Percorrer por autor "Coelho, Adosinda"
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- Immunological response to BrucellaPublication . Coelho, Ana Cláudia; Coelho, Adosinda; Quintas, Helder; Simões, JoãoThis chapter describes the immunological response to Brucella. The host immune response to Brucella is divided into innate and adaptive immunity. Protection against Brucella infection requires cell-mediated immunity, which includes CD4+ and CD8+ T lymphocytes, Th1-type cytokines such as IFN-γ and tumor necrosis factor-alpha (TNF-α), and activated macrophages and dendritic cells. Neutrophils, CD8+ and γδ T cells are part of the secondary innate immune response and migrate in the early stages of the infection to contribute to resolve the infection. Cytokine expression is necessary for development of a protective immune response. Brucella induces minimal production of pro-inflammatory cytokines. TNF-α, IL-12, and IFN-γ are the primary cytokines critical for defense against Brucella. In brucellosis, immune response mechanisms are divided in three primary mechanisms: (1) in the first step, it inhibits the intracellular survival of Brucella, IFN-γ produced by CD4+, CD8+, and T cells which activate macrophages, enhancing their bactericidal capacity; (2) secondly, cytotoxic CD8+ T cells directly kill infected macrophages, and T cells; and (3) thirdly, B lymphocytes secrete antibodies, in the endocytic compartments opsonization of Brucella and occur by immunoglobulin (Ig) G2a and IgG3 to increase phagocytosis which is useful for diagnosis of disease. The humoral antibody response consists in an early production of IgM against Brucella LPS for 3 to 4 weeks and rises gradually during the course of acute infection, followed by a gradual increase in IgG and IgA, beginning 7 to 14 days after infection. The dominant IgG isotype is IgG2. Antibodies against Brucella are proteins that cause agglutination, complement fixation, and precipitation when reacted with their homologous antigens. These antibodies have the potential to produce cross-reactions and this inevitably results in false positive serological tests.
- Pathogenesis of BrucellaPublication . Coelho, Ana Cláudia; Coelho, Adosinda; Quintas, Helder; Fernandes, Conceição; Saavedra, Maria José; Simões, JoãoThe goal of this chapter is to describe the pathogenesis of Brucella reporting, the host-pathogen and the cell/macrophage Brucella interactions, and the major virulence factors of this bacteria genus. The epithelium of the respiratory, digestive and reproductive tracts are the most important ports of bacterium entry in the host. The mechanisms by which Brucella enters the cells and evades the host immune system remains poorly understood. However, in the past decade, the mechanisms of Brucella pathogenesis and host immunity have been extensively investigated. Brucella has the ability to survive and replicate intracellularly in mononuclear phagocytes and to control host immune responses. This pathogen developed several strategies to evade the host s immune defense mechanisms preventing inflammatory responses at the site of entrance in the host and maintain the infection. Brucella bacterium is internalized by macrophages and dendritic cells, and invades the bloodstream and lymphatics causing an eventual transitory bacteremia. Inside phagocytic cells, few bacteria can survive. Brucella also shows a strong tissue tropism to monocytes in the liver, spleen, lymph nodes, bone marrow and trophoblasts. All these target cells lead to clinical manifestations, characterized by infection in lymphoid tissues and inflammatory lesions in the reproductive tract of pregnant females. Unlike other bacteria, Brucella lacks classical bacterial virulence factors such as exotoxins, capsules, secreted proteases, fimbriae, flagella, virulence plasmids, resistant strains and phage-encoded toxins. Other virulence factors have been implicated in the pathogenesis as the type IV secretion system, the BvrR/BvrS two component regulatory system, the Brucella intact lipopolysaccharide O-antigen in smooth strains, and cyclic -1,2-glucans. Toll-like receptors are single-pass type I transmembranespanning of proteins that play a key role in the innate immune system. Future perspectives include new genomics and omics technologies and software tools to analyze virulent genes associated with a Brucella infection. This information will provide a better knowledge of infection and Brucella-host relations that are necessary for vaccine production and strategies to prevent and control brucellosis in small ruminants.
- Symptoms, lesions and clinical evolution of Brucellosis in small ruminantsPublication . Quintas, Helder; Oliveira, Justina; Tavares, Humberto; Coelho, Ana Cláudia; Coelho, Adosinda; Simões, JoãoAlthough brucellosis in small ruminants can be caused by Brucella abortus and B. ovis (sheep), B. melitensis is the major Brucella species involved in acute and chronic forms of this disease. Late abortions, stillbirths, weak neonates and epididymitis/orchitis are the main clinical signs. B. melitensis acute infections in pregnant females causes a macroscopic placentitis. In males necrotic epididymitis and orchitis can be observed. In the chronic form of the disease, the main clinical signs may not occur but the infected animals continue actively secreting B. melitensis into the environment and can infect other animals and man. B. abortus causes deterioration in the quality of the semen and acute edema and inflammation of the scrotum. Palpable lesions in the epididymis and tunicae of one or both testicles also can be observed. Usually, no clinical signs are seen in the ewe, but in some flocks, infection causes abortion, stillborn lambs or weak neonates. In infected lactating goats, mastitis due to B. melitensis can be a frequent occurrence instead of abortion.
- Transmission of Brucella Melitensis and Brucella OvisPublication . Simões, João; Tavares, Humberto; Coelho, Ana Cláudia; Quintas, Helder; Castelo, Cristiana; Coelho, AdosindaThis chapter describes the transmission of Brucella melitensis, as well as B. ovis and other Brucella species, among animals and to humans (B. melitensis). Goats and sheep are mainly infected by ingestion or inhalation of bacterium from contaminated organic and inorganic materials, fluids and air. Nevertheless, the conjunctival and dermal routes also play a secondary role in direct contact. Due to the significant amount of bacterium present in the reproductive system of infected adult animals, the uterine secretions and abortion products, the milk and the semen are the main contagious material responsive for the horizontal transmission. A vertical in uterus, or acquired by the consumption of colostrum and/or milk, transmission also can occur and are responsible for latent brucellosis, where lambs or kids are seronegative mainly until puberty. The lambing or kidding seasons represents a decisive moment for the dissemination of bacterium in flocks and environment. However, infected animals can excrete Brucella during long periods in asymptomatic and/or chronic forms. The bacterium can survive for several months especially in cold and humid environments, or in other fomites or vectors, and is responsible for an indirect contact transmission. Wild animals as well as the presence of dogs and other domestic animals in flocks can also be involved in the transmission of Brucella. B. melitensis, and B. abortus, which can also infect small ruminants, are the most serious pathogens in humans, and are transmitted by direct and indirect contact. A low number of bacterium, 10 to 100 microorganims, can be sufficient to cause the human disease.
- Worldwide epidemiology of Brucella Melitensis and Brucella OvisPublication . Simões, João; Tavares, Humberto; Coelho, Ana Cláudia; Quintas, Helder; Coelho, AdosindaThe main goal of this chapter is to give an update on the worldwide distribution and prevalence of Brucella melitensis in animals and human populations, as well as the main risk factors of brucellosis occurrence in flocks. The current epidemiological data regarding brucellosis prevalence and incidence in small ruminants is still mainly based on indirect tests by the detection of antibodies anti-Brucella. Nevertheless, in the last years, a more progressive molecular characterization of B. melitensis, B. ovis and other Brucella species has been reported. As a consequence, new insights regarding the dynamics of Brucella were improved. Currently, several countries, mainly but not exclusively in socio-economic developed regions, e.g., USA, Oceania or Europe, are considered B. melitensis-free. In some other countries, normally with low socio-economic status, e.g., Africa or Asia, the situation remains unknown or with significantly high levels of brucellosis in small ruminants and people. According the data of the last five years, the true seroprevalence of brucellosis in small ruminant populations or flocks ranged from 2.7% to 70.4%, with Jordan and other Middle Eastern countries presenting the highest values. Animal movements, flock management, type and size, and environmental conditions are the most significant factors related to the prevalence of brucellosis