Clinical features and outcomes in adults with COVID-19 during the pre-Omicron and Omicron waves

OBJECTIVES

We conducted a single-center retrospective study to compare patient characteristics and death rates during the Omicron (O, December 01, 2021, to September 30, 2022) and pre-Omicron (PO, March 01, 1920, to October 31, 2021) periods.

PATIENTS AND METHODS

We retrospectively analyzed the data of 2932 patients (1242 (O) and 1690 (PO)) hospitalized (>24 h) with laboratory-confirmed COVID.

RESULTS

Compared to the PO period, O period patients were less frequently men, had a lower body mass index and fewer comorbidities except for immunosuppression and pregnancy. Nosocomial COVID-19 accounted for 18.2 % (O) and 15.4 % (PO) of cases (p = 0.05). Patient mortality rates during the O and PO periods were 11.0 % and 16.9 % (p < 0.001), respectively. Unvaccinated status (p < 0.001), existence of comorbidities, (p < 0.001) and high LDH value at baseline (p = 0.015), but not the period, were identified as factors likely to explain death.

CONCLUSION

During the Omicron period, the inpatient death rate remained > 10 %, especially among unvaccinated and comorbid patients. Nosocomial cases were more frequent.

Characteristic and outcome changes in inpatients with COVID-19 during the four pre - Omicron waves

Background

Four waves of Coronavirus disease 2019 (COVID-19) occurred in France between March 2020 and September 2021. COVID-19 inpatient characteristics change because of the influence of numerous parameters, especially immunization and circulating severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) variants.

Methods

This retrospective single-center study analyzed patients with laboratory-proven COVID-19 admitted from 1/3/2020 to 30/6/2020 (wave one), 1/7/2020 to 31/12/2020 (wave two), 1/1/2021 to 30/6/2021 (wave three), and 1/7/2021 to 30/11/2021 (wave four). We compared the outcomes and baseline characteristics between these waves.

Results

In our center, 1,762 patients were hospitalized for COVID-19: 666 (37.8 %), 425 (24.1 %), 482 (27.3 %), and 189 (10.7 %) during waves 1, 2, 3, and 4, respectively. Patients during the first wave were hospitalized later after the onset of COVID-19 symptoms, had more severe disease conditions at baseline, and suffered higher intensive care unit (ICU) hospitalization rates. Most patients from waves 1-3 were >70 years old, with 88-93 % having ≥1 comorbidity, whereas those from wave four were younger (68.0 years) with less comorbidities. The first two waves showed higher mortality rates (16.8 % and 20.0 %) than the latter (16.6 % and 9.5 %).

Conclusion

Patients during the first wave had more severe disease conditions at baseline and higher mortality and ICU hospitalization rates. Despite the more virulent circulating Delta variant during wave four, the death and hospitalization rates were markedly decreased during wave four. HIPPOKRATIA 2023, 27 (1):1-6.

Demographics and outcomes of laboratory-confirmed COVID-19 cases during the first epidemic wave in Senegal

BACKGROUND

Few studies have focused on the effects of COVID-19 on African populations. During the first epidemic wave in Senegal (May 1 to July 31, 2020), COVID-19 cases were isolated in treatment centers of epidemics (TCEs). We described the demographics and outcomes of COVID-19 cases in TCEs.

PATIENTS AND METHODS

All cases with laboratory-confirmed COVID-19 in Thiès medical region of Senegal were included.

RESULTS

COVID-19 was confirmed in 600 cases. Median age of cases (men: 357, 59.5%; women: 243, 40.5%) was 34.0years. The incidence was 12 per 100,000 inhabitants per month. Overall, 46 (7.7%) cases had a severe or critical form of the disease, and nine of them died. Of 455 cases quarantined in non-hospital TCEs, 340 (74.7%) had no symptom and 115 (25.3%) had mild or moderate symptoms.

CONCLUSION

In this African retrospective cohort, COVID-19 cases were young and mostly asymptomatic with a low case fatality rate.

Evolution of baseline characteristics and severe outcomes in COVID-19 inpatients during the first and second waves in Northeastern France

Objectives

Two COVID-19 epidemic waves occurred in France in 2020. This single-center retrospective study compared patients’ characteristics and outcomes.

Patients and methods

We included all patients with confirmed COVID-19 admitted to Colmar Hospital in March (n = 600) and October/November (n = 205) 2020.

Results

Median ages, sex ratio, body mass index, and number of comorbidities were similar in wave 1 and 2 patients. Significant differences were found for temperature (38 °C vs. 37.2), need for oxygen (38.6% vs. 26.8%), high-flow cannula (0% vs. 8.3%), and steroid use (6.3% vs. 54.1%). Intensive care unit (ICU) hospitalizations (25.5% vs. 15.1%, OR: 0.44, 95% CI [0.28; 0.68], P = 0.002) and deaths (19.2% vs. 12.7%, OR: 0.61, 95% CI [0.37; 0.98], P = 0.04) decreased during the second wave. Except for cardiovascular events (5.5% vs. 10.2%), no change was observed in extrapulmonary events.

Conclusions

Deaths and ICU hospitalizations were significantly reduced during the second epidemic wave.

Predictors of mortality, ICU hospitalization, and extrapulmonary complications in COVID-19 patients

OBJECTIVE

A major coronavirus disease 2019 (COVID-19) outbreak occurred in Northeastern France in spring 2020. This single-center retrospective observational cohort study aimed to compare patients with severe COVID-19 and those with non-severe COVID-19 (survivors vs. non-survivors, ICU patients vs. non-ICU patients) and to describe extrapulmonary complications.

PATIENTS AND METHODS

We included all patients with a confirmed diagnosis of COVID-19 admitted to Colmar Hospital in March 2020.

RESULTS

We examined 600 patients (median age 71.09 years; median body mass index: 26.9 kg/m²); 57.7% were males, 86.3% had at least one comorbidity, 153 (25.5%) required ICU hospitalization, and 115 (19.1%) died. Baseline independent factors associated with death were older age (>75 vs. ≤75 years), male sex, oxygen supply, chronic neurological, renal, and pulmonary diseases, diabetes, cancer, low platelet and hemoglobin counts, and high levels of C-reactive protein (CRP) and serum creatinine. Factors associated with ICU hospitalization were age <75 years, oxygen supply, chronic pulmonary disease, absence of dementia, and high levels of CRP, hemoglobin, and serum creatinine. Among the 600 patients, 80 (13.3%) had an acute renal injury, 33 (5.5%) had a cardiovascular event, 27 (4.5%) had an acute liver injury, 24 (4%) had venous thromboembolism, eight (1.3%) had a neurological event, five (0.8%) had rhabdomyolysis, and one had acute pancreatitis. Most extrapulmonary complications occurred in ICU patients.

CONCLUSION

This study highlighted the main risk factors for ICU hospitalization and death caused by severe COVID-19 and the frequency of numerous extrapulmonary complications in France.

[Screening for the risk of allergy and prevention in French maternity units: A survey]

Allergy has been on the rise for half a century and concerns nearly 30% of children; it has now become a real public health problem. The guidelines on prevention of allergy set up by the French Society of Paediatrics (SFP) and the European Society of Paediatric Allergology and Clinical Immunology (ESPACI) are based on screening children at risk through a systematic search of the family history and recommend, for children at risk, exclusive breastfeeding whenever possible or otherwise utilization of hypoallergenic infant formula, which has demonstrated efficacy. The AllerNaiss practice survey assessed the modes of screening and prevention of allergy in French maternity units in 2012. The SFP guidelines are known by 82% of the maternity units that took part in the survey, and the ESPACI guidelines by 55% of them. A screening strategy is in place in 59% of the participating maternity wards, based on local consensus for 36% of them, 13% of the units having a written screening procedure. Screening is based on the search for a history of allergy in first-degree relatives (99%) during pregnancy (51%), in the delivery room (50%), and after delivery (89%). A mode of prevention of the risk of allergy exists in 62% of the maternity units, most often in writing (49%). A hypoallergenic infant formula is prescribed for non-breastfed children in 90% of the units. The survey shows that there is a real need for formalization of allergy risk screening and prevention of allergy in newborns in French maternity units.

Treatment maintenance duration of dual therapy with metformin and sitagliptin in type 2 diabetes: The ODYSSEE observational study

AIM

The study compared the duration of maintenance of treatment in patients with type 2 diabetes (T2D) using dual therapy with either metformin and sitagliptin (M-Sita) or metformin and a sulphonylurea (M-SU).

MATERIALS AND METHODS

This observational study included adult patients with T2D who had responded inadequately to metformin monotherapy and therefore had started de-novo treatment with Met-Sita or Met-SU within the previous eight weeks. Patient follow-up and changes to treatment were performed according to their general practitioner's usual clinical practice. The primary outcome was time to change in treatment for whatever cause. HbA1c and symptomatic hypoglycaemia were also documented.

RESULTS

The median treatment duration for patients in the M-Sita group (43.2 months) was significantly longer (P < 0.0001) than in the M-SU group (20.2 months). This difference persisted after adjusting for baseline differences and confounders. A similar reduction in HbA1c was noted in both arms (-0.6%), and the incidence of hypoglycaemia prior to treatment modification was lower with M-Sita (9.7%) than with M-SU (21.0%). Adverse events potentially related to treatment were reported in 2.8% (n = 52) and 2.7% (n = 20) of patients in the M-Sita and M-SU arms, respectively.

CONCLUSION

Under everyday conditions of primary diabetes care, dual therapy with M-Sita can be maintained for longer than M-SU. In addition, while efficacy, as measured by changes in HbA1c, was similar between treatments, the incidence of hypoglycaemia was lower in patients taking M-Sita.

Renal function, attributes and coagulation treatment in atrial fibrillation (R-FACT Study): retrospective, observational, longitudinal cohort study of renal function and antithrombotic treatment patterns in atrial fibrillation patients with documented eGFR in real-world clinical practices in Germany

AIMS

This retrospective, observational, longitudinal study aimed to document the distribution, changes in renal function [measured by estimated glomerular filtration (eGFR)] and antithrombotic treatment pattern in atrial fibrillation (AF) patients in real-world settings managed by general practitioners in Germany.

METHODS AND RESULTS

Data were extracted from the German Longitudinal Patient Database. A total of 15,900 patients with AF were identified. Among 1660 having eGFR available at baseline, 3.4% had severely impaired eGFR, 9.7% and 25.6% had moderate severe decrease and moderate decrease in eGFR, respectively, and 61.3% had mildly decreased/normal eGFR. Patients with moderately and severely decreased eGFR tended to be older. The proportion of patients with a CHADS2 score ≥ 2 was 92.9% in those with severely decreased eGFR, and 87.0% and 79.1% in those with moderately severe and moderately decreased eGFR. During follow up, 52.1% of patients with severely decreased eGFR, and 26.3% to 23.7% of patients with moderately decreased eGFR were not treated by antithrombotic. When comparing baseline with follow-up eGFR, 55.0% of patients showed decreased eGFR. Age, diabetes, dyslipidaemia and history of myocardial infarction were identified as significant predictors for renal function deterioration based on results from multivariate Cox regression model.

CONCLUSIONS

Moderate-to-severe renal dysfunction is prevalent (~38%) in German AF patients with documented eGFR managed in actual clinical practices. The risk of stroke, as measured by the CHADS2 score, was associated with decreased renal function. Treatment with anticoagulation therapies decreased with decreasing renal function, despite increasing risk of stroke. Anticoagulation treatments remain suboptimal during the 12-month follow up in patients with moderate or severe renal impairment.

[Tolerance and adequacy of a 100% lactose infant formula. A controlled randomized double-blind study]

Lactose has beneficial nutritional effects in infancy, particularly on calcium retention and on Bifidobacterium colon microflora development.

OBJECTIVE

The objective of this controlled, prospective, randomized double-blind study was to assess the adequacy and safety of an infant formula containing only lactose as carbohydrate, as compared to a usual formula.

PATIENTS AND METHODS

Healthy non-breast-fed infants aged under 7 days were randomized to be fed exclusively with a conventional formula containing lactose (9.6 g/100 kcal) and maltodextrin (1.6 g/100 kcal) or the isocaloric-isoprotein study formula containing 100% lactose (11.2 g/100 kcal) for 120 days. Primary outcome was daily weight gain at D0 and D120. Weight, length, body mass index, formula consumption, tolerance, and safety were assessed monthly. The non-inferiority of the study formula was rejected if the difference in weight gain was higher than 2.5 g/day in the control group.

RESULTS

One hundred and seventy-eight infants were enrolled. Mean daily weight gain in the study group differed by 0.71 g/day (95% CI: -2.23; 0.82) indicating the non-inferiority of the study formula. Growth was normal and similar in the two groups, but formula intake was decreased in the study group, leading to a decrease in energy and protein intakes. Tolerance was good and adverse events did not differ between the two groups.

CONCLUSION

The 100% lactose study infant formula was safe and non-inferior to a conventional formula in ensuring normal growth during the first 4 months of life.

[Virus detection, clinical signs, and laboratory findings in dogs with acute hemorrhagic diarrhea: a retrospective study of 935 cases]

OBJECTIVE

The study evaluated which viruses can be detected in dogs with acute hemorrhagic diarrhea and compared signalment, clinical signs, and laboratory abnormalities among groups of dogs infected with different viruses and those that tested virus-negative.

MATERIAL AND METHODS

Fecal samples from 935 dogs with acute hemorrhagic diarrhea were examined by electron microscopy. The medical records of these patients were retrospectively evaluated for clinical and laboratory parameters.

RESULTS

Virus was detected in 44.2% of the dogs presented with acute bloody diarrhea. The highest prevalence for a virus infection was demonstrated for canine parvovirus (19.9%), followed by coronavirus (17.3%), and paramyxovirus (13.9%). More than one virus species was detected in 6.5% of all fecal samples. Dogs with a virus-positive fecal sample were significantly younger than dogs that tested negative on electron microscopy. Among virus-positive dogs, dogs with parvovirus infection were significantly younger when compared to dogs infected with other enteric viruses. Parvovirus-infected patients also showed significantly lower leukocyte and erythrocyte counts as well as hematocrit, total protein, and albumin levels compared to all other groups. No significant differences were seen when evaluating sex, clinical parameters, character of diarrhea or vomiting among all groups.

CONCLUSION

Young dogs are more likely to suffer from viral enteritis.

CLINICAL RELEVANCE

Based on clinical parameters it is not possible to differentiate a virus-positive from a virus-negative dog or to diagnose a certain virus species. Besides the young age, parvovirus infection is associated with typical changes in laboratory parameters, but not with specific clinical signs. A virologic fecal examination is always indicated.

Critical factors influencing prion inactivation by sodium hydroxide

BACKGROUND AND OBJECTIVES

Transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative diseases caused by aberrantly folded cellular proteins (PrP(Sc); prions) that are generally resistant to conventional pathogen-inactivation techniques. To ensure effective decontamination and inactivation of prions that could be present in source material, we investigated critical factors that influence prion inactivation by NaOH.

MATERIALS AND METHODS

A decrease in prion infectivity correlates with the disappearance of the protease-resistant core of PrPSc (PrPRES) observed in biochemical assays. To model prion inactivation, hamster scrapie (strain 263K) brain homogenate (SBH) was incubated for specific periods of time in 0.1 m NaOH at 4 or 18 degrees C, with or without detergent. Neutralized samples were subjected to limited digestion with proteinase K (PK) and then analysed using an endpoint dilution western blot assay and antibody 3F4. Structural changes in prions exposed to NaOH were examined using differential immunoprecipitation.

RESULTS

Treatment of SBH with 0.1 m NaOH for 15 min, in the absence of detergent, at 4 and 18 degrees C caused a reduction in the PrP(RES) signal of 3.5 and 4.0 log10 units, respectively, with some residual signal remaining. The presence of the detergent sarkosyl during a 60-min incubation in NaOH further enhanced PrPRES reduction to > or = 4.5 log10 units (i.e. below the limit of detection). NaOH treatment induced conformational changes in PrP that resulted in the exposure of a hidden epitope and enabled prion immunoprecipitation by antibody 3F4.

CONCLUSIONS

The use of NaOH can effectively reduce prion levels in an in vitro inactivation assay. After pretreatment of SBH with detergent, NaOH completely eliminates the PrPRES signal. Detergent may liberate lipid membrane-protected PrPSc to improve access to NaOH, which can then inactivate PrPSc by altering its structure. In cases of unidentified exposure to PrPSc during manufacturing, sanitizing procedures combining the use of detergent and NaOH may help to ensure minimal levels of contamination carryover in products.

Lenograstim after autologous peripheral blood progenitor cell transplantation: results of a double-blind, randomized trial

A phase III, randomized, double-blind, placebo-controlled, multi-center trial was conducted in order to compare the incidence of microbiologically defined infections occurring after high-dose chemotherapy (HDT) and ASCT in 98 patients given lenograstim (Granocyte) and 94 patients given placebo after transplantation. Hematopoietic recovery, the use of i.v. antibiotics, the numbers of red blood cell and platelet transfusions, the days spent in hospital, and the days on parenteral nutrition were also compared. The incidence of infections until neutrophil recovery was significantly less in patients who received lenograstim after HDT and ASCT as compared to patients who received placebo (66 of 98 vs 86 of 94 patients, P<0.001). Lenograstim also significantly reduced the use of i.v. antibiotics (P<0.001) and the median duration of i.v. antibiotic treatment (8 days vs 10 days, P=0.04), improved neutrophil recovery (absolute neutrophil count >0.5 x 10(9)/l: 11 days vs 15 days, P<0.001) and reduced the number of days spent in hospital (15 days vs 17 days, P<0.001). The administration of lenograstim after HDT and ASCT significantly reduces the incidence of microbiologically defined infections until neutrophil recovery. It also leads to less use of antibiotics and earlier discharge from hospital.

Partitioning of TSE infectivity during ethanol fractionation of human plasma

The practice of validating processes for their capacity to inactivate a range of non-enveloped and enveloped viruses also provides confidence that plasma products will be safe from emerging viral pathogens with known aetiology. Of greater concern are diseases of unknown or poorly defined aetiology such as the group of neurological diseases collectively called the transmissible spongiform encephalopathies (TSEs), or prion diseases, for which the best known human disease is Creutzfeldt-Jakob Disease (CJD) and its variant form (vCJD). The goal of the current study was to investigate the potential for manufacturing steps used in the production of albumin and immunoglobulin products by Kistler-Nitschmann fractionation, and the utility of nanofiltration of immunoglobulin to remove TSE agents. Two different scrapie model systems were used. In the first system infectious material used for spiking was scrapie sheep brain homogenate with infectivity titres being measured in hamsters. In the second system purified scrapie agent was used (PrP fibrils) with Western blot analysis measuring reduction in the proteinase K resistant form being used as a measure of removal. The data demonstrated substantial removal of the infectious agent by the manufacturing process in both model systems although some differences were observed in partitioning of the two different infectious materials. The hamster infectivity studies were shown to be approximately 1000 fold more sensitive than the Western Blot assay. The data from both studies provide added confidence that these plasma products are safe with respect to their potential to transmit TSE.

Strengths and limitations of the model virus concept

New plasma- or cell culture-based pharmaceutical manufacturing processes must be validated for their ability to eliminate potentially contaminating pathogens. To evaluate the virus elimination potential of such a process, current guidelines propose the use of model viruses. This approach is discussed based on two examples. These examples show the strengths of this approach but also its limitations. The blood processing industry was recently challenged by the emergence of a West Nile Virus (WNV) epidemic in the United States. The susceptibility of WNV and a frequently used model virus to commonly used inactivation methods is compared. Current data show a good correlation. Due to its physico-chemical properties and the high viremic titers, B19 virus (B19V), a small (diameter 18-26 nm), robust, non-enveloped parvovirus, is a considerable challenge for the plasma processing industry. Mice minute virus (MMV), an animal parvovirus, is used as a model for B19V. Data show that B19V is considerably more susceptible to some physico-chemical inactivation methods than MMV. The examples of WNV and B19V show that the model virus concept is a practicable tool to evaluate the safety of plasma- or cell culture-derived pharmaceuticals regarding known and emerging viruses. It also underlines the need for investigational studies of relevant viruses if they can be handled in a normal virology laboratory, under moderate biosafety conditions.

Neuroprotective effect of gacyclidine. A multicenter double-blind pilot trial in patients with acute traumatic brain injury

The aim of this study was to assess the safety and efficacy of intravenous (IV) injections of gacyclidine, a novel NMDA receptor antagonist, for neurological and functional recovery following acute traumatic brain injury. This multicenter, prospective, randomized, placebo-controlled, double-blind study compared four parallel groups. Two IV doses were administrated (placebo, 2x0.005mg/kg, 2x0.001mg/kg, 2x0.02mg/kg): the first dose was given within 2 hours following the trauma, and the second dose 4 hours after the first. Fifty-one patients were enrolled and 48 studied between March 1995 and June 1997 in France. Evaluation criteria for safety were physical examination, cardiovascular parameters, blood chemistry, hematology, ECG, and neuropsychological changes monitored after medication. Primary evaluation criteria for efficacy was the Glasgow coma scale complemented by the initial CT-scan and Glasgow outcome scale, motor deficiencies, neuropsychological changes, and functional indenpendence at D90 and D365 or endpoint. Intracranial pressure (ICP) monitoring was not taken into account because all the clinical centers participating in this study did not use this technique in daily practice during the inclusion period. Twelve patients died during the follow-up period, none of these deaths being related to the drug. Serious adverse events (181) were reported by most of the patients with no significant differences between groups. Only 10 of these adverse events were considered to be drug-related. Safety-related laboratory tests did not show any relevant changes. Concerning efficacy, the predefined prognostic factors (initial CT-scan score, initial Glasgow Coma Scale and occurrence of low systolic blood pressure during the first 24 hours) largely determinated the patient's outcome. When the prognostic factors were taken into account together with the dose level in a logistic regression model, gacyclidine showed a beneficial long-term effect and a best dose-result in the 0.04mg/kg treated group. Data obtained in this clinical trial appeared sufficient to warrant a European multicenter study on gacyclidine using the same evaluation criteria and ICP monitoring.

[FACT: French national registry of acute coronary syndromes. Specific study of French general hospital centers]

The FACT registry is currently the French registry including the greatest number of patients with acute coronary syndromes.

PURPOSE

The study presents epidemiologic data, modalities and delays for medical admission.

METHOD

Three thousand nine hundred and two patients were included in FACT by 362 French centers of cardiology between 06/01/2003 and 03/02/2003. One thousand eight hundred and ten patients, who had been placed in the cardiology departments of French general hospitals, were isolated from this registry. The French general hospitals represented 50.8% of the 362 centers. In order to clarify the study, these patients were divided into three groups: group A: patients without ST segment elevation but with suggestive ECG modifications; group B: patients with ST segment elevation; group C: all other patients. The results were mainly studied for groups A and B and compared. These results were also compared to those of the FACT registry and of other registries.

RESULTS

The results show that the average delay for admission is 2.9 h after a first delay between the pain and the help of 6.7 h. The first intervening party is a general practitioner (36.4%) then the SAMU (31.6%) and finally the emergency departments (18.7%). 16.6% of the patients from group B undergo pre-hospital thrombolysis. The recommendations of the European Society of Cardiology are widely applied except for the most recent of them since only 27.6% of the patients from group A having a TIMI score > or = 5 receive an anti-GIIB IIIA treatment. The reasons of the non-prescription of the recommended classes are mostly linked to contra-indication and intolerance. The strategy of coronary reopening mainly depends on the presence or the absence in the department of an available medical equipment for angioplasty. If there is one, the percentage of primary angioplasty reaches 54.2% and the percentage of thrombolysis 7.9%. On the opposite, there is 8.3% of angioplasty and 54.2% of thrombolysis for the unequipped centers. The global mortality reaches 5.8% but is inversely proportional to the level of equipment of the departments: 5.9% for the departments with angioplasty, 11% for the departments with coronarography but without angioplasty and 13.8% for the departments without any interventional equipment. Nevertheless, the age of the patients is different and this influences the results: we notice that the less equipped the department is, the older the patients are.

CONCLUSION

The FACT registry and the data from the general hospitals give the opportunity to think about the possibilities to improve the delays of call to the first intervening party (more particularly to the SAMU) but it also allows us to think about how to better organize the geographical distribution giving access to a medical equipment for angioplasty. All these information will also help the cardiologists to gather around the recommendations by convincing them that the benefit/risk ratio is positive.

Removal of neutralized model parvoviruses and enteroviruses in human IgG solutions by nanofiltration

BACKGROUND

Nanofiltration has proven to be an effective technology for virus removal. The small nonenveloped viruses, such as HAV and parvovirus B19 (B19), are evidently more difficult to remove than the larger enveloped viruses. However, since antibodies against these viruses, HAV and B19, are constantly present in large plasma pools, it is conceivable that antibody binding will lead to an increase in size of the viruses due to a corona of antibodies on the virus surfaces. These enlarged viruses should be easier to remove by nanofiltration than naked viruses. In this study, antibody-coated viruses and free virions were subjected to nanofiltration to determine whether the antibody-mediated increase in size contributes to the elimination of viruses which are otherwise too small to be retained by filters of a given nominal pore diameter.

STUDY DESIGN AND METHODS

One-percent IgG or 1-percent albumin solutions were spiked with bovine enterovirus (BEV) and filtered through 50-nm filters. This virus cross-reacts with antibodies in pooled human IgG solutions but persists as free virions in albumin solutions. Similarly, two parvoviruses, bovine parvovirus (BPV) and minute virus of mice (MVM), in 1-percent IgG solutions were filtered through 20-nm filters. BPV cross-reacts with antibodies in human IgG, whereas MVM remains unaffected. Virus removal was assessed by in vitro infectivity assays. Two methods were developed to displace the antibodies from BEV and BPV and thereby render them accessible for titration.

RESULTS

Antibody-coated BEV was eliminated to below detection limit by the 50-nm filters (logarithmic reduction factors [LRF] > or = 5), while free BEV virions passed without restraint through the same filters. Similarly, antibody-coated BPV was completely retained by the 20-nm filters (LRF > or = 5). MVM virions were strongly retained by the 20-nm filters; however, the virus was still detectable in the filtrate.

CONCLUSION

These results indicate that viruses with bound antibodies are efficiently eliminated by nanofiltration by use of filters having nominal pore sizes larger than the diameter of the respective free virions.

Combined calcium and vitamin D3 supplementation in elderly women: confirmation of reversal of secondary hyperparathyroidism and hip fracture risk: the Decalyos II study

Vitamin D insufficiency and low calcium intake contribute to increase parathyroid function and bone fragility in elderly people. Calcium and vitamin D supplements can reverse secondary hyperparathyroidism thus preventing hip fractures, as proved by Decalyos I. Decalyos II is a 2-year, multicenter, randomized, double-masked, placebo-controlled confirmatory study. The intention-to-treat population consisted of 583 ambulatory institutionalized women (mean age 85.2 years, SD = 7.1) randomized to the calcium-vitamin D3 fixed combination group (n = 199); the calcium plus vitamin D3 separate combination group (n = 190) and the placebo group (n = 194). Fixed and separate combination groups received the same daily amount of calcium (1200 mg) and vitamin D3 (800 IU), which had similar pharmacodynamic effects. Both types of calcium-vitamin D3 regimens increased serum 25-hydroxyvitamin D and decreased serum intact parathyroid hormone to a similar extent, with levels returning within the normal range after 6 months. In a subgroup of 114 patients, femoral neck bone mineral density (BMD) decreased in the placebo group (mean = -2.36% per year, SD = 4.92), while remaining unchanged in women treated with calcium-vitamin D3 (mean = 0.29% per year, SD = 8.63). The difference between the two groups was 2.65% (95% CI = -0.44, 5.75%) with a trend in favor of the active treatment group. No significant difference between groups was found for changes in distal radius BMD and quantitative ultrasonic parameters at the os calcis. The relative risk (RR) of HF in the placebo group compared with the active treatment group was 1.69 (95% CI = 0.96, 3.0), which is similar to that found in Decalyos I (RR = 1.7; 95% CI = 1.0, 2.8). Thus, these data are in agreement with those of Decalyos I and indicate that calcium and vitamin D3 in combination reverse senile secondary hyperparathyroidism and reduce both hip bone loss and the risk of hip fracture in elderly institutionalized women.

Virus inactivation and protein modifications by ethyleneimines

Virus inactivation by ethyleneimines was first introduced more than 30 years ago. Selective targeting of nucleic acids was reported for oligomeric ethyleneimines. In this study, trimeric ethyleneimine (TEI) was used to inactivate minute virus of mice (MVM; Parvoviridae) and Semliki forest virus (SFV; Togaviridae). The pH-dependency of the inactivation kinetics observed with MVM was different compared to the kinetics reported for other viruses. The higher inactivation rate at higher pH favoured the idea of a mechanism involving protein modifications. Alteration of the isoelectric point and changes in mass could be observed after treatment of soluble proteins with TEI. The uptake of MVM by host cells was reduced or completely blocked by TEI treatment, as shown by monitoring viral internalisation of DNA into target cells. The observed loss of virus infectivity coincided with the inhibition of virus uptake. Thus, virus inactivation by TEI is most likely also a result of chemical modifications of viral surface proteins.

Expression of Semliki Forest virus E1 protein in Escherichia coli. Low pH-induced pore formation

Exposure of Semliki Forest virus 1 to mildly acidic conditions results in conformational changes of the viral spike proteins, which in turn leads to a pore formation across its membrane. The ability to form a pore has been ascribed to the ectodomain of the Semliki Forest virus (SFV) E1 spike protein. To elucidate whether the E1 protein per se is sufficient for low pH-dependent pore formation, we expressed E1 in Escherichia coli in an inducible manner using the pET11c expression system. The data obtained clearly showed that the E1 protein was expressed in the bacterial cell membrane and that exposure of E. coli expressing the SFV E1 protein to low pH (<6.2) resulted in a permeability change of the membrane. Thus, we conclude that the E1 protein of SFV per se is sufficient to promote pore formation under mildly acidic conditions.

Virus inactivation of plasma-derived proteins by pasteurization in the presence of guanidine hydrochloride

BACKGROUND

Viruses, among them parvovirus B19 and other small, nonenveloped viruses, may be present in human blood and may contaminate plasma-derived therapeutics. Efficient inactivation or removal of such viruses, especially parvoviruses, represents a current problem and corresponding technologies are under investigation. In this report, such a technology is described.

STUDY DESIGN AND METHODS

A recently developed pasteurization of human apolipoprotein A-I (apoA-I), which is performed at 60 degrees C for 10 hours in the presence of guanidine hydrochloride (GdnHCl), was validated by using a series of model viruses, including members of the families parvoviridae and picornaviridae. The model viruses were spiked into the apoA-I- and GdnHCl-containing solutions, and virus inactivation was evaluated by infectivity assays in cell cultures. The mechanism of virus inactivation was studied by virus sedimentation analysis using the picornavirus model.

RESULTS

All viruses tested were inactivated to levels below the limit of detection, although different inactivation kinetics were obtained for the different viruses. The mechanism of virus inactivation by this pasteurization was disassembly of the virus particles into single proteins or small noninfectious viral subunits.

CONCLUSION

The pasteurization validated in this report has the potential to inactivate a wide range of transfusion-relevant viruses including parvoviruses and picornaviruses.

A randomized double-blind trial of intravenous trimetazidine as adjunctive therapy to primary angioplasty for acute myocardial infarction

BACKGROUND

Despite high patency rates, primary angioplasty for myocardial infarction does not necessarily result in optimal myocardial reperfusion and limitation of infarct size. Experimentally, trimetazidine limits infarct size, decreases platelet aggregation, and reduces leukocyte influx into the infarct zone. To assess trimetazidine as adjunctive therapy to primary angioplasty for acute myocardial infarction a prospective, double-blind, placebo-controlled pilot trial was performed.

METHODS

94 patients with acute myocardial infarction were randomized to receive trimetazidine (40 mg bolus followed by 60 mg/day intravenously for 48 h) (n=44) or placebo (n=50), starting before recanalization of the infarct vessel by primary angioplasty. Patients underwent continuous ST-segment monitoring to assess return of ST-segment deviation to baseline and presence of ST-segment exacerbation at the time of vessel recanalization. Infarct size was measured enzymatically from serial myoglobin measurements. Left ventricular angiography was performed before treatment and repeated at day 14.

RESULTS

Blinded ST segment analysis showed that despite higher initial ST deviation from baseline in the trimetazidine group (355 (32) vs. 278 (29) microV, P=0.07), there was an earlier and more marked return towards baseline within the first 6 h than in the placebo group (P=0.014) (change: 245 (30) vs. 156 (31) microV respectively, P=0.044). There was a trend towards less frequent exacerbation of ST deviation at the time of recanalization in the trimetazidine group (23.3 vs. 42.2%, P=0.11). There was no difference in left ventricular wall motion at day 14, or in enzymatic infarct size. There was no side effect from treatment. Clinical outcomes were similar between groups.

CONCLUSION

Trimetazidine was safe and led to earlier resolution of ST-segment elevation in patients treated by primary angioplasty for acute myocardial infarction.

Cleavage of incoming Semliki Forest virus capsid protein within the endocytotic pathway: a feature common to both invertebrate and mammalian cells

During the initial stages of Semliki Forest virus (SFV) infection in mammalian (baby hamster kidney, BHK) cells, the cleavage of SFV capsid protein could be detected. Analysis of subcellular fractions from SFV-infected BHK cells showed that (a) cleavage of the capsid protein occurred within a prelysosomal compartment of the endocytotic pathway, and (b) following release of the nucleocapsid into the cytoplasm, a 17.5 kD capsid protein fragment could be detected in the subcellular fraction which contained ribosomes. We have previously reported the cleavage of incoming SFV capsid protein in mosquito cells, too. Thus, the proteolytic cleavage of incoming SFV capsid protein is a feature which is common to both invertebrate and mammalian cells. These data further support our hypothesis that the cleavage of incoming capsid protein might provide the conformational change which primes the SFV nucleocapsid for uncoating.

Buckminsterfullerene and photodynamic inactivation of viruses

The development of new virus inactivation procedures has become an area of growing interest mainly due to increased demands concerning the safety of biological products. Photochemical processes represent the most promising methods for the future to inactivate viruses. In these methods, dyes are the most widely used photosensitising reagents. The current article covers a new interesting alternative, namely the use of buckminsterfullerene (C60). The unique properties of this molecule make it a valid candidate for future applications in the inactivation of viruses in biological fluids. Copyright 1998 John Wiley & Sons, Ltd.

Inactivation of enveloped viruses by singlet oxygen thermally generated from a polymeric naphthalene derivative

Inactivation of viruses can be induced by singlet oxygen generating agents. The water-insoluble polymeric compound PVNE (poly (1,4-dimethyl-6-vinylnaphthalene-1,4-endoperoxide)) is used as a storage for reactive oxygen and is able to produce thermally generated 1O2 in a dark-reaction. Enveloped viruses from two different families, Semliki Forest virus (SFV, Togaviridae) and vesicular stomatitis virus (VSV, Rhabdoviridae) showed a loss of infectivity of up to 8 log10/ml (TCID50) when incubated at 37 degrees C with PVNE in buffered solutions. PVNE produces singlet oxygen by thermal decomposition without irradiation. Such chemically generated oxygen excludes reactions involving radicals (type I photoreactions), a problem often encountered in photodynamic processes utilizing dyes as sensitizers. In addition, the water insolubility of the oxygen-carrier allows an easy removal and recycling from aqueous solutions. Therefore, it may prove useful in the inactivation of viruses in biological systems and may be a helpful tool in studies concerning the inactivation mechanism by 1O2.

Evaluation of haemorheological and microcirculatory disturbances in chronic venous insufficiency: activity of Daflon 500 mg

The use of Daflon 500 mg has been shown to improve venous tone, microvascular permeability, lymphatic activity, and microcirculatory nutritive flow. This study aimed to assess the effects of Daflon 500 mg at a daily dose of 2 tab/day on microcirculatory, haemorheologic parameters, white blood cell counts and neutrophil activation in patients suffering from chronic venous insufficiency (CVI). This was a single-centre double-blind placebo-controlled study comparing two parallel groups of CVI patients who were treated for 2 months with Daflon 500 mg (n = 39) or placebo (n = 38). Evaluations were performed before treatment (D0) and at the end of treatment (D60). Blood samples were drawn from a foot vein before and at the end of a 15-min period of venous hypertension provoked by a cuff inflated to 100 mm Hg. Red blood cell (RBC) deformability was determined by the initial flow rate filtration technique using a Hanss haemorheometer. RBC aggregation was evaluated by a Myrenne aggregometer based on analysis of transmitted light through a blood sample during flow. RBC disaggregation was evaluated by Sefam erythro-aggregometer based on analysis of the backscattered light through a blood sample in a Couette flow. Microcirculatory parameters were assessed by means of laser Doppler fluxmetry and transcutaneous oxymetry measurements and consisted of continuous records of blood flux (BF) and TcPO2 before and during 15 min of venous hypertension. Results are expressed as absolute values at baseline (before stasis) and at the end of stasis, before and after 2 months of treatment. Univariate analysis showed a significant reduction of the stasis-induced RBC aggregation index (Daflon 500 mg: -0.07+/-0.20; placebo: 0.04+/-0.18; mean +/- SD; p = 0.03). Multivariate analysis identified a subset of 5 variables (RBC aggregation, RBC count, microcirculatory BF, amplitude and frequency of vasomotion) that produced a good discrimination model between the two treatments. Linear combination of these 5 variables in 48 patients with complete data showed a significant difference (p < 0.001) between the groups. These changes suggest a protective effect of Daflon 500 mg on the deleterious influence of stasis on microcirculatory (BF) and hemorheologic (RBC aggregation) parameters in CVI patients in comparison to patients receiving placebo.

Characterisation of a chromatographically produced anti-D immunoglobulin product

A chromatographic fractionation method has been developed for the production of a liquid-stable anti-D immunoglobulin product for intravenous and intramuscular use. An immunoglobulin fraction, highly enriched with anti-D immunoglobulins, was isolated by cation-exchange column chromatography and further polished, first by anion-exchange chromatography, followed by an aluminium hydroxide gel treatment. The process includes two specific steps for virus inactivation and removal, namely S/D treatment and nanofiltration. The overall anti-D process yield is about 56%. The final product is stabilised with human albumin and glycine and placed in ready-to-use syringes. The anti-D product was shown to be stable in liquid state for at least 30 months at 4 degrees C.

Photodynamic inactivation of enveloped viruses by buckminsterfullerene

Photodynamic reactions induced by singlet oxygen-generating agents are known to inactivate enveloped viruses. In this report we demonstrate that the water-insoluble photosensitizer buckminsterfullerene (C60) can be used to mediate the inactivation of enveloped viruses. Viruses from two different families, Semliki Forest virus (SFV, Togaviridae) and vesicular stomatitis virus (VSV, Rhabdoviridae) were used as model systems. Buffered solutions containing C60 plus either of these viruses were illuminated with visible light for up to 5 h, resulting in a loss of infectivity of more than 7 log10/ml (TCID50). Furthermore, it was demonstrated that this viral inactivation was oxygen-dependent and equally efficient in solutions containing protein. C60 yields singlet oxygen in very high amounts and is completely inert to photo-oxidative destruction. In addition, it can be easily removed and recycled from aqueous solutions. For these reasons, it may prove useful in the inactivation of viruses in biological systems.

Low pH-induced pore formation by spike proteins of enveloped viruses

Exposure of Aedes albopictus cells infected with Semliki Forest virus (SFV; Togaviridae) to mildly acidic pH (5.6) results in a dramatic increase in the host cell membrane permeability due to pore formation by the virus spike proteins. Identical results were obtained when the cells were infected with two other viruses, Sindbis virus (SIN, Togaviridae) and vesicular stomatitis virus (VSV, Rhabdoviridae). This permeability change could also be observed on isolated virions of SFV, SIN and VSV by measuring the influx of propidium iodide, a nucleic acid-specific fluorescent marker, into the virions. This influx was dependent on the presence of the ectodomains of the viral spikes and could be hampered by zinc ions. Furthermore, haemagglutinin, a membrane protein of influenza A virus (Orthomyxoviridae), expressed in Aedes cells induced a change in membrane permeability identical to that induced by the spike proteins of SFV, SIN and VSV when exposed to low pH. Thus acid-induced membrane permeability changes produced by spike proteins of three different virus families could be demonstrated in infected cells as well as in virions. Therefore, the low pH-induced pore formation by viral spike proteins seems to be more than an event specific for togaviruses and might well be an inherent property of enveloped viruses that use the endocytotic pathway to infect a cell.

Virus inactivation by pepsin treatment at pH 4 of IgG solutions: factors affecting the rate of virus inactivation

BACKGROUND

IgG preparations have rarely transmitted infectious diseases; however, because such transmission has occurred a few times, manufacturers are required to present experimental proof that their specific production process removes and/or inactivates viruses that may be present in the starting material.

STUDY DESIGN AND METHODS

The kinetics of virus inactivation mediated by pepsin treatment at pH 4 during the production of intravenous immunoglobulin was assessed with spiking experiments using human immunodeficiency virus, bovine viral diarrhea virus, Semliki Forest virus, and pseudorabies virus. The influence of various factors on the rate of virus inactivation also was studied by modifying the composition of the IgG solutions with respect to IgG, sucrose, and NaCl content.

RESULTS

Virus inactivation at 37 degrees C was extremely rapid and resulted in a complete loss of infectivity within 5 minutes to 1 hour. Inactivation was much slower at lower temperatures. Furthermore, inactivation was dependent on the solute composition. Increasing the sucrose content from 0 to 15 percent reduced the rate of inactivation of pseudorabies virus but did not affect the rate of inactivation of Semliki Forest virus. In contrast, increasing the NaCl content from 0 to 150 mM resulted in a reduction in the rate of inactivation of Semliki Forest virus, whereas the rate of inactivation of pseudorabies virus remained unaffected. Moreover, increasing the IgG concentration from 0 to 10 percent resulted in an increased rate of inactivation of pseudorabies virus but a decreased rate of inactivation of Semliki Forest virus.

CONCLUSION

Inactivation of viruses by pepsin treatment at pH 4 essentially is temperature-dependent, and the reaction rate is selectively influenced by the solute composition of the IgG solution. This has to be taken into account when safety data for different products are compared.

The fragmentation of incoming Semliki Forest virus nucleocapsids in mosquito (Aedes albopictus) cells might be coupled to virion uncoating

The fate of Semliki Forest virus (SFV) nucleocapsid, especially the capsid protein (C-protein), was investigated during the early stages of a productive infection in mosquito Aedes albopictus cells. Infection of the cells resulted in a time dependent accumulation of a C-protein derived fragment. This fragmentation of incoming viral nucleocapsid was prevented by NH4Cl, an agent generally used to elevate the pH in acidic intracellular compartments, suggesting that a low intravesicular pH is required for this process. Density gradient analysis of the postnuclear cell lysate demonstrated that the fragmentation was associated with a cellular compartment showing a density of 1.14 +/- 0.02 g/ml. This cellular compartment was devoid from a lysosomal marker enzyme and represented the timely preceding cellular fraction through which SFV passed before encountering a lysosomal fraction. Furthermore, the intracellular distribution of the viral, 3H-uridine-labeled RNA suggested that the same fraction might represent a key cellular compartment in which the separation of the viral RNA from the viral structural proteins is primed. In conclusion, these data lead to the suggestion that the fragmentation of incoming SFV nucleocapsids in Aedes albopictus cells might be the part of the mechanism leading to the release of viral RNA into the cytosol during early stages of productive infection.

The E1 protein is mandatory for pore formation by Semliki Forest virus spikes

Insect cells (Aedes albopictus, clone C6/36) were infected with various variants of Semliki Forest virus including the wild type using the SFV replicon system. The variants included deletion mutants lacking one of the structural proteins and a mutant with a point mutation in p62 (SQL). The latter mutation results in a failure to process p62 to E2 and E3. After infection of the cells with different variant viruses and subsequent expression of viral proteins in the host cell plasma membrane low pH-induced pore formation was detected by measuring the efflux of a radiolabeled compound. The results of these experiments clearly showed that the E1 protein is mandatory for the acid-induced pore formation. A participation of the 6K or C-protein could be excluded. Furthermore, results obtained with the SQL mutant suggest that dissociation of the E1/E2 heterodimer and subsequent homooligomerization of E1 are required for pore formation.

Identification of the pore forming element of Semliki Forest virus spikes

Pore formation at mildly acidic pH by SFV spike proteins was investigated using isolated and modified virions. Modification of the virions was performed by limited proteolysis in presence of octylglucoside and resulted in the formation of E1 particles and spikeless particles, respectively. Pore formation was detected by measuring the influx of propidium iodide into the viral particles. The results obtained clearly showed that the presence of E1 alone is sufficient to promote pore formation at mildly acidic pH. Thus E1 represents the pore forming element of the viral spike proteins.

Entry and uncoating of enveloped viruses

Images

Modulation of thermoprotection and translational thermotolerance induced by Semliki Forest virus capsid protein

Low amounts of Semliki Forest virus capsid protein transferred into target cells by electroporation-mediated delivery (10(3)-10(4) molecules incorporated/cell) confer thermal resistance resulting in enhanced survival. Furthermore, when exposed to 43 degrees C, these cells display an enhanced expression of heat-shock protein-70 and a translational thermotolerance. Similarly, low amounts of capsid protein transferred into cells in which transcription is blocked by actinomycin D, also protect the translational machinery at 43 degrees C. In a cell-free translation system, added capsid protein appears to modulate translational efficiency of endogenous mRNAs. At approximately 1 molecule/ribosome, capsid protein is able to enhance translation at 30 degrees C and at 43 degrees C. In contrast, high concentrations of capsid protein are responsible for a marked inhibition of protein synthesis at 30 degrees C, but only hamper translational thermotolerance at 43 degrees C. Our results favor the hypothesis that small amounts of capsid protein trigger a chaperone-like activity that is able to protect the translational machinery from thermal damage.

Semliki Forest virus core protein fragmentation: its possible role in nucleocapsid disassembly

Semliki Forest virus (SFV) envelope proteins function as proton pores under mildly acidic conditions and translocate protons across the viral membrane [Schlegel, A., Omar, A., Jentsch, P., Morell, A. and Kemp, F. C. (1991) Biosci. Rep. 11, 243-255]. As a consequence, during uptake of SFV by cells via receptor-mediated endocytosis the nucleocapsid is supposed to be exposed to protons. In this paper the effects of mildly acidic pH on SFV nucleocapsids were examined. A partial proteolytic fragmentation of core proteins was observed when nucleocapsids were exposed to mildly acidic pH. A similar proteolytic event was detected when intact SFV virions were exposed to identical conditions. Protease protection assays with exogenous bromelain provided evidence that the capsid protein degradation was due to an endogenous proteolytic activity and not to a proteolytic contamination. Detergent solubilization of virus particles containing degraded nucleocapsids followed by sucrose gradient centrifugation led to a separation of capsid protein fragments and remaining nucleocapsids. These data are discussed in terms of a putative biological significance, namely that the core protein fragmentation may play a role in nucleocapsid disassembly.

Early events of Semliki Forest virus-induced cell-cell fusion

Insect cells (Aedes albopictus) were infected with Semliki Forest Virus. Cell-cell fusion was then induced by lowering the extracellular pH. The underlying processes were examined by monitoring the intercellular current flow, Ij. Experimentally, this involved the use of cell pairs in conjunction with a dual voltage-clamp method. This approach allowed us to monitor the kinetics of fusion at high temporal resolution. The fusion process began shortly after acidification (delay: 3-138 sec). Initially, Ij increased in a stepwise manner, later on it developed more gradually. Fusion between two cells reached a steady state within 7-70 sec. The steps in Ij are attributable to the formation of cytoplasmic connections between the cells, presumably involving proteinaceous fusion pores. The mean amplitude of Ij steps corresponds to a conductance of 300 pS, consistent with a pore radius of 1 nm. Cytoplasmic connections developed rapidly, i.e., Ij steps occurred within less than 1 msec. The absence of Ij flickering implies that formation of cytoplasmic connections, and hence SFV induced cell-cell fusion, is irreversible.

A comparative study of the effect of dextran sulfate on the fusion and the in vitro replication of influenza A and B, Semliki Forest, vesicular stomatitis, rabies, Sendai, and mumps virus

The effect of dextran sulfate on the fusion of a series of enveloped viruses, bearing specifically different fusion proteins, was investigated. The fusion with model- and with biological membranes was monitored by an R18 fluorescence-dequenching fusion assay. Dextran sulfate strongly suppresses the fusion of orthomxyo- (influenza A (H1N1 and H3N2 subtypes) and influenza B), of toga- (Semliki Forest virus), and of rhabdoviruses (vesicular stomatitis and rabies virus). The fusion of the paramyxo-viruses Sendai and mumps was not significantly affected by the anionic polysaccharide. The response to dextran sulfate was virus-specific, and identical for the different members of one virusfamily, bearing the same fusion protein. It was shown that dextran sulfate attaches with high affinity to the viruses studied, but not to erythrocytes. The anionic polymer appears to attach to the fusion epitope of the viral membrane. The inhibition of virus replication in vitro shows a remarkable correlation with the observed anti-fusion effects of dextran sulfate.

pH-dependent pore formation in Semliki forest virus-infected Aedes albopictus cells

The plasma membrane properties of Semliki forest virus-infected Aedes cells were studied using whole-cell patch-clamp recording. Cells exhibited a marked increase in membrane conductance, gm (from 0.48 +/- 0.09 nS to 14.2 +/- 10.8 nS) upon exposure to acidic pH (5.6). The membrane potential depolarized from -40.9 +/- 5.2 mV to -2.43 +/- 7.14 mV under these conditions. In uninfected cells, there was no change in gm after lowering the pH. This implies that viral fusion proteins are involved in changing the membrane properties at low pH. The increased gm in infected cells at low pH was not persistent but declined within minutes. Millimolar concentrations of calcium and zinc prevented or reverted the increase in gm. The results suggest that viral proteins, if brought to their fusogenic conformation by exposure to low pH, form unspecific pores in the residing membrane. These pores might play a role in virus entry.

Arachidonic acid and other unsaturated fatty acids alter membrane potential in PC12 and bovine adrenal chromaffin cells

The action of arachidonic acid and other fatty acids on membrane potential in PC12 and bovine chromaffin cells was investigated using a membrane potential-sensitive fluorescent dye. Arachidonic acid (1-40 microM) provoked dose-dependent membrane hyperpolarization, thereby reducing hyperpolarization induced by the K(+)-selective ionophore valinomycin. Other cis-unsaturated fatty acids, but not lipoxygenase products or the saturated fatty acid palmitic acid, also affected membrane potential. Tetraethylammonium blocked the arachidonic acid-induced hyperpolarization. These data suggest that cis-unsaturated fatty acids alter membrane potential in PC12 and bovine chromaffin cells by modulating K+ conductances. Valinomycin-generated hyperpolarization had no effect on agonist-induced Ca2+ influx into bovine chromaffin cells, whereas preincubation with arachidonic acid and other cis-unsaturated fatty acids blocked Ca2+ influx and secretion. We propose a model where internally generated fatty acids act as a feedback to desensitize the stimulated cell via inhibition of receptor-dependent Ca2+ influx and induction of membrane hyperpolarization.

Cytoplasmic bridges and gap junctions in an insect cell line (Aedes albopictus)

Cell pairs of an insect cell line (Aedes albopictus, clone C6/36) were used study simultaneously the diffusional and electrical properties of intercellular junctions. Diffusion studies involved injection of fluorescent molecules into one cell of a cell pair and visual inspection of their intercellular redistribution. Electrical measurements involved a dual voltage clamp method and whole-cell recording with patch pipette. The voltage clamp protocol was aimed at examining the dependency of the junctional conductance, gj, on membrane potential, Vm. Cell pairs exhibiting a voltage-dependent gj were found to allow intercellular diffusion of Lucifer Yellow CH (molecular mass, 443 Da), but not of FITC-dextran (molecular mass, 4,400 Da). This response pattern is consistent with the presence of gap junctions in the intercellular junctions. Cell pairs showing no voltage dependence of gj were found to permit intercellular diffusion of both Lucifer Yellow CH and FITC-dextran (dextran labelled with fluorescein isothiocyanate). This behaviour is compatible with the presence of cytoplasmic bridges connecting the two adjacent cells. Hence, in culture the cells investigated express two kinds of intercellular structures, gap junctions and cytoplasmic bridges.

Changes in membrane permeability during Semliki Forest virus induced cell fusion

The infection of Aedes albopictus cells by Semliki Forest virus (SFV) is a non lytic event. Exposure of infected cells to mildly acidic pH (less than 6.2) leads to syncytium formation. This polykaryon formation is accompanied by an influx of protons into the cells (Kempf et al. Biosci. Rep. 7, 761-769, 1987). We have further investigated this permeability change using various fluorescent or radiolabeled compounds. A significant, pH dependent increase of the membrane permeability to low molecular weight compounds (M(r) less than 1000) was observed when infected cells were exposed to a pH less than 6.2. The pH dependence of the permeability change was very similar to the pH dependence of cell-cell fusion. The permeability change was sensitive to divalent cations, protons and anionic antiviral drugs such as trypan blue. The nature of this virus induced, pH dependent permeability change is discussed.

Electrical coupling between cells of the insect Aedes albopictus

1. Cell pairs of an insect cell line (Aedes albopictus, clone C6/36) were used to study the electrical properties of intercellular junctions. A double voltage-clamp approach was adopted to control the voltage gradient between the cells and measure the intracellular current flow. 2. Determinations of junctional conductance (gj) revealed two types of intercellular contacts, gap junctions and cytoplasmic bridges. Identification occurred by means of functional criteria, i.e. the dependency of gj on (i) junctional membrane potential, (ii) non-junctional membrane potential, and (iii) heptanol. 3. In cell pairs with putative gap junctions, gj was dependent on the junctional membrane potential (Vj). When determined at the beginning of voltage pulses, gj was insensitive to Vj; when determined at the end of 15 s pulses, it depended on Vj in a bell-shaped manner (70% decrease for a change in Vj of +/- 75 mV). 4. These cell pairs also showed a dependency of gj on the non-junctional membrane potential (Vm). When determined immediately after changing the non-junctional membrane potential in both cells, gj was not affected by Vm; when determined 30 s later, gj was modified by Vm in a S-shaped fashion (100% decrease when Vm was depolarized to +50 mV). 5. Exposure to 3 mM-heptanol gave rise to complete and reversible block of gj in cell pairs with putative gap junctions. 6. Cell pairs susceptible to uncoupling by heptanol revealed junctional currents indicative of the operation of gap junction channels. The single-channel conductance, determined at a Vm of -50 to -70 mV, was 133 pS. 7. In the case of putative cytoplasmic bridges, gj was insensitive to the junctional and non-junctional membrane potential. In addition, it was not affected by 3 mM-heptanol. 8. While most cell pairs showed functional properties characteristic of gap junctions or cytoplasmic bridges, few cell pairs exhibited junctional currents compatible with the co-existence of both junctional structures.