Regulatory Interpretation: Validation of Inactivation Procedures for Regulated Nucleic Acids

Regulatory Interpretation: Validation of Inactivation Procedures for Regulated Nucleic Acids

Date: December 21, 2022

Subject: Validation of Inactivation Procedures for Regulated Nucleic Acids

This response addresses your September 24, 2021, request for a regulatory interpretation related to 42 CFR § 73.3(d)(4) of the select agent and toxins regulations. Specifically, your request “seeks guidance for the infectivity testing criteria for nucleic acids from inactivated positive-sense RNA viruses.”

According to your request for interpretation, your “specific concern is for formalin-fixed tissues from animals previously infected with positive sense RNA viruses.”  You state that your entity subjects positive-stranded RNA viruses, such as Venezuelan Equine Encephalitis virus, to a validated inactivation procedure (such as formalin fixation of non-paraffin embedded tissues from animals exposed to or infected with a select agent virus) and a viability testing method. However, because your entity does “not attempt to isolate the genomic material of the virus to determine infectivity,” in other words, you do not extract the RNA genome from the virus that has been subjected to a validated inactivation procedure, you are unclear if you must also determine that the RNA had been rendered incapable of producing infectious virus in order to qualify for the exclusion in 42 CFR § 73.3(d)(4).

The select agent and toxin regulations provide that “[n]ucleic acids that can produce infectious forms of any of the select agent viruses” are select agents. 42 CFR § 73.3(c)(1), 7 CFR § 331.3(c)(1), and 9 CFR § 121.3(c)(1). Therefore, to qualify for the exclusion in 42 CFR § 73.3(d)(4) [or the identical exclusions in 42 CFR § 73.4(d)(4), 7 CFR § 331.3(d)(4), and 9 CFR §§ 121.3(d)(4), 121.4(d)(4)] of the select agent and toxin regulations, regulated nucleic acids that can produce infectious forms of any select agent virus must be subjected to a validated inactivation procedure that is confirmed through a viability testing protocol to ensure the nucleic acids are incapable of producing infectious select agent virus. The answer to your question is YES; entities must determine that the RNA has been rendered incapable of producing infectious virus in order to qualify for the exclusion in 42 CFR § 73.3(d)(4). For more information on viability/infectivity testing of regulated nucleic acids, please see the section on “Infectivity Testing of Inactivation Procedures” in the “Guidance on the Inactivation or Removal of Select Agents or Toxins for Future Use” (Guidance on the Inactivation or Removal of Select Agents and Toxins for Future Use [PDF – 1 MB]).