Consensus?

• Treat active TB after renal transplantation with the same therapy as general population (Evidence level B)

• If rifampin is used, monitor blood levels of calcineurin inhibitors and rapamycin. Use rifabutin as an alternative (Evidence level C)

Risk factors for Post-TxTB

• DM

• Chronic liver disease

• Cyclosporine therapy

Case series

• Mycobacterial infection in 1261 renal transplant pts

• 27pts (2.1%) developed infection (20 had M. Tb)

• Mean age 40 years old with mean time of immunosuppression=26 months

• Immunosuppression was continued in all cases and doses were adjusted according to levels

• TB dissemination rates – 1% in general population vs 35% in post Tx pts.

• No difference with cyclosporine vs “conventional therapy”. However, risk is higher with the use of OKT3 (anti-CD3 monoclonal antibody)

• From another study, TAC or MMF were associated with development of TB earlier and in younger patients

Vitamin D: A New Old Cure for TB?

Alexander Usorov, MD

9-18-07

Overview

• Is TB that big of a deal?

• What do the observational studies show?

• What are the mechanisms of action?

TB – a big deal?

• Global emergency

• M. Tb. Kiils a human being every 15 seconds

• 8.8 million new cases in 2003

• 1.7 million deaths

• 1/3 of World’s population is infected with M. tubecrulosis

• Leading cause of death in women of reproductive age and HIV pts

• In the US, 10-15 milllion ppl are infected

• Leading cause of death in AIDS pts

• Higher prevalence of XDR TB in AIDS pts

Observations

• 1903 – Niels Ryberg Finsen wins Nobel prize for demonstrating that UV light treats pts with lupus vulgaris (cutaneous form of TB)

• 1905 – Robert Koch wins Nobel prize for isolating tubercle bacilli (which he did in 1882)

• 1854 – Hermann Brehmer opens first ever sanatorium (himself suffered from TB)

• 1887 – Edward Livingston Trudeau opens first sanatorium in the United States (Saranac Lake, NY) after observing that rabbits infected with TB had a more severe course if kept indoors in the dark.

Selman Waksman discovered Streptomyces griseus. Streptomycin was used successfully in 1944, which led to Nobel Prize in 1952

1946 –pts with lupus vulgaris were treated with Vitamin D2 and 18 out of 32 were cured (Dowling et al in Lancet 1947: 919-922)

Celiac Disease and TB

• Pts with celiac disease were found to have higher risk of TB, HR 3.74 (Ludvigsson et al. Thorax 2007;62:23-28)

• Follow up to a study by Williams et al (Susceptibility to TB in patients with celiac disease. Tubercle 1988;69:267-74) where positive relationship was established and showed a sixfold increase in death from Tb among CD patients.

• Swedish registery compared 14,335 pts with celiac disease to 69,888 mached individuals in a general population

• Impressive ability to collect medical data as a result of Swedish National In-Patient Register

• Only 24 pts in CD group developed TB, compared with 35 pts in general cohort

• Most likely due to malabsorption and lack of Vitamin D in pts with CD

Vitamin D and TB immunity

• A single dose of Vit D enhances immunity to Mycobacteria ( Martineau et al. Am J Respir Crit Care Med 176;208-213, 2007)

• Double-blind RCT in 192 healthy adult TB contacts in London– Single oral dose of 2.5mg Vit D vs placebo– Measured response to BCG-lux (measures the ability of whole blood to restrict

the growth of recombinant reporter mycobacteria in vitro)– Single dose of Vit D significantly enhances TB pts’ antimycobacterial immunity in

vitro– Profound Vit D deficiency in 40% of cohort; independently associated with South

Asian and African-Americans ( may be the effect of increased skin pigmentation in reducing cutaneous Vit D synthesis)

Vitamin D supplementation and sputum conversion

• Indonesian study in 2006• Double-blind RCT, Vit D vs placebo (in addition to RIPE)

in 67 pts with active pulmonary TB• Rate of sputum conversion as follows

– Vit D 100% Placebo 76% (p=0.002)

• More subjects with radiologic improvement in Vit D group

How does it all work?

• 1986-1987 Rook and Crowle infected human monocytes and macrophages with M. Tb. and added 1,25D3, which triggered significant antimicrobial activity

• Subsequently, Toll-like receptors were discovered.• TLRs are pattern-recognition receptors whose activation

induces expression of antimicrobial peptides • 11 subtypes of TLRs are expressed on various types of

immune and non-immune cells• TLRs trigger direct antimicrobial activity against

intracellular bacteria as well as apoptosis, cytokine secretion, and so on

• TLR2-TLR1, TLR4 and 5, TLR2-6 respond to ligands of bacterial origin

• TLR3, TLR 7, and TLR 8 respond to ligands of viral origin (targets of imiquimod and resisquimod for txt of genital warts and herpes)

• TLR 9 – to both• TLR4 – possible role against fungal

organisms

Human TLRs and their ligands. TLR 2 heterodimerizes with TLR1 and TLR6 to recognize triacyl- and diacyl-lipopeptides. TLR4 and TLR5 ligands are LPS and flagellin, respectively. These TLRs are supposed to recognize products derived from bacteria. By contrast, TLR3 recognizes viral dsRNA, whereas TLR8 recognizes viral ssRNA. TLR9 recognizes DNA from both bacteria and viruses. TLR7 and TLR10 have no known natural ligand; however, TLR7 can be stimulated by synthetic compounds such as imiquimod. TLR signaling is mediated via two different adapters, MyD88 and TRIF, which lead to activation of NF-κB and IRF3, respectively. MyD88 interacts directly with TLR5, TLR7, TLR8 and TLR9. TLR2–TLR1, TLR2–TLR6 and TLR4 associate with MyD88 through TIRAP; it is unclear how MyD88 associates with TLR10. TRIF directly associates with TLR3, but requires TRAM to interact with TLR4.

Upregulation of macrophage 1α,25(OH)2D synthesis following administration of pharmacologic doses of vitamin D in active Mycobacterium tuberculosis infection. In the granuloma both IFNγ and ligation of macrophage TLR2/1 by M. tuberculosis induces macrophage expression of 25(OH)D-1α-hydroxylase. Administration of pharmacologic doses of vitamin D results in increased circulating concentrations of free 25(OH)D, which is metabolised by upregulated 1α-hydroxylase to 1α,25(OH)2D. This may either act in a paracrine manner to modulate immune responses in the granuloma, or, if produced at high concentration, may enter the systemic circulation and induce hypercalcemia.

• DEFENSINs– Antimicrobial peptides produced by activation of TLR– 3 major classes : alfa-defensins, beta-defensins,

cathelicidins

• Alfa – predominantly in neutrophil granules• Beta – epithelial cells of airways and intestines• Cathelicidins – almost everywhere

Human TLR2–TLR1-induced antimicrobial mechanism against intracellular mycobacteria. TLR2–TLR1 stimulation results in the upregulation of the expression of Cyp27B1 and of VDR. Cyp27B1 converts inactive vitamin D (25D3) into its active form (1,25D3). The intracellular pool of 25D3 is shuttled into the cell via the vitamin D binding protein (DBP). Once activated, 1,25D3 can then bind to and activate the VDR, and induce transcription of antimicrobial factors, including the antimicrobial peptide cathelicidin (Cath.). The cathelicidin peptide can then traffic into intracellular compartments harboring mycobacteria. Whether or not cathelicidin has a role in the TLR-induced antimicrobial activity is still unclear. However, the cathelicidin peptide has been demonstrated to kill Mycobacterium tuberculosis directly. Therefore, cathelicidin probably has an important role in the TLR2–TLR1-mediated antimicrobial activity, but is probably not the only effector. The induction of host-defense mechanisms by TLR2–TLR1 depends on the amount of 25D3 present in the serum. Abbreviation: RIP, rest in peace.

Vitamin D and Transplantation

• Possible role of Vit D in immune tolerance, when its deficiency causes failure of tolerance mechanisms leading to autoreactive cytotoxic T-cell activation

• Several reports of acceleration of allograft rejection and induction of autoimmune diseases in transplant pts with

low levels of Vit D • Nonhypercalcemic Vit D receptor agonist BXL-628 (as

well as calcitriol) inhibits, as a monotherapy, acute and chronic graft rejection in mouse models. (Transplantation 80:81-87)