temporarily suspend the use of Rotarix while the agency and manufacturer in-

vestigated the finding of DNA from PCV1 in the vaccine [11]. On 14 May 2010, the

FDA recommended resumption of the use of Rotarix. The EMA and FDA both

concluded that the benefits of the vaccines were substantial and included the pre-

vention of death and hospitalization for severe rotavirus disease. These benefits

were considered to outweigh the risk, which is theoretical when considering that

Rotarix is an orally administrated vaccine.

New sequencing technologies are now able to detect unknown viruses present in

a biological sample (e.g., cell, seed, or vaccine) without prior knowledge of their

presence and genetic sequences [15]. A direct consequence is the increasing number

of new viruses to be included into the risk-assessment exercise.

In light of this greater level of virus diversity, NGS technology is revealing the

limitations of those current risk-control strategies mainly based on infectivity

assays and PCR testing. The poor performance of in vitro assays is not a problem

of assay sensitivity but rather because the adventitious viral agents are not able to

replicate in the cells used in the assay, or when viral replication is not detectable

using classic read-outs, such as CPE or hemadsorption/hemagglutination. For

example, the in-vitro 9CFR assays was identified as having limited capabilities in

detecting a wide range of viruses, even within the same families, in bovine serum

[16]. These viruses could infect human cells and represented potential con-

taminant risks to biological products. When viruses are incapable of propagating

in cell culture, specific PCR assays are typically included in the testing plan.

However, the potentially high genetic variability of the virus may need to be

considered in the design of the PCR assay, or particular virus variants may pass

undetected. For example, Gagnieur et al. [17] reported mismatches between the

sequence of the PCR primers used to detect BVDV and the BVDV sequences

present in the batches of bovine serum.

Thus, the viral-risk assessments and the associated risk-mitigation strategies

based on the testing for specific viral contaminants can become rapidly obsolete.

New assays cannot be systemically developed and implemented after each new

virus/variant discovery. This gap in viral coverage of existing testing is increasingly

recognized in the scientific community, particularly in the case of novel cell sub-

strates and biologically derived raw materials [14].

4.3.5

VIRAL-RISK ASSESSMENT

From the lessons learned during the last decade, regulatory guidance has adapted

quickly. Biopharmaceutical manufacturers are now advised to implement additional

assays to detect adventitious agents as part of the manufacturing processes, to en-

sure the quality and safety of the biological products.

In the conventional viral-risk model, viral-risk assessments represent the first key

stage to identify and reduce the risk.

According to the “Quality Risk Management ICH Q9” [18], a viral-risk as-

sessment consists of the identification of hazards plus analysis and evaluation of

risks associated with exposure to those hazards.

Cell lines for vaccine production

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