A Composite Recombinant Salivary Proteins Biomarker for Phlebotomus argentipes Provides a Surveillance Tool Postelimination of Visceral Leishmaniasis in India.

Incidence of visceral leishmaniasis (VL) in the Indian subcontinent (ISC) has declined by more than 95% since initiation of the elimination program in 2005. As the ISC transitions to the postelimination surveillance phase, an accurate measurement of human-vector contact is needed to assure long-term success. To develop this tool, we identified PagSP02 and PagSP06 from saliva of Phlebotomus argentipes, the vector of Leishmania donovani in the ISC, as immunodominant proteins in humans. We also established the absence of cross-reactivity with Phlebotomus papatasi saliva, the only other human-biting sand fly in the ISC. Importantly, by combining recombinant rPagSP02 and rPagSP06 we achieved greater antibody recognition and specificity than single salivary proteins. The receiver operating characteristics curve for rPagSP02 + rPagSP06 predicts exposure to Ph. argentipes bites with 90% specificity and 87% sensitivity compared to negative control sera (P >.0001). Overall, rPagSP02 + rPagSP06 provides an effective surveillance tool for monitoring vector control efforts after VL elimination.

The human immune response to saliva of Phlebotomus alexandri, the vector of visceral leishmaniasis in Iraq, and its relationship to sand fly exposure and infection.

BACKGROUND: Sand fly saliva exposure plays an important role in immunity against leishmaniasis where it has mostly been associated with protection. Phlebotomus (Ph.) alexandri transmits Leishmania (L.) infantum, the causative agent of visceral leishmaniasis (VL), in Iraq. Our group recently demonstrated that 20% of Operation Iraqi Freedom (OIF) deployers had asymptomatic VL (AVL) indicative of prior infection by the parasite L. infantum. Little is known about Ph. alexandri saliva, and the human immune response to it has never been investigated. Here, we characterize the humoral and cellular immune response to vector saliva in OIF deployers naturally exposed to bites of Ph. alexandri and characterize their immunological profiles in association to AVL. METHODOLOGY/PRINCIPAL FINDINGS: The humoral response to Ph. alexandri salivary gland homogenate (SGH) showed that 64% of 200 OIF deployers developed an antibody response. To assess the cellular immune response to saliva, we selected a subcohort of subjects based on their post-travel (median 4 months; range 1-22 months) antibody response (SGH Antibody [Ab] positive or negative) as well as their AVL status; ten never-traveled controls were also included. Banked peripheral blood mononuclear cells (PBMC), collected ~10 years after end of deployment, were stimulated with SGH for 96 hours. The levels of IFN- γ, IL-6, IL-10, IL-13 and IL-17 were determined by ELISA. Our findings indicate that OIF deployers mounted a cellular response to SGH where the anti-SGH+ asymptomatic subjects developed the highest cytokine levels. Further, stimulation with SGH produced a mixture of pro-inflammatory and anti-inflammatory cytokines. Contrary to our hypothesis, we observed no correlation between the cellular immune response to Ph. alexandri SGH and prevention from asymptomatic infection with L. infantum. CONCLUSIONS/SIGNIFICANCE: As we found, although all infected deployers demonstrated persistent disease control years after deployment, this did not correlate with anti-saliva systemic cellular response. More exposure to this vector may facilitate transmission of the L. infantum parasite. Since exposure to saliva of Ph. alexandri may alter the human immune response to bites of this vector, this parameter should be taken into consideration when considering the VL risk.

Leishmaniasis in the United States: Emerging Issues in a Region of Low Endemicity.

Leishmaniasis, a chronic and persistent intracellular protozoal infection caused by many different species within the genus Leishmania, is an unfamiliar disease to most North American providers. Clinical presentations may include asymptomatic and symptomatic visceral leishmaniasis (so-called Kala-azar), as well as cutaneous or mucosal disease. Although cutaneous leishmaniasis (caused by Leishmania mexicana in the United States) is endemic in some southwest states, other causes for concern include reactivation of imported visceral leishmaniasis remotely in time from the initial infection, and the possible long-term complications of chronic inflammation from asymptomatic infection. Climate change, the identification of competent vectors and reservoirs, a highly mobile populace, significant population groups with proven exposure history, HIV, and widespread use of immunosuppressive medications and organ transplant all create the potential for increased frequency of leishmaniasis in the U.S. Together, these factors could contribute to leishmaniasis emerging as a health threat in the U.S., including the possibility of sustained autochthonous spread of newly introduced visceral disease. We summarize recent data examining the epidemiology and major risk factors for acquisition of cutaneous and visceral leishmaniasis, with a special focus on implications for the United States, as well as discuss key emerging issues affecting the management of visceral leishmaniasis.

Immunogenicity of a Live-Attenuated Dengue Vaccine Using a Heterologous Prime-Boost Strategy in a Phase 1 Randomized Clinical Trial.

BACKGROUND: Dengue is a global health problem and the development of a tetravalent dengue vaccine with durable protection is a high priority. A heterologous prime-boost strategy has the advantage of eliciting immune responses through different mechanisms and therefore may be superior to homologous prime-boost strategies for generating durable tetravalent immunity. METHODS: In this phase 1 first-in-human heterologous prime-boost study, 80 volunteers were assigned to 4 groups and received a tetravalent dengue virus (DENV-1-4) purified inactivated vaccine (TDENV-PIV) with alum adjuvant and a tetravalent dengue virus (DENV-1-4) live attenuated vaccine (TDENV-LAV) in different orders and dosing schedules (28 or 180 days apart). RESULTS: All vaccination regimens had acceptable safety profiles and there were no vaccine-related serious adverse events. TDEN-PIV followed by TDEN-LAV induced higher neutralizing antibody titers and a higher rate of tetravalent seroconversions compared to TDEN-LAV followed by TDEN-PIV. Both TDEN-PIV followed by TDEN-LAV groups demonstrated 100% tetravalent seroconversion 28 days following the booster dose, which was maintained for most of these subjects through the day 180 measurement. CONCLUSIONS: A heterologous prime-boost vaccination strategy for dengue merits additional evaluation for safety, immunogenicity, and potential for clinical benefit. CLINICAL TRIALS REGISTRATION: NCT02239614.

Association of BCG Vaccination in Childhood With Subsequent Cancer Diagnoses: A 60-Year Follow-up of a Clinical Trial.

Importance: The BCG vaccine is currently the only approved tuberculosis vaccine and is widely administered worldwide, usually during infancy. Previous studies found increased rates of lymphoma and leukemia in BCG-vaccinated populations. Objective: To determine whether BCG vaccination was associated with cancer rates in a secondary analysis of a BCG vaccine trial. Design, Setting, and Participants: Retrospective review (60-year follow-up) of a clinical trial in which participants were assigned to the vaccine group by systematic stratification by school district, age, and sex, then randomized by alternation. The original study was conducted at 9 sites in 5 US states between December 1935 and December 1998. Participants were 2963 American Indian and Alaska Native schoolchildren younger than 20 years with no evidence of previous tuberculosis infection. Statistical analysis was conducted between August 2018 and July 2019. Interventions: Single intradermal injection of either BCG vaccine or saline placebo. Main Outcomes and Measures: The primary outcome was diagnosis of cancer after BCG vaccination. Data on participant interval health and risk factors, including smoking, tuberculosis infection, isoniazid use, and other basic demographic information, were also collected. Results: A total of 2963 participants, including 1540 in the BCG vaccine group and 1423 in the placebo group, remained after exclusions. Vaccination occurred at a median (interquartile range) age of 8 (5-11) years; 805 participants (52%) in the BCG group and 710 (50%) in the placebo group were female. At the time of follow-up, 97 participants (7%) in the placebo group and 106 participants (7%) in the BCG vaccine group could not be located; total mortality was 633 participants (44%) in the placebo group and 632 participants (41%) in the BCG group. The overall rate of cancer diagnosis was not significantly different in BCG vaccine vs placebo recipients (hazard ratio, 0.82; 95% CI, 0.66-1.02), including for lymphoma and leukemia. The rate of lung cancer was significantly lower in BCG vs placebo recipients (18.2 vs 45.4 cases per 100 000 person-years; hazard ratio, 0.38; 95% CI, 0.20-0.74; P = .005), controlling for sex, region, alcohol overuse, smoking, and tuberculosis. Conclusions and Relevance: Childhood BCG vaccination was associated with a lower risk of lung cancer development in American Indian and Alaska Native populations. This finding has potentially important health implications given the high mortality rate associated with lung cancer and the availability of low-cost BCG vaccines.

Cutaneous Leishmaniasis: Updates in Diagnosis and Management.

Cutaneous leishmaniasis (CL) is a diverse human disease caused by more than 20 Leishmania species transmitted by the bite of an infected sand fly. Diagnostic testing is recommended to confirm infection and determine the infecting species. Treatment decisions are complex and providers should consider infecting species, patient comorbidities, extent and location of lesions, and previous treatments. There is no single universal treatment for CL and some treatment can have toxicity. Treatment should be individualized and factors, such as self-healing nature of this infection, risk of metastatic complications (ie, mucosal leishmaniasis), and patient wishes, need to be included in individual risk-benefit treatment decisions.

Asymptomatic Visceral Leishmania infantum Infection in US Soldiers Deployed to Iraq.

BACKGROUND: Visceral leishmaniasis (VL), due to Leishmania infantum, is a persistent intracellular parasitic infection transmitted by the bite of infected sand flies. Symptomatic VL has been reported in U.S. soldiers with Iraq deployment. Untreated symptomatic VL can be fatal; asymptomatic VL (AVL) may establish a lifelong risk of reactivation. We report prevalence and AVL risk factors in Operation Iraqi Freedom (OIF) deployers during 2002-11. METHODS: Healthy soldiers exposed to VL endemic areas in Iraq and 50 controls who never traveled to endemic regions were recruited through military healthcare facilities (2015-17). Responses to a risk factor survey and blood samples were obtained. Leishmania research diagnostics utilized included enzyme-linked immunosorbent assay (ELISA), rk39 test strips, quantitative polymerase chain reaction (PCR), and interferon gamma release (IGRA) assays. Statistical analyses included Fisher exact test, Pearson χ2 test, Mann-Whitney U test, and logistic regression. RESULTS: 200 deployed subjects were enrolled, mostly males (84.0%), of white ethnicity (79.0%), and median age 41 (range 24-61) years. 64% were seropositive for Phlebotomus alexandri saliva antibodies. Prevalence of AVL (any positive test result) was 39/200 (19.5%, 95% confidence interval 14.4%-25.8%). Two (1.0%) PCR, 10 (5%) ELISA, and 28 (14%) IGRA samples were positive. Travel to Ninewa governorate increased risk for AVL (P = .01). CONCLUSION: AVL was identified in 19.5% of OIF deployers; travel to northwest Iraq correlated with infection. Further studies are needed to inform risk for reactivation VL in US veterans and to target additional blood safety and surveillance measures.

Transcutaneous immunization using SLA or rLACK skews the immune response towards a Th1 profile but fails to protect BALB/c mice against a Leishmania major challenge.

Leishmaniasis is an expanding health threat worldwide complicated by the absence of an effective vaccine. We investigated transcutaneous immunization (TCI) as a needle-free immunization route which exploits the abundance of antigen presenting cells in the skin to induce both mucosal and systemic immunity. Leishmania (L.) major soluble antigens (SLA) or recombinant Leishmania homolog of receptors for activated C-kinase (rLACK) antigens were delivered transcutaneously together with cholera toxin (CT), to BALB/c mice. Mice were immunized at weeks 1, 4, and 7 with PBS, CT, SLA/CT or rLACK/CT. Two weeks after the final boost, antigen-specific IgG titers, IFN-γ ELISpot, and cytokine levels were assessed in half of the mice and the remainder were challenged with an intradermal (ear) injection of 5 × 104L. major metacyclic parasites. Mice were monitored weekly and sacrificed after 7 weeks to assess the parasite burden and to study the ear lesion immunohistopathology. Our results show that TCI with SLA or rLACK yielded high levels of anti-SLA, anti-rLACK and anti-CT IgG antibodies. A Th1-type of immune response was demonstrated with a high frequency of IFN-γ secreting cells, high levels of IFN-γ production, and lower levels of IL-10 resulting in a high IFN-γ/IL-10 ratio in mice immunized with SLA/CT or rLACK/CT. After parasite challenge, rLACK immunization was not associated with protection. In addition, SLA/CT immunized mice had larger ear lesions and an increased parasite load in the ear. Immunohistochemistry of ear biopsies stained for nitric oxide synthase revealed that staining intensity was diminished in the SLA/CT group compared to the control group. This finding suggested that less parasite killing occurred at the site of the infection. In conclusion, despite a strong Th1 type profile induced by TCI, exacerbation of infection occurred after challenge with L. major. This also correlated with low induction of nitric oxide.

Addressing a clinical challenge: guidelines for the diagnosis and treatment of leishmaniasis.

Leishmaniasis is a chronic intracellular parasitic infection that travelers, immigrants, deployed military personnel, and refugees from endemic global areas acquire from the bite of infected sand flies and carry with them, including to non-endemic countries where leishmaniasis may be an unfamiliar illness to medical providers. This commentary discusses the first clinical practice guidelines produced by the Infectious Diseases Society of America and American Society of Tropical Medicine and Hygiene for the diagnosis and management of leishmaniasis, targeted for clinicians in North America.

The Long-term Effect of Bacille Calmette-Guérin Vaccination on Tuberculin Skin Testing: A 55-Year Follow-Up Study.

BACKGROUND: Bacille Calmette-Guérin (BCG) vaccination is known to cause false-positive tuberculin skin test (TST) results from cross-reactions with mycobacterial antigens. However, the duration of BCG vaccination influence on the TST is poorly characterized. The objective of this study was to assess the long-term effect of BCG vaccination on TST reactivity. METHODS: Data on TST reactivity were prospectively collected during 1935 to 1947 as part of a clinical trial among Native Americans/Alaskan Natives and were retrospectively collected thereafter between 1948 and 1998. TST induration of ≥ 10 mm was defined as a positive reaction. Kaplan-Meier analysis and multivariate Cox regression were used to compare the time to TST conversion and reversion between the BCG and placebo groups. RESULTS: BCG vaccination after infancy was associated with an increased risk of TST reactivity in the first 15 years after vaccination (adjusted hazard ratio [HR], 2.33). This association remained during the interval 16 to 55 years after vaccination, although the effect was attenuated (adjusted HR, 1.26). Age at vaccination modestly impacted the effect of BCG on TST results in the first 15 years. Positive TST results among the BCG-vaccinated group were more likely to revert to negative results during the first 15 years but not in the latter period. CONCLUSIONS: This study provides evidence that BCG vaccination after infancy may influence TST results beyond the 10-year period conventionally accepted by the Centers for Disease Control and Prevention (CDC), extending up to 55 years after vaccination. This suggests that BCG vaccination should be taken into account when interpreting TST results regardless of the time elapsed since vaccination.

The Immunology of a Healing Response in Cutaneous Leishmaniasis Treated with Localized Heat or Systemic Antimonial Therapy.

BACKGROUND: The effectiveness of systemic antimonial (sodium stibogluconate, Pentostam, SSG) treatment versus local heat therapy (Thermomed) for cutaneous leishmaniasis was studied previously and showed similar healing rates. We hypothesized that different curative immune responses might develop with systemic and local treatment modalities. METHODS: We studied the peripheral blood immune cells in a cohort of 54 cutaneous Leishmania major subjects treated with SSG or TM. Multiparameter flow cytometry, lymphoproliferative assays and cytokine production were analyzed in order to investigate the differences in the immune responses of subjects before, on and after treatment. RESULTS: Healing cutaneous leishmaniasis lead to a significant decline in circulating T cells and NKT-like cells, accompanied by an expansion in NK cells, regardless of treatment modality. Functional changes involved decreased antigen specific CD4+ T cell proliferation (hyporesponsiveness) seen with CD8+ T cell depletion. Moreover, the healing (or healed) state was characterized by fewer circulating regulatory T cells, reduced IFN-γ production and an overall contraction in polyfunctional CD4+ T cells. CONCLUSION: Healing from cutaneous Leishmaniasis is a dynamic process that alters circulating lymphocyte populations and subsets of T, NK and NKT-like cells. Immunology of healing, through local or systemic treatments, culminated in similar changes in frequency, quality, and antigen specific responsiveness with immunomodulation possibly via a CD8+ T cell dependent mechanism. Understanding the evolving immunologic changes during healing of human leishmaniasis informs protective immune mechanisms.

Leishmaniasis: treatment updates and clinical practice guidelines review.

PURPOSE OF REVIEW: This review summarizes recent important and interesting articles investigating the challenging treatment of the parasitic infection, leishmaniasis. In addition, it compares and contrasts leishmaniasis clinical practice treatment guidelines. RECENT FINDINGS: Studies show that, in contrast to experience in India, visceral leishmaniasis in East Africa requires higher doses of liposomal amphotericin for effective treatment results and that pentavalent antimonial drugs remain efficacious. A retrospective study of visceral leishmaniasis in organ transplant patients suggests that there may be a role for secondary prophylaxis after treatment akin to HIV coinfection recommendations. The pros and cons of oral therapy with miltefosine, which cuts across leishmaniasis syndromes in its spectrum, are discussed. Cutaneous leishmaniasis clinical practice guidelines vary, although the recent European guidelines favor species-directed therapy. SUMMARY: Leishmaniasis remains a neglected tropical disease, with a need for additional clinical trials with better design and reported endpoints to lead evidence-based treatment recommendations--especially in cutaneous leishmaniasis and leishmaniasis in the immunocompromised host.

Leishmania infantum-chagasi activates SHP-1 and reduces NFAT5/TonEBP activity in the mouse kidney inner medulla.

Visceral leishmaniasis patients have been reported to have a urine concentration defect. Concentration of urine by the renal inner medulla is essentially dependent on a transcription factor, NFAT5/TonEBP, because it activates expression of osmoprotective genes betaine/glycine transporter 1 (BGT1) and sodium/myo-inositol transporter (SMIT), and water channel aquaporin-2, all of which are imperative for concentrating urine. Leishmania parasites evade macrophage immune defenses by activating protein tyrosine phosphatases, among which SHP-1 is critical. We previously demonstrated that SHP-1 inhibits tonicity-dependent activation of NFAT5/TonEBP in HEK293 cells through screening a genome-wide small interfering (si) RNA library against phosphatases (Zhou X, Gallazzini M, Burg MB, Ferraris JD. Proc Natl Acad Sci USA 107: 7072-7077, 2010). We sought to examine whether Leishmania can activate SHP-1 and inhibit NFAT5/TonEBP activity in the renal inner medulla in a murine model of visceral leishmaniasis by injection of female BALB/c mice with a single intravenous dose of 5 × 10(5) L. chagasi metacyclic promastigotes. We found that SHP-1 is expressed in the kidney inner medulla. L. chagasi activates SHP-1 with an increase in stimulatory phosphorylation of SHP-1-Y536 in the region. L. chagasi reduces expression of NFAT5/TonEBP mRNA and protein as well as expression of its targeted genes: BGT1, SMIT, and aquaporin-2. The culture supernatant from L. chagasi metacyclic promastigotes increases SHP-1 protein abundance and potently inhibits NFAT5 transcriptional activity in mIMCD3 cells. However, L. chagasi in our animal model has no significant effect on urinary concentration. We conclude that L. chagasi, most likely through its secreted virulence factors, activates SHP-1 and reduces NFAT5/TonEBP gene expression, which leads to reduced NFAT5/TonEBP transcriptional activity in the kidney inner medulla.

Multidrug-resistant tuberculosis. Recommendations for reducing risk during travel for healthcare and humanitarian work.

Healthcare and humanitarian workers who travel to work where the incidence of multidrug-resistant tuberculosis (MDR TB) is high and potential transmission may occur are at risk of infection and disease due to these resistant strains. Transmission occurs due to inadequate transmission control practices and the inability to provide timely and accurate diagnosis and treatment of persons with MDR TB. Patients risk exposure if active TB is unrecognized in workers after they return to lower-risk settings. Guidance for risk reduction measures for workers in high-risk areas is limited, and no studies confirm the efficacy of treatment regimens for latent TB infection due to MDR TB. Bacille Calmette-Guérin (BCG) vaccination decreases the risk of active TB and possibly latent infection. IFN-γ release assays differentiate TB infection from BCG vaccination effect. A series of risk reduction measures are provided as a potential strategy. These measures include risk reductions before travel, including risk assessment, TB screening, education, respirator fit testing, and BCG vaccination. Measures during travel include use of respirators in settings where this may not be common practice, transmission control practices, triaging of patients with consistent symptoms, providing education for good cough etiquette, and provision of care in well-ventilated areas, including open air areas. Risk reduction measures after return include TB screening 8 to 10 weeks later and recommendations for management of latent TB infection in areas where the likelihood of MDR TB exposure is high.

Vitamin D deficiency and its association with low bone mineral density, HIV-related factors, hospitalization, and death in a predominantly black HIV-infected cohort.

BACKGROUND: Low bone mineral density (BMD) is common among patients infected with human immunodeficiency virus (HIV) and present in higher rates in black subjects. This study assessed vitamin D levels in HIV cases versus noninfected matched controls to determine if deficiency was associated with BMD and HIV clinical outcomes. METHODS: In total, 271 military beneficiaries with HIV underwent dual energy x-ray absorptiometry (DEXA) screening in 2001-2. Serum 25OH-vitamin D levels were determined using stored serum from the time of DEXA and 6-18 months prior. Two non-HIV-infected controls for each active duty case (n = 205) were matched on age, sex, race, zip code, and season using the Department of Defense Serum Repository (DoDSR). Vitamin D levels <20 ng/mL were considered deficient. HIV-related factors and clinical outcomes were assessed using data collected in the DoD HIV Natural History study. RESULTS: In total, 165 of 205 (80.5%) active duty HIV cases had 2 matched controls available. HIV cases had greater odds of for vitamin D deficiency (VDD) compared with controls (demographics adjusted paired data odds ratio [OR], 1.46, 95% confidence interval [CI], .87-2.45), but this was not statistically significant. Blacks were disproportionately deficient (P <.001) but not relative to HIV status or BMD. Low BMD was associated with typical risk factors (low body mass index and exercise levels, alcohol use); given limited available data the relationship between tenofovir exposure and VDD or low BMD could not be determined. Analysis of HIV-specific factors and outcomes such as exposure to antiretrovirals, HIV progression, hospitalizations, and death revealed no significant associations with vitamin D levels. CONCLUSIONS: VDD was highly prevalent in black HIV- infected persons but did not explain the observed racial disparity in BMD. Vitamin D deficiency was not more common among HIV- infected persons, nor did it seem associated with HIV- related factors/clinical outcomes.

Decade-long safety and function of retroviral-modified chimeric antigen receptor T cells.

The success of adoptive T cell gene transfer for treatment of cancer and HIV is predicated on generating a response that is both durable and safe. We report long-term results from three clinical trials to evaluate gammaretroviral vector-engineered T cells for HIV. The vector encoded a chimeric antigen receptor (CAR) composed of CD4 linked to the CD3ζ signaling chain (CD4ζ). CAR T cells were detected in 98% of samples tested for at least 11 years after infusion at frequencies that exceeded average T cell levels after most vaccine approaches. The CD4ζ transgene retained expression and function. There was no evidence of vector-induced immortalization of cells; integration site distributions showed no evidence of persistent clonal expansion or enrichment for integration sites near genes implicated in growth control or transformation. The CD4ζ T cells had stable levels of engraftment, with decay half-lives that exceeded 16 years, in marked contrast to previous trials testing engineered T cells. These findings indicate that host immunosuppression before T cell transfer is not required to achieve long-term persistence of gene-modified T cells. Further, our results emphasize the safety of T cells modified by retroviral gene transfer in clinical application, as measured in >500 patient-years of follow-up. Thus, previous safety issues with integrating viral vectors are hematopoietic stem cell or transgene intrinsic, and not a general feature of retroviral vectors. Engineered T cells are a promising form of synthetic biology for long-term delivery of protein-based therapeutics. These results provide a framework to guide the therapy of a wide spectrum of human diseases.

Discordance among commercially available diagnostics for latent tuberculosis infection.

RATIONALE: There is uncertainty regarding how to interpret discordance between tests for latent tuberculosis infection. OBJECTIVES: The objective of this study was to assess discordance between commercially available tests for latent tuberculosis in a low-prevalence population, including the impact of nontuberculous mycobacteria. METHODS: This was a cross-sectional comparison study among 2,017 military recruits at Fort Jackson, South Carolina, from April to June 2009. Several tests were performed simultaneously with a risk factor questionnaire, including (1) QuantiFERON-TB Gold In-Tube test, (2) T-SPOT.TB test, (3) tuberculin skin test, and (4) Battey skin test using purified protein derivative from the Battey bacillus. MEASUREMENTS AND MAIN RESULTS: In this low-prevalence population, the specificities of the three commercially available diagnostic tests were not significantly different. Of the 88 subjects with a positive test, only 10 (11.4%) were positive to all three tests; 20 (22.7%) were positive to at least two tests. Bacille Calmette-Guérin vaccination, tuberculosis prevalence in country of birth, and Battey skin test reaction size were associated with tuberculin skin test-positive, IFN-γ release assay-negative test discordance. Increasing agreement between the three tests was associated with epidemiologic criteria indicating risk of infection and with quantitative test results. CONCLUSIONS: For most positive results the three tests identified different people, suggesting that in low-prevalence populations most discordant results are caused by false-positives. False-positive tuberculin skin test reactions associated with reactivity to nontuberculous mycobacteria and bacille Calmette-Guérin vaccination may account for a proportion of test discordance observed.

Impact of targeted testing for latent tuberculosis infection using commercially available diagnostics.

BACKGROUND: The interferon-γ release assays (IGRAs) are increasingly being used as an alternative to the tuberculin skin test (TST). Although IGRAs may have better specificity and certain logistic advantages to the TST, their use may contribute to overtesting of low-prevalence populations if testing is not targeted. The objective of this study was to evaluate the accuracy of a risk factor questionnaire in predicting a positive test result for latent tuberculosis infection using the 3 commercially available diagnostics. METHODS: A cross-sectional comparison study was performed among recruits undergoing Army basic training at Fort Jackson, South Carolina, from April through June 2009. The tests performed included: (1) a risk factor questionnaire; (2) the QuantiFERON Gold In-Tube test (Cellestis Limited, Carnegie, Victoria, Australia); (3) the T-SPOT.TB test (Oxford Immunotec Limited, Abingdon, United Kingdom); and (4) the TST (Sanofi Pasteur Ltd., Toronto, Ontario, Canada). Prediction models used logistic regression to identify factors associated with positive test results. RFQ prediction models were developed independently for each test. RESULTS: Use of a 4-variable model resulted in 79% sensitivity, 92% specificity, and a c statistic of 0.871 in predicting a positive TST result. Targeted testing using these risk factors would reduce testing by >90%. Models predicting IGRA outcomes had similar specificities as the skin test but had lower sensitivities and c statistics. CONCLUSIONS: As with the TST, testing with IGRAs will result in false-positive results if the IGRAs are used in low-prevalence populations. Regardless of the test used, targeted testing is critical in reducing unnecessary testing and treatment. CLINICAL TRIAL REGISTRATION: NCT00804713.