Feasibility of precision smoking treatment in a low-income community setting: results of a pilot randomized controlled trial in The Southern Community Cohort Study

BACKGROUND

The feasibility of precision smoking treatment in socioeconomically disadvantaged communities has not been studied.

METHODS

Participants in the Southern Community Cohort Study who smoked daily were invited to join a pilot randomized controlled trial of three smoking cessation interventions: guideline-based care (GBC), GBC plus nicotine metabolism-informed care (MIC), and GBC plus counseling guided by a polygenic risk score (PRS) for lung cancer. Feasibility was assessed by rates of study enrollment, engagement, and retention, targeting > 70% for each. Using logistic regression, we also assessed whether feasibility varied by age, sex, race, income, education, and attitudes toward precision smoking treatment.

RESULTS

Of 92 eligible individuals (79.3% Black; 68.2% with household income < $15,000), 67 (72.8%; 95% CI 63.0-80.9%) enrolled and were randomized. Of these, 58 (86.6%; 95% CI 76.4-92.8%) engaged with the intervention, and of these engaged participants, 43 (74.1%; 95% CI 61.6-83.7%) were retained at 6-month follow-up. Conditional on enrollment, older age was associated with lower engagement (OR 0.83, 95% CI 0.73-0.95, p = 0.008). Conditional on engagement, retention was significantly lower in the PRS arm than in the GBC arm (OR 0.18, 95% CI 0.03-1.00, p = 0.050). No other selection effects were observed.

CONCLUSIONS

Genetically informed precision smoking cessation interventions are feasible in socioeconomically disadvantaged communities, exhibiting high enrollment, engagement, and retention irrespective of race, sex, income, education, or attitudes toward precision smoking treatment. Future smoking cessation interventions in this population should take steps to engage older people and to sustain participation in interventions that include genetic risk counseling.

TRIAL REGISTRATION

ClinicalTrials.gov No. NCT03521141, Registered 27 April 2018, https://www.

CLINICALTRIALS

gov/study/NCT03521141.

Comparison of Rapid Antigen Tests' Performance Between Delta and Omicron Variants of SARS-CoV-2 : A Secondary Analysis From a Serial Home Self-testing Study

BACKGROUND

It is important to document the performance of rapid antigen tests (Ag-RDTs) in detecting SARS-CoV-2 variants.

OBJECTIVE

To compare the performance of Ag-RDTs in detecting the Delta (B.1.617.2) and Omicron (B.1.1.529) variants of SARS-CoV-2.

DESIGN

Secondary analysis of a prospective cohort study that enrolled participants between 18 October 2021 and 24 January 2022. Participants did Ag-RDTs and collected samples for reverse transcriptase polymerase chain reaction (RT-PCR) testing every 48 hours for 15 days.

SETTING

The parent study enrolled participants throughout the mainland United States through a digital platform. All participants self-collected anterior nasal swabs for rapid antigen testing and RT-PCR testing. All Ag-RDTs were completed at home, whereas nasal swabs for RT-PCR were shipped to a central laboratory.

PARTICIPANTS

Of 7349 participants enrolled in the parent study, 5779 asymptomatic persons who tested negative for SARS-CoV-2 on day 1 of the study were eligible for this substudy.

MEASUREMENTS

Sensitivity of Ag-RDTs on the same day as the first positive (index) RT-PCR result and 48 hours after the first positive RT-PCR result.

RESULTS

A total of 207 participants were positive on RT-PCR (58 Delta, 149 Omicron). Differences in sensitivity between variants were not statistically significant (same day: Delta, 15.5% [95% CI, 6.2% to 24.8%] vs. Omicron, 22.1% [CI, 15.5% to 28.8%]; at 48 hours: Delta, 44.8% [CI, 32.0% to 57.6%] vs. Omicron, 49.7% [CI, 41.6% to 57.6%]). Among 109 participants who had RT-PCR-positive results for 48 hours, rapid antigen sensitivity did not differ significantly between Delta- and Omicron-infected participants (48-hour sensitivity: Delta, 81.5% [CI, 66.8% to 96.1%] vs. Omicron, 78.0% [CI, 69.1% to 87.0%]). Only 7.2% of the 69 participants with RT-PCR-positive results for shorter than 48 hours tested positive by Ag-RDT within 1 week; those with Delta infections remained consistently negative on Ag-RDTs.

LIMITATION

A testing frequency of 48 hours does not allow a finer temporal resolution of the analysis of test performance, and the results of Ag-RDTs are based on self-report.

CONCLUSION

The performance of Ag-RDTs in persons infected with the SARS-CoV-2 Omicron variant is not inferior to that in persons with Delta infections. Serial testing improved the sensitivity of Ag-RDTs for both variants. The performance of rapid antigen testing varies on the basis of duration of RT-PCR positivity.

PRIMARY FUNDING SOURCE

National Heart, Lung, and Blood Institute of the National Institutes of Health.

The Fish Oil to Reduce Tobacco Use iN Expectant mothers (FORTUNE) feasibility trial

BACKGROUND

Three small clinical trials have suggested that supplementation with n-3 long-chain polyunsaturated fatty acids (eicosapentaenoic acid and docosahexaenoic acid) found in fish oils may reduce nicotine cravings and at higher doses reduce cigarette consumption. Pregnant women who smoke have fewer pharmacologic options to aid them with smoking cessation. Although n-3 long-chain polyunsaturated fatty acid supplementation has been studied in pregnancy, few studies have evaluated doses of ≥4 g per day, and no previous studies have selectively enrolled pregnant women who smoke. High-dose n-3 long-chain polyunsaturated fatty acids may aid cessation but could be poorly tolerated in pregnant women who smoke because of gastrointestinal side effects.

OBJECTIVE

We conducted a feasibility trial to determine the tolerability of high-dose n-3 long-chain polyunsaturated fatty acid supplementation in pregnant women who smoked. We hypothesized that n-3 long-chain polyunsaturated fatty acid doses of 4.2 g a day would be well-tolerated relative to an olive oil placebo. We assessed red blood cell phospholipid membrane concentrations at baseline and end of therapy (4 weeks) and piloted outcomes for a future efficacy trial of n-3 long-chain polyunsaturated fatty acid supplementation for smoking cessation in pregnancy.

STUDY DESIGN

We recruited 28 pregnant women between the gestational ages of 6 and 36 weeks who reported daily cigarette smoking and were motivated to quit to participate in a double-blind placebo-controlled randomized feasibility trial of 4.2 g per day of n-3 long-chain polyunsaturated fatty acid supplementation. Participants reported cigarettes per day, completed the Fagerström Test for Cigarette Dependence, and provided blood, urine, and exhaled CO samples. We used repeated-measures analysis of variance to pilot analyses of changes in cigarettes per day and Fagerström Test for Cigarette Dependence scores.

RESULTS

At baseline, red blood cell membrane eicosapentaenoic acid concentrations were negatively correlated with cigarettes per day (r=-0.44; P=.04). By 4 weeks, circulating n-3 long-chain polyunsaturated fatty acid levels increased by 18% in the n-3 long-chain polyunsaturated fatty acid supplementation arm vs a decrease of 3% in the placebo arm. Occurrence of gastrointestinal side effects such as burping, heartburn, diarrhea, abdominal pain, or nausea did not differ statistically between study arms. At 4 weeks, participants allocated to the n-3 long-chain polyunsaturated fatty acids arm reported a median of 3 cigarettes per day (interquartile range, 1-8) vs 7 cigarettes per day (interquartile range, 1-14) in the placebo arm, which was not statistically significant (P=.99). Participants allocated to the n-3 long-chain polyunsaturated fatty acids arm had a decrease of 1 (interquartile range, 0-1) on the Fagerström Test for Cigarette Dependence score vs 0 (interquartile range, 0-0) for placebo (P=.46).

CONCLUSION

High-dose n-3 long-chain polyunsaturated fatty acids may be tolerated in pregnant women who smoke; however, there was a high level of participant dropout, with more participants allocated to the fish oil arm becoming lost to follow-up. These results will inform the design of a future large-scale randomized controlled trial to test the impact of fish oil supplements on smoking cessation in pregnancy.

Dispositional optimism and optimistic bias: Associations with cessation motivation, confidence, and attitudes

OBJECTIVE

To test whether 2 conceptually overlapping constructs, dispositional optimism (generalized positive expectations) and optimistic bias (inaccurately low risk perceptions), may have different implications for smoking treatment engagement.

METHOD

Predominantly Black, low-income Southern Community Cohort study smokers (n = 880) self-reported dispositional optimism and pessimism (Life Orientation Test-Revised subscales: 0 = neutral, 12 = high optimism/pessimism), comparative lung cancer risk (Low/Average/High), and information to calculate objective lung cancer risk (Low/Med/High). Perceived risk was categorized as accurate (perceived = objective), optimistically-biased (perceived < objective), or pessimistically-biased (perceived > objective). One-way ANOVAs tested associations between dispositional optimism/pessimism and perceived risk accuracy. Multivariable logistic regressions tested independent associations of optimism/pessimism and perceived risk accuracy with cessation motivation (Low/High), confidence (Low/High), and precision treatment attitudes (Favorable/Unfavorable), controlling for sociodemographics and nicotine dependence.

RESULTS

Mean dispositional optimism/pessimism scores were 8.41 (SD = 2.59) and 5.65 (SD = 3.02), respectively. Perceived lung cancer risk was 38% accurate, 27% optimistically-biased, and 35% pessimistically-biased. Accuracy was unrelated to dispositional optimism (F(2, 641) = 1.23, p = .29), though optimistically-biased (vs. pessimistically-biased) smokers had higher dispositional pessimism (F(2, 628) = 3.17, p = .043). Dispositional optimism was associated with higher confidence (Adjusted odds ratio [AOR] = 1.71, 95% CI [1.42, 2.06], p < .001) and favorable precision treatment attitudes (AOR = 1.66, 95% CI [1.37, 2.01], p < .001). Optimistically-biased (vs. accurate) risk perception was associated with lower motivation (AOR = .64, 95% CI [.42, .98], p = .041) and less favorable precision treatment attitudes (AOR = .59, 95% CI [.38, .94], p = .029).

CONCLUSIONS

Dispositional optimism and lung cancer risk perception accuracy were unrelated. Dispositional optimism was associated with favorable engagement-related outcomes and optimistically-biased risk perception with unfavorable outcomes, reinforcing the distinctiveness of these constructs and their implications for smoking treatment. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Comparative Effectiveness of Postdischarge Smoking Cessation Interventions for Hospital Patients: The Helping HAND 4 Randomized Clinical Trial

IMPORTANCE

Smoking cessation interventions for hospitalized patients must continue after discharge to improve long-term tobacco abstinence. How health systems can best deliver postdischarge tobacco treatment is uncertain.

OBJECTIVE

To determine if health system-based tobacco cessation treatment after hospital discharge produces more long-term tobacco abstinence than referral to a community-based quitline.

DESIGN, SETTING, AND PARTICIPANTS

This randomized clinical trial was conducted September 2018 to November 2020 in 3 hospitals in Massachusetts, Pennsylvania, and Tennessee. Cigarette smokers admitted to a study hospital who received brief in-hospital tobacco treatment and wanted to quit smoking were recruited for participation and randomized for postdischarge treatment to health system-based Transitional Tobacco Care Management (TTCM) or electronic referral to a community-based quitline (QL). Both multicomponent interventions offered smoking cessation counseling and nicotine replacement therapy (NRT) for up to 3 months. Data were analyzed from February 1, 2021, to April 25, 2022.

INTERVENTIONS

TTCM provided 8 weeks of NRT at discharge and 7 automated calls with a hospital-based counselor call-back option. The QL intervention sent referrals from the hospital electronic health record to the state quitline, which offered 5 counseling calls and an NRT sample.

MAIN OUTCOMES AND MEASURES

The main outcome was biochemically verified past 7-day tobacco abstinence at 6 months. Self-reported point-prevalence and continuous tobacco abstinence and tobacco treatment utilization were assessed 1, 3, and 6 months after discharge.

RESULTS

A total of 1409 participants (mean [SD] age, 51.7 [12.6] years; 784 [55.6%] women; mean [SD] 16.4 [10.6] cigarettes/day) were recruited, including 706 randomized to TTCM and 703 randomized to QL. Participants were comparable at baseline, including 216 Black participants (15.3%), 82 Hispanic participants (5.8%), and 1089 White participants (77.3%). At 1 and 3 months after discharge, more TTCM participants than QL participants used cessation counseling (1 month: 245 participants [34.7%] vs 154 participants [21.9%]; 3 months: 248 participants [35.1%] vs 123 participants [17.5%]; P < .001) and pharmacotherapy (1 month: 455 participants [64.4%] vs 324 participants [46.1%]; 3 months: 367 participants [52.0%] vs 264 participants [37.6%]; P < .001). More TTCM than QL participants reported continuous abstinence for 3 months (RR, 1.30; 95% CI, 1.06-1.58) and point-prevalence abstinence at 1 month (RR, 1.22; 95% CI, 1.08-1.35) and 3 months (RR, 1.23; 95% CI, 1.09-1.37) but not at 6 months (RR, 1.14; 95% CI, 0.99-1.29). The primary outcome, biochemically verified point-prevalence abstinence at 6 months, was not statistically significantly different between groups (19.9% vs 16.9%; RR, 1.18; 95% CI, 0.92-1.50).

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial, biochemically verified tobacco abstinence rates were not significantly different between groups at the 6-month follow-up. However, the health system-based model was superior to the community-based quitline model throughout the 3 months of active treatment. A longer duration of postdischarge treatment may sustain the superiority of the health system-based model.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03603496.

Comparison of Rapid Antigen Tests' Performance between Delta (B.1.61.7; AY.X) and Omicron (B.1.1.529; BA1) Variants of SARS-CoV-2: Secondary Analysis from a Serial Home Self-Testing Study

Background

There is a need to understand the performance of rapid antigen tests (Ag-RDT) for detection of the Delta (B.1.61.7; AY.X) and Omicron (B.1.1.529; BA1) SARS-CoV-2 variants.

Methods

Participants without any symptoms were enrolled from October 18, 2021 to January 24, 2022 and performed Ag-RDT and RT-PCR tests every 48 hours for 15 days. This study represents a non-pre-specified analysis in which we sought to determine if sensitivity of Ag-RDT differed in participants with Delta compared to Omicron variant. Participants who were positive on RT-PCR on the first day of the testing period were excluded. Delta and Omicron variants were defined based on sequencing and date of first RT-PCR positive result (RT-PCR+). Comparison of Ag-RDT performance between the variants was based on sensitivity, defined as proportion of participants with Ag-RDT+ results in relation to their first RT-PCR+ result, for different duration of testing with rapid Ag-RDT. Subsample analysis was performed based on the result of participants' second RT-PCR test within 48 hours of the first RT-PCR+ test.

Results

From the 7,349 participants enrolled in the parent study, 5,506 met the eligibility criteria for this analysis. A total of 153 participants were RT-PCR+ (61 Delta, 92 Omicron); among this group, 36 (23.5%) tested Ag-RDT+ on the same day, and 84 (54.9%) tested Ag-RDT+ within 48 hours as first RT-PCR+. The differences in sensitivity between variants were not statistically significant (same-day: Delta 16.4% [95% CI: 8.2-28.1] vs Omicron 28.2% [95% CI: 19.4-38.6]; and 48-hours: Delta 45.9% [33.1-59.2] vs. Omicron 60.9% [50.1-70.9]). This trend continued among the 86 participants who had consecutive RT-PCR+ result (48-hour sensitivity: Delta 79.3% [60.3-92.1] vs. Omicron: 89.5% [78.5-96.0]). Conversely, the 38 participants who had an isolated RT-PCR+ remained consistently negative on Ag-RDT, regardless of the variant.

Conclusions

The performance of Ag-RDT is not inferior among individuals infected with the SARS-CoV-2 Omicron variant as compared to the Delta variant. The improvement in sensitivity of Ag-RDT noted with serial testing is consistent between Delta and Omicron variant. Performance of Ag-RDT varies based on duration of RT-PCR+ results and more studies are needed to understand the clinical and public health significance of individuals who are RT-PCR+ for less than 48 hours.

Comparative effectiveness of post-discharge strategies for hospitalized smokers: Study protocol for the Helping HAND 4 randomized controlled trial

BACKGROUND

Tobacco smoking remains the leading preventable cause of death in the US. A hospital admission provides smokers with a unique opportunity to stop smoking because it requires temporary tobacco abstinence while illness may enhance motivation to quit. Hospital interventions must continue post-discharge to increase tobacco abstinence long-term, but how best to accomplish this remains unclear. Building on two previous randomized controlled trials, each of which tested smoking cessation interventions that began in hospital and continued after discharge, this trial compares two interventions that provide sustained smoking cessation treatment after hospital discharge with the goal of improving long-term smoking cessation rates among hospitalized smokers.

METHODS/DESIGN

Helping HAND 4 is a three-site randomized controlled trial that compares the effectiveness of two active interventions for producing validated past 7-day tobacco abstinence 6 months after hospital discharge. Smokers who are admitted to three hospitals receive a standard in-hospital smoking intervention, and those who plan to quit smoking after discharge are recruited and randomly assigned to two interventions that begin at discharge, Personalized Tobacco Care Management (PTCM) or Quitline eReferral. Each lasts 3 months. At discharge, PTCM provides 8 weeks of free nicotine replacement (NRT; a participant's choice of patch, gum, lozenge, or a combination) and then proactive smoking cessation support using an automated communication platform and live contact with a tobacco treatment specialist who is based in the health care system. In the eReferral condition, a direct referral is made from the hospital electronic health record to a community-based resource, the state's telephone quitline. The quitline provides up to 8 weeks of free NRT and offers behavioral support via a series of phone calls from a trained coach. Outcomes are assessed at 1, 3, and 6 months after discharge. The study hypothesis is that PTCM will produce higher quit rates than eReferral.

DISCUSSION

Helping HAND 4 is a pragmatic trial that aims to evaluate interventions in real-world conditions. This project will give hospital systems critical evidence-based tools for meeting National Hospital Quality Measures for tobacco treatment and maximizing their ability to improve cessation rates and overall health for the millions of smokers hospitalized annually in the US.

TRIAL REGISTRATION

Prospectively registered prior to start of enrollment at Clinicaltrials.gov, NCT03603496 (July 27, 2018). https://register.clinicaltrials.gov/prs/app/action/SelectProtocol?sid=S00084MJ&selectaction=Edit&uid=U00002G7&ts=2&cx=ff0oxn.

Attitudes toward Precision Treatment of Smoking in the Southern Community Cohort Study

BACKGROUND

Precision interventions using biological data may enhance smoking treatment, yet are understudied among smokers who are disproportionately burdened by smoking-related disease.

METHODS

We surveyed smokers in the NCI-sponsored Southern Community Cohort Study, consisting primarily of African-American, low-income adults. Seven items assessed attitudes toward aspects of precision smoking treatment, from undergoing tests to acting on results. Items were dichotomized as favorable (5 = strongly agree/4 = agree) versus less favorable (1 = strongly disagree/2 = disagree/3 = neutral); a summary score reflecting generalized attitudes was also computed. Multivariable logistic regression tested independent associations of motivation (precontemplation, contemplation, and preparation) and confidence in quitting (low, medium, and high) with generalized attitudes, controlling for sociodemographic factors and nicotine dependence.

RESULTS

More than 70% of respondents endorsed favorable generalized attitudes toward precision medicine, with individual item favorability ranging from 64% to 83%. Smokers holding favorable generalized attitudes reported higher income and education (P < 0.05). Predicted probabilities of favorable generalized attitudes ranged from 63% to 75% across motivation levels [contemplation vs. precontemplation: adjusted odds ratio (AOR) = 2.10, 95% confidence interval (CI), 1.36-3.25, P = 0.001; preparation vs. precontemplation: AOR = 1.83, 95% CI, 1.20-2.78, P = 0.005; contemplation vs. preparation: AOR = 1.15, 95% CI, 0.75-1.77, P = 0.52] and from 59% to 78% across confidence (medium vs. low: AOR = 1.91, 95% CI, 1.19-3.07, P = 0.007; high vs. low: AOR = 2.62, 95% CI, 1.68-4.10, P < 0.001; medium vs. high: AOR = 0.73, 95% CI, 0.48-1.11, P = 0.14).

CONCLUSIONS

Among disproportionately burdened community smokers, most hold favorable attitudes toward precision smoking treatment. Individuals with lower motivation and confidence to quit may benefit from additional intervention to engage with precision smoking treatment.

IMPACT

Predominantly favorable attitudes toward precision smoking treatment suggest promise for future research testing their effectiveness and implementation.

Improving Community Advisory Board Engagement in Precision Medicine Research to Reduce Health Disparities

Community Advisory Boards (CABs) are used in efforts to reduce health disparities; however, there is little documentation in the literature regarding their use in precision medicine research. In this case study, an academic-CAB partnership developed a questionnaire and patient educational materials for two precision smoking cessation interventions that involved use of genetic or genetically-informed information. The community-engaged research (CEnR) literature provided a framework for enhancing benefits to CAB members involved in developing research documents for use with a low-income, ethnically diverse population of smokers.The academic partners integrated three CEnR strategies: 1) in-meeting statements acknowledging their desire to learn from community partners, 2) in-meeting written feedback to and from community partners, and 3) a survey to obtain CAB member feedback post-meetings. Strategies 1 and 2 yielded modifications to pertinent study materials, as well as suggestions for improving meeting operations that were then adopted, as appropriate, by the academic partners. The survey indicated that CAB members valued the meeting procedure changes which appeared to have contributed to improvements in attendance and satisfaction with the meetings. Further operationalization of relevant partnership constructs and development of tools for measuring these aspects of community-academic partnerships is warranted to support community engagement in precision medicine research studies.

MEG-SIM: a web portal for testing MEG analysis methods using realistic simulated and empirical data

MEG and EEG measure electrophysiological activity in the brain with exquisite temporal resolution. Because of this unique strength relative to noninvasive hemodynamic-based measures (fMRI, PET), the complementary nature of hemodynamic and electrophysiological techniques is becoming more widely recognized (e.g., Human Connectome Project). However, the available analysis methods for solving the inverse problem for MEG and EEG have not been compared and standardized to the extent that they have for fMRI/PET. A number of factors, including the non-uniqueness of the solution to the inverse problem for MEG/EEG, have led to multiple analysis techniques which have not been tested on consistent datasets, making direct comparisons of techniques challenging (or impossible). Since each of the methods is known to have their own set of strengths and weaknesses, it would be beneficial to quantify them. Toward this end, we are announcing the establishment of a website containing an extensive series of realistic simulated data for testing purposes ( http://cobre.mrn.org/megsim/ ). Here, we present: 1) a brief overview of the basic types of inverse procedures; 2) the rationale and description of the testbed created; and 3) cases emphasizing functional connectivity (e.g., oscillatory activity) suitable for a wide assortment of analyses including independent component analysis (ICA), Granger Causality/Directed transfer function, and single-trial analysis.

Resident selection and predictors of performance: can we be evidence based?

Selection of orthopaedic residents can be a difficult process; we have endeavored to make it more objective by developing a scoring methodology for screening applications. The purpose of this investigation is to determine if an academic score, using objective elements only, will discriminate among applicants and will correlate with outcomes. Applications to our orthopaedic residency program for 2004 and 2005 were assigned an academic score as a screening tool in the residency selection process. Data was analyzed for the entire group both by gender and whether the applicant had interviewed for the program. Additionally, the applications of program graduates over the past 5 years were retrospectively assigned academic scores, which were compared with outcomes of the training program. Academic scores for applicants formed a generally normal distribution, and residents training in the program generally had higher scores. The distribution of scores for female applicants was similar to male applicants; however, a greater percentage of female applicants interviewed for the program. Scores on the OITE and ABOS examinations tended to parallel academic scores, but faculty ratings of performance in the program showed no difference between those with high and low academic scores. Calculating academic scores makes the application screening process more objective but does not appear to correlate with outcomes of the training program.

Effects of ultraviolet radiation on the pathogenesis of Mycobacterium lepraemurium infection in mice

The purpose of this study was to determine whether exposing mice to ultraviolet radiation (UVR) would alter the pathogenesis of infection with Mycobacterium lepraemurium (MLM), which causes a chronic, progressive, lethal disease in susceptible mouse strains. BALB/c mice were irradiated on dorsal skin with various doses of UVR from FS40 sunlamps 3 days before infection with MLM in the hind footpad. The course of disease was followed by assessing the number of acid-fast bacteria in the footpad, regional lymph node and spleen, and measuring the size of the lesion at the site of MLM infection at various times after infection. Mice were also tested periodically for a delayed-type hypersensitivity (DTH) response by injecting MLM antigen into the uninfected footpad and measuring footpad swelling 24 hours later. Mice treated with a single high dose of UVR (45 kJ/m2) had significantly more bacteria in the infected footpad, lymph node and spleen than unirradiated control animals. They also had larger lesions at the site of MLM infection and exhibited significant suppression of the DTH response at 3 and 6 months after infection. Injection of mice s.c. in the footpad with MLM 3d after 45 kJ/m2 UVR reduced the median survival time from 391 to 305 d and after i.v. infection from 171 to 139 d. Dose-response studies indicated that exposing mice to 2.3 kJ/m2 of UVR, which is approximately 1 minimal erythemal dose for this strain, suppressed the DTH response by 50% at 3 months after infection.(ABSTRACT TRUNCATED AT 250 WORDS)