Interferons (IFNs) are potent cytokines that serve as a critical component of the body's first line of defense against viral infections, playing a key role in inflammation and immune control by directly inducing pathogen-inhibiting molecules that suppress viral replication ^[1]. Arthropod-borne viruses (arboviruses) like Dengue virus (DENV), Zika virus (ZIKV), and Yellow Fever virus (YFV) encode proteins that antagonize the IFN response, helping these viruses evade host immunity and maintain sufficient viral loads in the blood (viremia) to sustain the vector-host transmission. Arboviruses pose a significant public health threat, affecting around 3.9 billion people in tropical and subtropical regions. However, most preclinical studies suggest that arboviruses cannot inhibit IFN responses in mice, rendering immunocompetent mice resistant to infection, with low viral loads and limited circulation, thus limiting their use in infection research ^[2-3]. As a result, immunodeficient mouse models with defects in multiple IFN signaling pathways have become essential tools for studying arbovirus pathogenesis and vaccine development ^[2-4]. Studies have demonstrated that wild-type mice of strains like C57BL/6, CD-1, or 129 rarely exhibit clinical symptoms after infection with arboviruses such as ZIKV. However, the virus has been detected in the blood, ovaries, and spleen of ZIKV-infected 129 mice, suggesting that this strain may be more susceptible to arboviruses ^[5-6]. Because the virus can persist in the bloodstream without causing disease or death, the 129 strain can be used to evaluate the teratogenic effects of such viruses. Furthermore, the 129 strain is commonly used in interferon signaling-deficient models related to other viral infections ^[7-8]. The IFNAR1 gene encodes a protein that is an essential component of the type I interferon (IFN) receptor, playing a critical role in the antiviral and immune responses. IFNAR1 is primarily expressed in immune cells, such as lymphocytes and dendritic cells, and various tissues, including the liver, brain, and skin. Defects in IFNAR1, whether due to mutations or regulatory abnormalities, can lead to severe diseases such as systemic lupus erythematosus, where excessive immune activation results in tissue damage, and certain cancers. Other diseases associated with IFNAR1 include hepatitis C, yellow fever, measles, papilloma, and viral infections. The A129 (Ifnar1 KO) mice on a 129 background are a type I (α/β) interferon receptor (Ifnar1) gene knockout model. The absence of the IFNAR1 protein in these mice leads to a lack of type I IFN receptor function, thereby reducing immune response and increasing susceptibility to viral infections. Homozygous A129 (Ifnar1 KO) mice are viable and fertile, but they show increased susceptibility to arbovirus infections.

Interferons (IFNs) are potent cytokines that serve as a critical component of the body's first line of defense against viral infections, playing a key role in inflammation and immune control by directly inducing pathogen-inhibiting molecules that suppress viral replication ^[1]. Arthropod-borne viruses (arboviruses) like Dengue virus (DENV), Zika virus (ZIKV), and Yellow Fever virus (YFV) encode proteins that antagonize the IFN response, helping these viruses evade host immunity and maintain sufficient viral loads in the blood (viremia) to sustain the vector-host transmission. Arboviruses pose a significant public health threat, affecting around 3.9 billion people in tropical and subtropical regions. However, most preclinical studies suggest that arboviruses cannot inhibit IFN responses in mice, rendering immunocompetent mice resistant to infection, with low viral loads and limited circulation, thus limiting their use in infection research ^[2-3]. As a result, immunodeficient mouse models with defects in multiple IFN signaling pathways have become essential tools for studying arbovirus pathogenesis and vaccine development ^[2-4]. Studies have demonstrated that wild-type mice of strains like C57BL/6, CD-1, or 129 rarely exhibit clinical symptoms after infection with arboviruses such as ZIKV. However, the virus has been detected in the blood, ovaries, and spleen of ZIKV-infected 129 mice, suggesting that this strain may be more susceptible to arboviruses ^[5-6]. Because the virus can persist in the bloodstream without causing disease or death, the 129 strain can be used to evaluate the teratogenic effects of such viruses. Furthermore, the 129 strain is commonly used in interferon signaling-deficient models related to other viral infections ^[7-8]. The IFNAR1 gene encodes a key component of the type I IFN receptor, while the IFNGR1 gene encodes the ligand-binding chain (α) of the type II (γ) IFN receptor. AG129 mice, which are knockout models for both the type I (α/β) IFN receptor (Ifnar1) and the type II (γ) IFN receptor (Ifngr1), lack functional IFNAR1 and IFNGR1 proteins, resulting in deficiencies in α/β/γ interferon receptor signaling and heightened susceptibility to viral infections. Homozygous AG129 mice are viable and fertile, and exhibit increased sensitivity to arboviral infections, generating viremia similar to that seen in humans. Compared to IFNα/β/γR KO mice on the C57BL/6 background, the 129-background AG129 mice exhibit more pronounced neurological symptoms after infection ^[6,9].

The protein encoded by the Angiotensin Converting Enzyme 2 (ACE2) gene belongs to the angiotensin converting enzyme family of dipeptidyl carboxydipeptidases and is homologous to Angiotensin I. ACE2 is expressed in a variety of human organs and has a strong affinity for Angiotensin I (AngⅠ) and Angiotensin II (AngⅡ) receptors. It catalyzes the cleavage of Ang I to angiotensin 1-9 (Ang1-9) and Ang II to angiotensin 1-7 (Ang1-7), which has a vasodilating and antihypertensive effect ^[1], and plays a role in the regulation of blood pressure, fluid balance, inflammation, cell proliferation, hypertrophy, and fibrosis, as well as in the regulation of cardiovascular and renal function and fertility ^[2]. ACE2 is also a common functional receptor for the spike protein of human coronavirus HCoV-NL63 and the severe acute respiratory syndrome coronaviruses SARS-CoV and SARS-CoV-2 ^[3]. This strain is a mouse Ace2 gene knockout model that uses gene editing technology to knock out the homologous gene of human ACE2 in mice. The knockout of the Ace2 gene will result in the absence of ACE2 protein expression, and this model can be used for the study of COVID-19. The homozygous Ace2-KO mice are viable and fertile.

The DPP4 gene (CD26) encodes dipeptidyl peptidase 4, an intrinsic type II transmembrane glycoprotein and a serine exopeptidase involved in glucose and insulin metabolism and immune regulation. The DPP4 protein is a functional receptor for the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). The spike protein of MERS-CoV binds to DPP4, mediating the virus's attachment to host cells and promoting virus-cell fusion, thereby initiating infection ^[1-2]. Studies have found that the DPP4 protein may interact with the S1 domain of the spike glycoprotein of COVID-19, aiding in enhancing the transmission efficiency of viral particles ^[3]. Experimental evidence has shown that hDPP4 transgenic mice infected with MERS-CoV experience high mortality and severe pneumonia ^[4]. These mice infected with Manis javanica HKU4-related coronavirus (MjHKU4r-CoV-1) develop mild to moderate pulmonary histological damage ^[5]. Thus, gene-edited mice expressing human DPP4 protein are important tools for studying coronavirus infections. Additionally, DPP4 expression is severely dysregulated in diseases such as inflammation, cancer, obesity, and diabetes. DPP4 is highly expressed in the intestine, where it selectively cleaves N-terminal dipeptides from various substrates, including incretins, to inactivate multiple bioactive peptides. Since incretins like glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are crucial for regulating postprandial insulin secretion, inhibiting DPP4 to elevate endogenous GLP-1 and GIP levels to increase insulin levels has become an important treatment method for type 2 diabetes (T2D) ^[6]. The B6-hDPP4(line 1) mouse is a humanized model constructed by gene editing technology to replace a partial region of the mouse Dpp4 gene with the human DPP4 gene CDS sequence. This model can be used to study the infection mechanisms of viruses such as MERS-CoV and COVID-19, as well as to develop related virus vaccines. Additionally, this model can be utilized to develop DPP4 inhibitor therapies. Additionally, Cyagen Biosciences has developed B6-hDPP4(line 2) mice (Catalog ID: I001188) on the C57BL/6JCya background strain and BALB/c-hDPP4(line 2) mice (Catalog ID: I001189) on the BALB/cAnCya background strain. These two models replace the mouse Dpp4 gene p.S29 to part of intron 2 with the "Human DPP4 CDS-rBG pA" expression cassette, meeting the experimental needs for different strain backgrounds.

The DPP4 gene (CD26) encodes dipeptidyl peptidase 4, an intrinsic type II transmembrane glycoprotein and a serine exopeptidase involved in glucose and insulin metabolism and immune regulation. The DPP4 protein is a functional receptor for the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). The spike protein of MERS-CoV binds to DPP4, mediating the virus's attachment to host cells and promoting virus-cell fusion, thereby initiating infection ^[1-2]. Studies have found that the DPP4 protein may interact with the S1 domain of the spike glycoprotein of COVID-19, aiding in enhancing the transmission efficiency of viral particles ^[3]. Experimental evidence has shown that hDPP4 transgenic mice infected with MERS-CoV experience high mortality and severe pneumonia ^[4]. These mice infected with Manis javanica HKU4-related coronavirus (MjHKU4r-CoV-1) develop mild to moderate pulmonary histological damage ^[5]. Thus, gene-edited mice expressing human DPP4 protein are important tools for studying coronavirus infections. Additionally, DPP4 expression is severely dysregulated in diseases such as inflammation, cancer, obesity, and diabetes. DPP4 is highly expressed in the intestine, where it selectively cleaves N-terminal dipeptides from various substrates, including incretins, to inactivate multiple bioactive peptides. Since incretins like glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are crucial for regulating postprandial insulin secretion, inhibiting DPP4 to elevate endogenous GLP-1 and GIP levels to increase insulin levels has become an important treatment method for type 2 diabetes (T2D) ^[6]. The B6-hDPP4(line 2) mouse is a humanized model constructed by gene editing technology to replace a partial region of the mouse Dpp4 gene with the human DPP4 gene CDS sequence. This model can be used to study the infection mechanisms of viruses such as MERS-CoV and COVID-19, as well as to develop related virus vaccines. Additionally, this model can be utilized to develop DPP4 inhibitor therapies. Similar models include the B6-hDPP4(line 1) mouse (Catalog ID: I001187), constructed on the C57BL/6NCya background strain, which replaces the sequence of the mouse Dpp4 gene with the human DPP4 gene CDS sequence, and the BALB/c-hDPP4(line 2) mouse (Catalog ID: I001189), constructed on the BALB/cAnCya background strain. These models meet the experimental needs of different strain backgrounds.

The DPP4 gene (CD26) encodes dipeptidyl peptidase 4, an intrinsic type II transmembrane glycoprotein and a serine exopeptidase involved in glucose and insulin metabolism and immune regulation. The DPP4 protein is a functional receptor for the Middle East Respiratory Syndrome Coronavirus (MERS-CoV). The spike protein of MERS-CoV binds to DPP4, mediating the virus's attachment to host cells and promoting virus-cell fusion, thereby initiating infection ^[1-2]. Studies have found that the DPP4 protein may interact with the S1 domain of the spike glycoprotein of COVID-19, aiding in enhancing the transmission efficiency of viral particles ^[3]. Experimental evidence has shown that hDPP4 transgenic mice infected with MERS-CoV experience high mortality and severe pneumonia ^[4]. These mice infected with Manis javanica HKU4-related coronavirus (MjHKU4r-CoV-1) develop mild to moderate pulmonary histological damage ^[5]. Thus, gene-edited mice expressing human DPP4 protein are important tools for studying coronavirus infections. Additionally, DPP4 expression is severely dysregulated in diseases such as inflammation, cancer, obesity, and diabetes. DPP4 is highly expressed in the intestine, where it selectively cleaves N-terminal dipeptides from various substrates, including incretins, to inactivate multiple bioactive peptides. Since incretins like glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are crucial for regulating postprandial insulin secretion, inhibiting DPP4 to elevate endogenous GLP-1 and GIP levels to increase insulin levels has become an important treatment method for type 2 diabetes (T2D) ^[6]. The BALB/c-hDPP4(line 2) mouse is a humanized model constructed by gene editing technology to replace a partial region of the mouse Dpp4 gene with the human DPP4 gene CDS sequence. This model can be used to study the infection mechanisms of viruses such as MERS-CoV and COVID-19, as well as to develop related virus vaccines. Additionally, this model can be utilized to develop DPP4 inhibitor therapies. Similar models include the B6-hDPP4(line 1) mouse (Catalog ID: I001187), constructed on the C57BL/6NCya background strain, which replaces the sequence of the mouse Dpp4 gene with the human DPP4 gene CDS sequence, and the B6-hDPP4(line 2) mouse (Catalog ID: I001188), constructed on the C57BL/6JCya background strain. These models meet the experimental needs of different strain backgrounds.

Interferons (IFNs) are potent cytokines that serve as a critical component of the body's first line of defense against viral infections, playing a key role in inflammation and immune control by directly inducing pathogen-inhibiting molecules that suppress viral replication ^[1]. Arthropod-borne viruses (arboviruses) like Dengue virus (DENV), Zika virus (ZIKV), and Yellow Fever virus (YFV) encode proteins that antagonize the IFN response, helping these viruses evade host immunity and maintain sufficient viral loads in the blood (viremia) to sustain the vector-host transmission. Arboviruses pose a significant public health threat, affecting around 3.9 billion people in tropical and subtropical regions. However, most preclinical studies suggest that arboviruses cannot inhibit IFN responses in mice, rendering immunocompetent mice resistant to infection, with low viral loads and limited circulation, thus limiting their use in infection research ^[2-3]. As a result, immunodeficient mouse models with defects in multiple IFN signaling pathways have become essential tools for studying arbovirus pathogenesis and vaccine development ^[2-4]. Studies have demonstrated that wild-type mice of strains like C57BL/6, CD-1, or 129 rarely exhibit clinical symptoms after infection with arboviruses such as ZIKV. However, the virus has been detected in the blood, ovaries, and spleen of ZIKV-infected 129 mice, suggesting that this strain may be more susceptible to arboviruses ^[5-6]. Because the virus can persist in the bloodstream without causing disease or death, the 129 strain can be used to evaluate the teratogenic effects of such viruses. Furthermore, the 129 strain is commonly used in interferon signaling-deficient models related to other viral infections ^[7-8]. The IFNGR1 gene encodes the ligand-binding chain (α) of the type II (γ) interferon receptor. IFNGR1 forms a receptor complex with IFNGR2, which can bind gamma interferon and participate in immune and inflammatory responses. The G129 (Ifngr1 KO) mice on a 129 background are a type II (γ) interferon receptor (Ifngr1) gene knockout model. The absence of the IFNGR1 protein in these mice results in defective gamma interferon receptor function, which reduces natural resistance and may increase susceptibility to certain viral infections. Homozygous G129 (Ifngr1 KO) mice are viable and fertile.

Angiotensin-converting enzyme 2 (ACE2) is the predominant cell surface receptor for SARS-CoV-2 virus infection in humans, but due to species differences, the SARS-CoV-2 virus is unable to bind to the ACE2 receptor in most wild-type rodents. By inserting the "K18 promoter-human ACE2 CDS-P2A-CreERT2-rBGpA" sequence into the safety harbor of the mouse genome through gene editing technology, humanized ACE2 mice (K18-hACE2) that stably express the human ACE2 receptor can be obtained. This mouse model expresses human ACE2 protein in epithelial cells under the regulation of the human keratin K18 promoter, including the most initially infected airway epithelial cells. This model also carries the CreERT2 element, which can be induced by tamoxifen to express the Cre recombinase, so this strain can be used either alone for COVID-19 and related studies or in combination with flox mice for studying the role of specific host genes in response to SARS-CoV-2 virus infection. K18-hACE2 mice can be infected with the SARS-CoV-2 virus, resulting in severe disease characterized by weight loss, rapid respiration, hunched posture, and immobility. This strain responds to viral attack in a dose-dependent manner, thus allowing the study of severe acute respiratory disease in mice heavily infected by high doses of the virus, as well as the long-term effects of low doses of mild infection. The model should be handled in strict accordance with the guidelines for the prevention of SARS-CoV-2 virus infection in humans as specified by CDC, ABSA, and WHO, and appropriate personal protective equipment (PPE) and handling methods should always be used when using these mice for research.

Angiotensin-converting enzyme 2 (ACE2) is a member of the angiotensin-converting enzyme (ACE) family of dipeptidyl carboxypeptidases. ACE2 is expressed in a variety of human tissues and has a high affinity for angiotensin I (Ang I) and angiotensin II (Ang II) receptors. ACE2 catalyzes the cleavage of Ang I to angiotensin 1-9 (Ang 1-9) and Ang II to angiotensin 1-7 (Ang 1-7), which have vasodilatory and hypotensive effects ^[1]. ACE2 plays a role in regulating blood pressure, fluid balance, inflammation, cell proliferation, hypertrophy, and fibrosis, as well as in the regulation of cardiovascular and renal function and fertility ^[2]. ACE2 is also the common functional receptor for the spike protein of human coronaviruses HCoV-NL63, SARS-CoV, and SARS-CoV-2 ^[3]. However, due to species differences, the SARS-CoV-2 virus cannot bind to the ACE2 receptor of wild-type rodents ^[4-5]. Replacement of mouse Ace2 with human ACE2 by gene editing techniques resulted in humanized ACE2 mice (hACE2) that stably express human ACE2 receptors for COVID-19 studies. This strain contains a loxP-hACE2 CDS-loxP gene expression cassette inserted at the endogenous mouse Ace2 gene locus, which enables the regulation of human ACE2 gene (hACE2) expression by the mouse endogenous Ace2 regulatory element. When bred with relevant tissue-specific Cre mouse mating, knockout of the hACE2 gene can be achieved in specific tissues of the offspring mice. Homozygous LoxP-hACE2-CDS^tm mice are viable and fertile.

Angiotensin-converting enzyme 2 (ACE2) is a member of the angiotensin-converting enzyme (ACE) family of dipeptidyl carboxypeptidases. ACE2 is expressed in a variety of human tissues and has a high affinity for angiotensin I (Ang I) and angiotensin II (Ang II) receptors. ACE2 catalyzes the cleavage of Ang I to angiotensin 1-9 (Ang 1-9) and Ang II to angiotensin 1-7 (Ang 1-7), which have vasodilatory and hypotensive effects ^[1]. ACE2 plays a role in regulating blood pressure, fluid balance, inflammation, cell proliferation, hypertrophy, and fibrosis, as well as in the regulation of cardiovascular and renal function and fertility ^[2]. ACE2 is also the common functional receptor for the spike protein of human coronaviruses HCoV-NL63, SARS-CoV, and SARS-CoV-2 ^[3]. However, due to species differences, the SARS-CoV-2 virus cannot bind to the ACE2 receptor of wild-type rodents ^[4-5]. Replacement of mouse Ace2 with human ACE2 by gene editing techniques resulted in humanized ACE2 mice (hACE2) that stably express human ACE2 receptors for COVID-19 studies. This strain is a human ACE2 (hACE2) conditional overexpression model generated by integrating the hACE2 gene expression element into the mouse ROSA26 safe harbor site. Under normal conditions, the expression of hACE2 is blocked by the upstream loxP-Stop-loxP expression stop cassette. Upon mating with Cre mice, the Cre recombinase mediates the deletion of the sequence between the loxP sites, including the stop cassette, thereby enabling the expression of hACE2. When bred with tissue-specific Cre mice, overexpression of the hACE2 gene and protein can be achieved in specific tissues of the offspring mice. Homozygous ROSA26-LSL-hACE2 mice are viable and fertile.