• English
  • Čeština
  • Deutsch
  • Español
  • Français
  • Gàidhlig
  • Latviešu
  • Magyar
  • Nederlands
  • Português
  • Português do Brasil
  • Suomi
  • Svenska
  • Türkçe
  • Қазақ
  • বাংলা
  • हिंदी
  • Ελληνικά
  • Log In
  • Communities & Collections
  • Browse OpenUCT
  • English
  • Čeština
  • Deutsch
  • Español
  • Français
  • Gàidhlig
  • Latviešu
  • Magyar
  • Nederlands
  • Português
  • Português do Brasil
  • Suomi
  • Svenska
  • Türkçe
  • Қазақ
  • বাংলা
  • हिंदी
  • Ελληνικά
  • Log In
  1. Home
  2. Browse by Author

Browsing by Author "Dorfman, Jeffrey"

Now showing 1 - 4 of 4
Results Per Page
Sort Options
  • Loading...
    Thumbnail Image
    Item
    Open Access
    Characterisation of functional properties of Envelopes of highly neutralisation resistant HIV-1 isolates
    (2018) Guled, Fatuma Hassan; Dorfman, Jeffrey; Williamson, Carolyn
    An effective antibody-based HIV-1 vaccine would ideally elicit potent antibodies capable of neutralising a wide range of HIV-1 isolates to better cover the human population. A primary concern is the virus’ ability to rapidly escape an antibody response. A strong neutralising response elicited by a vaccine may, in principle, select for viruses that are highly antibody resistant thereby significantly reducing the benefit of a vaccine. It is therefore important to study and better understand highly neutralisation resistant viruses. To this effect, we characterized sets of subtype C and CRF02_AG viruses whose neutralisation phenotype were well defined using within subtype neutralisation (neutralisation by subtype matched sera). Our main aim was to determine if there exists a relationship between neutralisation resistance and entry efficiency. Very highly neutralisation resistant viruses appear under-represented in the population. We hypothesised that this may be at least partially explained by decreased entry efficiency as changes to Envelope (Env) during escape could affect the entry process and provide opposing selective pressure that discourages the appearance of very highly neutralisation-resistant viruses. By comparing entry efficiencies of tier 3 viruses (highly resistant) to tier 2 (moderately resistant) and 1B (sensitive), we observed that the tier 3 viruses generally exhibited higher entry efficiency. This was the opposed of what we hypothesised at the outset of these experiments. We also measured characteristics of resistant HIV-1 Envs that can be inferred from the primary sequence such as the variable loop lengths, number of glycans and net charge. We found that the V2 net charge and the V5 loop length were associated with neutralisation resistance in subtype C viruses and the V2 loop length was associated with resistance in the CRF02_AG viruses. By analysing glycosylation patterns between the groups, we found that the presence of an N-linked glycan at position 413 and the lack of a glycan at N332 were predictors of neutralisation resistance in subtype C viruses. Tier 3 viruses were also more resistant than tier 2 and 1B viruses to the PGT121 (V3/glycan), 4E10 (MPER) and the CD4 binding site broadly neutralising antibodies VRC01 and 3BNC117; suggesting that the epitopes of these antibodies are important for driving resistance. Furthermore, we found no significant relationship between susceptibility to the entry inhibitors Maraviroc and PSC RANTES (CCR5 antagonists) and the fusion inhibitor T20 and resistance, indicating that neutralisation resistance did not alter inhibitor target sites. Based on our findings, it is clear that reduced entry efficiency does not explain why highly resistant viruses are not more common. We may speculate that the evolutionary steps needed to reach very high neutralisation resistance may be difficult to go through and/or that other countervailing selective pressures may be involved. In the context of an antibody based intervention, highly resistant viruses with increased entry efficiency circulating in the population could be a set back in the control of the HIV-1 epidemic. Therefore, for any long-term antibody-based intervention to be globally relevant it must elicit responses that limit occurrence of resistance and also increase chances that escape would lead to severely impaired viral fitness.
  • Loading...
    Thumbnail Image
    Item
    Open Access
    Evaluating the neutralizing antibody response to HIV-1 membrane proximal external regional; Implications for vaccine design
    (2014) Jacob, Rajesh Abraham; Dorfman, Jeffrey
    Inducing broadly neutralizing antibodies targeting the HIV-1 envelope is thought to be crucial for developing an effective vaccine. The Membrane Proximal External Region (MPER) within the HIV- 1 gp41 envelope is a promising vaccine target. The MPER is highly conserved, functionally constrained, facilitates virus fusion and is targeted by broadly neutralizing monoclonal antibodies. The objectives of this research were 1) To evaluate the neutralization breadth of antibodies induced by epitopes within the MPER compared to the PG9/16-site in chronically HIV-1-infected individuals, 2) to identify neutralization resistant HIV-1 isolates (using plasma samples infected with the same subtype) and to characterize their sensitivity to anti-MPER antibodies and 3) to determine the accessibility of the MPER to HIV-1 induced polyclonal anti-MPER antibodies in a highly neutralization resistant virus (253-11; CRF02_AG subtype).
  • Loading...
    Thumbnail Image
    Item
    Open Access
    Genetic and immunological characterization of new subtype G envelope expressing HIV-1 pseudoviruses
    (2014) Essomba, Rene Ghislain; Dorfman, Jeffrey
    One of the greatest challenges for the development of an effective HIV-1 vaccine is the high genetic diversity of this pathogen and the complex escape mechanisms employed by the envelope gp120 and gp41 glycoprotein that form the envelope spike. An ideal vaccine would elicit the production of broadly neutralizing antibodies (nAb), capable of having potent activity against worldwide viral isolates. This thesis encompasses a series of studies on characterizing the genetic diversity of envelope genes of subtype G and the neutralization antibody responses to these viruses. HIV-1 subtype G accounts for 5% of HIV-1 infection worldwide, centered on West Africa, with spread to European countries, primarily Spain and Portugal, presumably with immigration of infected individuals. Small satellite subtype G epidemics have been documented in Cuba and among Russian intravenous drug users. In addition, 80% of the recombinant strains circulating in Cameroon contain segments attributed to subtype G. However, until recently, little research has been done on the neutralization sensitivity and vulnerabilities of subtype G viruses, particularly those that circulate in its main reservoir, Central and West Africa. We studied plasma derived viruses from eight HIV-1 subtype G infected individuals. Five samples were collected for donation by the Yaoundé Central Hospital Blood Service from individuals who were subsequently found to be HIV-infected. Presumably, these donors were unaware of their HIV status. The remaining three samples were collected at the CIRCB Research Institute in Yaounde during testing for antiretroviral resistance. These donors were failing therapy, and had sufficiently high viral loads that HIV-1 envelope clones could be isolated. The objectives of my thesis were: 1) to examine the molecular and functional characteristics of the HIV-1 envelope glycoproteins of subtype G viral variants which is crucial to improving strategies to prevent transmission; 2) to evaluate the neutralization sensitivity subtype G viruses and the neutralizing capacities of antibodies induced by the viruses by determining the neutralization antibodies titers against autologous and heterologous HIV-1 viral isolates; 3) to characterize the sensitivity of HIV-1 subtype G viral isolates against broadly neutralizing antibodies, to gain insight into the neutralization vulnerabilities of the subtype G viruses.
  • Loading...
    Thumbnail Image
    Item
    Open Access
    The screening of neutralising antibodies against a resistant HIV-1 strain to identify novel epitopes
    (2014) Moyo, Thandeka; Dorfman, Jeffrey
    Since the start of the HIV/AIDS pandemic in the 1980s, over 75 million individuals have been infected with the virus and it has been the cause of approximately 36 million deaths worldwide. With such a high morbidity and mortality in HIV-1 infected individuals, there is a need to find ways of controlling the disease. Development of an HIV-1 vaccine would help in the fight against HIV/AIDS. It is clear that other prevention strategies poorly reach vulnerable groups such as intravenous drug users and people living in war zones. More importantly, they generally provide very transient protection and do not provide the durable and affordable protection that could be expected from a vaccine. Antiretroviral therapy (ART) may be effective in reducing death and morbidity; but, treatment is life-long and ART is not a cure. However, producing immunogens that elicit neutralising antibodies that are protective against HIV-1 acquisition has proven difficult. This is not only because of the genetic diversity of the viruses circulating in the human population but is also as a result of an incomplete understanding of how to design effective immunogens based on the known targets for broadly neutralising antibodies (BnAbs). The availability of more potential targets for BnAbs is also an important goal. In this project, we designed a system to help identify novel targets of BnAbs if one or more does exist. We selected the QH343.A10 virus as the basis for this system. We found this virus to be moderately resistant to sera and resistant to all the BnAbs we initially tested against it (which target various epitopes on the HIV-1 envelope). QH343.A10 is resistant to monoclonal antibodies (mAbs) b12 (anti-CD4-binding site), 2G12 (anti-V3/glycan), 2F5 and 4E10 (both anti-membrane proximal external region). Of note, the virus is resistant to the extremely broad and potent mAb VRC01 (anti-CD4-bs). QH343.A10 was also found to be resistant to neutralisation by soluble CD4 (sCD4). This made the virus attractive to use in our system as antibodies that recognise QH343.A10 in the same manner as these mAbs are also unlikely to neutralise the virus. Therefore, we tested the ability of 474 serum samples, from ART-naïve chronically HIV-1-infected individuals from a Cape Town cohort, to neutralise QH343.A10. Sixty-six sera (14%) were able to neutralise the virus by an ID50 value of 150 or higher and were retained for further analysis. The sera which recognise the MPER, CD4-bs and V3/glycan regions in a similar way to the mAbs that are unable to neutralise QH343.A10 would presumably be similarly unable to neutralise the virus. Thus, just by identifying sera able to neutralise QH343.A10, we propose that we are already partially enriched against sera that recognise these three targets. Because we expected this enrichment to be only partially effective, we then systematically tested for and removed QH343.A10-recoginising sera that recognised the MPER, the V2/glycan-site and V3/glycan region. For technical reasons, we have not yet attempted to remove sera that recognise QH343.A10 through the CD4-binding site and CD4-inducible site (3BC176 mAb site), which are both targets for BnAbs. After exclusion of sera recognising the MPER, V2/glycan-site and V3/glycan region, we were left with 19 samples. We analysed neutralisation breadth and potency of these remaining 19 serum samples as we wanted to retain sera containing potent BnAbs. We remained with 12 sera samples which were broad and potent and did not detectably neutralise QH343.A10 through the MPER, V2/glycan -site or V3/glycan region. In this manner, we believe we have selected heavily for sera that could plausibly neutralise QH343.A10 through the recognition of a novel target of BnAbs. We propose that further study of this very select set of sera taken from a large serum cohort may allow identification of a novel target of broadly neutralising anti-HIV-1 antibodies, if such a target does exist. Our unique system can be used to screen a large panel of serum samples and allows the scientist to focus on those few samples that are broadly neutralising but do not detectably neutralise most of the already identified targets of broadly neutralising anti-HIV-1 antibodies.
UCT Libraries logo

Contact us

Jill Claassen

Manager: Scholarly Communication & Publishing

Email: openuct@uct.ac.za

+27 (0)21 650 1263

  • Open Access @ UCT

    • OpenUCT LibGuide
    • Open Access Policy
    • Open Scholarship at UCT
    • OpenUCT FAQs
  • UCT Publishing Platforms

    • UCT Open Access Journals
    • UCT Open Access Monographs
    • UCT Press Open Access Books
    • Zivahub - Open Data UCT
  • Site Usage

    • Cookie settings
    • Privacy policy
    • End User Agreement
    • Send Feedback

DSpace software copyright © 2002-2025 LYRASIS