3、 指示(shi)病毒選(xuan)擇

Indicator viruses can be classified into three types: "related" viruses (such as human viruses that may be carried by human blood products, including HAV, HBV, HIV, and B19), specific "model" viruses (such as MVM and x-MuLV viruses in CHO expression systems, and BV virus in baculovirus expression systems), and non-specific "model" viruses (such as PRV and Reo3 viruses in CHO expression systems). Priority should be given to selecting viruses that are closely related to potential contaminating viruses. If related viruses are unavailable or unsuitable for in vitro culture, specific "model" viruses can be used as substitutes.
When evaluating the overall virus clearance capability, non-specific model viruses with different characteristics should be selected. These include DNA/RNA, enveloped/non-enveloped, particle size, and viruses that are particularly resistant to physical/chemical treatments. The indicator virus should have a sufficiently high titer, and the selected indicator virus should not pose a biological hazard to operators or the environment.
The validation platform has a rich collection of virus strains, with clear backgrounds, high purity, and titers reaching 8-9 Log10/ml. Table 1 lists the four most commonly used indicator viruses for CHO expression product process validation.

Table 1: Properties of Commonly Used Indicator Viruses in Virus Clearance Process Validation

Virus Name	Virus Characteristics	Testing Method	Viral Titer Log10/ml
Reo3（呼腸孤病毒）	雙(shuang)鏈 RNA 病毒(du)，無包膜(mo)，抗性中50-70nm	TCID50 Q-PCR	8-9
MVM（鼠細小病毒(du) ）	單(dan)鏈 DNA 病毒無包膜，抗(kang)性極高(gao) 18-26nm	TCID50 Q-PCR	8.5-9.5
PRV(偽狂(kuang)病毒)	雙鏈 DNA 病(bing)毒有包膜，抗(kang)性(xing)中120-200nm	TCID50 Q-PCR	8-9
MuLv （鼠白血(xue)病病毒）	單鏈(lian) RNA 病(bing)毒(du)有包膜，抗性低 80-120nm	TCID50 Q-PCR	7.5-8.5
BV (桿狀病(bing)毒)	雙鏈 DNA病毒有(you)包膜 45×275nm	TCID50 Q-PCR	8-9
POL-1 (人脊髓灰質炎I型(xing)病毒)	單鏈 RNA 病毒無包膜，抗性中 25-30nm	TCID50	8-9
VSV (水皰性口炎病毒)	單鏈 RNA 病毒有包膜(mo)，抗性低 70×150nm	TCID50 Q-PCR	8-9
PPV （豬(zhu)細小病毒）	單鏈 DNA 病毒(du)無包膜(mo)，抗(kang)性高 18-24nm	TCID50 Q-PCR	7.5-8.5
HAdV-5 (人(ren)腺病毒5型(xing))	雙鏈 DNA 病毒無包膜，抗性低(di) 70-90nm	TCID50	8.5-9.5
BPIV-3 （牛副流感病(bing)毒3型）	單鏈 RNA 病(bing)毒(du)有包膜，抗性低 150-200nm	TCID50	8-9