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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Distinct vaccine-induced antibody responses and bispecific neutralizing immunoadhesins against SIV/HIV infection

Guo, Jia, 郭佳 January 2013 (has links)
Our research laboratory has recently reported that mucosal priming with a replicating modified vaccinia Tiantan virus (MVTTgpe)-based vaccine elicits durable protection against pathogenic SIVmac239 infection in rhesus monkeys. However, the protective role of vaccine-elicited antibody responses remains poorly understood. Here, a novel yeast surface displayed (YSD) antigen library was established to quantitatively map the antigenic determinants presented by MVTTgpe-based and control vaccines as well as by SIVmac239 infection. The YSD-library allows the mapping of linear and some conformational epitopes as a major technical innovation, as validated by testing SIV-specific mAbs KK65, KK8 and VM-18S. While eight antigenic domains are characterized covering the entire SIVmac239 gp160, the MVTTgpe/Ad5gpe regimen uniquely induces antibody responses against a distinct major antigenic determinant (MAD) in V2 region as compared with the Ad5gpe/Ad5gpe vaccination and SIV infection. This MAD is associated with a higher titer of anti-V2 antibody responses, which inversely correlates with peak viral load. Unexpectedly, the MVTTgpe/Ad5gpe vaccine- challenge. The results showed that instead of recalling B cell memory response to V2, viral infection presents a distinct set of antigenic determinants with anti-V1V2 antibodies primarily directed to V1 region. Moreover, the anti-V1V2 antibody responses disappear in two infected macaques after they enter the stage of simian AIDS. SIVmac239 infection, therefore, can modulate vaccine-elicited B cell immunity by diminishing anti-V2 antibody memory responses in rhesus monkeys. These findings implicated that vaccine efforts with focus on V2 region would require periodic vaccinations to maintain a long-lasting high level of antibody responses for protection. In the absence of an effective vaccine for eliciting HIV-1-specific broadly neutralizing antibodies (bNAbs), passive immunization with bNAbs or Ab-like agents (e.g. immunoadhesin) becomes an attractive alternative for HIV-1 prevention. In this study, we aimed to design, optimize and produce secretory immunoadhesins (IAs) based on gene engineering of existing HIV-1 specific bNAbs for potency and production improvements. IAs are chimeric, antibody-like molecules that combine the functional domain of bNAb with immunoglobulin constant domains, including the hinge and Fc regions. We found that the modified secretory IAs not only preserved the neutralization activity of the parental bNAbs, but also had enhanced expression and smaller molecular size that is suitable for antibody gene-based in vivo delivery. Furthermore, we defined the synergistic effects of five IAs against HIV-1 infection and subsequently engineered two types of bi-specific IAs by combining the functional domains of Hu5A8, a humanized anti-CD4 antibody, and the bNAb PGT128. Significantly, one of the bi-specific IA, namely Bi-IA-Mono, neutralized 100% of the 33 viruses tested, including the transmitted/founder viruses and viruses resistant to both parental IAs. The remarkably enhanced neutralization activity of Bi-IA-Mono, either in potency and breadth, indicated the great potential of modified bi-specific IA to provide complete or nearly complete protection against major HIV-1 subtypes. Overall, our results demonstrated that the engineering of IA and bi-specific IA is an attractive way to improve anti-HIV-1 properties of existing bNAbs, which have significant implications for antibody-based prophylactics in blocking diverse HIV-1 transmissions and infections. / published_or_final_version / Microbiology / Doctoral / Doctor of Philosophy

Systematic reviews and economic evaluation of HIV behavioural interventions in China.

Wang, Shuhong January 2007 (has links)
Title page, contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / This thesis focuses on behavioural interventions for preventing sexual transmission of HIV. The international literature on the evaluation of this type of intervention largely originates from developed countries and from Africa. China, where the AIDS epidemic is growing rapidly, lacks rigorous evaluation studies to determine the effectiveness of HIV prevention activities. This study develops a model to inform decision-making based on evidence generated in settings other than those for which policy is being developed. This model is illustrated through two case studies in China, the first on HIV/AIDS prevention strategies targeting young people, and the second on men who have sex with men. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1284184 / Thesis (Ph.D.) -- University of Adelaide, School of Population Health and Clinical Practice, 2007

Systematic reviews and economic evaluation of HIV behavioural interventions in China.

Wang, Shuhong January 2007 (has links)
Title page, contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / This thesis focuses on behavioural interventions for preventing sexual transmission of HIV. The international literature on the evaluation of this type of intervention largely originates from developed countries and from Africa. China, where the AIDS epidemic is growing rapidly, lacks rigorous evaluation studies to determine the effectiveness of HIV prevention activities. This study develops a model to inform decision-making based on evidence generated in settings other than those for which policy is being developed. This model is illustrated through two case studies in China, the first on HIV/AIDS prevention strategies targeting young people, and the second on men who have sex with men. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1284184 / Thesis (Ph.D.) -- University of Adelaide, School of Population Health and Clinical Practice, 2007

Knowledge of safe sex practices and HIV transmission, propensity for risk taking, and alcohol/drug use in the aetiology of unprotected sex

Simpson, Malcolm Robert January 1997 (has links)
Second year psychology students (N=176) from Rhodes University were surveyed using an anonymous questionnaire to obtain information on sexual behaviour and knowledge of the acquired immunodeficiency syndrome (AIDS) among young people. The following information was obtained: Knowledge of safe sex practices and HIV transmission was high although a number of misconceptions were noted. Only fifty six percent of students viewed oral sex with a condom as safe and thirty one percent do not consider mutual masturbation with a condom safe. Thirteen percent and twenty five percent respectively identified insects and saliva as being routes of HIV transmission. Magazines (96%), informal discussions with friends (95%), public pamphlets (86%) and public television (79%) were preferred sources of information. The students' knowledge did not appear to significantly affect sexual behaviour. Eighty percent of respondents were intimately involved with another person during the past twelve months, and only fifteen percent always made use of a latex barrier when being sexually intimate. Despite high rates of alcohol and/or drug consumption (80% of students use such substances), and the belief by the majority of respondents that alcohol and/or drugs facilitate higher risk behaviours, no support for the alcohol/risky sex hypothesis was found. Students were found to score highly on proneness to psychological and behavioural risk taking, and no significant relationship between this and unprotected sex was found. It can be concluded that educational programmes need to focus on what constitutes safe sexual practices in order to equip young adults with the knowledge they need to make informed choices regarding the relative risks of various sexual activities.

Founder virus envelope glycoproteins as novel oligomeric HIV-1 vaccine immunogens

Killick, Mark Andrew 21 April 2015 (has links)
A thesis submitted to Faculty of Health Sciences, University of the Witwatersrand, in fulfillment of the requirements for the degree of Doctor of Philosophy Johannesburg, March 2014 / The ability to induce a broadly neutralizing antibody (bNAb) response following vaccination is regarded as a crucial aspect in developing an effective vaccine targeting the human immunodeficiency virus type 1 (HIV-1). The bNAbs target the HIV-1 envelope glycoprotein (Env) which is exposed on the surface of the virion, thereby preventing cell entry. Previous work in our laboratory focused on the generation of a 2dCD4S60C molecule (a variant of the CD4 primary Env receptor) with higher affinity for HIV-1 Env through targeted disulphide exchange. This study reports on the design and construction of an HIV-1 subtype C founder virus consensus Env immunogen derived from newly transmitted/founder virus sequences, and the ability of the purified recombinant Env proteins (2dCD4S60C-liganded and unliganded) to induce a broadly neutralizing antibody response in small animals. A total of 1894 founder sequences from 80 HIV-1 subtype C infected patients were available and downloaded from the databases. A consensus sequence was generated for each of the patients, and this alignment was subsequently used to generate a founder virus consensus env sequence. The env sequence was used to create codon-optimized constructs encoding monomeric (gp120FVCm), dimeric (gp120FVCGCN4d) and trimeric (gp140FVCGCN4t(+) and gp140FVCGCN4t(-) founder virus conformations cloned into the pcDNA3.1(-) mammalian expression vector. All four Env constructs were successfully expressed in HEK293T mammalian cell culture. The 2dCD4S60C was expressed in E. coli BL21 (DE3) and purified by nickel affinity chromatography. Large scale expression and purification of the gp120, gp120GCN4 and gp140GCN4 +/- in the unliganded or 2dCD4S60C liganded state were purified by lectin affinity chromatography, followed by conformation and complex purification using size exclusion chromatography. Immunogens/immune complexes were evaluated by ELISA, SDS-PAGE, native PAGE and surface plasmon resonance, and confirmed they were functional and conformationally intact. Immunogenicity of each conformation alone or complexed to 2dCD4S60C was evaluated in rabbits. Breadth and potency of the rabbit sera was tested against 12 pseudoviruses (Tiers 1-3), derived from HIV-1 subtype B and C Env, using the PhenoSense Neutralizing antibody assay (Monogram Bioscience, Inc.). Minimal neutralizing breadth was obtained from animals immunized exclusively with Env conformations. However, animals that received the Env/2dCD4S60C complex showed extensive neutralizing capacity against all 12 viruses tested, including the tier 2 and 3 virus strains. End-point ELISA titer results revealed that the rabbits that were immunized with Env/2dCD4S60C produced both Env and 2dCD4S60C specific titers, but those directed towards 2dCD4 were on average 10x lower than the 2dCD4S60C control group. This implies a proportion of the NAb activity is directed towards conserved epitopes exposed on the Env/2dCD4S60C immunogens. Overall, these results show that the use of founder Env/2dCD4S60C complexes as vaccine immunogens dramatically improves the antibody neutralization breadth and magnitude as compared to founder Env or 2dCD4S60C alone. This level of broad neutralization has not been previously reported in the literature, and these results provide encouraging data to inform us of the best envelope vaccine immunogen to include in a preventative vaccine.

Sensitivity of HIV-1 subtype C viruses to Griffithsin, cyanovirin-N and scytovirin: potential HIV-1 microbicides

Alexandre, Kabamba Bankoledi 07 May 2013 (has links)
Thesis (Ph.D. (Virology))--University of the Witwatersrand, Faculty of Health Sciences, 2012 / The majority of HIV-1 infections around the world occur via sexual intercourse and women, especially in developing countries, are disproportionately affected. Recently a number of strategies have been proposed to control the spread of HIV, among these the use of microbicides to prevent the sexual transmission of the virus. A clinical trial of 1% tenofovir gel that conferred up to 39% protection provided a proof-of-concept that an anti-HIV microbicide is feasible. Various other compounds, acting at different stages of HIV-1 life cycle, are also being investigated as potential microbicides. These include the lectins Griffithsin (GRFT), cyanovirin-N (CV-N) and scytovirin (SVN). GRFT was isolated from the red algae griffithsia sp. while CV-N and SVN were isolated from the blue green alga Nostoc ellipsosporum and the cyanobacterium Scytonema varium, respectively. These lectins bind mannose-rich glycans found on the surface of HIV-1 envelope and act as entry inhibitors. Although HIV-1 subtype C is the main cause of infections around the world, almost all studies conducted with GRFT, CV-N and SVN are based on subtype B viruses. The Chapter Two sought to establish the neutralization sensitivity of HIV-1 subtype C viruses to the three lectins, using both a cell line and primary cells, and compared this sensitivity to subtype B. This Chapter also examined mannose-rich glycans on HIV-1 that are involved in GRFT, CV-N and SVN binding. The conclusion from this study was that the neutralization of subtype C viruses by these lectins is similar to subtype B and that the 234 and 295 mannose-rich glycans were involved in their interaction with the virus. In general these data supported further studies on the use of GRFT, CV-N and SVN for prevention of HIV-1 subtype C sexual transmission. In Chapter Three, the ability of GRFT to expose the CD4 binding site (CD4bs) on HIV-1 gp120 is explored. I found that this exposure resulted in the enhancement of HIV-1 binding to plates coated with anti-CD4bs antibodies b12 and b6 or the CD4 receptor mimetic CD4-IgG2. This lectin also synergized with b12 and HIVpositive plasma containing antibodies to the CD4bs to neutralize the virus. Furthermore, the glycan at position 386, which shields the CD4bs, was shown to be involved in both GRFT enhancement of HIV-1 binding to b12 and b6 and in the synergistic interaction between the lectin and these antibodies. The importance of this study is that it investigated in details the effect of GRFT binding on HIV-1 envelope and also suggests this lectin can be used in combination with anti-HIV-1 antibodies to synergistically enhance the anti-viral activity. In Chapter Four I investigated GRFT, CV-N and SVN inhibition of the virus binding to the DC-SIGN receptor and their inhibition of the DCSIGN transfer of HIV-1 to target cells. These lectins only moderately inhibited the virus binding to the receptor while they potently inhibited its transfer to target cells. However, the inhibition of transfer was stronger when the virus bound the lectins after binding the DC-SIGN receptor compared to when it bound the lectins prior to binding the receptor. These three lectins can, therefore, inhibit the sexual transmission of HIV-1 since the DCSIGN- mediated transfer of the virus to susceptible cells is pivotal to this mode of transmission. Chapter Five is an investigation of the ability of HIV-1 subtype C to escape GRFT, CV-N and SVN, which involved growing the virus under escalating concentrations of these compounds. This was to know how this virus behaves under conditions of continuous exposure to the lectins. I found that HIV-1 subtype C became increasingly resistant to the lectins and viral envelope sequence analysis showed that this was associated with the deletion of mannose-rich glycans on gp120. Furthermore, of the 11 potential mannose-rich glycosylation sites on gp120 seven (230, 234, 241, 289, 339, 392 and 448) were involved in GRFT, CV-N and SVN resistance. Thus, the conclusion was that although these three lectins are potent inhibitors of HIV-1 infection, the virus is also able to escape their neutralization by deleting mannose-rich glycans on its envelope. However, the fact that escape to these lectins involved multiple deglycosylation and was only partial suggests that HIV-1 subtype C escape from GRFT, CV-N and SVN in a microbicide formulation may not be an easy process. We discuss the implications of these findings in Chapter Six and suggest future studies that could complement data presented in this thesis. Overall our data show that GRFT, CV-N and SVN can prevent the sexual transmission of both free and DC-SIGN associated HIV-1 particles and supports further development of these lectins as microbicides against HIV-1.

Motivations to either accept or reject pre-exposure prophylaxis: awareness, beliefs, and risk perceptions among African American women in New York City

Robinson Davis, Suzanne January 2018 (has links)
The world has suffered immensely and disproportionately from the ravages of HIV and AIDS. Oral PrEP is a single pill taken once daily that can reduce the risk of sexually transmitted HIV infection by up to 92% (CDC, 2014a). This study describes African American females’ awareness, beliefs, and perception of PrEP and identifies factors that may motivate women to either accept or reject PrEP. This cross-sectional study occurred over a 3-month period from November 2017 to January 2018, following from a previous pilot study. The sample comprised African American women aged 18 and over receiving STD or HIV screening services at a FQHC in Brooklyn, New York. Women were interviewed using the five characteristics of the Diffusion of Innovation theory and also completed a risk assessment for HIV using CDC recommended guidelines for screening heterosexual women for PrEP. Awareness of PrEP remained extremely low among the 72 African American women interviewed in the study. Using the CDC guidelines, all women reported one or more risk factors for PrEP indication. Awareness about PrEP, negative reactions from partners and shared experiences from female PrEP users were cited as factors that may predict and motivate African American women to use PrEP. Additionally, skills in pill-taking, cost and insurance, and maintaining privacy while using PrEP were strong enabling factors to support PrEP use. Factors such as initiating couple’s PrEP use as an intervention, medical doctors overtly directing PrEP for women, and the role of older women in promoting PrEP use were persuasive factors in reinforcing the utilization of PrEP among African American women in the study. Creative programming within high burden communities is critically important to penetrate with messages of new innovations and best practices. The results of the current research speak volumes to the continued work needed to educate communities with prevention messages.

Nurses’ counseling to mothers to prevent mother to child transmission of HIV through breastfeeding : A qualitative study

Staflin, Emma, Lundkvist, Jennie January 2011 (has links)
Introduction: HIV is a serious problem in Namibia, 13.1% of the adult population is HIV-positive or is a carrier of AIDS. This is one of the highest numbers in the world. HIV is passed from mother to child during pregnancy, during labour or through breast milk. 18.8 % of the pregnant mothers in Namibia who is in contact with the maternity welfare have HIV. Aim: The aim of the study was to describe nurses’ counseling to mothers to prevent mother to child transmission of HIV through breastfeeding. Method: Eight nurses working with PMTCT of HIV were interviewed in Namibia. The interviews were transcribed and a content analysis was made. 18 sub-categories and seven categories were found. Findings: It is important that nurses provide individual counseling, are supportive and motivate the mothers. Poverty is an obstacle for the mothers, stigmatization occurs and cultural differences can have influence on the mothers. It is also important that nurses are updated in counseling and PMTCT. Conclusion: Nurses should provide mothers with the correct information in a pedagogical way. Nurses need to be aware of obstacles for the mothers and their families to be able to meet their different demands. Men are not involved in PMTCT-counseling and nurses think that partner involvement would benefit PMTCT of HIV.

Antiretroviral prophylaxis for prevention of mother to child transmission of HIV through breastfeeding: asystematic review and meta-analysis of infant treatment regimens

Wu, Lucy, Mimi. January 2012 (has links)
A systematic review and meta-analysis was conducted to evaluate the efficacy of different infant antiretroviral (ARV) prophylaxis regimens for prevention of mother to child transmission (MTCT) of human immunodeficiency virus (HIV) infection in breastfeeding infants who were born to HIV positive mothers but were HIV uninfected at birth. The systematic review of the literature published during January 2000 to April 2012 resulted in ten randomized and controlled clinical studies which met the study inclusion criteria. Two datasets were identified from the ten selected clinical trials. One dataset contains six studies evaluating short-course ARV prophylaxis regimens, and the second dataset contains four studies evaluating short-course versus extended ARV prophylaxis regimens. The odds ratio was used as the effect size to measure the efficacy between two comparative infant ARV prophylaxis regimens. Meta-analyses were conducted to assess the overall (pooled) treatment effect of the two comparative infant ARV prophylaxis regimens of the two datasets. The pooled ARV treatment effect was calculated as a weighted average of the effect estimated in the individual studies. If no heterogeneity was identified, a fixed-effect meta-analysis by the Mantel-Haenszel method was used. The random-effects method was used when there was heterogeneity in the meta-analysis. The inverse-variance method was used in the random-effects method of meta-analysis. Heterogeneity in the meta-analysis was accessed by the Chi-squared (χ2) test and I2 test. The combined sample size of all ten clinical trials was a total of 10,316 breastfeeding infants, and the overall postnatal HIV transmission rate regardless of ARV regimens and the timing of HIV infection status was approximately 8.7%. The overall HIV transmission rates of the short-course ARV prophylaxis regimen groups were 10.3% at 4-8 weeks and 9.0% at 6-9 months, respectively. The overall late postnatal HIV transmission rate (at 6-9 months after birth) was 5.5% in the extended ARV prophylaxis regimen group. The first dataset contains six randomized and controlled studies to evaluate the efficacy outcome (defined as the unadjusted HIV infection status at 4-8 weeks after birth) of two short-course infant ARV prophylaxis regimens, the nevirapine (NVP) regimen and the zidovudine (ZDV) with or without combination of lamivudine (3TC) or NVP regimen. Due to the existence of substantial heterogeneity, a random-effects method was used to test for the overall treatment effect. The results show that there was no significant difference between the two short-course infant ARV prophylaxis regimens (odds ratio:1.07; 95% CI: 0.69-1.66; Z=0.31, p=0.76). The results of the meta-analysis of five comparative short-course versus extended infant ARV prophylaxis regimens from four randomized and controlled clinical trials, demonstrate a favorable efficacy outcome (defined as the unadjusted HIV infection status at 6-9 months after birth), of the extended ARV regimens. There was no heterogeneity found in this dataset. There was a highly significant difference in the overall effect between the two ARV prophylaxis regimens by a fixed-effect model (odds ratio: 1.72; 95% CI:1.45-2.04; Z=0.68, p<0.00001). In summary, there was no significant difference in the overall treatment effect in reducing the early postnatal MTCT of HIV infection by infant short-course regimens of ARV prophylaxis, which include NVP, ZDV and their combination regimens. In comparison with the short-course ARV regimens, the extended ARV prophylaxis further reduced the risk of the late postnatal MTCT of HIV infection in breastfeeding infants. / published_or_final_version / Public Health / Master / Master of Public Health

Parenting in the time of AIDS.

Paruk, Zubeda. January 2011 (has links)
This thesis reports on a formative evaluation study conducted, firstly, to inform an adaptation of the Collaborative HIV Prevention and Adolescent Mental Health Program (CHAMP) so as to strengthen the adult protective shield in order to prevent high risk behaviour and HIV among children in the targeted community in Embo, Kwadedangendlale, KwaZulu-Natal (Study 1); and secondly, after a pilot intervention, to evaluate the adapted programme in order to understand the processes involved in strengthening the adult protective shield (Study 2). The research design for both Study 1 and Study 2 was qualitative in nature. More specifically, the two studies used a focused ethnographic case study approach. Thematic content analysis was used to analyse the data from both studies and three theoretical approaches facilitated the understanding of the data: Joffe’s psychoanalytic extension of social representation theory, Carpiano’s integrative theory of social capital, and Campbell and Murray’s critical approach to community health psychology. The participants in the first study were a volunteer convenience sample of parents of children aged 9-12 years from a school in the targeted community. Focus groups and in depth follow up interviews were conducted with the parents. Interviews were also conducted with key members of the community. At the community level, lack of containment emerged as an overarching theme, with splitting and lack of trust as subthemes interpreted as emerging to deal with anxiety. Anxiety was also linked to stigmatization of people suspected of being HIV positive or having AIDS. Coping mechanisms used to deal with stigmatization were silence and denial. Linked to the issue of stigmatization was that of death and bereavement. At the family level, disempowerment of caregivers emerged as an overarching theme creating anxiety for parents, one of the sources of which was the generational knowledge gap, with parents being generally less educated than their children. This was linked to two issues: that of children’s rights; and parents’ attempts to resort to severe forms of authoritarian parenting. In the second study, in-depth semi-structured interviews, based on the themes that had emerged from the pre-intervention focused ethnographic study, were conducted with a volunteer convenience sample of nine mothers who had been part of the CHAMPSA intervention. Two broad themes emerged: Individual empowerment, including the subthemes parental empowerment, women empowerment, and social support and social leverage; and collective empowerment, including the subthemes informal social control and community organisation, and HIV/AIDS stigma. The findings of the second study contributed to the development of a model showing how improved parent child communication and parental HIV knowledge at the individual level as well as renegotiated, empowered parental identities facilitated through the group process restored parental authority at the individual level as well as collectively, strengthening social capital and restoring the adult and community protective shields. / Theses (Ph.D.)-University of KwaZulu-Natal, Durban, 2011.

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