Tuberculosis, Pulmonary Clinical Trial
Official title:
A Randomized, Placebo-Controlled, Double-Blinded, 250-Subject Clinical Trial of Vitamin D Replacement in Patients With Pulmonary Tuberculosis
Tuberculosis is a global public health problem. One third of the world's population is
infected with tuberculosis (TB) with almost 2 million deaths per year globally. According to
the WHO, Pakistan ranks 8th amongst the 22 high TB burden countries, with an estimated
prevalence is 263 cases /100,000 populations.
In spite of effective therapy for drug sensitive TB, treatment failure occurs frequently
leading to concerns for the emergence of multi-drug resistant (MDR) and extensively drug
resistant (XDR) mycobacterial strains. Therefore in the recent years, interest has been
generated regarding the role of adjuvant immunomodulating therapy for the treatment of TB.
WHO has classified tuberculosis by disease severity into 3 distinct categories; mild,
moderate and severe according to clinical presentations and host factors. Severity of
disease has been linked to mycobacterium genotypes and with host factors such as vitamin D
deficiency
Vitamin D is a hormone produced by the body in response to sun exposure. Independent of it's
effects on bone mineralization, vitamin D is recognized to have numerous immune modulating
effects; some specific to mycobacterium tuberculosis. Therefore vitamin D may enhance the
host immune responses against the pathogen. Vitamin D status can be accurately determined by
measuring the serum levels of 25-(OH) D3. A recent systemic review and meta-analysis
explored the association between low serum vitamin D and risk of active tuberculosis and
concluded that patients with tuberculosis have lower serum levels of vitamin D than healthy
controls when matched for sex, age, ethnicity, diet and geographical location.
Vitamin D deficiency is not a life threatening condition. It usually is unrecognized or can
present with generalized 'aches and pains' due to osteomalacia. The recommended dose for
treatment of vitamin D deficiency is 200,000 IU/ month or 50,000 IU/ week, both given for 2
months or until the serum vitamin D level is > 30 ng/ml. Bone mineral density changes are
usually completed by 10 weeks of treatment.
The investigators hypothesize that by replacing vitamin D in patients with active pulmonary
tuberculosis, the 'Time to Recovery' can be shortened.Our aims are to determine whether
replacing patients with insufficient and deficient levels of vitamin D affects the clinical
outcome of the disease.
Tuberculosis Tuberculosis (TB) is a global emergency. In 2004, there were an estimated 8.9
million new cases and 1.7 million deaths due to the disease1. In Pakistan, pulmonary
tuberculosis (TB) is a major public health problem. The population of Pakistan is
160,943,000 with an estimated prevalence of all cases of tuberculosis at 263/100,000, an
incidence of smear positive pulmonary TB of 181/100,000, and a mortality of 34/100,0002.
The management of TB remains a complicated issue even with the availability of effective
anti-tuberculous drugs. One important aspect of this issue has been the difficulty
clinicians' face in measuring clinical response in these patients, especially in
smear-negative pulmonary and extra-pulmonary disease. Christian et al 3. have recently
developed and validated a simple clinical score for the evaluation of TB patients. The score
is based on eleven clinical variables, which were obtained from the WHO clinical manual for
TB. These included self-reported parameters (e.g., cough, hemoptysis, dyspnoea, chest pain
and night sweats), and signs comprising of anemic conjunctivae, tachycardia, positive
findings at lung auscultation, axillary temperature >37.0˚C, body mass index (BMI) and
middle upper arm circumference (MUAC). Each variable contributes 1 point, except for BMI and
MUAC which contribute 2 points each, giving a maximum score of 13. Using this, score
patients can be divided into 3 severity classes, providing an easy tool for clinical follow
up and prognosis.
Vitamin D Vitamin D is normally synthesized in the skin under the influence of sunlight or
ingested, It is readily metabo-lized in the liver to form 25-hydroxyvitamin D (25(OH)D), the
accepted measure of vitamin D status. 25(OH)D is then further metabolized by the 1
hydroxylase enzyme to its biologically active metabolite, 1 , 25 dihy-droxyvitamin D (1
,25[OH]2D) 4,5 . Activated vitamin D circulates with a binding protein and enters the target
cell to interact with its nuclear receptor. This complex then combines with the retinoic
acid X receptor to form a heterodimer, which in turn interacts with the Vitamin D response
element on the target gene. By increasing in-testinal calcium and phosphate absorption6,
increasing renal calcium reabsorption, and enhancing PTH-mediated bone resorption (via its
effect on RANKL), vitamin D has the net effect of increasing the serum cal-cium and
phosphate concentrations. Additionally, the vitamin D receptor element is present on
multiple genes, the vitamin D receptor in many organs, and 1-alpha hydroxylase activity
occurs in extrarenal tissues7. These local tissue effects are responsible for the
non-mineral-related effects of vitamin D; such as cell differentiation and proliferation and
immune regulation8.
Vitamin D deficiency The two most common causes of vitamin D deficiency remains decreased
intake of vitamin D containing food and reduced sun exposure. The major source of vitamin D
is exposure to sunlight, anything that diminishes the transmission or penetration of solar
UVB into the skin will affect the cutaneous synthesis of vitamin D3. Vita-min D deficiency
can therefore occur in people who live without sun exposure (including those whose skin is
constantly protected from the sun by protective clothing, indoor life styles and sunscreen
use.). In addition, very few foods naturally contain vitamin D and foods that are fortified
with with vitamin D are often inadequate to satisfy the vitamin D requirements. Serum levels
of less than 20 ng/mL (50 nmol/L) of 25-OH vitamin D are a commonly accepted cutoff for
vitamin D deficiency , whereas levels between 20 and 30 ng/mL (50 to 75 nmol/L), are
considered insufficiency9,10.
Asymptomatic or minimally symptomatic vitamin D deficiency is increasingly being recognized
around the world. In Pakistan, a number of small studies have identified a high prevalence
of vitamin D deficiency in pa-tient populations that include those presenting with hip
fractures, obstetric cases and those attending ambulatory care clinics. Risk factors include
a history of poor nutrition, lack of exposure to sunlight, and a low socioeco-nomic status.
Zuberi LM et al11 reported that 92% of outpatients presenting to the AKUH, were vitamin D
defi-cient; 62% had severe, 24% moderate and 8% had mild deficiency. Almost half of all
these patients (including those with severe deficiency) were asymptomatic. Two separate
studies from our center involving healthy, as-ymptomatic volunteers have identified a high
prevalence of vitamin D deficiency (unpublished data). Baig MA et al12, in a study on
outpatients from two public hospitals in Karachi, identified that 92% patients were vitamin
D deficient and that the most severe form of D deficiency was seen in patients with
tuberculosis.
Vitamin D Replacement Nutritional deficiency (25OHD <20 ng/ml [50 nmol/L]) requires
treatment with 600,000 IU/month or 50,000 IU/week) 13. In this study we plan to give 600,000
IU/month for 2 months. Repeat testing for vitamin D will be performed at 8 weeks. If the
levels are <30ng/ml then treatment will be repeated for further 2 months.
Vitamin D replacement is generally very safe. Toxicity, with the development of
hypercalciuria and hypercal-cemia occurs only at 25OHD levels above 88 ng/ml (220 nmol/L)
14,15 . In 1997, the National Academy of Sci-ences defined the Safe Upper Limit for vitamin
D as 2000 U/day14 but newer data however indicate that higher doses are safe at least over a
several-month period16.
The benefits of vitamin D replacement occur gradually; in one study, skeletal effects were
seen upto 10 months after a 5 week course of therapy17.
Vitamin D and Tuberculosis Clinical studies suggest that vitamin D enhances
antimycobacterial immunity, and that deficiency is associated with susceptibility to active
disease18,19. High doses of vitamin D were widely used to treat active TB in the
pre-antibiotic era. More recently, case-control studies have demonstrated that a vegetarian
diet (low in vitamin D) is an independent risk factor for active TB in South Asians18 and
that patients with TB who are of Gujarati Hindu ethnic origin have significantly higher
rates of vitamin D deficiency than ethnically matched tuberculin-positive TB contacts.
Similarly, Gibney et al, documented a gradation of vitamin D levels in African immigrants to
Aus-tralia, with patients with latent TB having lower levels as compared to controls, while
patients with active or past history of active TB had levels lower than those with latent
infection20. A recent systematic review and meta-analysis 21explored the association between
low serum vitamin D and risk of active tuberculosis and con-cluded that patients with
tuberculosis have lower serum levels of vitamin D than healthy controls when matched for
sex, age, ethnicity, diet and geographical location.
1 ,25(OH)2D has no direct antimycobacterial action, but it does induce antituberculous
activity in vitro in both monocytes and macrophages22.Several mechanisms of action have been
proposed. Exogenous 1 ,25(OH)2D in-duces a superoxide burst23 and enhances phagolysosome
fusion in Mycobacterium tuberculosis-infected macrophages; both phenomena are mediated by
phosphatidylinositol 3-kinase, suggesting that this response is initiated by binding
membrane vitamin D receptor (VDR) 24.1 ,25(OH)2D also modulates immune responses by binding
nuclear VDR, where it up-regulates protective innate host responses, including induction of
nitric oxide synthase25.Recently, 25(OH)D has also been shown to support messenger RNA
induction of the antimicrobial peptide cathelicidin LL-37, which possesses antituberculous
activity26.
Although the association of vitamin D deficiency and tuberculosis has been documented in
epidemiological and clinical studies, a causal role is yet to be verified. Interestingly
isoniazid and rifampicin therapy has been shown to decrease vitamin D levels, raising the
question of whether low vitamin D levels could be a consequence of disease27. Additionally,
the affect of replacing vitamin D in the prevention and treatment of tuberculosis has not
been studied in a systematic manner. There is, therefore, a need for a randomized controlled
trial to evaluate the effect of vitamin D supplementation on antimycobacterial host response
and clinical recovery.
Immune responses to Mycobacterium tuberculosis Restriction of infection by M. tuberculosis
is dependent on effective macrophage activation which is facilitated by the recruitment of
leucocytes to the site of infection. The protective role of CD4+, IFN-γ producing T cells
has been confirmed in both acute and chronic mycobacterial infections28. Macrophage TNFα
plays a critical role in granuloma formation and in restriction of disease related
pathology29. TNF-α and IFN-γ activate granu-loma formation by C-C family of chemokines,
CCL2, CCL3, CCL4, CCL5 and the C-X-C chemokine family; CXCL8, CXCL9, CXCL10 and CXCL1230 .
Chemokines play a critical role in determining both activation and migration patterns of
circulating monocytes in the blood. CXCL9 is an early predictive marker for IFNγ secreting
cells, and is found to be increased in re-sponse to M. tuberculosis antigen stimulation.
CCL5 and IFNγ-induced CXCL10 also contribute to the granu-lomatous response31.
Previous studies have shown the utility of mycobacterial antigens such as, from RD1 antigens
early secreted and activated T cell (ESAT)6 in investigating specific immune responses in
individuals infected with M. tuber-culosis. Specific immune profiles have been shown to be
present in TB patients which are coordinate with their disease status32,33.
A study of household contacts of TB patients showed that the dynamics of cytokine response
to mycobacterial antigens driven by IL10 was central to protection against, and the
development of M. tuberculosis infection, and that a peak inflammatory cytokine response at
6 months was present in those individuals who did not develop disease34 .
We have shown that circulating CXCL9 levels in TB patients differ according to severity of
disease35. In addi-tion, mycobacterial antigen induced CXCL9 responses correlate with IFNγ,
and that these are greater in local-ised as compared with disseminated disease36. A recent
study has also shown the relevance of using both CCL2 (MCP-2) and CXCL10 (IP-10) as
biomarkers for tuberculosis37,38 . In this study we hope to determine immune parameters in
patients prior to and post-vitamin D treatment.
;
Allocation: Randomized, Endpoint Classification: Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver, Investigator), Primary Purpose: Supportive Care
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