Viral Transport System

I. Definition

A viral transport system (VTS) is a tool or medium specifically designed for collecting, preserving, and transporting virus samples. It can maintain the viability of viruses, preventing them from becoming inactivated or degraded during the process from the collection site to the laboratory for analysis and testing, ensuring that subsequent virus detection, isolation, cultivation, research, and other work can be carried out smoothly.

II. Components

1. Buffer Solutions
   • Viral transport systems usually contain buffer solutions, which function to maintain a stable pH value. Common buffer systems include phosphate – buffered saline (PBS), etc. A stable pH environment is crucial for maintaining the structure and activity of viruses because viruses are sensitive to changes in pH, and an inappropriate pH may lead to the denaturation of viral proteins or the degradation of nucleic acids.
2. Proteins and Nutrients
   • They contain proteins such as bovine serum albumin (BSA). These proteins can provide certain protection for viruses, preventing virus loss due to adsorption onto the container walls during transportation. At the same time, the added proteins can, to some extent, simulate the environment inside host cells, helping to maintain the activity of viruses. In addition, specific nutrients may also be present to meet the basic survival requirements of viruses in a short period.
3. Antibiotics and Antifungal Agents
   • To prevent bacterial and fungal contamination during sample collection and transportation, antibiotics (such as penicillin and streptomycin) and antifungal agents (such as amphotericin B) are generally added to the viral transport system. These antimicrobial substances can inhibit the growth of foreign microorganisms, prevent them from competing with viruses for nutrients, and avoid the impact of microbial metabolites on viral activity.
4. Cryoprotectants (in specific cases)
   • For some virus samples that need to be transported at low temperatures or stored for a long time, cryoprotectants such as glycerol and dimethyl sulfoxide (DMSO) may be added to the viral transport system. These cryoprotectants can reduce damage to viruses during the freezing and thawing processes and prevent the destruction of viral structures caused by ice crystal formation.

III. Types

1. Liquid – based Viral Transport Systems
   • This is the most common type, mainly consisting of the above – mentioned liquids containing various components. It is applicable to the collection and transportation of various virus samples and is relatively simple to operate. After sample collection, the virus – containing sample is directly placed into the liquid, mixed thoroughly, and then sealed for storage and transportation. For example, when collecting respiratory virus samples (such as influenza viruses), using this liquid transport system can well maintain the activity of viruses until laboratory testing.
2. Swab – based Viral Transport Systems
   • They consist of specially – made swabs and matching preservation solutions. The swabs are used for collecting virus samples, such as from the throat, nasal cavity, and other parts. After collection, the swab is placed in a tube containing the preservation solution, and the components of the preservation solution are similar to those of the liquid – based transport system and can maintain the activity of viruses. This system is very convenient for collecting virus samples from some locally – infected areas, and the swab can effectively collect a sufficient amount of viruses.
3. Dry – type Viral Transport Systems (relatively less used)
   • In this system, after virus sample collection, the virus is transported in a relatively stable dry state through special drying treatment. During laboratory testing, the virus is re – hydrated by specific methods. This type of transport system has its advantages in some special situations. For example, for some viruses that are relatively stable in a dry environment or when there is a need for long – distance transportation and long – term storage, but its operation is relatively complex, and its application is not as widespread as the first two types.