Micronutrient supplementation and T cell-mediated immune responses in patients with tuberculosis in Tanzania

Targeting Mycobacterium tuberculosis iron-scavenging tools: a recent update on siderophores inhibitors

Among the various bacterial infections, tuberculosis (TB) remains a life-threatening infectious disease responsible as the most significant cause of mortality and morbidity worldwide. The co-infection of human immunodeficiency virus (HIV) in association with TB burdens the healthcare system substantially. Notably, M.tb possesses defence against most antitubercular antibiotic drugs, and the efficacy of existing frontline anti-TB drugs is waning. Also, new and recurring cases of TB from resistant bacteria such as multidrug-resistant TB (MDR), extensively drug-resistant TB (XDR), and totally drug-resistant TB (TDR) strains are increasing. Hence, TB begs the scientific community to explore the new therapeutic class of compounds with their novel mechanism. M.tb requires iron from host cells to sustain, grow, and carry out several biological processes. M.tb has developed strategic methods of acquiring iron from the surrounding environment. In this communication, we discuss an overview of M.tb iron-scavenging tools. Also, we have summarized recently identified MbtA and MbtI inhibitors, which prevent M.tb from scavenging iron. These iron-scavenging tool inhibitors have the potential to be developed as anti-TB agents/drugs.

Macrophage Selenoproteins Restrict Intracellular Replication of Francisella tularensis and Are Essential for Host Immunity

The essential micronutrient Selenium (Se) is co-translationally incorporated as selenocysteine into proteins. Selenoproteins contain one or more selenocysteines and are vital for optimum immunity. Interestingly, many pathogenic bacteria utilize Se for various biological processes suggesting that Se may play a role in bacterial pathogenesis. A previous study had speculated that Francisella tularensis, a facultative intracellular bacterium and the causative agent of tularemia, sequesters Se by upregulating Se-metabolism genes in type II alveolar epithelial cells. Therefore, we investigated the contribution of host vs. pathogen-associated selenoproteins in bacterial disease using F. tularensis as a model organism. We found that F. tularensis was devoid of any Se utilization traits, neither incorporated elemental Se, nor exhibited Se-dependent growth. However, 100% of Se-deficient mice (0.01 ppm Se), which express low levels of selenoproteins, succumbed to F. tularensis-live vaccine strain pulmonary challenge, whereas 50% of mice on Se-supplemented (0.4 ppm Se) and 25% of mice on Se-adequate (0.1 ppm Se) diet succumbed to infection. Median survival time for Se-deficient mice was 8 days post-infection while Se-supplemented and -adequate mice was 11.5 and >14 days post-infection, respectively. Se-deficient macrophages permitted significantly higher intracellular bacterial replication than Se-supplemented macrophages ex vivo, corroborating in vivo observations. Since Francisella replicates in alveolar macrophages during the acute phase of pneumonic infection, we hypothesized that macrophage-specific host selenoproteins may restrict replication and systemic spread of bacteria. F. tularensis infection led to an increased expression of several macrophage selenoproteins, suggesting their key role in limiting bacterial replication. Upon challenge with F. tularensis, mice lacking selenoproteins in macrophages (TrspM) displayed lower survival and increased bacterial burden in the lung and systemic tissues in comparison to WT littermate controls. Furthermore, macrophages from TrspM mice were unable to restrict bacterial replication ex vivo in comparison to macrophages from littermate controls. We herein describe a novel function of host macrophage-specific selenoproteins in restriction of intracellular bacterial replication. These data suggest that host selenoproteins may be considered as novel targets for modulating immune response to control a bacterial infection.

Role of Selenoproteins in Bacterial Pathogenesis

The trace element selenium is an essential micronutrient that plays an important role in maintaining homeostasis of several tissues including the immune system of mammals. The vast majority of the biological functions of selenium are mediated via selenoproteins, proteins which incorporate the selenium-containing amino acid selenocysteine. Several bacterial infections of humans and animals are associated with decreased levels of selenium in the blood and an adjunct therapy with selenium often leads to favorable outcomes. Many pathogenic bacteria are also capable of synthesizing selenocysteine suggesting that selenoproteins may have a role in bacterial physiology. Interestingly, the composition of host microbiota is also regulated by dietary selenium levels. Therefore, bacterial pathogens, microbiome, and host immune cells may be competing for a limited supply of selenium. Elucidating how selenium, in particular selenoproteins, may regulate pathogen virulence, microbiome diversity, and host immune response during a bacterial infection is critical for clinical management of infectious diseases.

Non-antibiotic adjunctive therapy: A promising approach to fight tuberculosis

Tuberculosis (TB) is currently a clinical and public health problem. There is a concern about the emergence and development of multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) species. Additionally, the lack of effective vaccines is another limitation to control the related infections. To overcome these problems various approaches have been pursued such as finding novel drug candidates with a new mechanism of action or repurposing conventional antibiotics. However, these strategies are still far from clinical application. Hence, the use of adjunctive therapy has been suggested for TB. In this paper, we review non-antibiotic adjunctive treatment options for TB. Natural products, vitamins, micronutrients, and trace elementals, as well as non-antibiotic drugs, are examples of agents which have been used as adjunctive therapies. The use of these adjunctive therapies has been shown to improve disease outcomes and reduce the adverse effects of antibiotic drugs. Employing these agents, either alone or in combination with antibiotics, might be considered as a promising approach to control TB infections and achieve better clinical outcomes. However, supportive evidence from randomized controlled trials is still scant and merits further investigations.

Impact of Childhood Malnutrition on Host Defense and Infection

The global impact of childhood malnutrition is staggering. The synergism between malnutrition and infection contributes substantially to childhood morbidity and mortality. Anthropometric indicators of malnutrition are associated with the increased risk and severity of infections caused by many pathogens, including viruses, bacteria, protozoa, and helminths. Since childhood malnutrition commonly involves the inadequate intake of protein and calories, with superimposed micronutrient deficiencies, the causal factors involved in impaired host defense are usually not defined. This review focuses on literature related to impaired host defense and the risk of infection in primary childhood malnutrition. Particular attention is given to longitudinal and prospective cohort human studies and studies of experimental animal models that address causal, mechanistic relationships between malnutrition and host defense. Protein and micronutrient deficiencies impact the hematopoietic and lymphoid organs and compromise both innate and adaptive immune functions. Malnutrition-related changes in intestinal microbiota contribute to growth faltering and dysregulated inflammation and immune function. Although substantial progress has been made in understanding the malnutrition-infection synergism, critical gaps in our understanding remain. We highlight the need for mechanistic studies that can lead to targeted interventions to improve host defense and reduce the morbidity and mortality of infectious diseases in this vulnerable population.

Malnutrition: Modulator of Immune Responses in Tuberculosis

Nutrition plays a major role in the management of both acute and chronic diseases, in terms of body’s response to the pathogenic organism. An array of nutrients like macro- and micro-nutrients, vitamins, etc., are associated with boosting the host’s immune responses against intracellular pathogens including mycobacterium tuberculosis (M.tb). These nutrients have an immunomodulatory effects in controlling the infection and inflammation process and nutritional deficiency of any form, i.e., malnutrition may lead to nutritionally acquired immunodeficiency syndrome, which greatly increases an individual’s susceptibility to progression of infection to disease. This narrative review looks at the various mechanisms by which nutrition or its deficiency leads to impaired cell mediated and humoral immune responses, which in turn affects the ability of an individual to fight M.tb infection or disease. There is very little evidence in the literature that any specific food on its own or a specific quantity can alter the course of TB disease or be effective in the treatment of malnutrition. Further clinical trials or studies will be needed to recommend and to better understand the link between malnutrition, tuberculosis, and impaired immunity.

Nutritional supplements for people being treated for active tuberculosis

BACKGROUND

Tuberculosis and malnutrition are linked in a complex relationship. Tuberculosis may cause undernutrition through increased metabolic demands and decreased intake, and nutritional deficiencies may worsen the disease, or delay recovery by depressing important immune functions. At present, there is no evidence-based nutritional guidance for adults and children being treated for tuberculosis.

OBJECTIVES

To assess the effects of oral nutritional supplements in people being treated with antituberculous drug therapy for active tuberculosis.

SEARCH METHODS

We searched the Cochrane Infectious Disease Group Specialized Register, Cochrane Central Register of Controlled Trials (CENTRAL; Issue 1, 2016), MEDLINE (from 1946 to 4 February 2016), EMBASE (from 1980 to 4 February 2016), LILACS (from 1982 to 4 February 2016), the metaRegister of Controlled Trials (mRCT), the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP), and the Indian Journal of Tuberculosis up to 4 February 2016, and checked the reference lists of all included studies.

SELECTION CRITERIA

Randomized controlled trials that compared any oral nutritional supplement given for at least four weeks with no nutritional intervention, placebo, or dietary advice only for people being treated for active tuberculosis. The primary outcomes of interest were all-cause death, and cure at six and 12 months.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, and extracted data and assessed the risk of bias in the included trials. We presented the results as risk ratios (RR) for dichotomous variables, and mean differences (MD) for continuous variables, with 95% confidence intervals (CIs). Where appropriate, we pooled data from trials with similar interventions and outcomes. We assessed the quality of the evidence using the Grading of Recommendation Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

Thirty-five trials, including 8283 participants, met the inclusion criteria of this review. Macronutrient supplementationSix trials assessed the provision of free food, or high-energy supplements. Only two trials measured total dietary intake, and in both trials the intervention increased calorie consumption compared to controls.The available trials were too small to reliably prove or exclude clinically important benefits on mortality (RR 0.34, 95% CI 0.10 to 1.20; four trials, 567 participants, very low quality evidence), cure (RR 0.91, 95% CI 0.59 to 1.41; one trial, 102 participants, very low quality evidence), or treatment completion (data not pooled; two trials, 365 participants, very low quality evidence).Supplementation probably produces a modest increase in weight gain during treatment for active tuberculosis, although this was not seen consistently across all trials (data not pooled; five trials, 883 participants, moderate quality evidence). Two small studies provide some evidence that quality of life may also be improved but the trials were too small to have much confidence in the result (data not pooled; two trials, 134 participants, low quality evidence). Micronutrient supplementationSix trials assessed multi-micronutrient supplementation in doses up to 10 times the dietary reference intake, and 18 trials assessed single or dual micronutrient supplementation.Routine multi-micronutrient supplementation may have little or no effect on mortality in HIV-negative people with tuberculosis (RR 0.86, 95% CI 0.46 to 1.6; four trials, 1219 participants, low quality evidence), or HIV-positive people who are not taking antiretroviral therapy (RR 0.92, 95% CI 0.69 to 1.23; three trials, 1429 participants, moderate quality evidence). There is insufficient evidence to know if supplementation improves cure (no trials), treatment completion (RR 0.99, 95% CI 0.95 to 1.04; one trial, 302 participants, very low quality evidence), or the proportion of people who remain sputum positive during the first eight weeks (RR 0.92, 95% CI 0.63 to 1.35; two trials, 1020 participants, very low quality evidence). However, supplementation may have little or no effect on weight gain during treatment (data not pooled; five trials, 2940 participants, low quality evidence), and no studies have assessed the effect on quality of life.Plasma levels of vitamin A appear to increase following initiation of tuberculosis treatment regardless of supplementation. In contrast, supplementation probably does improve plasma levels of zinc, vitamin D, vitamin E, and selenium, but this has not been shown to have clinically important benefits. Of note, despite multiple studies of vitamin D supplementation in different doses, statistically significant benefits on sputum conversion have not been demonstrated.

AUTHORS' CONCLUSIONS

There is currently insufficient research to know whether routinely providing free food, or energy supplements improves tuberculosis treatment outcomes, but it probably improves weight gain in some settings.Although blood levels of some vitamins may be low in people starting treatment for active tuberculosis, there is currently no reliable evidence that routinely supplementing above recommended daily amounts has clinical benefits.

A cross-sectional and follow-up study of leukopenia in tuberculosis patients: prevalence, risk factors and impact of anti-tuberculosis treatment

BACKGROUND

To investigate the prevalence of and risk factors for leukopenia in tuberculosis patients and the impact of anti-tuberculosis regimens on the occurrence of leukopenia in newly treated tuberculosis patients.

METHODS

A total of 1,904 tuberculosis patients were included in the study. A cross-sectional survey of the prevalence of leukopenia was initially conducted, and then factors influencing leukopenia were identified using Logistic regression analysis. Non-treatment factors influencing peripheral blood leukocyte counts were analyzed using univariate COX proportional hazards models. Covariate analysis was used to assess the independent effect of different anti-tuberculosis regimens on peripheral blood leukocyte counts.

RESULTS

Being female, advanced age and longer duration of previous anti-tuberculosis treatment (>6 month) were risk factors for leukopenia in tuberculosis patients, while secondary pulmonary tuberculosis, higher body mass index (BMI: 24-27.9 kg/m(2)), and higher degree of education (senior high school or above) were protective factors. Gender, vegetable consumption, drinking, pulmonary infection, other chronic diseases, and use of antibiotics were significantly associated with the development of leukopenia in patients on anti-tuberculosis treatment. In tuberculosis patients treated with anti-tuberculosis regimens not containing antibiotics, peripheral blood leukocyte levels gradually declined with the prolongation of treatment duration. In tuberculosis patients treated with anti-tuberculosis regimens containing antibiotics, peripheral blood leukocyte levels showed a declining trend.

CONCLUSIONS

Female patients, patients at advanced age and recurrent tuberculosis patients having longer previous anti-tuberculosis treatment are high-risk populations for leukopenia. Attention should be paid to the influence of vegetable consumption and drinking, co-morbidities and use of antibiotics during anti-tuberculosis treatment.

Nutritional Supplementation Is a Necessary Complement to Dietary Counseling among Tuberculosis and Tuberculosis-HIV Patients

The Brazilian Ministry of Health and the World Health Organization recommend dietary counseling for patients with malnutrition during tuberculosis treatment. Patients under tuberculosis therapy (infected and not infected with HIV) were followed-up to evaluate the effectiveness of dietary counseling.

OBJECTIVE

describe the nutritional status of patients with tuberculosis.

METHODS

an observational follow-up study over a 180-day period of tuberculosis therapy in adults was conducted. Subjects were assessed for body composition (using BMI, TSF and MUAC parameters), serum biomarkers and offered dietary counseling. The data obtained at each visit (D15, D30, D60, D90, D120, D150, and D180) were analyzed, showing trajectories over time and central tendencies each time.

RESULTS

at baseline, the mean age was 41.1 (± 13.4) years; they were predominantly male, with income lower than a local minimum wage and at least six years of schooling. Patients showed predominantly pulmonary tuberculosis. At baseline, all patients suffered from malnutrition. The overall energy malnutrition prevalence was of 70.6%. Anemia at baseline was observed in both groups (63.2%), however, it was significantly more pronounced in the HIV+. At the end, energy malnutrition was reduced to 57.1% (42.9% of HIV- and 71.4% of the HIV+). Micronutrients malnutrition was evident in 71.4% of the HIV- patients and 85.7% of HIV+ patients at the end of tuberculosis therapy. Using BMI (≤ 18.5 kg/m2cutoff) as an index of malnutrition, it was detected in 23.9% of the HIV- and 27.3% of the HIV+ patients at baseline, with no evident improvement over time; using TSF (≤ 11.4mm as cutoff) or MUAC (≤ 28.5cm as cutoff), malnutrition was detected in 70.1% and 85.3% of all patients, respectively. Nevertheless, combining all biomarkers, at the end of follow-up, all patients suffered from malnutrition.

CONCLUSION

Although with a limited number of patients, the evidence does not support that dietary counseling is effective to recover from malnutrition in our population.

Dietary selenium in adjuvant therapy of viral and bacterial infections

Viral and bacterial infections are often associated with deficiencies in macronutrients and micronutrients, including the essential trace element selenium. In selenium deficiency, benign strains of Coxsackie and influenza viruses can mutate to highly pathogenic strains. Dietary supplementation to provide adequate or supranutritional selenium supply has been proposed to confer health benefits for patients suffering from some viral diseases, most notably with respect to HIV and influenza A virus (IAV) infections. In addition, selenium-containing multimicronutrient supplements improved several clinical and lifestyle variables in patients coinfected with HIV and Mycobacterium tuberculosis. Selenium status may affect the function of cells of both adaptive and innate immunity. Supranutritional selenium promotes proliferation and favors differentiation of naive CD4-positive T lymphocytes toward T helper 1 cells, thus supporting the acute cellular immune response, whereas excessive activation of the immune system and ensuing host tissue damage are counteracted through directing macrophages toward the M2 phenotype. This review provides an up-to-date overview on selenium in infectious diseases caused by viruses (e.g., HIV, IAV, hepatitis C virus, poliovirus, West Nile virus) and bacteria (e.g., M. tuberculosis, Helicobacter pylori). Data from epidemiologic studies and intervention trials, with selenium alone or in combination with other micronutrients, and animal experiments are discussed against the background of dietary selenium requirements to alter immune functions.

Effect of micronutrient supplementation on treatment outcomes in children with intrathoracic tuberculosis: a randomized controlled trial

BACKGROUND

Micronutrients play an important role in immune function. To our knowledge, there have been no comprehensive studies on the role of micronutrient supplementation in children with tuberculosis.

OBJECTIVE

We assessed the effect of micronutrient supplementation in children treated with antituberculosis therapy (ATT).

DESIGN

A randomized, double-blind, placebo-controlled trial that used a 2 × 2 factorial design was undertaken at 2 teaching hospitals in Delhi. Children with newly diagnosed intrathoracic tuberculosis were enrolled, and they received ATT together with daily supplementation for 6 mo with either zinc alone, micronutrients without zinc, micronutrients in combination with zinc, or a placebo. Main outcomes were weight gain and an improvement in a chest X-ray (CXR) lesion assessed at 6 mo of treatment.

RESULTS

A total of 403 children were enrolled and randomly assigned. A microbiological diagnosis of tuberculosis was confirmed in 179 children (44.4%). The median (95% CI) increase in weight-for-age z score at 6 mo was not significantly different between subjects who received micronutrients [0.75 (0.66, 0.84)] and those who did not receive micronutrients [0.76 (0.67, 0.85)] and between subjects who received zinc [0.76 (0.68, 0.85)] and those who did not receive zinc [0.75 (0.66, 0.83)]. An improvement in CXR was observed in 285 children, but there was no difference between those receiving zinc and no zinc or between those receiving micronutrients and no micronutrients after 6 mo of ATT. However, children who received micronutrients had a faster gain in height over 6 mo than did those who did not receive micronutrients (height-for-age z score Δ = 0.08; P = 0.014).

CONCLUSIONS

Micronutrient supplementation did not modify the weight gain or clearance of lesions on CXR in children with intrathoracic tuberculosis. However, micronutrient supplementation during treatment may improve height gain in children with intrathoracic tuberculosis. This trial was registered at clinicaltrials.gov as NCT00801606.