-liquid interface (ALI-FRECs) were established by collecting respiratory tracts from 6 healthy cats after euthanasia. Cells were isolated, cultured and characterized histologically and immunologically before infection with FHV-1. The expression of Toll-like receptors (TLRs), cytokine and chemokine responses were measured by real time PCR. ALI-FRECs morphologically resembled the natural airways of cats with multilayered columnar epithelial cells and cilia. Immunological properties of the natural airways were maintained in ALI-FRECs, as evidenced by the expression of TLRs, cytokines, chemokines, interferons, beta-defensins, and other regulatory genes. Furthermore, ALI-FRECs were able to support infection and replication of FHV-1, as well as modulate transcriptional regulation of various immune genes in response to infection. IL-1β and TNFα were increased in ALI-FRECs by 24hpi, whereas expression levels of IFN-α and TLR9 were not increased until 36hpi. In contrast, TLR3, GM-CSF and TGF-1β expression was down-regulated at 36hpi. The data presented show the development of a system ideal for investigating the molecular pathogenesis and immunity of FHV-1 or other respiratory pathogens.

Feline infectious peritonitis: still an enigma?

Feline infectious peritonitis (FIP) is one of the most important fatal infectious diseases of cats, the pathogenesis of which has not yet been fully revealed. The present review focuses on the biology of feline coronavirus (FCoV) infection and the pathogenesis and pathological features of FIP. Recent studies have revealed functions of many viral proteins, differing receptor specificity for type I and type II FCoV, and genomic differences between feline enteric coronaviruses (FECVs) and FIP viruses (FIPVs). FECV and FIP also exhibit functional differences, since FECVs replicate mainly in intestinal epithelium and are shed in feces, and FIPVs replicate efficiently in monocytes and induce systemic disease. Thus, key events in the pathogenesis of FIP are systemic infection with FIPV, effective and sustainable viral replication in monocytes, and activation of infected monocytes. The host's genetics and immune system also play important roles. It is the activation of monocytes and macrophages that directly leads to the pathologic features of FIP, including vasculitis, body cavity effusions, and fibrinous and granulomatous inflammatory lesions. Advances have been made in the clinical diagnosis of FIP, based on the clinical pathologic findings, serologic testing, and detection of virus using molecular (polymerase chain reaction) or antibody-based methods. Nevertheless, the clinical diagnosis remains challenging in particular in the dry form of FIP, which is partly due to the incomplete understanding of infection biology and pathogenesis in FIP. So, while much progress has been made, many aspects of FIP pathogenesis still remain an enigma.

Human coronaviruses: viral and cellular factors involved in neuroinvasiveness and neuropathogenesis

•

Human coronavirus (HCoV) are naturally neuroinvasive in both mice and humans.

•

Both transneuronal and hematogenous route may allow virus invasion of the CNS.

•

Infection of neurons leads to excitotoxicity, neurodegeneration and cell-death.

•

HCoV are potentially associated with human neurological disorders.

Among the various respiratory viruses infecting human beings, coronaviruses are important pathogens, which usually infect the upper respiratory tract, where they are mainly associated with common colds. However, in more vulnerable populations, such as newborns, infants, the elderly and immune-compromised individuals, these opportunistic pathogens can also affect the lower respiratory tract, leading to pneumonia, exacerbations of asthma, and various types of respiratory distress syndrome. The respiratory involvement of human coronaviruses has been clearly established since the 1960s. Nevertheless, for almost three decades now, data reported in the scientific literature has also demonstrated that, like it was described for other human viruses, coronaviruses have neuroinvasive capacities since they can spread from the respiratory tract to the central nervous system (CNS). Once there, infection of CNS cells (neurotropism) could lead to human health problems, such as encephalitis and long-term neurological diseases. Neuroinvasive coronaviruses could damage the CNS as a result of misdirected host immune responses that could be associated with autoimmunity in susceptible individuals (virus-induced neuroimmunopathology) and/or viral replication, which directly induces damage to CNS cells (virus-induced neuropathology). Given all these properties, it has been suggested that these opportunistic human respiratory pathogens could be associated with the triggering or the exacerbation of neurologic diseases for which the etiology remains poorly understood. Herein, we present host and viral factors that participate in the regulation of the possible pathogenic processes associated with CNS infection by human coronaviruses and we try to decipher the intricate interplay between virus and host target cells in order to characterize their role in the virus life cycle as well as in the capacity of the cell to respond to viral invasion.

Neuroinvasive and neurotropic human respiratory coronaviruses: potential neurovirulent agents in humans

In humans, viral infections of the respiratory tract are a leading cause of morbidity and mortality worldwide. Several recognized respiratory viral agents have a neuroinvasive capacity since they can spread from the respiratory tract to the central nervous system (CNS). Once there, infection of CNS cells (neurotropism) could lead to human health problems, such as encephalitis and long-term neurological diseases. Among the various respiratory viruses, coronaviruses are important pathogens of humans and animals. Human Coronaviruses (HCoV) usually infect the upper respiratory tract, where they are mainly associated with common colds. However, in more vulnerable populations, such as newborns, infants, the elderly, and immune-compromised individuals, they can also affect the lower respiratory tract, leading to pneumonia, exacerbations of asthma, respiratory distress syndrome, or even severe acute respiratory syndrome (SARS). The respiratory involvement of HCoV has been clearly established since the 1960s. In addition, for almost three decades now, the scientific literature has also demonstrated that HCoV are neuroinvasive and neurotropic and could induce an overactivation of the immune system, in part by participating in the activation of autoreactive immune cells that could be associated with autoimmunity in susceptible individuals. Furthermore, it was shown that in the murine CNS, neurons are the main target of infection, which causes these essential cells to undergo degeneration and eventually die by some form of programmed cell death after virus infection. Moreover, it appears that the viral surface glycoprotein (S) represents an important factor in the neurodegenerative process. Given all these properties, it has been suggested that these recognized human respiratory pathogens could be associated with the triggering or the exacerbation of neurological diseases for which the etiology remains unknown or poorly understood.

Establishment of a rat model for canine necrotizing meningoencephalitis (NME)

The pathogenesis of necrotizing meningoencephalitis (NME), necrotizing leukoencephalitis (NLE), and granulomatous meningoencephalomyelitis (GME) is still uncertain, although they are considered immune-mediated diseases. The purpose of the present study is to generate a rodent model(s) of these diseases. Rats were injected with rat cerebral or cerebellar homogenate. Rats injected with cerebral homogenate (Cbr) exhibited vacuolar or malacic changes mainly in the cerebral cortex. CD3-positive T cells and Iba-1-positive and CD163-negative microglia infiltrated and activated around the lesions. IgG deposited in the glial fibrillary acid protein (GFAP)-positive glia limitans from the early phase, and CD3-positive T cells attached to GFAP-positive astrocytes. Autoantibodies against GFAP were detected in the sera. These pathological features of Cbr rats were consistent with those of canine NME. In contrast, rats injected with cerebral homogenate (Cbe) exhibited demyelinating lesions with inflammatory reactions in the cerebellum, brainstem, and spinal cord. The presence of demyelination and autoantibodies against myelin proteins in Cbe rats was similar to murine experimental autoimmune encephalitis and differed from NME, NLE, and GME. All the present findings indicate that autoantibodies together with microglia and T cells may play a major role in the pathogenesis of idiopathic canine meningoencephalomyelitis.

The paradox of feline coronavirus pathogenesis: a review

Feline coronavirus (FCoV) is an enveloped single-stranded RNA virus, of the family Coronaviridae and the order Nidovirales. FCoV is an important pathogen of wild and domestic cats and can cause a mild or apparently symptomless enteric infection, especially in kittens. FCoV is also associated with a lethal, systemic disease known as feline infectious peritonitis (FIP). Although the precise cause of FIP pathogenesis remains unclear, some hypotheses have been suggested. In this review we present results from different FCoV studies and attempt to elucidate existing theories on the pathogenesis of FCoV infection.

Immunomodulator expression in trophoblasts from the feline immunodeficiency virus (FIV)-infected cat

Background

FIV infection frequently compromises pregnancy under experimental conditions and is accompanied by aberrant expression of some placental cytokines. Trophoblasts produce numerous immunomodulators that play a role in placental development and pregnancy maintenance. We hypothesized that FIV infection may cause dysregulation of trophoblast immunomodulator expression, and aberrant expression of these molecules may potentiate inflammation and compromise pregnancy. The purpose of this project was to evaluate the expression of representative pro-(TNF-α, IFN-γ, IL-1β, IL-2, IL-6, IL-12p35, IL-12p40, IL-18, and GM-CSF) and anti-inflammatory cytokines (IL-4, IL-5, and IL-10); CD134, a secondary co-stimulatory molecule expressed on activated T cells (FIV primary receptor); the chemokine receptor CXCR4 (FIV co-receptor); SDF-1α, the chemokine ligand to CXCR4; and FIV gag in trophoblasts from early-and late-term pregnancy.

Methods

We used an anti-cytokeratin antibody in immunohistochemistry to identify trophoblasts selectively, collected these cells using laser capture microdissection, and extracted total RNA from the captured cell populations. Real time, reverse transcription-PCR was used to quantify gene expression.

Results

We detected IL-4, IL-5, IL-6, IL-1β, IL-12p35, IL-12p40, and CXCR4 in trophoblasts from early-and late-term pregnancy. Expression of cytokines increased from early to late pregnancy in normal tissues. A clear, pro-inflammatory microenvironment was not evident in trophoblasts from FIV-infected queens at either stage of pregnancy. Reproductive failure was accompanied by down-regulation of both pro-and anti-inflammatory cytokines. CD134 was not detected in trophoblasts, and FIV gag was detected in only one of ten trophoblast specimens collected from FIV-infected queens.

Conclusion

Feline trophoblasts express an array of pro-and anti-inflammatory immunomodulators whose expression increases from early to late pregnancy in normal tissues. Non-viable pregnancies were associated with decreased expression of immunomodulators which regulate trophoblast invasion in other species. The detection of FIV RNA in trophoblasts was rare, suggesting that the high rate of reproductive failure in FIV-infected queens was not a direct result of viral replication in trophoblasts. The influence of placental immune cells on trophoblast function and pregnancy maintenance in the FIV-infected cat requires additional study.

Production of IFN-γ in feline whole blood after incubation with potential T-cell epitopes of the nucleocapsid protein of feline coronavirus

Interferon gamma (IFN-γ) plays an important role in cell mediated responses against mutated feline coronavirus strains (FCoV) involved in the pathogenesis of feline infectious peritonitis (FIP). The aim of this study was to establish a combined in silico and in vitro approach to assess feline leukocyte production of IFN-γ in response to selected peptides of the nucleocapside protein (N) of FCoVs.

To this aim, we designed, through a bioinformatic approach, 8 potentially immunogenic peptides from the protein N corresponding to sequences of residues 14, 182, 198 detected only in FCoVs from FIP cats (virulent strains), only in FCoVs from healthy cats (avirulent strains) and both in FIP and in healthy cats (mixed strains).

The peptides or a sham solution were incubated with whole blood from 16 cats (7 healthy and 9 with chronic diseases other than FIP) and IFN-γ concentration was measured on plasma using an ELISA system. RT-PCR expression of IFN-γ mRNA was also evaluated after incubation of the peptides or a sham solution with whole blood from 4 clinically healthy cats.

The mean plasma concentration of IFN-γ in samples incubated with peptides decreased and the expression of IFN-γmRNA did not change compared with the sham solution, except for some cats with chronic diseases (which probably have a “pre-activated” immune response). These cats responded to “avirulent” or “mixed” peptides by increasing the concentration of IFN-γ and the expression of IFN-γ mRNA.

The combined approach employed in this study allowed us to identify potentially immunogenic peptides of FCoV N protein that can modulate the production of IFN-γ especially in cats with a “pre-activated” cell mediated response.

Expression of receptor tyrosine kinases VEGFR-1 (FLT-1), VEGFR-2 (KDR), EGFR-1, PDGFRalpha and c-Met in canine primary brain tumours

Inhibition of tumour growth and angiogenesis by targeting key growth factor receptors is a promising therapeutic strategy for central nervous system tumours. Characterization of these growth factor receptors in canine primary brain tumours has not been done. Using quantitative real-time TaqMan polymerase chain reaction (PCR), we evaluated the expression of messenger RNA (mRNA) for five tyrosine kinase growth factor receptors (vascular endothelial growth factor receptor [VEGFR]-1, VEGFR-2, endothelial growth factor receptor [EGFR]-1, platelet-derived growth factor receptor a [PDGFRa], and c-Met) relative to normal cerebral cortex in 66 spontaneous canine primary brain tumours. Increased expression of VEGFR-1 and VEGFR-2 mRNA was greatest in grade IV astrocytomas (glioblastoma multiforme) and grade III (anaplastic) oligodendrogliomas. EGFR-1 mRNA expression was more consistently increased than the other receptors in all tumour types, while increased PDGFRa mRNA expression was mostly restricted to oligodendrogliomas. The similarities in increased expression of these tyrosine kinase growth factor receptors in these canine tumours, as compared to data from their human counterparts, suggest that common molecular mechanisms may be present.

Feline infectious peritonitis. ABCD guidelines on prevention and management

OVERVIEW

Feline coronavirus infection is ubiquitous in domestic cats, and is particularly common where conditions are crowded. While most FCoV-infected cats are healthy or display only a mild enteritis, some go on to develop feline infectious peritonitis, a disease that is especially common in young cats and multi-cat environments. Up to 12% of FCoV-infected cats may succumb to FIP, with stress predisposing to the development of disease.

DISEASE SIGNS

The 'wet' or effusive form, characterised by polyserositis (abdominal and/or thoracic effusion) and vasculitis, and the 'dry' or non-effusive form (pyogranulomatous lesions in organs) reflect clinical extremes of a continuum. The clinical picture of FIP is highly variable, depending on the distribution of the vasculitis and pyogranulomatous lesions. Fever refractory to antibiotics, lethargy, anorexia and weight loss are common non-specific signs. Ascites is the most obvious manifestation of the effusive form.

DIAGNOSIS

The aetiological diagnosis of FIP ante-mortem may be difficult, if not impossible. The background of the cat, its history, the clinical signs, laboratory changes, antibody titres and effusion analysis should all be used to help in decision-making about further diagnostic procedures. At the time of writing, there is no non-invasive confirmatory test available for cats without effusion.

DISEASE MANAGEMENT

In most cases FIP is fatal. Supportive treatment is aimed at suppressing the inflammatory and detrimental immune response. However, there are no controlled studies to prove any beneficial effect of corticosteroids.

VACCINATION RECOMMENDATIONS

At present, only one (intranasal) FIP vaccine is available, which is considered as being non-core. Kittens may profit from vaccination when they have not been exposed to FCoV (eg, in an early-weaning programme), particularly if they enter a FCoV-endemic environment.

The cat with neurological manifestations of systemic disease. Key conditions impacting on the CNS

PRACTICAL RELEVANCE

A number of systemic diseases are associated with neurological deficits. Most systemic diseases that impact on the nervous system result in multifocal neurological signs; however, isolated deficits can also be observed. This article reviews the clinical signs, pathophysiology, diagnosis, treatment and prognosis of four important systemic diseases with neurological consequences: feline infectious peritonitis, toxoplasmosis, hypertension and hepatic encephalopathy.

CLINICAL CHALLENGES

Early recognition of systemic signs of illness in conjunction with neurological deficits will allow for prompt diagnosis and treatment. While neurological examination of the feline patient can undoubtedly be challenging, hopefully the accompanying articles in this special issue will enable the clinician to approach these cases with more confidence.

EVIDENCE BASE

The veterinary literature contains numerous reports detailing the impact of systemic disease on the nervous system. Unfortunately, very few references provide detailed descriptions of large cohorts of affected cats. This review summarises the literature underpinning the four key diseases under discussion.

Retrospective analysis of seizures associated with feline infectious peritonitis in cats

Seizures have been reported frequently in feline infectious peritonitis (FIP) but have not been studied in detail in association with this disease. The purpose of this study was to perform a retrospective analysis of neurological signs in a population of 55 cats with a histopathologically confirmed neurological form of FIP. Seizure patterns were determined and it was attempted to relate occurrence of seizures with age, breed, sex and neuropathological features. Fourteen cats had seizure(s), while 41 cats had no history of seizure(s). Generalised tonic–clonic seizures were seen in nine cats; and complex focal seizures were observed in four patients. The exact type of seizure could not be determined in one cat. Status epilepticus was observed in one patient but seizure clusters were not encountered. Occurrence of seizures was not related to age, sex, breed or intensity of the inflammation in the central nervous system. However, seizures were significantly more frequent in animals with marked extension of the inflammatory lesions to the forebrain (P = 0.038). Thus, the occurrence of seizures in FIP indicates extensive brain damage and can, therefore, be considered to be an unfavourable prognostic sign.

The feline acute phase reaction

The acute phase reaction (APR) is a response to potentially pathogenic stimuli. It begins with the release of interleukin (IL)-1, IL-6 and tumour necrosis factor (TNF)-α from inflammatory cells. These cytokines induce fever, leucocytosis and release of serum acute phase proteins (APPs). In this review, the characteristics of the feline APR are described. In cats with inflammatory conditions, fever is a common finding, with leucocytosis due to the release of cells from the marginal pool, followed by activation of myelopoiesis. Because excitement frequently causes leucocytosis in cats, a diagnosis of inflammation should therefore be supported by additional findings such as the presence of toxic neutrophils. The major APPs are serum amyloid A and α₁-acid glycoprotein (AGP), which both increase a few hours after the inflammatory stimulus and remain elevated for as long as the inflammation persists. AGP plays an important role in the diagnosis of feline infectious peritonitis (FIP) and may also be useful also in studies of FIP pathogenesis.

Whole blood cytokine profiles in cats infected by feline coronavirus and healthy non-FCoV infected specific pathogen-free cats

In this study, the cytokine profiles of clinically healthy cats naturally infected with feline coronavirus (FCoV), of cats with feline infectious peritonitis (FIP) and of specific pathogen-free (SPF) cats were investigated in whole blood using a traditional reverse-transcriptase polymerase chain reaction (RT-PCR) assay and a semi-quantitative method of analysis based on computerised quantification of positive bands. The low inter-assay coefficient of variation recorded demonstrated that this method is highly repeatable. Compared with SPF cats, cytokine production was upregulated in most of the samples from FCoV-positive non-symptomatic cats. The appearance of a case of FIP in the cattery was associated with an increased expression of cytokines, in particular there was an increased production of IL-1beta and IFN-gamma, suggesting that these cytokines might protect infected cats from the disease. This hypothesis was also supported by the low levels of IFN-gamma recorded in blood from cats with FIP.

Marek's Disease Virus–Induced Transient Paralysis Is Associated with Cytokine Gene Expression in the Nervous System

Marek's disease (MD)-associated transient paralysis (TP) was experimentally induced in chickens by intraperitoneal inoculation of RB1B strain of Marek's disease virus (MDV). Between 7 and 11 days post-infection (d.p.i.), neck and limb paralysis was observed in 18% of infected chickens, which was associated with various degrees of edema, vacuolation, perivascular cuffing of mononuclear cells, and glial cell infiltration mainly in the cerebrum, cerebellum, and brain stem. The chickens that were infected but did not progress to develop TP until 12 d.p.i. also had similar lesions suggestive of encephalitis in the cerebrum, cerebellum, and brain stem. Chickens infected with MDV had more interleukin (IL)-6, IL-12, and interferon (IFN)-gamma in their brain tissues compared to uninfected chickens. Moreover, IL-18 was significantly increased in brain tissues of birds showing clinical signs of TP compared to uninfected birds. Importantly, the expression of IL-6, IL-18, and IFN- gamma in brain tissues of MDV-infected chickens with signs of TP was significantly increased compared to that in asymptomatic MDV-infected birds. MDV genome load in the brain of chickens showing clinical signs of TP was higher than that in asymptomatic MDV-infected chickens but was not statistically significant. The lesions in the cervical, thoracic, and lumbar spinal cord segments in MDVinfected chickens were characterized mainly by perivascular cuffing of mononuclear cells irrespective of the group. The expression of mRNA for IL-18 and IFN-gamma genes was not significantly different in spinal cord tissues of chickens with TP compared to clinically normal, MDV-infected and noninfected chickens. These results suggest possible underlying immunologic mechanisms for MDV-induced TP.

Natural feline coronavirus infection: differences in cytokine patterns in association with the outcome of infection

Natural and experimental feline coronavirus (FCoV) infection leads to systemic viral spread via monocyte-associated viraemia and induces systemic proliferation of monocytes/macrophages. In the majority of naturally infected animals, FCoV infection remains subclinical and is associated with generalised B and T cell hyperplasia, but no other pathological findings. A minority of cats, however, develop feline infectious peritonitis (FIP), a fatal systemic granulomatous disease. This is generally accompanied by B and T cell depletion. The obvious functional differences of lymphatic tissues in FCoV-infected cats with and without FIP suggest that they contribute to the outcome of FCoV infection. This study attempted to evaluate the functional changes in haemolymphatic tissues after natural FCoV infection, with special emphasis on the magnitude, phenotype and function of the monocyte/macrophage population. The spleen, mesenteric lymph nodes and bone marrow from naturally FCoV-infected cats with and without FIP and specific pathogen-free (SPF) control cats were examined for the quantity and activation state of monocytes/macrophages both by immunohistology and by quantitative real time PCR for the transcription of interleukin (IL)-1β, IL-6, IL-10, IL-12 p40, tumour necrosis factor (TNF), granulocyte colony stimulating factor (G-CSF), macrophage-CSF (M-CSF) and GM-CSF. Compared to cats with FIP, FCoV-infected cats without FIP exhibited significantly higher IL-10 levels in the spleen and significantly lower levels of IL-6, G- and M-CSF in mesenteric lymph nodes. In cats with FIP, however, IL-12 p40 levels were significantly lower in lymphatic tissues in comparison to both SPF cats and FCoV-infected cats without FIP. In comparison to SPF cats, FIP cats had significantly higher IL-1β levels and lower TNF levels in mesenteric lymph nodes and lower M-CSF levels in the spleen. Findings indicate that FCoV-infected cats which do not develop FIP are able to mount an effective FCoV-specific immune response and can avoid excessive macrophage activation and FIP, possibly by upregulation of IL-10 production. Development of FIP, however, might be due to a lack of IL-12 which inhibits an effective cellular immune response and allows for monocyte/macrophage activation and the development of FIP.

Virulent systemic feline calicivirus infection: local cytokine modulation and contribution of viral mutants

Virulent systemic feline calicivirus (VS-FCV) is a novel, emerging pathogen with mortality up to 67% even in previously healthy adult cats; VS-FCV has resulted in at least six epidemics since 1998. Affected cats have systemic vascular compromise and hemorrhagic-fever like signs in part due to viral invasion of epithelium and endothelium, coupled with host cytokine responses. Affected skin tissues had, on average, 3.8 elevated cytokines compared with control tissue, with prominent upregulation in IL-10, TNF-alpha, and MIP-1alpha. Sequencing of most of the genomes of two VS-FCV strains documented patterns of virus relatedness and implicated changes in the capsid gene in the emerging phenotype, possibly through initiation of immune mechanisms manifest in the cytokine changes. Understanding the features contributing to the emergence of this disease is critical for management and prevention of this and similar outbreaks attributable to RNA viruses in animals and humans.

Immunopathogenesis of coronavirus infections: implications for SARS

The severe acute respiratory syndrome (SARS), which was first identified in 2003, is caused by a novel coronavirus: the SARS coronavirus (SARS-CoV).

Many features of the infection indicate that an excessive, but perhaps 'normal', immune response contributes to SARS.

Several coronaviruses cause diseases that result in considerable morbidity and mortality in animals. Some of these diseases are also immune mediated and provide insights into the pathogenesis of SARS.

Feline infectious peritonitis virus (FIPV) causes a fatal, immune-mediated disease of felines. Macrophage infection, lymphocyte depletion and antibody-dependent disease enhancement are hallmarks of this disease.

Infection with the murine coronavirus murine hepatitis virus (MHV) strain JHM results in immune-mediated demyelination. Similar to SARS, macrophage activation is a key component in the pathogenic process.

Another strain of MHV, MHV-3, causes a fatal, fulminant hepatitis. MHV-3 infection of macrophages, with subsequent activation and induction of expression of a novel procoagulant, fibrinogen-like protein 2 (FGL2), is required for severe disease.

Chickens that are infected with avian infectious bronchitis virus (IBV) develop respiratory and renal disease. An excessive innate immune response contributes to the pathogenic process in these animals.

To develop effective therapies for SARS will require understanding of the contributions of direct injury by virus and of the host immune response to pathogenesis. This requires further studies of the interactions of SARS-CoV with its target cells and necessitates the development of an animal model that reproduces the pulmonary infection that is observed in infected humans.

At the end of 2002, the first cases of severe acute respiratory syndrome (SARS) were reported, and in the following year, SARS resulted in considerable mortality and morbidity worldwide. SARS is caused by a novel species of coronavirus (SARS-CoV) and is the most severe coronavirus-mediated human disease that has been described so far. On the basis of similarities with other coronavirus infections, SARS might, in part, be immune mediated. As discussed in this Review, studies of animals that are infected with other coronaviruses indicate that excessive and sometimes dysregulated responses by macrophages and other pro-inflammatory cells might be particularly important in the pathogenesis of disease that is caused by infection with these viruses. It is hoped that lessons from such studies will help us to understand more about the pathogenesis of SARS in humans and to prevent or control outbreaks of SARS in the future.

Rush immunotherapy in an experimental model of feline allergic asthma

Specific allergen immunotherapy represents the only curative treatment of allergy. No studies have evaluated its efficacy in feline allergic asthma. We hypothesized that an abbreviated course of immunotherapy (rush immunotherapy, RIT) would blunt eosinophilic airways inflammation in experimental feline asthma induced with Bermuda grass allergen (BGA). The 6-month study included asthmatic-RIT treated cats; asthmatic-no RIT treated cats; and non-asthmatic cats. RIT involved increasing parenteral doses (20-200 microg) of BGA over 2 days. Numbers of eosinophils in bronchoalveolar lavage fluid (BALF), serum and BALF immunoglobulins, lymphocyte blastogenesis assays, and cytokines in blood and BALF were evaluated. BALF eosinophils decreased (P=0.048) only in asthmatic-RIT treated cats (baseline 1.1 x 10(6); Month 6, 2.4 x 10(5)). Serum BGA-specific IgG was higher (P<0.001) at all time points after baseline within the asthmatic-RIT group, and was higher (P<0.001) than asthmatic-no RIT cats at Months 1 and 3. No differences (P=0.133) in BGA-specific IgE levels over time were noted among asthmatic-RIT cats, but this group had lower IgE levels (P<0.001) levels than asthmatic no-RIT cats at Months 3 and 6. Differences in BGA-specific IgA levels over time and between the two groups did not reach the traditional level of significance. The mean BGA stimulation index in the asthmatic-RIT cats was biologically insignificant at 6 months, reflecting BGA-specific lymphocyte hypoproliferation. Preliminary results of cytokine profiles were not significantly different; however, BAL cytokine profiles favoring a Th2 response prior to RIT shifted to increased IFN-g and IL-10 thereafter. RIT dampens eosinophilic airways inflammation in cats with experimental asthma. The mechanism of RIT may involve changes in allergen-specific immunoglobulins, induction of hyporesponsive lymphocytes, or alteration of cytokine profiles.

Cellular composition and interferon-gamma expression of the local inflammatory response in feline infectious peritonitis (FIP)

Feline infectious peritonitis (FIP) is one of the most important viral diseases of cats. International studies estimate that approximately 80% of all purebred cats are infected with the causative agent, feline coronavirus (FCoV). Out of these, 5-12% develop clinical symptoms of FIP. The pathogenesis of the disease is complex with many unresolved issues relating to the role of the immune system. The aim of the present study was to determine the proportions of various inflammatory cell types in FIP lesions by using a panel of cat specific, thoroughly validated, monoclonal antibodies. In addition, the expression of interferon-gamma within the inflammatory lesions was examined by RT-PCR. Our results confirm the mixed nature of the inflammatory reaction in FIP, involving B cells and plasma cells as well as CD4+ and CD8+ T cells. However, one cell type stands out as being the key element in both the "wet" and "dry" forms of FIP: the macrophage. Upregulation of IFN-gamma expression within the inflammatory lesions suggests a local activation of macrophages, which might result in increased viral replication.

Cytokine gene transcription in feline nasal tissue with histologic evidence of inflammation

OBJECTIVE

To correlate gene transcription of cytokines and chemokines with histologic inflammation in nasal biopsy specimens of cats.

ANIMALS

25 study cats and 4 specific pathogen-free cats.

PROCEDURE

One nasal biopsy specimen from each cat was submitted for routine histologic evaluation; a second was submitted for evaluation by use of a quantitative real-time polymerase chain reaction analysis with a fluorogenic probe (ie, TaqMan) for detection of cytokines and chemokines (interleukin [IL]-4, IL-5, IL-6, IL-10, IL-12 p40, IL-16, IL-18, interferon [IFN]I-gamma, tumor necrosis factor [TNF]-alpha, and the regulated on activation normal T cell expressed and secreted [RANTES] protein). Specimens were grouped histologically by degree of inflammation (none, mild, moderate, or severe). Linearized TaqMan signals for each gene were compared among histologic groups.

RESULTS

Nasal biopsy specimens from specific pathogen-free cats were histologically normal, and cytokine transcription was low in these samples. As nasal inflammation in study cats worsened from absent (n = 3) to mild (4) to moderate (8) or severe (10), progressively and significantly increasing transcription of IL-6, IL-10, IL-12 p40, IFN-gamma, TNF-alpha, and the RANTES protein was detected. Transcription of IL-4, IL-5, IL-16, and IL-18 did not correlate with worsened histologic inflammation.

CONCLUSIONS AND CLINICAL RELEVANCE

Transcription of specific cytokines and chemokines in nasal tissue of cats progressively increased with severity of histologic evidence of inflammation, and IL-6, IL-10, IL-12 p40, IFN-gamma, TNF-alpha, and the RANTES protein were markers of inflammation. Our data suggest that the nasal cavity of cats is biased toward a Th1 cytokine profile that is augmented by inflammation.

Feline herpesvirus type-1 transcription is associated with increased nasal cytokine gene transcription in cats

The etiopathogenesis of chronic nasal discharge in the cat is poorly understood. The objective of this study was to investigate alterations in transcription of genes for cytokines and chemokines in association with feline herpesvirus-1 (FHV-1) mRNA transcription. Nasal samples from 21 cats were submitted for FHV-1 virus isolation (VI), traditional endpoint polymerase chain reaction (PCR) detection of FHV-1 DNA, and quantitative real-time TaqMan PCR analysis of cytokines and chemokines (interleukin [IL]-4, IL-5, IL-6, IL-10, IL-12p40, IL-16, IL-18, interferon [IFN]-gamma, tumor necrosis factor [TNF]-alpha, and regulated on activation normal T cell expressed and secreted protein [RANTES]) and of FHV-1 mRNA and DNA. Co-infection with feline calicivirus or Chlamydophila spp. was excluded in all cats. Gene transcription in nasal samples from four specific pathogen free (SPF) cats served as the calibrator for cytokines. FHV-1 was detected by VI in 14 of 21 samples, by traditional PCR in 18 of 21 samples, and by quantitative PCR in 13 (mRNA+) and 18 (DNA+) samples. Nasal samples from cats positive for FHV-1 mRNA displayed significantly increased transcription of IL-6, IL-10, IL-12p40, IL-18, IFN-gamma, TNF-alpha, and RANTES (P<0.05) in comparison to samples from cats negative for FHV-1 mRNA. The cycle threshold for FHV-1 DNA was significantly higher in cats with detectable FHV-1 mRNA (P<0.05). Increased transcription of cytokines/chemokines in cats with detectable mRNA for FHV-1 suggests a role for FHV-1 in nasal inflammation.

Feline infectious peritonitis

The article discusses feline infectious peritonitis (FIP), an important disease frequently seen in veterinary practice. FIP causes many problems to the veterinarian as it can be difficult to definitively diagnose the disease, as there is no effective treatment, and as prophylactic interventions are not very successful. Although intense research has created a lot of new knowledge about this disease in the last years, there are still many unanswered questions. The objective of this article is to review recent knowledge and to increase understanding of the complex pathogenesis of FIP.

Infectious diseases of the central nervous system

Neurologic disease is seen commonly in cats, with infectious causes accounting for 30-45% of cases. However, since a specific infection cannot be identified in 12-40% of these cases, it is essential that we try to understand these cases better in the hope that we can eventually identify the cause(s), and so determine how best to treat and/or prevent them.

An experimental model of allergic asthma in cats sensitized to house dust mite or bermuda grass allergen

BACKGROUND

Animal models are used to mimic human asthma, however, not all models replicate the major characteristics of the human disease. Spontaneous development of asthma with hallmark features similar to humans has been documented to occur with relative frequency in only one animal species, the cat. We hypothesized that we could develop an experimental model of feline asthma using clinically relevant aeroallergens identified from cases of naturally developing feline asthma, and characterize immunologic, physiologic, and pathologic changes over 1 year.

METHODS

House dust mite (HDMA) and Bermuda grass (BGA) allergen were selected by screening 10 privately owned pet cats with spontaneous asthma using a serum allergen-specific IgE ELISA. Parenteral sensitization and aerosol challenges were used to replicate the naturally developing disease in research cats. The asthmatic phenotype was characterized using intradermal skin testing, serum allergen-specific IgE ELISA, serum and bronchoalveolar lavage fluid (BALF) IgG and IgA ELISAs, airway hyperresponsiveness testing, BALF cytology, cytokine profiles using TaqMan PCR, and histopathologic evaluation.

RESULTS

Sensitization with HDMA or BGA in cats led to allergen-specific IgE production, allergen-specific serum and BALF IgG and IgA production, airway hyperreactivity, airway eosinophilia, an acute T helper 2 cytokine profile in peripheral blood mononuclear cells and BALF cells, and histologic evidence of airway remodeling.

CONCLUSIONS

Using clinically relevant aeroallergens to sensitize and challenge the cat provides an additional animal model to study the immunopathophysiologic mechanisms of allergic asthma. Chronic exposure to allergen in the cat leads to a variety of immunologic, physiologic, and pathologic changes that mimic the features seen in human asthma.