Involvement of extraneural tissues and upregulation of inducible nitric oxide synthase after experimental infection with rabies virus in BALB/c mice and LEW/SsN rats

Rabies in a Captive Lowland Tapir (Tapirus terrestris)

Rabies is a severe viral zoonosis of mammals and causes irreversible neurological damage. We describe the clinical presentation and anatomopathological lesions of rabies in a captive lowland tapir (Tapirus terrestris) in Bauru, São Paulo State, Brazil. The clinical course of the disease lasted 6 days and was characterized by progressive neurological deterioration and death. The main anatomopathological findings were non-suppurative encephalitis and presence of Negri bodies within neurons. Direct immunofluorescence and mouse inoculation tests were positive for rabies virus. This is the first report of rabies in a lowland tapir and highlights the importance of disease prevention under managed care and continuous control measures in urbanized environments.

Ocular and Lacrimal Gland Lesions in Naturally Occurring Rabies of Domestic and Wild Mammals

Investigations describing the ocular and lacrimal gland lesions associated with rabies are sparse. Here we characterize the pathological changes and distribution of rabies viral antigen in the eye, optic nerve, and lacrimal gland of 18 rabies cases from different mammalian species. Histology and immunohistochemistry for rabies virus, CD3, CD20, and Iba1 were performed on tissue sections of eye, optic nerve, and lacrimal gland. Polymerase chain reaction (PCR) for rabies was performed on all cases, including 7 formalin-fixed, paraffin-embedded (FFPE) and 11 frozen tissue samples of eye and lacrimal gland. Pathological changes in the eye consisted of retinal necrosis (12/18 cases) with occasional viral inclusions within ganglion cells (8/12 cases). Immunohistochemically, viral antigen was detected within the nerve fiber layer, ganglion cells, and inner plexiform layer in all 12 cases with retinal lesions and in 2 cases with no retinal lesions, as well as optic nerve (6/18 cases) and lacrimal gland epithelium (3/18 cases). CD3⁺ T lymphocytes were present in the retina (11/18 cases), optic nerve (2/18 cases), and lacrimal gland (11/18 cases). No CD20⁺ B lymphocytes or Iba1⁺ macrophages were detected. PCR for rabies virus was positive in 9 of 11 frozen samples but in only 2 of 7 FFPE samples. Five samples that were negative for rabies by PCR were positive by immunohistochemistry, and 2 samples were negative by both tests. These results provide evidence that rabies virus infection extends to the eye, likely via the ocular nerve, and that the lacrimal gland might be a source of viral infection.

Rabies encephalitis and extra-neural manifestations in a patient bitten by a domestic cat

Rabies encephalitis is a fatal zoonotic viral disease transmitted to humans either by domestic animals like dogs and cats or by wild animals like bats, skunks and raccoons. We present the case of a 25-year-old woman admitted due to behavioral disorders, generalized paresthesiasand acute respiratory deterioration compatible with a respiratory distress syndrome (ARDS) requiring orotracheal intubation, mechanical ventilation and empirical initiation of antibiotic and antiviral therapy. Chest tomography showed pneumomediastinum and changes suggestive of pulmonary infection. In the presence of neurological symptoms, a central nervous system (CNS) infection was suspected and the cerebrospinal fluid showed no pleocytosis, hiperproteinorrachy without glucose consumption; cranial CT scan was normal. During hospitalization, the family reported that the patient was bitten by a cat 30-day prior to the onset of rabies-like symptoms, and the animal was sacrificed. The patient had an unfavorable clinical evolution, with electroencephalographic activity dissociation evidenced by video telemetry. The zoonotic exposure led to the suspected diagnosis of rabies infection. The patient died and the suspected diagnosis was confirmed by histopathology, with presence of Negri bodies on cerebellum Purkinje cells and a positive immunofluorescence test for rabies virus. Both, initial extra-neural manifestations and late reporting of rabies exposure led to delayed diagnosis.

Rabies - epidemiology, pathogenesis, public health concerns and advances in diagnosis and control: a comprehensive review

Rabies is a zoonotic, fatal and progressive neurological infection caused by rabies virus of the genus Lyssavirus and family Rhabdoviridae. It affects all warm-blooded animals and the disease is prevalent throughout the world and endemic in many countries except in Islands like Australia and Antarctica. Over 60,000 peoples die every year due to rabies, while approximately 15 million people receive rabies post-exposure prophylaxis (PEP) annually. Bite of rabid animals and saliva of infected host are mainly responsible for transmission and wildlife like raccoons, skunks, bats and foxes are main reservoirs for rabies. The incubation period is highly variable from 2 weeks to 6 years (avg. 2-3 months). Though severe neurologic signs and fatal outcome, neuropathological lesions are relatively mild. Rabies virus exploits various mechanisms to evade the host immune responses. Being a major zoonosis, precise and rapid diagnosis is important for early treatment and effective prevention and control measures. Traditional rapid Seller's staining and histopathological methods are still in use for diagnosis of rabies. Direct immunofluoroscent test (dFAT) is gold standard test and most commonly recommended for diagnosis of rabies in fresh brain tissues of dogs by both OIE and WHO. Mouse inoculation test (MIT) and polymerase chain reaction (PCR) are superior and used for routine diagnosis. Vaccination with live attenuated or inactivated viruses, DNA and recombinant vaccines can be done in endemic areas. This review describes in detail about epidemiology, transmission, pathogenesis, advances in diagnosis, vaccination and therapeutic approaches along with appropriate prevention and control strategies.

Protective immune response of oral rabies vaccine in stray dogs, corsacs and steppe wolves after a single immunization

In this study the safety and protective immunity of an oral rabies vaccine, based on the live, modified rabies virus strain VRC-RZ2, was examined in stray dogs (Canis Sp.), corsacs (Vulpes corsac) and steppe wolves (Canis lupus campestris). In the safety group (dogs, n=6; corsacs, n=3; wolves, n=3) which was vaccinated with a 10-times field dose/animal, no animals showed any signs of disease or changes in behavior or appetite during the period of clinical observation, similar to the animals in the negative control group. Saliva samples taken from animals prior and post (5^th and 10^th days) vaccination failed to demonstrate rabies virus antigen. Observations of immunogenicity in vaccinated carnivores (dogs, corsacs and wolves) during a 180 day period showed the titers of virus neutralizing antibodies (VNA) in the blood sera of vaccinated dogs to be within 0.59-1.37 IU/mL. On 14 days post vaccination (dpv), all the wild carnivores had detectable levels of neutralizing antibodies, with mean titers ranging from 0.50 ± 0.07 IU/mL (for wolves) to 0.59 ± 0.10 IU/mL (for corsacs). Weeks after vaccination, all the vaccinated wolves and corsacs had higher levels of neutralizing antibodies: 0.70 ± 0.10 - 0.71 ± 0.08 IU/mL at 30 dpv, 1.06 ± 0.08 - 1.28 ± 0.21 IU/mL at 60 dpv and 0.41 ± 0.09 - 047 ± 0.06 at 180 dpv. The highest level of VNA (˃1.0 IU/ml) was detected at 60 dpv, in all vaccinated animals. After challenge all vaccinated dogs remained healthy for 180 days. Control animals (unvaccinated dogs) developed symptoms of rabies on day 6 post administration of a virulent virus and died of rabies on days 11-13. Of note, the VNA titers in all the wild carnivores (corsacs and wolves) immunized with VRC-RZ2 were higher than 0.5 IU/ml (0.59 ± 0.11 IU/ml), even as early as 14 days post vaccination. These, presumably protective, titers of antibodies to rabies virus were present in the dogs and wild carnivores examined in this study for at least 180 days.

Quantitative Analysis of the Microtubule Interaction of Rabies Virus P3 Protein: Roles in Immune Evasion and Pathogenesis

Although microtubules (MTs) are known to have important roles in intracellular transport of many viruses, a number of reports suggest that specific viral MT-associated proteins (MAPs) target MTs to subvert distinct MT-dependent cellular processes. The precise functional importance of these interactions and their roles in pathogenesis, however, remain largely unresolved. To assess the association with disease of the rabies virus (RABV) MAP, P3, we quantitatively compared the phenotypes of P3 from a pathogenic RABV strain, Nishigahara (Ni) and a non-pathogenic Ni-derivative strain, Ni-CE. Using confocal/live-cell imaging and dSTORM super-resolution microscopy to quantify protein interactions with the MT network and with individual MT filaments, we found that the interaction by Ni-CE-P3 is significantly impaired compared with Ni-P3. This correlated with an impaired capacity to effect association of the transcription factor STAT1 with MTs and to antagonize interferon (IFN)/STAT1-dependent antiviral signaling. Importantly, we identified a single mutation in Ni-CE-P3 that is sufficient to inhibit MT-association and IFN-antagonist function of Ni-P3, and showed that this mutation alone attenuates the pathogenicity of RABV. These data provide evidence that the viral protein-MT interface has important roles in pathogenesis, suggesting that this interface could provide targets for vaccine/antiviral drug development.

Subversion of the Immune Response by Rabies Virus

Rabies has affected mankind for several centuries and is one of the oldest known zoonoses. It is peculiar how little is known regarding the means by which rabies virus (RABV) evades the immune response and kills its host. This review investigates the complex interplay between RABV and the immune system, including the various means by which RABV evades, or advantageously utilizes, the host immune response in order to ensure successful replication and spread to another host. Different factors that influence immune responses—including age, sex, cerebral lateralization and temperature—are discussed, with specific reference to RABV and the effects on host morbidity and mortality. We also investigate the role of apoptosis and discuss whether it is a detrimental or beneficial mechanism of the host’s response to infection. The various RABV proteins and their roles in immune evasion are examined in depth with reference to important domains and the downstream effects of these interactions. Lastly, an overview of the means by which RABV evades important immune responses is provided. The research discussed in this review will be important in determining the roles of the immune response during RABV infections as well as to highlight important therapeutic target regions and potential strategies for rabies treatment.

What Is the Arrhythmic Substrate in Viral Myocarditis? Insights from Clinical and Animal Studies

Sudden cardiac death (SCD) remains an unsolved problem in the twenty-first century. It is often due to rapid onset, ventricular arrhythmias caused by a number of different clinical conditions. A proportion of SCD patients have identifiable diseases such as cardiomyopathies, but for others, the causes are unknown. Viral myocarditis is becoming increasingly recognized as a contributor to unexplained mortality, and is thought to be a major cause of SCD in the first two decades of life. Myocardial inflammation, ion channel dysfunction, electrophysiological, and structural remodeling may play important roles in generating life-threatening arrhythmias. The aim of this review article is to examine the electrophysiology of action potential conduction and repolarization and the mechanisms by which their derangements lead to triggered and reentrant arrhythmogenesis. By synthesizing experimental evidence from pre-clinical and clinical studies, a framework of how host (inflammation), and viral (altered cellular signaling) factors can induce ion electrophysiological and structural remodeling is illustrated. Current pharmacological options are mainly supportive, which may be accompanied by mechanical circulatory support. Heart transplantation is the only curative option in the worst case scenario. Future strategies for the management of viral myocarditis are discussed.

Raccoon rabies virus variant transmission through solid organ transplantation

IMPORTANCE

The rabies virus causes a fatal encephalitis and can be transmitted through tissue or organ transplantation. In February 2013, a kidney recipient with no reported exposures to potentially rabid animals died from rabies 18 months after transplantation.

OBJECTIVES

To investigate whether organ transplantation was the source of rabies virus exposure in the kidney recipient, and to evaluate for and prevent rabies in other transplant recipients from the same donor.

DESIGN

Organ donor and all transplant recipient medical records were reviewed. Laboratory tests to detect rabies virus-specific binding antibodies, rabies virus neutralizing antibodies, and rabies virus antigens were conducted on available specimens, including serum, cerebrospinal fluid, and tissues from the donor and the recipients. Viral ribonucleic acid was extracted from tissues and amplified for nucleoprotein gene sequencing for phylogenetic comparisons.

MAIN OUTCOMES AND MEASURES

Determination of whether the donor died from undiagnosed rabies and whether other organ recipients developed rabies.

RESULTS

In retrospect, the donor's clinical presentation (which began with vomiting and upper extremity paresthesias and progressed to fever, seizures, dysphagia, autonomic dysfunction, and brain death) was consistent with rabies. Rabies virus antigen was detected in archived autopsy brain tissue collected from the donor. The rabies viruses infecting the donor and the deceased kidney recipient were consistent with the raccoon rabies virus variant and were more than 99.9% identical across the entire N gene (1349/1350 nucleotides), thus confirming organ transplantation as the route of transmission. The 3 other organ recipients remained asymptomatic, with rabies virus neutralizing antibodies detected in their serum after completion of postexposure prophylaxis (range, 0.3-40.8 IU/mL).

CONCLUSIONS AND RELEVANCE

Unlike the 2 previous clusters of rabies virus transmission through solid organ transplantation, there was a long incubation period in the recipient who developed rabies, and survival of 3 other recipients without pretransplant rabies vaccination. Rabies should be considered in patients with acute progressive encephalitis of unexplained etiology, especially for potential organ donors. A standard evaluation of potential donors who meet screening criteria for infectious encephalitis should be considered, and risks and benefits for recipients of organs from these donors should be evaluated.