US develops lethal new viruses
19:00 29 October 03
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A scientist funded by the US government has deliberately created an extremely deadly form of mousepox, a relative of the smallpox virus, through genetic engineering.
The new virus kills all mice even if they have been given antiviral drugs as well as a vaccine that would normally protect them.
The work has not stopped there. The cowpox virus, which infects a range of animals including humans, has been genetically altered in a similar way.
The new virus, which is about to be tested on animals, should be lethal only to mice, Mark Buller of the University of St Louis told New Scientist. He says his work is necessary to explore what bioterrorists might do.
But the research brings closer the prospect of pox viruses that cause only mild infections in humans being turned into diseases lethal even to people who have been vaccinated.
And vaccines are currently our main defence against smallpox and its relatives, such as the monkeypox that reached the US this year. Some researchers think the latest research is risky and unnecessary.
"I have great concern about doing this in a pox virus that can cross species," said Ian Ramshaw of the Australian National University in Canberra on being told of Buller's work.
Ramshaw was a member of the team that accidentally discovered how to make mousepox more deadly (New Scientist, 13 January 2001). But the modified mousepox his team created was not as deadly as Buller's.
No rebound
Since then, Ramshaw told New Scientist, his team has also created more deadly forms of mousepox, and has used the same method to engineer a more deadly rabbitpox virus.
But this research revealed that the modified pox viruses are not contagious, he says. That is good news in the sense that these viruses could not cause ecological havoc by wiping out mouse or rabbit populations around the world if they escaped from a lab.
However, this discovery also means some bioterrorists might be more tempted to use the same trick to modify a pox virus that infects humans. Such a disease, like anthrax, would infect only those directly exposed to it. It would not spread around the world and rebound on the attackers. But there is no guarantee that other pox viruses modified in a similar way would also be non-contagious.
Ramshaw's team made its initial discovery while developing contraceptive vaccines for sterilising mice and rabbits without killing them. The researchers modified the mousepox virus by adding a gene for a natural immunosuppressant called IL-4, expecting this would boost antibody production.
Instead, the modified mousepox virus was far more lethal, killing 60 per cent of vaccinated mice. The addition of IL-4 seems to switch off a key part of the immune system called the cell-mediated response.
Maximised production
Now Buller has engineered a mousepox strain that kills 100 per cent of vaccinated mice, even when they were also treated with the antiviral drug cidofovir. A monoclonal antibody that mops up IL-4 did save some, however.
His team "optimised" the virus by placing the IL-4 gene in a different part of the viral genome and adding a promoter sequence to maximise production of the IL-4 protein, he told a biosecurity conference in Geneva last week.
Buller has also constructed a cowpox virus containing the mouse IL-4 gene, which is about to be tested on mice at the US Army Medical Research Institute of Infectious Diseases at Fort Detrick, Maryland.
Cowpox infects people, but Buller says the IL-4 protein is species-specific and would not affect the human immune system. The experiments are being done at the second-highest level of biological containment.
Nine-eleven
Ramshaw says there is no reason to do the cowpox experiments, as his group's work on rabbits has already shown the method works for other pox viruses. While viruses containing mouse IL-4 should not be lethal to humans, recombinant viruses can have unexpected effects, he says. "You'd hope the combination remains mouse-specific."
Why his group's engineered viruses are not contagious is a mystery, he says. It is not, for instance, because the host dies faster than usual, taking the virus with it. But his findings could explain why pox viruses containing IL-4 have never evolved naturally, even though the viruses frequently pick up genes that affect their host's immunity.
Despite the concerns, work on lethal new pox viruses seems likely to continue in the US. When members of the audience in Geneva questioned the need for such experiments, an American voice in the back boomed out: "Nine-eleven". There were murmurs of agreement.
Debora MacKenzie, Geneva
Sound-detecting hair cells grown in lab
22:00 27 October 03
NewScientist.com news service
The sound-detecting hair cells of the inner ear can be grown in the lab from embryonic stem cells, US scientists have shown. The work raises another possible alternative to cochlear implants for treating deafness.
Hair cells convert sound waves into electrical signals that go to the brain. In mammals including humans, these cells die off with age. The result is irreversible hearing loss.
Stefan Heller's team at the Massachusetts Eye and Ear Infirmary in Boston generated the hair cells by exposing mouse embryonic stem cells - which are capable of turning into any type of cell - to the chemical factors that a normal hair cell would encounter.
To see if these lab-grown cells would make themselves at home in a developing ear, Heller transplanted partially developed cells into chicken embryos. The cells continued to develop, behaving just like the hair cells the chicken already had.
Neural connection
However, while the cells look normal, Heller does not yet know if the lab-grown hair cells will function like the cells that developed in an animal. His next step is to see if cell transplants can restore hearing in hard-of-hearing mice.
One encouraging sign is that the stem cells formed connections with neurons in the same petri dish, a crucial characteristic of hair cells in an animal.
Another group has shown that gene therapy can turn other inner ear cells into hair cells (New Scientist print edition, 7 June 2003).
The advantage of using embryonic stem cells is that great numbers of hair cells could be grown says Yehoash Raphael, a hair cell expert at the University of Michigan Medical Center. However, unlike gene therapy, there could be problems with immune system rejection of transplanted cells.
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.2334503100)
Emily Singer
Mortality Rates Lower for Breast Cancers Linked to HRT Use
NEW YORK (Reuters Health) Oct 23 - The risk of invasive lobular carcinoma (ILC), the type of breast cancer most commonly associated with use of combined hormone replacement therapy, has increased over the last three decades. However, the prognosis for ILC has improved relative to that of invasive ductal carcinoma, the most common type.
The results of previous studies that compared the prognoses of different histologic types of breast cancer have been inconsistent, note Dr. Christopher I. Li, at the Fred Hutchinson Cancer Research Center in Seattle, and colleagues. But few studies have been population based, and the studies included relatively small numbers of cases with rare histological types.
To further clarify the prognoses of different types, Dr. Li's group conducted a retrospective cohort study using data from the nine cancer registries of the Surveillance, Epidemiology and End Results (SEER) program. Included were nearly 165,000 women ages 59 to 79 years old when diagnosed with a primary invasive breast cancer between 1974 and 1998.
Approximately 80% had ductal, 12% had lobular and 2.4% had mucinous carcinomas, they report in the October 13th issue of the Archives of Internal Medicine. Between 0.6% and 1.9% had comedocarcinomas, medullary, tubular or papillary carcinomas. Only the number of cases of medullary carcinoma declined over the course of the study.
After adjusting for age and year of diagnosis, SEER historic stage and category, and treatment (surgical and/or radiation), the prognosis remains the worst for women with invasive ductal carcinoma. Mortality rate declined the most for women with tubular carcinomas (34%).
Between 1994 and 1998, the risk of mortality associated with mucinous carcinoma and invasive lobular carcinoma dropped 31% and 26%, respectively, compared with women with invasive ductal carcinoma. Dr. Li and associates suggest that improved survival may be due to changes in hormonal therapy and chemotherapy.
"It appears that the types of breast carcinomas combined HRT users have a greater risk of developing, such as invasive lobular carcinoma, have a relatively favorable prognosis," they conclude.
Arch Intern Med 2003;163:2149-2153.
Mortality Rates Lower for Breast Cancers Linked to HRT Use
NEW YORK (Reuters Health) Oct 23 - The risk of invasive lobular carcinoma (ILC), the type of breast cancer most commonly associated with use of combined hormone replacement therapy, has increased over the last three decades. However, the prognosis for ILC has improved relative to that of invasive ductal carcinoma, the most common type.
The results of previous studies that compared the prognoses of different histologic types of breast cancer have been inconsistent, note Dr. Christopher I. Li, at the Fred Hutchinson Cancer Research Center in Seattle, and colleagues. But few studies have been population based, and the studies included relatively small numbers of cases with rare histological types.
To further clarify the prognoses of different types, Dr. Li's group conducted a retrospective cohort study using data from the nine cancer registries of the Surveillance, Epidemiology and End Results (SEER) program. Included were nearly 165,000 women ages 59 to 79 years old when diagnosed with a primary invasive breast cancer between 1974 and 1998.
Approximately 80% had ductal, 12% had lobular and 2.4% had mucinous carcinomas, they report in the October 13th issue of the Archives of Internal Medicine. Between 0.6% and 1.9% had comedocarcinomas, medullary, tubular or papillary carcinomas. Only the number of cases of medullary carcinoma declined over the course of the study.
After adjusting for age and year of diagnosis, SEER historic stage and category, and treatment (surgical and/or radiation), the prognosis remains the worst for women with invasive ductal carcinoma. Mortality rate declined the most for women with tubular carcinomas (34%).
Between 1994 and 1998, the risk of mortality associated with mucinous carcinoma and invasive lobular carcinoma dropped 31% and 26%, respectively, compared with women with invasive ductal carcinoma. Dr. Li and associates suggest that improved survival may be due to changes in hormonal therapy and chemotherapy.
"It appears that the types of breast carcinomas combined HRT users have a greater risk of developing, such as invasive lobular carcinoma, have a relatively favorable prognosis," they conclude.
Arch Intern Med 2003;163:2149-2153.
CDC Issues Guidelines on Temperatures for Vaccine Storage
NEW YORK (Reuters Health) Oct 23 - In an effort to ensure optimal vaccine efficacy, the US Centers for Disease Control and Prevention released guidelines on Thursday regarding correct storage temperatures.
The report, which is published in the October 24th issue of the CDC's Morbidity and Mortality Weekly Report, also describes appropriate storage units, proper temperature-monitoring practices, and steps for evaluating a temperature-monitoring program.
Most vaccines should be stored at temperatures between 2 and 8 degrees Celsius and should not be exposed to freezing temperatures. The exceptions are live attenuated influenza vaccine and varicella vaccine, which should be frozen with no freeze-thaw cycles.
Storing vaccines at temperatures that are too high or low can irreversibly reduce their potency, the CDC notes. State or local health departments or the vaccine manufacturer should be contacted for guidance if storage temperatures fall outside the recommended range.
In terms of storage units, standard refrigerator/freezer combos are suitable for vaccine storage if each compartment has a separate door. Still, more precise temperature control is probably achieved with stand-alone refrigerator and freezer units, the report indicates.
Standard fluid-filled, min-max, and continuous chart recorder thermometers can all be used for temperature monitoring and each has unique pros and cons. Regardless of which type is selected, it "should be calibrated and certified by an appropriate agency."
The CDC recommends the following procedures for clinicians who administer vaccines:
--Have personnel trained in vaccine storage with written duties
--Use accurate thermometers with proper positioning in storage units
--Make sure vaccines are properly stored in the correct unit
--Keep temperature logs for the storage units
--Immediately address any out-of-range temperature problems
--Contact health officials or the vaccine maker for out-of-range temperatures
--Have a storage back-up plan in case of power outages or equipment failures.
Mor Mortal Wkly Rep CDC Surveill Summ 2003;52:1023-1025.
EU Warns on Triple Nucleoside/Nucleotide Reverse Transcriptase Inhibitors
By Richard Woodman
LONDON (Reuters Health) Oct 22 - The European Medicines Agency on Wednesday advised doctors not to start HIV patients on the drug combination of didanosine (Videx; BMS), lamivudine (Epivir; GSK) and tenofovir (Viread; Gilead Sciences).
In a statement on its Web site, the agency said a high rate of virologic failure (91%) has been observed in a clinical study of treatment-nave patients on this once-daily triple drug combination.
As a precautionary measure, it said: "Tenofovir in combination with didanosine and lamivudine should not be used when considering a new treatment regimen for therapy-nave or experienced patients with HIV infection and particularly as a once-a-day regimen.
"Any patient controlled on therapy with this combination should be frequently monitored with a sensitive viral load test and considered for modification of therapy at the first sign of viral load increase."
In July, the agency issued a similar warning about a slightly different triple combination containing tenofovir, abacavir (Ziagen; GSK) and lamivudine after a study found that nearly half of patients on this regimen failed to respond.
In both cases, the precise nature of any interaction leading to non-response remains a mystery and the agency has asked the companies to investigate.
Single-Dose Azithromycin Effective in Travelers' Diarrhea CME
News Author: Laurie Barclay, MD
CME Author: Désirée Lie, MD, MSEd
Authors and Disclosures
To earn CME credit, read the news brief, the paragraphs that follow, and answer the questions below.
Release Date: October 23, 2003; Valid for credit through October 23, 2004
Credits Available
Physicians - up to 0.25 AMA PRA category 1 credit(s)
Oct. 23, 2003 — Single-dose azithromycin is as effective as single-dose levofloxacin for travelers' diarrhea, according to the results of a randomized, placebo-controlled, double-blind trial published in the Nov. 1 issue of Clinical Infectious Diseases.
"Increased drug resistance among enteropathogens is an emergent problem in travelers' diarrhea," write Javier A. Adachi, from the University of Texas-Houston School of Public Health and Medical School, and colleagues. "Azithromycin, an azalide, has a long half-life and achieves a high intracellular concentration. It has excellent in vitro activity against common bacterial enteric pathogens."
During the summers of 1999 to 2001, 217 U.S. adults with travelers' diarrhea acquired in Guadalajara, Mexico, were randomized to receive a single oral dose of 1,000 mg azithromycin or 500 mg levofloxacin. Over a follow-up period of four days, three patients in each group dropped out of the study.
Both groups had similar median time between initiation of therapy and passage of the last unformed stool (22.3 hours for azithromycin vs. 21.5 hours for levofloxacin) and number of unformed stools passed during the four-day follow-up period (6.5 vs. 5.5). Treatment failed in 10 patients (9.5%) receiving azithromycin and in eight patients (7.5%) receiving levofloxacin. In each group, 57 patients had possible minor, self-limiting adverse events.
"Azithromycin was found to be a safe and effective alternative to levofloxacin for the treatment of acute travelers' diarrhea in US adult travelers to Mexico," the authors write. "Single-dose therapy offers three advantages to international travelers for self-treatment of diarrhea: ease of administration, improved compliance, and lower cost. Azithromycin has additional safety considerations. It is already approved for other uses in children, and it is a category B drug in pregnancy, both of which are contraindications for fluoroquinolones."
Pfizer helped support this study and employs one of its authors.
Clin Infect Dis. 2003;37:1165-1171
Penicillin Allergy Better Predictor Than Sulfonamide Antibiotic Allergy of Sulfonamide Nonantibiotic Allergy CME
News Author: Laurie Barclay, MD
CME Author: Charles Vega, MD
Authors and Disclosures
To earn CME credit, read the news brief, the paragraphs that follow, and answer the questions below.
Release Date: October 22, 2003; Valid for credit through October 22, 2004
Credits Available
Physicians - up to 0.25 AMA PRA category 1 credit(s)
Oct. 22, 2003 — Penicillin allergy is a better predictor than sulfonamide antibiotic allergy of sulfonamide nonantibiotic allergy, according to the results of a retrospective cohort study published in the Oct. 23 issue of the New England Journal of Medicine. The editorialist praises the study and emphasizes the need for more research on drug-induced allergic reactions.
"The safety of sulfonamide nonantibiotics is unclear in patients with prior allergic reactions to sulfonamide antibiotics," write Brian L. Strom, MD, MPH, from the University of Pennsylvania School of Medicine in Philadelphia, and colleagues. "Although the mechanism of sulfonamide-related reactions is poorly understood, patients who have had a reaction after taking a sulfonamide are thought to be at increased risk for another reaction, and all sulfonamides are considered contraindicated in those with a history of sulfa allergy."
Using the U.K. General Practice Research Database, the authors determined the risk of allergic reactions within 30 days after receipt of a sulfonamide nonantibiotic.
Of 969 patients with a history of allergic reaction to a sulfonamide antibiotic, 96 (9.9% had an allergic reaction after subsequently receiving a sulfonamide nonantibiotic. Of 19,257 patients who had no history of allergic reaction to a sulfonamide antibiotic, 315 (1.6%) had an allergic reaction after receiving a sulfonamide nonantibiotic (adjusted odds ratio [OR], 2.8; 95% confidence interval [CI], 2.1 - 3.7).
Among patients with a prior hypersensitivity reaction to a sulfonamide antibiotic, the risk of allergic reactions was even greater after receiving a penicillin compared with patients with no such history (adjusted OR, 3.9; 95% CI, 3.5 - 4.3). Among those with a prior hypersensitivity reaction to a sulfonamide antibiotic, the risk of an allergic reaction after the subsequent receipt of a sulfonamide nonantibiotic was lower than the risk of an allergic reaction after the subsequent receipt of a penicillin (adjusted OR, 0.7; 95% CI, 0.5 - 0.9).
The risk of an allergic reaction after receiving a sulfonamide nonantibiotic was lower among patients with a history of hypersensitivity to sulfonamide antibiotics than among patients with a history of hypersensitivity to penicillins (adjusted OR, 0.6; 95% CI, 0.5 - 0.8).
Possible study limitations include information bias, diagnostic suspicion bias, outcome misclassification, selection bias, and potential confounders.
"There is an association between hypersensitivity after the receipt of sulfonamide antibiotics and a subsequent allergic reaction after the receipt of a sulfonamide nonantibiotic, but this association appears to be due to a predisposition to allergic reactions rather than to cross-reactivity with sulfonamide-based drugs," the authors write. "Prescribers should understand that patients with a history of allergic reactions to drugs may be at increased risk for all drug-induced adverse events that appear to be allergic in nature."
Pfizer supported this study and employs one of its authors.
In an accompanying editorial, Wayne A. Ray, PhD, notes the important clinical implications of this study and questions why has it taken nearly 50 years to obtain data from controlled studies on cross-reactivity.
"Ultimately, progress in detecting and quantifying adverse drug effects may be determined more by the priorities of society than by technological capacity," he writes. "Some of the barriers to funding post-marketing studies are the severely limited resources of the Food and Drug Administration for monitoring a drug after it is marketed, the perception by sources at the National Institutes of Health that these clinical studies may not be scientifically innovative or should be funded by the pharmaceutical industry, and disincentives for the industry itself to conduct these studies.... The importance of basing clinical practice on accurate information about the effects of drugs demands that we put forth even greater efforts in the future."
N Engl J Med. 2003;349:1592-1594, 1628-1635
Measuring Estradiol Levels Recommended for Women Treated With HRT
Mindy Hung
Oct. 22, 2003 — Analysis of data from the Postmenopausal Health Disparities Study (PHDStudy) suggests that estradiol (E2) levels should be monitored and hormone replacement therapy (HRT) adjusted accordingly. Results were published in the October issue of the Journal of Women's Health.
"The current report is the first to systematically address the issue of individualizing [estrogen replacement therapy] using data from a multi-racial multi-ethnic study, in which hormone levels were assayed using identical methods in both controls and women treated with oral or patch HRT by their own healthcare providers," writes Judith S. Gavaler, PhD, from the University of Pittsburgh in Pennsylvania.
"The creation of logical HRT-response categories based on the mean and standard deviation of E2 levels in the controls (women not using [estrogen replacement therapy]) as a way to differentiate the responses to HRT is a novel approach, which has been demonstrated to be useful in revealing the spectrum of estradiol levels actually achieved," she adds.
Dr. Gavaler obtained data from 616 postmenopausal patients in the PHDStudy, which was performed in Oklahoma City between 1993 and 1999 and has been continuing in Pittsburgh. The majority of these women were drawn from minority groups.
Two hundred ninety-one untreated postmenopausal women formed the control group. Three hundred twenty-five women were being treated with HRT by their own clinicians with oral or patch HRT preparations.
The author included women who had at least one full year since the last episode of menstrual bleeding or bilateral ovariectomy. Menopausal status was confirmed by a follicle-stimulating hormone/luteinizing hormone ratio greater than a value of one.
Dr. Gavaler excluded women who had unstable disease of any major organ system, or a history of or current cancer or alcoholism. Thirty-three women who were being treated with birth control regimens or monthly estrogen shots were also disqualified from study because the two treatment modalities precluded the achievement of a steady state in hormone levels.
The researcher based response categories for the E2 levels achieved in HRT-treated women on average and standard deviation (SD) in the untreated control women. The response categories ranged from the control mean -1 SD to the control mean 6 SD.
Participants filled out questionnaires on demographics, gynecologic history, menopausal symptomatology, details of HRT use, medical conditions, medications (including supplements and other over-the-counter agents), fitness and exercise, health behaviors, and dietary frequencies. In addition, investigators obtained three-day food records and the Tarter Quality of Life Instrument (QLI) responses.
Patients also had blood samples taken and weight, height, waist, and hip measured, and they brought medication containers to clinic so that HRT dose, type, and regimen could be recorded.
For E2 measurements, the intra-assay coefficient of variation was 4.1%, and the inter-assay coefficient of variation was 6.6%; the detection limit was 5 pg/mL. Assayed samples below the detection limit of the assay were assigned a statistically conservative value of 4.9 rather than zero.
Approximately 42% of women in the medicated group had E2 levels less than the mean E2 level plus 1 SD in the controls (37 pg/mL). However, 11% in the HRT group had estradiol levels greater than the mean estradiol level plus 6 SD in the control patients (126 pg/mL), indicating substantial variability in E2 concentrations achieved with conventional oral and patch HRT.
In increasing control-based E2 categories, menopausal vasomotor and vaginal symptoms decreased (P < .06). Both follicle-stimulating hormone and luteinizing hormone levels were significantly correlated with E2 control-based categories (both P = .00).
Dr. Gavaler identified predictive factors that explained more than 51.1% variability in the E2 levels achieved in HRT-treated women: negative predictors included poor medical compliance, lower body fat mass, use of the patch, menopause duration, and being a white woman (European American); positive predictors included alcoholic beverage consumption, previous removal of the ovaries, and markers of factors involved in E2 production.
"The data strongly support an interpretation that women with E2 levels greater than the control E2 mean plus 6 standard deviations are conceivably being overtreated, and as a result may be at increased risk for the development of breast cancer and other adverse consequences," Dr. Gaveler writes.
"Women with E2 levels less than the control E2 mean plus 1 standard deviation (and thus indistinguishable from untreated women) conceivably are being ineffectively treated, and as a result may be at a risk of cardiovascular disease and hip fracture, which does not differ from the risk in controls," she continues.
"The results of this study provide a feasible approach, which could be used in randomized clinical trials to settle the furor arising from recent reports regarding the long-term risks and benefits of HRT, the Women's Health Initiative (WHI) randomized controlled trial, in particular," Dr. Gaveler adds.
The National Institute on Alcohol Abuse and Alcoholism, the Office of Women's Health Research, and the Office of Minority Health Research provided funding for this study.
J Womens Health. 2003;12(8):757-768
Reviewed by Gary D. Vogin, MD
Intensive Diabetes Treatment Has Lasting Beneficial Renal Effects
By Anthony J. Brown, MD
NEW YORK (Reuters Health) Oct 21 - In patients with type 1 diabetes, intensive glucose control seems to slow the progression of diabetic nephropathy even many years after the intensive intervention has ended, new research shows.
Started in 1981, the Diabetes Control and Complications Trial (DCCT) compared the benefits of intensive and conventional therapy in 1441 type 1 diabetics. The intensive therapy consisted of at least three daily insulin injections or pump use with dose adjustment based on frequent glucose monitoring. In contrast, conventional therapy consisted of no more than two daily injections and one blood or urine glucose test.
The results from DCCT revealed that intensive therapy was more effective than conventional therapy at controlling glucose levels and at slowing the progression of diabetic nephropathy. After DCCT ended in 1989, patients in the control group were offered intensive therapy supervised by their own physicians, while those in the treatment group were encouraged to continue the intensive therapy.
The current study, known as the Epidemiology of Diabetes Interventions and Complications (EDIC) study, represents eight years of additional follow-up for former DCCT participants. The results are reported in the October 22/29th issue of the Journal of the American Medical Association.
"Over time, the glycemic levels of the former control group began to drop, while those of the former intervention group rose, so that during the EDIC study the levels in each group were no longer substantially different," lead author Dr. David M. Nathan, from Massachusetts General Hospital, told Reuters Health.
Interestingly, although each group now had similar levels, a renal benefit was still seen in the former intervention group, Dr. Nathan noted. The new findings complement those reported in 2000, which showed that intensive therapy provides a persistent reduction in the risk of progressive retinopathy (see Reuters Health story February 10, 2000).
In the present study, previous treatment with intensive therapy was associated with a significant reduction in the risk of clinical albuminuria, hypertension, and having a serum creatinine level of 2 mg/dL or greater.
"The take-home message is that early, intensive intervention is very important," Dr. Nathan noted. "The earlier that patients can intervene to keep their HbA1c down the better effect they're going to get and the better long-term outcomes they're going to have."
"The mechanism for the persistent benefits may relate to the glycation of long-lived proteins," he said.
JAMA 2003;290:2159-2167.
