Immunological aspects of latent tuberculosis infection during pregnancy

Pregnancy-induced immune modulation might lead to reactivation of latent tuberculosis infection (LTBI). This thesis explores aspects of immune-based LTBI diagnostics and how pregnancy affects the immune control of Mycobacterium tuberculosis (Mtb) infection. We studied a prospective cohort of women recruited during pregnancy in Ethiopia. LTBI testing was performed by quantification of interferon-γ (IFN-γ) in Mtb-antigen- stimulated whole blood supernatants using the QuantiFERON-TB Gold Plus (QFT) assay.In paper I, we found that 277/829 (33%) of pregnant women had LTBI using the conventional IFN-γ cut-off level (0.35 IU/ml). However, borderline results (0.20-0.70 IU/ml) were common, especially in HIV-positive women. In paper II, we characterized Mtb-antigen cytokine responses for LTBI classification in women with borderline IFN-γ results. A combination of MCP-2, IP-10 and IL-1ra classified 42% of women with borderline IFN-γ as having high likelihood of LTBI. In paper III, we studied longitudinal patterns of Mtb-triggered IFN-γ secretion during pregnancy and post-partum. We observed that Mtb-stimulated IFN-γ response was elevated during the 3rd trimester compared to early pregnancy and post-partum. In paper IV, we investigated longitudinal kinetics of Mtb-specific and -non-specific cytokine responses in women with LTBI. We found elevated expression of Mtb-specific IL-2 and IP-10, and reduced TGF-β1, secretion at the 3rd trimester. Non-specific levels of IL-2, IP-10 and MCP-2 were elevated post-partum in women with LTBI. In conclusion, these findings suggest that cytokines other than IFN-γ, could be used as biomarkers to assess LTBI status of pregnant women. The dynamic immune responses in women with LTBI indicate increased exposure to Mtb at later stages of pregnancy, which in turn suggests that LTBI is transiently reactivated during pregnancy

How does HIV testing modality impact the cascade of care among persons diagnosed with HIV in Ethiopia?

Background: Despite scaling up of HIV programmes in sub-Saharan Africa, many people living with HIV (PLHIV) are unaware of their HIV status. New testing modalities, such as community-based testing, can improve test uptake, but it is uncertain whether type of testing modality affects the subsequent cascade of HIV care. Objective: To compare linkage to care and antiretroviral treatment (ART) outcomes with regard to type of HIV testing modality. Methods: A retrospective registry-based study was conducted at public ART clinics in an urban uptake area in Central Ethiopia. Persons aged ≥15 years newly diagnosed with HIV in 2015–2018 were eligible for inclusion. Data on patient characteristics and testing modality were analysed for associations with the following outcomes: ART initiation, retention in care at 12 months after starting ART, and viral suppression (<1000 copies/ml, recorded during the first 12 months after ART initiation), using uni- and multivariable analysis. Separate analyses disaggregated by sex were performed. Results: Among 2885 included PLHIV (median age 32 years, 59% female), 2476 (86%) started ART, 1422/2043 (70%) were retained in care, and 953/1046 (92%) achieved viral suppression. Rates of ART initiation were lower among persons diagnosed through community-based testing (adjusted odds ratio [AOR] 0.44, 95% confidence interval [CI] 0.29–0.66) and among persons diagnosed through provider-initiated testing (AOR 0.65, 95% CI 0.44–0.97) compared with facility-based voluntary counselling and testing. In sex-disaggregated analyses, community-based testing was associated with lower rates of ART initiation among both women and men (AOR 0.47, 95% CI 0.27–0.82; AOR 0.39, 95% CI 0.19–0.78, respectively). No differences were found for retention in care or viral suppression with regard to test modality. Conclusion: Type of HIV testing modality was associated with likelihood of ART initiation, but not with subsequent treatment outcomes among persons starting ART

Intrauterine HIV exposure is associated with linear growth restriction among Ethiopian children in the first 18 months of life

Objective: The role of HIV exposure in determining growth among HIV-uninfected children is debated. We determined whether intrauterine HIV exposure influences linear growth in a cohort of Ethiopian children followed up to 18 months of age in public health facilities in Adama city, Ethiopia. Methods: Participants were offspring of pregnant women enrolled in a prospective cohort study that included screening for HIV infection during antenatal care. Growth patterns of HIV-exposed and uninfected (HEU) and HIV-unexposed (HU) children were compared up to 18 months of age, with length-for-age z-score (LAZ) and proportion with stunting as primary outcomes. Multivariable linear and logistic regression models were constructed to investigate the associations between HIV exposure and linear growth, controlling for socio-demographic factors and breastfeeding status. Results: Of 1705 included infants (164 HEU), 1276 remained in follow-up at 18 months. Among HIV-positive mothers, 132 (80.5%) were receiving antiretroviral therapy at enrolment. At the 18-month visit, mean LAZ was −1.08 among HEU children and −0.74 among HU children (p = 0.052). Proportions of HEU and HU children with stunting at the 18-month visit were 27.8% and 18.7%, respectively (p = 0.010). In multivariable models, HIV exposure was associated with lower LAZ at all follow-up visits, and with stunting at the 18-month visit (adjusted odds ratio 2.29, 95% confidence interval 1.40–3.71). HIV exposure was not associated with weight-related growth outcomes. Conclusions: HEU children in Ethiopia had inferior linear growth compared with HU children, implying that intrauterine HIV exposure impacts early childhood growth in this setting

Kynurenine/tryptophan ratio for detection of active tuberculosis in adults with HIV prior to antiretroviral therapy

Objective: The aim of this study was to assess the performance of kynurenine/tryptophan ratio for tuberculosis (TB) case-finding among antiretroviral therapy (ART)-naive people with HIV (PWH), and to investigate other factors associated with kynurenine/tryptophan ratio in this population. Design: A nested case-control study based on a cohort of 812 ambulatory PWH in the Oromia region, Ethiopia. Methods: At enrolment, all participants submitted sputum samples for bacteriological TB investigations. Concentrations of kynurenine and tryptophan in plasma were quantified using liquid chromatography-mass spectrometry. Receiver operator characteristic curves were constructed to assess diagnostic performance (area under the curve; AUC) for kynurenine, tryptophan, and kynurenine/tryptophan ratio. Sensitivity, specificity, and predictive values were calculated. Kynurenine/tryptophan ratios were correlated to plasma levels of nine inflammation mediators, plasma HIV RNA levels, CD4+cell count, BMI, and mid-upper arm circumference (MUAC). Results: We included 124 individuals with HIV-TB coinfection (HIV+/TB+) and 125 with HIV mono-infection (HIV+/TB-). Tryptophan levels were lower in HIV+/TB+ than in HIV+/TB-(median 19.5 vs. 29.8 μmol/l, P < 0.01), while kynurenine levels were similar between these groups (median 2.95 vs. 2.94 μmol/l, P = 0.62). Median kynurenine/tryptophan ratio was 0.15 in HIV+/TB+, significantly higher compared with HIV+/TB-(0.11; P < 0.01), with AUC 0.70 for TB detection. Kynurenine/tryptophan ratio was positively correlated to plasma HIV RNA levels, IP-10, IL-18, and IL-27, and negatively correlated to CD4+cell count, BMI, and MUAC (all P < 0.01). Conclusion: Among ART-naive PWH, kynurenine/tryptophan ratio has modest potential for TB discrimination, limiting its utility for TB case-finding in this population

High variability in tuberculosis treatment outcomes across 15 health facilities in a semi-urban area in central Ethiopia

Background: Despite reported tuberculosis (TB) treatment success rate of 86%, TB remains a leading cause of death in Ethiopia. We investigated patient and provider-specific factors associated with unfavorable treatment outcomes in Ethiopian health facilities providing TB care. Methods: Data on characteristics and treatment outcomes of patients registered for TB treatment at 15 public health facilities (4 hospitals and 11 health centres) were collected from clinic registers. Proportions of unfavorable outcomes (defined as deaths, loss-to-follow-up [LTFU] and treatment failure), were compared across facilities using multivariable logistic regression, with separate analyses for death and LTFU. Results: Among 3359 patients (53.5 % male, median age 28 years, 19.6 % HIV-positive), 296 (8.8 %) had unfavorable treatment outcome. Proportions of unfavorable outcomes across facilities ranged from 2.0 % to 21.1 % (median 8.3 %). Median proportions of death and LTFU among facilities were 3.3 % (range 0–10.9 %) and 2.6 % (range 0.6 %-19.2 %), respectively. Three facilities had significantly higher rates of LTFU, whereas two facilities had higher rates of death. The two facilities with full-time TB-nurses had higher proportions of successful outcomes (95.2 % vs 90.1 %, adjusted odds ratio 2.27, p < 0.0001). Conclusion: Substantial variability of TB treatment outcomes was observed across the assessed health facilities providing TB care, independently of age and HIV co-infection, reflecting possible differences in service structure and related quality of care

Performance of Galectin-9 for Identification of HIV Viremia in Adults Receiving Antiretroviral Therapy in a Resource-Limited Setting

Background: Targeted viral load (VL) testing has been proposed for antiretroviral treatment (ART) monitoring in resource-limited settings. In this study, we have investigated the performance of the host biomarker galectin-9 (Gal-9), alone and in combination with interferon-γ-inducible protein 10 (IP-10), in identifying individuals at increased likelihood of viremia during ART.Setting:Cohort of HIV-positive adults receiving ART at Ethiopian health centers.Methods:We included participants with detectable viremia (VL ≥150 copies/mL) 12 months after starting ART and sex-matched nonviremic controls. Performance to identify individuals with VL ≥1000 copies/mL was determined for Gal-9 and the Gal-9/IP-10 combination, respectively, using receiver operating characteristic (ROC) analysis.Results:Among 191 participants (50.3% women), 46 (24.1%) had VL ≥1000 copies/mL, 23 (12.0%) had 150-999 copies/mL, and 122 (63.9%) had <150 copies/mL. Gal-9 and VL were positively correlated (rs= 0.451, P < 0.001). Sensitivity and specificity for Gal-9 to identify individuals with VL ≥1000 copies/mL were 91.3% (95% CI: 79.2-97.6) and 54.5% (95% CI: 46.0-62.8), respectively. The area under the ROC curve for Gal-9 was 0.810 (95% CI: 0.745-0.875), which was similar to that of the combination of Gal-9 and IP-10 [0.849 (95% CI: 0.792-0.905)]. Assuming 10% prevalence of VL ≥1000 copies/mL, using Gal-9 for targeted VL testing instead of universal VL testing would reduce the number of VL tests from 10 to 5 to identify 1 viremic individual, with misclassification of 1 in 10 viremic individuals.Conclusions:Gal-9 is a potential screening marker for targeted VL monitoring in ART recipients. Further studies are needed to determine optimal threshold levels

Validation of the Viral Load Testing Criteria – an algorithm for targeted viral load testing in HIV-positive adults receiving antiretroviral therapy

Objectives: Restricted capacity for viral load (VL) testing is a major obstacle for antiretroviral therapy (ART) programmes in high-burden regions. Algorithms for targeted VL testing could help allocate laboratory resources rationally. We validated the performance of the Viral Load Testing Criteria (VLTC), an algorithm with satisfactory performance in derivation (sensitivity 91%, specificity 43%). Methods: HIV-positive adults who had been receiving first-line ART for ≥12 months at three Ethiopian public ART clinics were included. Healthcare providers collected data on variables of the VLTC: current CD4 count, mid-upper arm circumference (MUAC) and self-reported treatment interruption. VL testing was performed in parallel. Performance of the algorithm for identification of patients with VL ≥ 1000 copies/ml was evaluated. Results: Of 562 patients (female 62%, median ART duration 92 months), 33 (6%) had VL ≥ 1000 copies/ml. Sensitivity for the VLTC was 85% (95% CI, 68–95), specificity 60% (95% CI, 55–64), positive predictive value 12% (95% CI, 10–14) and negative predictive value 98% (95% CI, 97–99). Use of the algorithm would reduce the number of VL tests required by 57%. Misclassification occurred in 5/33 (15%) of subjects with VL ≥ 1000 copies/ml. Conclusion: In validation, the VLTC performed similarly well as derivation. Use of the VLTC may be considered for targeted VL testing for ART monitoring in high-burden regions

Dynamics of Mycobacterium tuberculosis-Specific and Nonspecific Immune Responses in Women with Tuberculosis Infection during Pregnancy

The immune control of tuberculosis (TB) infection could be influenced by pregnancy. To elucidate this, we longitudinally characterized Mycobacterium tuberculosis (Mtb)-specific and nonspecific immune responses in women during pregnancy and postpartum. HIV-uninfected women without past or current active TB, and with blood samples available from the 1st/2nd trimester, 3rd trimester, and 9 months postpartum, were identified at Ethiopian antenatal care clinics. Twenty-two TB1 women and 10 TB2 women, defined according to Mtb-stimulated interferon-g levels ($0.35 and,0.20 IU/mL, respectively, in the Quantiferon-TB Gold-Plus assay), were included in the study. Longitudinal dynamics of six cytokines (IL-1ra, IL-2, IP-10, MCP-2, MCP-3, and TGF-b1) were analyzed in supernatants from Mtb-stimulated and unstimulated whole blood. In TB1 women, Mtb-specific expression of IL-2 and IP-10 was higher at 3rd compared to 1st/2nd trimester (median 139 pg/mL versus 62 pg/mL, P = 0.006; 4,999 pg/mL versus 2,310 pg/mL, P = 0.031, respectively), whereas level of Mtb-triggered TGF-b1 was lower at 3rd compared to 1st/2nd trimester (26.8 ng/mL versus 2.3 ng/mL, P = 0.020). Unstimulated IL-2, IP-10, and MCP-2 levels were increased postpartum, compared with those noted during pregnancy, in TB1 women. Additionally, postpartum levels of proinflammatory cytokines in unstimulated blood were higher in TB1 women, than in TB2 women. None of the women developed active TB during follow-up. Taken together, dynamic changes of Mtb-specific cytokine expression revealed during the 3rd trimester in TB1 women indicate increased Mtb-antigen stimulation at later stages of pregnancy. This could reflect elevated bacterial activity, albeit without transition to active TB, during pregnancy. IMPORTANCE Tuberculosis (TB) is globally one of the most common causes of death, and a quarter of the world's population is estimated to have TB infection. The risk of active TB is increased in connection to pregnancy, a phenomenon that could be due to physiological immune changes. Here, we studied the effect of pregnancy on immune responses triggered in HIV-uninfected women with TB infection, by analyzing blood samples obtained longitudinally during pregnancy and after childbirth. We found that the dynamics of Mtb-specific and nonspecific immune responses changed during pregnancy, especially in later stages of pregnancy, although none of the women followed in this study developed active TB. This suggests that incipient TB, with elevated bacterial activity, occurs during pregnancy, but progression of infection appears to be counteracted by Mtb-specific immune responses. Thus, this study sheds light on immune control of TB during pregnancy, which could be of importance for future intervention strategies

Longitudinal Mycobacterium tuberculosis-specific Interferon Gamma responses in Ethiopian HIV-negative women during pregnancy and postpartum

Pregnancy may influence cellular immune responses to Mycobacterium tuberculosis. We investigated M. tuberculosis-specific interferon-g responses in women followed longitudinally during pregnancy and postpartum. Interferon-g levels (stimulated by M. tuberculosis antigens [TB1 and TB2] and mitogen included in the QuantiFERON-TB Gold Plus assay) were measured in blood from pregnant HIV-negative women identified from a prospective cohort at Ethiopian antenatal care clinics. Longitudinal comparisons included women without active tuberculosis (TB) with M. tuberculosis-triggered interferon-g responses of $ 0.20 IU/ml, sampled on two and/or three occasions (1st/2nd trimester, 3rd trimester, and 9 months postpartum). Among 2,093 women in the source cohort, 363 met inclusion criteria for longitudinal comparisons of M. tuberculosis-stimulated interferon-g responses. Median M. tuberculosis-triggered interferon-g concentrations were higher at 3rd than those at the 1st/2nd trimester (in 38 women with samples available from these time points; TB1: 2.8 versus 1.6 IU/ml, P = 0.005; TB2: 3.3 versus 2.8 IU/ml, P = 0.03) and postpartum (in 49 women with samples available from these time points; TB1: 3.1 versus 2.2 IU/ml, P = 0.01; TB2: 3.1 versus 2.3 IU/ml, P = 0.03). In contrast, mitogen-stimulated interferon-g levels were lower at 3rd than those at 1st/2nd trimester (in 32 women with samples available from these time points: 21.0 versus 34.9 IU/ml, P = 0.02). Results were similar in 22 women sampled on all 3 occasions. In HIV-negative women, M. tuberculosis-stimulated interferon-g responses were higher during the 3rd trimester than those at earlier stages of pregnancy and postpartum, despite decreased mitogen-triggered responses. These findings suggest increased M. tuberculosis-specific cellular responses due to dynamic changes of latent TB infection during pregnancy

Interferon-g-Inducible Protein 10 (IP-10) Kinetics after Antiretroviral Treatment Initiation in Ethiopian Adults with HIV

Interferon-g-inducible protein 10 (IP-10) has been suggested as a marker for targeted viral load (VL) monitoring during antiretroviral treatment (ART). We aimed to determine the kinetics of IP-10 during the initial year of ART, with particular regard to the impact of tuberculosis (TB) co-infection on IP-10 secretion. Longitudinal plasma IP-10 levels were quantified in 112 treatment-naive HIV-positive adults at Ethiopian health centers, through enzyme-linked immunosorbent assay (ELISA) using samples obtained before and during the initial 12 months of ART. All participants underwent bacteriological TB investigation before starting ART. In virological responders (VRs; defined as VL, 150 copies/ml with no subsequent VL $ 1,000 copies/ml), IP-10 kinetics were analyzed using linear regression models. Among 91/112 (81.3%) participants classified as VRs, 17 (18.7%) had concomitant TB. Median baseline IP-10 was 650 pg/ml (interquartile range [IQR], 428–1,002) in VRs. IP-10 decline was more rapid during the first month of ART (median 306 pg/ml/month) compared with later time intervals (median 7-48 pg/ml/month, P, 0.001 in each comparison). Although VRs with TB had higher IP-10 levels at baseline (median 1106 pg/ml [IQR, 627–1,704]), compared with individuals without TB (median 628 pg/ml [IQR, 391–885]; P = 0.003), the rate of IP-10 decline during ART was similar, regardless of TB-status. During the initial year of ART, IP-10 kinetics followed a biphasic pattern in VRs, with a more rapid decline in the first month of ART compared with later time intervals. Baseline IP-10 was higher in individuals with TB versus individuals without TB, but the kinetics during ART were similar. IMPORTANCE To reach the goal of elimination of HIV as public health threat, access to antiretroviral treatment (ART) has to be further scaled up. To ensure viral suppression in individuals receiving ART, novel and robust systems for treatment monitoring are required. Targeting viral load monitoring to identify individuals at increased likelihood of treatment failure, using screening tools, could be an effective use of limited resources for viral load testing. Interferon-g-inducible protein 10 (IP-10), a host inflammation mediator, has shown potential for this purpose. Here, we have investigated IP-10 kinetics in Ethiopian adults with HIV during the initial year after ART initiation. IP-10 levels decreased in parallel with viral load during ART, and prevalent tuberculosis at ART initiation did not influence IP-10 kinetics. This study shows satisfactory performance for IP-10 as a surrogate marker for viral load in persons starting ART, with no influence of concomitant tuberculosis