Inflammatory markers in pregnancy are associated with postpartum weight in South African women living with HIV on antiretroviral therapy.

BACKGROUND: Postpartum weight (PPW) contributes to long-term obesity, a growing concern in persons with HIV (PWH). We investigated whether inflammatory markers in pregnancy may be involved in postpartum (PP) obesity in PWH. SETTING: A total of 57 pregnant PWH enrolled at ≤14 weeks gestation (T1) in Gugulethu antenatal care clinic in Cape Town and followed through 48 weeks PP were included. METHODS: Plasma soluble (s) CD14, sCD163, leptin, tumour necrosis factor receptor 1 (TNFR-1), resistin, adiponectin, and interleukin-6 (IL-6) were assayed in duplicate using the Luminex platform. We considered each inflammatory marker at T1 (n=57) and T3 (29-36 weeks gestation, n=31) as a separate exposure of interest. Linear mixed effects models were fit to examine whether each exposure was associated with average PPW and PPW trajectories; linear regression was used for associations with PPW change between T1 and 48 weeks. RESULTS: Median age was 32 years (IQR, 29-35), 98% were multigravida, and 49% had a BMI≥30 kg/m2. Higher T1 sCD14 levels were associated with higher average weight through 48 weeks PP (ß = 0.002, p=0.04), and T3 sCD14 with higher PPW gain (ß = 0.007, p=0.04). Leptin (ß = 0.414, p<0.01), TNFR-1 (ß = 11.048, p<0.01) and resistin (ß = 0.714, p=0.01) at T3 were associated with higher average PPW, and IL-6 (ß = 2.266, p=0.02) with PPW gain. CONCLUSION: These findings suggest that low-grade inflammation in pregnancy may play a role in postpartum obesity, pointing to potential mechanisms with implications for long-term cardiometabolic health in PWH.

Comparing the immune abnormalities in MIS-C to healthy children and those with inflammatory disease reveals distinct inflammatory cytokine production and a monofunctional T cell response.

Multisystem inflammatory syndrome in children (MIS-C) is a severe, hyperinflammatory disease that occurs after exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The underlying immune pathology of MIS-C is incompletely understood, with limited data comparing MIS-C to clinically similar paediatric febrile diseases at presentation. SARS-CoV-2-specific T cell responses have not been compared in these groups to assess whether there is a T cell profile unique to MIS-C. In this study, we measured inflammatory cytokine concentration and SARS-CoV-2-specific humoral immunity and T cell responses in children with fever and suspected MIS-C at presentation (n = 83) where MIS-C was ultimately confirmed (n = 58) or another diagnosis was made (n = 25) and healthy children (n = 91). Children with confirmed MIS-C exhibited distinctly elevated serum IL-10, IL-6, and CRP at presentation. No differences were detected in SARS-CoV-2 spike IgG serum concentration, neutralisation capacity, antibody dependant cellular phagocytosis, antibody dependant cellular cytotoxicity or SARS-CoV-2-specific T cell frequency between the groups. Healthy SARS-CoV-2 seropositive children had a higher proportion of polyfunctional SARS-CoV-2-specific CD4+ T cells compared to children with MIS-C and those with other inflammatory or infectious diagnoses, who both presented a largely monofunctional SARS-CoV-2-specific CD4+ T cell profile. Treatment with steroids and/or intravenous immunoglobulins resulted in rapid reduction of inflammatory cytokines but did not affect the SARS-CoV-2-specific IgG or CD4+ T cell responses in MIS-C. In these data, MIS-C had a unique cytokine profile but not a unique SARS-CoV-2 specific humoral or T cell cytokine response.

Myocardial extracellular volume fraction is positively associated with activated monocyte subsets among cART-treated persons living with HIV in South Africa.

BACKGROUND: Despite treatment with combination antiretroviral therapy (cART), persons living with HIV (PLWH) are at higher risk of cardiac structural abnormalities that may presage clinical heart failure, including myocardial fibrosis. This study assessed whether circulating cellular and soluble protein markers of immune activation cross-sectionally associate with myocardial fibrosis among cART-treated PLWH in South Africa. METHODS: Participants were enrolled in Khayelitsha township near Cape Town, SA. Cardiac magnetic resonance imaging was performed. Plasma protein biomarkers were measured using enzyme-linked immunoassays and monocyte phenotypes were evaluated using flow cytometry. Associations were assessed using multivariable linear and logistic regression. RESULTS: Among 69 cART-treated PLWH, mean (SD) age was 48 (10) years, 71% were female, and time since HIV diagnosis was 9 (6) years. Evidence of left ventricular fibrosis by late gadolinium enhancement was present in 74% of participants and mean (SD) extracellular volume fraction (ECV) was 30.9 (5.9)%. Degree of myocardial fibrosis/inflammation measured by ECV was positively associated with percentages of circulating non-classical and intermediate monocyte phenotypes reflecting inflammation and tissue injury. CONCLUSION: These data generate hypotheses on possible immune mechanisms of HIV-associated non-ischemic myocardial disease, specifically among cART-treated PLWH in sub-Saharan Africa, where the majority of the HIV burden exists globally.

Relationship Between LTA4H Promotor Polymorphism and Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome and Its Prevention With Prednisone.

The development of paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) and its prevention using prednisone may potentially be mediated by the LTA4H genotype. We assessed this hypothesis in a clinical trial evaluating prednisone to prevent TB-IRIS. We did not find an association between LTA4H genotype and TB-IRIS incidence or prednisone efficacy.

Mycobacterial-specific secretion of cytokines and chemokines in healthcare workers with apparent resistance to infection with Mycobacterium tuberculosis.

Background: Currently, diagnosis of latent TB infection (LTBI) is based on the secretion of IFN-γ in response to Mycobacterium tuberculosis (Mtb) antigens, the absence of which is regarded as no infection. Some individuals appear to resist Mtb infection despite sustained exposure (resisters). In this study, we aimed to assess cytokines, chemokines and antibodies that may be associated with resistance to Mtb infection. We hypothesized that there may be an alternative immune response to Mtb exposure in the absence of IFN-γ in resisters. Methods: We enrolled HIV-uninfected healthcare workers who had worked in high TB-exposure environments for 5 years or longer. We screened them for LTBI using the tuberculin skin test and the QuantiFERON-TB Gold Plus assay. We performed multiplex Luminex to measure concentrations of T cell-associated cytokines and chemokines as well as total antibodies in plasma collected from unstimulated fresh whole blood and supernatants from QuantiFERON-TB Gold Plus tubes following incubation of whole blood for 16-24 hours with ESAT6/CFP10 peptides. Results: Samples from 78 individuals were analyzed: 33 resisters (TST<10mm; IGRA<0.35 IU/mL), 33 with LTBI (TST≥10mm and IGRA≥0.35 IU/mL) and 12 discordant (TST=0mm; IGRA≥1.0 IU/mL). There were no differences in concentrations of cytokines and chemokines in plasma between the different groups. Resisters had significantly lower concentrations of IFN-γ, IL-2, TNF-α, MIP-1α, MIP-1ß, ITAC, IL-13 and GM-CSF in supernatants compared with LTBI group. There were no significant differences in the concentrations in supernatants of IL-10, IL-1ß, IL-17A, IL-21, IL-23, MIP-3α, IL-4, IL-5, IL-6, IL-7, IL-8, Fractalkine and IL-12p70 between the groups. We observed that resisters had similar concentrations of total antibodies (IgG1, IgG2, IgG3, IgG4, IgA, and IgM) in plasma and supernatants compared to the LTBI and discordant groups. Conclusion: Resistance to Mtb infection despite sustained exposure is associated with lower Mtb-specific secretion of Th1-associated cytokines and chemokines. However, resisters showed secreted concentrations after Mtb stimulation of total antibodies and cytokines/chemokines associated with innate and Th17 immune responses similar to those with Mtb infection. This suggests an ability to mount non-IFN-γ immune responses to Mtb in apparent resisters.

Phenotypic Profile of Mycobacterium tuberculosis-Specific CD4 T-Cell Responses in People With Advanced Human Immunodeficiency Virus Who Develop Tuberculosis-Associated Immune Reconstitution Inflammatory Syndrome.

Background: Tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is a frequent complication of cotreatment for TB and human immunodeficiency virus (HIV)-1. We characterized Mycobacterium tuberculosis (Mtb)-specific CD4 T-cell phenotype and transcription factor profile associated with the development of TB-IRIS. Methods: We examined the role of CD4 T-cell transcription factors in a murine model of mycobacterial IRIS. In humans, we used a longitudinal study design to compare the magnitude of antiretroviral therapy, activation, transcription factor profile, and cytotoxic potential of Mtb-specific CD4 T cells between TB-IRIS (n = 25) and appropriate non-IRIS control patients (n = 18) using flow cytometry. Results: In the murine model, CD4 T-cell expression of Eomesodermin (Eomes), but not Tbet, was associated with experimentally induced IRIS. In patients, TB-IRIS onset was associated with the expansion of Mtb-specific IFNγ+CD4 T cells (P = .039). Patients with TB-IRIS had higher HLA-DR expression (P = .016), but no differences in the expression of T-bet or Eomes were observed. At TB-IRIS onset, Eomes+Tbet+Mtb-specific IFNγ+CD4+ T cells showed higher expression of granzyme B in patients with TB-IRIS (P = .026). Conclusions: Although the murine model of Mycobacterium avium complex-IRIS suggests that Eomes+CD4 T cells underly IRIS, TB-IRIS was not associated with Eomes expression in patients. Mycobacterium tuberculosis-specific IFNγ+CD4 T-cell responses in TB-IRIS patients are differentiated, highly activated, and potentially cytotoxic.

Rifampicin resistance and mortality in patients hospitalised with HIV-associated tuberculosis.

Background: Patients with HIV and drug-resistant tuberculosis (TB) are at high risk of death. Objectives: We investigated the association between rifampicin-resistant TB (RR-TB) and mortality in a cohort of patients who were admitted to hospital at the time of TB diagnosis. Method: Adults hospitalised at Khayelitsha Hospital and diagnosed with HIV-associated TB during admission, were enrolled between 2013 and 2016. Clinical, biochemical and microbiological data were prospectively collected and participants were followed up for 12 weeks. Results: Participants with microbiologically confirmed TB (n = 482) were enrolled a median of two days (interquartile range [IQR]: 1-3 days) following admission. Fifty-three participants (11.0%) had RR-TB. Participants with rifampicin-susceptible TB (RS-TB) received appropriate treatment a median of one day (IQR: 1-2 days) following enrolment compared to three days (IQR: 1-9 days) in participants with RR-TB. Eight participants with RS-TB (1.9%) and six participants with RR-TB (11.3%) died prior to the initiation of appropriate treatment. Mortality at 12 weeks was 87/429 (20.3%) in the RS-TB group and 21/53 (39.6%) in the RR-TB group. RR-TB was a significant predictor of 12-week mortality (hazard ratio: 1.88; 95% confidence interval: 1.07-3.29; P = 0.03). Conclusion: Mortality at 12 weeks in participants with RR-TB was high compared to participants with RS-TB. Delays in the initiation of appropriate treatment and poorer regimen efficacy are proposed as contributors to higher mortality in hospitalised patients with HIV and RR-TB.

Influenza Vaccination Uptake and Hesitancy among Healthcare Workers in Early 2021 at the Start of the COVID-19 Vaccine Rollout in Cape Town, South Africa.

Vaccination attitudes among healthcare workers (HCWs) predict their level of vaccination uptake and intention to recommend vaccinations to their patients. To our knowledge, no study has been conducted in South Africa to assess hesitancy toward influenza vaccines among HCWs. We adapted a questionnaire developed and validated by Betsch and colleagues and used it to conduct online and face-to-face interviews among HCWs at the start of the COVID-19 vaccine rollout. Multivariate logistic regression was used to assess predictors of influenza vaccine hesitancy. Of 401 participants, 64.5% were women, 49.2% were nurses, and 12.5% were physicians. A total of 54.9% were willing to accept, 20.4% were undecided, and 24.7% intended to refuse influenza vaccination. Participants who were above 25 years of age and physicians were more likely to accept the vaccine. Key predictors of vaccine acceptance were confidence in the effectiveness, consideration of benefits and risks, and willingness to be vaccinated to protect others. Influenza vaccine hesitancy was highest in those who did not trust that influenza vaccines are safe. For future flu seasons, tailored education programs on the safety and effectiveness of flu vaccines targeting younger HCWs, could be vital to improving vaccine uptake.

Xpert Ultra testing of blood in severe HIV-associated tuberculosis to detect and measure Mycobacterium tuberculosis blood stream infection: a diagnostic and disease biomarker cohort study.

BACKGROUND: Mycobacterium tuberculosis bloodstream infection is a leading cause of death in people living with HIV and disseminated bacillary load might be a key driver of disease severity. We aimed to assess Xpert MTB/RIF Ultra (Xpert Ultra) testing of blood as a diagnostic for M tuberculosis bloodstream infection and investigate cycle threshold as a quantitative disease biomarker. METHODS: In this cohort study, we obtained biobanked blood samples from a large and well characterised cohort of adult patients admitted to hospital in Western Cape, South Africa with suspected HIV-associated tuberculosis and a CD4 count less than 350 cells per µL. Patients already receiving antituberculosis therapy were excluded. Samples were obtained on recruitment within 72 h of admission to hospital, and patients were followed up for 12 weeks to determine survival. We tested the biobanked blood samples using the Xpert Ultra platform after lysis and wash processing of the blood. We assessed diagnostic yield (proportion of cases detected, with unavailable test results coded as negative) against a microbiological reference, both as a function of markers of critical-illness and compared with other rapid diagnostics (urine lipoarabinomannan and sputum Xpert). Quantitative blood Xpert Ultra results were evaluated as a disease biomarker by assessing association with disease phenotype defined by principal component analysis of 32 host-response markers. Prognostic value compared to other tuberculosis biomarkers was assessed using likelihood ratio testing of nested models predicting 12-week mortality. FINDINGS: Between Jan 16, 2014, and Oct 19, 2016, of the 659 participants recruited to the parent study, 582 had an available biobanked blood sample. 447 (77%) of 582 met the microbiological reference standard for tuberculosis diagnosis. Median CD4 count was 62 (IQR 221-33) cells per µL, and 123 (21%) of participants died by 12-weeks follow-up. Blood Xpert Ultra was positive in 165 (37%) of 447 participants with confirmed tuberculosis by the microbiological reference standard, with a diagnostic yield of 0·37 (95% CI 0·32-0·42). Diagnostic yield increased with lower CD4 count or haemoglobin, and outperformed urine lipoarabinomannan testing in participants with elevated venous lactate. Quantitative blood Xpert Ultra results were more closely associated with mortality than other tuberculosis biomarkers including blood culture, and urine lipoarabinomannan, or urine Xpert (all p<0·05). A principal component of clinical phenotype capturing markers of inflammation, tissue damage, and organ dysfunction was strongly associated with both blood Xpert-Ultra positivity (associated with a SD increase of 1·1 in PC score, p<0·0001) and cycle threshold (r= -0·5; p<0·0001). INTERPRETATION: Xpert Ultra testing of pre-processed blood could be used as a rapid diagnostic test in critically ill patients with suspected HIV-associated tuberculosis, while also giving additional prognostic information compared with other available markers. A dose-response relationship between quantitative blood Xpert Ultra results, host-response phenotype, and mortality risk adds to evidence that suggests M tuberculosis bloodstream infection bacillary load is causally related to outcomes. FUNDING: Wellcome Trust, National Institute of Health Fogarty International Center, South African MRC, UK National Institute of Health Research, National Research Foundation of South Africa. TRANSLATIONS: For the Xhosa and Afrikaans translations of the abstract see Supplementary Materials section.

Serial measurement of M. tuberculosis in blood from critically-ill patients with HIV-associated tuberculosis.

BACKGROUND: Despite being highly prevalent in hospitalised patients with severe HIV-associated tuberculosis (TB) and sepsis, little is known about the mycobacteriology of Mycobacterium tuberculosis bloodstream infection (MTBBSI). We developed methods to serially measure bacillary load in blood and used these to characterise MTBBSI response to anti-TB therapy (ATT) and relationship with mortality. METHODS: We established a microscopy method for direct visualisation of M. tuberculosis bacilli in blood using a novel lysis-concentration protocol and the fluorescent probe, 4-N,N-dimethylaminonaphthalimide-trehalose (DMN-Tre). We tested blood using GeneXpert® MTB/RIF-Ultra (Xpert-ultra) and Myco/F lytic culture after processing blood through lysis-wash steps to remove PCR inhibitors and anti-microbial drug carry-over. HIV-positive patients predicted to have MTBBSI gave blood samples 0, 4, 24, 48 and 72 h after ATT initiation. Bacillary loads were quantified using microscopy, Xpert-ultra cycle threshold, and culture time-to-positivity. Pharmacodynamics were modelled using these measures combined on an ordinal scale, including association with 12-week mortality. FINDINGS: M. tuberculosis was detected in 27 of 28 recruited participants; 25 (89%) by blood Xpert-ultra, 22 (79%) by DMN-Tre microscopy, and 21 (75%) by Myco/F lytic blood culture. Eight (29%) participants died by 12-week follow-up. In a combined pharmacodynamic model, predicted probabilities of negative DMN-Tre microscopy, blood Xpert-ultra, or blood culture after 72 h treatment were 0·64, 0·27, and 0·94, respectively, in those who survived, compared with 0·23, 0·06, and 0·71 in those who died (posterior probability of slower clearance of MTBBSI in those that died >0·99). DMN-Tre microscopy of blood demonstrated heterogenous bacillary morphologies, including microcolonies and clumps. Bacillary cell-length varied significantly with ATT exposure (mean cell-length increase 0·13 log-µm/day; 95%CrI 0·10-0·16). INTERPRETATION: Pharmacodynamics of MTBBSI treatment can be captured using DMN-Tre microscopy, blood Xpert-ultra and culture. This could facilitate interventional trials in severe HIV-associated TB. FUNDING: Wellcome Trust, NIH Fogarty International Center, South African MRC, NIHR(UK), National Research Foundation of South Africa.

COVID-19 vaccine acceptance and hesitancy among healthcare workers in South Africa.

BACKGROUND: We assessed willingness to accept vaccination against coronavirus disease 2019 (COVID-19) among healthcare workers(HCWs) at the start of South Africa's vaccination roll-out. RESEARCH DESIGN AND METHODS: We conducted a cross-sectional survey among HCWs in Cape Town in March-May 2021 and assessed predictors of vaccination intentions. RESULTS: We recruited 395 participants; 64% women, 49% nurses, and 13% physicians. Of these, 233(59.0%) would accept and 163 (41.0%) were vaccine hesitant i.e. would either refuse or were unsure whether they would accept COVID-19 vaccination. People who did not trust that COVID-19 vaccines are effective were the most hesitant (p = 0.038). Older participants and physicians were more likely to accept vaccination than younger participants (p < 0.01) and other HCWs (p = 0.042) respectively. Other predictors of vaccine acceptance were trust that vaccines are compatible with religion (p < 0.001), consideration of benefits and risks of vaccination (p < 0.001), willingness to be vaccinated to protect others (p < 0.001), and viewing vaccination as a collective action for COVID-19 control (p = 0.029). CONCLUSIONS: COVID-19 vaccine hesitancy is high among HCWs in Cape Town. Reducing this would require trust-building interventions, including tailored education.

Pharmacokinetics of antitubercular drugs in patients hospitalized with HIV-associated tuberculosis: a population modeling analysis.

BACKGROUND: Early mortality among hospitalized HIV-associated tuberculosis (TB/HIV) patients is high despite treatment. The pharmacokinetics of rifampicin, isoniazid, and pyrazinamide were investigated in hospitalized TB/HIV patients and a cohort of outpatients with TB (with or without HIV) to determine whether drug exposures differed between groups. METHODS: Standard first-line TB treatment was given daily as per national guidelines, which consisted of oral 4-drug fixed-dose combination tablets containing 150 mg rifampicin, 75 mg isoniazid, 400 mg pyrazinamide, and 275 mg ethambutol. Plasma samples were drawn on the 3rd day of treatment over eight hours post-dose. Rifampicin, isoniazid, and pyrazinamide in plasma were quantified and NONMEM ® was used to analyze the data. RESULTS: Data from 60 hospitalized patients (11 of whom died within 12 weeks of starting treatment) and 48 outpatients were available. Median (range) weight and age were 56 (35 - 88) kg, and 37 (19 - 77) years, respectively. Bioavailability and clearance of the three drugs were similar between TB/HIV hospitalized and TB outpatients. However, rifampicin's absorption was slower in hospitalized patients than in outpatients; mean absorption time was 49.9% and 154% more in hospitalized survivors and hospitalized deaths, respectively, than in outpatients. Higher levels of conjugated bilirubin correlated with lower rifampicin clearance. Isoniazid's clearance estimates were 25.5 L/h for fast metabolizers and 9.76 L/h for slow metabolizers. Pyrazinamide's clearance was more variable among hospitalized patients. The variability in clearance among patients  was 1.70 and 3.56 times more for hospitalized survivors and hospitalized deaths, respectively, than outpatients.   Conclusion. We showed that the pharmacokinetics of first-line TB drugs are not substantially different between hospitalized TB/HIV patients and TB (with or without HIV) outpatients. Hospitalized patients do not seem to be underexposed compared to their outpatient counterparts.

Fractional dose compared with standard dose inactivated poliovirus vaccine in children: a systematic review and meta-analysis.

BACKGROUND: Since WHO recommended introduction of at least a single dose of inactivated poliovirus vaccine (IPV) in routine immunisation schedules, there have been global IPV shortages. Fractional-dose IPV (fIPV) administration is one of the strategies to ensure IPV availability. We reviewed studies comparing the effects of fractional with full-dose IPV vaccination to determine when seroconversion proportions with each strategy become similar in children aged 5 years and younger. METHOD: In this systematic review and meta-analysis, we searched 16 databases in July, 2019, for trials and observational studies, including ongoing studies that compare immunogenicity and adverse events of fractional-dose (0·1 mL) to full-dose (0·5 mL) IPV in healthy children aged 5 years or younger regardless of study design, number of doses, and route of administration. Screening, selection of articles, data extraction, and risk of bias assessment were done in duplicate, and conflicts were resolved by discussion or arbitration by a third author. We assessed immunogenicity, the main outcome, as proportion of seroconverted participants and changes in geometric mean titres of anti-poliovirus antibodies. Timepoints were eligible for analysis if measurements were done at least 4 weeks after vaccination. Summary estimates were pooled by use of random-effects meta-analysis. Analysis was stratified by study design, type of outcome measure, type of poliovirus, and number of doses given. We assessed heterogeneity using the χ2 test of homogeneity and quantified it using the I2 statistic. We assessed risk of bias using the Cochrane risk of bias tool, and the certainty of evidence using the Grading of Recommendations Assessment, Development and Evaluation approach. The study is registered with PROSPERO, CRD42018092647. FINDINGS: 860 records were screened for eligibility, of which 36 potentially eligible full-text articles were assessed and 14 articles were included in the final analysis: two ongoing trials and 12 articles reporting on ten completed studies. For poliovirus type 2, there were no significant differences in the proportions of seroconversions between fractional and full doses of IPV for two or three doses: the risk ratio for serconversion at one dose was 0·61 (95% CI 0·51-0·72), at two doses was 0·90 (0·82-1·00), and at three doses was 0·95 (0·91-1·00). Geometric mean titres (GMTs) for poliovirus type 2 were lower for fIPV than for full-dose IPV: -0·51 (95% CI -0·87 to -0·14) at one dose, -0·49 (-0·70 to -0·28) at two doses, and -0·98 (-1·46 to -0·51) at three doses. The seroconversion meta-analysis for the three-dose comparison was homogeneous (p=0·45; I2=0%), whereas heterogeneity was observed in the two-dose (p<0·00001; I2=88%) and one-dose (p=0·0004; I2=74%) comparisons. Heterogeneity was observed in meta-analyses of GMTs for one-dose (p<0·00001; I2=92%), two-dose (p=0·002; I2=80%), and three-dose (p<0·00001; I2=93%) comparisons. Findings for types 1 and 3 were similar to those for type 2. The certainty of the evidence was high for the three-dose comparisons and moderate for the rest of the comparisons. INTERPRETATION: There is no substantial difference in seroconversion between three doses of fIPV and three doses of full-dose IPV, although the full dose gives higher titres of antibodies for poliovirus type 1, 2, and 3. Use of fractional IPV instead of the full dose can stretch supplies and possibly lower the cost of vaccination. FUNDING: South African Medical Research Council and the National Research Foundation of South Africa.

Functional and Activation Profiles of Mucosal-Associated Invariant T Cells in Patients With Tuberculosis and HIV in a High Endemic Setting.

Background: MAIT cells are non-classically restricted T lymphocytes that recognize and rapidly respond to microbial metabolites or cytokines and have the capacity to kill bacteria-infected cells. Circulating MAIT cell numbers generally decrease in patients with active TB and HIV infection, but findings regarding functional changes differ. Methods: We conducted a cross-sectional study on the effect of HIV, TB, and HIV-associated TB (HIV-TB) on MAIT cell frequencies, activation and functional profile in a high TB endemic setting in South Africa. Blood was collected from (i) healthy controls (HC, n = 26), 24 of whom had LTBI, (ii) individuals with active TB (aTB, n = 36), (iii) individuals with HIV infection (HIV, n = 50), 37 of whom had LTBI, and (iv) individuals with HIV-associated TB (HIV-TB, n = 26). All TB participants were newly diagnosed and sampled before treatment, additional samples were also collected from 18 participants in the aTB group after 10 weeks of TB treatment. Peripheral blood mononuclear cells (PBMC) stimulated with BCG-expressing GFP (BCG-GFP) and heat-killed (HK) Mycobacterium tuberculosis (M.tb) were analyzed using flow cytometry. MAIT cells were defined as CD3+ CD161+ Vα7.2+ T cells. Results: Circulating MAIT cell frequencies were depleted in individuals with HIV infection (p = 0.009). MAIT cells showed reduced CD107a expression in aTB (p = 0.006), and reduced IFNγ expression in aTB (p < 0.001) and in HIV-TB (p < 0.001) in response to BCG-GFP stimulation. This functional impairment was coupled with a significant increase in activation (defined by HLA-DR expression) in resting MAIT cells from HIV (p < 0.001), aTB (p = 0.019), and HIV-TB (p = 0.005) patients, and higher HLA-DR expression in MAIT cells expressing IFNγ in aTB (p = 0.009) and HIV-TB (p = 0.002) after stimulation with BCG-GFP and HK-M.tb. After 10 weeks of TB treatment, there was reversion in the observed functional impairment in total MAIT cells, with increases in CD107a (p = 0.020) and IFNγ (p = 0.010) expression. Conclusions: Frequencies and functional profile of MAIT cells in response to mycobacterial stimulation are significantly decreased in HIV infected persons, active TB and HIV-associated TB, with a concomitant increase in MAIT cell activation. These alterations may reduce the capacity of MAIT cells to play a protective role in the immune response to these two pathogens.

Mucosal-associated invariant T cells in natural immunity and vaccination against infectious diseases in humans.

Mucosal-associated invariant T (MAIT) cells are subsets of T cells abundant in human mucosal tissues and in blood. These cells are activated directly by cytokines or by vitamin B metabolites antigen presentation. MAIT cells possess antimicrobial potential against viruses and bacteria through production of cytokines and cytotoxic molecules. MAIT cells generally reduce in numbers and function during viral and bacterial infections/diseases. Mice and humans lacking MAIT cells cannot effectively control bacterial infections. MAIT cells respond rapidly to infections and are rapidly recruited to the site of vaccination or infection including the lungs where they can be involved in controlling local inflammation. These characteristics of MAIT cells offer them a unique potential to be explored as potential targets for vaccines.

A pilot study of inflammatory mediators in brain extracellular fluid in paediatric TBM.

Tuberculous meningitis (TBM) is the most fatal form of tuberculosis and frequently occurs in children. The inflammatory process initiates secondary brain injury processes that lead to death and disability. Much remains unknown about this cerebral inflammatory process, largely because of the difficulty in studying the brain. To date, studies have typically examined samples from sites distal to the site of disease, such as spinal cerebrospinal fluid (CSF) and blood. In this pilot study, we examined the feasibility of using direct brain microdialysis (MD) to detect inflammatory mediators in brain extracellular fluid (ECF) in TBM. MD was used to help guide neurocritical care in 7 comatose children with TBM by monitoring brain chemistry for up to 4 days. Remnant ECF fluid was stored for offline analysis. Samples of ventricular CSF, lumbar CSF and blood were collected at clinically indicated procedures for comparison. Inflammatory mediators were quantified using multiplex technology. All inflammatory markers, with the exception of interleukin (IL)-10 and IL-12p40, were detected in the ECF. Cytokine concentrations were generally lower in ECF than ventricular CSF in time-linked specimens. Individual cases showed ECF cytokine increases coinciding with marked increases in ECF glycerol or decreases in ECF glucose. Cytokine levels and glycerol were generally higher in patients with more severe disease. This is the first report of inflammatory marker analysis from samples derived directly from the brain and in high temporal resolution, demonstrating feasibility of cerebral MD to explore disease progression and possibly therapy response in TBM.

Antibody tests for diagnosing COVID-19: how relevant are they?

The current standards for detecting active coronavirus disease (COVID-19) infection are molecular tests by reverse transcription polymerase chain reaction, using swabs from the lower or upper respiratory tract. Because of the expertise required and the long turnaround time for the availability of test results, faster and easier point-of-care methods are necessary. The latter may include the detection of antibodies specific to COVID-19. We highlight a recent Cochrane review that assessed the accuracy of antibody tests for diagnosing COVID-19. The review shows that, at present, antibodies have little use in the diagnosis of COVID-19 within the first seven days from onset of symptoms. However, as time progresses, the sensitivity of the antibody tests increases. Antibody tests are more useful in detecting previous COVID-19 infection if used 15 days or more from onset of symptoms. Data presented in the review should be interpreted with caution as most studies (85%) recruited in-hospital patients and 11% recruited suspected COVID-19 patients, while only 4% recruited convalescent patients. This limits generalisability of the results to most settings.