Browsing by Author "Gray, Clive M"
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- ItemOpen AccessCD4 and CD8 T-cell responses to acellular pertussis and rotavirus vaccination in breast-fed HIV exposed, uninfected infants(2017) Nundalall, Trishana; Jaspan, Heather B; Gray, Clive MIntroduction: Vaccination is one of the most efficient ways to prevent infectious diseases, however due to the naivety and regulation of immunity found in infants, induction of vaccine-mediated immunity is challenging. Respiratory and diarrheal diseases are major contributors to infant mortality. Additionally, Human Immunodeficiency Virus-1 (HIV) infections increase the risk of mortality. Current advances in Prevention of Mother-to-Child Transmission (PMTCT) have prevented HIV infections in almost 97% of infants being born to HIV-infected mothers. As a result there is an increasing number of HIV exposed, uninfected infants (HEU). HEU infants have a higher rate of infectious disease related mortality and morbidity compared to unexposed infants, the underling causes of these differences are still not understood. In this dissertation, responses to two childhood vaccines, live, attenuated rotaviral vaccine (Rotarix) and acellular Pertussis (aP), were analyzed in HEU infants, with specific focus on T-cell responses to Rotarix and aP, due to the current lack of published data on T-cell responses. Additionally, the influence of feeding mode, that is breast or formula feeding, was also assessed as it is well established that breast fed infants contract fewer infections compared to formula fed infants. Methods: This dissertation included infants from a larger cohort which includes three groups of infants; HIV unexposed breast fed (UBF), HIV exposed breast-fed (EBF) and HIV exposed formula fed (EFF) infants. Infants were recruited at birth and followed up until 36 weeks of age. As no Rotavirus vaccine T-cell assay was previously published, multiple techniques were utilized to attempt to optimize an assay capable of detecting Rotavirus (RV) vaccine-specific T-cell responses. To determine T-cell responses to Bordertella pertussis (BP), blood was collected from infants at each time-point and 200ul was stimulated with BP antigen in a 12-hour whole blood assay. Cells from all assays were fixed and stained for flow cytometric analysis of CD4 and CD8 T-cell responses. The markers used included live/ dead, CD3, CD4 and CD8 for identification of T-cell populations, IFNγ, IL-2 and TNFα cytokines, HLA-DR and Ki67 for activation and proliferation, and CD45RA and CD27 memory differentiation. Data analysis was then completed using Microsoft Excel, Flow.Jo V9, GraphPad prism V6, Pestle 1.7 and Spice V5.33 software packages. Results: Despite multiple attemps it was not possible to optimise an assay capable of consistently detecting Rotavirus vaccine specific responses. This was partly due to interferance from contaminating agents in the protein antigens used, and difficulty in culturing and purification of whole virus. Assessment of aP spcific CD4+ T-cell memory demonstrated an overall increase in terminally differentiated (TD) memory cells accross time. This mirrored the ontogeny of the total T cell pool which showed an overall decrease in naïve T-cell frequencies with a consequent increase in late and terminally differentiated CD4 and CD8 T-cell populations over time through the first months of life. Both total and aP specific CD4+ early differentiated (ED) memory T-cells remained unchanged over time. ED CD8+ memory T-cells peaked at week 15 in EBF infants. A similar observation was found in UBF infants but at a non-significant level. EFF infants had no significant changes in CD8+ naive, ED and late differentiated (LD) memory populations over time. Additionally all infants demonstrated high levels of Ki67 expression at D4-7, which is prior to vaccination and maintained this level of proliferation after vaccination. HEU infants had higher levels of activation compared to HU infants in the first week of life but this normalised to HU infant levels by week 7. Furthermore EFF infants had peak T-cell activation at week 7 as compared to week 15 in EBF infants. In addition HU infants had better cytokine responses than HEU infants at week 7 but similar responses at week 15 and 36. In Addition, EFF infants also had increased vaccine specific CD4+ responses at week 7 and week 36 compared to EBF infants. This was true for overall cytokine expressing CD4 T-cells and single TNFα expressing CD4+ T-cells. Disscussion: Given the important role T-cells play in the clearance of Rotavirus, it is important that an assay capable of detecting RV vaccine specific T-cell responses be developed. Furthermore, T cells play a role in providing help for antibody responses to BP and for killing of intracellular bacteria. Our findings regarding immunity to aP suggest that all infants, regardless of HIV exposure status and feeding mode, are able to mount a T cell response to aP vaccination. However the differing ontogeny of responses seen in all three groups of infants lends some insight on the complex determinants of vaccine T -cell immunogenicity. In this case, age since vaccination, HIV exposure, and feeding mode resulted in apparent changes in vaccine responses as well as T cell differetiation and activation.
- ItemOpen AccessCharacterisation of mucosal tissue in the foreskin after voluntary medical male circumcision(2016) Harryparsad, Rushil; Gray, Clive M; Olivier, Abraham JacobusBackground: Medical Male Circumcision (MMC) reduces the risk of HIV-1 acquisition by up to 60% as shown in a number of randomized controlled trials in Uganda, Kenya and South Africa. MMC has also been shown to reduce the prevalence of other sexually transmitted infections (STIs) like Herpes Simplex Virus (HSV) -2 and Human Papillomavirus (HPV) by 25% and 35% respectively. Asymptomatic STIs may elevate the risk of HIV-1 acquisition by recruiting HIV-1 target cells to the foreskin. The higher permeability of the inner foreskin may play a role in HIV-1 acquisition as well as the number of target cells present in the foreskin. The more inflamed inner foreskin may be increasing the risk of a productive HIV-1 infection. The aims of this dissertation was to a) examine the levels of keratinisation in the inner and outer foreskins after MMC; b) investigate the number of Langerhans, Ki67+ and CD4+ T cells in the inner and outer foreskin and c) identify the impact of asymptomatic STIs on the numbers and proliferative capacity of foreskin-resident Langerhans and CD4+ T cells.
- ItemOpen AccessThe effect of HIV-exposure on immune responses to expanded programme on immunization vaccines and antigens(2013) Kidzeru, Elvis Banboye; Jaspan, Heather B; Gray, Clive MImmunization against vaccine-preventable infections is essential to reducing childhood morbidity and mortality. The immaturity and tolerogenicity of the immune system of infants renders them susceptible to infectious diseases and makes induction of protective immunity via vaccines a challenge. HIV-exposed infants are HIV uninfected and born to HIV-infected mothers and have increased morbidity and mortality of unknown aetiology. We hypothesise that T cells of HIV-exposed uninfected (HEU) infants have impaired proliferative ability and cytokine production in response to vaccine antigens than HIV unexposed (HU) infants.
- ItemOpen AccessEffect of standard tuberculosis treatment on plasma cytokine levels in patients with active pulmonary tuberculosis(Public Library of Science, 2012) Riou, Catherine; Peixoto, Blas Perez; Roberts, Lindi; Ronacher, Katharina; Walzl, Gerhard; Manca, Claudia; Rustomjee, Roxana; Mthiyane, Thuli; Fallows, Dorothy; Gray, Clive MBACKGROUND: Sputum Mycobacterium tuberculosis (Mtb) culture is commonly used to assess response to antibiotic treatment in individuals with pulmonary tuberculosis (TB). Such techniques are constrained by the slow growth rate of Mtb, and more sensitive methods to monitor Mtb clearance are needed. The goal of this study was to evaluate changes in plasma cytokines in patients undergoing treatment for TB as a means of identifying candidate host markers associated with microbiologic response to therapy. METHODS: Twenty-four plasma cytokines/chemokines were measured in 42 individuals diagnosed with active pulmonary TB, 52% were HIV co-infected. Individuals, undergoing a 26-week standard TB treatment, were followed longitudinally over 18 months and measurements were associated with HIV status and rates of sputum culture conversion. RESULTS: Plasma concentrations of interferon-inducible protein-10 (IP-10) and vascular endothelial growth factor (VEGF) were significantly reduced upon TB treatment, regardless of HIV status. By the end of treatment, IP-10 concentrations were significantly lower in HIV negative individuals when compared to HIV-positive individuals (p = 0.02). Moreover, in HIV negative patients, plasma VEGF concentrations, measured as early as 2-weeks post TB treatment initiation, positively correlated with the time of sputum conversion (p = 0.0017). No significant changes were observed in other studied immune mediators. CONCLUSIONS: These data suggest that VEGF plasma concentration, measured during early TB treatment, could represent a surrogate marker to monitor sputum culture conversion in HIV uninfected individuals.
- ItemOpen AccessEstablishing a cohort at high risk of HIV infection in South Africa: challenges and experiences of the CAPRISA 002 acute infection study(Public Library of Science, 2008) van Loggerenberg, Francois; Mlisana, Koleka; Williamson, Carolyn; Auld, Sara C; Morris, Lynn; Gray, Clive M; Karim, Quarraisha Abdool; Grobler, Anneke; Barnabas, Nomampondo; Iriogbe, ItuaObjectives To describe the baseline demographic data, clinical characteristics and HIV-incidence rates of a cohort at high risk for HIV infection in South Africa as well as the challenges experienced in establishing and maintaining the cohort. Methodology/Principle FINDINGS: Between August 2004 and May 2005 a cohort of HIV-uninfected women was established for the CAPRISA 002 Acute Infection Study, a natural history study of HIV-1 subtype C infection. Volunteers were identified through peer-outreach. The cohort was followed monthly to determine HIV infection rates and clinical presentation of early HIV infection. Risk reduction counselling and male and female condoms were provided. After screening 775 individuals, a cohort of 245 uninfected high-risk women was established. HIV-prevalence at screening was 59.6% (95% CI: 55.9% to 62.8%) posing a challenge in accruing HIV-uninfected women. The majority of women (78.8%) were self-identified as sex-workers with a median of 2 clients per day. Most women (95%) reported more than one casual sexual partner in the previous 3 months (excluding clients) and 58.8% reported condom use in their last sexual encounter. Based on laboratory testing, 62.0% had a sexually transmitted infection at baseline. During 390 person-years of follow-up, 28 infections occurred yielding seroincidence rate of 7.2 (95% CI: 4.5 to 9.8) per 100 person-years. Despite the high mobility of this sex worker cohort retention rate after 2 years was 86.1%. High co-morbidity created challenges for ancillary care provision, both in terms of human and financial resources. Conclusions/Significance Challenges experienced were high baseline HIV-prevalence, lower than anticipated HIV-incidence and difficulties retaining participants. Despite challenges, we have successfully accrued this cohort of HIV-uninfected women with favourable retention, enabling us to study the natural history of HIV-1 during acute HIV-infection. Our experiences provide lessons for others establishing similar cohorts, which will be key for advancing the vaccine and prevention research agenda in resource-constrained settings.
- ItemOpen AccessIs obesity a risk factor for vaccine non-responsiveness?(Public Library of Science, 2013) Young, Katherine M; Gray, Clive M; Bekker, Linda-GailUnderstanding the link between vaccine immunogenicity and efficacy is currently a major focus in HIV research. Consequently, recent developments in the HIV-1 vaccine field have led to a closer look at immune responses to known efficacious vaccines. We undertook a study to explore clinical predictors of vaccine efficacy following recombinant hepatitis B (rHBV) vaccination in a cohort of HIV-uninfected, hepatitis B virus naïve women living in a peri-urban setting in Cape Town. Our aim was to define host biological risk factors associated with lack of vaccine uptake. We found a significant association (p=0.009) between body mass index (BMI) and lack of vaccine-specific IgG titre (<10mIU/mL). Obese individuals (BMI ≥ 30kg/m 2 ) were significantly more likely to be non-responders following 2 rHBV vaccine doses (Adjusted Odds Ratio of 8.75; p=0.043). There was no observed association between vaccine responses and age, method of contraception or time from vaccination to antibody measurement. These data suggest that obesity-associated factors interfere with vaccine immunogenicity and possible efficacy.
- ItemOpen AccessA subset of circulating blood mycobacteria-specific CD4 T cells can predict the time to Mycobacterium tuberculosis sputum culture conversion(Public Library of Science, 2014) Riou, Catherine; Gray, Clive M; Lugongolo, Masixole; Gwala, Thabisile; Kiravu, Agano; Deniso, Pamela; Stewart-Isherwood, Lynsey; Omar, Shaheed Vally; Grobusch, Martin P; Coetzee, GerritWe investigated 18 HIV-negative patients with MDR-TB for M. tuberculosis (Mtb)- and PPD-specific CD4 T cell responses and followed them over 6 months of drug therapy. Twelve of these patients were sputum culture (SC) positive and six patients were SC negative upon enrollment. Our aim was to identify a subset of mycobacteria-specific CD4 T cells that would predict time to culture conversion. The total frequency of mycobacteria-specific CD4 T cells at baseline could not distinguish patients showing positive or negative SC. However, a greater proportion of late-differentiated (LD) Mtb- and PPD-specific memory CD4 T cells was found in SC positive patients than in those who were SC negative (p = 0.004 and p = 0.0012, respectively). Similarly, a higher co-expression of HLA-DR + Ki67 + on Mtb- and PPD-specific CD4 T cells could also discriminate between sputum SC positive versus SC negative (p = 0.004 and p = 0.001, respectively). Receiver operating characteristic (ROC) analysis revealed that baseline levels of Ki67 + HLA-DR + Mtb- and PPD-specific CD4 T cells were predictive of the time to sputum culture conversion, with area-under-the-curve of 0.8 (p = 0.027). Upon treatment, there was a significant decline of these Ki67 + HLA-DR + T cell populations in the first 2 months, with a progressive increase in mycobacteria-specific polyfunctional IFNγ + IL2 + TNFα + CD4 T cells over 6 months. Thus, a subset of activated and proliferating mycobacterial-specific CD4 T cells (Ki67 + HLA-DR + ) may provide a valuable marker in peripheral blood that predicts time to sputum culture conversion in TB patients at the start of treatment.