Risk of Gastroenteritis from Swimming at a Wastewater-Impacted Tropical Beach Varies across Localized Scales

Population growth and changing climate are expected to increase human exposure to pathogens in tropical coastal waters. We examined microbiological water quality in three rivers within 2.3 km of each other that impact a Costa Rican beach and in the ocean outside their plumes during the rainy and dry seasons. We performed quantitative microbial risk assessment (QMRA) to predict the risk of gastroenteritis associated with swimming and the amount of pathogen reduction needed to achieve safe conditions. Recreational water quality criteria based on enterococci were exceeded in >90% of river samples but in only 13% of ocean samples. Multivariate analysis grouped microbial observations by subwatershed and season in river samples but only by subwatershed in the ocean. The modeled median risk from all pathogens in river samples was between 0.345 and 0.577, 10-fold above the U.S. Environmental Protection Agency (U.S. EPA) benchmark of 0.036 (36 illnesses/1,000 swimmers). Norovirus genogroup I (NoVGI) contributed most to risk, but adenoviruses raised risk above the threshold in the two most urban subwatersheds. The risk was greater in the dry compared to the rainy season, due largely to the greater frequency of NoVGI detection (100% versus 41%). Viral log10 reduction needed to ensure safe swimming conditions varied by subwatershed and season and was greatest in the dry season (3.8 to 4.1 dry; 2.7 to 3.2 rainy). QMRA that accounts for seasonal and local variability of water quality contributes to understanding the complex influences of hydrology, land use, and environment on human health risk in tropical coastal areas and can contribute to improved beach management. IMPORTANCE This holistic investigation of sanitary water quality at a Costa Rican beach assessed microbial source tracking (MST) marker genes, pathogens, and indicators of sewage. Such studies are still rare in tropical climates. Quantitative microbial risk assessment (QMRA) found that rivers impacting the beach consistently exceeded the U.S. EPA risk threshold for gastroenteritis of 36/1,000 swimmers. The study improves upon many QMRA studies by measuring specific pathogens, rather than relying on surrogates (indicator organisms or MST markers) or estimating pathogen concentrations from the literature. By analyzing microbial levels and estimating the risk of gastrointestinal illness in each river, we were able to discern differences in pathogen levels and human health risks even though all rivers were highly polluted by wastewater and were located less than 2.5 km from one another. This variability on a localized scale has not, to our knowledge, previously been demonstrated.

Distributions of waterborne pathogens in raw wastewater based on a 14-month, multi-site monitoring campaign

The California State Water Resources Control Board is the first regulatory body in the United States to develop statewide regulations for direct potable reuse (DPR). To support this effort, a pathogen monitoring campaign was undertaken to develop and implement an optimized standard operating protocol to better characterize the concentration of human pathogens in raw wastewater. Methods to detect relevant viral and protozoan pathogens in raw wastewater were optimized and implemented during a 14-month monitoring campaign. Over 120 samples were collected from five wastewater treatment plants treating a quarter of California's population. Samples were analyzed for two protozoa (Cryptosporidium and Giardia) using microscopy methods, three enteric viruses (enterovirus, adenovirus, and norovirus) using culture and/or molecular methods, and male-specific coliphage using culture methods. The method recovery efficiency was measured in every protozoa sample and every other virus sample to confirm minimum recovery efficiencies were achieved and to correct the concentrations for pathogen losses during sample processing. The results from this study provide the industry with a large, high-quality dataset as demonstrated by the high degree of method sensitivity, method recovery, and QA/QC steps. Such high-quality data on pathogen concentrations in raw wastewater are critical for confirming the level of treatment needed to reduce pathogen concentrations down to acceptable levels for potable water in DPR projects.

Reproducibility and sensitivity of 36 methods to quantify the SARS-CoV-2 genetic signal in raw wastewater: findings from an interlaboratory methods evaluation in the U.S

In response to COVID-19, the international water community rapidly developed methods to quantify the SARS-CoV-2 genetic signal in untreated wastewater. Wastewater surveillance using such methods has the potential to complement clinical testing in assessing community health. This interlaboratory assessment evaluated the reproducibility and sensitivity of 36 standard operating procedures (SOPs), divided into eight method groups based on sample concentration approach and whether solids were removed. Two raw wastewater samples were collected in August 2020, amended with a matrix spike (betacoronavirus OC43), and distributed to 32 laboratories across the U.S. Replicate samples analyzed in accordance with the project's quality assurance plan showed high reproducibility across the 36 SOPs: 80% of the recovery-corrected results fell within a band of ±1.15 log10 genome copies per L with higher reproducibility observed within a single SOP (standard deviation of 0.13 log10). The inclusion of a solids removal step and the selection of a concentration method did not show a clear, systematic impact on the recovery-corrected results. Other methodological variations (e.g., pasteurization, primer set selection, and use of RT-qPCR or RT-dPCR platforms) generally resulted in small differences compared to other sources of variability. These findings suggest that a variety of methods are capable of producing reproducible results, though the same SOP or laboratory should be selected to track SARS-CoV-2 trends at a given facility. The methods showed a 7 log10 range of recovery efficiency and limit of detection highlighting the importance of recovery correction and the need to consider method sensitivity when selecting methods for wastewater surveillance.

Reproducibility and sensitivity of 36 methods to quantify the SARS-CoV-2 genetic signal in raw wastewater: findings from an interlaboratory methods evaluation in the U.S

In response to COVID-19, the international water community rapidly developed methods to quantify the SARS-CoV-2 genetic signal in untreated wastewater. Wastewater surveillance using such methods has the potential to complement clinical testing in assessing community health. This interlaboratory assessment evaluated the reproducibility and sensitivity of 36 standard operating procedures (SOPs), divided into eight method groups based on sample concentration approach and whether solids were removed. Two raw wastewater samples were collected in August 2020, amended with a matrix spike (betacoronavirus OC43), and distributed to 32 laboratories across the U.S. Replicate samples analyzed in accordance with the project's quality assurance plan showed high reproducibility across the 36 SOPs: 80% of the recovery-corrected results fell within a band of ±1.15 log₁₀ genome copies per L with higher reproducibility observed within a single SOP (standard deviation of 0.13 log₁₀). The inclusion of a solids removal step and the selection of a concentration method did not show a clear, systematic impact on the recovery-corrected results. Other methodological variations (e.g., pasteurization, primer set selection, and use of RT-qPCR or RT-dPCR platforms) generally resulted in small differences compared to other sources of variability. These findings suggest that a variety of methods are capable of producing reproducible results, though the same SOP or laboratory should be selected to track SARS-CoV-2 trends at a given facility. The methods showed a 7 log₁₀ range of recovery efficiency and limit of detection highlighting the importance of recovery correction and the need to consider method sensitivity when selecting methods for wastewater surveillance.

Relationships among microbial indicators of fecal pollution, microbial source tracking markers, and pathogens in Costa Rican coastal waters

Tropical coastal waters are understudied, despite their ecological and economic importance. They also reflect projected climate change scenarios for other climate zones, e.g., increased rainfall and water temperatures. We conducted an exploratory microbial water quality study at a tropical beach influenced by sewage-contaminated rivers, and tested the hypothesis that fecal microorganisms (fecal coliforms, enterococci, Clostridium perfringens, somatic and male-specific coliphages, pepper mild mottle virus (PMMoV), Bacteroides HF183, norovirus genogroup I (NoVGI), Salmonella, Cryptosporidium and Giardia) would vary by season and tidal stage. Most microorganisms' concentrations were greater in the rainy season; however, NoVGI was only detected in the dry season and Cryptosporidium was the only pathogen most frequently detected in rainy season. Fecal indicator bacteria (FIB) levels exceeded recreational water quality criteria standards in >85% of river samples and in <50% of ocean samples, regardless of the FIB or regulatory criterion. Chronic sewage contamination was demonstrated by detection of HF183 and PMMoV in 100% of river samples, and in >89% of ocean samples. Giardia, Cryptosporidium, Salmonella, and NoVGI were frequently detected in rivers (39%, 39%, 26%, and 39% of samples, respectively), but infrequently in ocean water, particularly during the dry season. Multivariate analysis showed that C. perfringens, somatic coliphage, male-specific coliphage, and PMMoV were the subset of indicators that maximized the correlation with pathogens in the rivers. In the ocean, the best subset of indicators was enterococci, male-specific coliphage, and PMMoV. We also executed redudancy analyses on environmental parameters and microorganim concentrations, and found that rainfall best predicted microbial concentrations. The seasonal interplay of rainfall and pathogen prevalence undoubtedly influences beach users' health risks. Relationships are likely to be complex, with some risk factors increasing and others decreasing each season. Future use of multivariate approaches to better understand linkages among environmental conditions, microbial predictors (fecal indicators and MST markers), and pathogens will improve prediction of high-risk scenarios at recreational beaches.

Assessment of Drinking Water Sold from Private Sector Kiosks in Post-Earthquake Port-au-Prince, Haiti

Consumption of drinking water from private vendors has increased considerably in Port-au-Prince, Haiti, in recent decades. A major type of vendor is private kiosks, advertising reverse osmosis-treated water for sale by volume. To describe the scale and geographical distribution of private kiosks in metropolitan Port-au-Prince, an inventory of private kiosks was conducted from July to August 2013. Coordinates of kiosks were recorded with global positioning system units and a brief questionnaire was administered with the operator to document key kiosk characteristics. To assess the quality of water originating from private kiosks, water quality analyses were also conducted on a sample of those inventoried as well as from the major provider company sites. The parameters tested were Escherichia coli, free chlorine residual, pH, turbidity, and total dissolved solids. More than 1,300 kiosks were inventoried, the majority of which were franchises of four large provider companies. Approximately half of kiosks reported opening within 12 months of the date of the inventory. The kiosk treatment chain and sales price was consistent among a majority of the kiosks. Of the 757 kiosks sampled for water quality, 90.9% of samples met World Health Organization (WHO) microbiological guideline at the point of sale for nondetectable E. coli in a 100-mL sample. Of the eight provider company sites tested, all samples met the WHO microbiological guideline. Because of the increasing role of the private sector in drinking water provision in Port-au-Prince and elsewhere in Haiti, this assessment was an important first step for government regulation of this sector.

The first association of a primary amebic meningoencephalitis death with culturable Naegleria fowleri in tap water from a US treated public drinking water system

BACKGROUND

Naegleria fowleri is a climate-sensitive, thermophilic ameba found in warm, freshwater lakes and rivers. Primary amebic meningoencephalitis (PAM), which is almost universally fatal, occurs when N. fowleri-containing water enters the nose, typically during swimming, and migrates to the brain via the olfactory nerve. In August 2013, a 4-year-old boy died of meningoencephalitis of unknown etiology in a Louisiana hospital.

METHODS

Clinical and environmental testing and a case investigation were initiated to determine the cause of death and to identify potential exposures.

RESULTS

Based on testing of cerebrospinal fluid and brain specimens, the child was diagnosed with PAM. His only reported water exposure was tap water; in particular, tap water that was used to supply water to a lawn water slide on which the child had played extensively prior to becoming ill. Water samples were collected from both the home and the water distribution system that supplied the home and tested; N. fowleri was identified in water samples from both the home and the water distribution system.

CONCLUSIONS

This case is the first reported PAM death associated with culturable N. fowleri in tap water from a US treated drinking water system. This case occurred in the context of an expanding geographic range for PAM beyond southern states, with recent case reports from Minnesota, Kansas, and Indiana. This case also highlights the role of adequate disinfection throughout drinking water distribution systems and the importance of maintaining vigilance when operating drinking water systems using source waters with elevated temperatures.

Recovery of diverse microbes in high turbidity surface water samples using dead-end ultrafiltration

Dead-end ultrafiltration (DEUF) has been reported to be a simple, field-deployable technique for recovering bacteria, viruses, and parasites from large-volume water samples for water quality testing and waterborne disease investigations. While DEUF has been reported for application to water samples having relatively low turbidity, little information is available regarding recovery efficiencies for this technique when applied to sampling turbid water samples such as those commonly found in lakes and rivers. This study evaluated the effectiveness of a DEUF technique for recovering MS2 bacteriophage, enterococci, Escherichia coli, Clostridium perfringens, and Cryptosporidium parvum oocysts in surface water samples having elevated turbidity. Average recovery efficiencies for each study microbe across all turbidity ranges were: MS2 (66%), C. parvum (49%), enterococci (85%), E. coli (81%), and C. perfringens (63%). The recovery efficiencies for MS2 and C. perfringens exhibited an inversely proportional relationship with turbidity, however no significant differences in recovery were observed for C. parvum, enterococci, or E. coli. Although ultrafilter clogging was observed, the DEUF method was able to process 100-L surface water samples at each turbidity level within 60 min. This study supports the use of the DEUF method for recovering a wide array of microbes in large-volume surface water samples having medium to high turbidity.

Primary amebic meningoencephalitis deaths associated with sinus irrigation using contaminated tap water

BACKGROUND

Naegleria fowleri is a climate-sensitive, thermophilic ameba found in the environment, including warm, freshwater lakes and rivers. Primary amebic meningoencephalitis (PAM), which is almost universally fatal, occurs when N. fowleri-containing water enters the nose, typically during swimming, and N. fowleri migrates to the brain via the olfactory nerve. In 2011, 2 adults died in Louisiana hospitals of infectious meningoencephalitis after brief illnesses.

METHODS

Clinical and environmental testing and case investigations were initiated to determine the cause of death and to identify the exposures.

RESULTS

Both patients had diagnoses of PAM. Their only reported water exposures were tap water used for household activities, including regular sinus irrigation with neti pots. Water samples, tap swab samples, and neti pots were collected from both households and tested; N. fowleri were identified in water samples from both homes.

CONCLUSIONS

These are the first reported PAM cases in the United States associated with the presence of N. fowleri in household plumbing served by treated municipal water supplies and the first reports of PAM potentially associated with the use of a nasal irrigation device. These cases occurred in the context of an expanding geographic range for PAM beyond southern tier states with recent case reports from Minnesota, Kansas, and Virginia. These infections introduce an additional consideration for physicians recommending nasal irrigation and demonstrate the importance of using appropriate water (distilled, boiled, filtered) for nasal irrigation. Furthermore, the changing epidemiology of PAM highlights the importance of raising awareness about this disease among physicians treating persons showing meningitislike symptoms.

Standard and alternative methods of stretcher carriage: performance, human factors, and cardiorespiratory responses

Transporting a casualty on a stretcher is a common task for medical and military personnel. Stretchers are usually carried by hand, but distributing the load to other parts of the body may have advantages. To examine alternative carriage methods, 11 soldiers walked on a treadmill at 4.8 km/h while performing two-person carries of a stretcher containing an 80-kg manikin. In separate trials, soldiers carried the stretcher using: (1) hand carriage, (2) shoulder straps, (3) a specially designed harness that allowed load shifting between the hips and shoulders (hip-shoulder system), and (4) a clip that fitted on the belt of standard military load carrying equipment (LCE) and placed the stretcher mass mainly on the hips. With each system, subjects walked until volitional fatigue or 30 min. While walking, expired gases and heart rates were obtained and subjects rated their perceived exertion (Borg Scale). At the conclusion of all four trials, subjects rated each system on a number of subjective measures. Results showed that average (+/- SD) carriage times were 2.7+/-1.4, 14.5+/-8.3, 25.4+/-8.1, and 21.7+/-9.9 min with the hand, shoulder, hip-shoulder and LCE systems respectively (p<0.01). Hand carriage resulted in considerably more cardiorespiratory stress (higher heart rate and minute ventilation, p<0.05) than the other three systems, but there were few consistent differences among the other three systems. Perceived exertion in the upper body was less with the hip-shoulder and LCE systems than with the other two systems (p<0.05). Subjects preferred the hip-shoulder and LCE systems overall and for specific subjective characteristics such as comfort, ease of use and stability (p<0.01). These data indicate that moving the stretcher load from the hands and placing that load on the shoulders and/or hips results in improved performance, reduced cardiorespiratory stress and favourable subjective evaluations. Further developmental work should focus on the hip-shoulder and LCE systems.

Hepatocyte gene therapy in a large animal: a neonatal bovine model of citrullinemia

The development of gene-replacement therapy for inborn errors of metabolism has been hindered by the limited number of suitable large-animal models of these diseases and by inadequate methods of assessing the efficacy of treatment. Such methods should provide sensitive detection of expression in vivo and should be unaffected by concurrent pharmacologic and dietary regimens. We present the results of studies in a neonatal bovine model of citrullinemia, an inborn error of urea-cycle metabolism characterized by deficiency of argininosuccinate synthetase and consequent life-threatening hyperammonemia. Measurements of the flux of nitrogen from orally administered 15NH4 to [15N]urea were used to determine urea-cycle activity in vivo. In control animals, these isotopic measurements proved to be unaffected by pharmacologic treatments. Systemic administration of a first-generation E1-deleted adenoviral vector expressing human argininosuccinate synthetase resulted in transduction of hepatocytes and partial correction of the enzyme defect. The isotopic method showed significant restoration of urea synthesis. Moreover, the calves showed clinical improvement and normalization of plasma glutamine levels after treatment. The results show the clinical efficacy of treating a large-animal model of an inborn error of hepatocyte metabolism in conjunction with a method for sensitively measuring correction in vivo. These studies will be applicable to human trials of the treatment of this disorder and other related urea-cycle disorders.

Anticipation and execution of a simple reading task enhance corticospinal excitability

OBJECTIVE

Electromyographic responses (EMG) evoked in the right hand by transcranial magnetic stimulation (TMS) of the left motor cortex are enhanced during continuous reading. This enhancement is the result of increased excitability of the motor cortex. We proposed that anticipation and reading of single words would also enhance corticospinal excitability. We studied the temporal course of corticospinal excitability changes following left and right hemisphere TMS.

METHODS

Ten normal volunteers were studied. A warning stimulus (S1) was followed by an imperative stimulus (S2) whereupon a word was presented. Subjects responded by reading the word aloud or reading it silently. In other conditions, no word was displayed and the subjects responded to S2 by saying the word 'Cat', pursing their lips, or doing nothing. EMG was recorded over the contralateral hand following a TMS pulse over the motor cortex during and after the S1-S2 period.

RESULTS

Enhancement of EMG amplitudes was significantly greater following left hemisphere TMS. The enhancement in the S1-S2 period and that following S2 had a time course similar to several event-related brain potentials.

CONCLUSIONS

There may be a common mechanism underlying both corticospinal excitability and the contingent negative variation, readiness potential and N400.

Toxicological comparison of E2a-deleted and first-generation adenoviral vectors expressing alpha1-antitrypsin after systemic delivery

Second-generation adenoviral vectors, mutated in E2a, have been proposed to decrease host immune responses against transduced cells, reduce toxicity, and increase duration of expression as compared with first-generation vectors deleted only in E1. To test these hypotheses further, we have developed an E2a-deleted adenoviral vector expressing human alpha1-antitrypsin (hAAT). Toxicity of first-generation and E2a-deleted vectors, as determined by hematological indices, liver function tests, and histological analyses, was evaluated in C3H mice for 21 days after vector administration at increasing doses starting at 1 x 10(12) particles/kg. Both vectors induced dose-dependent abnormalities including transient thrombocytopenia, elevated ALT levels in serum, and increased hepatocyte proliferation followed by inflammation and then hypertrophy. Differences in the ratio of particles to plaque-forming units among vector preparations led to differences in hAAT expression at similar particle doses. There were no differences in toxicity between the two vectors when measured at matching levels of hAAT expression. However, the E2a-deleted vector was demonstrated to have slightly reduced hepatocyte toxicity at an intermediate particle dose. This suggests that hepatocyte toxicity is related primarily to viral entry and expression, rather than to the presence of noninfectious particles, and implies that vectors with complete elimination of viral gene expression, such as vectors with all viral coding sequences deleted, are likely to have substantial advantages in terms of safety and toxicity.

Increased excitability of the human corticospinal system with hyperventilation

OBJECTIVES

Hyperventilation is effective in inducing generalized spike-wave discharges in patients with absence seizures and improves visual function and normalizes visual function in patients with multiple sclerosis. Hyperventilation increases the excitability of cutaneous and motor axons. In experimental animals, hyperventilation increases excitability of hippocampal neurons. There is however no direct evidence of a hyperventilation-induced increase in neuronal excitability within the central nervous system in humans. In this study we determined the effects of hyperventilation on the human corticospinal system.

METHODS

We studied the effects of hyperventilation on (1) motor evoked potentials (MEPs) induced by transcranial magnetic pulse stimulation of the motor cortex and (2) F-wave responses. Six subjects were studied.

RESULTS

Hyperventilation resulting in an end-tidal pCO2 of 15 mm Hg or less enhanced the amplitude of the MEP and resulted in a shortened onset latency. F-wave amplitudes were enhanced without any change in onset latency.

CONCLUSIONS

These findings indicate that hyperventilation increases the excitability of the human corticospinal system. A hyperventilation-induced increase in excitability within the central nervous system may account for clinical phenomena such as facilitation of spike-wave discharges.

Evaluation of gene therapy for citrullinaemia using murine and bovine models

Citrullinaemia is an autosomal recessive disorder caused by the deficiency of argininosuccinate synthase. The deficiency of this enzyme results in an interruption in the urea cycle and the inability to dispose of excess ammonia derived from the metabolism of protein. The only treatment for this disorder has been dietary restriction of protein and supplementation with medications allowing for alternative excretion of excess nitrogen. Gene therapy offers the possibility of a long-term cure for disorders like citrullinaemia by expressing the deficient gene in the target organ. We have explored the use of adenoviral vectors as a treatment modality for citrullinaemia in two animal models, a naturally occurring bovine model and a murine model created by molecular mutagenesis. Mice treated with adenoviral vectors expressing argininosuccinate synthase lived significantly longer than untreated animals (11 days vs 1 day; however, the animals did not exhibit normal weight gain during the experiment, indicating that the therapeutic effectiveness of the transducing virus was suboptimal. It is speculated that part of the failure to observe better clinical outcome might be due to the deficiency of arginine. In the bovine model, the use of adenoviral vectors did not result in any change in the clinical condition of the animals or in the level of plasma ammonia. However, the use of 15N isotopic ammonia allowed us to assess the flux of nitrogen through the urea cycle during the experiment. These studies revealed a significant increase in the flux through the urea cycle following administration of adenoviral vectors expressing argininosuccinate synthase. We conclude that the use of adenoviral vectors in the treatment of citrullinaemia is a viable approach to therapy but that it will be necessary to increase the level of transduction and to increase the level of enzyme produced from the recombinant viral vector. Future experiments will be designed to address these issues.

Recombinant human interleukin-3 to dose-intensify carboplatin and cyclophosphamide chemotherapy in epithelial ovarian cancer: a phase I trial

PURPOSE

To define the optimal dose of recombinant human interleukin-3 (rhIL-3) required to intensify the dose of carboplatin and cyclophosphamide for advanced epithelial ovarian cancer.

PATIENTS AND METHODS

Seventeen patients were treated on day 1 with carboplatin (dose adjusted for creatinine clearance: range, 257 to 385 mg/m2; median, 300 mg/m2) and cyclophosphamide (750 mg/m2). rhIL-3 5 micrograms/kg/d (n = 10) or 10 micrograms/kg/d (n = 7) was administered subcutaneously (SC) on days 2 through 11. Carboplatin dose was escalated if no postponement of cycles 1 to 3 had occurred.

RESULTS

A 3-week interval was achieved in 62% of cycles and a 4-week interval in 81%, with no difference between the rhIL-3 doses. A neutrophil nadir less than 0.5 x 10(9)/L occurred in 35% of the cycles at 5 micrograms/kg/d and in 52% at 10 micrograms/kg/d of rhIL-3 (nonsignificant difference). The mean platelet nadir in cycle 1 was 173 +/- 78 x 10(9)/L at 5 micrograms/kg/d and 340 +/- 152 x 10(9)/L at 10 micrograms/kg/d of rhIL-3 (P < .05), with a faster recovery of platelets at 10 micrograms/kg/d (P < .05). Progressive myelotoxicity occurred for leukocytes and platelets at both rhIL-3 doses and required chemotherapy postponement in later cycles. The planned six cycles were completed by 41% of patients. Fever (> or = 38.5 degrees C) occurred in 38% of cycles at 5 micrograms/kg/d and in 97% at 10 micrograms/kg/d (P < .0005); headache and myalgias occurred in 30% and 44%, respectively. After two cycles, diffuse erythema, facial edema, and urticaria were observed in two patients at 5 micrograms/kg/d and in five patients at 10 micrograms/kg/d of rhIL-3. This resolved after discontinuation of rhIL-3 and administration of corticosteroids and antihistamines.

CONCLUSION

A dose of 5 micrograms/kg/d of rhIL-3 proved to be optimal to intensify the carboplatin and cyclophosphamide regimen. It permitted the administration of carboplatin and cyclophosphamide combination therapy every 3 weeks in 62% of cycles.

Successful treatment of metastatic renal cell carcinoma with a biologically active dose of recombinant interferon-gamma

We tested the clinical efficacy of a biologically active dose (BAD) of interferon (IFN)-gamma for treatment of progressive renal cell carcinoma (RCC). Twenty-two RCC patients with disease progression subsequent to nephrectomy were entered on a phase II clinical trial. During an initial dose-finding phase, biochemical responses to repeated once-weekly subcutaneous injections of 10, 100, or 500 micrograms of recombinant IFN-gamma were tested in 16 patients. Results indicated that 100 micrograms IFN-gamma applied once weekly was biologically active with induction of serum beta 2-microglobulin and neopterin. Such a dose induced a nearly maximum response of both markers lasting more than 4 days. This dose was also associated with minimal side effects. A dose of 100 micrograms IFN-gamma given once weekly was, therefore, subsequently given weekly for long-term treatment. During a median time of therapy of 10 months (range, 2 to 32 months) two complete (CR; 20+, 20+ months) and four partial tumor responses (PR; 6+, 7+, 8+, 24+ months) were seen (30% CR plus PR; 95% confidence limits, 12% to 54%) among 20 patients evaluable for response. Patients with refractory disease had significantly lower IFN-gamma-induced increments of serum beta 2-microglobulin than those who achieved clinical remission or stable disease.

In-vitro and in-vivo studies on the induction of neopterin biosynthesis by cytokines, alloantigens and lipopolysaccharide (LPS)

Recently we presented evidence that cellular immune responses are associated with increased in-vitro and in-vivo excretion of neopterin (Huber et al., 1983) and that, in vitro at least, macrophages and IFN-gamma play a key role in the induction of this phenomenon (Huber et al., 1984). Although this marker is increasingly applied for monitoring of human disease, there is limited knowledge about the mechanism(s) responsible for its increased biosynthesis during inflammatory states. To further elucidate this question we evaluated neopterin and IFN-levels in culture supernatants of human blood cells and in patients' sera. Cells or patients were exposed to a panel of recombinant cytokines, alloantigens or lipopolysaccharide. To investigate indirect stimulation by induction of production of endogenous IFNs, the impact of neutralization of IFNs by addition of specific antibodies was also studied. The data confirm our previous results which identified the monocyte/macrophage as the main producer cell among human blood cells. They further demonstrate that, at least in vitro, IFN-gamma, IFN-alpha and LPS can all stimulate neopterin release independently from each other. Thirdly, they indicate that stimuli such as alloantigens or TNF-alpha can indirectly enhance neopterin release by their capacity to induce production of endogenous IFN-gamma. On the basis of these data we conclude that enhanced neopterin biosynthesis does not necessarily relate to activation of T cells but can also be caused by non-immune stimuli.

Enhanced serum levels of beta-2-microglobulin, neopterin, and interferon-gamma in patients treated with recombinant tumor necrosis factor-alpha

The effect of different doses of recombinant human tumor necrosis factor-alpha (rTNF-alpha) on serum levels of neopterin, beta-2-microglobulin and interferon-gamma (IFN-gamma) was investigated in tumor patients. Twelve patients with advanced malignant disease were treated and received single doses of either 1, 10, or 100 micrograms/m2 rTNF-alpha on days 0 and 7. Neopterin, beta-2-microglobulin and IFN-gamma serum levels were measured from day -2 to day 12 of the study. Application of rTNF-alpha leads to a marked and dose-dependent increase of neopterin and beta-2-microglobulin levels; no rTNF-alpha-dependent changes were observed after 1 microgram/m2, and maximum increments were seen in patients receiving 100 micrograms/m2. Serum levels of both parameters peaked after 2 days and returned to baseline values within 1 week. IFN-gamma levels were also elevated after application of rTNF-alpha. We failed, however, to demonstrate a clear correlation between the serum levels of IFN-gamma, beta-2-microglobulin, and neopterin because of the wide range of pre- and posttreatment levels of IFN-gamma. We conclude that neopterin and beta-2-microglobulin represent useful markers for monitoring biological response to treatment with rTNF-alpha.