Estudou-se a freqüência da ocorrência de anticorpos antivírus da Artrite-encefalite dos Caprinos, em caprinos de 14 plantéis localizados no Estado de São Paulo, por um período de 2 anos, utilizando-se a técnica de imunodifusão em gel de ágar. A prevalência obtida foi de 26,3%, sendo significativamente maior nos caprinos mantidos em regime intensivo (31,8% - 733/2303) de criação do que no sistema semi-extensivo (13,1% - 128- 977). A infecção pelo vírus da Artrite-encefalite dos Caprinos aumentou gradativa e significativamente após os 6 meses de idade, havendo predominância da infecção nos caprinos mais velhos. Não se detectou influência de fatores sexuais sobre a prevalência da enfermidade determinada em caprinos do sexo feminino (27,9% - 663/2375) e masculino (32,3% - 94/291). A prevalência da doença foi significativamente maior nos caprinos das raças Anglo Nubiana (63,8% - 88/138) e Toggenbourg (56,0% - 28/50) do que nas demais raças estudadas: Saanen (27,4% - 673/2458), Alpina (11,9% - 59/497), Bôer (5,9% - 2/34) e caprinos mestiços (10,7% - 11/103). Paralelamente realizou-se estudo clínico dos animais infectados pelo vírus da Artrite-encefalite dos Caprinos, quando pudemos demonstrar que 17,1% (64/374) dos caprinos sororeagentes apresentavam a forma clínica articular da enfermidade e que 6,6% (17/249) das cabras sororeagentes apresentavam a forma mamária. A possibilidade de transmissão vertical transplacentária foi menor do que 3,8%. Verificou-se ser pequena a possibilidade dos cabritos se infectarem pelo colostro de cabras sororeagentes positivas, mas podem se infectar pelo leite oriundos dessas cabras infectadas (18,8% - 3/16). O tempo de duração dos anticorpos séricos adquiridos passivamente pelo colostro variou de 60 a 120 dias. Demonstrou-se, indiretamente, a presença e a viabilidade do vírus no sangue circulante, colostro e leite de caprinos infectados, bem como a possibilidadede infectar animais susceptíveis por inoculação, sendo o período de incubação de 45 a 60 dias. Não se demonstrou diferenças significativas dos teores séricos de proteína total, gamaglobulina e da atividade enzimática da glutamiltransferase - γGT em cabritos que receberam colostro de cabras infectadas ou não infectadas pelo mencionado vírus. / The frequency of occurrence of antibodies anti-caprine arthritis-encephalitis virus was studied in 14 herds in the State of São Paulo, during 2 years, using agar gel immunodiffusion. Prevalence was equal to 26.3%, and was significantly higher in animals kept under an intensive management scheme (31.8% - 733/2303), than in animals kept under a semi-extensive one (13.1% - 128- 977). Infection by the caprine arthritis-encephalitis virus increased gradual and significantly after 6 months of age. Infection was predominant in older animals. There was no gender influence on the prevalence of the disease, both in females (27.9% - 663/2375) and males (32.3% - 94/291). In relation to breed, prevalence of the disease was significantly higher in Anglo-Nubian (63.8% - 88/138) and Toggenbourg animals (56.0% - 28/50), than in the rest of the breeds studied: Saanen (27.4% - 673/2458), Alpine (11.9% - 59/497), Boer (5.9% - 2/34) and mixed breed animals (10.7% - 11/103). A clinical study of the animals infected by caprine arthritis-encephalitis virus was also performed. It was observed that 17.1% (64/374) of seroreagents presented the articular form of the disease and that 6.6% (17/249) of the seroreagent females presented the mammary form of the disease. The possibility of vertical, transplacentary transmission was lower than 3.8%. It was observed that the probability of infection of kids by colostrum of infected females was low (18.8% - 3/16). Antibodies passively acquired by colostrum ingestion lasted from 60 to 120 days. The presence and viability of the virus circulating in blood, colostrum and milk of infected animals, as well as the possibility of infection of susceptible animals by inoculation was indirectly demonstrated. Incubation period ranged from 45 to 60 days. There was no significant difference in serum levels of total protein and gammaglobulin, and in enzymatic activity of glutamiltransferase - γGT in kids that received colostrum from infected and non-infected females.

Introdução - No litoral sul do Estado de São Paulo, no período de 1975 a 1978, ocorreu uma epidemia, a Encefalite pelo arbovírus Rocio. A região foi objeto de estudo de diversos investigadores. Altas taxas de morbidade e mortalidade devido ao processo epidêmico foram observadas e causaram impacto socioeconômico. A maioria dos indivíduos infectados, no início da epidemia, era do sexo masculino e estava em idade produtiva, sendo trabalhadores rurais da região. Diante das limitações hospitalares e inespecificidade do tratamento na época, houve desde uma lenta convalescença, seqüelas até a ocorrência de óbitos, afetando a economia da região, que repercutiu principalmente na queda no turismo. Mediante este fato, justifica-se a importância deste estudo histórico-documental da encefalite por arbovírus Rocio. Objetivo - Objetivou-se relatar acontecimentos sociais e naturais, medidas clínicas, impactos midiáticos e avanços científicos relacionados à doença, verificando, a trajetória do Rocio. Método - Foi feita uma revisão de literatura de trabalhos publicados desde o início da epidemia até os dias atuais. As fontes consultadas foram teses, dissertações, livros, periódicos, bancos de dados de jornais e revistas, bases de dados cooperativas, relatórios de instituições públicas, contato com especialistas e comunicações em eventos. Resultados - Foi possível analisar como a mídia impressa relatou os acontecimentos sociais relacionados à epidemia e como foi a reação popular às notícias veiculadas, além de discutir a possibilidade de o homem voltar a ser acometido pelo Rocio, diante das atuais mudanças climáticas, acelerada urbanização e pressão sobre a cobertura vegetal no litoral sul do Estado, o que altera a ecologia das populações dessa região. Conclusões - Houve o desencontro entre informações veiculadas pela mídia e dados científicos fornecidos por pesquisadores e autoridades sanitárias, o que dificultava a aceitação da epidemia pela população e viabilizava a distorção de informações e criação de barreiras aos métodos de combate ao possível vetor. Ainda não se sabe como o vírus Rocio tornou-se emergente no litoral sul do Estado em 1975 e o porquê do seu silenciamento, entretanto é conhecido que esse arbovírus ainda mantém atividade, possibilitando o retorno da epidemia no país. / Introduction - On the south coast of São Paulo State, Brazil, there was an encephalitis epidemic due to the arbovirus Rocio from 1975 to 1978. Thus, the region has been the object of study by researchers. High rates of morbidity and mortality caused an enormous social impact. The most infected individuals at the beginning of the epidemic was male and was in the productive age. Facing the limitations of the hospital and nonspecific treatment at the time, there was since a slow convalescence, sequels and even the occurrence of deaths, affecting the regional economy, which mainly reflected the drop in local tourism. In view of this fact, it is the importance of this historical and documentary study of encephalitis caused by arbovirus Rocio during the epidemic period. Aim - The aim of this study was to report social and natural events, clinical measurements, media impacts and scientific advances related to the disease, checking the trajectory of virus Rocio. Method It was made a literature review of studies published since the beginning of the epidemic until the present day. The sources which were consulted: theses, dissertations, books, periodicals, databases of newspapers and magazines, electronic databases, reports from public institutions, contact with specialists in communications and events. Results - In this study, it was possible to analize how the written press communicated the social reactions related to the epidemic and how the population reacted the news communicated, in addition was possible to discuss the possibility of the human being be affected by Rocio again due to the current climate change, accelerated urbanization and pressure on the vegetation on the coast south of the State, thus changing the ecology of the population of that region. Conclusions - There was a contradiction between the information carried by the media and scientific data provided by researchers and health authorities, which hindered the acceptance of the epidemic by the population and facilitated the distortion of information. This fact created barriers to methods of combating the possible vector. It is not known how the virus Rocio has become emerging on the south coast of the State in 1975 and why it became silent, however it is know that the arbovirus still has activity, what allows the return of the epidemic in the country.

Encefalite auto-imune experimental (EAE) é o modelo animal da doença humana esclerose múltipla. Foi demonstrado que as estatinas podem ter efeitos benéficos na EAE. Diversos mecanismos de ação foram descritos para explicar esses efeitos, entre eles: estímulo a expressão de HO-1, inibição da expressão de Toll-like receptors (TLR) e inibição da produção de citocinas de padrão Th1. Estudamos o efeito de uma estatina, a sinvastatina, na evolução clínica da EAE e seus mecanismos de ação. Também avaliamos o papel do TLR4 na EAE. O tratamento com sinvastatina melhorou a evolução clínica da EAE nas doses de 1 e 5 mg/kg/dia. A análise do infiltrado celular no SNC mostrou mudança do padrão de diferenciação dos linfócitos com menor porcentagem de células produtoras de IL-17 nos grupos tratados em relação aos controles. Os animais TLR-4 -/- apresentaram melhor evolução da doença. Concluímos que o tratamento com sinvastatina melhora a evolução clínica da EAE através da inibição da produção de IL-17 e que animais TLR-4 -/- têm melhor desfecho clínico na EAE que os controles. / Experimental autoimmune encephalomyelitis (EAE) is considered the experimental model for the human multiple sclerosis disease. It has been demonstrated that statins, used as lipid-lowering agents, can have beneficial effects on EAE. Several actions have been described to explain these effects: enhancement of HO-1 expression, inhibition of Toll-like receptors expression and inhibition of Th1 cytokines. We have investigated the effect of a statin, simvastatin, on EAE clinical development and the mechanisms behind those effects. Simvastatin treatment ameliorated EAE clinical outcome at doses 1 and 5 mg/kg/day. SNC cellular infiltrates analysis showed altered pattern of differentiation with decreased percentage of IL-17-producing T lymphocytes in treated group comparing with controls. TLR4 -/- mice showed better clinical development. We concluded that simvastatin treatment ameliorates EAE clinical outcome through inhibition of IL-17 production. Mice TLR4 -/- have better EAE clinical outcome than WT controls.

Orientador: Tereza Cristina Cardoso Silva / Banca: Roberto Gameiro de Carvalho / Banca: Andréa Fontes Garcia / Banca: Ana Carolina Borsanelli / Banca: Jamila Cristina Baptistella / Resumo: O herpes vírus bovino 5 (HVB-5) é um agente infeccioso pertencente a família Herpesviridae, sub-família Alphaherpesvirinae e gênero Varicellovirus. É um vírus neurotrópico que causa doenças neurológicas principalmente em animais jovens em todo mundo, especialmente nos países Sul-americanos, resultado em significantes perdas econômicas. A infecção pelo herpesvírus bovino 5 em gado jovemestá associado a doença neurológica que é, usualmente, fatal, sendo um ótimo modelo para estudar a patogênese da meningoencefalite induzida por vírus. O HVB5 replica na mucosa nasal, e invadesistema nervoso central (SNC), principalmente por meio do sistema olfatório. A resposta imune inata desencadeada pelo hospedeiro frente à replicação do vírus por meio da via olfativa não é totalmente entendida. Estudos verificaram as variações nos níveis de expressão de receptores Toll-Like (TLRs) em diferentes regiões do sistema nervoso central bovino durante a infecção aguda e reativação de bovinos infectados por HVB-1 e HVB-5-.Uma nova perspectiva para entender a relação do patógeno e o hospedeirorelacionando os microRNAs(miRNAs) que interagem com a resposta imune inatadurante infecções virais neurotrópicas. / Abstract: Bovine herpes virus 5 (BHV-5) is an infectious agent belonging to the family Herpesviridae, subfamily Alphaherpesvirinae and genus Varicellovirus. It is a neurotropic virus that causes neurological diseases mainly in young animals worldwide, especially in the South American countries, resulting in significant economic losses. Bovine herpesvirus 5 infection in young cattle is associated with neurological disease, which is usually fatal and is a good model for studying the pathogenesis of virus-induced meningoencephalitis. The BHV5 replicates in the nasal mucosa, and invades the central nervous system (CNS), mainly through the olfactory system. The innate immune response triggered by the host against virus replication via the olfactory route is not fully understood. Studies have found variations in the levels of Toll-Like receptor (TLR) expression in different regions of the bovine central nervous system during acute infection and reactivation of BoHV-1 and BoHV-5 infected bovines. A new perspective to understand the relationship of the pathogen and the host relating the microRNAs (miRNAs) that interact with the innate immune response during neurotropic viral infections. / Doutor

Cat scratch's disease caused by Bartonella henselae, is known to be a self-limited benign process in immunocompetent children. The association with neurologic manifestations is very uncommon especially in patient with no immunologic defects and in cases without specific treatment. A 7 years old male patient, without any immunocompromised defect, presented an atypic presentation of the cat scratch disease. The patient came to the hospital in two opportunities in a status epilepticus, in both cases the diagnosis was encephalitis by Bartonella henselae and the evolution with treatment was monitored with PCR (polymerase chain reaction) in cerebrospinal fluid and blood, as well as IFI (IgM, IgG) serology (indirect immunofluorescence). The patient had a favorable clinical and laboratory evolution for 6 months showing no recurrence of the disease. / This work has been partially supported by the Programa Nacional de Innovacion para la Competitividad y Productividad ´ (Innovate Per ´ u), under the contract 116-PNICP-PIAP-2015.

L’encéphalite Japonaise (EJ) est une maladie zoonotique virale et c’est la principale cause d'encéphalite humaine en Asie et le Pacifique. Elle est due à un Flavivirus, transmis de l’animal à l'Homme par des moustiques, elle peut se transmettre entre porcs par contact direct. Malgré une baisse significative des cas d’EJ dans de nombreux pays suite à la mise en place de programmes de vaccination, l’EJ continue à sévir d’une manière importante en Asie. Notre objectif dans cette thèse est de (i) construire un modèle mathématique de la dynamique de transmission du virus de l’EJ (VEJ), (ii) paramétrer ce modèle pour déterminer l’importance de la transmission directe entre porcs en milieu naturel (iii) et déterminer des stratégies de contrôle. Nous avons développé un modèle de propagation du VEJ. Ensuite, nous avons adapté ce modèle pour avoir deux modèles intégrant la transmission vectorielle seulement ou une combinaison de la transmission vectorielle et directe. Nos résultats montrent que la transmission directe entre porcs pourrait contribuer à la dynamique de transmission du VEJ dans le contexte Cambodgien, toutefois elle ne pourrait pas permettre toute seule une épidémie. Enfin, nous avons considéré la lutte anti-vectorielle, la vaccination des truies et la gestion d’élevages en bandes pour déterminer des stratégies de contrôle pour éradiquer le VEJ au sein des troupeaux de porcs, baisser les avortements des truies, évaluer les risques pour les humains vivant à proximité des fermes et des abattoirs ainsi que le coût-efficacité de la vaccination. Nos résultats confirment que la lutte anti-vectorielle est le meilleur moyen pour contrôler le VEJ. La vaccination des truies gestantes fait diminuer les avortements comme attendu. Paradoxalement, si le contrôle vectoriel est moyen l’efficacité de la vaccination pourrait être compromise. La gestion d’élevages en bandes a un faible impact sur l'incidence et les avortements, par conséquent sur le contrôle de l’EJ. Combiner la vaccination des truies et la lutte anti-vectorielle pourrait être une alternative et/ou une mesure supplémentaire à la vaccination humaine pour réduire à la fois l'incidence de l'EJ chez l'Homme et l'impact économique de l'infection du au VEJ dans les élevages des porcs. / Japanese encephalitis (JE) is a viral zoonotic disease and it is the leading cause of human encephalitis in Asia and the Pacific. Japanese encephalitis virus (JEV) is a Flavivirus of the family of Flaviviridae transmitted from animals to human by mosquitoes, direct transmission between pigs can occur via direct contact. Despite a significant decline in JE cases in many countries as a result of vaccination programs, JE continues to have a significant impact in Asia. Our objective in this thesis is to (i) built a mathematical model of the transmission dynamics of JEV, (ii) parameterize this model to determine the importance of direct transmission between pigs under field conditions (iii) and determine control strategies. We developed a propagation model of JEV. Next, we adapted this model to have two models incorporating vector-borne transmission alone or a combination of vector-borne and direct transmission. Our findings suggest that direct transmission between pigs does contribute to transmission dynamics of JEV in Cambodia; although, alone direct transmission cannot sustain an outbreak. Finally, we considered vector control, sow vaccination, and herd management to determine control strategies to eradicate JEV in pig herds, reduce sow abortions, assess the risk for human beings living in the vicinity of pig herds and near pig slaughterhouse, and the cost-effectiveness of vaccination. Our results confirm that vector control is the best way to control JEV. Vaccination of pregnant sows reduces abortions as expected. Paradoxically, if the vector control is medium the effectiveness of the vaccination could be compromised. Herd management has a low impact on incidence and abortions, therefore on JE control. Combining sow vaccination and vector control could be an alternative and/or an additional measure to human vaccination to reduce both JE incidence in humans and the economic impact of JE infection on pig breeding.

Tregs dienen zur Aufrechterhaltung der Balance im Immunsystem. Die Infektion, Aktivierung oder Induktion von Tregs durch Pathogene kann diese Balance empfindlich stören, eine Immunsuppression zur Folge haben und zur Ausbildung von Autoimmunerkrankungen oder Persistenzen beitragen. Das MV verfügt nicht nur über vielfältige Mechanismen der Immunsuppression, während einer MV-Infektion herrschen zudem Bedingungen vor, welche die Zahl und Aktivität von Tregs beeinflussen könnten. Aufgrund der Expression von Reifungsmarkern auf Trn ist zudem eine präferenzielle Infektion dieser Zellpopulation denkbar. MV-Infektionen können sowohl die akute MV-Enzephalitis, eine Autoimmunerkrankung, nach sich ziehen, als auch die Persistenz SSPE ausbilden. Ob diese Komplikationen mit spezifischen Aberrationen in der Menge und Aktivität von Tregs im Zusammenhang stehen, war bisher nicht bekannt. In dieser Arbeit konnte gezeigt werden, dass auf unstimulierten Trn der Reifungsmarker und MV-Rezeptor CD150 exprimiert wird und es in Folge dessen in vitro zu einer präferentiellen nicht produktiven Infektion und Depletion von Trn kommt. Ex vivo ließ sich ein deutlicher Depletionseffekt während der frühen akuten MV-Enzephalitis nachweisen, der nach Vaczinierung eines gesunden Probanden und Challenge eines immunisierten Affen nicht auftrat. Ob dieser Depletionseffekt ursächlich für die Enzephalitis ist, oder es sich um einen Begleiteffekt handelt ließe sich an Modellorganismen durch mitogene Manipulation der Trn während einer MV-Infektion untersuchen. Auch bei SSPE kann es zu einer Depletion von Trn kommen, dies scheint jedoch nicht mit der Progression dieser Erkrankung im Zusammenhang zu stehen. Wahrscheinlich ist dagegen ein Zusammenhang mit der Induktion von Tregs. In MV-stimulierten Proben von SSPE-Patienten wurde im Mittel signifikant mehr IL-10 exprimiert als in den Kontrollen. In Proben seropositiver gesunder Spender wurde IL-10 in den ersten Stunden nach MV-Stimulation fast ausschließlich von induzierten Tregs exprimiert. Weitere Versuche sind nötig, um die Evidenz zu steigern und zu ermitteln, ob auch in Patientenproben die frühe IL-10 Expression nach MV-Stimulation von induzierten Tregs dominiert wird. Zusammenfassend kann gesagt werden, dass es sowohl bei der MV-Enzephalitis als auch bei SSPE zu signifikanten Wechselwirkungen mit Tregs kommt. Ob sich eine MV-Enzephalitis auch ohne Depletion von Trn ausbilden kann und ob die Ausbildung von SSPE erhöhte IL-10 Expression voraussetzt, werden weitere Untersuchungen ergründen müssen. / Treg are supposed to keep the balance throughout the immune system. Infection, activation and induction of Treg by pathogens can interrupt with this balance. Immunosuppression autoimmunity and viral persistence can result from this interference. MV does not only cause immunosuppression during infection by multifaceted mechanisms, but also effects circumstances known to interfere with the frequency and activity of Treg. Due to the expression of maturity markers on the surface of Trn a preferential infection of this cell population by MV seems possible. MV-infection can involve both, acute MV-encephalitis, an autoimmune disease, and the virus persistence SSPE. It was not investigated until now, if thous complications are associated to specific aberrations in the frequency and activity of Treg. In this paper it was demonstrated that CD150, which is both a maturity marker and a MV-receptor, is expressed on unstimulated Trn. Due to this expression the Trn are infected preferentially and non productively in vitro leading to apoptosis. Ex vivo a noticeable depletion effect was detected during the early acute MV-encephalitis. This effect did not accure after vaccination of a healthy proband, and the challenge of an immunised monkey. Mitogenic manipulation of Trn in model organisms during MV-infection could give advice, if this depletion effect is causal to MV-Encephalitis or rather a concomitant effect. Depletion of Trn can also arise in the presence of SSPE, but this seems not to interfere with the progression of disease. By contrast there is presumable an interrelation of SSPE with the induction of Tregs. In MV-stimulated probes from SSPE-patients the median IL-10 expression was significantly higher than in controls. Probes from seropositive healthy donators were used to identify the IL-10 expressing cells. During the first hours after MV-stimulation IL-10 was mainly expressed by induced Treg. Subsequent investigations are necessary to enhance the evidence and to determine if induced Treg also dominate the early IL-10 expression after MV-stimulation in patient probes. To give a resume you could claim that there are significant interrelations between MV-encephalitis respectively SSPE and Treg. If a depletion of Trn is necessary for the development of MV-encephalitis and if increased levels of IL-10 expression are required for the formation of SSPE has to be examined in further experiments.

Stress is known to alter immune function, both in positive and negative ways. The disparate effects of stress on immune function remains an active area of investigation. This thesis investigates how the application of social disruption stress either prior to or concurrent with infection alters the neuropathogenesis of Theiler's murine encephalitis virus. Experiment 1 verified that social disruption prior to infection exacerbated the course of infection. Experiment 2 examined application of social disruption concurrent with infection, and found that this may produce a delay in symptom onset, and possibly a protective effect. Experiment 3 directly compared the two schedules to each other. The previous findings were replicated and expanded with additional measures (both behavioral and physiological) that further verified the earlier findings. Social disruption applied prior to infection resulted in greater behavioral and physiological exacerbation of the disease. Concurrently applied stress remained protective or inhibitory in the disease progression. Timing of stress is one of several quantitative aspects of stress that has been found to impact the stress-immune interaction and should be further investigated.

L'encéphalite herpétique (EH), causée par l'herpès simplex virus-1 (HSV-1), peut résulter de défauts monogéniques de l'immunité médiée par TLR3. L'induction d'interférons (IFNs)-α/β ou -λ via TLR3 est cruciale à la protection après infection primaire avec HSV-1 dans le système nerveux central (SNC). Nous décrivons deux enfants avec l'EH portant différentes mutations hétérozygotes (D50A et G159A) dans TBK1, encodant TANK-Binding Kinase 1, une kinase aux carrefours de multiples voies de signalisation induisant des IFNs. Les deux allèles mutants de TBK1 sont perte-de-fonction par des mécanismes différents: instabilité de la protéine (D50A) ou perte d'activité kinase (G159A). Ces allèles sont associés à un trait autosomal dominant (AD) par des mécanismes différents: haplotype-insuffisance (D50A) ou dominance négative (G159A). Un défaut de réponses à poly(I:C) par TLR3 est observable dans les fibroblastes hétérozygotes pour G159A, et non pour D50A TBK1. Néanmoins, la réplication virale et la mortalité cellulaire après infection par deux virus dépendants de TLR3 (HSV-1 et VSV) étaient élevées dans les fibroblastes des deux patients. Ces phénotypes peuvent être sauvés par IFN-α2b. De plus, la production d'IFNs en réponse à des agonistes et virus indépendants de TLR3 est maintenue dans les PBMCs et fibroblastes des patients. Le phénotype cellulaire restreint, partiel représente ainsi le phénotype clinique de ces patients, limité à l'EH. Ces données identifient la déficience partielle AD de TBK1 comme une nouvelle étiologie génétique de l'EH de l'enfance, et indiquent que TBK1 est essentiel pour le contrôle de HSV-1 dans le SNC, médié par TLR3 et dépendant des IFNs

One of the key events in a virus-infected host cell is the activation and repression of a large number of host genes. In recent years, such differentially expressed host genes have been identified for several viruses, bacteria and parasites. Such studies indicate that reprogramming of host transcriptome during infection by a pathogen is a major component of host response and many of the reprogrammed genes may promote or prevent pathogen infection or may contribute to pathogen-induced pathological changes. Host gene expression changes have been studied for a number of viruses in cell lines. However, in case of neurotropic viruses which infect nonrenewable populations of central nervous system (CNS), changes in the host gene expression need to be studied in the intact host rather than cells grown in culture. Since such studies are reported only for a few neurotropic viruses, an attempt has been made in this thesis to identify and characterize genes that are differentially expressed in the mouse brain during infection by Japanese encephalitis virus (JEV) and rabies virus. Using subtraction hybridization technique, subtraction cDNA libraries were generated representing mRNAs that are induced or repressed in the mouse brain during JEV infection. Sequence analysis of the 350 isolated clones resulted in the identification of 73 unique genes. Out of these, 66 were of forward library clones (upregulated genes) and 7 of reverse library clones (downregulated genes). The forward library clones was clustered in different functional groups such as, proteins involved in immune response and interferon-inducible proteins, GTPase and GTP binding proteins, transcriptional regulators, enzymes, ribosomal proteins, neuronal proteins, carrier proteins, DNA-binding proteins, miscellaneous and proteins of unknown function. The differential expression of all these genes was further validated by northern blot analysis of brain RNA isolated from normal and JEV-infected mice, which indicate that out of 66 forward library clones 33 were genuinely upregulated in JEV-infected mouse brain, whereas all 7 reverse library clones were repressed in JEV infection. Since vaccination is known to prevent virus replication in the brain, host gene expression changes in mice immunized with BIKEN JE vaccine was also examined. There was a good correlation between inhibition of JEV replication and reduced expression of JEV-inducible CNS genes in the vaccinated mice. To check whether JEV-induced CNS genes identified in this study are specific to JEV or can be induced by any other neurotropic virus, expression patterns of 15 randomly chosen genes were checked in RV infected mouse brain. Results indicated that all the chosen genes are modulated in the same way during RV infection as well. Comparison of JEV-induced gene expression changes with those induced by other neurotropic viruses indicated that 83% of the JEV-inducible mouse CNS genes are also induced by Sindbis virus, a neurotropic virus of the family alphaviridae, indicating that despite diverse life cycles, these two viruses may activate common host signaling pathways. This study also led to the identification of 9 unique JEV-inducible genes (LRG-21, VHSV induced gene1, Tpt1, SLC25A3, Olfm1, Ina/NF-66, Dst/Bpag1, Mdm2 and Gbp5) which are not reported to be activated by any other neurotropic virus. Since it is beyond the scope of this study to characterize all the JEV-induced and repressed genes, two genes were chosen for a detailed analysis. These are: JEV-inducible gene encoding GARG-39 protein which is a member of the glucocorticoid attenuated response gene family and an unannotated, JEV-repressible gene designated in this study as clone # 137. The gene encoding GARG-39 identified as a JEV-inducible gene in this study was originally discovered as lipopolysaccharide- and interferon-inducible gene in macrophages. This protein contains tetratricopeptide repeat (TPR) motifs that are known to be involved in protein-protein interactions. However, the function of this protein remains unknown till date. Therefore the gene was cloned and over-expressed in E. coli and antibodies were raised against the recombinant protein. Western blot analysis revealed that GARG-39 protein is detectable only in JEV-infected but not in the normal mouse brain. Surprisingly, immunoflourescence studies carried out in NIH3T3 cells revealed that GARG-39 is localized in the cytosol of normal cells and it colocalizes with α-tubulin in the mitotic spindle in a small fraction of cells which are in the mitotic stage. Further, in an in vitro assay, GARG-39 was found to interact with taxol-stabilized tubulin polymers. Since microtubules are known to play an important role in virus assembly, it is possible that GARG-39 may have a role in virus assembly and maturation. Alternatively, microtubule-associated proteins are implicated in several neurodegenerative disorders including Parkinson’s, Alzheimer’s and mental retardation and therefore, a role for GARG-39 in virus-induced neuropathogenesis cannot be ruled out. In addition, the expression of GARG-39 in normal dividing cells in the culture indicates a role for this protein in mitosis. In a normal mouse brain, mitotically active cells are very low in number and hence GARG-39 expression (both at the RNA and protein levels) is below the detection limits. JEV infection may trigger mitotic activity in brain leading to increased expression of GARG-39. One of the cDNA clones identified in this study, designated as clone # 137, hybridized to a ~2.6 kb transcript which was found to be down regulated in the mouse brain by JEV as well as rabies virus. A series of investigations led to the conclusion that clone #137 corresponds to the 3′ end of a ~2.6 kb transcript encoding mouse calcium calmodulin kinase inhibitor II α (mCaMKIINα). Interestingly, only the α isoform but not the β isoform of mCaMKIINα mRNA is down regulated in the mouse brain during JEV infection. Since the physiological function of mCaMKIINα is not known, the gene encoding 8 kDa mouse mCaMKIINα open reading frame was cloned into an E. coli expression vector and antibodies were raised against the purified recombinant protein. Surprisingly, antibodies raised against the ~8 kDa recombinant mouse CaMKIINα reacted with a ∼37 kDa mouse brain protein. This protein designated as CaMKIINα-immunoreactive protein (CaMKIINα-IRP) is also down regulated during JEV infection and is localized in the post synaptic density (PSD) of normal mouse brain. In addition, distinct changes are also observed in the subcellular localization and phosphorylation of CaMKIIα leading to an increase in cytosolic CaMKII activity in JEV-infected mouse brain. The differential regulation of CaMKIIα and CaMKIINα during JEV infection suggests a possible role for CaMKII signaling pathway in JEV infection and/or JEV-induced neuropathogenesis in the CNS. Conclusions: • A number of host genes whose expression is modulated in the mouse brain during JEV and/or rabies virus infection have been identified. • One of the JEV-inducible genes encoding the GARG-39 protein was shown to be a microtubule-associated protein with a possible role in mitosis. • One of the JEV-repressible genes was found to encode the mouse CaMKIINα mRNA. • A novel JEV-repressible ∼37 kDa protein immunoreactive to antibodies raised against the recombinant CaMKIINα was identified in the post synaptic density of the mouse brain.