ARCHIVED - Infectious Diseases News Brief - August 31, 2012
Three new cases have brought to 107 the number of people who have contracted the disease in Quebec City since July. Health officials have set up a toll-free information line at 1-877-644-4545. The deadly bacteria grow in the stagnant water of cooling systems, spreading in little droplets through air conditioning. Authorities have disinfected the systems in more than 100 Quebec City buildings but say more cases could surface in the coming days. Inspectors are going to return to 30 cooling systems over the next few days to look at the water and to make sure building owners have complied with clean-up directives. The source of the current outbreak is believed to be the cooling systems of two building towers. Chantale Giguere, assistant director general for public security in Quebec City, said more than 100 cooling towers have been inspected. The Quebec government promised additional steps against the disease following criticism last week from Quebec City's mayor. The new measures, which may be enacted this fall, include holding building owners legally responsible for maintaining their cooling systems. Heavy smokers and people with weak immune systems are most at risk of catching the disease, which is not contagious. Symptoms include persistent fever, coughing and difficulty breathing.
It can be treated with antibiotics. There has never been a documented case of drug-resistant legionella. The current spate is not considered the largest legionella outbreak in Canadian history. In 2005, 23 people died and more than 100 others contacted the disease at a home for the elderly in Toronto. The bacteria were traced to a cooling tower at the facility. A molecular biologist with Public Health Ontario says dealing with the disease is really complex because it is so common. "It's basically found everywhere in water sources," said Cyril Guyard. "It seems to concentrate in man-made water systems." "Because it's so ubiquitous, it's found everywhere, it's really complex and challenging to link the environmental sources with the patient cases."
Can HIV be transformed into a biotechnological tool for improving human health? According to a CNRS team at the Architecture et Réactivité de l'ARN (RNA Architecture and Reactivity) laboratory, the answer is yes. Taking advantage of the HIV replication machinery, the researchers have been able to select a specific mutant protein. Added to a culture of tumor cells in combination with an anticancer drug, this protein improves the effectiveness of the treatment at 1/300 the normal dosage levels. These findings could lead to long-term therapeutic applications in the treatment of cancer and other pathologies. The human immunodeficiency virus (HIV), which causes AIDS, uses human cell material to multiply, primarily by inserting its genetic material into the host cells' genome. The distinctive characteristic of HIV is that it mutates constantly, and consequently generates several mutant proteins (or variants) in the course of its successive multiplications. This phenomenon allows the virus to adapt to repeated environmental changes and resist the antiviral treatments that have been developed so far. At the IBMC (Institut de Biologie Moléculaire et Cellulaire) in Strasbourg, the researchers of the CNRS Architecture et Réactivité de l'ARN laboratory had the idea of using this multiplication strategy to rechannel the effects of the virus for therapeutic purposes, in particular the treatment of cancer. They first altered the HIV genome by introducing a human gene that is found in all cells: the gene for deoxycytidine kinase (dCK), a protein that activates anticancer drugs (2). Researchers have been trying to produce a more effective form of dCK for several years. Through HIV multiplication, the CNRS team has selected a "library" of nearly 80 mutant proteins and tested them on tumor cells in the presence of an anticancer drug. The results have enabled them to identify a dCK variant that is more effective than the wild-type (non-mutated) protein, inducing the death of tumor cells in culture. In combination with this protein, the anticancer drugs showed identical effectiveness at 1/300 the dose. The possibility of reducing the doses of anticancer drugs would palliate the problems posed by their components' toxicity, reduce their side effects and, most importantly, improve their effectiveness. One advantage of this experimental technique is that the mutant proteins were tested directly on cells in culture. The next step in the years to come will be preclinical (animal) studies on the isolated mutant protein. In addition, this experimental system using a normally life-threatening virus is likely to lead to a great many other therapeutic applications.
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