Immunologic study of the human immune system poses special safety problems associated with the risk for infection with human disease agents. Attention in recent years has focused on possible infection with the AIDS (HIV-1) virus. It should be noted, however, that human materials may harbor other dangerous pathogens, including hepatitis B virus (HBV), cytomegalovirus, EBV, and a host of bacterial pathogens.
The basic framework for safety in immunologic research is encompassed in the concept of the biosafety level. This defines a set of procedures mandated by the type of microorganism being handled, or likely to be handled, as well as the number of such organisms involved and the nature of the manipulations to be carried out. Biosafety level 1 (BL-1), the lowest level, applies to ubiquitous microorganisms found in the general environment and requires that standard microbiological practices be followed—including the use of mechanical pipetting devices, daily decontamination of work surfaces, prohibition of eating, smoking, and application of cosmetics in the laboratory area, use of laboratory coats, and appropriate hand washing. Biosafety level 2 (BL-2) applies to organisms capable of producing disease of moderate severity in normal healthy individuals. It assumes all the features of BL-1 and, in addition, applies more stringent conditions for laboratory cleaning, use of containment equipment (e.g., biosafety cabinets)—particularly if aerosols will be generated—and autoclaving of laboratory wastes. Biosafety level 3 (BL-3) applies to possible exposure to microorganisms capable of causing serious illness. This level differs from the BL-2 level in that it provides for a double-door entry system into a sealed "inner" laboratory having a unidirectional airflow. At this biosafety level, tissue is manipulated only within biosafety cabinets, centrifugation of specimens is accomplished with sealed safety cups, and special clothing and gloves are routinely worn. Finally, BL-4 applies to laboratory work with pathogens that pose a life-threatening risk to laboratory workers when even "casual" contact with tissue occurs. The safety practices employed at this level are an intensification of those at the BL-3 level and include extensive clothing changes before entering the work area, decontamination of waste, strict training of all laboratory personnel, and the use of class II biosafety cabinets (which provide for physical isolation of specimens) or of lower-class cabinets in association with one-piece positive-pressure personnel suits ventilated by a life-support system.
Most laboratory work with materials containing blood-borne pathogens can be safely accomplished with BL-2 level procedures, except when unusually large numbers of organisms must be handled or when aerosols will be generated. BL-3, on the other hand, is reserved for the more dangerous infectious agents and is the preferred level for research involving HIV-1. Both the BL-2 and BL-3 levels require the presence of a laboratory leader that is fully versed in safety practices, and, in addition, requires provision of safety training programs for workers and the establishment of laboratory-specific safety manuals. Particular attention must be given to the possibility of laboratory accidents that will result in infection of a laboratory worker (or waste handler) and the institution of strict procedures that prevent such accidents. Obvious examples here are the proscription of mouth pipetting and the use of instruments that cause skin breaks without adequate glove protection. It is essential that all persons working in a laboratory in which human tissues are being processed be fully aware of the potential for exposure to various pathogens present in the tissue. When a break in safety procedure and undue exposure does occur, it is the responsibility of everyone concerned to investigate the incident and to bring the exposed individuals to immediate medical attention.
Details concerning biosafety levels, precautions necessary for individual infectious agents, and other pertinent information is provided in the Centers for Disease Control/National Institutes of Health handbook Biosafety in Microbiological and Biomedical Laboratories. Every researcher engaged in the study of human tissue is advised to have a copy of this handbook in the laboratory. Another publication of particular use to those working with HIV-1 is Working Safely with HIV in the Research Laboratory: Biosafety Level 2/3, which contains procedures for biosafety in general and HIV in particular, as well as a wealth of other material relating to working with HIV in the laboratory.
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