Overall focus: Investigating the role of HIV envelope in viral fitness.
|Viral fitness is defined as the ability of Human Immunodeficiency virus to replicate in a given environment.
|The very first viral contact with host cells is mediated by the envelope protein that occurs as spikes on the viral surface. Envelope comprising of gp120 and gp41binds to CD4 and CCR5 receptors on T lymphocytes and undergoes a series of conformational changes that allows the fusion of viral and plasma membranes, culminating in the release of viral RNA into the cytoplasm. The HIV lifecycle thus involves entry, reverse transcription of the viral RNA, integration into the chromosomal DNA, transcription, translation of viral proteins, viral particle formation and budding.This laboratory focuses on the entry process and its impact on the ability of HIV to complete its life cycle efficiently. More specifically, I am interested in elucidating the role and impact of envelope
|function on the abilityof HIV to replicate within a given environment. The two major research thrusts are: 1) identifying Envelope functional determinates that impact HIV fitness and 2) the impact of Envelope N-glycosylation on HIV transmission.
HIV-1 subtype C Envelope functional determinants as targets for drug and vaccine design
Sites within structurally constrained regions of Envelope that affect viral replication are potential targets for drug and vaccine design, especially as they are more unlikely to mutate and evade therapeutics and immune responses. This study investigates individuals that are dual infected with two HIV phylogenetically distinct variants as a model for identifying these sites within Envelope. These dual infected individuals usually have rapid disease progression and it is hypothesised that this is because the two distinct variants can rapidly evolve to gain replication fitness by exchanging regions of env via recombination generating natural chimeric viruses with potential differences in fitness. By identifying sites associated with enhanced fitness, this project will identify determinants essential for viral propagation, prime candidates for drug and vaccine targets. Moreover, this study will also investigate the mechanistic relationship between the function of structurally constrained sites and their impact on viral replication. Given the limited research focus on the structure and function of subtype C Env, this project will advance current knowledge on subtype C infections.
N-glycosylation patterns of gp120 involved in HIV transmission
As vaccines and microbicides are designed to target transmitted variants this study aims to elucidate the mechanism whereby HIV variants are able to cross the genital epithelium and infect CD4 T lymphocytes. In eight out of 10 transmission events, a single HIV infectious unit results in productive infection. However, the presence of sexually transmitted infections is associated with multiple variant transmission suggesting that an intact genital epithelium is highly protective against HIV infection and that variants able to overcome this barrier are selectively transmitted. Transmitted variants are enriched for env sequences with shorter variable loops and fewer N-glycan sites than variants from chronically infected individuals. This suggests that transmission might be dependent on the presence or absence of specific N-glycan sites and that lectins (carbohydrate binding proteins) expressed by the genital mucosal cellular milieu might be involved in HIV infection. Dendritic cells are located at the rectal and genital mucosa and express a lectin (DC-SIGN) that has been shown to bind to gp120 and mediate HIV trans-infection of CD4+ T cells. Therefore, DC-SIGN might selectively bind to variants depending on the presence or absence of specific N-glycan sites on gp120. However, the glycosylation patterns and carbohydrate structures at the N-glycan sites of transmitted variants have not been identified. There is evidence to suggest that N-glycan sites that carry high mannose type carbohydrate structures (bind to DC-SIGN) are conserved compared to those with complex type carbohydrates. This study tests the hypothesis that HIV variants are successfully transmitted because they carry an optimal arrangement of high mannose-type N-glycans that facilitate their uptake by dendritic cells through binding to DC-SIGN (or an as yet unidentified lectin) and enabling their infection of CD4+ T cells.
|I am presently recruiting post graduate students for the above projects. Please contact me at ZL.Woodman@uct.ac.za.
1) Woodman ZL, Chubb AJ, Schwager SLU, van de Merwe L, Ehlers MRW and Sturrock ED. Homologous substitution of ACE C-domain regions with N-domain sequences: effect on processing, shedding, and catalytic properties. Biol Chem. 2006 Aug; 387(8):1043-51.
2) Woodman ZL, Schwager SLU, Ehlers MRW and Sturrock ED. The N domain and the C domain affect ACE shedding differently Biochem J. 2005 Apr 6Aug 1;389(Pt 3):739-44
3) Irina V. Balyasnikova, Zenda L. Woodman, Ronald F. Albrecht II, Ramanathan Natesh, K Ravi Acharya, Edward D. Sturrock and Sergei M. Danilov.The Localization of an N-domain Region of Angiotensin-Converting Enzyme Involved in the Regulation of Ectodomain Shedding using Monoclonal Antibodies J Proteome Res. 2005 Mar-Apr;4(2):258-67
4) Bajaj, BG, Verma SC, Lan K, Cotter MA, Woodman ZL, Robertson ES KSHV encoded LANA upregulates Pim-1 and is a substrate for its kinase activity.Virology. 2006 Jul 20;351(1):18-28.
5) Chopera. D.R., Woodman ZL, Mlotshwa M, Martin D.P., Seoighe C., Treurnicht F., Assis de Rosa D., Hide W., Mlisana K., Abdool Karim S, Gray C.M., Williamson C. Transmission of HIV-1 CTL escape variants provides HLA-mismatched recipients with a survival advantage Plos Pathogens 2007 Mar 21;4(3):e1000033
6) Nobubelo K. Ngandu, Konrad Scheffler, Penny Moore, Darren Martin, Zenda Woodman and Cathal Seoighe Purifying selection affecting synonymous sites reveals functional nucleotide motifs in HIV-1. Virology Journal 2008 5:160
7) F.K. Treurnicht, C. Seoighe, D.P. Martin, N. Wood, M-R. Abrahams, D. Assis de Rosa, H. Bredell, Z. Woodman, W. Hide, K. Mlisana, S Abdool Karim, C.M. Gray, C. Williamson Site specific differences in amino acid frequencies within HIV-1 subtype C proteins expressed during early and chronic infections Virology 2009 in press
8) Zenda Woodman, Koleka Mlisane, Florette Treurnicht , Ruwayida Thebus, Melissa Abrahams, , Abdool Karim and Carolyn Williamson Infection with multiple subtype C variants is associated with sexually transmitted infections. AIDS. 2010 Submitted
Verma, S.C. Lan, K. Woodman, Z.L., and Robertson, E.S., Developments in understanding the mechanism of tumorigenesis mediated by Kaposi’s sarcoma associated herpesvirus. Virus Research Nova Science Publishers, France (2003)
Woodman ZL & Williamson C HIV molecular epidemiology: HIV transmission and adaptation in humans. Curr Opin HIV AIDS. 2009 Jul;4(4):247-52. Review