IL2rg-/- rats support prolonged infection of human RSV / 中国实验动物学报

Objective To overcome the limitations of existing human respiratory syncytial virus(hRSV)animal models,such as semi-permissiveness and short duration of infection,this study established an IL2rg gene knockout(IL2rg-/-)rat model using TALEN gene editing technology.Methods The animal model was infected with hRSV intranasally.Clinical characteristics,body weight,and temperature changes were observed over the infection period(0～35 days).The total viral loads in respiratory organs,such as the nasal tissue,trachea,and lungs,were measured at various time points(4,11,20,and 35 days post-infection).Pathological analysis was conducted on target organs at the endpoint of observation(35 days post-infection).Changes in peripheral blood T,B,NK,and NKT cells and various cytokines were assessed at various time points(4,20,and 35 days post-infection).Results(1)IL2rg/-knockout rats sustained high viral loads in the nasal cavity upon intranasal inoculation with hRSV.The average peak titer rapidly reached 1 × 1010 copies/g in nasal tissue and 1 × 107 copies/g up to 5 weeks post-infection.(2)However,no significant pathological changes were noted in nasal,tracheal,or lung tissues.(3)An increase was observed in the content of peripheral blood B cells in hRSV-infected IL2rg--rats.(4)IL-6 and MCP-1 were increased in the early stage of infection and then decreased at the end of the observation period.Conclusions This study established a new IL2rg-/-rat model using TALEN technology and found that this model effectively supported high-level replication and long-term infection of hRSV,providing a good basis for antiviral drug screening and in vivo efficacy evaluation of anti-hRSV antibodies.

Establishment of hKDR+/+ Humanized and Rag1-/- Gene Knockout Double Genetically Modified Mouse Model / 实验动物与比较医学

ObjectiveThrough improving the potential of vascular endothelial growth factor receptor (VEGFR)-humanized mouse model (hKDR+/+) with C57BL/6N background to allow the growth of different mouse tumor cell lines, to establish novel tumor-bearing mouse models which can support in vivo tumorigenesis of different mouse tumor cell lines and be used to evaluate drugs targeting VEGFR.MethodsFirstly, a method to evaluate the in vivo activity of antibody targeting VEGFR based on the hKDR+/+ humanized mouse model was established. Recombinant activating gene 1 (Rag1) knockout mice (Rag1-/-) were established using CRISPR/Cas9 technology. Then these Rag1-/- mice were crossed with hKDR+/+ mice to get a double gene modified homozygous hKDR+/+/Rag1-/- mouse model by screening. Finally, tumor cell lines derived from different mouse strains were tested on the double gene-modified mouse model to compare the differences in tumor growth. ResultsAntibodies designed for VEGFR showed significant anti-tumor activity in hKDR+/+ mice, which significantly reduced tumor volume and weight compared with the PBS group (P<0.01, P<0.05). The number of B cells and T cells in the peripheral blood of Rag1-/- mice and hKDR+/+/Rag1-/- mice decreased (P<0.05, P<0.001). Tumors were observed in hKDR+/+/Rag1-/-, Rag1-/-, wild-type, and hKDR+/+ mice after 7 d of inoculation of MC38 cells derived from C57BL/6 mice. Tumors were only observed in groups of hKDR+/+/Rag1-/- and Rag1-/- mice, but not in the wild-type and hKDR+/+ mice after 10 d of inoculation with CT26 cells derived from BALB/c mice. After 3 weeks of inoculation, the tumor volume of hKDR+/+/Rag1-/- mice was significantly larger than that of Rag1-/- mice (P<0.01). ConclusionRag1 knockout mice were obtained and a novel hKDR+/+/Rag1-/- double genes modified mouse model was further screened. The tumor cell lines from different mouse strain origins were more prone to growth in mice with Rag1 gene deficiency. The results suggest that the reduced immune response of hKDR+/+ humanized mice will improve the capacity of supporting the growth of mouse tumor lines in the model. As a result, more tumor-bearing mouse models may be constructed for the evaluation of drugs targeting VEGFR in this way.

A live attenuated influenza virus-vectored intranasal COVID-19 vaccine provides rapid, prolonged, and broad protection against SARS-CoV-2 infection

Remarkable progress has been made in developing intramuscular vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); however, they are limited with respect to eliciting local immunity in the respiratory tract, which is the primary infection site for SARS-CoV-2. To overcome the limitations of intramuscular vaccines, we constructed a nasal vaccine candidate based on an influenza vector by inserting a gene encoding the receptor-binding domain (RBD) of the spike protein of SARS-CoV-2, named CA4-dNS1-nCoV-RBD (dNS1-RBD). A preclinical study showed that in hamsters challenged 1 day and 7 days after single-dose vaccination or 6 months after booster vaccination, dNS1-RBD largely mitigated lung pathology, with no loss of body weight, caused by either the prototype-like strain or beta variant of SARS-CoV-2. Lasted data showed that the animals could be well protected against beta variant challenge 9 months after vaccination. Notably, the weight loss and lung pathological changes of hamsters could still be significantly reduced when the hamster was vaccinated 24 h after challenge. Moreover, such cellular immunity is relatively unimpaired for the most concerning SARS-CoV-2 variants. The protective immune mechanism of dNS1-RBD could be attributed to the innate immune response in the nasal epithelium, local RBD-specific T cell response in the lung, and RBD-specific IgA and IgG response. Thus, this study demonstrates that the intranasally delivered dNS1-RBD vaccine candidate may offer an important addition to fight against the ongoing COVID-19 pandemic, compensating limitations of current intramuscular vaccines, particularly at the start of an outbreak.

Cathepsin L plays a key role in SARS-CoV-2 infection in humans and humanized mice and is a promising target for new drug development

To discover new drugs to combat coronavirus disease 2019 (COVID-19), an understanding of the molecular basis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is urgently needed. Here, for the first time, we report the crucial role of cathepsin L (CTSL) in patients with COVID-19. The circulating level of CTSL was elevated and was positively correlated with disease course and severity in COVID-19 patients. Correspondingly, SARS-CoV-2 pseudovirus infection increased CTSL expression in human cell lines and human ACE2 transgenic mice, while CTSL overexpression, in turn, enhanced pseudovirus infection. CTSL functionally cleaved the SARS-CoV-2 spike protein and enhanced virus entry, as evidenced by CTSL overexpression and knockdown in vitro and application of CTSL inhibitor drugs in vivo. Furthermore, amantadine, a licensed anti-influenza drug, significantly inhibited CTSL activity and prevented SARS-CoV-2 pseudovirus infection. Therefore, CTSL is a promising target for new anti-COVID-19 drug development.

Structural basis for neutralization of SARS-CoV-2 and SARS-CoV by a potent therapeutic antibody

The COVID-19 pandemic caused by the SARS-CoV-2 virus has resulted in an unprecedented public health crisis. There are no approved vaccines or therapeutics for treating COVID-19. Here we reported a humanized monoclonal antibody, H014, efficiently neutralizes SARS-CoV-2 and SARS-CoV pseudoviruses as well as authentic SARS-CoV-2 at nM level by engaging the S receptor binding domain (RBD). Importantly, H014 administration reduced SARS-CoV-2 titers in the infected lungs and prevented pulmonary pathology in hACE2 mouse model. Cryo-EM characterization of the SARS-CoV-2 S trimer in complex with the H014 Fab fragment unveiled a novel conformational epitope, which is only accessible when the RBD is in open conformation. Biochemical, cellular, virological and structural studies demonstrated that H014 prevents attachment of SARS-CoV-2 to its host cell receptors. Epitope analysis of available neutralizing antibodies against SARS-CoV and SARS-CoV-2 uncover broad cross-protective epitopes. Our results highlight a key role for antibody-based therapeutic interventions in the treatment of COVID-19. One sentence summaryA potent neutralizing antibody conferred protection against SARS-CoV-2 in an hACE2 humanized mouse model by sterically blocking the interaction of the virus with its receptor.

A non-competing pair of human neutralizing antibodies block COVID-19 virus binding to its receptor ACE2

Neutralizing antibodies could be antivirals against COVID-19 pandemics. Here, we report the isolation of four human-origin monoclonal antibodies from a convalescent patient in China. All of these isolated antibodies display neutralization abilities in vitro. Two of them (B38 and H4) block the binding between RBD and vial cellular receptor ACE2. Further competition assay indicates that B38 and H4 recognize different epitopes on the RBD, which is ideal for a virus-targeting mAb-pair to avoid immune escape in the future clinical applications. Moreover, therapeutic study on the mouse model validated that these two antibodies can reduce virus titers in the infected mouse lungs. Structure of RBD-B38 complex revealed that most residues on the epitope are overlapped with the RBD-ACE2 binding interface, which explained the blocking efficacy and neutralizing capacity. Our results highlight the promise of antibody-based therapeutics and provide the structural basis of rational vaccine design. One Sentence SummaryA pair of human neutralizing monoclonal antibodies against COVID-19 compete cellular receptor binding but with different epitopes, and with post-exposure viral load reduction activity.

Determination of hematological and visceral weight parameters of F1 carcinogenesis transgenic C57-ras model CB6F1 mice / 中国比较医学杂志

Objective To determine the normal range of hematological and visceral weight parameters of F 1 4-week and 8-week old, male and female transgenic CB6F1 mice.The influence of gender and week age on the biochemical parameters was assessed .Methods 4-week and 8-week old CB6F1 mice, half male and half female ( n=20 in each group) , were weighed alive , dissected to weigh the main viscera , and blood samples were collected to test the physiological and biochemical parameters .Results When 4-week old and 8-week old CB6F1 mice were compared , there were significant differences in 22 parameters (body weight, heart, liver, spleen, left ovary, left testis, right testis, WBC, RBC, HGB, HCT, MCV, MCH, PCT, MPV, PDW, LYM, TP, ALT, ALB, P and TG) (P<0.01 for all), and in 8 parameters (left kidney, right kidney, right adrenal, thymus, left ovary, RDW, MON%and BUN) (P<0.05 for all). When male and female 4-week CB6F1 mice were compared, there were significant differences in 14 parameters ( body weight, heart, liver, spleen, lung, left kidney, right kidney, MCHC, LYM, ALT, ALP, GLU, P and CHO) (P<0.01 for all), and in 6 parameters (right adrenal, WBC, PCT, MPV, TP and BUN) (P<0.05 for all).For male and female 8-week old CB6F1 mice, there were significant differences in 15 parameters (body weight, heart, liver, lung, left kidney, right kidney, MCV, PCT, LYM, LYM%, NEUT%, ALT, GLU, P and CHO) (P<0.01 for all), and in 5 parameters (WBC, RBC, MPV, NEUT and TP) (P<0.05 for all).Conclusions The normal range of hematological and visceral weight parameters of 4-week and 8-week old male and female CB6F1 mice are determined.Our study establishes normal detection indexes of CB6F1 mice and provides useful reference for its application .

Impact of different mouse blastocyst donors on the efficiency of germline chimera production from C57BL/6 embryonic stem cells / 中国实验动物学报

Objective To improve the gene targeting efficiency with C57BL/6 embryonic stem ( ES) cells.Meth-ods Three different genetically modified C57BL/6 ES cell lines, named TLX3, Ai3K and SL, were microinjected into ICR, B6( Cg)-Tyrc-2J and BALB/c mouse blastocysts, respectively.The efficiency was statistically evaluated according to three aspects:blastocyst collection, chimera production and germline transmission.Results None of the three ES cell lines was germline transmitted with B6(Cg)-Tyrc-2J mice as blastocyst donors, while it was achieved with both BALB/c and ICR mouse blastocysts.Compared in the aspect of blastocysts collection, ICR mouse was much better than BALB/c mouse (P<0.05), and the chimera production efficiency of ICR mouse was comparable to that of BALB/c mouse (P =0.115). As to the germline transmission efficiency, that of BALB/c mice is significantly higher than that of the ICR mice ( P<0.01).Conclusions The germline transmission efficiency of BALB/c mouse is highest among these three mouse strains. However, it has the disadvantages of blastocyst collection, developmental delay and zona pellucida fragility, compared with ICR mouse.Therefore, ICR mouse is also a good candidate as blastocyst donor for embryonic stem cell microinjection.

Effects of preincubation medium and other factors affecting in vitro fertilization rate of post-thawed genetically engineering mouse spermatozoa / 中国比较医学杂志

Objective To discuss the effect of in vitro fertilization ( IVF) and mouse sperm cryopreservation , to establish a simple and economic frozen system for the genetically engineering mice preservation .Methods Sperm from genetically engineering mice were cryopreserved , IVF was performed using post-thawed sperm, then embryo transfer, to compare the effects of cryopreservation medium、age of male mice and sperm preincubation medium .Results Using CPA as sperm cryopreservation medium , when PM was used thawed-sperm preincubation in IVF , the fertility rates were from 82.49%to 91.43%, when HTF was used thawed-sperm preincubation in IVF , the fertility rates were from14.46%to 27.38%, there was a signification difference between PM and HTF sperm preincubation medium;10 to 35 weeks male genetically engineering mice sperm were succeed cryopreservation , and positive mice were procreated after 2-cell embryos were transferred;R18S3、CPM and CPA was used to freeze sperm , the fertility rates were 75.85%、88.89%to 94.27%, positive mice were procreated after 2-cell embryos were transferred;2-cell embryos after IVF were freezed , then thawed and positive mice were procreated after 2-cell embryos were transferred .Conclusion Using CPA as sperm cryopreservation medium , when PM was used thawed-sperm preincubation in IVF , genetically engineering mice sperm were succeed cryopreservation .

Characterization of growth performance of F1 hybrid CB6 F1 C57-ras transgenic mouse model / 中国比较医学杂志

Objective To obtain the basic growth parameters of a self-established F1 hybrid CB6F1 C57-ras transgenic mouse model, and to provide basic information for commercialization of this mouse model. Methods F1 hybrid mice (CB6F1) were produced by crossing C57-ras heterozygous transgenic (c-Ha-ras+/-) male mice and wild-type BALB/cJ female mice.The average litter size, weaning rate, sex ratio, growth performance and C57-ras transgenic positive rate were recorded and analyzed.Results The average litter size was eight, weaning rate was 90%, and sex ratio was approximately in accordance with prediction.The average body weight of newborn mice was 1.73 ±0.05 g.The average body weight of 10-week old c-Ha-ras transgenic female and male mice in CB6F1 background was 24.38 ±1.74 g and 29.42 ±1.72g, respectively, which had a significant difference (P<0.01).The c-Ha-ras transgenic positive rate was 46.9%. which was in accordance with genetic rules.Conclusions The F1 hybrid mice (CB6F1) produced by crossing C57-ras heterozygous transgenic ( c-Ha-ras +/-) male mice and wild-type BALB/cJ female mice show normal growth performance and development characteristics, and it can be used for large-scale commercial supply.

Comparison of three methods for total DNA extraction from mouse models / 中国比较医学杂志

Objective To establish a simple , fast and economic total DNA extraction method to serve the rapid identification of model mouse genotype in large number of mice .Methods Three methods, i.e.phenol extraction, isopropyl alcohol precipitation and mouse ear boiling methods were used to extract the total DNA from ten C 57-rasmodel mice.The purity and yield of DNA obtained by the three methods were compared , and polymerase chain reaction ( PCR) assay was used to compare the efficacy of the three extraction methods .Results Among the three methods , phenol extraction was the best and isopropyl alcohol precipitation was the poorest in DNA yield .In terms of DNA purity , the phenol extraction was the best and the mouse ear boiling method was the poorest .All the three methods could be used to extract the total DNA from mice serving as template of PCR reaction for the mouse genotype identification .The time consumption of three methods are 12.5 hr ,13 hr and 0.18 hr.Mouse ear boiling method was significantly lower than that of the other two methods ( P <0.01 ) ,.The obtained total DNA can be stored at conventional -20℃for 7 days and 30 days later still can be used as a template for PCR reaction .Conclusions Among the three methods studied , the mouse ear boiling method is simple and with the lowest cost , so it is feasible for total DNA extraction in scaled genotyping experiments .