La transmission mère-enfant (TME) du VIH-1 est un des enjeux majeurs de la pandémie. Une meilleure compréhension de la réponse des lymphocytes T cytotoxiques CD8+ (LTC) VIH-spécifiques lors de la grossesse facilitera le design de stratégies optimales pour diminuer la TME. Notre objectif est donc de caractériser l’amplitude et la diversité de la reconnaissance antigénique des LTC VIH-spécifiques avant, pendant et après la grossesse chez des femmes infectées par le VIH-1. Nos résultats montrent pour la première fois que l’initiation et la progression de la grossesse, à elles seules, n'ont que peu d’influence sur l’amplitude et la diversité de la reconnaissance antigénique des réponses LTC en termes de production d’IFN‐. Ces résultats indiquent que les femmes infectées par le VIH conservent une immunocompétence durant leur grossesse, du moins dans le contexte d’un traitement antirétroviral efficace. Ceci pourrait éventuellement aider à promouvoir l’immunisation comme stratégie pour prévenir la TME du VIH‐1. / Mother-to-child transmission (MTCT) of HIV-1 is one of the major issues of the pandemic. Characterization of HIV-specific immunity during pregnancy, especially cytotoxic CD8+ T lymphocytes (CTL), will lead to a better understanding of HIV pathogenesis and facilitate design of optimal strategies to prevent MTCT. Our objective is to describe the magnitude and the breadth of antigen recognition of HIV-specific CTL responses before, throughout and after pregnancy in a group of HIV-infected women. Our results revealed for the first time that initiation of pregnancy by itself doesn’t change the magnitude of CTL responses in terms of IFN- production. These findings support the fact that HIV-infected women maintain immunocompetence throughout gestation, at least in the context of effective antiretroviral treatment. These results provide a novel understanding of the dynamics of HIV-specific CTL responses during pregnancy and may help to promote maternal immunization as a strategy to prevent MTCT of HIV-1.

La transmission mère-enfant du VIH-1 (TME) représente le principal mode d’infection chez l’enfant et se produit durant la grossesse (in utero, IU), l’accouchement (intrapartum, IP) ou l’allaitement (postpartum, PP). Les mécanismes qui sous-tendent le passage du VIH-1 à travers le placenta et les muqueuses intestinales du nouveau-né sont encore très peu décrits. « Dendritic cell-specific ICAM-grabbing non-integrin » (DC-SIGN) et son homologue DC-SIGN « related » (DC-SIGNR) sont des récepteurs d’antigènes exprimés au niveau du placenta et capables de capter et de transmettre le VIH-1 aux cellules adjacentes. Ils pourraient donc participer au passage trans placentaire du VIH-1 et le polymorphisme génétique affectant l’expression ou modifiant l’interaction avec le virus aurait une influence sur la TME du VIH-1. Afin d’explorer cette hypothèse, nous avons procédé à une analyse exhaustive du polymorphisme de DC-SIGN et DC-SIGNR dans la population du Zimbabwe. Par la suite, nous avons déterminé l’association entre le polymorphisme de DC-SIGN et DC-SIGNR et la TME du VIH-1 dans une cohorte d’enfants nés de mères VIH-positives à Harare, au Zimbabwe. Enfin, nous avons défini l’impact fonctionnel des mutations associées. Les enfants homozygotes pour les haplotypes H1 et H3 dans le gène de DC-SIGNR sont 4 à 6 fois plus à risque de contracter le VIH-1 par voie IU et IP. H1 et H3 contiennent la mutation du promoteur p-198A et la mutation de l’intron 2, int2-180A, et des études fonctionnelles nous ont permis de démontrer que p-198A diminue l’activité transcriptionnelle du promoteur de DC-SIGNR et l’expression des transcrits d’ARNm dans le placenta, alors que int2-180A modifie le répertoire d’isoformes de DC-SIGNR vers une proportion diminuée d’isoformes membranaires. Les enfants porteurs des haplotypes H4 et H6 de DC-SIGN sont 2 à 6 fois plus à risque de contracter le VIH-1 par voie IU. Ces haplotypes contiennent deux mutations du promoteur (p-336T/C et p-201C/A) et quatre mutations codant pour un changement d’acide aminé dans l’exon 4 (R198Q, E214D, R221Q ou L242V) associées à un risque augmenté de transmission IU, IP et PP du VIH-1. Des études fonctionnelles ont démontré que les mutations du promoteur diminuent l’expression de DC-SIGN dans les macrophages placentaires. Toutefois, l’exposition IU au VIH-1 module le niveau d’expression de DC-SIGN, résultant en des niveaux d’expression similaires entre les macrophages des porteurs des allèles sauvages et mutés. Les mutations de l’exon 4 augmentent l’affinité de DC-SIGN pour le VIH-1 et sa capacité à capturer et à transmettre le virus aux lymphocytes T, favorisant possiblement la dissémination du VIH-1 à travers le placenta. L’association entre les mutations de DC-SIGN et la transmission IP et PP du VIH-1 suggèrent qu’il aurait aussi un rôle à jouer dans les muqueuses intestinales de l’enfant. Notre étude démontre pour la première fois l’implication de DC-SIGN et DC-SIGNR dans la TME du VIH-1. L’augmentation des capacités de capture et de transmission de DC-SIGN résulte en une susceptibilité accrue de l’enfant à l’infection au VIH-1 et concorde avec un rôle dans la dissémination transplacentaire. Toutefois, la diminution préférentielle des transcrits membranaires de DC-SIGNR au placenta augmente la TME du VIH-1 et laisse croire à son implication via un autre mécanisme. Ces mécanismes pourraient aussi s’appliquer à d’autres pathogènes reconnus par DC-SIGN et DC-SIGNR et transmis de la mère à l’enfant. / Mother-to-child transmission (MTCT) is the main cause of HIV-1 infection in children worldwide. MTCT of HIV-1 can occur during pregnancy (in utero, IU), delivery (intrapartum, IP) or breastfeeding (postpartum, PP). Dendritic cell-specific ICAM-grabbing non-integrin (DC-SIGN) and its homolog DC-SIGN related (DC-SIGNR) are attachment receptors for HIV-1 and are expressed in the placenta. They have been implicated in viral capture and transmission to T cells. To investigate the potential role of DC-SIGN and DC-SIGNR in MTCT of HIV-1, we carried out a genetic association study in a well-characterized cohort of 197 HIV-infected mothers and their infants recruited in Harare, Zimbabwe. Infants harbouring two copies of DC-SIGNR H1 and/or H3 haplotypes (H1-H1, H1-H3, H3-H3) had a 4-fold increased risk of IU and 6-fold increased risk of IP HIV-1 infection after adjusting for a number of maternal factors. The implicated H1 and H3 haplotypes share two single nucleotide polymorphisms (SNPs) in promoter region (p-198A) and intron 2 (int2-180A) that were associated with increased risk of both IU and IP HIV-1 infection. The promoter variant reduced transcriptional activity in vitro. In homozygous H1 infants bearing both the p-198A and int2-180A mutations, we observed a 4-fold decrease in the level of placental DC-SIGNR transcripts, disproportionately affecting the expression of membrane-bound isoforms compared to infant noncarriers. Infants carrying H4 and H6 haplotypes in DC-SIGN gene were more likely to be HIV-1-infected during pregnancy. These haplotypes contain promoter variants (p-336T/C and p-201C/A) and exon 4 variants (R198Q, E214D, R221Q and L242V) that were all significantly associated with increased risk of MTCT of HIV-1. Compared with wild-type sequence, the promoter variants reduced both the DC-SIGN transcription in vitro and expression (2-fold) in placental macrophages of HIV-1-unexposed infants. However, in HIV-1-exposed infants, the level of DC-SIGN expression in placental macrophages was similar in infants carrying either the promoter wild-type or variant sequences. Exon 4 variants increased HIV-1 capture and transmission to T cells in vitro. Association between DC-SIGN SNPs and HIV-1 IP and PP infection also suggests that DC-SIGN plays an important role in intestinal mucosa. This is the first study reporting on functional impact of DC-SIGN and DC-SIGNR natural polymorphisms on HIV-1 transmission from mother-to-child. Decreased levels of expression of membrane DC-SIGNR isoforms at the placental endothelial cell surface increased child susceptibility to HIV-1. Presence of DC-SIGN variants increasing its affinity for the virus augmented child susceptibility to HIV-1 and may favour viral dissemination across the placental barrier. This study provides compelling evidence to support an important role of DC-SIGN and DC-SIGNR in various modes of MTCT of HIV-1 and shed light on the possible mechanisms involved in HIV-1 passage from mother-to-infant. These findings raise the possibility that similar mechanisms may operate with other human pathogens known to interact with DC-SIGN and DC-SIGNR.

The study reports on the perceptions of the midwives and pregnant women of the PMTCT of HIV programme at the antenatal care and maternity ward at the Johan Heyns Community Health Centre. A qualitative approach was adopted to conduct the study. Purposive sampling was used to select participants and was informed by social behavioural theories. Data was collected using interviews and analysed using thematic categorisation. The findings show that at the first PMTCT encounter participants had little to no knowledge of the PMTCT programme, generally displayed a lack of interest, experienced emotional distress, and fear at the thought of having to disclosing their HIV-positive status to their partners/family and had certain trepidations about participating in the PMTCT programme. The participants’ perception on their roles was that their roles were interlinked, midwife needs the recipients (pregnant woman) and pregnant woman needs the provider (midwife) therefore one cannot do PMTCT without the other. The study recommends that the capacity building of pregnant women be optimised, that PMTCT awareness campaigns for women of childbearing age should be a priority and PMTCT skills to be prerequisite for midwives deployed to ANC clinics and maternity ward units. / Health Studies / M.A. (Social Behaviour Studies in HIV/AIDS)

Submitted by Ana Lúcia Torres (bfmhuap@gmail.com) on 2017-09-20T16:29:39Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) CIENCIAS MEDICAS GABRIELA AVILA.pdf: 1035117 bytes, checksum: 1e557cad3ea706ebe746a5080324d310 (MD5) / Approved for entry into archive by Ana Lúcia Torres (bfmhuap@gmail.com) on 2017-09-20T16:29:50Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) CIENCIAS MEDICAS GABRIELA AVILA.pdf: 1035117 bytes, checksum: 1e557cad3ea706ebe746a5080324d310 (MD5) / Made available in DSpace on 2017-09-20T16:29:50Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) CIENCIAS MEDICAS GABRIELA AVILA.pdf: 1035117 bytes, checksum: 1e557cad3ea706ebe746a5080324d310 (MD5) Previous issue date: 2017 / Universidade Federal Fluminense / O padrão da epidemia da infecção pelo vírus da imunodeficiência humana (HIV) entre crianças modificou-se substancialmente nos últimos anos, com declínio no número de novas infecções na população pediátrica após a implementação, em 1994, do protocolo PACTG 076 (Pediatric Aids Clinical Trials Group 076). Posteriormente, o impacto da terapia antirretroviral combinada durante a gestação, primariamente para diminuir a morbidade na mãe, apresentou o benefício adicional da redução das taxas de TVHIV. Este estudo é uma série de casos, cujo objetivo é conhecer o perfil clínico-epidemiológico das gestantes infectadas pelo HIV atendidas no Serviço de Infectologia do Hospital Universitário Antônio Pedro no período de 1998 a 2013, o resultado de suas gestações ea taxa de transmissão vertical do HIV. Foram investigadas 115 gestantes, que resultaram em 152 gestações, através da seleção mediante consulta ao registro de atendimento no ambulatório de Serviço de Infectologia do HUAP. A média de idade das gestantes atendidas foi de 26 anos (desvio padrão - DP = 2,1) e 57,9% eram brancas. A idade gestacional média na primeira consulta foi de 22,8 semanas gestacionais (DP = 7,8). Embora a maioria já soubesse ser portadora do HIV, 46,4% foram diagnosticados em mulheres que não tinham conhecimento do seu estado sorológico. A percentagem de gestações consideradas em imunossupressão grave (CD4 + <200 células / mm3) caiu de 17,9% antes de iniciar a terapêutica anti-retroviral para 8,9% na consulta pré-parto. Houve também um aumento na proporção de mulheres grávidas que atingiram uma carga viral não detectada, de 10,4% para 37,9%. A taxa de transmissão vertical do HIV foi de 1,6%., corroborando para a importância do acompanhamento pré-natal adequado e do tratamento com antirretrovirais potentes, fundamentais para a saúde das gestantes e para prevenção da transmissão do HIV aos recém-nascidos. / The pattern of the human immunodeficiency virus (HIV) epidemic among children has changed substantially in recent years, with a decline in the number of new infections in the pediatric population following the implementation in 1994 of the PACTG 076 protocol (PEDIATRIC AIDS CLINICAL TRIALS GROUP 076). Subsequently, the impact of combination antiretroviral therapy during pregnancy, primarily to reduce maternal morbidity, had the additional benefit of reducing maternal-fetal transmission rates of the virus. This study is a series of cases, whose objective is to know the clinical-epidemiological profile of HIV-infected pregnant women attended the Infectious Disease Department of the Antônio Pedro University Hospital from 1998 to 2013, the outcome of their pregnancies and the vertical HIV transmission rate. 115 pregnant women, resulting in 152 pregnancies, were investigated through the selection by consulting medical records. The mean age of the pregnant women attended was 26 years (standart deviation - ST = 2.1), 57.9% of them were white. The mean gestational age at the first outpatient clinic was 22.8 gestational weeks (ST = 7.8). Although most of them already knew to be HIV carrier, 46.4% were diagnosed in women who were unaware of their serological status. The percentage of pregnancies considered in severe immunosuppression (CD4+ < 200 cells/mm3) fell from 17.9% before starting antiretroviral therapy to 8.9% in the prepartum consultation. There was also an increase in the proportion of pregnant women who achieved an undetected viral load, from 10.4% to 37.9%. The vertical HIV transmission rate was 1.6%, corroborating the importance of adequate prenatal care and treatment with potent antiretroviral drugs, which are essential for the health of pregnant women and for the prevention of HIV transmission to newborns.

Made available in DSpace on 2014-07-29T15:26:22Z (GMT). No. of bitstreams: 1 Tese Keila Correia de Alcantara.pdf: 2967378 bytes, checksum: abcf75d777805ea6de3323b7586a4654 (MD5) Previous issue date: 2010-10-31 / Introduction: The spread of the aids epidemic among young women and HIV-1 mother-tochild transmission (MTCT) represent important public health issues. In this context, prenatal care represents a unique opportunity for the early diagnosis of young women and for the implementation of full preventive strategies to HIV-1MTCT. Objectives: To study immunological, virological, clinical and epidemiological characteristics and to identify factors associated with HIV-1MTCT among HIV-1 pregnant women/infants recruited in Goias State. Material and methods: Cohort 1: 41 pregnant HIV/AIDS: infant pairs (April/2000-August/2001) were recruited and prospectively followed up at two regional reference centers-Mother-Infant Hospital (HMI/SUS) and Hospital Dr. Anuar Auad (HAA/HDT/SUS). Cohort 2: 172 HIV/AIDS pregnant women and 149 exposed children were recruited at the Institute of diagnosis and prevention (IDP/APAE) and prospectively followed up at HAA/HDT/SUS. The following tests were performed: maternal viral load, CD4+ T cell counts, HIV-1env/gag subtypes by heteroduplex mobility assay/HMA (cohort 1) and pol (protease and reverse transcriptase-PR/RT) sequencing for resistance profile, subtypes identification and phylogeography analysis for subtype C (cohort 2). Infants born to HIV-1/aids mothers were evaluated by plasma viral RNA and CD4+ T cell counts. Seroreversion of exposed- uninfected children was followed by sequential ELISA tests for IgG anti HIV-1. Results: Patients from cohorts 1 and 2 presented similar social-demographic and clinical profiles. The median age was 26 years; 15-41 years), lower educational level predominated and most were diagnosed during pregnancy (90%). Over 80% received ARV prophylaxis. One case of MTCT was observed in cohort 1 which was associated with short prophylaxis and long labor period. Exposed-uninfected infants born to symptomatic mothers seroreverted earlier. Cohort 2 included 80% of all HIV-1 infected pregnant women from Goias state in that period. The early prophylaxis and undetectable viral load predominated among previously diagnosed patients (p<0.05). One ARV naive patient presented transmitted drug resistance; 10 ARV experienced patients presented secondary drug resistance: 6 under MTCT prophylaxis, 4 under HAART. MTCT was observed in 3/149 (2.01%) cases and late diagnosis, vaginal delivery, brastfeeding and lack of oral ZDV were observed. Among MTCT cases resistance mutations were not detected. HMA env/gag (cohort 1) and pol sequencing (cohort 2) results showed mostly subtype B followed by subtypes F1, C and recombinants, mainly BF1. HIV-1 subtype C was identified only among pregnant women from cohort 2 which together with recombinants BC represented around 20% of the isolates. Subtype C and BC recombinants were isolated in interior municipalities of Goias state located close to the main highways that connect south/southern to north (BR153), northeast (BR020) and South/west (BR369/BR070). Phylogenetic/ phylogeographic analysis showed a subtype C clado, clusters (aLTR &#8805; 0.85) with sequences from Southern states and from Sao Paulo and evidences of multiple introductions. Conclusion: Our results indicate the importance of prenatal care for the early diagnosis/prevention of HIV-1 vertical transmission. However late diagnosis and missed opportunities to fully prevent transmission were associated with vertical transmission. Multiple introductions and the dissemination of HIV-1 subtype C by heterosexual contact in interior cities highlight the importance of monitoring the genetic diversity and the impact of subtype C dissemination in the interior of Brazil. Note: superscript + is where it appears and the program does not copy. / Introdução: O avanço da epidemia de aids em mulheres jovens e a transmissão materno-infantil do HIV-1 (TMI) representam importantes temas de saúde pública. Neste contexto, a assistência pré-natal representa uma oportunidade única para o diagnóstico da infecção pelo HIV-1 e implementação precoce de medidas profiláticas para TMI. Objetivos: Estudar as características imunológicas, virais, clínicas, epidemiológicas e identificar fatores associados à transmissão materno-infantil do HIV-1 entre gestantes infectadas pelo HIV-1/filhos recrutados no estado de Goiás. Material e métodos: Coorte 1: 41 pares mães HIV/aids-filhos (abril/2000-agosto/2001) recrutados e acompanhados prospectivamente em dois centros de referência regionais (Hospital Materno Infantil/HMI/SUS; Hospital Dr. Auar Auad/HAA/HDT/SUS). Coorte 2: 172 mães HIV/aids-149 filhos recrutados no Instituto de Diagnóstico e Prevenção/IDP/APAE e acompanhados prospectivamente no HAA/HDT/SUS. Foram avaliados viremia plasmática materna, contagem de células T CD4+, subtipos de HIV-1 nas regiões env/gag pelo ensaio da mobilidade de heteroduplex (HMA) para coorte 1 e sequenciamento gene pol (protease e transcriptase reversa-PR/RT) para identificar mutações de resistência aos antirretrovirais e subtipos do HIV-1 e análise filogeográfica das seqüências do subtipo C da coorte 2. As crianças filhas de mães HIV/aids foram submetidas a testes para quantificação do RNA HIV-1 plasmático e das células T CD4+. Nas crianças não infectadas a sororreversão foi acompanhada sequencialmente por ELISA para IgG anti HIV-1/2. Resultados: As pacientes da coorte 1 e 2 apresentaram características sócio-demográficas e clínicas semelhantes. A mediana de idade foi 26 anos (variação 15-41 anos), a maioria tinha baixa escolaridade e foi diagnosticada durante a gestação (90%). Mais de 80% recebeu profilaxia ARV para TMI. Na coorte 1 foi observado um caso de TMI associado a curta exposição à profilaxia e longo trabalho parto. Entre crianças expostas/nãoinfectadas a sororreversão foi mais rápida entre os nascidos de mães sintomáticas. A coorte 2 representou 80% do total de gestantes HIV-1+ do Estado de Goiás no período. A introdução precoce da profilaxia e viremia indetectável predominaram nas pacientes com diagnóstico anterior à gestação (p<0.05). Uma paciente virgem de tratamento apresentou resistência transmitida; 10 pacientes apresentaram resistência secundária: 6 sob profilaxia, 4 sob HAART. Entre os casos de TMI (3/149; 2.01%) observamos diagnóstico tardio, parto vaginal, amamentação e ausência do AZT oral e mutações de resistência não foram detectadas. Resultados do HMA (coorte 1) e do sequenciamento automatizado (coorte 2) em gestantes de Goiás mostraram a circulação dos subtipos B, F1 e recombinantes, principalmente BF1 nas regiões env/gag e pol do HIV-1. O subtipo C só foi detectado na coorte 2 e juntamente com os recombinantes BC representaram em torno de 20% dos isolados. HIV-1 subtipo C, originado do sul do país, foi detectado em gestantes de municípios do interior de Goiás por onde passam importantes vias de ligação sul-norte (BR153), sul-nordeste (BR020) e sulcentro-oeste/Mato Grosso (BR070/BR364). Análises filogenética/filogeográfica do subtipo C mostraram um clado monofilético formado por sequencias de Goias e da região Sul e de São Paulo e evidências de múltiplas introduções em Goiás. Conclusão: Nossos resultados indicam que o programa pré-natal de alta cobertura em Goiás representa uma importante oportunidade para diagnósttico e prevenção precoce de transmissão vertical do HIV-1. Entretanto os 3 casos de TMI observamos diagnóstico tardio e perda de oportunidade para a profilaxia completa da transmissão vertical do HIV-1. Múltiplas introduções e a disseminação do subtipo C por contato heterossexual no interior indicam a necessidade de monitoramento da diversidade genética e do impacto da disseminação do subtipo C no interior do Brasil. OBS: + está sobrescrita onde aparece e o programa não copia.

<p>The study aimed to assess the level of adherence and to identify the barriers to adherence and the motivations for good adherence to antiretroviral therapy, amongst women who commenced treatment while pregnant at research clinics in Molepolole, Mochudi, Lobatse and Gaborone.</p>

La transmission mère-enfant (TME) du VIH-1 est un des enjeux majeurs de la pandémie. Une meilleure compréhension de la réponse des lymphocytes T cytotoxiques CD8+ (LTC) VIH-spécifiques lors de la grossesse facilitera le design de stratégies optimales pour diminuer la TME. Notre objectif est donc de caractériser l’amplitude et la diversité de la reconnaissance antigénique des LTC VIH-spécifiques avant, pendant et après la grossesse chez des femmes infectées par le VIH-1. Nos résultats montrent pour la première fois que l’initiation et la progression de la grossesse, à elles seules, n'ont que peu d’influence sur l’amplitude et la diversité de la reconnaissance antigénique des réponses LTC en termes de production d’IFN‐. Ces résultats indiquent que les femmes infectées par le VIH conservent une immunocompétence durant leur grossesse, du moins dans le contexte d’un traitement antirétroviral efficace. Ceci pourrait éventuellement aider à promouvoir l’immunisation comme stratégie pour prévenir la TME du VIH‐1. / Mother-to-child transmission (MTCT) of HIV-1 is one of the major issues of the pandemic. Characterization of HIV-specific immunity during pregnancy, especially cytotoxic CD8+ T lymphocytes (CTL), will lead to a better understanding of HIV pathogenesis and facilitate design of optimal strategies to prevent MTCT. Our objective is to describe the magnitude and the breadth of antigen recognition of HIV-specific CTL responses before, throughout and after pregnancy in a group of HIV-infected women. Our results revealed for the first time that initiation of pregnancy by itself doesn’t change the magnitude of CTL responses in terms of IFN- production. These findings support the fact that HIV-infected women maintain immunocompetence throughout gestation, at least in the context of effective antiretroviral treatment. These results provide a novel understanding of the dynamics of HIV-specific CTL responses during pregnancy and may help to promote maternal immunization as a strategy to prevent MTCT of HIV-1.

<p>The study aimed to assess the level of adherence and to identify the barriers to adherence and the motivations for good adherence to antiretroviral therapy, amongst women who commenced treatment while pregnant at research clinics in Molepolole, Mochudi, Lobatse and Gaborone.</p>

La transmission mère-enfant du VIH-1 (TME) représente le principal mode d’infection chez l’enfant et se produit durant la grossesse (in utero, IU), l’accouchement (intrapartum, IP) ou l’allaitement (postpartum, PP). Les mécanismes qui sous-tendent le passage du VIH-1 à travers le placenta et les muqueuses intestinales du nouveau-né sont encore très peu décrits. « Dendritic cell-specific ICAM-grabbing non-integrin » (DC-SIGN) et son homologue DC-SIGN « related » (DC-SIGNR) sont des récepteurs d’antigènes exprimés au niveau du placenta et capables de capter et de transmettre le VIH-1 aux cellules adjacentes. Ils pourraient donc participer au passage trans placentaire du VIH-1 et le polymorphisme génétique affectant l’expression ou modifiant l’interaction avec le virus aurait une influence sur la TME du VIH-1. Afin d’explorer cette hypothèse, nous avons procédé à une analyse exhaustive du polymorphisme de DC-SIGN et DC-SIGNR dans la population du Zimbabwe. Par la suite, nous avons déterminé l’association entre le polymorphisme de DC-SIGN et DC-SIGNR et la TME du VIH-1 dans une cohorte d’enfants nés de mères VIH-positives à Harare, au Zimbabwe. Enfin, nous avons défini l’impact fonctionnel des mutations associées. Les enfants homozygotes pour les haplotypes H1 et H3 dans le gène de DC-SIGNR sont 4 à 6 fois plus à risque de contracter le VIH-1 par voie IU et IP. H1 et H3 contiennent la mutation du promoteur p-198A et la mutation de l’intron 2, int2-180A, et des études fonctionnelles nous ont permis de démontrer que p-198A diminue l’activité transcriptionnelle du promoteur de DC-SIGNR et l’expression des transcrits d’ARNm dans le placenta, alors que int2-180A modifie le répertoire d’isoformes de DC-SIGNR vers une proportion diminuée d’isoformes membranaires. Les enfants porteurs des haplotypes H4 et H6 de DC-SIGN sont 2 à 6 fois plus à risque de contracter le VIH-1 par voie IU. Ces haplotypes contiennent deux mutations du promoteur (p-336T/C et p-201C/A) et quatre mutations codant pour un changement d’acide aminé dans l’exon 4 (R198Q, E214D, R221Q ou L242V) associées à un risque augmenté de transmission IU, IP et PP du VIH-1. Des études fonctionnelles ont démontré que les mutations du promoteur diminuent l’expression de DC-SIGN dans les macrophages placentaires. Toutefois, l’exposition IU au VIH-1 module le niveau d’expression de DC-SIGN, résultant en des niveaux d’expression similaires entre les macrophages des porteurs des allèles sauvages et mutés. Les mutations de l’exon 4 augmentent l’affinité de DC-SIGN pour le VIH-1 et sa capacité à capturer et à transmettre le virus aux lymphocytes T, favorisant possiblement la dissémination du VIH-1 à travers le placenta. L’association entre les mutations de DC-SIGN et la transmission IP et PP du VIH-1 suggèrent qu’il aurait aussi un rôle à jouer dans les muqueuses intestinales de l’enfant. Notre étude démontre pour la première fois l’implication de DC-SIGN et DC-SIGNR dans la TME du VIH-1. L’augmentation des capacités de capture et de transmission de DC-SIGN résulte en une susceptibilité accrue de l’enfant à l’infection au VIH-1 et concorde avec un rôle dans la dissémination transplacentaire. Toutefois, la diminution préférentielle des transcrits membranaires de DC-SIGNR au placenta augmente la TME du VIH-1 et laisse croire à son implication via un autre mécanisme. Ces mécanismes pourraient aussi s’appliquer à d’autres pathogènes reconnus par DC-SIGN et DC-SIGNR et transmis de la mère à l’enfant. / Mother-to-child transmission (MTCT) is the main cause of HIV-1 infection in children worldwide. MTCT of HIV-1 can occur during pregnancy (in utero, IU), delivery (intrapartum, IP) or breastfeeding (postpartum, PP). Dendritic cell-specific ICAM-grabbing non-integrin (DC-SIGN) and its homolog DC-SIGN related (DC-SIGNR) are attachment receptors for HIV-1 and are expressed in the placenta. They have been implicated in viral capture and transmission to T cells. To investigate the potential role of DC-SIGN and DC-SIGNR in MTCT of HIV-1, we carried out a genetic association study in a well-characterized cohort of 197 HIV-infected mothers and their infants recruited in Harare, Zimbabwe. Infants harbouring two copies of DC-SIGNR H1 and/or H3 haplotypes (H1-H1, H1-H3, H3-H3) had a 4-fold increased risk of IU and 6-fold increased risk of IP HIV-1 infection after adjusting for a number of maternal factors. The implicated H1 and H3 haplotypes share two single nucleotide polymorphisms (SNPs) in promoter region (p-198A) and intron 2 (int2-180A) that were associated with increased risk of both IU and IP HIV-1 infection. The promoter variant reduced transcriptional activity in vitro. In homozygous H1 infants bearing both the p-198A and int2-180A mutations, we observed a 4-fold decrease in the level of placental DC-SIGNR transcripts, disproportionately affecting the expression of membrane-bound isoforms compared to infant noncarriers. Infants carrying H4 and H6 haplotypes in DC-SIGN gene were more likely to be HIV-1-infected during pregnancy. These haplotypes contain promoter variants (p-336T/C and p-201C/A) and exon 4 variants (R198Q, E214D, R221Q and L242V) that were all significantly associated with increased risk of MTCT of HIV-1. Compared with wild-type sequence, the promoter variants reduced both the DC-SIGN transcription in vitro and expression (2-fold) in placental macrophages of HIV-1-unexposed infants. However, in HIV-1-exposed infants, the level of DC-SIGN expression in placental macrophages was similar in infants carrying either the promoter wild-type or variant sequences. Exon 4 variants increased HIV-1 capture and transmission to T cells in vitro. Association between DC-SIGN SNPs and HIV-1 IP and PP infection also suggests that DC-SIGN plays an important role in intestinal mucosa. This is the first study reporting on functional impact of DC-SIGN and DC-SIGNR natural polymorphisms on HIV-1 transmission from mother-to-child. Decreased levels of expression of membrane DC-SIGNR isoforms at the placental endothelial cell surface increased child susceptibility to HIV-1. Presence of DC-SIGN variants increasing its affinity for the virus augmented child susceptibility to HIV-1 and may favour viral dissemination across the placental barrier. This study provides compelling evidence to support an important role of DC-SIGN and DC-SIGNR in various modes of MTCT of HIV-1 and shed light on the possible mechanisms involved in HIV-1 passage from mother-to-infant. These findings raise the possibility that similar mechanisms may operate with other human pathogens known to interact with DC-SIGN and DC-SIGNR.

225 leaves printed on single pages, preliminary pages i- xxiii and numbered pages 1-203. Includes bibliography, list of abbreviations, list of definitions, list of tables and figures and list of appendices. / Digitized at 330 dpi color PDF format (OCR), using KODAK i 1220 PLUS scanner. / Thesis (MNutr (Interdisciplinary Health Sciences))--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: "A comprehensive package of care for the Prevention of Mother- To-Child Transmission (PMTCT) of HIV" states that all mothers participating in the PMTCT Programme should receive education that will enable them to make informed decisions about infant feeding options. Rapid, same-day HIV testing and results that are available immediately, enable health care workers to be responsible for providing pre- and post-test counselling (which includes infant feeding options) on the same day. This could place a tremendous workload and time pressure on the health care workers. The aim of this study was to determine how "informed" is the literate mother's decision regarding infant feeding options, who participated in the PMTCT Programme, in the Gert Sibande District, Mpumalanga, South Africa. Method: Data was collected from health care workers and mothers on the PMTCT Programme at 23 PMTCT sites in the Gert Sibande District, with the help of 6 field workers and the PMTCT site manager at each PMTCT site, by means of once-off, self-administered questionnaires, which had been previously tested and validated. Results: Health care workers' attitude towards the PMTCT Programme was positive, although some (14%) indicated that what was expected of them was not achievable in their working environment. The most prominent change relating to the personal preferences of health care workers regarding infant feeding options for HIV-infected mothers, after attending the 5-day PMTCT course, was from formula-feeding to breast-feeding. Most (65%) indicated it was possible to stay neutral in a counselling session regardless of personal preference for infant feeding and 60% of those who could not stay neutral, still thought it was in the mother's best interest to be counselled by them. Most (98%) agreed mothers had the right to make informed decisions and 80% agreed mothers were able to make such a decision. Most (67%) health care workers indicated that not enough staff was stationed at PMTCT sites, only 53% used the feeding option cards when counselling mothers and indicated that more educational material was needed. Sixty one percent of the health care workers demonstrated the preparation of the formula to the mothers and allowed the mothers to demonstrate back to them. Between 49-82% and 37-56% of the health care workers knew the correct answers to knowledge questions relating to breastfeeding and formula-feeding, respectively. Not one health care worker, nor mother, knew all the steps in preparing a formula feed. Most (80%) mothers made decisions based on information provided to them by health care workers and only a small (13%) percentage were influenced by the community to practise a different feeding option than what they had chosen. Conclusions: The attitude, personal preferences, knowledge of and resources available to health care workers, influenced the decision made by mothers regarding infant feeding options and seeing that most mothers made their decision, based on information provided by health care workers, it is concluded that mothers can only make an informed decision about infant feeding options if they are advised appropriately by well trained, equipped and informed health care workers. / AFRIKAANSE OPSOMMING: "A comprehensive package of care for the Prevention of Mother-To-Child Transmission of HIV", vermeld dat moeders, wat deelneem aan die Voorkoming van Moeder-Tot-Kind Oordrag (VMTKO) progam, voorligting behoort te ontvang ten opsigte van voedingsopsies vir hul babas, sodat hulle in staat sal wees om 'n ingeligte keuse te maak. Gesondheidswerkers is verantwoordelik om voorligting voor en na die HIV toets te gee, wat die voedingsopsies vir babas insluit, op dieselfde dag. Dit kan 'n ontsaglike werkslading op die gesondheidswerkers plaas. Die doel van die studie was om te bepaal hoe "ingelig" is die geletterde moeder se keuse ten opsigte van voedingsopsies, wat deelneem aan die VMTKO program, in die Gert Sibande distrik, Mpumalanga, Suid-Afrika. Metode: Die data is ingesamel by 23 VMTKO-klinieke en -hospitale in die Gert Sibande distrik onder gesondheidswerkers en moeders op die VMTKO-program, met behulp van 6 veldwerkers en VMTKO-bestuurders, deur middel van eenmalige, selfvoltooide vraelyste, wat van tevore getoets en gevalideer was. Resultate: Die gesondheidswerkers se houding teenoor die VMTKO-program was positief, alhoewel 14% aangedui het dat wat van hulle verwag word nie prakties of moontlik is in hul werksomgewing nie. Die prominentste verandering rakende die persoonlike voorkeure van die gesonheidswerkers teenoor voedingsopsies vir HIV -geinfekteerde moeders, na die 5-dag VMTKO kursus, was van formulevoeding na borsvoeding. Meeste (65%) het aangedui dit is moontlik om neutraal te bly gedurende 'n voorligtingssessie, ten spyte van persoonlike voorkeure vir voedingsopsies en 60% van die wat nie neutraal kon bly nie, het steeds gedink dit is in die beste belang van die moeder om deur hulle voorgelig te word. Meeste (98%) het saamgestem dat dit die moeder se reg is om 'n ingeligte keuse te maak en 80% het saamgestem dat die moeder wel in staat is om so 'n besluit te neem. Meeste (67%) gesondheidswerkers het aangedui dat personeel tekorte bestaan by die VMTKO klinieke en hospitale. Slegs 53% gebruik die voedingsopsie kaarte gedurende 'n voorligtingsessie met die moeder en het aangedui dat meer voorligtingsmateriaal benodig word. Een en sestig persent van die gesondheidswerkers het die voorbereiding van die formulevoeding aan die moeders gedemonstreer en het moeders toegelaat om ook die demonstrasie te doen. Nege en veertig tot twee en tagtig persent en 37-56% van die gesondheidswerkers kon die korrekte antwoorde verskaf vir vrae oor borsvoeding en formulevoeding, afsonderlik. Nie een gesondheidswerker of moeder kon al die stappe vir die voorbereiding van die formulevoeding noem nie. Meeste (80%) moeders maak keuses gebaseer op inligting wat aan hulle verskaf word deur die gesondheidswerkers en slegs 'n klein persentasie (13%) word beinvloed deur familielede om die teenoorgestelde voedingsopsie te praktiseer as wat hulle gekies het. Gevolgtrekking: Die houding, persoonlike voorkeure, kennis van en hulpbronne beskikbaar aan die gesongheidswerkers, beinvloed die besluit wat moeders neem ten op sigte van voedingsopsies en aangesien die moeders hulle besluit baseer op inligting wat deur die gesondheidswerkers aan hulle gegee word, word die gevolgtrekking gemaak dat moeders slegs 'n ingeligte keuse aangaande voedingsopsies kan maak indien hulle voorligting ontvang deur goed opgeleide en ingeligte gesondheidswerkers.