The anti-pneumococcal function of native C-reactive protein (CRP) involves its binding to phosphocholine molecules present on Streptococcus pneumoniae and subsequent activation of the complement system. However, when pneumococci recruit complement inhibitory protein factor H on their surface, they escape complement attack. Non-native forms of CRP have been shown to bind immobilized factor H. Accordingly, we hypothesized that modified CRP would bind to factor H on pneumococci, masking its complement inhibitory activity, allowing native CRP to exert its anti-pneumococcal function. As reported previously, native CRP protected mice from lethal pneumococcal infection when injected 30 minutes before infection but not when injected 24 hours after infection. However, a combination of native and mutant CRP was found to protect mice even when administered 24 hours after infection. Therefore, it is concluded that while native CRP is protective only against early-stage infection, a combination of native and mutant CRP offers protection against late-stage infection.

Herpes simplex virus (HSV) infection of the cornea leads to a blinding immuno-inflammatory condition of the eye also called stromal keratitis (SK). SK immunopathology is characterized by the infiltration of CD4+ T cells of Th1 phenotype as well as the development of new blood vessels into the normally avascular cornea. Studies in mouse models of SK have firmly established the role of CD4+ T cells, and particularly of Th1 phenotype, as the principal mediators of SK immunopathology. However, with the recent discovery of IL-17A and Th17 cells, the role of this cytokine as well as Th17 cells remains to be further defined. Recently it was shown that the normal cornea expresses VEGF-A, however its biological activity is impeded by its binding to a soluble form of VEGF-A receptor-1 (sVEGFR-1). Past studies have implicated the role of vascular endothelial growth factor-A (VEGF-A) in HSV induced corneal angiogenesis, however the source of VEGF-A as well as molecular mechanisms, particularly in the context of VEGF-A/sVEGFR-1 balance during HSV infection, are poorly understood. The first part of this dissertation (I) reviews past literature on HSV induced corneal SK immunopathology. It focuses on the understanding of HSV-1 induced events that particularly results in corneal angiogenesis as well as tissue damage mediated by different type of cells as well as their secreted products. The next three parts (II-IV) focus on the mechanisms of HSV induced corneal angiogenesis as well as the relative role of Th1 and Th17 cells in SK immunopathology. Results in part II focuses on the relative role of IFN-γ/IL-17 as well as Th1/Th17 cells in HSV induced corneal immunopathology. The third section evaluate the significance of VEGF-A/sVEGFR-1 balance in HSV induced corneal neovascularization. Results in part IV focus on the role of IL-17A in altering the balance between VEGF-A and sVEGFR-1 post ocular HSV infection and subsequent corneal angiogenesis. Collectively these studies identified novel mechanisms by which HSV infection of the cornea leads to the development of angiogenesis as well as corneal tissue damage and subsequent SK immunopathology, the most common cause of infectious blindness in the Western World.

Submitted by Mario BC (mario@bc.ufrpe.br) on 2016-06-17T12:26:34Z No. of bitstreams: 1 Victor Hugo de Vasconcelos Calado.pdf: 593050 bytes, checksum: ab20bdddfa55a2c22cb9e115c16dbb93 (MD5) / Made available in DSpace on 2016-06-17T12:26:34Z (GMT). No. of bitstreams: 1 Victor Hugo de Vasconcelos Calado.pdf: 593050 bytes, checksum: ab20bdddfa55a2c22cb9e115c16dbb93 (MD5) Previous issue date: 2016-03-11 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Mycotoxins have been a problem in poultry production to be present in the major ingredients (corn and soybean meal) that make up the poultry feed, leading to problems such as an inadequate use of food and reduction of animal front immunity to various pathogens. Thus it aimed to evaluate the effects of adding mycotoxin adsorbents in broiler diets naturally contaminated with aflatoxin and fumonisin, on the parameters: histopathology, biometric and serological. The experiment was conducted with 60 birds, seven-day-old Cobb commercial line in three treatments: T1 - control (not including mycotoxin adsorbents in diet); T2 - adding 0.5 kg / t. of adsorbent A and T3 inclusion of 1.5 kg / t of adsorbent B. The broilers receive in all treatments, isonutritives diets naturally contaminated by mycotoxins. These broilers were raised up to 60 days old when was made serology tests for NDV and IBDV, and after were sacrificed for histopathologic and biometric analysis. The results were submitted to analysis of variance (ANOVA) with significance level of 5% probability and Tukey test. There were significant differences between treatments (P <0.05) in body weight. The body weight was significantly different between T1 and T2 (P = 0.01400), with a higher weight of the broilers receiving the adsorbent (4.26 ± 0.37). Among the organs analyzed, only the weight of the cecal tonsil significant difference between T1 and T2 (P <0.05; P = 0.03008), and T1 (5,20g ± 1.239) had an average weight slightly higher than average weight of T2 (4,05g ± 1.208). The amounts of immunoglobulins to IBDV showed significantly higher concentrations in T2 (P = 0.041). This contamination of broilers aflatoxin and fumonisin caused histopathological lesions in immune organs, liver and kidneys. However adsorbents used A and B reversed in parts of the lesions, especially in the liver, bursa and thymus. This reversal of lesions led to improved serological tests for IBD (Gumboro bursal-infectious disease) in the group treated with the adsorbent, resulting in broilers with better performance, suggesting that this adsorbent showed better effect on broilers in field conditions. / As micotoxinas têm sido um problema na produção avícola por estarem presentes nos principais ingredientes (milho e farelo de soja) que compõem a ração para aves, levando a problemas como: inadequado aproveitamento dos alimentos e diminuição de imunidade animal frente a patógenos diversos. Assim, objetivou-se avaliar os efeitos da adição de adsorventes de micotoxinas, em dietas de frangos de corte contaminadas naturalmente com aflatoxinas e fumonisinas, sobre os parâmetros: biométricos, sorológicos e histopatológicos. O experimento foi realizado com 60 aves, com sete dias de idade, da linhagem comercial Cobb distribuídas em três tratamentos: T1 – Controle (sem inclusão de adsorventes de micotoxinas na dieta); T2 – inclusão de 0,5 kg/t do adsorvente A (composto por aluminossilicato de sódio e cálcio modificado industrialmente) e T3- inclusão de 1,5 kg/t do adsorvente B(composto por aluminossilicato de sódio e cálcio). As aves receberam, em todos os tratamentos, dietas isonutritivas, feitas com milho sabidamente contaminado, em campo por micotoxinas. Essas aves foram criadas até 60 dias de idade, quando foi realizada sorologia para NDV(vírus da doença de Newcastle) e IBDV(vírus da doença infecciosa bursal) e preparadas para eutanásia para posteriores análises histopatológicas e biométricas. Ao final, o peso vivo foi significativamente diferente entre os tratamentos T1 e T2 (P=0,01400), observando-se maior peso das aves que receberam o adsorvente A (4,26 ± 0,37). Entre os órgãos analisados, apenas o peso da tonsila cecal apresentou diferença significativa entre os tratamentos T1 e T2 (P<0,05; P=0,03008), sendo que T1 (5,20g ± 1,239) apresentou peso médio levemente superior ao peso médio do T2 (4,05g ± 1,208). No teste sorológico, as quantidades de imunoglobulinas para IBDV apresentaram concentrações significativamente maiores no T2 (P=0,041). A intoxicação das aves com aflatoxinas e fumonisinas provocou lesões histopatológicas nos órgãos linfóides (bolsa cloacal, baço, timo e tonsilas cecais), fígado e rins. Contudo os adsorventes usados A e B minimizou as lesões, principalmente no fígado, bursa, e timo. A menor intensidade das lesões proporcionou melhores resultados sorológicos para IBDV no grupo tratado com o adsorvente A, resultando em aves com melhor desempenho, conclui-se sugerindo que este adsorvente produz melhor efeito nas aves em condições de campo.

INTRODUÇÃO: A Leishmaniose Tegumentar Americana (LTA) é uma doença infecciosa endêmica no Brasil, causada por protozoários do gênero Leishmania e possui duas formas clínicas principais, a leishmaniose cutânea (LC) e a leishmaniose mucocutânea (LMC). Os macrófagos têm papel crucial na patogênese da Leishmaniose como hospedeiros do parasita e atuam como células apresentadoras de antígenos, promovendo uma resposta imune de perfil Th1 contra a Leishmania. Os macrófagos polarizados M2, relacionados com resposta anti-inflamatória (Th2), são envolvidos no controle da inflamação e dano tecidual em várias doenças e estão associados à cronicidade nas doenças infecciosas. O objetivo deste trabalho foi verificar a participação dos macrófagos M2 nos sítios de lesão cutânea da LTA MÉTODOS: Sessenta e três biópsias de pele de lesões de LTA, obtidas de 48 doentes com LC e 15 de LMC, foram submetidas ao método imuno-histoquímico com os anticorpos anti-CD163 e anti-CD206, marcadores de macrófagos M2. Dez espécimes foram também submetidos à técnica imuno-histoquímica de dupla marcação com a utilização dos marcadores pSTAT-1 e CD68 para identificação de macrófagos M1 e CMAF e CD163 para identificação de macrófagos M2. RESULTADOS: Os espécimes de pele com reação inflamatória difusa (n = 26) exibiram maior número de células imunomarcadas com CD163, quando comparadas ao grupo com reação granulomatosa bem organizada (n = 37) (p= 0,01). Os macrófagos CD163+ também foram mais numerosos nas lesões de pele com a presença de formas amastigotas de Leishmania (n = 39) ao exame histopatológico (p=0,02), quando comparadas às lesões onde os parasitas não foram observados (n = 24). O mesmo ocorreu quando comparados somente os espécimes do grupo de doentes com LC com a presença de parasitas (n = 31) e ausência dos mesmos (n = 17) (p = 0,04). As lesões de pele de doentes com LMC mostraram maior número de células CD206+ (n = 15) que a de doentes com LC (n = 48) (p=0,008). Houve correlação positiva entre o número de células imunomarcadas com os anticorpos CD163 e CD206 (r de Spearman= 0,369). Os macrófagos +pSTAT1/CD68+ (M1) mostraram-se mais numerosos que os macrófagos CMAF+/CD163+ (M2) nos sítios de lesão cutânea da LTA. CONCLUSÕES: Os resultados obtidos sugerem que os macrófagos M2 têm um papel na resposta imune \"in situ\" da LTA. Essas células devem atuar como células alvo, facilitando a entrada dos parasitas, a progressão da doença e parecem estar envolvidos nos mecanismos de cronicidade e nos processos de remodelamento tecidual dessa doença. As moléculas CD163 e CD206 podem ser consideradas bons marcadores teciduais de macrófagos M2, uma vez que mostraram correlação positiva em sua expressão. A técnica de dupla marcação confirmou a presença dos macrófagos M2 nas lesões cutâneas da LTA. Embora ocorra a presença de macrófagos M2, os macrófagos M1 são a população macrofágica predominante da resposta imune \"in situ\" da LTA / INTRODUCTION: American tegumentary leishmaniasis (ATL) is an endemic infectious disease in Brazil, caused by Leishmania parasites and it has two main clinical forms, cutaneous leishmaniasis (CL) and mucocutaneous leishmaniasis (MCL). Macrophages play a key role in leishmaniasis pathogenesis. They are definite parasite host and act as antigen presenting cells, eliciting a Th1 pattern of immune response (M1) against Leishmania. M2 polarized macrophages, related to an anti-inflammatory response (Th2), are involved in controlling inflammation and tissue damage in several diseases and are related to chronicity in infectious diseases. The aim of this study was verifying M2 macrophages \"in situ\" participation in ATL. METHODS: Sixty-three skin biopsies from LTA lesions, obtained from patients with CL (n=48) and MCL (n=15), were subjected to imunohistochemical technique with M2 macrophages markers CD163 and CD206 antibodies. Ten samples were selected for double staining technique with pSTAT1 and CD68 markers for M1 identification, and CMAF and CD163 markers for M2 macrophages identification. RESULTS: Skin samples displaying diffuse inflammatory reaction (n = 26) exhibited higher number of CD163 immune stained macrophages when compared to the well-organized granulomatous reaction group (n = 37) (p=0.01). CD163+ macrophages were higher in samples displaying Leishmania parasites (n = 39) at histopathology exam than the samples without parasites (n = 24) (p=0.02). Same result was observed when comparing the lesions of CL lesions with (n = 31) and without (n = 17) parasites (p = 0.04). MCL skin lesions (n = 15) showed higher number of CD206+ cells (p = 0.008) in comparison with skin lesions taken from CL patients (n = 48). Spearman test demonstrated a positive correlation between the number of CD163+ and CD206+ immune stained cells (Spearman r = 0,369). M1 macrophages (pSTAT1+/CD68+) were present in higher number when compared to M2 macrophages (CMAF+/CD163+) in the samples studied. CONCLUSIONS: The results suggest that M2 macrophages play a role in the in situ immune response of ATL. M2 polarized macrophages may act as host target cells facilitating parasites entry and promoting disease progression, but also seem to be involved with chronicity and tissue remodeling of ATL lesions. CD163 and CD206 molecules may be considered as good markers for M2 macrophages. Double staining technique confirmed the presence of M2 macrophages, although M1 macrophages are the predominant macrophagic component in skin lesions of ATL

Células T reguladoras (Treg) são cruciais na tolerância periférica e no controle da inflamação. Nós usamos dois modelos bem estabelecidos de tolerância de mucosas para a asma alérgica e a tolerância inalatória local induzida pela exposição crônica a OVA para estudar o aparecimento e função das Treg. Nós mostramos que a tolerância nasal distinguiu da tolerância oral pela produção sistêmica de IgG1 e desenvolvimento da inflamação alérgica na cavidade peritoneal ou pela indução da inflamação das vias aéreas de camundongos RAG-/- reconstituídos com células T CD4+ após desafios com OVA. Observamos também que Treg Foxp3+ migraram para o pulmão alérgico e expressaram fenótipo de ativação e memória que distinguiu essas células das Treg presentes nos linfonodos drenantes. Células T CD4+CD25+ do pulmão dos animais alérgicos suprimiram a proliferação das células T CD4+CD25-, mas não a produção de citocinas Th2. Finalmente, a exposição crônica a OVA levou ao aumento da apoptose de eosinófilos que infiltraram o pulmão resultando na resolução da inflamação alérgica pulmonar. / Regulatory T cells (Treg) are critical for peripheral tolerance and control of inflammation. We used two well established models of mucosal tolerance to allergic airway disease and the local inhalational tolerance induced by chronic OVA exposure to study the appearance and function of Treg cells. We found that nasal tolerance distinguished from oral tolerance by systemic IgG1 antibody production and development of allergic inflammation in the peritoneal cavity or by induction of airway inflammation in RAG-/- mice reconstituted with CD4+ T cells after OVA challenge. We also found that Foxp3+ T cells migrated to allergic lung and expressed an effector/memory phenotype that distinguished them from Treg cells present in lung draining lymph nodes. Lung infiltrating CD4+CD25+ T cells from allergic mice suppressed CD4+CD25- T cell proliferation but not Th2 cytokines production by these cells. Finally, chronic OVA exposure leaded to increased apoptosis of infiltrating lung eosinophils resulting in the resolution of allergic lung inflammation.

Mycobacterium tuberculosis, the causative agent of tuberculosis, can manipulate host cell death pathways as virulent strains inhibit apoptosis to protect its replication niche and induce necrosis as a mechanism of escape. In vitro studies revealed that similar to lytic viruses, M. tuberculosis has the ability to induce cytolysis in macrophages when it reaches an intracellular burden of ~25 bacilli. Base on this finding, we proposed the burst size hypothesis that states when M. tuberculosis invades a macrophage at a low multiplicity of infection it replicates to a burst size triggering necrosis to escape the cell and infect naïve nearby phagocytes, propagating the spread of infection. The first part of this study investigated if the in vitro observations of M. tuberculosis cytolysis were relevant to cell death of infected phagocytes during pulmonary tuberculosis in vivo. Mice infected with a low dose of M. tuberculosis revealed during TB disease, the major host cell shifted from one type of phagocyte to another. Enumeration of intracellular bacilli from infected lung cells revealed the predictions of the hypothesis were confirmed by the distribution of bacillary loads across the population of infected phagocytes. Heavily burdened cells appeared nonviable sharing distinctive features similar to infected macrophages from in vitro studies. Collectively, the data indicates that M. tuberculosis triggers necrosis in mononuclear cells when its number reaches the threshold burst size. The previous study showed during the period of logarithmic bacterial expansion, neutrophils were the primary host cell for M. tuberculosis coinciding with the timeframe of the highest rate of burst size necrosis. The second part of this study examined this link by infecting mice with one of four different M. tuberculosis strains ranging in virulence. Mice infected with the most virulent strain had the highest bacterial burden and elicited the greatest number of infected neutrophils with the most extensive lung inflammation and greater accounts of cell death. Treating these mice with a bacteriostatic agent decreased the bacterial load and infected neutrophils in a dose-dependent manner indicating necrosis induced by virulent M. tuberculosis recruited neutrophils to the lungs. Infected neutrophils can serve as a biomarker in tuberculosis as evidenced by poorly controlled infection and increased severity of lung immune pathology.

The dynamics of T cell responses have been extensively studied during single virus infection of naïve mice. During a viral infection, viral antigen is presented in the context of MHC class I molecules on the surface of infected cells. Activated CD8 T cells that recognized viral antigens mediate clearance of virus through lysis of these infected cells. We hypothesize that the balance between the replicating speed of the virus and the efficiency at which the T cell response clears the virus is key in determining the disease outcome of the host. Lower T cell efficiency and delayed viral clearance can lead to extensive T cellmediated immunopathology and death in some circumstances. To examine how the efficiency of the immune response would impact immunopathology we studied several viral infection models where T cell responses were predicted to be less than optimal: 1. a model of co-infection with two viruses that contain a crossreactive epitope, 2. a viral infection model where a high dose infection is known to induce clonal exhaustion of the CD8 T cell response, 3. a neonatal virus infection model where the immune system is immature and 4. A model of beneficial heterologous immunity and T cell crossreactivity where mice are immunized as neonates when the T cell pool is still developing. Model 1. Simultaneous co-infections are common and can occur from mosquito bites, contaminated needle sticks, combination vaccines and the simultaneous administration of multiple vaccines. Using two distantly related arenaviruses, lymphocytic choriomeningitis virus (LCMV) and Pichinde virus (PICV), we questioned if immunological T cell memory and subsequent protection would be altered following a simultaneous co-infection, where two immune responses are generated within the same host at the same time. Coinfection with these two viruses, which require CD8 T cell responses to clear, resulted in decreased immune protection and enhanced immunopathology after challenge with either virus. After primary co-infection, each virus-specific immune response impacted the other as they competed within the same host and resulted in several significant differences in the CD8 T cell responses compared to mice infected with a single virus. Co-infected mice had a dramatic decrease in the overall size of the LCMV-specific CD8 T cell response and variability in which virus-specific response dominated, along with skewing in the immunodominance hierarchies from the normal responses found in single virus infected mice. The reduction in the number of LCMV-specific CD8 memory T cells, specifically cells with an effector memory-like phenotype, was associated with higher viral loads and increased liver pathology in co-infected mice upon LCMV challenge. The variability in the immunodominance hierarchies of co-infected mice resulted in an enhanced cross-reactive response in some mice that mediated enhanced immune-mediated fat pad pathology during PICV challenge. In both viral challenge models, an ineffective memory T cell response in co-infected mice facilitated increased viral replication, possibly leading to enhanced and prolonged accumulation of secondary effector T cells in the tissues, thereby leading to increased immune pathology. Thus, the magnitude and character of memory CD8 T cell responses in simultaneous co-infections differed substantially from those induced by single immunization. This has implications for the design of combination vaccines and scheduling of simultaneous immunizations. Model 2. The balance between protective immunity and immunopathology often determines the fate of the virus-infected host. Several human viruses have been shown to induce a wide range of severity of disease. Patients with hepatitis B virus (HBV), for example, show disease progression ranging from acute resolving infection to a persistent infection and fulminant hepatitis. Certain rapidly replicating viruses have the ability to clonally exhaust the T cell response, such as HBV and hepatitis C virus (HCV) in humans and the clone 13 strain of LCMV in mice. How rapidly virus is cleared is a function of initial viral load, viral replication rate, and efficiency of antigen-specific T cells. By infecting mice with three different inocula of LCMV clone 13, we questioned how the race between virus replication and T cell responses could result in different disease outcomes. A low dose of LCMV generated efficient CD8 T effector cells, which cleared the virus with minimal lung and liver pathology. A high dose of LCMV resulted in clonal exhaustion of T cell responses, viral persistence and little immunopathology. An intermediate dose only partially exhausted the CD8 T cell responses and was associated with significant mortality, and the surviving mice developed viral persistence and massive immunopathology, including necrosis of the lungs and liver. This was a T cell-mediated disease as T cell-deficient mice had no pathology and became persistently infected like mice infected with a high dose of LCMV clone 13. This suggests that for non-cytopathic viruses like LCMV, HCV and HBV, clonal exhaustion may be a protective mechanism preventing severe immunopathology and death. Model 3. Newborns are more susceptible to infections due to their lack of immunological memory and under-developed immune systems. Passive maternal immunity helps protect neonates until their immune systems have matured. We questioned if a noncytolytic virus that produces strong T cell responses in adult mice would also induce an equally effective response in neonatal mice. Neonates were infected with very low doses of LCMV Armstrong and surprisingly the majority succumbed to infection between days 7-11, which is the peak of the T cell response in adult mice infected with LCMV. Death was caused by T cell-dependent pathology and not viral load as 100% of T cell deficient neonates survived with minimal lung and liver pathology. This is similar to the adult model of medium dose LCMV clone 13, but T cell responses in neonates were not partially clonal exhausted. Furthermore, surviving neonates were not persistently infected, clearing virus by day 14 post infection. In adult mice direct intracranial infection leads to LCMV replication and CD8 T cell infiltration in the central nervous system (CNS), causing CD8 T cell-mediated death. However, this does not occur in adults during LCMV intraperitoneal (ip) infections. We questioned if unlike adults LCMV could be gaining access to the CNS in neonates following ip infection. Replicating LCMV was found in the brain of neonates after day 5 post infection along with virus-specific CD8 T cells producing IFNγ at day 9 post infection. Neonates lacking perforin had complete survival when followed until day 14 post infection, suggesting perforin-mediated T cell-dependent immunopathology within the CNS of neonates was causing death after LCMV infection. Passive immunity from LCMV-immune mothers also protected 100% of pups from death by helping control viral load early in infection. We believe that the maternal antibody compensates for the immature innate immune response of neonates and controls viral replication early so the neonatal T cell response induced less immunopathology. Neonates are commonly thought to have less functional immune systems, but these results show that neonates are capable of producing strong T cell responses that contribute to increased mortality. Model 4. Due to their enhanced susceptibility to infection neonatal and infant humans receive multiple vaccines. Several non-specific effects from immunizations have been observed, for example, measles or Bacillus Calmette- Guerin (BCG) vaccines have been linked to decreased death of children from infections other than measles virus or tuberculosis. These studies mirror the concepts of beneficial heterologous immunity, where previous immunization with an unrelated pathogen can result in faster viral clearance. LCMV-immune mice challenged with vaccinia virus (VV) have lower viral loads then naïve mice and survive lethal infections, but some mice do develop fat pad immunopathology in the form of panniculitis or acute fatty necrosis (AFN). We questioned how immunological T cell memory formed during the immature neonatal period would compare to memory generated in fully mature adults during a heterologous viral challenge. Mice immunized as neonates had comparable reduction in VV load and induction of AFN, indicating that heterologous immunity is established during viral infections early in life. Interestingly, the LCMV-specific memory populations that expanded in mice immunized as neonates differed from that of mice immunized as adults. In adult mice 50% of the mice have an expansion of LCMVNP205- specific CD8 T cells while the majority of neonates expanded the LCMVGP34- specific CD8 T cell pool. This alteration in dominant crossreactivities may be due to the limited T cell receptor repertoire of neonatal mice. In naïve neonatal mice we found altered Vβ repertoires within the whole CD8 T cell pool. Furthermore, there was altered Vβ usage within virus-specific responses compared to adult mice and a wide degree of variability between individual neonates, suggesting enhanced private specificity of the TCR repertoire. Beneficial heterologous immunity is maintained in neonates, but there was altered usage of crossreactive responses. As neonatal mice were found to be so sensitive to LCMV infection we questioned if neonates could control another arena virus that did not replicate as efficiently in mice, PICV. Unlike LCMV infection, neonatal mice survived infection with PICV even with adult-like doses. However, viral clearance was protracted in neonates compared to adults, but was cleared from fat pad and kidney by day 11 post infection. The peak of the CD8 T cell response was similarly delayed. PICV infected neonates showed dose-dependent PICV-specific CD8 T cell responses, which were similar to adult responses by frequency, but not total number. As with LCMV infection there were changes in immunodominance hierarchies in neonates. Examination of the immunodominance hierarchies of PICV-infected neonates showed that there were adult-like responses to the dominant NP38- specific response, but a loss of the NP122-specific response. Six weeks post neonatal infection mice were challenged with LCMV Armstrong and there was a strong skewing of the PICV immunodominance hierarchy to the crossreactive NP205-specific response. These data further support the hypothesis that heterologous immunity and crossreactivity develop following neonatal immunization, much as occurs in adults, although TCR repertoire and crossreactive patterns may differ. Changing the balance between T cell efficiency and viral load was found to altered the severity of the developing immunopathology after viral infection.

Preclinical models of lupus indicate that T cell-B cell collaboration drives antinuclear antibody (ANA) production and sustains T cell activation. Autoreactive B lymphocytes are present in the normal repertoire but persist as ignorant or anergic cells. Mechanisms that normally limit T cell activation of autoreactive B cells remain incompletely resolved, but potentially include the absence of autoreactive effector T cell subsets and/or the presence of autoAgspecific regulatory T cells (Tregs). Several studies have addressed this issue by using experimental systems dependent on transgenic autoreactive B cells, but much less is known about the activation of autoreactive B cells present in a polyclonal repertoire. In the second chapter of this thesis, I have explored the role of effector T cells and Tregs using mice that express an inducible pseudoautoAg expressed on B cells and other antigen presenting cells (APCs). In this system, activated Th2 cells, but not naïve T cells, elicit the production of ANAs, but ANA production is severely limited by autoAg-specific Tregs. Bone marrow chimera experiments further demonstrated that this B cell activation is constrained by radioresistant autoantigen-expressing APCs (rAPC) present in the thymus as well as by non-hematopoietic stromal cells located in peripheral lymphoid tissue. Importantly, peripheral rAPC expression of autoAg induced the expansion of a highly effective subset of CD62L+CD69+ Tregs. The third chapter of this thesis focuses on the contribution of CD8+ T cells to fibrosis resulting from sterile lung injury. Type 2 effector production of IL-13 is v a demonstrated requirement in several models of fibrosis, and is routinely ascribed to CD4+ Th2 cells. However, we now demonstrate a major role for pulmonary CD8+ T cells, which mediate an exaggerated wound healing response and fibrosis through robust differentiation into IL-13-producing pro-fibrotic type 2 effectors (Tc2). Remarkably, differentiation of these Tc2 cells in the lung requires IL-21. We further show that the combination of IL-4 and IL-21 skews naïve CD8+ T cells to produce IL-21, which in turn acts in an autocrine manner to support robust IL-13 production. TGF-β negatively regulates production of IL-13 by suppressing CD8+ T cell responsiveness to IL-21. Our data illuminate a novel pathway involved in the onset and regulation of pulmonary fibrosis, and identify Tc2 cells as key mediators of fibrogenesis.

Celiac Disease (CD) is an autoimmune disorder that emerges due to the ingestion of gluten, a protein found in a variety of common grains such as wheat, rye, and barley. Approximately 1 in 100 individuals in the US suffer from CD, making it the most commonly diagnosed gastrointestinal disorder (Ciclitira et. al., 2005). These proline-rich gluten peptides are resistant to proteolysis and accumulate in the duodenum of the small intestine. Once in the duodenum, these peptides illicit an autoimmune response resulting in villous atrophy. Current treatment for CD requires a rigorous adherence to a gluten-free diet. Nevertheless, gluten-containing grains are ubiquitous in the western diet, so accidental exposure to gluten remains as a persistent threat. The approach of this project centers on genetically engineering a strain Lactobacillus reuteri to secrete a Myxococcus xanthus prolyl endopeptidase (PEP), an enzyme that hydrolyzes a peptide bond adjacent to an internal proline residue. The data from this study revealed that recombinant M. xanthus PEP purified from E. coli was effective in degrading Suc-Ala-Pro-pNA, a chromogenic substrate containing an internal proline residue. When introduced into a L. reuteri expression vector, mutations accumulated in the vector over the course of 5 days. These data suggested that toxicity was possibly associated with M. xanthus PEP and the amyl signal peptide.

Equine protozoal myeloencephalitis (EPM), caused by the protozoan parasite Sarcocystis neurona, is one of the most important neurological diseases of horses in the Americas. While seroprevalence of S. neurona in horses is high, clinical manifestation of EPM occurs in less than 1% of infected horses. Factors governing the occurrence and severity of EPM are largely unknown, although horse immunity might play an important role in clinical outcome. We hypothesize that EPM occurs due to an aberrant immune response, which will be discernable in the equine IgG subisotypes a, b, and (T) that recognize S. neurona in infected diseased horses versus infected but clinically healthy horses. Based on previously-established serum antibody concentrations for IgG subisotypes in healthy horses, standard curves were generated and served to establish the concentration of antigen-specific IgG subisotypes in equine serum and CSF in infected diseased and infected normal horses. The subisotype concentrations and ratios between subisotypes were analyzed to assess whether neurological disease is associated with detectable differences in the antibody response elicited by infection. Results indicate a type I biased immune response in infected diseased horses, implicating the role of immunity in the development of EPM.