2007-06-10-世界卫生组织-WHO_Study_Group_on_Cell_Substrates_for_Production_of_Biologicals_30页_304kb

WHO Study Group on Cell Substrates for Production of Biologicals - Meeting Report Summary

Core Content

The World Health Organization (WHO) Study Group on Cell Substrates for Production of Biologicals convened its second meeting in Geneva on 11–12 June 2007. The meeting aimed to revise the current WHO requirements for cell substrates used in the production of biologicals, particularly vaccines, and to address new scientific and regulatory challenges. The group focused on the safety and risk assessment of continuous cell lines (CCLs), including the potential presence of adventitious agents and the oncogenic and infectious risks posed by residual cellular DNA.

Main Goals and Progress

Goals

• Revise the WHO Requirements for cell substrates to reflect new scientific knowledge and technological developments.
• Develop new testing methods and standards for evaluating cell substrates, including adventitious agents and tumorigenicity.
• Provide scientifically sound, evidence-based guidance for the use of novel cell substrates in vaccine production.
• Address the legal and practical issues related to WHO cell banks.

Progress Since May 2006

• Completed additional studies on tumorigenicity of CCLs and oncogenicity of DNA.
• Analyzed existing methods for detecting residual cell DNA and proposed revisions.
• Identified research gaps and initiated discussions on new testing methodologies.
• Considered the need for updated guidelines to reflect the emergence of new viruses and the use of novel cell types such as insect cells.

Key Issues and Discussions

Adventitious Agents

• New viruses and agents may emerge and contaminate cell substrates, particularly through raw materials.
• Testing procedures need to be updated to include new detection methods and international harmonization.
• Insect cells, due to their growth at lower temperatures, may be exposed to different types of agents.
• The Study Group emphasized the development of new in vitro tests that align with the principles of reducing, refining, and replacing animal testing.

Tumorigenicity of Continuous Cell Lines

• Tumorigenicity testing is shifting from documenting the absence of a tumorigenic phenotype to characterizing the phenotype itself.
• In vivo testing using athymic nude mice is considered the most appropriate model for assessing tumorigenicity.
• In vitro assays, such as soft agar colony formation, are being evaluated but are not reliable indicators of in vivo tumorigenicity.
• The group recommended the use of a qualified NIH 3T3 cell bank for standardizing in vitro transformation assays.

Oncogenicity and Infectivity of Cellular DNA

• DNA from tumorigenic cells may pose oncogenic risks, but current data are largely negative.
• In vitro infectivity assays are more sensitive than oncogenicity assays in detecting biological activity.
• A new system was developed to measure the infectivity of cloned DNA using retrovirus proviral copies and permissive cell co-culture.

Conclusions and Next Steps

• The Study Group is preparing a revised WHO document on cell substrates.
• A broad consultation with regulators, manufacturers, and other stakeholders is planned for 2008.
• The group emphasized the importance of considering the potential risks associated with novel cell substrates and developing standardized testing protocols.
• A position paper summarizing current testing approaches and proposing improvements will be part of the revised document.
• The use of negative control cells such as MRC-5 is not recommended for tumorigenicity testing.
• A qualified HeLa cell bank would contribute to the standardization of tumorigenicity testing.

Recommendations

• Develop new in vitro testing methods that reduce reliance on animal testing.
• Update testing procedures to account for new viruses and agents.
• Streamline testing for adventitious agents using broad-spectrum detection systems.
• Consider the use of a specific mouse strain deficient in T and NK cells for assessing oncogenicity.
• Establish a standardized in vitro infectivity assay to evaluate DNA biological activity.
• Ensure that any assessment of tumorigenicity is discussed and approved with the relevant National Regulatory Authority (NRA).

Next Steps

• Preparation of a revised WHO document on cell substrates.
• Planning for a 2008 consultation with stakeholders.
• Continued research and validation of new testing methods.
• Development of a position paper on current testing approaches and proposed improvements.

References

• WHO TRS 878 (October 1996)
• WHO guidelines on recombinant HPV-like particle vaccines (2006)
• International conference on vaccine cell substrates (2004)
• DNA microarray studies on immortalization and transformation (2007)

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This summary provides an overview of the key topics, discussions, and recommendations from the second meeting of the WHO Study Group on Cell Substrates for Production of Biologicals, highlighting the evolving landscape of cell substrate safety and testing in the context of vaccine development.