Incidence of Lyme Borreliosis in Germany: Exploring Observed Trends Over Time Using Public Surveillance Data, 2016-2020

Background: Public surveillance of Lyme borreliosis (LB) occurs in 9 out of 16 federal states of Germany and remains a critical facet of disease epidemiology and trends. We describe the incidence, time trends, seasonality, and geographic distribution of LB in Germany using publicly reported surveillance data. Methods: We obtained LB cases and incidence (2016-2020) from the online platform SurvStat@RKI 2.0, maintained by the Robert Koch Institute (RKI). Data included clinically diagnosed and laboratory-confirmed LB reported by nine out of 16 federal states of Germany where LB notification is mandatory. Results: During 2016-2020, the nine federal states reported 63,940 LB cases, of which 60,570 (94.7%) were clinically diagnosed, and 3370 (5.3%) also had laboratory confirmation, with an average of 12,789 cases annually. Incidence rates were mostly stable over time. The average annual LB incidence was 37.2/100,000 person-years and varied by spatial level, ranging from 22.9 to 64.6/100,000 person-years among nine states; from 16.8 to 85.6/100,000 person-years among 19 regions; and from 2.9 to 172.8/100,000 person-years among 158 counties. Incidence was lowest among persons 20-24 years old (16.1/100,000 person-years) and highest among those 65-69 years old (60.9/100,000 person-years). Most cases were reported between June and September, with a peak in July of every year. Conclusion: The risk of LB varied substantially at the smallest geographic unit and by age group. Our results underscore the importance of presenting LB data at the most spatially granular unit and by age to allow implementation of efficient preventive interventions and reduction strategies.

Evaluation of under-testing and under-diagnosis of tick-borne encephalitis in Germany

BACKGROUND

Tick-borne encephalitis (TBE), a viral infectious disease affecting the central nervous system, potentially resulting in prolonged neurological symptoms and other long-term sequelae. Case identification can be challenging as TBE can be associated with non-specific symptoms, and even in cases consistent with typical TBE symptoms, the rate of laboratory testing to confirm cases is unknown. This study assessed real-world TBE laboratory testing rates across Germany.

METHODS

In this retrospective cross-sectional study, physicians provided data on TBE decision-making, laboratory testing (serological), and diagnostics behavior via in-depth qualitative interviews (N = 12) or a web-based quantitative survey of their patient medical records (N = 166). Hospital-based physicians who specialized in infectious disease, intensive care unit, emergency room, neurology, or pediatrics with experience managing and ordering testing for patients with meningitis, encephalitis, or non-specific central nervous system symptoms in the past 12 months were included. Data were summarized via descriptive statistics. TBE testing and positivity rates were assessed for the aggregate sample of 1400 patient charts and reported by presenting symptoms, region, and tick bite exposure.

RESULTS

TBE testing rates ranged from 54.0% (non-specific neurological symptoms only) to 65.6% (encephalitis symptoms only); the percentage of TBE positive results ranged from 5.3% (non-specific neurological symptoms only) to 36.9% (meningitis symptoms only). TBE testing rates were higher among those with a tick bite history and/or who presented with headache, high fever, or flu-like symptoms.

CONCLUSIONS

The findings of this study suggest that patients with typical TBE symptoms are likely under-tested, thus likely leading to under-diagnosis in Germany. To ensure appropriate case identification, TBE testing should be consistently integrated into routine practice for all patients who present with relevant symptoms or exposure to common risk factors.

1361. Lyme Borreliosis (LB) is a Significant Disease Burden in Germany: Estimated LB Incidence after Adjusting for Under-ascertainment by Public Health Surveillance, 2021

Background

Lyme borreliosis (LB), the most common tickborne disease in Europe, is endemic in Germany. Nine German states (with 42% of the German population) conduct LB surveillance with mandatory notification by clinicians and laboratories but an analysis of outpatient claims estimated that only one of every six LB cases in these states were reported. We estimated the LB incidence after adjusting for under-ascertainment of public health surveillance.

Methods

Nationally representative studies estimated the prevalence of antibodies against Borrelia burgdorferi sensu lato in adults and children in Germany. Published estimates of the asymptomatic proportion and the duration of antibody detection were used to estimate the number of LB cases from seroprevalence data in states that conduct LB surveillance. The number of estimated LB cases were compared to the number of surveillance-reported cases to derive under-ascertainment multipliers for adults and children. The derived multipliers were applied to the number of reported cases in 2021 to estimate the number and incidence of LB cases in the states that conducted surveillance in 2021. A sensitivity analysis evaluated the impact of different antibody durations.

Results

Using a 50% asymptomatic proportion and 10-year antibody duration, the estimated number (population-based incidence) of LB cases in states that conducted surveillance was 128,870 (408/100,000) in 2021. Since there were 11,051 reported cases in these states, these data indicate there were 12 LB cases in 2021 for every reported case in these states. Using 20-year or 5-year antibody duration, the estimated number (incidence) of LB cases in the states that conducted surveillance was 64,935 – 259,740 (204 - 816/100,000) in 2021, respectively.

Conclusion

Incidence of LB in states that conduct surveillance in Germany is higher than reported. Under-ascertainment of LB cases in states that conduct surveillance is even greater than that estimated in a claims data analysis of medically-attended LB cases. Enhancements of LB surveillance, including expanding nationwide, would facilitate further elucidation of the true LB disease burden in Germany. Disease prevention efforts, including availability of an efficacious vaccine, are needed to address this important public health problem.

Disclosures

Julia Olsen, BS, Pfizer: Employee Gordon Brestrich, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds Andreas Pilz, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds|Pfizer: Stocks/Bonds Kate Halsby, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds Patrick Kelly, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds Claudius Malerczyk, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds Frederick Angulo, DVM PhD, Pfizer: Employee|Pfizer: Stocks/Bonds James H. Stark, PhD, Pfizer: Employee|Pfizer: Stocks/Bonds.

Can risk area designation help increase vaccination coverage for Tick-Borne Encephalitis? Evidence from German claims data

BACKGROUND AND OBJECTIVES

Although vaccine preventable, the incidence of tick-borne encephalitis (TBE) increased in Germany from 2001 to 2021 by on average 2% each year, with a peak of more than 700 TBE infections documented in 2020. TBE-risk areas, as designated by district based on incidence of human cases, expanded north- and northeastward, present in 11 of the 16 Federal States as of 2022. Using claims data from a German statutory health insurance in the Federal States of Saxony and Thuringia (AOK PLUS), we aimed to assess whether official assignment of a district to a risk area had an impact on vaccination rates in Germany.

METHODS

The data covered the period from 01/01/2010 to 31/12/2018 and included information on vaccine administrations from outpatient physicians. Yearly incident vaccination rates were reported overall and by district. To investigate the association between a new designation of an incident TBE-risk area and vaccination rates, a difference-in-difference analysis was conducted.

RESULTS

Overall, the incident vaccination rates increased from 6.2 to 9.5 per 1,000 person-years between 2012 and 2018, with a peak of 12.2 in 2015. While districts that had been risk-areas for the whole study period had always a higher vaccination rate compared to districts that were never categorized as risk areas, the increase between 2012 and 2018 was comparable in the two groups (3.0 and 3.2 per 1,000 person-years, respectively). In contrast, districts that were newly designated risk districts during the study period experienced a significantly larger increase in vaccination rates, going from 5.8 to 14.7 per 1,000 person-years between 2012 and 2018, with a peak of 19.6 in 2015.

CONCLUSION

The results suggest that the new designation of a district as risk area has a significant positive impact on vaccination rates, which is strongest immediately after designation of risk area.

Ticks on the turf: investigating the presence of ixodid ticks on and around football fields in Germany

Ixodes ricinus is the most abundant tick species and an important vector of pathogens in Germany and in large parts of Europe. A few other ixodid tick species, e.g., Dermacentor reticulatus, may also be of eco-epidemiological relevance. As ticks are not only found in natural but also in suburban areas (parks, gardens), the present study investigated whether ticks occur on and near football grounds thus posing a potential risk to players and visitors. Thirty-two football grounds from all 16 German federal states were selected, mainly situated adjacent to a green area (forest, park). Ticks were collected by the conventional flagging method in spring 2018, and nymphs and adults were counted and morphologically determined. Altogether 807 nymphal and adult ticks were collected from 29 football grounds: 714 I. ricinus, 64 Ixodes inopinatus, 2 Ixodes frontalis, 24 Ixodes sp. ticks, and 3 D. reticulatus. Ixodes inopinatus was found in 13 out of 16 German states. Three ticks were even found on the turf of two football fields. It can be concluded that ticks occur quite frequently and sometimes in high abundance near football grounds situated close or adjacent to a forest or a park.

Vaccination rate and adherence of tick-borne encephalitis vaccination in Germany

BACKGROUND

Tick-borne encephalitis (TBE) is an arboviral infection of the central nervous system. As there is no causal treatment of TBE, disease prevention by vaccination is especially important. Immunization consists of a three-dose primary vaccination schedule, followed by regular booster doses. In Germany, the Standing Committee on Vaccination (STIKO) at the Robert Koch-Institute recommends TBE vaccination for all those at high risk of contracting TBE. This includes individuals living in, traveling to and/or working in risk areas, and being exposed to ticks. To our knowledge, there are currently no reliable data on TBE vaccination rates in Germany available.

METHODS

This retrospective cohort study based on anonymized German health claims data was conducted to determine vaccination rates of TBE primary immunization in 2012 to 2015 by federal state, compliance with the vaccination schedule, and TBE vaccination uptake for the 2011 birth cohort. Vaccination protection rates for each federal state were simulated based on a compartmental model.

RESULTS

Vaccination rates of an initiated primary immunization ranged from about 3% in the southern federal states to <1% in the northern federal states. Across all federal states, compliance with the vaccination schedule decreased with each subsequent vaccination. Slightly higher TBE vaccination uptake was determined in the 2011 birth cohort, as compared to the German school entry health examination statistics in 2017. Simulated vaccination protection rates for each federal state ranged from 10% in Hamburg to 51% in Baden-Wuerttemberg.

CONCLUSIONS

While there was an overall low vaccination uptake and a discrepancy between areas of high vs. low TBE risk, this study also indicates a concerning decline in vaccination compliance. Vaccinating physicians should address the importance of adherence upon initiation of TBE vaccination.

Comparison of the immunogenicity and safety of the purified chick embryo cell rabies vaccine manufactured in India and Germany: A randomized, single blind, multicentre, phase IV clinical study

This phase IV, single blind study assessed the immunogenicity and safety of India-manufactured purified chick embryo cell rabies vaccine (PCECV), compared with a German-manufactured batch obtained by the same production process. A total of 340 participants enrolled at 2 study sites in India were randomized (1:1:1:1) in 4 groups to receive a 5-dose Essen regimen with either 1 of the 3 Indian batches (PCECV-I) or the German batch (PCECV-G), administered on Days (D) 0, 3, 7, 14 and 30. The lot-to-lot consistency of PCECV-I batches in terms of induced immune response at D14 was demonstrated. The immune response elicited by PCECV-I was shown to be non-inferior to that induced by PCECV-G, as the lower limit of the 95% confidence interval for the ratio (PCECV-I/PCECV-G) of rabies virus neutralising antibody (RVNA) geometric mean concentrations was higher than 0.5 at D14. At least 96% of participants developed adequate RVNA concentrations (≥ 0.5 IU/mL) by D14 and all achieved RVNA concentrations ≥ 0.5 IU/mL by D90. RVNA levels were comparable across all groups throughout the entire study. Solicited local and general symptoms had a similar incidence in all groups. Unsolicited adverse events (AEs) were reported by 11% of participants. Only 1 serious AE (leg fracture) was reported and was not related to vaccination. No deaths and no rabies cases were recorded during the 90 days of observation. The study showed that the 3 PCECV-I and the PCECV-G batches induced a similar immune response and had a comparable safety profile when administered according to a 5-dose schedule.

A randomized open-labeled study to demonstrate the non-inferiority of purified chick-embryo cell rabies vaccine administered in the Zagreb regimen (2-1-1) compared with the Essen regimen in Chinese adults

The Zagreb regimen has been used for 20 years in various countries. In China, until 2010, the Zagreb schedule was only approved for purified chick embryo cell vaccine (PCECV) and purified Vero cell rabies vaccines (PVRV). In this phase III clinical trial, we aimed to demonstrate the safety and immunogenic non-inferiority of the Zagreb regimen compared with the Essen regimen in healthy adult Chinese immunized with PCECV (Rabipur®). The study enrolled 825 subjects aged 18 to 50 years; serum samples were collected on Days 0, 7, 14, 42, and at 13 months to assess rabies virus neutralizing antibody (RVNA) concentrations. Solicited and unsolicited local and systemic reactions were recorded for 6 days following the day of vaccination, and collected throughout the entire study period (Day 1 until Month 13). The Zagreb regimen was non-inferior to the Essen regimen with regard to RVNA concentrations after 7, 14, and 42 days, and 13 months of immunization. The non-inferiority of seroconversion was established at Days 14 and 42. The incidence of local and systemic reactions was similar between groups, and mostly of mild or moderate severity. Vaccine-related adverse events occurred more frequently in the Essen group than in the Zagreb group. Vaccination with PCECV under a 2-1-1 regimen is as safe and immunogenic as under the traditional 5-dose Essen regimen for rabies post-exposure prophylaxis, and is a more cost-effective option, has a more practical vaccination schedule, and can potentially increase compliance.

Cross-neutralization of antibodies induced by vaccination with Purified Chick Embryo Cell Vaccine (PCECV) against different Lyssavirus species

Background: Rabies is a neglected zoonotic disease caused by viruses belonging to the genus lyssavirus. In endemic countries of Asia and Africa, where the majority of the estimated 60,000 human rabies deaths occur, it is mainly caused by the classical rabies virus (RABV) transmitted by dogs. Over the last decade new species within the genus lyssavirus have been identified. Meanwhile 15 (proposed or classified) species exist, including Australian bat lyssavirus (ABLV), European bat lyssavirus (EBLV-1 and -2), Duvenhage virus (DUVV), as well as Lagos bat virus (LBV) and Mokola virus (MOKV) and recently identified novel species like Bokeloh bat lyssavirus (BBLV), Ikoma bat lyssavirus (IKOV) or Lleida bat lyssavirus (LLBV). The majority of these lyssavirus species are found in bat reservoirs and some have caused human infection and deaths. Previous work has demonstrated that Purified Chick Embryo Cell Rabies Vaccine (PCECV) not only induces immune responses against classical RABV, but also elicits cross-neutralizing antibodies against ABLV, EBLV-1 and EBLV-2.

Material & Methods: Using the same serum samples as in our previous study, this study extension investigated cross-neutralizing activities of serum antibodies measured by rapid fluorescent focus inhibition test (RFFIT) against selected other non-classical lyssavirus species of interest, namely DUVV and BBLV, as well as MOKV and LBV.

Results: Antibodies developed after vaccination with PCECV have neutralizing capability against BBLV and DUVV in the same range as against ABLV and EBLV-1 and -2. As expected, for the phylogenetically more distant species LBV no cross-neutralizing activity was found. Interestingly, 15 of 94 serum samples (16%) with a positive neutralizing antibody titer against RABV displayed specific cross-neutralizing activity (65-fold lower than against RABV) against one specific MOKV strain (Ethiopia isolate), which was not seen against a different strain (Nigeria isolate).

Conclusion: Cross-neutralizing activities partly correlate with the phylogenetic distance of the virus species. Cross-neutralizing activities against the species BBLV and DUVV of phylogroup 1 were demonstrated, in line with previous results of cross-neutralizing activities against ABLV and EBLV-1 and -2. Potential partial cross-neutralizing activities against more distant lyssavirus species like selected MOKV strains need further research.

Rabies pre-exposure vaccination of children with purified chick embryo cell vaccine (PCECV)

Human rabies, mainly transmitted by dog bites, remains a major public health problem in developing countries. In Asian countries, such as India or the Philippines, where large free-ranging dog populations exist, the human death toll stays high. Children under the age of 15 y are at particular risk, representing up to half of the dog bite victims. While pre-exposure prophylaxis (PrEP) is commonly used in travelers from developed countries visiting areas of high endemicity, rabies vaccination is rarely used in highly endemic countries in contrast to post-exposure prophylaxis (PEP). Purified Chick Embryo Cell Vaccine (PCECV, Rabipur®/RabAvert®, Novartis Vaccines and Diagnostics) is approved for pre- and post-exposure prophylaxis, either by the intramuscular route, or--where registered--by the intradermal route of administration. In more than 25 y of use, PCECV has been widely used for PrEP in children. This review summarizes the pediatric pre-exposure clinical trials using PCECV. In total, PCECV has been administered to more than 1,200 children in clinical trials, from toddlers to those in elementary school, using intramuscular and intradermal schedules, demonstrating safety and immunogenicity. PrEP as part of routine pediatric vaccination programs may have a major role to play in human rabies prevention. Extensive clinical experience with PCECV supports intramuscular and intradermal PrEP in children as one pillar of human rabies prevention in developing countries.

Immunogenicity of Simulated PCECV Postexposure Booster Doses 1, 3, and 5 Years after 2-Dose and 3-Dose Primary Rabies Vaccination in Schoolchildren

Objectives. To assess the immunogenicity of intradermal (ID) booster doses of Purified Chick Embryo Cell rabies vaccine (PCECV, Rabipur) administered to Thai schoolchildren one, three and five years after a primary ID pre-exposure (PrEP) vaccination series. Methods. In this follow-up study of a randomized, open-label, phase II clinical trial, two simulated post-exposure booster doses of PCECV were administered on days 0 and 3 intradermally to 703 healthy schoolchildren, one, three or five years after primary vaccination with either two or three ID doses of 0.1 mL PCECV. Blood was drawn immediately before and 7, 14 and 365 days after the first booster dose to determine rabies virus neutralizing antibody (RVNA) concentrations. Results. An anamnestic response of approximately 30-fold increase in RVNA concentrations was demonstrated within 14 days after booster. All children (100%) developed adequate RVNA concentrations above 0.5 IU/mL. No vaccine related serious adverse events were seen in any of the vaccinees. Conclusion. ID rabies PrEP with PCECV is safe and immunogenic in schoolchildren and the anamnestic response to a two booster dose vaccination series was found to be adequate one, three, and five years after a two- or three-dose primary PrEP vaccination series.

Antibodies induced by vaccination with purified chick embryo cell culture vaccine (PCECV) cross-neutralize non-classical bat lyssavirus strains

Tissue-culture vaccines like purified chick embryo cell vaccine (PCECV) have been shown to provide protection against classical rabies virus (RABV) via pre-exposure or post-exposure prophylaxis. A cross-neutralization study was conducted using a panel of 100 human sera, to determine, to what extent after vaccination with PCECV protection exists against non-classical bat lyssavirus strains like European bat lyssavirus (EBLV) type 1 and 2 and Australian bat lyssavirus (ABLV). Virus neutralizing antibody (VNA) concentrations against the rabies virus variants CVS-11, ABLV, EBLV-1 and EBLV-2 were determined by using a modified rapid fluorescent focus inhibition test. For ABLV and EBLV-2, the comparison to CVS-11 revealed almost identical results (100% adequate VNA concentrations >or=0.5 IU/mL; correlation coefficient r(2)=0.69 and 0.77, respectively), while for EBLV-1 more scattering was observed (97% adequate VNA concentrations; r(2)=0.50). In conclusion, vaccination with PCECV produces adequate VNA concentrations against classical RABV as well as non-classical lyssavirus strains ABLV, EBLV-1, and EBLV-2.

Pre-exposure rabies vaccination using purified chick embryo cell rabies vaccine intradermally is immunogenic and safe

OBJECTIVE

To demonstrate the safety and immunogenicity of intradermal rabies pre-exposure prophylaxis with purified chick embryo cell vaccine (PCECV) in schoolchildren age 5 to 8 years in Thailand.

STUDY DESIGN

In a randomized, open-label, phase II clinical trial, 2 or 3 intradermal doses of 0.1 mL PCECV (Rabipur) were administered to 703 schoolchildren on days 0 and 28 or on days 0, 7, and 28. In 206 children, 2 simulated post-exposure booster doses were given 1 year after the primary vaccination series. Rabies virus- neutralizing antibody (RVNA) titers were determined by the rapid fluorescent focus inhibition test.

RESULTS

In school-age children in Thailand, a pre-exposure immunization regimen of 3 intradermal doses of PCECV produced adequate immune responses. After primary vaccination, all subjects developed RVNA titers > or =0.5 IU/mL and demonstrated a rapid increase in RVNA titer after 2 simulated post-exposure booster immunizations 1 year after the primary vaccination series. No serious adverse drug reactions occurred.

CONCLUSIONS

Rabies pre-exposure immunization with PCECV is safe and immunogenic, and its implementation could save the lives of many children in rabies-endemic areas.

Rabies post-exposure prophylaxis vaccination with purified chick embryo cell vaccine (PCECV) and purified vero cell rabies vaccine (PVRV) in a four-site intradermal schedule (4-0-2-0-1-1): An immunogenic, cost-effective and practical regimen

Currently, two intradermal (ID) regimens for rabies post-exposure prophylaxis (PEP) are recommended by WHO and used in countries where approved by national authorities: the Thai Red Cross (TRC) two-site ID regimen and the eight-site ID regimen. Besides these WHO recommended schedules, a new economical four-site ID regimen was evaluated that reduces the cost of PEP by up to 80%, when compared with the standard intramuscular Essen regimen, reduces the number of visits required for the patients when compared with the TRC regimen, and is more convenient than the eight-site regimen. To determine the immunogenicity of the ID four-site PEP regimen (4-0-2-0-1-1), 180 healthy volunteers were randomized to receive 0.1 mL volumes of PCECV or PVRV administered ID over both left and right shoulders and both deltoid regions on day 0, both deltoid regions on day 7 and over one deltoid region on days 30 and 90. Regardless of the vaccine, every subject developed rabies virus neutralizing antibody (RVNA) titers above 0.5 IU/mL by day 14, as determined by rapid fluorescent focus inhibition test (RFFIT) using a homologous test system. Two weeks after the last dose of vaccine, RVNA titers were all above 0.5 IU/mL (day 104). Geometric mean titers were similar throughout the study period. Both vaccines were well tolerated. These results demonstrate that a new four-site ID PEP regimen is a cost-effective and convenient alternative to IM (Essen or Zagreb) or ID (TRC or eight-site) regimens, especially using a 1 mL vial of vaccine (PCECV).

Potency requirements of rabies vaccines administered intradermally using the Thai Red Cross regimen: investigation of the immunogenicity of serially diluted purified chick embryo cell rabies vaccine

To determine the minimum vaccine potency per intradermal dose required to elicit an adequate immune response using the Thai Red Cross (TRC) regimen (2-2-2-0-1-1), healthy volunteers received 0.1 mL volumes of PCECV containing decreasing amounts of antigen. Subjects also received HRIG to evaluate potential interference with antibody production. Results indicated that when each 0.1 mL intradermal dose of PCECV contained antigen corresponding to 0.32 IU per intramuscular dose, every subject had titers above 0.5 IU/mL by day 14. These results confirm that the current World Health Organization (WHO) recommendations for vaccine potency (2.5 IU per intramuscular dose) are sufficient for use in the Thai Red Cross intradermal regimen.

Reducing the cost of post-exposure rabies prophylaxis: efficacy of 0.1ml PCEC rabies vaccine administered intradermally using the Thai Red Cross post-exposure regimen in patients severely exposed to laboratory-confirmed rabid animals

Purified chick embryo cell rabies vaccine (PCECV) administered as 0.1 ml intradermally according to the Thai Red Cross (TRC) regimen could reduce the cost of PEP by up to 84% when compared to the traditional five-dose Essen regimen. To confirm the efficacy of 0.1 ml of PCECV using the TRC regimen, a clinical trial was conducted in 113 patients presenting with category III exposures from confirmed rabid animals at two bite referral centres in the Philippines. Patients were monitored monthly for 1 year after exposure. PCECV was well tolerated, no vaccine-related serious adverse events occurred and all patients were alive 1 year after their initial exposure.

Ribozyme targeting of the growth factor pleiotrophin in established tumors: a gene therapy approach

The growth and metastasis of solid tumors relies on the activities of polypeptide growth factors to recruit stromal tissue and expand the tumor mass. Pleiotrophin (PTN) is a secreted growth factor with angiogenic activity that has been found to contribute to the growth and metastasis of tumors including melanoma. Here, we present a gene therapy approach of targeting PTN in established tumors using ribozymes. Tetracycline-regulated ribozyme expression vectors were used to deplete conditionally PTN mRNA from melanoma xenograft tumors in vivo. We found that tetracycline-mediated initiation of ribozyme expression in established tumors reduced further tumor growth. Next, we generated synthetic anti-PTN ribozymes that inhibit PTN-dependent colony formation of cells in soft agar. Intraperitoneal administration of these synthetic ribozymes into nude mice inhibited growth of PTN-positive, subcutaneous melanoma. Furthermore, PTN released from the tumors into the circulation of mice was reduced after ribozyme treatment. These data show that ribozyme targeting of rate-limiting tumor growth factors could provide an efficient tool for cancer therapy and that the efficacy may be reflected in the reduction of the serum levels of the targeted protein, PTN.

Serum bactericidal activity of gemifloxacin versus clarithromycin against Streptococcus pneumoniae with different susceptibility to quinolones

The objective of this study was to determine serum bactericidal titers (SBT, the highest dilution of serum showing no growth) and the serum bactericidal activity (SBA, i.e. duration of SBT greater than 1:2) as well as the serum bactericidal rate of gemifloxacin and clarithromycin after single doses in healthy male volunteers against Streptococcus pneumoniae. Strains tested had various degrees of susceptibility to penicillin as well as different susceptibility to quinolones due to a different QRDR mutation pattern (parC, gyrA). Serum samples from volunteers (n = 12) who had received a single oral dose of either 320 mg gemifloxacin or 500 mg clarithromycin in an open-label crossover study were obtained over a 24-hour period. SBA was determined, using the microdilution method. SBA of wildtype strains for gemifloxacin ranged from 8.9 to 15.4 h (mean 12.6 h). For gemifloxacin, 2 strains with solitary gyrA mutation had an SBA from 4.5 to 4.7 h (median 4.5 h). One of the 2 strains with a single QRDR mutation in parC displayed an SBA of 4.5 h, comparable to the gyrA mutation strains, whereas the second strain had a nearly twice as long SBA of 8.9 h. Two strains with two mutations (parC and gyrA) did not display any SBA. For clarithromycin, the duration of SBA ranged from 11.3 to 15.5 h (mean 13.6 h) for 6 of the 12 strains with an MIC < or = 0.06 mg/L (no SBA was found for the remaining strains, with an MIC of 0.25 mg/L or higher). In conclusion, a correlation between individual serum concentrations and SBA was found for both antibiotics.

Monitoring daunorubicin-induced alterations in protein expression in pancreas carcinoma cells by two-dimensional gel electrophoresis

Tumors of the pancreas are characterized by a high intrinsic potency to develop chemoresistance towards cytotoxic drugs, which is the main cause of ineffective treatment. The phenomenon of multidrug resistance is known to be a multifactorial event in which several mechanisms act simultaneously. We investigated the response of pancreas tumor cells after exposure to the anthracycline daunorubicin (DRC), a well-known antitumor agent in chemotherapy, by two-dimensional gel electrophoresis (2-DE). DRC is known to cause DNA damage and to affect tumor cell growth. Importantly, we aimed at investigating alterations in the protein expression pattern after first contact of the tumor cells with DRC, thus simulating a situation close to clinical chemotherapy and elucidating cell survival strategies following initial drug exposure. A concentration dependent up-regulation of a variety of proteins was observed, indicating that cell response to DRC involves multiple signaling events. Since the p53 tumor suppressor is essentially involved in the regulation of cell growth and controlled cell death (apoptosis) after cellular stress (like DNA damage), we investigated the role of p53 in DRC-resistant and -sensitive pancreas carcinoma cells by measuring p53 transcriptional transactivation activities. No differences in p53 activities were observed in response to DRC treatment in both pancreas cell lines, whereas mamma carcinoma cells (MCF-7), possessing wild-type p53, demonstrated the expected increase in p53 transcriptional transactivation activity. Hence, the tested pancreas carcinoma cells harbor a mutant, nonfunctional p53. We additionally analyzed the steady state protein levels of the cyclin dependent kinase inhibitor p21(CIP1), which is known to be involved in cell cycle control. Interestingly, p21(CIP1 )was induced by DRC in sensitive cells in a concentration dependent manner and was highest in resistant cells. In conclusion, our results suggest that the induction of proteins by DRC in pancreas carcinoma cells, as observed by 2-DE, occurs independently from p53 signaling events, but is probably associated with increased levels of p21(CIP1).

Monitoring daunorubicin-induced alterations in protein expression in pancreas carcinoma cells by two-dimensional gel electrophoresis

Tumors of the pancreas are characterized by a high intrinsic potency to develop chemoresistance towards cytotoxic drugs, which is the main cause of ineffective treatment. The phenomenon of multidrug resistance is known to be a multifactorial event in which several mechanisms act simultaneously. We investigated the response of pancreas tumor cells after exposure to the anthracycline daunorubicin (DRC), a well-known antitumor agent in chemotherapy, by two-dimensional gel electrophoresis (2-DE). DRC is known to cause DNA damage and to affect tumor cell growth. Importantly, we aimed at investigating alterations in the protein expression pattern after first contact of the tumor cells with DRC, thus simulating a situation close to clinical chemotherapy and elucidating cell survival strategies following initial drug exposure. A concentration dependent up-regulation of a variety of proteins was observed, indicating that cell response to DRC involves multiple signaling events. Since the p53 tumor suppressor is essentially involved in the regulation of cell growth and controlled cell death (apoptosis) after cellular stress (like DNA damage), we investigated the role of p53 in DRC-resistant and -sensitive pancreas carcinoma cells by measuring p53 transcriptional transactivation activities. No differences in p53 activities were observed in response to DRC treatment in both pancreas cell lines, whereas mamma carcinoma cells (MCF-7), possessing wild-type p53, demonstrated the expected increase in p53 transcriptional transactivation activity. Hence, the tested pancreas carcinoma cells harbor a mutant, nonfunctional p53. We additionally analyzed the steady state protein levels of the cyclin dependent kinase inhibitor p21(CIP1), which is known to be involved in cell cycle control. Interestingly, p21(CIP1 )was induced by DRC in sensitive cells in a concentration dependent manner and was highest in resistant cells. In conclusion, our results suggest that the induction of proteins by DRC in pancreas carcinoma cells, as observed by 2-DE, occurs independently from p53 signaling events, but is probably associated with increased levels of p21(CIP1).

The human papillomavirus (HPV) 16 E6 oncoprotein leads to an increase in gene expression of the angiogenic switch molecule FGF-BP in non-immortalized human keratinocytes

Fibroblast growth factor binding protein (FGF-BP) is a secreted protein that binds FGF-1 and FGF-2 and is involved in mobilization and activation of FGFs from the extracellular matrix. FGF-BP overexpression as well as ribozyme-mediated reduction of endogenous FGF-BP revealed that FGF-BP can be rate-limiting for tumor growth and angiogenesis. Recent studies showed that FGF-BP expression is up-regulated during early phases of tumorigenesis, indicating that the role of FGF-BP in angiogenesis is a critical early step in the development and progression of tumors. Human papillomavirus type 16 (HPV 16) is highly associated with the development of anogenital cancers. Here we demonstrate that the stable expression of the E6 oncogene of HPV 16 leads to an activation of the FGF-BP promoter in primary human foreskin keratinocytes (one of the natural host cells of these viruses). This is associated with an increase in the steady state levels of FGF-BP mRNA and FGF-BP protein in cells stably expressing E6. Transient E6 expression revealed that the observed activation of the FGF-BP promoter by the viral oncogene is an early process which is independent from immortalization/transformation events in the cells.

Expression of a truncated 100 kDa HER2 splice variant acts as an endogenous inhibitor of tumour cell proliferation

Overexpression of the HER2 (neu/c-erbB-2) oncogene frequently coincides with an aggressive clinical course of certain human adenocarcinomas. Expression and secretion of aberrant HER2 splice variants has been reported in various cell lines and tissues and can interfere with the oncogenic HER2 activity. Here we demonstrate, using two different approaches, that expression of a truncated 100 kDa HER2 variant which encodes the extracellular domain of HER2 (HER-ECD) inhibits growth factor-mediated tumour cell proliferation. A HER2-ECD cDNA encoding the truncated variant was overexpressed in MCF7 breast cancer cells. HER2-ECD overexpression decreased spontaneous proliferation of MCF7 cells as well as heregulin-mediated soft agar colony formation. Concomitantly, heregulin-induced phosphorylation of HER4 as well as downstream activation of p44/p42 MAP-kinases was decreased. To confirm these data, ribozymes were targeted to the 3'-untranslated region of the 2.3 kb HER2-ECD mRNA which is spontaneously expressed in MKN7 gastric cancer cells. HER2-ECD-targeted ribozymes downregulated HER2-ECD expression and enhanced EGF-mediated soft agar colony formation of MKN7 cells. In parallel, EGF-induced activation of p44/p42 MAP-kinases and activation of c-Fos expression were increased in ribozyme-transfected MKN7 cells. Finally, in RT-PCR we found a trend towards a progressive loss of 2.3 kb HER2-ECD mRNA expression in more advanced gastric tumours. These data show that the HER2-ECD variant inhibits growth factor-mediated tumour cell proliferation suggesting an important role during the progression of human cancer.

Identification of anaplastic lymphoma kinase as a receptor for the growth factor pleiotrophin

Pleiotrophin (PTN) is a secreted growth factor that induces neurite outgrowth and is mitogenic for fibroblasts, epithelial, and endothelial cells. During tumor growth PTN can serve as an angiogenic factor and drive tumor invasion and metastasis. To identify a receptor for PTN, we panned a phage display human cDNA library against immobilized PTN protein as a bait. From this we isolated a phage insert that was homologous to an amino acid sequence stretch in the extracellular domain (ECD) of the orphan receptor tyrosine kinase anaplastic lymphoma kinase (ALK). In parallel with PTN, ALK is highly expressed during perinatal development of the nervous system and down-modulated in the adult. Here we show in cell-free assays as well as in radioligand receptor binding studies in intact cells that PTN binds to the ALK ECD with an apparent Kd of 32 +/- 9 pm. This receptor binding is inhibited by an excess of PTN, by the ALK ECD, and by anti-PTN and anti-ECD antibodies. PTN added to ALK-expressing cells induces phosphorylation of both ALK and of the downstream effector molecules IRS-1, Shc, phospholipase C-gamma, and phosphatidylinositol 3-kinase. Furthermore, the growth stimulatory effect of PTN on different cell lines in culture coincides with the endogenous expression of ALK mRNA, and the effect of PTN is enhanced by ALK overexpression. From this we conclude that ALK is a receptor that transduces PTN-mediated signals and propose that the PTN-ALK axis can play a significant role during development and during disease processes.

Comparative pharmacodynamics and pharmacokinetics of candesartan and losartan in man

The angiotensin II antagonistic effects of candesartan and losartan were compared in-vivo after single and repeated doses. Effects were related to antagonistic activity in plasma. In this double-blind, crossover study, 12 healthy male volunteers received, in random order, daily oral doses of 8 mg candesartan cilexetil or 50 mg losartan for seven days. On day 1 and day 8, dynamics and kinetics were assessed up to 48 h after dosing. Antagonistic effect was determined from the antagonist-induced rightward shifts of the diastolic blood pressure response curves to exogenously administered angiotensin II measured as the dose ratio (DR). The antagonistic activity in plasma was measured using an ex-vivo/in-vitro radioreceptor assay. Specific high-performance liquid chromatography assays determined plasma concentrations of candesartan, losartan and its active metabolite EXP-3174. The pharmacokinetic properties of candesartan and losartan were comparable and antagonistic activity in plasma almost identical (ratio candesartan: losartan = 0.97 and 1-2 after single and multiple doses, respectively). However, the antagonistic effects of candesartan and losartan in-vivo were quite different. Twenty-four hours after single dosing with candesartan a clinically relevant rightward shift in the angiotensin II dose-response curve (DR= 3.2) occurred that was more pronounced than that following losartan administration (DR=2.1, ratio candesartan: losartan= 1.65). Twenty-four hours after multiple doses of candesartan or losartan, the values of the DR were 4.8 and 2.3, respectively (ratio candesartan: losartan = 1.94). The values of DR for candesartan were significantly higher compared with losartan between 6 and 36h after a single dose and between 3 and 24 h post-dose following multiple dose administration. A counter-clockwise hysteresis was apparent between antagonistic activity in plasma and antagonistic effect. Despite equivalent angiotensin II antagonistic activity in plasma, the pharmacodynamic effect of candesartan cilexetil was greater than that of losartan. Candesartan appeared to have a slower off-rate from the angiotensin AT1-receptor compared with losartan, nevertheless differences in distributional phenomena or the extent of insurmountable antagonistic activity cannot be ruled out.

Influence of the human endogenous retrovirus-like element HERV-E.PTN on the expression of growth factor pleiotrophin: a critical role of a retroviral Sp1-binding site

Germ line insertion of a human endogenous retrovirus-like element (HERV-E.PTN) into the growth factor pleiotrophin (PTN) gene generated a phylogenetically new promoter driving the expression of functional HERV-PTN fusion transcripts. Here we show by in situ hybridization, that HERV-PTN fusion transcripts are expressed in malignant trophoblasts (i.e. choriocarcinoma) and in the proliferative and in the invasive trophoblasts of gestational trophoblastic tissue. Additionally, a 1.9 kb fragment of the HERV-derived PTN promoter was analysed which has strong activity when transiently transfected into choriocarcinoma JEG-3 cells in contrast to HeLa cells. Deletion of the retrovirally-derived promoter portion abolished its activity and an enhancer (+443 to +486) was identified in this region. Electrophoretic mobility shift and supershift experiments identified a Sp1 binding site in this enhancer and site specific mutation of this site abolished its activity in choriocarcinoma cells. Sp1 overexpression in Drosophila SL2 cells showed that the enhancer activity is mediated via Sp1 binding in vivo. Furthermore, mutation of the Sp1 binding site reduced the activity of a promoter test fragment in choriocarcinoma cells by 80%. Our result shows that a retroviral Sp1 binding site in the PTN promoter is important for the expression of growth factor pleiotrophin in human choriocarcinoma cells. Oncogene (2000) 19, 3988 - 3998.

ERbB-2 expression is rate-limiting for epidermal growth factor-mediated stimulation of ovarian cancer cell proliferation

Over-expression of the ErbB-2 proto-oncogene frequently coincides with an aggressive clinical course of certain human adenocarcinomas. The ErbB-2 receptor is a member of the ErbB family of growth factor receptors, and within this complex signaling network, ErbB-2-containing heterodimers are preferentially formed. To assess whether ErbB-2 is a critical component in epidermal growth factor (EGF)-mediated stimulation of tumor cell proliferation, we used as a model SK-OV-3 ovarian cancer cells, which over-express EGF receptor (EGFR) and ErbB-2 receptors. In these cells, we reduced ErbB-2 mRNA and protein expression by transfection with ErbB-2-targeted hammerhead ribozymes and generated cell lines expressing different levels of ErbB-2. In SK-OV-3 cells, ErbB-2 expression conferred a growth advantage and soft agar experiments revealed that ErbB-2 was rate-limiting for anchorage-independent growth. The induction of colony formation by EGF was completely abrogated in ErbB-2-depleted cells, despite unchanged expression levels and tyrosine phosphorylation of the EGFR. The duration of EGF-mediated c-Fos mRNA up-regulation was decreased in parallel with loss of ErbB-2 expression. Furthermore, the rate of spontaneous apoptosis was increased in ErbB-2-depleted cells. Our results demonstrate that in human ovarian cancer cells the EGFR-ErbB-2 heterodimer, and not the EGFR homodimer, can be rate-limiting for EGF-mediated proliferation, thus suggesting that the oncogenic activity of ErbB-2 in human tumors is due in part to its ability to increase the growth response to stroma-derived EGF-like growth factors.

Reversal of HER-2 over-expression renders human ovarian cancer cells highly resistant to taxol

Currently, the treatment options for advanced ovarian cancer are limited. Thus, the majority of the patients are treated with drugs with considerable side effects but in many cases without clinical benefit. The relationship between activation of an oncogene like the HER-2 receptor and drug sensitivity, is of considerable interest as this molecular marker may allow to better predict response to chemotherapy. The aim of this study was to evaluate whether over-expression of the HER-2 receptor would modulate drug responsiveness to doxorubicin, cisplatin and taxol in ovarian cancer cells. An anti-HER-2-targeted ribozyme approach was used to abrogate HER-2 expression in human SK-OV-3 ovarian cancer cells. SK-OV-3 cells expressing very low residual levels of HER-2 protein, were then assessed for their sensitivity to doxorubicin, cisplatin and taxol and compared to control cells. HER-2 expression had no effect on the cytotoxicity of doxorubicin (IC50=10 nM) or cisplatin (IC50=5 microM) in proliferation assays. In contrast, the sensitivity to taxol was increased approximately 70-fold in SK-OV-3 ovarian cancer cells expressing high levels of HER-2 (IC50=10(-5) nM) compared to HER-2 depleted cells (IC50=7x10(-4) nM). If these findings can be confirmed in patients, it could be possible that HER-2 expression may serve as a marker for response to taxol treatment in ovarian cancer patients.

Tissue distribution and retinoid-mediated downregulation of an FGF-binding protein (FGF-BP) in the rat

We showed previously that a secreted fibroblast growth factor-binding protein (FGF-BP) can mobilize and bioactivate locally-stored FGFs from the extracellular matrix. This FGF-BP is upregulated in various cancers and plays a rate limiting role as an angiogenic switch molecule during tumor growth. In this paper, we describe the cloning and sequence analysis of the rat homologue of FGF-BP and show its expression pattern and retinoid-mediated downregulation in normal adult rat tissues. The rat FGF-BP amino acid sequence is 91% and 70% homologous to mouse and human, respectively, and contains 10 cysteine residues whose position is conserved across species. In Northern blots, FGF-BP mRNA was detected in the gut, eye, thymus, skin, lung and tongue. Immunohistochemistry confirmed this tissue distribution with cerebellar Purkinje cells, the cerebral chorioid plexus and the eye showing the most distinctive staining patterns. Oral treatment of animals with all-trans-retinoic acid for one and two days induced a significant decrease of FGF-BP protein in tissues from stomach, eye and lung suggesting that regulation of FGF-BP can be one effector mechanism through which retinoids affect normal and pathological processes.

Angiotensin II antagonism and plasma radioreceptor-kinetics of candesartan in man

AIMS

The pharmacodynamic properties of the angiotensin II antagonist candesartan in humans were assessed from the rightward shifts of angiotensin II dose-effect curves (Schild regression technique). The pharmacokinetic characteristics were determined by radioreceptor assay (r.r.a.) and h.p.l.c.

METHODS

Twelve healthy male volunteers received single oral doses of 4, 8 and 16 mg candesartan cilexetil and placebo. Plasma was obtained for h.p.l.c. and r.r.a. (receptors: rat lung; radioligand: [125I-Sar1Ile8]-angiotensin II). Before and up to 24 h post dosing angiotensin II was infused in ascending dose steps until blood pressure (systolic and/or diastolic) increased by +25 mmHg. Individual angiotensin II dose-effect curves were fitted according to an Emax model and dose ratios (DR) calculated from the antagonist induced rightward shifts.

RESULTS

Candesartan, the active metabolite of candesartan cilexetil, declined from peak concentrations at about 4 h with a t1/2 of about 6 h. A linear relation (slope 1) between h.p.l.c. and r.r.a. data revealed that there is no other active metabolite. DR at 6-9 h post dosing reached a maximum of about 30 and at 24 h still amounted to 4-7, indicating the persistence of a relevant antagonistic effect in vivo. The apparent Ki-doses (derived from Schild regression plots) indicated a high potency (1.9 mg at 24 h) and slow decline of effect. Between plasma concentrations and antagonistic effect a counterclockwise hysteresis was visible.

CONCLUSIONS

A longer persistence of the antagonistic effect at the receptor site than expected by the presence in plasma indicates a slow off-rate of candesartan cilexetil from in vivo receptors. This provides an additional rationale for the observed 24 h therapeutic activity of candesartan cilexetil.

Pharmacodynamic and pharmacokinetic properties of an angiotensin II receptor antagonist--characterization by use of Schild regression technique in man

OBJECTIVE

The pharmacodynamic properties of a new angiotensin II receptor antagonist (BAY 10-6734) in humans were to be quantitatively characterized from the rightward shifts of the agonist dose-response curves after administration of different doses of the antagonist.

METHODS

24 healthy male volunteers received single oral doses of 20-300 mg BAY 10-6734. Before and up to 23 h post dosing (p.d.) plasma was obtained for HPLC measurement of parent compound and active metabolite BAY 10-6735. Exogenous angiotensin II was infused in increasing dose steps until blood pressure had increased by +25 mmHg. Angiotensin II dose-response curves were fitted individually using the sigmoidal Emax model. From the antagonist-induced rightward shifts, as compared to a premedication curve, dose ratios (DR) were determined and DR-1 plotted versus applied dosages and measured plasma concentrations. From these Schild regression plots the fictive doses and concentration (Ki) inducing a DR-1 = 1, i.e. a 2-fold shift in agonist dose-response curves, were derived. The "doubling (t2.0) time" of the apparent Ki doses was calculated.

RESULTS

BAY 10-6734 dose-dependently induced rightward shifts of the angiotensin II blood pressure response curves, mean maximum DR at 2 h p.d. ranged from 42 (80 mg) to 216 (300 mg), and at 23 h p.d. decreased to about 2 (80 mg) to 4 (300 mg). Pharmacodynamic (3.4-4.6 h) and pharmacokinetic half-lives (3.4-4.3 h) were nearly identical. Apparent Ki doses increased from about 1-2 mg at 2 h p.d. to about 80-100 mg at 23 h p.d., their time course revealed a doubling (t2.0) time of 3.5-3.8 h. A Ki concentration of about 10 micrograms/l was obtained for the active metabolite BAY 10-6735.

CONCLUSIONS

Oral administration of BAY 10-6734 in man antagonized angiotensin II dose blood pressure response curves in a dose-dependent manner. The time kinetics of the pharmacodynamic effect, derived from the decay of DR-1 values, as well as the doubling time of the apparent Ki values well agreed with the pharmacokinetic half-life. Schild regression revealed competitive angiotensin II antagonistic properties within the dose/concentration range tested. This technique was shown to be an adequate means to evaluate pharmacodynamic potency and kinetic behavior of an angiotensin II receptor antagonist in vivo.