Transmissible spongiform encephalopathies (TSEs) are a group of fatal neurodegenerative diseases that are characterised by long incubation periods, protein aggregation and vacuolation. During TSE pathogenesis the normal, cellular prion protein, (PrPC), which is encoded by the gene PRNP, misfolds and accumulates as abnormal disease associated prion protein, (PrPSc) within the central nervous system. Variants of the Prion protein gene are associated with susceptibility to TSE disease. For example sheep scrapie disease is modulated by several PRNP alleles, with certain alleles carried by susceptible animals being different from those carried by resistant animals. The mechanisms linking PRNP genetics and disease is poorly understood but may involve protein sequence, PrPC expression levels, and possibly differences in protein processing. Post-translational modification of PrPC leads to specific cleavage (alpha cleavage) between amino acids 115/116 of ovine PrP, producing two fragments C1 and N1. Cleavage of PrP may occur as a protective mechanism, as a response to changes in the cellular environment or as a feature of an as yet unknown biological function. In the context of TSEs, alpha cleavage may inadvertently provide a protective role by reducing available PrPC protein for conversion into PrPSc, assuming that the C1 fragment would be an inefficient substrate for conversion, the opposite theory was also proposed. The former hypothesis became the focus of this present study, with the idea that total full-length PrPC, total C1 or the ratio between full-length PrPC and C1 may be linked to differences in scrapie susceptibility. To investigate these aims the C1 fragment was measured as a percentage of total PrPC in different PRNP genotypes with varying degrees of susceptibility to scrapie and in different brain regions. This study found that PrPC alpha cleavage increased during development from the new born lamb to the adult sheep, which may have consequences for the susceptibility differences related to age. There are also variations in the amount of alpha cleavage between brain regions such as cortex and medulla that may influence scrapie strain targeting. Overall the amount of the C1 fragment in the different brain areas varied as much as 10x (range 5% to 60%). There was a significant difference in the ratio of C1 to the other PrPC forms between two PRNP genotype groups carrying the VRQ and ARQ allele but there was no correlation between C1 level and scrapie susceptibility or scrapie incubation period in our scrapie models. Alpha cleavage of PrPC also occurs in various transgenic mouse models expressing different ruminant PrP sequences. In PrPC over-expressing transgenic mouse models a higher ratio of C1 was observed, this may suggest a link between PrPC expression levels and alpha cleavage. Transgenic mice are therefore important models to further investigate the link between PrPC biology and scrapie disease phenotype. In conclusion, this thesis has shown for the first time that certain ovine PRNP alleles can influence alpha cleavage of the PrPC protein; however it appears not to be a significant indicator of TSE disease susceptibility in sheep.

In CBA/NJ mice, splenic natural killer (NK) cell activity varies with stages of estrous. Susceptibility of ICR mice to intravaginal inoculation of herpes simplex virus type 2 (HSV-2) decreases with age. Susceptibility of female ICR and CBA/NJ mice to HSV-2 inoculated intravaginally and intraperitoneally was examined during the estrous cycle. In cycling ICR mice, greatest susceptibility to intravaginal inoculation was observed during diestrous and the least during metestrous. CBA/NJ mice were most susceptible to intravaginal inoculation of HSV-2 during diestrous. ICR mice were ovariectomized to mimic diestrous and found to be highly susceptible to intravaginal inoculation at all virus doses. No difference in susceptibility among phases of the estrous cycle was seen following intraperitoneal inoculation.

A number of polymorphisms in the human VDR gene (located on chromosome 12q12-14) have previously been associated with TB susceptibility, of which most commonly, FokI, BsmI, ApaI and TaqI. The active metabolite of vitamin D, 1,25 dihydroxyvitamin D3, is an important immunoregulatory hormone. Its effects are exerted via the VDR, which is present on human monocytes and activated T and B-lymphocytes. Considering the role of the VDR and it specific immunological functions, including activation of monocytes, stimulation of cell-mediated immunity, suppression of lymphocyte proliferation, immunoglobulin production and cytokine synthesis, variation in the VDR genes may contribute to disease susceptibility. Hypothesis and objectives: In this study it was hypothesized that polymorphisms in the vitamin D receptor (VDR) gene influence TB susceptibility in the Venda population of South Africa. The role of VDR polymorphisms in TB susceptibility was investigated by setting the following objectives: 1. Typing of VDR gene polymorphisms (FokI, BsmI, ApaI and TaqI) in controls and TB cases as well as family samples from a Venda population of the Northern Province of South Africa. Comparing VDR allele and genotype frequencies between the Venda population and other populations as reported in the literature. 2. Analysis of possible associations in the case-control and family-based study 3. Studying Linkage disequilibrium (LD) in the case-control and the family samples. 4. Screening VDR haplotypes in the case-control and family-based study for possible association with TB. Patient and laboratory methods: VDR polymorphisms were studied in controls (n=110), TB cases (n=113) and 25 families in the Venda population inhabiting the Northern Province of South Africa. Case-control studies are vulnerable to false positive results caused by inadequate matching of the two groups. For this reason, a withinfamily association test was also implemented (the transmission disequilibrium test, TDT), as this is robust to this possible source of error. ARMS-PCR was used to type the VDR allele polymorphisms. The Statistical Package for Social Sciences (SPSSv10) was used to analyze possible association in case-controls, while TRANSMIT was used to analyze transmission of VDR alleles to affected offspring. LD between the single nucleotide polymorphisms (SNPs) of the VDR gene was investigated using the software “Graphical Overview of Linkage Disequilibrium” (GOLD) in both case-control and family studies. Possible association of TB with haplotypes comprising the VDR SNPs, ApaI and TaqI, were determined using SPSSv10 and TRANSMIT respectively for case-controls and the family based study. Results: 1. The comparative analysis indicated that the allele frequencies of the VDR SNPs related to the African American population. Genotype frequencies for FokI, BsmI and TaqI were similar to the West African population, whereas ApaI did not relate to any of the populations investigated. 2. No significant differences existed concerning the allele frequencies or genotype distribution between controls and TB cases with regard the VDR SNPs; FokI, BsmI and TaqI. The ApaI allele ‘A’ differed between cases and controls (p=0.041) but, no significant differences were obtained for genotype distribution between cases and controls for this SNP. All SNPs were in Hardy-Weinburg equilibrium except for ApaI. No differences between controls and cases were observed concerning allele presence or absence. In the family-based study, no significant difference was observed between observed and expected numbers of transmission for neither alleles nor genotypes, although, a borderline association was observed between TaqI ‘T’ allele and TB susceptibility (p=0.084). 3. LD in the case-control study was found between the VDR SNPs: BsmI and ApaI (p=0.051, D’=0.478), BsmI and TaqI (p=0.007, D’=0.222) and ApaI and TaqI (p=0.003, D’=0.479). In the family-based study, LD was only observed between ApaI and TaqI (p=0.049, D’=0.001) 4. Haplotype analysis in the case-control study indicated that no significant difference between controls and TB cases was observed. The family-based study indicated that transmission of the VDR haplotype ‘AT’ and ‘at’ differed from the expected transmission, but was of borderline significance. ‘AT’ was transmitted more than expected (P=0.090) and ‘at’ was transmitted less than expected (P=0.075), indicating that ‘AT’ may play a role in TB susceptibility and ‘at’ may play a protective role. Conclusion: The current study supports a possible role for VDR polymorphisms, ApaI (‘A’, p=0.041), or nearby yet unidentified markers in TB susceptibility in African populations (FokI-ApaI-BsmI-TaqI) (p=0.049). A larger sample size may clarify associations found to be of borderline significance. Results obtained may contribute to an improved understanding of genetic susceptibility factors in Africans. / Prof. L. Bornman

A leishmaniose visceral constitui grave doença infecciosa causada por um protozoário parasita intracelular obrigatório. Alguns fatores podem alterar a gravidade das manifestações clínicas, sendo um deles a predisposição genética. Este estudo investigou polimorfismos dos genes TGFB1, IL8 e IL6, que são citocinas relacionadas com o desencadeamento e a gravidade da doença, visando identificar fatores de susceptibilidade. Os polimorfismos TGFB1 -509 C/T e TGFB1 +869 T/C, IL8 -251A/T e IL6 -174G/C foram analisados por PCR-RFLP, em 198 pacientes com leishmaniose visceral (LV), 98 indivíduos com infecção assintomática (teste de hipersensibilidade tardia - DTH+) e 100 indivíduos sem evidências de infecção (DTH-). O alelo T na posição -509 do gene TGFB1 conferiu risco duas vezes maior de desenvolver LV ou ser positivo para o teste DTH (p = 0,007, OR = 1,9 [1,19-3,02]), em comparação com indivíduos DTH-. Os resultados sugerem uma associação do polimorfismo TGFB1 -509C/T com a susceptibilidade à LV, podendo contribuir para o desencadeamento da doença clínica. / Visceral leishmaniasis is a serious protozoan infectious disease caused by an obligate intracellular parasite. Some factors can affect the severity of the clinical manifestations; one of which is genetic susceptibility. This study investigated polymorphisms in the TGFB1, IL8 and IL6 genes, which are cytokines related with the onset and severity of the disease, to look for genetic susceptibility factors. Polymorphisms at TGFB1 -509C/T and +869T/C, and IL8 - 251A/T and IL6 -174G/C were analyzed by a PCR-RFLP technique, in 198 patients with Visceral Leishmaniasis (VL), 98 individuals with asymptomatic infection (positive delayed-type hypersensitivity, DTH+) and 100 individuals with no evidence of infection (DTH-). The T allele of the TGFB1 polymorphism in position -509C/T conferred a two risk fold to develop LV or to be DTH+ (p=0.007; OR=1.9 [1.19 - 3.02]) when compared with DTH- individuals. We suggest the TGFB1 -509C/T polymorphism is associated with susceptibility to LV and may contribute to development of the clinical disease.

Sjèogren's syndrome (S) is a chronic autoimmune disease characterized by ocular and oral dryness and primarily affects post menopausal women. In the present study we investigated the time course of lymphocytic infiltration, apoptosis, caspase-3 activity and different cytokines levels in the lacrimal glands of both genetically predisposed and control mice to elucidate immunopathological mechanism leading to dry eye. The results of our experiments showed that ovariectomy accelerated pathological findings of SS by increasing lympocytic infiltration, cytokine production, lacrimal gland cell death and cleaved caspase-3 activity, and these effects were more pronounced and persistent in the genetically predisposed mouse model of SS. In addition, we observed that lymphocytic infiltration occurred earlier compared to apoptosis which may perpetuate immune mediated destruction of lacrimal epithelial cells. Furthermore, treatment with physioloigical doses of 17-B Estradiol (E2) or DIhydrotestosterone (DHT) prevented all these pathological events observed after ovariectomy. / by Safinaz Mostafa. / Thesis (M.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

Myxobolus cerebralis, a myxozoan parasite of salmonids, is the causative agent of whirling disease. The parasite is considered widespread throughout northeastern Oregon in the Grande Ronde and Imnaha River basins where threatened and endangered salmonid populations exist. The work presented in this thesis comprises several studies that assess the effects of M. cerebralis on resident and anadromous salmonids in Oregon. Laboratory challenges to determine the susceptibility of indigenous Deschutes River, Oregon, salmonids to M. cerebralis were conducted as part of a study to assess the risk of reintroducing anadromous salmon above a migration barrier on that river. This study was the first to assess the susceptibility of kokanee salmon Oncorhynchus nerka to M. cerebralis, and results contribute to the understanding of salmonid susceptibility as it relates to species and age. Further, this study demonstrates that the indigenous salmonids present in the river are susceptible to infection, but resident rainbow trout Oncorhynchus mykiss would be most at risk should introduction of M. cerebralis occur in this system. The susceptibility of chinook salmon Oncorhynchus tshawytscha to M. cerebralis was assessed following laboratory challenges at different ages to different parasite levels. Results from this study indicate that chinook salmon are more resistant to M. cerebralis infection than susceptible rainbow trout; resistance to disease developed in chinook salmon exposed after 3 weeks of age. Sustained exposures to a low parasite dose were performed to model the conditions chinook salmon would encounter in a natural exposure. Following continuous exposure to low parasite densities, chinook salmon were very resistant to infection and disease. Managed populations of chinook salmon and steelhead Oncorhynchus mykiss juveniles are held in acclimation facilities on their natal streams before release to commence their seaward migration. Rainbow trout fry were held at each of the acclimation facilities to detect the presence of M. cerebralis and to assess the prevalence of exposure during the acclimation period. Results from these exposures indicate that the Wallowa acclimation facility is a high-risk site for parasite exposure of steelhead juveniles. Further, detection was confirmed in several rivers and streams where the presence of M. cerebralis has been suggested. Finally, a preliminary study on the effect of M. cerebralis on survival of steelhead juveniles upon transfer to saltwater was conducted. Results from this study indicate that M. cerebralis exposure and infection may increase mortality among juvenile steelhead during saltwater adaptation. / Graduation date: 2003

Thesis (M.Sc. Biological Sciences)--University of Waikato, 2007. / Title from PDF cover (viewed February 27, 2008) Includes bibliographical references (p. 189-199)

Made available in DSpace on 2014-06-11T19:27:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-25Bitstream added on 2014-06-13T19:56:29Z : No. of bitstreams: 1 corbi_sct_me_arafo.pdf: 500522 bytes, checksum: acbb0ada52f0fc0619726c5c3c57e5c5 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A Doença Periodontal (DP) tem caráter multifatorial, com a influência de fatores como a presença de microrganismos periodontopatogênicos, suscetibilidade genética do hospedeiro, reação do sistema imune, hábito de fumar e presença de doenças sistêmicas. O tecido periodontal inflamado produz várias citocinas, dentre elas a interleucina 8 (IL-8). Estudos recentes realizados por este grupo investigaram polimorfismos no gene IL8 em indivíduos com e sem periodontite crônica, onde foram observados indivíduos com 2 vezes mais predisposição genética à DP. O objetivo do presente estudo foi testar a hipótese de que a maior suscetibilidade genética à periodontite crônica dada pelo haplótipo ATC/TTC no gene IL8 seria acompanhada por diferenças nos índices clínicos periodontais, nos níveis da citocina IL-8 no fluido sulcular (FS) e na resposta ao tratamento periodontal não-cirúrgico. Foram selecionados 79 indivíduos divididos quanto à presença ou não do referido haplótipo no gene IL8, de forma que os indivíduos “suscetíveis” e “não suscetíveis” foram subdivididos quanto à presença ou ausência da periodontite crônica. Os indivíduos selecionados foram submetidos a exame clínico periodontal e coletas de FS antes e após 45 dias de finalizado o tratamento periodontal não-cirúrgico. A citocina IL-8 foi quantificada por meio de teste imunoenzimático (ELISA). Como resultado verificou-se que, comparando indivíduos suscetíveis e não-suscetíveis à DP, não houve diferença estatisticamente significante tanto nos índices clínicos periodontais quanto na resposta ao tratamento periodontal realizado, sendo que apenas o volume do FS, no período baseline, apresentou diferença significativa. Assim, a suscetibilidade genética à DP previamente observada nesses indivíduos não... / Periodontal disease is a multifactorial disease which is influenced by factors such as the presence of periodontopathogenic microorganisms, the reaction of the immune system, smoking, genetic susceptibility and the occurrence of systemic diseases. The inflamed periodontal tissue produces several cytokines like Interleukin 8 (IL-8). Recent studies carried out by our research group investigated polymorphisms in the IL8 gene in patients with and without periodontitis, where it was found individuals with a genetic predisposition to periodontitis. The purpose of this study was to test the hypothesis that the genetic susceptibility to chronic periodontitis given by ATC/TTC haplotype in IL8 gene would be linked to differences in the clinical periodontal parameters, IL-8 cytokine levels in the gingival crevicular fluid (GCF) and the response to non-surgical periodontal therapy. Seventy-nine individuals were selected and grouped according to the presence or not of the haplotype given in the IL8 gene, so that the “susceptible” and “nonsusceptible” individuals were subdivided by the presence or absence of chronic periodontitis. The selected individuals were submitted to periodontal clinical exam and the collection of GCF was done before and 45 days after the non-surgical periodontal therapy. The IL-8 cytokine was quantified through an immunoenzymatic assay (ELISA). As a result, it was verified that, comparing susceptible and non-susceptible individuals to chronic periodontitis, there wasn’t any statistically significant difference as in clinical periodontal parameters as in response to non-surgical periodontal therapy. However, the volume of GCF, at baseline, presented a significant difference. Thus, the genetic susceptibility to chronic periodontitis previously observed in these individuals influenced neither... (Complete abstract, click electronic access below)

Orientador: Raquel Mantuaneli Scarel Caminaga / Banca: Silvana Regina Perez Orrico / Banca: Andréa Márcia Marcaccini / Resumo: A Doença Periodontal (DP) tem caráter multifatorial, com a influência de fatores como a presença de microrganismos periodontopatogênicos, suscetibilidade genética do hospedeiro, reação do sistema imune, hábito de fumar e presença de doenças sistêmicas. O tecido periodontal inflamado produz várias citocinas, dentre elas a interleucina 8 (IL-8). Estudos recentes realizados por este grupo investigaram polimorfismos no gene IL8 em indivíduos com e sem periodontite crônica, onde foram observados indivíduos com 2 vezes mais predisposição genética à DP. O objetivo do presente estudo foi testar a hipótese de que a maior suscetibilidade genética à periodontite crônica dada pelo haplótipo ATC/TTC no gene IL8 seria acompanhada por diferenças nos índices clínicos periodontais, nos níveis da citocina IL-8 no fluido sulcular (FS) e na resposta ao tratamento periodontal não-cirúrgico. Foram selecionados 79 indivíduos divididos quanto à presença ou não do referido haplótipo no gene IL8, de forma que os indivíduos "suscetíveis" e "não suscetíveis" foram subdivididos quanto à presença ou ausência da periodontite crônica. Os indivíduos selecionados foram submetidos a exame clínico periodontal e coletas de FS antes e após 45 dias de finalizado o tratamento periodontal não-cirúrgico. A citocina IL-8 foi quantificada por meio de teste imunoenzimático (ELISA). Como resultado verificou-se que, comparando indivíduos suscetíveis e não-suscetíveis à DP, não houve diferença estatisticamente significante tanto nos índices clínicos periodontais quanto na resposta ao tratamento periodontal realizado, sendo que apenas o volume do FS, no período baseline, apresentou diferença significativa. Assim, a suscetibilidade genética à DP previamente observada nesses indivíduos não... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Periodontal disease is a multifactorial disease which is influenced by factors such as the presence of periodontopathogenic microorganisms, the reaction of the immune system, smoking, genetic susceptibility and the occurrence of systemic diseases. The inflamed periodontal tissue produces several cytokines like Interleukin 8 (IL-8). Recent studies carried out by our research group investigated polymorphisms in the IL8 gene in patients with and without periodontitis, where it was found individuals with a genetic predisposition to periodontitis. The purpose of this study was to test the hypothesis that the genetic susceptibility to chronic periodontitis given by ATC/TTC haplotype in IL8 gene would be linked to differences in the clinical periodontal parameters, IL-8 cytokine levels in the gingival crevicular fluid (GCF) and the response to non-surgical periodontal therapy. Seventy-nine individuals were selected and grouped according to the presence or not of the haplotype given in the IL8 gene, so that the "susceptible" and "nonsusceptible" individuals were subdivided by the presence or absence of chronic periodontitis. The selected individuals were submitted to periodontal clinical exam and the collection of GCF was done before and 45 days after the non-surgical periodontal therapy. The IL-8 cytokine was quantified through an immunoenzymatic assay (ELISA). As a result, it was verified that, comparing susceptible and non-susceptible individuals to chronic periodontitis, there wasn't any statistically significant difference as in clinical periodontal parameters as in response to non-surgical periodontal therapy. However, the volume of GCF, at baseline, presented a significant difference. Thus, the genetic susceptibility to chronic periodontitis previously observed in these individuals influenced neither... (Complete abstract, click electronic access below) / Mestre

Orientador: Carlos Fernando Salgueirosa de Andrade / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-05T12:43:31Z (GMT). No. of bitstreams: 1 Silva_GilciaAparecidadeCarvalho_D.pdf: 2420692 bytes, checksum: 389c3c5a059387fa98ae9be752bd8f0e (MD5) Previous issue date: 2006 / Resumo: Mosquitos pertencentes aos gêneros Culex, Aedes, Anopheles, Mansonia, Psorophora e Coquillettidia são susceptíveis à infecção por Dirofilaria immitis (Leidy, 1856), podendo transmitir o filarídeo aos cães e gatos. Os vetores de D. immitis no Brasil são conhecidos apenas nos Estados do Rio de Janeiro e do Maranhão, fazendo-se necessária a investigação da susceptibilidade e da competência vetorial de espécies existentes nos demais Estados brasileiros. O presente trabalho teve por finalidade verificar a freqüência de infecção por D. immitis em cães domiciliados na Região Metropolitana do Recife, bem como avaliar a susceptibilidade e a competência vetorial de Culex quinquefasciatus Say, 1823, Aedes aegypti Linnaeus, 1762 e Ae. albopictus Skuse, 1894 provenientes de área endêmica e não endêmica para a transmissão desse filarídeo, em condições experimentais. A resposta imune humoral (melanização) apresentada pelos mosquitos expostos à infecção também foi avaliada. Para a realização do inquérito epidemiológico, 816 amostras de sangue canino foram coletadas nas áreas costeiras da Região Metropolitana do Recife e no município de Bezerros, agreste do Estado de Pernambuco. As amostras sangüíneas foram analisadas por meio de teste parasitológico para a pesquisa de microfilárias de D. immitis, utilizando-se o método modificado de Knott. Para a avaliação da competência vetorial Cx. Quinquefasciatus população RECIFE, Ae. aegypti populações RECIFE, UNICAMP e linhagem ROCKFELLER e Ae. albopictus população RECIFE foram criados em insetário sob condições controladas (28 '+ ou ¿' '1 GRAU C¿ e 80 ' + ou ¿' 5% de umidade relativa do ar). As fêmeas das espécies estudadas foram alimentadas com sangue canino contendo diferentes densidades de microfilárias de D. immitis, por meio de membrana artificial confeccionada com pele fresca de animal. Para Cx. quinquefasciatus, que é uma espécie ornitofílica, foi utilizada pele de codorna, e para Ae. aegypti e Ae. albopictus a membrana artificial foi confeccionada com pele de rato. Os resultados obtidos no estudo mostraram freqüência de 3,61%, 7,89% e 7,69% de cães infectados na Ilha de Itamaracá, Igarassu e Recife, respectivamente. Após as infecções experimentais, observou-se que a mortalidade de Cx. quinquefasciatus não foi influenciada pela exposição a diferentes densidades de microfilárias de D. immitis (F = 0,0615, p>0,05) e os índices encontrados variaram de 8,9% a 36,25%. Os índices de eficiência vetorial (IEV) apresentados por Cx. quinquefasciatus população RECIFE variaram de 7,8% a 56,5%. Em relação à razão de infecção, o maior índice foi encontrado no grupo de fêmeas expostas a densidade de 1913 microfilárias/ml, entretanto, não foi influenciado pela taxa de ingurgitamento das fêmeas (F=3,2937, p>0,05). Por meio de melanização, Cx. quinquefasciatus população RECIFE, limitou a intensidade do parasitismo, promovendo o equilíbrio da relação parasito-hospedeiro e deste modo passando a ser um excelente vetor de D. immitis na Região Metropolitana do Recife. Dentre as espécies de Aedes estudadas, verificou-se que a população RECIFE de Ae. aegypti apresentou maior mortalidade (70,7%) ao final dos experimentos, apresentando diferença estatisticamente significante (p<0,01) em relação à linhagem ROCKFELLER, população UNICAMP e Ae. albopictus população RECIFE, que não diferiram entre si (p>0,05). Em relação ao índice de eficiência vetorial (IEV) foi detectado um índice de 7,4% para a linhagem ROCKFELLER e uma variação de 20,0% a 53,8% para as populações de Ae. aegypti e 25,2% para Ae. albopictus população RECIFE. O maior número de larvas de D. immitis infectantes na probóscide foi apresentado por Ae. albopictus população RECIFE, além de uma baixa mortalidade. Desta forma, esta população mostrou-se susceptível ao filarídeo e por apresentar baixa mortalidade, foi considerada como a melhor vetora. Ae. aegypti população RECIFE não apresentou reação de melanização e apresentou mortalidade acentuada, enquanto que Ae. aegypti população UNICAMP e linhagem ROCKFELLER mostraram-se refratárias à infecção por D. immitis / Abstract: Mosquitoes belong to the genus Culex, Aedes, Anopheles, Mansonia, Psorophora and Coquillettidia are susceptible to infection of Dirofilaria immitis (Leidy, 1856) and some of them serve as vectors heartworm disease in dogs and cats. Although the potential vectors of canine heartworm in Brazil have been recorded only in Rio de Janeiro and Maranhão State and no more date are available. The objective of this study was to verify the frequency of heartworm infection in dogs in metropolitan region of Recife and also identify under experimental conditions their ability of Culex quinquefasciatus Say, 1823, Aedes aegypti Linnaeus, 1762 and Ae. albopictus Skuse,1894 from enzootic and non enzootic areas to become infected with and transmit D. immitis. After the experimental infection of mosquitoes, the melanization response to larvae of D. immitis also was evaluated. The survey study were performed on a total of 816 dogs from costal areas of Metropolitan Region of Recife and Bezerros County, located in agreste area of Pernambuco State. Whole blood samples were collected from all animals and were examined for the presence of microfilariae of D. immitis by the modified Knott test. To verify the vector competence of Cx. quinquefasciatus RECIFE population, Ae. aegypti RECIFE, UNICAMP populations and also ROCKFELLER strain and Ae. albopictus RECIFE population, the mosquitoes were reared under constant insectary conditions (28 '+ or ¿' '1 DEGREE C¿ and 80 '+ or ¿' 5% relative humidity). Females mosquitoes, were exposed to blood¿s dog with diferents density of D. immitis microfilariae by artificial feeding apparatus made by fresh animal skin. For this puporse, ornithophilic Cx. quinquefasciatus was feeding by skin quail menbrane, and for the Ae. aegypti and Ae. albopictus the artificial membrane was made by rat skin. The results of the survey study showed 3.61%, 7.89%, and 7.69% of heartworm infection frequency in dog from Itamaracá Island, Igarassu and the city of Recife respectively. The mortality of Cx. Quinquefasciatus RECIFE population observed in the vector competence study did not show influence of different density of microfilariae of D. immitis (F = 0.0615, p>0.05) and the mortality rate was 8.9% to 36.25%. The vector efficiency (VE) rates of Cx. quinquefasciatus RECIFE population were 7.8% to 56.5%. The higher infection rate was showed in females feeding with blood containing 1913 mf/ml, but no influence was observed in engorged females. The melanization response observed in Cx. quinquefasciatus was important for vector survival by limiting the number of larvae, acting as an important mechanism of parasitic-host interactions. The data indicate that the Cx. quinquefasciatus RECIFE population should is an excelent vector of D. immitis at metropolitan region of Recife. Significant difference (p<0.01) was observed in the mortality rates between the RECIFE population of Ae. aegypti, UNICAMP population, ROCKFELLER strain, and Ae. albopictus RECIFE population. Although no difference were observed between Ae. aegypti ROCKFELLER, UNICAMP and Ae. albopictus RECIFE population. The vector efficiency (VE) rates of Ae. aegypti and Ae. albopictus RECIFE population were 7.4% to 53.8% and 25.2% respectively. Not only the high number of infective third stage larvae of D. immitis in mouth of mosquitoes but also low mortality was observed in Ae. albopictus RECIFE population. This data showed that this specie is the best vector of heartworm infection in the study area. No melanization response was observed in Ae. Aegypti RECIFE population but high mortality was reported. The UNICAMP population and ROCKFELLER strain of Ae. aegypti were refractory to infection to D. immitis / Doutorado / Doutor em Parasitologia