Safety and immunogenicity of a purified inactivated Zika virus vaccine candidate in adults primed with a Japanese encephalitis virus or yellow fever virus vaccine in the USA: a phase 1, randomised, double-blind, placebo-controlled clinical trial

BACKGROUND

Zika virus infection is a threat to at-risk populations, causing major birth defects and serious neurological complications. Development of a safe and efficacious Zika virus vaccine is, therefore, a global health priority. Assessment of heterologous flavivirus vaccination is important given co-circulation of Japanese encephalitis virus and yellow fever virus with Zika virus. We investigated the effect of priming flavivirus naive participants with a licensed flavivirus vaccine on the safety and immunogenicity of a purified inactivated Zika vaccine (ZPIV).

METHODS

This phase 1, placebo-controlled, double-blind trial was done at the Walter Reed Army Institute of Research Clinical Trials Center in Silver Spring, MD, USA. Eligible participants were healthy adults aged 18-49 years, with no detectable evidence of previous flavivirus exposure (by infection or vaccination), as measured by a microneutralisation assay. Individuals with serological evidence of HIV, hepatitis B, or hepatitis C infection were excluded, as were pregnant or breastfeeding women. Participants were recruited sequentially into one of three groups (1:1:1) to receive no primer, two doses of intramuscular Japanese encephalitis virus vaccine (IXIARO), or a single dose of subcutaneous yellow fever virus vaccine (YF-VAX). Within each group, participants were randomly assigned (4:1) to receive intramuscular ZPIV or placebo. Priming vaccinations were given 72-96 days before ZPIV. ZPIV was administered either two or three times, at days 0, 28, and 196-234. The primary outcome was occurrence of solicited systemic and local adverse events along with serious adverse events and adverse events of special interest. These data were analysed in all participants receiving at least one dose of ZPIV or placebo. Secondary outcomes included measurement of neutralizing antibody responses following ZPIV vaccination in all volunteers with available post-vaccination data. This trial is registered at ClinicalTrials.gov, NCT02963909.

FINDINGS

Between Nov 7, 2016, and Oct 30, 2018, 134 participants were assessed for eligibility. 21 did not meet inclusion criteria, 29 met exclusion criteria, and ten declined to participate. 75 participants were recruited and randomly assigned. 35 (47%) of 75 participants were male and 40 (53%) were female. 25 (33%) of 75 participants identified as Black or African American and 42 (56%) identified as White. These proportions and other baseline characteristics were similar between groups. There were no statistically significant differences in age, gender, race, or BMI between those who did and did not opt into the third dose. All participants received the planned priming IXIARO and YF-VAX vaccinations, but one participant who received YF-VAX dropped out before receipt of the first dose of ZPIV. 50 participants received a third dose of ZPIV or placebo, including 14 flavivirus-naive people, 17 people primed with Japanese encephalitis virus vaccine, and 19 participants primed with yellow fever vaccine. Vaccinations were well tolerated across groups. Pain at the injection site was the only adverse event reported more frequently in participants who received ZPIV than in those who received placebo (39 [65%] of 60 participants, 95% CI 51·6-76·9 who received ZPIV vs three [21·4%] of 14 who received placebo; 4·7-50·8; p=0·006). No patients had an adverse event of special interest or serious adverse event related to study treatment. At day 57, the flavivirus-naive volunteers had an 88% (63·6-98·5, 15 of 17) seroconversion rate (neutralising antibody titre ≥1:10) and geometric mean neutralising antibody titre (GMT) against Zika virus of 100·8 (39·7-255·7). In the Japanese encephalitis vaccine-primed group, the day 57 seroconversion rate was 31·6% (95% CI 12·6-56·6, six of 19) and GMT was 11·8 (6·1-22·8). Participants primed with YF-VAX had a seroconversion rate of 25% (95% CI 8·7-49·1, five of 20) and GMT of 6·6 (5·2-8·4). Humoral immune responses rose substantially following a third dose of ZPIV, with seroconversion rates of 100% (69·2-100; ten of ten), 92·9% (66·1-99·8; 13 of 14), and 60% (32·2-83·7, nine of 15) and GMTs of 511·5 (177·6-1473·6), 174·2 (51·6-587·6), and 79 (19·0-326·8) in the flavivirus naive, Japanese encephalitis vaccine-primed, and yellow fever vaccine-primed groups, respectively.

INTERPRETATION

We found ZPIV to be well tolerated in flavivirus naive and primed adults but that immunogenicity varied significantly according to antecedent flavivirus vaccination status. Immune bias towards the flavivirus antigen of initial exposure and the timing of vaccination may have impacted responses. A third ZPIV dose overcame much, but not all, of the discrepancy in immunogenicity. The results of this phase 1 clinical trial have implications for further evaluation of ZPIV's immunisation schedule and use of concomitant vaccinations.

FUNDING

Department of Defense, Defense Health Agency; National Institute of Allergy and Infectious Diseases; and Division of Microbiology and Infectious Disease.

Effectiveness of the DROP training for military behavioral health providers targeting therapeutic alliance and premature dropout

AbstractPremature discontinuation from behavioral health treatment is a major problem reducing effectiveness of care in military populations. A training was developed and delivered to 622 behavioral health providers across 15 sites within the Army behavioral healthcare system. The training taught two techniques to foster treatment engagement: (1) Progress Informed Treatment, consisting of reviewing symptom assessments and outcome measures, and (2) assessment and discussion of the treatment alliance via a paper survey given near the end of each session. Eighty-five percent of providers indicated the training was useful and 89% of providers incorporated a technique into their practice. Dropout before the fourth session was significantly reduced in the six months following training, from 72.5% to 67.1% in Service Members (SM; X²(1, N=9127) = 39.58, p < .001). In both the pre and post-training periods, providers working at the Master's level, SM aged 17 or 46 or older, and clients receiving a mood, PTSD, anxiety, adjustment, substance or childhood/adolescent psychiatric diagnosis experienced significantly less dropout, while SM aged 18-21 had significantly more dropout. This training is a feasible and available option to increase treatment engagement and improve treatment outcomes for service members.

Far Forward Behavioral Health Service Delivery in Future Combat Environments: A Qualitative Needs Assessment

INTRODUCTION

It is expected that future multi-domain operational (MDO) combat environments will be characterized by limited capabilities for immediate combat stress control support services for soldiers or immediate evacuation from theater. The operational requirements of the future battlefield make it unlikely that current models for behavioral health (BH) treatment could be implemented without significant adjustments. We conducted a qualitative study with Special Forces medics and operators and soldiers who had deployed to austere conditions in small groups in an effort to inform construction of a BH service delivery model for an MDO environment. The objectives of this study were (1) characterizing stressors and BH issues that were encountered and (2) describing mitigation strategies and resources that were useful or needed in these types of deployments.

MATERIALS AND METHODS

Six focus groups were conducted at three army installations with 23 active duty soldiers, including three groups of medics using a semi-structured interview guide focused on stressors they encountered during deployments to austere conditions, and the impact of those stressors on mission and focus. Focus group recordings were transcribed, imported into NVivo software (version 12), and independently coded by two researchers. An analysis was then conducted to develop themes across participants. The study was reviewed by the Walter Reed Army Institute of Research Human Subjects Protection Board.

RESULTS

Behavioral health concerns were commonly cited as a stressor in far forward environments. Other common stressors included ineffective or inexperienced leaders, as well as poor team dynamics (e.g., communication and cohesion). Four primary strategies were mentioned as mitigations for deployment stressors: leadership, morale, resilience training, and strength of the team. When asked about resources or training that would have helped with these types of deployments, participants frequently mentioned the availability of BH providers and development of new and realistic BH skills trainings for non-providers and leaders.

CONCLUSIONS

Current models for treating BH problems need to be adapted for the future MDO environments in which soldiers will be expected to deploy. Understanding what issues need to be addressed in these environments and how they can best be delivered is an important first step. This study is the first to use qualitative results from those who have already deployed to such environments to describe the stressors and BH issues that were most commonly encountered, the mitigation strategies used, and the resources that were useful or needed.

Behavioral Health Provider Attitudes Toward Behavioral Health Profiles in the U.S. Army

INTRODUCTION

U.S. Army healthcare providers' use of profiles to document and communicate behavioral health (BH) condition limitations to commanders is vital to understanding both the individual soldier's BH readiness for missions and, as an aggregate, the unit's overall BH readiness status. Quantitative work exploring the link between soldier attitudes toward BH profiles and treatment utilization found that profiles may actually promote increases in treatment-seeking behavior in those receiving conventional BH services. BH provider attitudes on the subject, however, have not been quantitatively explored. Using data from the recently described Behavioral Health Readiness and Decision-Making Instrument (B-REDI) study, the current inquiry addresses this by examining BH providers' pre-/post-B-REDI attitudes toward BH profiles, including therapeutic alliance, to better understand how BH profiles may impact BH treatment.

METHODS

This study was approved by the WRAIR Institutional Review Board and is part of the larger B-REDI study. BH providers (n = 307) across five installations supporting active duty U.S. Army Divisions completed surveys longitudinally across three time points from September 2018 to March 2019. The survey specific to this study included five items, developed by WRAIR, assessing BH provider attitudes toward BH profiles. Of the providers who completed the survey, 250 (81%) consented to participate in the study and 149 (60%) completed the 3-month follow-up survey.

RESULTS

Over 80% of BH providers expressed agreement with each of three items assessing rationale for issuing BH profiles in both the pre- and post B-REDI period. Specifically, most providers agreed that profiles facilitate commander support to the soldier, afford soldiers resources for recovery, and give commanders increased understanding of soldier health for mission planning. Twenty-six percent of BH providers agreed, 46% were neutral, and 28% disagreed on whether profile impact on the soldier was positive or not in the pre-B-REDI period, but there was a significant positive trend relative to baseline in the post B-REDI period. The vast majority of providers (≥94%) did not endorse agreement that BH profiles negatively impact therapeutic alliance in either the pre- or post-B-REDI period.

CONCLUSIONS

Assuming that therapeutic alliance and perceptions of BH profile impact on soldiers are useful proxy measures of how treatment utilization may be affected by profiling, this inquiry fails to establish any meaningful negative association between them. This may provide some additional reassurance to BH providers and policymakers that efforts to improve readiness decision-making, such as B-REDI, and increased profiling in conventional military BH settings may not negatively impact treatment utilization rates.

Methodology of the U.S. Army's Suicide Prevention Leadership Tool Study: The Behavioral Health Readiness and Suicide Risk Reduction Review (R4)

INTRODUCTION

The Secretary of the U.S. Army issued two directives in late 2017 to directly combat the problem of suicide in the U.S. Army. The first was to develop an Army tool to assist commanders and first-line leaders in preventing suicide and improving behavioral health (BH) outcomes, which has been previously published as the BH Readiness and Risk Reduction Review (R4). The second was to conduct an evaluation study of the tool with Army units in the field. This study is the first to empirically examine the Army's tool-based methods for identifying and caring for the health and welfare of soldiers at risk for suicide, and this article outlines the methodology employed to study the effectiveness of the R4 tools and accomplish the Secretary's second directive.

METHODS

The Walter Reed Army Institute of Research Institutional Review Board approved the R4 study. The study employed a repeated measurements in pre/post quasi-experimental design, including a nonequivalent but comparable business-as-usual control group. The R4 intervention consisted of the R4 tools, accompanying instructions, and an orientation. Samples were drawn from two geographically separated U.S. Army divisions in the continental United States, each composed of four comparable brigades. Study implementation consisted of three phases and three data collections over the course of 12 months. Soldiers completed anonymous survey instruments to assess a range of health factors, behaviors, characteristics, tool-related decision-making processes, and the frequency, type, and quality of interactions between soldiers and leaders.

RESULTS

The R4 study commenced on May 6, 2019, and concluded on June 4, 2020. Sample size goals were achieved for both the divisions at all three data collection time points.

CONCLUSIONS

The methodology of the R4 study is critical for the U.S. Army from both a precedential and an outcome-based standpoint. Despite the use of many previous tools and programs for suicide prevention, this is the first time the Army has been able to empirically test the effectiveness of tool-supported decision-making among Army units in a rigorous fashion. The methodology of such a test is a critical marker for future interventional inquiries on the subject of suicide in the Army, and the results will allow for more informed decision-making by leaders when approaching these ongoing challenges.

Soldier Attitudes Toward Behavioral Health Profiles in the US Army

INTRODUCTION

Behavioral health (BH) readiness is a critical component of U.S. Army personnel readiness. Medical providers issue BH profiles in order to communicate BH-related duty limitations to the commander and reflect BH force readiness on both micro/macro-levels. A recent report indicates BH profile underutilization may be significantly elevating U.S. Army safety and mission-failure risks, and a study of BH provider decision-making suggests some providers may be hesitant to use profiles due to concerns that soldiers' attitudes toward BH profiles may negatively impact treatment utilization. This potential link, however, has not been empirically examined. This study addresses this gap by assessing soldiers' attitudes towards BH profiles to better understand how BH profiles may impact treatment utilization and explore for any BH profile-related stigma effect.

METHODS

Approved by the Walter Reed Army Institute of Research (WRAIR) Institutional Review Board as part of the Land Combat Study II, the survey specific to this study included eight WRAIR-developed items assessing soldier attitudes toward BH profiles. Soldiers (N = 1,043) from two active duty U.S. Army brigades completed cross-sectional, anonymous surveys in 2017-2018. Soldier self-reported BH care utilization was assessed and used to create sub-groups for analysis.

RESULTS

A majority of soldiers indicated that being placed on a BH profile would make them as or more likely to seek (71%) and no more or less likely to drop out (84%) of BH care. Among soldiers who had received BH care, BH profiles were associated with more favorable treatment seeking attitudes among those inclined to access conventional BH services and less favorable treatment seeking and maintenance attitudes among those inclined to access BH services from sources incapable of issuing profiles. Negative attitudes towards BH profiles were significantly more prevalent when compared to physical injury profiles, except in the group who had received BH care from a source incapable of issuing a profile. No significant proportional differences were observed among soldiers toward the rationale for BH profiles. Almost all soldiers (95% or greater) preferred their BH condition not come to the commander's attention during pre-deployment screening (SRP), choosing either BH profile or crisis options instead.

CONCLUSIONS

Results suggest soldiers who would be less likely to seek or more likely to drop out of BH care due to a BH profile may be those that are less likely to access conventional BH services in the first place. This may provide some preliminary reassurance to conventional providers that increased BH profiling practices may not be inversely proportional to the amount of BH care delivered and may encourage treatment-seeking behaviors among the population they serve. Soldiers seeking BH care from sources incapable of issuing a profile may be sensitive to a potential BH profile-related stigma effect (possibly more global profile-related effect in this group), which should be factored into policy outreach efforts. A BH profile represents a more palatable BH duty limitation disclosure option for many soldiers, and supports the merits of a disclosure process that is earlier than SRP for promoting risk mitigation and more honest appraisals of BH mission-readiness levels.

Results of the Behavioral Health Readiness Evaluation and Decision-Making Instrument Study

INTRODUCTION

Recent reports have demonstrated behavioral health (BH) system and individual provider challenges to BH readiness success. These pose a risk to winning on the battlefield and present a significant safety issue for the Army. One of the most promising areas for achieving better BH readiness results lies in improving readiness decision-making support for BH providers. The Walter Reed Army Institute of Research (WRAIR) has taken the lead in addressing this challenge by developing and empirically testing such tools. The results of the Behavioral Health Readiness Evaluation and Decision-Making Instrument (B-REDI) field study are herein described.

METHODS

The B-REDI study received WRAIR Institutional Review Board approval, and BH providers across five U.S. Army Forces Command installations completed surveys from September 2018 to March 2019. The B-REDI tools/training were disseminated to 307 providers through random clinic assignments. Of these, 250 (81%) providers consented to participate and 149 (60%) completed both initial and 3-month follow-up surveys. Survey items included a wide range of satisfaction, utilization, and proficiency-level outcome measures. Analyses included examinations of descriptive statistics, McNemar's tests pre-/post-B-REDI exposure, Z-tests with subgroup populations, and chi-square tests with demographic comparisons.

RESULTS

The B-REDI resulted in broad, statistically significant improvements across the measured range of provider proficiency-level outcomes. Net gains in each domain ranged from 16.5% to 22.9% for knowledge/awareness (P = .000), from 11.1% to 15.8% for personal confidence (P = .001-.000), and from 6.2% to 15.1% for decision-making/documentation (P = .035-.002) 3 months following B-REDI initiation, and only one (knowledge) failed to maintain a statistically significant improvement in all of its subcategories. The B-REDI also received high favorability ratings (79%-97% positive) across a wide array of end-user satisfaction measures.

CONCLUSIONS

The B-REDI directly addresses several critical Army BH readiness challenges by providing tangible decision-making support solutions for BH providers. Providers reported high degrees of end-user B-REDI satisfaction and significant improvements in all measured provider proficiency-level domains. By effectively addressing the readiness decision-making challenges Army BH providers encounter, B-REDI provides the Army BH health care system with a successful blueprint to set the conditions necessary for providers to make more accurate and timely readiness determinations. This may ultimately reduce safety and mission failure risks enterprise-wide, and policymakers should consider formalizing and integrating the B-REDI model into current Army BH practice.

Development of the U.S. Army’s Suicide Prevention Leadership Tool: The Behavioral Health Readiness and Suicide Risk Reduction Review (R4)

Introduction

Although numerous efforts have aimed to reduce suicides in the U.S. Army, completion rates have remained elevated. Army leaders play an important role in supporting soldiers at risk of suicide, but existing suicide-prevention tools tailored to leaders are limited and not empirically validated. The purpose of this article is to describe the process used to develop the Behavioral Health Readiness and Suicide Risk Reduction Review (R4) tools for Army leaders that are currently undergoing empirical validation with two U.S. Army divisions.

Materials and Methods

Consistent with a Secretary of the Army directive, approximately 76 interviews and focus groups were conducted with Army leaders and subject matter experts (SMEs) to obtain feedback regarding existing practices for suicide risk management, leader tools, and institutional considerations. In addition, reviews of the empirical literature regarding predictors of suicide and best practices for the development of practice guidelines were conducted. Qualitative feedback, empirical predictors of suicide, and design considerations were integrated to develop the R4 tools. A second series of 11 interviews and focus groups with Army leaders and SMEs was also conducted to validate the design and obtain feedback regarding the R4 tools.

Results

Leaders described preferences for tool processes (eg, incorporating engaged leadership, including multiple risk identification methods), formatting (eg, one page), organization (eg, low-intermediate-high risk scoring system), content (eg, excluding other considerations related to vehicle safety, including readiness implications), and implementation (eg, accounting for leadership judgment, tailoring process to specific leadership echelons, consideration of institutional barriers). Evidence-based predictors of suicide risk and practice guideline considerations (eg, design) were integrated with leadership feedback to develop the R4 tools that were tailored to specific leadership echelons. Leaders provided positive feedback regarding the R4 tools and described the importance of accounting for potential institutional barriers to implementation. This feedback was addressed by including recommendations regarding the implementation of standardized support meetings between different echelons of leadership.

Conclusions

The R4 development process entailed the simultaneous integration of leadership feedback with evidence-based predictors of suicide risk and design considerations. Thus, the development of these tools builds upon previous Army leadership tools by specifically tailoring elements of those tools to accommodate leader preferences, accounting for potential implementation barriers (eg, institutional factors), and empirically evaluating the implementation of those tools. Future studies should consider utilizing a similar process to develop empirically based resources that are more likely to be incorporated into the routine practice of leaders supporting soldiers at risk of suicide, very often located at the company level and below.

Minor Behavioral Health Readiness and Profiling Barriers in the U.S. Army

INTRODUCTION

Medical readiness for deployment is arguably the most important component of personnel readiness in the U.S. Army. Administrative documents called profiles provide individualized medical recommendations to the commander regarding how to best provide for a soldier's health and welfare, and contribute to an aggregated enumeration of a unit's overall readiness to deploy. Profiles that convey behavioral health (BH) limitations thus reflect what can be called the "behavioral health readiness" of the force. In the Army, BH profiles are further broken into major (more severe BH conditions) and minor (less severe) categories. Recent reporting indicates that current profiling (both major and minor) substantially underestimates BH readiness, presenting a significant safety and personnel issue for the Army. Currently, little is understood regarding barriers to profiling. The intent of this paper is to establish a basis for understanding these barriers by examining provider perceptions on the issue. While the results may have broad applicability in determining BH profiling barriers in general, minor BH improvement efforts stand to benefit the most due to more reliance on provider judgment and less on mandatory guidelines.

MATERIALS AND METHODS

Selected themes and provider quotes regarding barriers to BH profiling from a qualitative study, "Return to Duty Practices of Behavioral Healthcare Providers in Garrison," are presented. Fourteen semi-structured interviews and three focus groups were conducted with a diverse convenience sample of Army BH providers in October 2015, resulting in input from 29 practitioners.

RESULTS

Four general profiling barrier categories were identified and include provider proficiency level, environmental factors, stigma concern, and clinical time constraints.

CONCLUSIONS

Suboptimal BH profiling rates suggest that a preponderance of factors currently tip the scale of BH profiling in a lopsided fashion that comes at the cost of soldier safety and increased risk of mission failure. Relief from one or more of the identified profiling barriers would likely be necessary to tip the scale of clinical judgment in favor of increased profiling, and may be more beneficial for improving minor BH profiling deficits in particular. Quantitative exploration of provider and soldier attitudes on this subject is worthy of further pursuit and would shed light on which of the identified barriers are most crucial to reducing BH profile deficits.

Return to Duty Practices of Army Behavioral Health Providers in Garrison

Introduction

While combat readiness is a top priority for the U.S. Army, there is concern that behavioral health (BH) return to duty (RTD) practices may under-represent the number of soldiers available for deployment. Profiling, the official administrative process by which medical duty limitations are communicated to commanders, was recently found to be significantly under-reporting BH readiness levels in one Army Division. This is a safety issue in addition to a readiness problem, and underscores the importance of better understanding RTD practices in order to offer solutions. This study sought to categorize the information and tools used by Army BH providers in garrison to make decisions about duty limitations that can affect BH readiness.

Materials and Methods

A qualitative approach was used for this study. Fourteen semi-structured interviews and three focus groups were conducted with a diverse convenience sample of Army BH providers in October 2015, resulting in input from 29 practitioners.

Results

Through thematic analysis, it was discovered that profile decisions are driven first by safety of the soldier and secondarily by the needs of the unit. To facilitate their clinical decision-making, providers consider an array of data including standardized scales, unit mission, consultation with unit leadership, meetings with other providers, and, when appropriate, discussion with the friends and family of the soldier.

Conclusions

If the military is to address the concern of under-reporting behavioral health readiness levels in garrison, it is critical to develop more predictability in treatment planning and reporting, as well as access to necessary data to make these clinical decisions. The interviews and focus groups revealed that while the technical process for initiating a profile does not vary, there is great disparity about the amount and type of information that is taken into consideration when making profile decisions. Categorization of the information that supports RTD decisions can lead to a better understanding of the process and inform leadership about ways to improve the accuracy of BH readiness reporting.

Malaria caused by Plasmodium vivax complicated by acalculous cholecystitis

We report the first adult cases of acute acalculous cholecystitis (AAC) exclusively caused by infections with Plasmodium vivax. We reviewed the previous cases of AAC occurring during malaria, compared and contrasted the variables of previously reported cases with the cases reported here, examined the pathogenic link between malaria and AAC, and considered the diagnostic pitfalls and treatment implications as they applied to clinical outcomes in patients with this serious and potentially underrecognized illness.

Sequential production of two different polyesters in the inclusion bodies of Pseudomonas oleovorans

When Pseudomonas oleovorans was grown on a mixture of 5-phenylvaleric acid, PVA, and nonanoic acid, NA, the reserve polyester produced included both a homopolymer and a copolymer. The homopolymer poly-3-hydroxy-5-phenylvalerate, PHPV, contained only 3-hydroxy-5-phenylvalerate units, while the copolymer contained the same long chain 3-hydroxyalkanoates as those present in the copolymer poly-3-hydroxynonanoate, PHN, which is produced from acid alone. The intracellular location of each of these polymers was determined by selective staining of the inclusion body granules with ruthenium tetraoxide and examination by transmission electron microscopy showed that both types of polyesters occurred in the same granule. PHN was present in the center of the granule, while PHPV accumulated around the PHN in the inclusion body. The proteins associated with the inclusion bodies were separated using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). In all cases, two different polymerase enzymes of molecular weight 59 and 55 KDa were present, indicating that the same polymerase enzyme system was responsible for the production of both PHN and PHPV. Attempts were made to produce a random copolymer containing both alkyl and phenylalkyl repeat units by varying the growth conditions, but a mixture of PHN and PHPV was always produced instead.

HLA-class II antigen expression in human heart-lung allografts

Long-term survival in heart-lung transplantation has ben hindered by the development of bronchiolitis obliterans (OB), which is believed to be a manifestation of chronic rejection of the lung. Since HLA-class II antigens are involved in the rejection response, the distribution of the class II products HLA-DR, HLA-DQ, and HLA-DP were studied in normal lung, and in transplanted lung with and without OB, utilizing frozen-section immunohistochemical techniques. All three allelic products are usually expressed on the epithelial, endothelial, and mesenchymal components of the lung. Sequential transbronchial biopsies from 4 recipients before and concurrent with the diagnosis of OB were stained with serial dilutions of monoclonal antibodies to assess the level of expression of the above class II products. Increased levels of HLA-DR and HLA-DP antigens may be seen on the bronchial and bronchiolar epithelium during OB, but the changes are subtle and complicated by many other variables. Additional studies are needed to confirm these preliminary results.