The 2022 monkeypox outbreak 1 year on: The 5 Ws.

In May 2022, World Health Organization (WHO) reported an outbreak of Mpox in several European countries which were previously Mpox free. Mpox (formerly known as monkeypox) is a zoonotic viral disease endemic in Central and West Africa. The sudden emergence of Mpox outside Africa and its subsequent rapid spread lead the WHO to declare the outbreak as Public Health Emergency of International Concern. By 15 May 2023, a total of 87,704 confirmed cases and 140 deaths had been reported from 111 countries and territories worldwide. Looking back on this outbreak 1 year later, several important questions have arisen. Here, we address these questions using the classic 5 Ws: What, When, Where, Who and Why? We discuss these questions to understand how this outbreak emerged and how it was effectively managed. We outline what needs to be done to prevent, or at least minimise, outbreaks due to emerging and re-emerging viral infections.

Monkeypox: Past, Present, and Future.

Monkeypox (Mpox) is a zoonotic disease caused by a virus (monkeypox virus-MPV) belonging to the Poxviridae family. In humans, the disease has an incubation period of 5-21 days and then progresses in two phases, the prodromal phase and the rash phase. The prodromal phase is characterized by non-specific symptoms such as fever, muscle pain, malaise, lymphadenopathy, headache, and chills. Skin lesions appear in the rash phase of the disease. These lesions progress through different stages (macules, papules, vesicles, and pustules). In May 2022, WHO reported an outbreak of human Mpox in several countries which were previously Mpox-free. As per the CDC report of March 01, 2023, a total of 86,231 confirmed cases of Mpox and 105 deaths have been reported from 110 countries and territories across the globe. Notably, more than 90% of these countries were reporting Mpox for the first time. The phylogenetic analysis revealed that this outbreak was associated with the virus from the West African clade. However, most of the cases in this outbreak had no evidence of travel histories to MPV-endemic countries in Central or West Africa. This outbreak was primarily driven by the transmission of the virus via intimate contact in men who have sex with men (MSM). The changing epidemiology of Mpox raised concerns about the increasing spread of the disease in non-endemic countries and the urgent need to control and prevent it. In this chapter, we present all the documented cases of Mpox from 1970 to 2023 and discuss the past, present, and future of MPV.

CRISPR-Cas12-based nucleic acids detection systems.

Because of the outstanding contribution in genome editing, CRISPR has undoubtedly become the most popular technology around the world and two pioneers are awarded the Nobel Prize in Chemistry this year. Besides, along with the discovery of nonspecific trans-cleavage activities of several Cas proteins such as Cas12 and Cas13, many CRISPR-based molecular diagnostic systems have been successfully created, showing advantages in sensitivity, specificity and operation convenience. Among them, systems with Cas12, which targets DNA and trans-cleaves single-stranded DNA probes, are both simple and highly efficient. Here in this review, we mainly focus on the Cas12-based methods and briefly discuss their applications in nucleic acids detection and beyond.

Epstein-Barr virus-infected cells release Fas ligand in exosomal fractions and induce apoptosis in recipient cells via the extrinsic pathway.

Epstein-Barr virus (EBV; human herpesvirus 4) is an oncogenic herpesvirus implicated in the pathogenesis of several human malignancies. A number of recent studies indicate that EBV can manipulate the local microenvironment by excreting viral and cellular components in nanovesicles called exosomes. In this study, we investigated the impact of EBV-derived exosomes on apoptosis of recipient cells and the molecular pathway involved in this process. Exosomes from EBV-infected but not from non-infected cells induced apoptosis in a number of different cell types, including B-cells, T-cells and epithelial cells. However, this phenomenon was not universal and the Burkitt's lymphoma-derived B-cell line BJAB was found to be resistant to apoptosis. Exosomes from both type I and type III EBV latently infected cells induced apoptosis in a dose- and time-dependent manner. Moreover, cells exposed to EBV exosomes did not form colonies in soft agar assays. We further show that fluorescently labelled exosomes derived from EBV-infected cells are taken up by non-infected cells and induce apoptosis via the extrinsic pathway. Inhibition of caspase-3/7/8 blocks EBV exosome-mediated apoptosis. Furthermore, our data indicate that EBV exosomes trigger apoptosis through the Fas ligand (FasL)-mediated extrinsic pathway, as FasL was present in EBV exosomal fractions and anti-FasL antibodies could block EBV exosome-mediated apoptosis. Together, these data support the notion that EBV hijacks the exosome pathway to excrete viral and cellular components that can modulate its microenvironment.

Healthy rabbits are susceptible to Epstein-Barr virus infection and infected cells proliferate in immunosuppressed animals.

BACKGROUND: Epstein-Barr virus (EBV) is an oncogenic virus implicated in the pathogenesis of several human malignancies. However, due to the lack of a suitable animal model, a number of fundamental questions pertaining to the biology of EBV remain poorly understood. Here, we explore the potential of rabbits as a model for EBV infection and investigate the impact of immunosuppression on viral proliferation and gene expression. METHODS: Six healthy New Zealand white rabbits were inoculated intravenously with EBV and blood samples collected prior to infection and for 7 weeks post-infection. Three weeks after the last blood collection, animals were immunosuppressed with daily intramuscular injections of cyclosporin A at doses of 20 mg/kg for 15 days and blood collected twice a week from each rabbit. The animals were subsequently sacrificed and tissues from all major organs were collected for subsequent analysis. RESULTS: Following intravenous inoculation, all 6 rabbits seroconverted with raised IgG and IgM titres to EBV, but viral DNA in peripheral blood mononuclear cells (PBMCs) could only be detected intermittently. Following immunosuppression however, EBV DNA could be readily detected in PBMCs from all 4 rabbits that survived the treatment. Quantitative PCR indicated an increase in EBV viral load in PBMCs as the duration of immunosuppression increased. At autopsy, splenomegaly was seen in 3/4 rabbits, but spleens from all 4 rabbit were EBV PCR positive. EBER-in situ hybridization and immunoshistochemistry revealed the presence of a large number of EBER-positive and LMP-1 positive lymphoblasts in the spleens of 3/4 rabbits. To a lesser extent, EBER-positive cells were also seen in the portal tract regions of the liver of these rabbits. Western blotting indicated that EBNA-1 and EBNA-2 were also expressed in the liver and spleen of infected animals. CONCLUSION: EBV can infect healthy rabbits and the infected cells proliferate when the animals are immunocompromised. The infected cells expressed several EBV-latent gene products which are probably driving the proliferation, reminiscent of what is seen in immunocompromised individuals. Further work is required to explore the potential of rabbits as an animal model for studying EBV biology and tumorigenesis.

A simple procedure for the extraction of DNA from long-term formalin-preserved brain tissues for the detection of EBV by PCR.

Long-term formalin fixed brain tissues are potentially an important source of material for molecular studies. Ironically, very few protocols have been published describing DNA extraction from such material for use in PCR analysis. In our attempt to investigate the role of Epstein-Barr virus (EBV) in the pathogenesis of multiple sclerosis (MS), extracting PCR quality DNA from brain samples fixed in formalin for 2-22 years, proved to be very difficult and challenging. As expected, DNA extracted from these samples was not only of poor quality and quantity, but more importantly, it was frequently found to be non-amplifiable due to the presence of PCR inhibitors. Here, we describe a simple and reproducible procedure for extracting DNA using a modified proteinase K and phenol-chloroform methodology. Central to this protocol is the thorough pre-digestion washing of the tissues in PBS, extensive digestion with proteinase K in low SDS containing buffer, and using low NaCl concentration during DNA precipitation. The optimized protocol was used in extracting DNA from meninges of 26 MS and 6 non-MS cases. Although the quality of DNA from these samples was generally poor, small size amplicons (100-200 nucleotides) of the house-keeping gene, ß-globin could be reliably amplified from all the cases. PCR for EBV revealed positivity in 35% (9/26) MS cases, but 0/6 non-MS cases. These findings indicate that the method described here is suitable for PCR detection of viral sequences in long-term formalin persevered brain tissues. Our findings also support a possible role for EBV in the pathogenesis of MS.

The labyrinth of interactions of Epstein-Barr virus-encoded small RNAs.

Epstein-Barr Virus (EBV) is an oncogenic herpesvirus implicated in the pathogenesis of a number of human malignancies. However, the mechanism by which EBV leads to malignant transformation is not clear. A number of viral latent gene products, including non-protein coding small RNAs, are believed to be involved. Epstein-Barr virus-encoded RNA 1 (EBER1) and EBER2 are two such RNA molecules that are abundantly expressed (up to 10(7) copies) in all EBV-infected cells, but their function remains poorly understood. These polymerase III transcripts have extensive secondary structure and exist as ribonucleoproteins. An accumulating body of evidence suggests that EBERs play an important role, directly or indirectly, in EBV-induced oncogenesis. Here, we summarize the current understanding of the complex interactions of EBERs with various cellular factors and the potential pathways by which these small RNAs are able to influence EBV-infected cells to proliferate and to induce tumorigenesis. The exosome pathway is probably involved in the cellular excretion of EBERs and facilitating some of their biological effects.

A novel coronavirus capable of lethal human infections: an emerging picture.

In September 2012, a novel coronavirus was isolated from a patient in Saudi Arabia who had died of an acute respiratory illness and renal failure. The clinical presentation was reminiscent of the outbreak caused by the SARS-coronavirus (SARS-CoV) exactly ten years ago that resulted in over 8000 cases. Sequence analysis of the new virus revealed that it was indeed a member of the same genus as SARS-CoV. By mid-February 2013, 12 laboratory-confirmed cases had been reported with 6 fatalities. The first 9 cases were in individuals resident in the Middle East, while the most recent 3 cases were in family members resident in the UK. The index case in the UK family cluster had travel history to Pakistan and Saudi Arabia. Although the current evidence suggests that this virus is not highly transmissible among humans, there is a real danger that it may spread to other parts of the world. Here, a brief review of the events is provided to summarize the rapidly emerging picture of this new virus.

Assessing the Efficacy of VLP-Based Vaccine against Epstein-Barr Virus Using a Rabbit Model.

Epstein-Barr virus (EBV) is etiologically associated with a number of malignant and non-malignant conditions. Thus, a prophylactic vaccine against this virus could help to reduce the burden of many EBV-associated diseases. Previously, we reported that an EBV virus-like particle (VLP) vaccine was highly immunogenic and produced a strong humoral response in mice. However, since EBV does not infect mice, the efficacy of the VLP in preventing EBV infection could not be addressed. Here we examined, for the first time, the efficacy of the EBV-VLP vaccine using a novel rabbit model of EBV infection. Animals vaccinated with two doses of VLP elicited higher antibody responses to total EBV antigens compared to animals receiving one dose. Vaccinated animals also elicited both IgM and IgG to EBV-specific antigens, VCA and EBNA1. Analysis of peripheral blood and spleen for EBV copy number indicated that the viral load in both of these compartments was lower in animals receiving a 2-dose vaccine. However, the VLP vaccine was ineffective in preventing EBV infection. With several other EBV vaccine candidates currently at various stages of development and testing, we believe that the rabbit model of EBV infection could be a great platform for evaluating potential candidates.

Crimean-Congo hemorrhagic fever in the Arab world: A systematic review.

Crimean-Congo hemorrhagic fever (CCHF) is an important tick-borne viral infection with a fatality rate of up to 50% during outbreaks. Crimean-Congo hemorrhagic fever virus (CCHFV) is sustained in the ecosystem in benign form through vertical and horizontal transmission cycles involving tick vectors, wildlife, and livestock. Hyalomma ticks are considered the major source of human infection. CCHF occurs most often among butchers, slaughterhouse workers, and farmworkers through infected tick bites or/and contact with blood and tissues of infected livestock. The nosocomial transmission can occur in auxiliary nurses and physicians through contact with the infected patients. The widespread distribution of CCHFV most probably occurred by ticks on migratory birds, or through international travel and trade of livestock and wildlife. During co-infections of ticks and vertebrates, reassortment among genome segments could play a significant role in generating diversity, and hence, a potential risk for the emergence of novel variants. In this systematic review, we aimed to determine the epidemiology, transmission, distribution, mortality, and clinical features of CCHF in 22 Arab countries, comprising the Arab world. Based on the analysis of 57 studies published from 1978 to 2021, we found 20 tick species that could be associated with CCHFV transmission. During the 43-year period, 321 cases of CCHF were reported from 9/22 Arab countries, Iraq, Kuwait, UAE, Saudi Arabia, Oman, Sudan, Egypt, Tunisia, and Mauritania. The mean case fatality rate was 29% during various outbreaks. Individuals working in abattoirs/slaughter houses, livestock farms, and healthcare were most at risk. Contact with blood or body secretions from infected animals and patients was the most common mode of transmission. A number of different animals, including cattle, goats, sheep, and camels were reported to be seropositive for CCHFV. The highest seroprevalence was observed in camels (29%), followed by cattle (21%), goats (15%), and sheep (14%). We discuss these results in the context of policy-making and potential preventative measures that can be implemented to reduce the burden of CCHF in the Arab world.

What do animal models tell us about the role of EBV in the pathogenesis of multiple sclerosis?

Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS), marked primarily by demyelination, inflammation, and neurodegeneration. While the prevalence and incidence rates of MS are on the rise, the etiology of the disease remains enigmatic. Nevertheless, it is widely acknowledged that MS develops in persons who are both genetically predisposed and exposed to a certain set of environmental factors. One of the most plausible environmental culprits is Epstein-Barr virus (EBV), a common herpesvirus asymptomatically carried by more than 90% of the adult population. How EBV induces MS pathogenesis remains unknown. A comprehensive understanding of the biology of EBV infection and how it contributes to dysfunction of the immune system and CNS, requires an appreciation of the viral dynamics within the host. Here, we aim to outline the different animal models, including nonhuman primates (NHP), rodents, and rabbits, that have been used to elucidate the link between EBV and MS. This review particularly focuses on how the disruption in virus-immune interaction plays a role in viral pathogenesis and promotes neuroinflammation. We also summarize the effects of virus titers, age of animals, and route of inoculation on the neuroinvasiveness and neuropathogenic potential of the virus. Reviewing the rich data generated from these animal models could provide directions for future studies aimed to understand the mechanism(s) by which EBV induces MS pathology and insights for the development of prophylactic and therapeutic interventions that could ameliorate the disease.

The Impact of Deleting Stem-Loop 1 of Epstein-Barr Virus-Encoded RNA 1 on Cell Proliferation.

Epstein-Barr virus-encoded RNAs (EBERs) are two small, noncoding, structurally conserved transcripts, constitutively expressed at >106 copies per EBV-infected cell. They have been shown to drive cell growth. However, the mechanism(s) involved in EBER-induced proliferation is not clear. In this study, we investigated the molecular mechanisms and structural impact of EBER1. Sequences of EBER1 stem-loops (SL) 1, 3, and 4 were deleted, creating three mutants: ∆SL1, ∆SL3, and ∆SL4. These mutants were cloned into pHebo plasmids and expressed in Jurkat cell lines. Cells transfected with wildtype EBER1 and pHebo were used as controls. Cell proliferation was monitored by microscopy and flow cytometry. Microarray, qPCR, and Western blotting were used to investigate the cell cycle markers. We found significantly higher cell proliferation in wildtype EBER1 cells compared to pHebo, ∆SL1, and ∆SL3, but not ∆SL4 mutants. There was also significant upregulation of S-phase and G2/M phase markers in wildtype EBER1 and ∆SL4 mutant. Furthermore, CDT1, a factor for DNA replication, was upregulated in wildtype EBER1 and ∆SL4 mutant. However, in ∆SL1 mutant, CDT1 was significantly downregulated and translocated to the cytoplasm. These data indicate that the structure of EBER1 is important in cell proliferation.

Automated artificial intelligence-enabled proactive preparedness real-time system for accurate prediction of COVID-19 infections- Performance evaluation.

COVID-19 is a contagious disease that has infected over half a billion people worldwide. Due to the rapid spread of the virus, countries are facing challenges to cope with the infection growth. In particular, healthcare organizations face difficulties efficiently provisioning medical staff, equipment, hospital beds, and quarantine centers. Machine and deep learning models have been used to predict infections, but the selection of the model is challenging for a data analyst. This paper proposes an automated Artificial Intelligence-enabled proactive preparedness real-time system that selects a learning model based on the temporal distribution of the evolution of infection. The proposed system integrates a novel methodology in determining the suitable learning model, producing an accurate forecasting algorithm with no human intervention. Numerical experiments and comparative analysis were carried out between our proposed and state-of-the-art approaches. The results show that the proposed system predicts infections with 72.1% less Mean Absolute Percentage Error (MAPE) and 65.2% lower Root Mean Square Error (RMSE) on average than state-of-the-art approaches.

Ameliorating effect of erythropoietin in a severe case of COVID-19: case report.

The COVID-19 pandemic is arguably one of the greatest public health crises since the 1918 influenza pandemic. Although several vaccines have been approved and rolled out, effective antiviral treatment options are very limited. Here, we present a case of severe COVID-19 that failed to respond to the standard interventions and continued to deteriorate. On day 22 of his illness, after informed consent, the patient was administered 4000IU of erythropoietin (EPO) subcutaneously, in the hope of improving his O2 saturation. Positive response was observed in the patient within 24 hours. This prompted us to continued EPO treatment for a total of 42 days until full recovery and discharge. Our findings warrant further studies to ascertain the use of EPO in severe cases COVID-19.

Effectiveness of containment strategies in preventing SARS-CoV-2 transmission.

BACKGROUND: Despite substantial resources deployed to curb SARS-CoV-2 transmission, controlling the COVID-19 pandemic has been a major challenge. New variants of the virus are frequently emerging leading to new waves of infection and re-introduction of control measures. In this study, we assessed the effectiveness of containment strategies implemented in the early phase of the pandemic. METHODS: Real-world data for COVID-19 cases was retrieved for the period Jan 1 to May 1, 2020 from a number of different sources, including PubMed, MEDLINE, Facebook, Epidemic Forecasting and Google Mobility Reports. We analyzed data for 18 countries/regions that deployed containment strategies such as travel restrictions, lockdowns, stay-at-home requests, school/public events closure, social distancing, and exposure history information management (digital contact tracing, DCT). Primary outcome measure was the change in the number of new cases over 30 days before and after deployment of a control measure. We also compared the effectiveness of centralized versus decentralized DCT. Time series data for COVID-19 were analyzed using Mann-Kendall (M-K) trend tests to investigate the impact of these measures on changes in the number of new cases. The rate of change in the number of new cases was compared using M-K z-values and Sen's slope. RESULTS: In spite of the widespread implementation of conventional strategies such as lockdowns, travel restrictions, social distancing, school closures, and stay-at-home requests, analysis revealed that these measures could not prevent the spread of the virus. However, countries which adopted DCT with centralized data storage were more likely to contain the spread. CONCLUSIONS: Centralized DCT was more effective in containing the spread of COVID-19. Early implementation of centralized DCT should be considered in future outbreaks. However, challenges such as public acceptance, data security and privacy concerns will need to be addressed.

Global data analysis and risk factors associated with morbidity and mortality of COVID-19.

This review was focused on global data analysis and risk factors associated with morbidity and mortality of coronavirus disease 2019 from different countries, including Bangladesh, Brazil, China, Central Eastern Europe, Egypt, India, Iran, Pakistan, and South Asia, Africa, Turkey and UAE. Male showed higher confirmed and death cases compared to females in most of the countries. In addition, the case fatality ratio (CFR) for males was higher than for females. This gender variation in COVID-19 cases may be due to males' cultural activities, but similar variations in the number of COVID-19 affected males and females globally. Variations in the immune system can illustrate this divergent risk comparatively higher in males than females. The female immune system may have an edge to detect pathogens slightly earlier. In addition, women show comparatively higher innate and adaptive immune responses than men, which might be explained by the high density of immune-related genes in the X chromosome. Furthermore, SARS-CoV-2 viruses use angiotensin-converting enzyme 2 (ACE2) to enter the host cell, and men contain higher ACE2 than females. Therefore, males may be more vulnerable to COVID-19 than females. In addition, smoking habit also makes men susceptible to COVID-19. Considering the age-wise distribution, children and older adults were less infected than other age groups and the death rate. On the contrary, more death in the older group may be associated with less immune system function. In addition, most of these group have comorbidities like diabetes, high pressure, low lungs and kidney function, and other chronic diseases. Due to the substantial economic losses and the numerous infected people and deaths, research examining the features of the COVID-19 epidemic is essential to gain insight into mitigating its impact in the future and preparedness for any future epidemics.

Pandemic (H1N1) 2009, Abu Dhabi, United Arab Emirates, May 2009-March 2010.

To ascertain characteristics of pandemic (H1N1) 2009 virus infection, we reviewed medical records for all suspected or confirmed cases reported in Abu Dhabi during May 2009-March 2010. Overall case-fatality rate was 1.4/100,000 population. Most patients who died had ≥1 risk factor, and female decedents were considerably younger than male decedents.

Localization of Epstein-Barr virus to infiltrating lymphocytes in breast carcinomas and not malignant cells.

The pathogenesis of breast cancer is unknown. In recent years, a number of studies have implicated a role for Epstein-Barr virus (EBV) in a subset of cases. However, these findings are controversial and others have failed to find any link between the virus and this malignancy. We hypothesized that technical differences and the different type and ethnic origin of the cases may be the cause of the disparities reported. Using a highly sensitive EBER-in situ hybridization and immunohistochemistry, we examined 219 samples (158 malignant and 61 non-malignant) from 61 Emirati breast cancer cases to determine if EBV was etiologically associated with Emirati cases and if there was any correlation with other established prognostic factors such as age, histological type, lymph node metastasis, estrogen, progesterone and HER2 expression. We found 47.5% of the cases to be EBV positive, but the virus was localized to occasional infiltrating lymphocytes and not in the malignant cells. EBV lymphocytes were more commonly observed in lymph nodes than in breast tissues, but there was no correlation with malignancy or hormone status. The mean age of our patients was 48years and hormone receptor staining revealed 20% of the cases to be triple negative (ER-/PR-/HER2-). We conclude that although EBV can be detected in breast cancer cases, it is not directly associated with the disease. Thus, a PCR-based approach cannot be used to link this ubiquitous virus to the pathogenesis of breast cancer. Furthermore, we do not find any correlation between the presence of EBV in infiltrating lymphocytes and ER, PR, HER2 expression. We believe our findings will help explain some of the controversies relating to the role of EBV in the pathogenesis of breast cancer.

Uncovering early events in primary Epstein-Barr virus infection using a rabbit model.

Epstein-Barr virus (EBV) is an oncogenic herpesvirus implicated in the pathogenesis of several malignant and non-malignant conditions. However, a number of fundamental aspects about the biology of EBV and the mechanism(s) by which this virus induces pathology remain unknown. One major obstacle has been the lack of a suitable animal model for EBV infection. In this study, using our recently established rabbit model of EBV infection, we examined the early events following primary EBV infection. We show that, both immunocompetent and immunosuppressed animals were readily susceptible to EBV infection. However, immunosuppressed animals showed marked splenomegaly and widespread infection. Following EBV infection, the virus primarily targeted naïve IgM+, CD20+, CD21+ and CD79a+ B cells. Infected cells expressed varying sets of viral latent/lytic gene products. Notably, co-expression of latent and lytic proteins in the same cell was not observed. Infected cells in type 0/1 latency (EBERs+), were small and proliferating (Ki67+). By contrast, cells in type 2/3 latency (LMP1+), were large, non-proliferating (Ki-67-) and p53+. Although infected B-cells were widely present in splenic follicles, they did not express germinal center marker, BCL-6. Taken together, this study shows for the first time, some of the early events following primary EBV infection.

Primary Peripheral Epstein-Barr Virus Infection Can Lead to CNS Infection and Neuroinflammation in a Rabbit Model: Implications for Multiple Sclerosis Pathogenesis.

Epstein-Barr virus (EBV) is a common herpesvirus associated with malignant and non-malignant conditions. An accumulating body of evidence supports a role for EBV in the pathogenesis of multiple sclerosis (MS), a demyelinating disease of the CNS. However, little is known about the details of the link between EBV and MS. One obstacle which has hindered research in this area has been the lack of a suitable animal model recapitulating natural infection in humans. We have recently shown that healthy rabbits are susceptible to EBV infection, and viral persistence in these animals mimics latent infection in humans. We used the rabbit model to investigate if peripheral EBV infection can lead to infection of the CNS and its potential consequences. We injected EBV intravenously in one group of animals, and phosphate-buffered saline (PBS) in another, with and without immunosuppression. Histopathological changes and viral dynamics were examined in peripheral blood, spleen, brain, and spinal cord, using a range of molecular and histopathology techniques. Our investigations uncovered important findings that could not be previously addressed. We showed that primary peripheral EBV infection can lead to the virus traversing the CNS. Cell associated, but not free virus in the plasma, correlated with CNS infection. The infected cells within the brain were found to be B-lymphocytes. Most notably, animals injected with EBV, but not PBS, developed inflammatory cellular aggregates in the CNS. The incidence of these aggregates increased in the immunosuppressed animals. The cellular aggregates contained compact clusters of macrophages surrounded by reactive astrocytes and dispersed B and T lymphocytes, but not myelinated nerve fibers. Moreover, studying EBV infection over a span of 28 days, revealed that the peak point for viral load in the periphery and CNS coincides with increased occurrence of cellular aggregates in the brain. Finally, peripheral EBV infection triggered temporal changes in the expression of latent viral transcripts and cytokines in the brain. The present study provides the first direct in vivo evidence for the role of peripheral EBV infection in CNS pathology, and highlights a unique model to dissect viral mechanisms contributing to the development of MS.