Evaluating Antibody Mediated Protection against Alpha, Beta, and Delta SARS-CoV-2 Variants of Concern in K18-hACE2 Transgenic Mice

Abstract

SARS-CoV-2 variants of concern (VoC) are impacting responses to the COVID-19 pandemic. Here, we utilized passive immunization using human convalescent plasma (HCP) obtained from a critically ill COVID-19 patient in the early pandemic to study the efficacy of polyclonal antibodies generated to ancestral SARS-CoV-2 against the Alpha, Beta, and Delta VoC in the K18 human angiotensin converting enzyme 2 (hACE2) transgenic mouse model. HCP protected mice from challenge with the original WA-1 SARS-CoV-2 strain; however, only partially protected mice challenged with the Alpha VoC (60% survival) and failed to save Beta challenged mice from succumbing to disease. HCP treatment groups had elevated receptor binding domain (RBD) and nucleocapsid IgG titers in the serum; however, Beta VoC viral burden in the lung and brain was not decreased due to HCP treatment. While mice could be protected from WA-1 or Alpha challenge with a single dose of HCP, six doses of HCP could not decrease mortality of Delta challenged mice. Overall, these data demonstrate that VoC have enhanced immune evasion and this work underscores the need for in vivo models to evaluate future emerging strains. IMPORTANCE Emerging SARS-CoV-2 VoC are posing new problems regarding vaccine and monoclonal antibody efficacy. To better understand immune evasion tactics of the VoC, we utilized passive immunization to study the effect of early-pandemic SARS-CoV-2 HCP against, Alpha, Beta, and Delta VoC. We observed that HCP from a human infected with the original SARS-CoV-2 was unable to control lethality of Alpha, Beta, or Delta VoC in the K18-hACE2 transgenic mouse model of SARS-CoV-2 infection. Our findings demonstrate that passive immunization can be used as a model to evaluate immune evasion of emerging VoC strains.

Diet induced obesity and type 2 diabetes drives exacerbated sex-associated disease profiles in K18-hACE2-mice challenged with SARS-CoV-2

“…The Alpha strain was intranasally administered at 10 3 , 10 4 , and 10 5 PFU per dose. Using a previously established disease scoring system (55,68,69), we determined that the 10 3 PFU dose caused lethality but postponed the time to morbidity compared to higher doses (Fig. 2A) and caused disease phenotypes that increase in severity over time (Fig.…”

“…The Alpha variant (strain B.1.1.7) of SARS-CoV-2 emerged in the United Kingdom in the spring of 2021 and moved rapidly across the globe. Alpha seemed to have enhanced virulence compared to ancestral strains of the virus in K18-hACE2-mice as well as other preclinical animal models (55,(62)(63)(64)(65)(66)(67). Due to the significance of Alpha variant's dominance among circulating strains in humans, we used this VOC to study the effects of DIO and Type 2 Diabetes in the K18-hACE2 mouse model of SARS-CoV-2 infection.…”

“…Mice were euthanized either due to disease scores or at the end of the experiment with an IP injection of Euthasol (390mg/kg) (Pentobarbital) followed by cardiac puncture as a secondary measure of euthanasia. Each animal was the dissected to collect tissues for pathological analysis as previously described (55)Cardiac blood was collected in BD Microtainer gold serum separator tubes and centrifuged at 15,000 x g for 5 minutes to separate the serum for downstream analysis. PBS (1mL) was pushed by catheter through the nasal pharynx and collected in a 1.5mL Eppendorf tube for Nasal Wash. For future RNA purification, 500μL of nasal wash was added to 500μL of TRIzol reagent (Zymo Research Catalog No R2050-1-200) and the remainder of the nasal wash was stored for serological analysis.…”

“…The SARS-CoV-2 Alpha variant strain was obtained for challenge from BEI: hCoV19/England/204820464/2020 (Alpha; NR-54000)(GISAID: EPI_ISL_683466). The virus was propagated in Vero E6 cells (ATCC-CRL-1586) as described previously (53). Normal diet or DIO K18-hACE2 mice were challenged with a 10 3 PFU dose.…”

“…Health assessments of the mice were scored based on the following criteria: weight loss (scale 0-5 (up to 20% weight loss)), appearance (scale 0-2), activity (scale 0-3), eye closure (scale 0-2), and respiration (scale 0-2). All five criteria were scored based off a scaling system where 0 represents no symptoms and the highest number on the scale denotes the most severe phenotype as previously described by our lab (54). Additive health scores of the criteria listed above were assigned to each mouse after evaluation and assessed so that mice scoring 5 or above, 20% weight loss, or significant drops in temperature received immediate euthanasia.…”