Development, Histological, and Ultrastructural Evaluation of Sheep Hyperimmune Serum Therapy for COVID-19

In response to the threat posed by new variants of SARS-CoV-2 and the urgent need for effective treatments in the absence of vaccines, the aim of this study was to develop a rapid and cost-effective hyperimmune serum (HS) derived from sheep and assess its efficacy. The utilization of a halal-certified, easily maintained in certain geographic regions, easy-to-handle animal such as sheep could provide a viable alternative to the expensive option of horses. Sheep were immunized with a whole inactivated SARS-CoV2 antigen to produce HS, which was evaluated for neutralizing potency using the PRNT50 assay. K18-hACE2 transgenic mice (n=35) were divided into three groups: control, SARS-CoV-2 exposure through inhalation, and SARS-CoV-2 exposed mice treated with HS. HS efficacy was assessed through serum proinflammatory cytokine levels, qRT-PCR analysis, histopathological examination of lungs and hearts, and transmission electron microscopy. Purified HS exhibited significant neutralizing activity (1/24,576). The SARS-CoV-2+HS group showed lower levels of TNF-alpha , IL-10, and IL-6 (P<0.01) and relatively lower levels of MCP-1 compared to the SARS-CoV-2 group. HS prevented death, reduced viral RNA levels in the lungs and hearts, protected against severe interstitial pneumonia, preserved lung tissue integrity, and prevented myocyte damage, while the SARS-CoV-2 group exhibited viral presence in the lungs. This study successfully developed a sheep-derived HS against the entire SARS-CoV-2 virus, resulting in a significant reduction in infection severity, inflammation, and systemic cytokine production. The findings hold promise for treating severe COVID-19 cases, including emerging viral variants, and immunocompromised patients.