M. Kansasii pulmonary disease in idiopathic CD4+ T-lymphocytopenia

Administration of interleukin-7 increases CD4 T cells in idiopathic CD4 lymphocytopenia

Idiopathic CD4 lymphopenia (ICL) is a rare syndrome defined by low CD4 T-cell counts (<300/µL) without evidence of HIV infection or other known cause of immunodeficiency. ICL confers an increased risk of opportunistic infections and has no established treatment. Interleukin-7 (IL-7) is fundamental for thymopoiesis, T-cell homeostasis, and survival of mature T cells, which provides a rationale for its potential use as an immunotherapeutic agent for ICL. We performed an open-label phase 1/2A dose-escalation trial of 3 subcutaneous doses of recombinant human IL-7 (rhIL-7) per week in patients with ICL who were at risk of disease progression. The primary objectives of the study were to assess safety and the immunomodulatory effects of rhIL-7 in ICL patients. Injection site reactions were the most frequently reported adverse events. One patient experienced a hypersensitivity reaction and developed non-neutralizing anti-IL-7 antibodies. Patients with autoimmune diseases that required systemic therapy at screening were excluded from the study; however, 1 participant developed systemic lupus erythematosus while on study and was excluded from further rhIL-7 dosing. Quantitatively, rhIL-7 led to an increase in the number of circulating CD4 and CD8 T cells and tissue-resident CD3 T cells in the gut mucosa and bone marrow. Functionally, these T cells were capable of producing cytokines after mitogenic stimulation. rhIL-7 was well tolerated at biologically active doses and may represent a promising therapeutic intervention in ICL. This trial was registered at www.clinicaltrials.gov as #NCT00839436.

Idiopathic CD4 Lymphocytopenia: Spectrum of opportunistic infections, malignancies, and autoimmune diseases

Idiopathic CD4 lymphocytopenia (ICL) was first defined in 1992 by the US Centers for Disease Control and Prevention (CDC) as the repeated presence of a CD4+ T lymphocyte count of fewer than 300 cells per cubic millimeter or of less than 20% of total T cells with no evidence of human immunodeficiency virus (HIV) infection and no condition that might cause depressed CD4 counts. Most of our knowledge about ICL comes from scattered case reports. The aim of this study was to collect comprehensive data from the previously published cases to understand the characteristics of this rare condition. We searched the PubMed database and Science Direct for case reports since 1989 for Idiopathic CD4 lymphocytopenia cases. We found 258 cases diagnosed with ICL in 143 published papers. We collected data about age, sex, pathogens, site of infections, CD4 count, CD8 count, CD4:CD8 ratio, presence of HIV risk factors, malignancies, autoimmune diseases and whether the patients survived or died. The mean age at diagnosis of first opportunistic infection (or ICL if no opportunistic infection reported) was 40.7 ± 19.2 years (standard deviation), with a range of 1 to 85. One-sixty (62%) patients were males, 91 (35.2%) were females, and 7 (2.7%) patients were not identified whether males or females. Risk factors for HIV were documented in 36 (13.9%) patients. The mean initial CD4 count was 142.6 ± 103.9/mm³ (standard deviation). The mean initial CD8 count was 295 ± 273.6/mm³ (standard deviation). The mean initial CD4:CD8 ratio was 0.6 ± 0.7 (standard deviation). The mean lowest CD4 count was 115.4 ± 87.1/mm³ (standard deviation). The majority of patients 226 (87.6%) had at least one infection. Cryptococcal infections were the most prevalent infections in ICL patients (26.6%), followed by mycobacterial infections (17%), candidal infections (16.2%), and VZV infections (13.1%). Malignancies were reported in 47 (18.1%) patients. Autoimmune diseases were reported in 37 (14.2%) patients.

Pneumonia caused by Mycobacterium kansasii in a series of patients without recognised immune defect

The clinical and epidemiological characteristics of 17 patients diagnosed with Mycobacterium kansasii pneumonia within a limited geographical region over a period of 10 years are described. An in-depth evaluation of the innate and adaptive immune systems was performed for five available patients. A comparison was made of the genetic fingerprint patterns of the isolates obtained by restriction fragment length polymorphism (RFLP) analysis, with the major polymorphic tandem repeat (MPTR) as a probe. Predisposing factors consisted of smoking, airway abnormalities, substance abuse, diabetes or poor general condition, but in two patients no risk factor was identified. In the five patients tested, no abnormalities or deficiencies were detected in the innate or adaptive type-1 immunity. All M. kansasii isolates had identical MPTR RFLP patterns, although no epidemiological connection could be established, and these were identical to those of clinical isolates from Australian patients. These data do not support the theory that defects in the innate or adaptive type-1 immunity have a role in the pathogenesis of invasive M. kansasii infections. The identical fingerprint patterns of the isolates suggested the existence of a virulent strain of M. kansasii.

Epidemiological, clinical, and prognostic differences between the diseases caused by Mycobacterium kansasii and Mycobacterium tuberculosis in patients infected with human immunodeficiency virus: a multicenter study

A multicenter, comparative study was performed to determine the epidemiological, clinical, and prognostic differences between the diseases caused by Mycobacterium tuberculosis and Mycobacterium kansasii in human immunodeficiency virus (HIV)-infected patients. From 1 January 1995 through 31 December 1999, 25 HIV-infected patients received diagnoses of M. kansasii infection, and another 75 were selected as control subjects from among patients who had M. tuberculosis infection. Variables associated with M. tuberculosis disease in the multivariate analysis were previous intravenous drug use (odds ratio [OR], 8; 95% confidence interval [CI], 1.5-41.4) and interstitial radiologic pattern (OR, 12.7; 95% CI, 1.7-94.3). Variables associated with M. kansasii were previous diagnosis of acquired immunodeficiency syndrome (OR, 15.8; 95% CI, 4.2-59.6) and concomitant opportunistic infections (OR, 14.2; 95% CI, 2-105.7). Clinical and radiologic features were similar for both groups, but epidemiological characteristics and prognosis were different. M. kansasii disease was associated more closely with level of immunosuppression and progression of HIV infection than was disease caused by M. tuberculosis.

Nontuberculous Mycobacterial Infections of the Lung

There is an increasing appreciation for the role of nontuberculous mycobacteria (NTM) as pathogens causing pulmonary disease, disseminated disease, or both in immunocompetent and immunocompromised individuals. Species previously considered nonpathogenic have been shown to cause pulmonary infection. The majority of immunocompetent patients with NTM pulmonary infection have underlying lung disease. New diagnostic techniques such as gene probes, gas-liquid and high-pressure chromatography, and polymerase chain reaction offer significant advantages in the rapid identification of NTM species. Some of these techniques allow identification of mycobacteria directly from clinical specimens. The fluoroquinolones, rifabutin, and newer macrolides offer advances in the treatment of infections that are caused by NTM and are resistant to the traditional antimycobacterial drugs.

Drug-induced lymphopenia: focus on CD4+ and CD8+ cells

Drug-induced lymphopenia is a common adverse event. Some drugs, in particular those used in the treatment of malignancies and autoimmune diseases, inevitably affect the percentages and proportions of lymphocytes in the peripheral blood. Some other drugs exert only minor effects and their clinical relevance cannot be established with certainty. Most cytotoxic and immunosuppressive drugs affect CD4+ T cells more profoundly. Since their regeneration seems to be slower than that of CD8+ T cells, the frequent occurrence of CD4+ lymphopenia may merely reflect this phenomenon. As in HIV infection, critically low numbers of CD4+ cells, irrespective of the cause, predisposes to opportunistic infections. There is no such critically low value for CD8+ cells, and their essential role in various pathological conditions should also be established.