Browsing by Author "Mitchell, Charles"
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- ItemThe association between the ratio of monocytes : lymphocytes at age 3 months and risk of tuberculosis (TB) in the first two years of life(BioMed Central, 2014-07-17) Naranbhai, Vivek; Kim, Soyeon; Fletcher, Helen; Cotton, Mark F.; Violari, Avy; Mitchell, Charles; Nachman, Sharon; McSherry, George; McShane, Helen; Hill, Adrian V. S.; Madhi, Shabir A.Background: Recent transcriptomic studies revived a hypothesis suggested by historical studies in rabbits that the ratio of peripheral blood monocytes to lymphocytes (ML) is associated with risk of tuberculosis (TB) disease. Recent data confirmed the hypothesis in cattle and in adults infected with HIV. Methods: We tested this hypothesis in 1,336 infants (540 HIV-infected, 796 HIV-exposed, uninfected (HEU)) prospectively followed in a randomized controlled trial of isoniazid prophylaxis in Southern Africa, the IMPAACT P1041 study. We modeled the relationship between ML ratio at enrollment (91 to 120 days after birth) and TB disease or death in HIV-infected children and latent Mycobacterium tuberculosis (MTB) infection, TB disease or death in HEU children within 96 weeks (with 12 week window) of randomization. Infants were followed-up prospectively and routinely assessed for MTB exposure and outcomes. Cox proportional hazards models allowing for non-linear associations were used; in all cases linear models were the most parsimonious. Results: Increasing ML ratio at baseline was significantly associated with TB disease/death within two years (adjusted hazard ratio (HR) 1.17 per unit increase in ML ratio; 95% confidence interval (CI) 1.01 to 1.34; P = 0.03). Neither monocyte count nor lymphocyte counts alone were associated with TB disease. The association was not statistically dissimilar between HIV infected and HEU children. Baseline ML ratio was associated with composite endpoints of TB disease and death and/or TB infection. It was strongest when restricted to probable and definite TB disease (HR 1.50; 95% CI 1.19 to 1.89; P = 0.006). Therefore, per 0.1 unit increase in the ML ratio at three to four months of age, the hazard of probable or definite TB disease before two years was increased by roughly 4% (95% CI 1.7% to 6.6%). Conclusion: Elevated ML ratio at three- to four-months old is associated with increased hazards of TB disease before two years among children in Southern Africa. While significant, the modest effect size suggests that the ML ratio plays a modest role in predicting TB disease-free survival; its utility may, therefore, be limited to combination with existing tools to stratify TB risk, or to inform underlying pathophysiologic determinants of TB disease.
- ItemLow vitamin-D levels combined with PKP3-SIGIRR-TMEM16J host variants is associated with tuberculosis and death in HIV-infected and -exposed infants(Public Library of Science, 2016) Gupta, Amita; Montepiedra, Grace; Gupte, Akshay; Zeldow, Bret; Jubulis, Jennifer; Detrick, Barbara; Violari, Avy; Madhi, Shabir; Bobat, Raziya; Cotton, Mark; Mitchell, Charles; Spector, Stephen; IMPAACT NWCS113 and P1041 Study TeamBackground: This study examined the associations of 25-hydroxyvitamin D and specific host genetic variants that affect vitamin D levels or its effects on immune function, with the risk of TB or mortality in children. Methods: A case-cohort sample of 466 South African infants enrolled in P1041 trial (NCT00080119) underwent 25-hydroxyvitamin D testing by chemiluminescent immunoassay. Single nucleotide polymorphisms (SNPs) that alter the effect of vitamin D [e.g. vitamin D receptor (VDR)], vitamin D levels [e.g. vitamin D binding protein (VDBP)], or toll like receptor (TLR) expression (SIGIRR including adjacent genes PKP3 and TMEM16J) were identified by real-time PCR. Outcomes were time to TB, and to the composite of TB or death by 192 weeks of follow-up. Effect modification between vitamin D status and SNPs for outcomes was assessed. Findings: Median age at 25-hydroxyvitamin D determination was 8 months; 11% were breastfed, 51% were HIV-infected and 26% had low 25-hydroxyvitamin D (<32ng/mL). By 192 weeks, 138 incident TB cases (43 definite/probable, and 95 possible) and 26 deaths occurred. Adjusting for HIV status and potential confounders, low 25-hydroxyvitamin D was associated with any TB (adjusted hazard ratio [aHR] 1.76, 95% CI 1.01–3.05; p = 0.046) and any TB or death (aHR 1.76, 95% CI 1.03–3.00; p = 0.038). Children with low 25-hydroxyvitamin D and TMEM 16J rs7111432-AA or PKP3 rs10902158-GG were at increased risk for probable/definite TB or death (aHR 8.12 and 4.83, p<0.05) and any TB or death (aHR 4.78 and 3.26, p<0.005) respectively; SNPs in VDBP, VDR, and vitamin D precursor or hydroxylation genes were not. There was significant interaction between low 25-hydroxyvitamin D and, TMEM 16J rs7111432-AA (p = 0.04) and PKP3 rs10902158-GG (p = 0.02) SNPs. Conclusions: Two novel SNPs, thought to be associated with innate immunity, in combination with low vitamin D levels were identified as increasing a young child’s risk of developing TB disease or death. Identifying high-risk children and providing targeted interventions such as vitamin D supplementation may be beneficial.
- ItemA prospective study of the immune reconstitution inflammatory syndrome (IRIS) in HIV-infected children from high prevalence countries(PLoS, 2019-07-01) Cotton, Mark F.; Rabie, Helena; Nemes, Elisa; Mujuru, Hilda; Bobat, Raziya; Njau, Boniface; Violari, Avy; Mave, Vidya; Mitchell, Charles; Oleske, James; Zimmer, Bonnie; Varghese, George; Pahwa, SavitaBackground: The immune reconstitution inflammatory syndrome (IRIS) in HIV-infected infants and young children is relatively understudied in regions endemic for HIV and TB. We aimed to describe incidence, clinical features and risk factors of pediatric IRIS in Sub-Saharan Africa and India. Methods and findings: We conducted an observational multi-centred prospective clinical study from December 2010 to September 2013 in children <72 months of age recruited from public antiretroviral programs. The main diagnostic criterion for IRIS was a new or worsening inflammatory event after initiating antiretroviral therapy (ART). Among 198 participants, median age 1.15 (0.48; 2.21) years, 38 children (18.8%) developed 45 episodes of IRIS. Five participants (13.2%) had two IRIS events and one (2.6%) had 3 events. Main causes of IRIS were BCG (n = 21; 46.7%), tuberculosis (n = 10; 22.2%) and dermatological, (n = 8, 17.8%). Four TB IRIS cases had severe morbidity including 1 fatality. Cytomegalovirus colitis and cryptococcal meningitis IRIS were also severe. BCG IRIS resolved without pharmacological intervention. On multivariate logistic regression, the most important baseline associations with IRIS were high HIV viral load (likelihood ratio [LR] 10.629; p = 0.0011), recruitment at 1 site (Stellenbosch University) (LR 4.01; p = 0.0452) and CD4 depletion (LR 3.4; p = 0.0654). Significantly more non-IRIS infectious and inflammatory events between days 4 and 17 of ART initiation were noted in cases versus controls (35% versus 15.2%: p = 0.0007). Conclusions: IRIS occurs commonly in HIV-infected children initiating ART and occasionally has severe morbidity. The incidence may be underestimated. Predictive, diagnostic and prognostic biomarkers are needed.
- ItemViral hepatitis B and C in HIV-exposed South African infants(BMC (part of Springer Nature), 2020) Tchuem, Cynthia Tamandjou; Cotton, Mark Fredric; Nel, Etienne; Tedder, Richard; Preiser, Wolfgang; Violari, Avy; Bobat, Raziya; Hovind, Laura; Aaron, Lisa; Montepiedra, Grace; Mitchell, Charles; Andersson, Monique IngridBackground: Whilst much attention is given to eliminating HIV mother-to-child transmission (MTCT), little has been done to ensure the same for hepatitis B virus (HBV) transmission. The introduction of HBV immunization at six weeks of age has reduced HBV horizontal transmission in South Africa. However, in order to eliminate HBV MTCT, further interventions are needed. The risk of hepatitis C virus (HCV) MTCT in HIV-infected (HIV+) African women is not yet well described. This study aimed to determine the rate of HBV and HCV vertical transmission in HIV-exposed infants in South Africa. Methods: Serum samples from infants enrolled in an isoniazid prevention study (P1041) were screened for HBV and HCV serology markers; screening was performed on samples collected at approximately 60 weeks of age of the infants. HBV DNA was quantified in HBsAg positive samples and HBV strains characterized through gene sequencing. All HCV antibody samples with inconclusive results underwent molecular testing. Results: Three of 821 infants were positive for both HBsAg and HBV DNA. All HBV strains belonged to HBV subgenotype A1. The rtM204I mutation associated with lamivudine resistance was identified in one infant, a second infant harboured the double A1762T/G1764A BCP mutation. Phylogenetic analysis showed clustering between mother and infant viral genomic sequences. Twenty-one of 821 HIV-exposed infants tested had inconclusive HCV antibody results, none were HCV PCR positive. Conclusions: This study suggests that HBV vertical transmission is likely to be occurring in HIV-exposed infants in South Africa.. A more robust strategy of HBV prevention, including birth dose vaccination, is required to eradicate HBV MTCT. HCV infection was not detected.