A Pfs48/45-based vaccine to block Plasmodium falciparum transmission: phase 1, open-label, clinical trial.

BACKGROUND: The stalling global progress in malaria control highlights the need for novel tools for malaria elimination, including transmission-blocking vaccines. Transmission-blocking vaccines aim to induce human antibodies that block parasite development in the mosquito and mosquitoes becoming infectious. The Pfs48/45 protein is a leading Plasmodium falciparum transmission-blocking vaccine candidate. The R0.6C fusion protein, consisting of Pfs48/45 domain 3 (6C) and the N-terminal region of P. falciparum glutamate-rich protein (R0), has previously been produced in Lactococcus lactis and elicited functional antibodies in rodents. Here, we assess the safety and transmission-reducing efficacy of R0.6C adsorbed to aluminium hydroxide with and without Matrix-M™ adjuvant in humans. METHODS: In this first-in-human, open-label clinical trial, malaria-naïve adults, aged 18-55 years, were recruited at the Radboudumc in Nijmegen, the Netherlands. Participants received four intramuscular vaccinations on days 0, 28, 56 and 168 with either 30 µg or 100 µg of R0.6C and were randomised for the allocation of one of the two different adjuvant combinations: aluminium hydroxide alone, or aluminium hydroxide combined with Matrix-M1™ adjuvant. Adverse events were recorded from inclusion until 84 days after the fourth vaccination. Anti-R0.6C and anti-6C IgG titres were measured by enzyme-linked immunosorbent assay. Transmission-reducing activity of participants' serum and purified vaccine-specific immunoglobulin G was assessed by standard membrane feeding assays using laboratory-reared Anopheles stephensi mosquitoes and cultured P. falciparum gametocytes. RESULTS: Thirty-one participants completed four vaccinations and were included in the analysis. Administration of all doses was safe and well-tolerated, with one related grade 3 adverse event (transient fever) and no serious adverse events occurring. Anti-R0.6C and anti-6C IgG titres were similar between the 30 and 100 µg R0.6C arms, but higher in Matrix-M1™ arms. Neat participant sera did not induce significant transmission-reducing activity in mosquito feeding experiments, but concentrated vaccine-specific IgGs purified from sera collected two weeks after the fourth vaccination achieved up to 99% transmission-reducing activity. CONCLUSIONS: R0.6C/aluminium hydroxide with or without Matrix-M1™ is safe, immunogenic and induces functional Pfs48/45-specific transmission-blocking antibodies, albeit at insufficient serum concentrations to result in transmission reduction by neat serum. Future work should focus on identifying alternative vaccine formulations or regimens that enhance functional antibody responses. TRIAL REGISTRATION: The trial is registered with ClinicalTrials.gov under identifier NCT04862416.

Gestational and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin primes cortical microglia to tissue injury.

Recent studies have shown that the aryl hydrocarbon receptor (AhR) is expressed in the brain's native immune cells, known as microglia. However, while the impact of exposure to AhR ligands is well studied in the peripheral immune system, the impact of such exposure on immune function in the brain is less well defined. Microglia serve dual roles in providing synaptic and immunological support for neighboring neurons and in mediating responses to environmental stimuli, including exposure to environmental chemicals. Because of their dual roles in regulating physiological and pathological processes, cortical microglia are well positioned to translate toxic stimuli into defects in cortical function via aberrant synaptic and immunological functioning, mediated either through direct microglial AhR activation or in response to AhR activation in neighboring cells. Here, we use gene expression studies, histology, and two-photon in vivo imaging to investigate how developmental exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a high-affinity and persistent AhR agonist, modulates microglial characteristics and function in the intact brain. Whole cortical RT-qPCR analysis and RNA-sequencing of isolated microglia revealed that gestational and lactational TCDD exposure produced subtle, but durable, changes in microglia transcripts. Histological examination and two-photon in vivo imaging revealed that while microglia density, distribution, morphology, and motility were unaffected by TCDD exposure, exposure resulted in microglia that responded more robustly to focal tissue injury. However, this effect was rectified with depletion and repopulation of microglia. These results suggest that gestational and lactational exposure to AhR ligands can result in long-term priming of microglia to produce heightened responses towards tissue injury which can be restored to normal function through microglial repopulation.

Imaging nanoparticle-algae interactions in three dimensions using Cytoviva microscopy.

Plasmonic resonances of metal-based nanoparticles are increasingly used for ultrasensitive imaging assays. In this context, the Cytoviva(TM) microscopy platform has greatly gained in popularity. In essence, Cytoviva is an optimized dark field microscope that permits detection of particles down to a few nanometers in size. A significant limitation of Cytoviva up to now has been that it only provided for single plane imaging. The datasets produced by this technique therefore only show a partial view of the sample - not ideally suited to analysis. Here we explain how to overcome this limitation by mounting the Cytoviva condenser on an automated microscope with Z-scanning capability. Our method allows three-dimensional mapping of nanoparticles in their full three-dimensional cellular context. We apply this technique to study the interaction of silver and cerium dioxide nanoparticles with cells of the green alga, Pseudokirchneriella subcapitata, a system of significant environmental relevance because algae underlie much of the aquatic food chain. Our objective was to develop a technique to visualize in detail the interaction of nanoparticles with cells in three dimensions, such that one may, for example, determine whether a particular nanoparticle is inside a cell, at its very surface, or at a distance from it.

Yoga in adult cancer: a pilot survey of attitudes and beliefs among oncologists.

BACKGROUND: Depending on interest, knowledge, and skills, oncologists are adapting clinical behaviour to include integrative approaches, supporting patients to make informed complementary care decisions. The present study sought to improve the knowledge base in three ways: Test the acceptability of a self-reported online survey for oncologists.Provide preliminary data collection concerning knowledge, attitudes, beliefs, and current referral practices among oncologists with respect to yoga in adult cancer.List the perceived benefits of and barriers to yoga intervention from a clinical perspective. METHODS: A 38-item self-report questionnaire was administered online to medical, radiation, and surgical oncologists in British Columbia. RESULTS: Some of the 29 oncologists who completed the survey (n = 10) reported having recommended yoga to patients to improve physical activity, fatigue, stress, insomnia, and muscle or joint stiffness. Other responding oncologists were hesitant or unlikely to suggest yoga for their patients because they had no knowledge of yoga as a therapy (n = 15) or believed that scientific evidence to support its use is lacking (n = 11). All 29 respondents would recommend that their patients participate in a clinical trial to test the efficacy of yoga. In qualitative findings, oncologists compared yoga with exercise and suggested that it might have similar psychological and physical health benefits that would improve patient capacity to endure treatment. Barriers to and limitations of yoga in adult cancer are also discussed. CONCLUSIONS: An online self-report survey is feasible, but has response rate limitations. A small number of oncologists are currently recommending yoga to improve health-related outcomes in adult cancer. Respondents would support clinical yoga interventions to improve the evidence base in cancer patients, including men and women in all tumour groups.

Adeno-associated virus-RNAi of GlyRα1 and characterization of its synapse-specific inhibition in OFF alpha transient retinal ganglion cells.

In the central nervous system, inhibition shapes neuronal excitation. In spinal cord glycinergic inhibition predominates, whereas GABAergic inhibition predominates in the brain. The retina uses GABA and glycine in approximately equal proportions. Glycinergic crossover inhibition, initiated in the On retinal pathway, controls glutamate release from presynaptic OFF cone bipolar cells (CBCs) and directly shapes temporal response properties of OFF retinal ganglion cells (RGCs). In the retina, four glycine receptor (GlyR) α-subunit isoforms are expressed in different sublaminae and their synaptic currents differ in decay kinetics. GlyRα1, expressed in both On and Off sublaminae of the inner plexiform layer, could be the glycinergic isoform that mediates On-to-Off crossover inhibition. However, subunit-selective glycine contributions remain unknown because we lack selective antagonists or cell class-specific subunit knockouts. To examine the role of GlyRα1 in direct inhibition in mature RGCs, we used retrogradely transported adeno-associated virus (AAV) that performed RNAi and eliminated almost all glycinergic spontaneous and visually evoked responses in PV5 (OFFα(Transient)) RGCs. Comparisons of responses in PV5 RGCs infected with AAV-scrambled-short hairpin RNA (shRNA) or AAV-Glra1-shRNA confirm a role for GlyRα1 in crossover inhibition in cone-driven circuits. Our results also define a role for direct GlyRα1 inhibition in setting the resting membrane potential of PV5 RGCs. The absence of GlyRα1 input unmasked a serial and a direct feedforward GABA(A)ergic modulation in PV5 RGCs, reflecting a complex interaction between glycinergic and GABA(A)ergic inhibition.

The combination of anti-NKG2D and CTLA-4 Ig therapy prolongs islet allograft survival in a murine model.

Islet transplantation is an effective means of treating severe type 1 diabetes in patients with life-threatening hypoglycemia. Improvements in glycemic control with correction of HbA1C enhance quality of life irrespective of insulin independence. By antagonizing the Natural Killer Group 2, member D (NKG2D) receptor expression on NK and CD8+ T cells, in combination with blocking CTLA-4 binding sites, we demonstrate a significant delay of graft rejection in islet allotransplant. Anti-NKG2D combined with CTLA-4 Ig (n = 15) results in prolonged allograft survival, with 84.6 ± 10% of the recipients displaying insulin independence compared to controls (n = 10, p < 0.001). The effect of combination therapy on graft survival is superior to treatments alone (CTLA-4 Ig vs. combination p = 0.024, anti-NKG2D vs. combination p < 0.001) indicating an interaction between these pathways. In addition, combination treatment also improves glucose tolerance when compared to controls (n = 10, p = 0.018). Histologically, NKG2D+ cells were significantly decreased within the allograft after 7 days of combination treatment (n = 6, p = 0.029). T cell proliferation was significantly reduced with anti-NKG2D therapy and CD8+ T cell daughter fractions were also significantly decreased with mAb and combination treatment when measured by in vitro mixed lymphocyte reaction (n = 5, p = 0.015, p = 0.005 and p = 0.048). These results demonstrate that inhibition of NKG2D receptors and costimulatory pathways enhance islet allograft survival.

The trans-sphincteric posterior sagittal repair of recto-urinary and recto-vaginal fistulae using Surgisis™ mesh and fibrin sealant.

Recto-urinary, recto-vaginal and ileo-anal pouch-associated fistulae are rare yet a significant clinical problem due to their profound impact on patients' quality of life and are a challenge to repair. In this report, we describe repair of these complex fistulae using a modified trans-sphincteric posterior sagittal approach with Surgisis™ mesh and fibrin sealant and review our repair outcomes.

Baseline TGF-ß correlates with protection after immunization with Plasmodium falciparum sporozoites in the controlled human malaria infection model.

BACKGROUND: Here we assessed a possible relationship between baseline TGF-ß concentrations and acquisition of sterile immunity after Plasmodium falciparum sporozoite immunization. METHODS: TGF-ß concentrations were determined in samples of 65 malaria-naive volunteers in 4 studies either prior to and after challenge infection, or prior to and after first immunizing infection under chemoprophylaxis with P. falciparum sporozoites. RESULTS: High baseline TGF-ß concentrations were associated with rapid acquisition of sterile protection (p = 0.028). CONCLUSION: Baseline TGF-ß concentrations predict the efficiency of acquisition of sterile immunity following sporozoite immunization and may represent a steady-state regulatory mechanism to keep in check immune systems with a low threshold for activation.

Different patterns of Toll-like receptor 2 polymorphisms in populations of various ethnic and geographic origins.

Upon the invasion of the host by microorganisms, innate immunity is triggered through pathogen recognition by pattern recognition receptors (PRRs). Toll-like receptors (TLRs) are the best-studied class of PRRs, and they recognize specific pathogen-associated molecular patterns (PAMPs) from various microorganisms. A large number of studies have shown that genetic variation in TLRs may influence susceptibility to infections. We assessed the genetic variation of TLR2, which encodes one of the most important TLRs, in various populations around the globe and correlated it with changes in the function of the molecule. The three best-known nonsynonymous TLR2 polymorphisms (1892C>A, 2029C>T, and 2258G>A) were assessed in different populations from the main continental masses: Romanians, Vlax-Roma, Dutch (European populations), Han Chinese (East Asia), Dogon, Fulani (Africa), and Trio Indians (America). The 2029C>T polymorphism was absent in both European and non-European populations, with the exception of the Vlax-Roma, suggesting that this polymorphism most likely arose in Indo-Aryan people after migration into South Asia. The 1892C>A polymorphism that was found exclusively in European populations, but not in Asian, African, or American volunteers, probably occurred in proto-Indo-Europeans. Interestingly, 2258G>A was present only in Europeans, including Vlax-Roma, but at a very low frequency. The differential pattern of the TLR2 polymorphisms in various populations may explain some of the differences in susceptibility to infections between these populations.

Anakinra potentiates the protective effects of etanercept in transplantation of marginal mass human islets in immunodeficient mice.

Anti-inflammatory agents are used routinely in clinical islet transplantation in an attempt to promote islet engraftment. Infliximab, and more recently etanercept, is being used to neutralize tumor necrosis factor alpha, but this tenet is based on limited preclinical data. One group has promoted the potential of combined etanercept with an IL-1 receptor antagonist, anakinra in a small clinical study, but without strong preclinical data to justify this approach. We therefore sought to evaluate the impact of combined anakinra and etanercept in a marginal islet mass transplant model using human islets in immunodeficient mice. The combination of anakinra and etanercept led to remarkable improvement in islet engraftment (control 36.4%; anakinra 53.9%; etanercept 45.45%; anakinra and etanercept 87.5% euglycemia, p < 0.05 by log-rank) compared to single-drug treated mice or controls. This translated into enhanced metabolic function (area under curve glucose tolerance), improved graft insulin content and marked reduction in beta-cell specific apoptotis (0.67% anakinra + etanercept vs. 23.5% control, p < 0.001). These results therefore strongly justify the combined short-term use of anakinra and etanercept in human islet transplantation.

Micro RNA expression profiles as adjunctive data to assess the risk of hepatocellular carcinoma recurrence after liver transplantation.

Donor livers are precious resources and it is, therefore, ethically imperative that we employ optimally sensitive and specific transplant selection criteria. Current selection criteria, the Milan criteria, for liver transplant candidates with hepatocellular carcinoma (HCC) are primarily based on radiographic characteristics of the tumor. Although the Milan criteria result in reasonably high survival and low-recurrence rates, they do not assess an individual patient's tumor biology and recurrence risk. Consequently, it is difficult to predict on an individual basis the risk for recurrent disease. To address this, we employed microarray profiling of microRNA (miRNA) expression from formalin fixed paraffin embedded tissues to define a biomarker that distinguishes between patients with and without HCC recurrence after liver transplant. In our cohort of 64 patients, this biomarker outperforms the Milan criteria in that it identifies patients outside of Milan who did not have recurrent disease and patients within Milan who had recurrence. We also describe a method to account for multifocal tumors in biomarker signature discovery.

Sporozoite motility as a quantitative readout for anti-CSP antibody inhibition.

Antibodies can prevent malaria by neutralizing the infectious Plasmodium falciparum sporozoites (SPZ) before they establish an infection in the liver. Circumsporozoite protein (CSP), the most abundant surface protein of SPZ is the leading candidate for passive (and subunit) immunization approaches against malaria. Comprehensive assessment of the parasite-inhibitory capacity of anti-CSP monoclonal antibodies (mAbs) is an important step in advancing CSP-based immunization strategies. In this study, we employed a quantitative imaging-based motility assay to quantify the effect of anti-CSP mAbs on SPZ motility, both in vitro and in human skin.Our assay provided a quantitative measure of mAb parasite-inhibitory capacity through measurement of the half-maximal motility inhibitory concentration (IC50M) value for anti-CSP mAbs (IC50M 2A10: 24 nM, IC50M 3SP2: 71 nM). We found a sevenfold discrepancy between the IC50M and the binding saturation concentration measured by ELISA, possibly related to the observed shedding of CSP-mAb complexes during SPZ movement. In a subset of SPZ (5%), in vitro motility was unaffected by the presence of 2A10 while 3SP2 was able to completely block movement. In our ex vivo skin explant model, SPZ proved less susceptible to anti-CSP mAbs compared to SPZ in an in vitro environment. By quantitatively assessing motility, we created a valuable tool that can be used for comprehensive assessment of anti-CSP mAb potency. Insight that will help deepen our understanding of anti-CSP mAb potency and guide selection of the most promising anti-CSP mAbs for downstream clinical development.

The Effectiveness of Traditional Chinese Medicine (TCM) as an Adjunct Treatment on Stable COPD Patients: A Systematic Review and Meta-Analysis.

BACKGROUND: Traditional Chinese medicine (TCM), including Chinese herbal medicine (CHM) and acupuncture, exhibits beneficial effects on stable chronic obstructive pulmonary disease (COPD) such as improving lung function and reducing exacerbation. Previous research studies have examined either CHM or acupuncture alone, which are not the usual practice in TCM clinic setting. We conduct a systematic review for evaluating the clinical effectiveness and safety of TCM by combining CHM and acupuncture. METHODS: Databases are searched from inception to November 2019. Randomized controlled trials examining either acupuncture or CHM on stable COPD are included. Primary outcomes include lung functions, exacerbations, and COPD assessment test. Secondary outcomes include quality of life, TCM syndrome score and effective rate, and 6-minute walk distance. Two independent reviewers extract data and assess the quality of evidence and generate meta-analysis and risk of bias by STATA. This protocol follows the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) guidelines. RESULTS: 100 randomized controlled trials (8291 participants) were included to compare add-on Chinese medicine treatment with conventional treatment (CT). Combining CHM with CT improves FEV1 (MD: 0.18, 95% CI: 0.08, 0.28), exacerbation rate (MD: -0.29, 95% CI: -0.61, 0.03), COPD assessment test (MD: -2.16, 95% CI: -3.44, -0.88), TCM syndrome score (MD: -3.96, 95% CI: -5.41, -2.51) and effective rate (RR: 0.89, 95% CI: 0.80, 0.93), and 6-minute walk test (MD: 37.81, 95% CI: 20.90, 54.73). No serious adverse events were reported. Risk of bias: low to unclear. CONCLUSIONS: This review identifies sufficient moderate-to-low-quality evidence to suggest TCM as an adjunct treatment for stable COPD patients. Though heterogeneity was low among studies, the results were limited and the quality of evidence was low or very low based on small sample sizes and risk of bias. Future studies with larger sample sizes are warranted. The trial is registered with CRD42019161324.

Acute 2,3,7,8-Tetrachlorodibenzo-p-dioxin exposure in adult mice does not alter the morphology or inflammatory response of cortical microglia.

Microglia, the immune cells of the brain, have a canonical role in regulating responses to neurological disease or injury, but have also recently been implicated as regulators of neurophysiological processes such as learning and memory. Given these dual immune and physiological roles, microglia are a likely mechanism by which external toxic stimuli are converted into deficits in neuronal circuitry and subsequently function. However, while it is well established that exposure to environmental toxicants negatively affects the peripheral immune system, it remains unknown whether and how such exposure causes neuroinflammation which, in turn, may negatively impact microglial functions in vivo. Here, we examined how acute 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure in adulthood, which negatively impacts immune cells in the periphery, affects microglial characteristics in the cortex of the mouse. We found that microglia density, distribution, morphology, inflammatory signaling, and response to a secondary, pathological activation were unaffected by acute TCDD exposure. These results suggest that acute, peripheral TCDD exposure in adulthood is not sufficient to induce an overt inflammatory phenotype in cortical microglia.

[Development of vaccines against malaria; progress with contributions from the Netherlands]. / Ontwikkeling van vaccins tegen malaria.

Five years ago, the very first malaria vaccine, RTS,S/AS01, received a positive evaluation by the European Medicines Agency. Although this vaccine does not achieve the WHO's target of 75% protection, it does set the standard for all new vaccine candidates. In this article, we describe the progress made in the development of several second-generation malaria vaccines, an area where Dutch research has made major contributions. These include vaccines with live, attenuated Plasmodium falciparumsporozoites and transmission-blocking vaccines. Thanks in part to Dutch contributions, the development of vaccines against malaria has recently made significant progress on the way to the finish line: a vaccine that provides protection to the most vulnerable population - young children in Africa.

Opioid-prescribing patterns, storage, handling, and disposal in postoperative pediatric urology patients.

BACKGROUND: Emerging research on surgeons and the opioid epidemic have focused on the adult population. Consequently, little is known regarding opioid-prescribing practices in the pediatric population. The goal of this study is to examine postoperative opioid-prescribing and consumption patterns, as well as storage and disposal trends for specific pediatric urologic procedures. STUDY DESIGN: Patients undergoing surgery associated with specified Current Procedural Terminology codes were retrospectively identified, and details regarding opioid medications were obtained through our pharmacy database. Patients' guardians were contacted two weeks postoperatively to determine opioid usage. Opioids were prescribed at a standard dosing of 0.1 mg/kg per dose or the equivalent. RESULTS: Of the 171 identified patients, 117 patients were successfully contacted, with 67 (39%) completing telephone surveys. The 3 most common pediatric urology procedures were inguinal hernia repair (N = 39), circumcision (N = 27), and cystoscopy (N = 16). Across all procedures, there was an average excess of 9.8 doses prescribed, corresponding to an overprescription rate of 64%. Of the patients prescribed opioids, 41 (62%) had leftover opioid medication two weeks postoperatively. Thirty-two of 41 (78%) patients did not dispose of their leftover medication. Only 13 patients received perioperative counseling on appropriate storage and disposal of opiates. DISCUSSION: Prescribing practices for an array of pediatric urologic procedures are non-standardized and often generously excessive. We show universal overprescribing for all our reviewed urologic procedures. Sixty-two percent of pediatric urology patients did not use their entire prescribed opiate, leaving a significant pool of medicine within the pediatric family home. Given the low incidence of perioperative education, unsurprisingly a majority of our patients improperly handled and disposed off excess opioid medication. CONCLUSION: There is general overprescription of postoperative opioids and poor perioperative opioid education in the pediatric urology population.

A decrease of plasma macrophage migration inhibitory factor concentration is associated with lower numbers of circulating lymphocytes in experimental Plasmodium falciparum malaria.

Macrophage migration inhibitory factor (MIF) has recently been implicated in the pathogenesis of malarial anaemia. However, field studies have reported contradictory results on circulating MIF concentrations in patients with clinically overt Plasmodium falciparum malaria. We determined plasma MIF levels over time in 10 healthy volunteers during experimental P. falciparum infection. Under fully controlled conditions, MIF levels decreased significantly during early blood-stage infection and reached a nadir at day 8 post-infection. A decrease in the number of circulating lymphocytes, which are an important source of MIF production, paralleled the decrease in MIF levels. Monocyte/macrophage counts remained unchanged. At MIF nadir, the anti-inflammatory cytokine interleukin (IL)-10, which is an inhibitor of T-cell MIF production, was detectable in only 2 of 10 volunteers. Plasma concentrations of the pro-inflammatory cytokines IL-8 and IL-1beta were only marginally elevated. We conclude that circulating MIF levels decrease early in blood-stage malaria as a result of the decline in circulating lymphocytes.

Effect of mass of 111In-benzyl-EDTA monoclonal antibody on hepatic uptake and processing in mice.

In patients, the pharmacokinetic behavior of murine monoclonal antibodies has been observed to vary with the amount of antibody administered. It has been suggested that this reflects human recognition of the foreign mouse protein. We have found that the amount of antibody administered also influenced pharmacokinetic behavior when murine monoclonal antibody was administered to mice. p-Isothiocyanatobenzyl-EDTA, a new chelator which forms complexes with 111In that are stable in vivo, was conjugated to Lym-1, a murine anti-Burkitt's lymphoma monoclonal antibody. The pharmacokinetics of two doses (20 and 0.2 micrograms) of the 111In labeled radiopharmaceutical were studied in non-tumor bearing BALB/c mice. About 20% (0.04 microgram) of the 0.2-microgram dose, compared with 8% (1.6 micrograms) of the 20-micrograms dose, was found in the liver at 48 h after injection. Both doses demonstrated a biological half-life of approximately 120 h. At least 75% of the 111In was excreted by the kidneys, and essentially all 111In in the urine remained chelated by the EDTA portion of p-isothiocyanatobenzyl-EDTA. From these observations of a dose dependent uptake of this radiopharmaceutical by the liver we conclude that there is a recognition phenomenon in mice for this murine monoclonal antibody.

Development of humoral immune responses against a macrocyclic chelating agent (DOTA) in cancer patients receiving radioimmunoconjugates for imaging and therapy.

The development of stable immunoconjugates by the advent of macrocyclic metal chelating agents (DOTA) has enabled us to study the ability of 111In-DOTA-labeled monoclonal antibodies to detect tumor lesions in a pilot radioimmunolocalization study, as well as to evaluate the kinetics, toxicity, and efficacy of i.p. administered 90Y-DOTA-labeled murine monoclonal antibody in a Phase I/II clinical trial of advanced ovarian cancer. The development of serum sickness-like reactions in three of six treated patients, in the absence of previous monoclonal antibody administration, led us to study the potential immunogenicity of the new chelate. Six patients with ovarian cancer received 25 mg of HMFG1 monoclonal antibody coupled with 90Y-DOTA (doses of radioactivity, 15 to 25 mCi), administered i.p. Eight patients with various malignant tumors received low doses (220 micrograms to 1 mg) of monoclonal antibodies, labeled with 111In-DOTA, i.v. for imaging studies. Using a solid-phase enzyme-linked immunosorbent assay method, the immunogenicity of DOTA was evaluated. Serial dilutions of patients' sera, before and after imaging or therapy with DOTA-coupled monoclonal antibodies, as well as sera from patients who did not receive DOTA-coupled antibody, were screened on enzyme-linked immunosorbent assay plates coated with human serum albumin (HSA), HSA-2-iminothiolane, and HSA-2-iminothiolane-benzyl-DOTA. All patients treated with i.p. monoclonal antibody developed anti-DOTA antibodies. Four of eight patients who received i.v. "imaging" doses of DOTA-coupled monoclonal antibody developed antibodies against DOTA. The levels of anti-DOTA response correlated with the amount of injected radioimmunoconjugate (r = 0.889, P less than 0.001). None of the patients who received DOTA-coupled antibody had detectable antibodies against the macrocycle before immunoconjugate administration. We then addressed further the restriction of the immune response against the macrocycle. We found that there was no or very low response against the aromatic ring attached to DOTA. Most, if not all, of the immune response is directed against the DOTA ring structure. Affinity purification of anti-DOTA antibody from serum enabled quantitation of these antibodies in the serum of patients. An inverse, statistically significant correlation was observed between the percentage of binding inhibition of a patient's serum to DOTA, by HSA-2-iminothiolane-DOTA (100 micrograms/ml) and the level of anti-DOTA immunoglobulin in the serum.(ABSTRACT TRUNCATED AT 400 WORDS)