Browsing by Author "Walker, Bruce D."

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Association of TRIM22 with the Type 1 Interferon Response and Viral Control during Primary HIV-1 Infection.
(American Society for Microbiology., 2010) Singh, Ravesh.; Gaiha, Gaurav.; Werner, Lise.; Mlisana, Koleka Patience.; Luban, Jeremy.; Walker, Bruce D.; Abdool Karim, Salim Safurdeen.; Ndung'u, Peter Thumbi.; Brass, Abraham.; McKim, Kevin.
Type 1 interferons (IFNs) induce the expression of the tripartite interaction motif (TRIM) family of E3 ligases, but the contribution of these antiviral factors to HIV pathogenesis is not completely understood. We hypothesized that the increased expression of select type 1 IFN and TRIM isoforms is associated with a significantly lower likelihood of HIV-1 acquisition and viral control during primary HIV-1 infection. We measured IFN-a, IFN-b, myxovirus resistance protein A (MxA), human TRIM5a (huTRIM5a), and TRIM22 mRNA levels in peripheral blood mononuclear cells (PBMCs) of high-risk, HIV-1-uninfected participants and HIV-1-positive study participants. Samples were available for 32 uninfected subjects and 28 infected persons, all within 1 year of infection. HIV-1-positive participants had higher levels of IFN-b(P=0.0005), MxA (P=0.007), and TRIM22 (P=0.01) and lower levels of huTRIM5a (P< 0.001) than did HIV-1-negative participants. TRIM22 but not huTRIM5a correlated positively with type 1 IFN (IFN-a, IFN-b, and MxA) (all P<0.0001). In a multivariate model, increased MxA expression showed a significant positive association with viral load (P=0.0418). Furthermore, TRIM22 but not huTRIM5a, IFN-a, IFN-b, or MxA showed a negative correlation with plasma viral load (P=0.0307) and a positive correlation with CD4 T-cell counts (P=0.0281). In vitro studies revealed that HIV infection induced TRIM22 expression in PBMCs obtained from HIV-negative donors. Stable TRIM22 knockdown resulted in increased HIV-1 particle release and replication in Jurkat reporter cells. Collectively, these data suggest concordance between type 1 IFN and TRIM22 but not huTRIM5a expression in PBMCs and that TRIM22 likely acts as an antiviral effector in vivo.
CD8+ T cell breadth and ex vivo virus inhibition capacity distinguish between viremic controllers with and without protective HLA class I alleles.
(American Society for Microbiology., 2016) Koofhethile, Catherine Kegakilwe.; Ndhlovu, Zaza Mtine.; Thobakgale, Christina Fanesa.; Prado, Julia G.; Ismail, Nasreen.; Mncube, Zenele.; Mkhize, Lungile.; Van der Stok, Mary Elizabeth.; Yende-Zuma, Fortunate Nonhlanhla.; Walker, Bruce D.; Goulder, Philip Jeremy Renshaw.; Ndung'u, Peter Thumbi.
Abstract available in PDF file.
Characterization of CD4+ and CD8+ T cell responses in HIV-1 C-Clade infection.
(2011) Ramduth, Dhanwanthie.; Kiepiela, Photini.; Ndung'u, Peter Thumbi.; Walker, Bruce D.
HIV-1 specific CD4+ T cell activity in clade C infected subjects has not been studied. CD4+ T cells play a vital role in controlling infectious diseases and there is a need to augment our knowledge of HIV immunology to aid vaccine design. We therefore embarked on a study to characterize HIV-1 specific CD4+ T cell activity in both adults and infants; assess the relationship between CD4+ and CD8+ immune responses; and the relationship between CD4+ T cell activity and markers of disease progression (viral loads and CD4 counts). Our study revealed that the magnitude of CD8+ T cell responses correlated significantly with CD4+ T cell responses, but that the percentage of CD8+ T cells directed against HIV-1 was always greater than that of CD4+ T cells. Gag was the frequently targeted HIV-1 protein by CD4+ T cells and had the highest density of epitopes targeted by CD4+ T cells. Patients with either a dominant CD4 or CD8 T cell response against Gag had significantly lower viral loads than patients in whom non-Gag proteins were the main target (p< 0.0001 for CD4 activity and p= 0.007 for CD8 responses). Single IFN- producing CD4+ T cells were present in significantly higher numbers than cells producing both IFN- and IL-2 simultaneously (p=0.009). Gag also dominated the CD4+ T cell response in acutely infected infants with IFN- production detected more frequently than IL-2 or TNF- . Longitudinal analysis of infants receiving early ARV treatment and then ceasing after 12 months revealed that early treatment conferred no protection against increasing viremia and disease progression. CD4+ T cell responses were detected sporadically in untreated infants indicating a dysfunctional immune response in the face of constant exposure to high levels of viremia. Taken together, the data reveal that a vaccine inducing Gag specific CD4+ T cell responses has the potential to confer some degree of protection, but other immunological parameters need to be investigated especially in infants.
Intersubtype differences in the effect of a rare p24 Gag mutation on HIV-1 replicative fitness.
(American Society for Microbiology., 2012) Chopera, Denis Rutendo.; Cotton, Laura A.; Zawaira, Alexander.; Mann, Jaclyn Kelly.; Ngandu, Nobubelo K.; Ntale, Roman.; Carlson, Jonathan M.; Mlisana, Koleka Patience.; Woodman, Zenda.; de Assis Rosa, Debra.; Martin, Eric.; Miura, Toshiyuki.; Pereyra, Florencia.; Walker, Bruce D.; Gray, Clive M.; Martin, Darren Patrick.; Ndung'u, Peter Thumbi.; Brockman, Mark A.; Abdool Karim, Salim Safurdeen.; Brumme, Zabrina L.; Williamson, Carolyn.
Certain immune-driven mutations in HIV-1, such as those arising in p24Gag, decrease viral replicative capacity. However, the intersubtype differences in the replicative consequences of such mutations have not been explored. In HIV-1 subtype B, the p24Gag M250I mutation is a rare variant (0.6%) that is enriched among elite controllers (7.2%) (P 0.0005) and appears to be a rare escape variant selected by HLA-B58 supertype alleles (P<0.01). In contrast, in subtype C, it is a relatively common minor polymorphic variant (10 to 15%) whose appearance is not associated with a particular HLA allele. Using site-directed mutant viruses, we demonstrate that M250I reduces in vitro viral replicative capacity in both subtype B and subtype C sequences. However, whereas in subtype C downstream compensatory mutations at p24Gag codons 252 and 260 reduce the adverse effects of M250I, fitness costs in subtype B appear difficult to restore. Indeed, patient-derived subtype B sequences harboring M250I exhibited in vitro replicative defects, while those from subtype C did not. The structural implications of M250I were predicted by protein modeling to be greater in subtype B versus C, providing a potential explanation for its lower frequency and enhanced replicative defects in subtype B. In addition to accounting for genetic differences between HIV-1 subtypes, the design of cytotoxic-T-lymphocyte-based vaccines may need to account for differential effects of host-driven viral evolution on viral fitness.
Nef-mediated down-regulation of CD4 and HLA class I in HIV-1 subtype C infection: association with disease progression and influence of immune pressure.
(Elsevier., 2014) Mann, Jaclyn Kelly.; Chopera, Denis Rutendo.; Omarjee, Saleha.; Kuang, Xiaomei T.; Le, Anh Q.; Anmole, Gursev.; Danroth, Ryan.; Mwimanzi, Philip.; Reddy, Tarylee.; Carlson, Jonathan M.; Radebe, Mopo.; Goulder, Philip Jeremy Renshaw.; Walker, Bruce D.; Abdool Karim, Salim Safurdeen.; Novitsky, Vladimir.; Williamson, Carolyn.; Brockman, Mark A.; Brumme, Zabrina L.; Ndung'u, Peter Thumbi.
Abstract available in pdf.