[Opinion] The Danger of Animal Adaptive Trials

Author: Billwilliam | Reviewer: Irene

In the PLA’s biowarfare textbook “The Unnatural Origin of SARS-1 and the Man-made Human Virus as a Genetic Bioweapon“, the term “adaptive trial” has been mentioned in almost every chapter. This is a technique to make a virus adapt to new hosts (humans, for example), thus turning an innocuous animal virus into a bioweapon. The PLA is obsessed with this technique probably because adaptive mutations could erase the marks of gene editing and make the bioweapon appear “natural” in origin. The CCP’s goal is to commit “perfect crimes” and get away from punishment.

On page 93 in chapter 4, the book refers to a new type of contemporary bioweapon called “host-swapping disease”, which is an animal virus modified by adaptive trials to infect humans. One method of adaptive animal trial is a serial passage, which involves the following steps: 1) infecting a few model animals, 2) extracting the pathogen in these animals, 3) using the extract to infect other model animals, 4) extracting the pathogen again, and 5) repeating the process for many rounds of passage. The virus undergoes mutations to adapt to the animal model — viral infectivity and virulence increase significantly after many rounds of serial passage.

Let’s look at one specific example of adaptive animal trials. In an article published in the Science journal, a group of scientists from Communist China created a mutant strain of SARS-CoV-2 (or COVID-19) that can infect wild-type mice1. The SARS-CoV-2 virus normally has high specificity for human cells and does not infect wild-type mice. The scientists carried out a serial passage to enhance its ability to infect mice1. As shown in the diagram, wild-type mice were inoculated by the SARS-CoV-2 virus intranasally. The mice were euthanized three days later, and their lung tissues were homogenized. The lysate of their virus-containing lung tissues was then used to inoculate other mice for the next round of passage1. This process was repeated for six cycles until the virus has acquired enough adaptive mutations to infect mice and cause severe pneumonia in them1. The viral load (in terms of RNA copies per gram of tissue) increases gradually from passage 1 to passage 6.   

Figure 1. The serial passage of SARS-CoV-2 in mice. The original SARS-CoV-2 virus (black) undergoes adaptive mutation in six rounds of serial passage to become a mutant strain (red) that can infect mice.

One of the adaptive mutations the virus acquired is an amino acid substitution at position 501 of the Spike protein—asparagine in the original sequence is replaced by tyrosine (N501Y). According to the article, the mutant Spike protein has a higher affinity to mouse ACE2 and thus contributes to enhanced virulence among mice1.

Adaptive animal trials are dangerous because they can be used to create novel, emerging diseases that target humans. In the experiment above, the serial passage was used to infect mice with a human virus, SARS-CoV-2. But if the process is done in reverse, such as trying to adapt an animal virus to infect humans, then a new bioweapon is created.

In addition, the PLA’s biowarfare textbook describes an “ecology type genetic bioweapon” that can infect both humans and wild animals. This kind of bioweapon can persist for long durations since infected animals can serve as reservoir hosts of the pathogen. If the mouse-adapted SARS-CoV-2 mutant strain were released or leaked into nature, wild mice or rats may become reservoir hosts carrying the mutant virus, thus causing recurring epidemic outbreaks for years.

I also want to point out the affiliations of the article’s authors. Many of them are affiliated with the Academy of Military Medical Sciences and its subsidiary, the Beijing Institute of Microbiology and Epidemiology — these are institutions of the People’s Liberation Army. Of course, they claimed the purpose of their experiment is to create animal models for vaccine development.

The US Department of State under former Secretary Mike Pompeo published a fact sheet stating that Communist China engaged in secret bioweapon development. Communist China has an obligation, they must tell the truth about the origin of SARS-CoV-2.


  1. Adaptation of SARS-CoV-2 in BALB/c mice for testing vaccine efficacy“, Gu, H., and et al., Science 369, 1603-1607 (2020).

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