Generation of infectious retrovirus aerosol through medical laser irradiation

A novel model system was used to investigate the spread of infectious particles and live cells through the application of lasers commonly used in clinical medicine. Supernatants from a cell line producing recombinant retroviruses carrying a marker gene (neoR) were exposed to Er:YAG-laser beams. Aerosols were collected from various sites and distances from the point of laser impact and were analyzed by reverse transcription-polymerase chain reaction (RT-PCR) for neoR. In addition, a susceptible indicator cell line was used to investigate the presence of infectious virions in collected aerosols. To test the possibility of dissemination of viable cells, a cell line was laser irradiated, and the generated aerosols were analyzed for the presence of viable cells. The viral marker gene neoR could be detected in 16% (distance: 5.0-6.3 cm) to 59% (0.5-1.6 cm) of wells adjacent to the point of laser impact. The presence of infectious viruses in laser vapors conferring G418 resistance could be detected in 3% (distance 5.0-6.3 cm) to 20% (distance: 0.5-1.6 cm) of wells containing susceptible cells, and subsequent PCR analysis of isolated resistant clones revealed the presence of neoR-RNA and -DNA. Viable cells were detected in 40% (distance 0.7-3.6 cm) to 3% (distance 10.7-11.8 cm) of wells adjacent to the point of laser impact. These results demonstrate that laser vapors can contain infectious viruses, viral genes, or viable cells and may promote the spread of infections or tumor cell dissemination.