Location: Infectious Bacterial Diseases Research
Project Number: 5030-32000-232-019-I
Project Type: Interagency Reimbursable Agreement
Start Date: Sep 1, 2022
End Date: Aug 31, 2025
Objective:
1. What is the in vivo magnitude and duration of infectious viral shedding of SARS-CoV-2 in WTD and how long can viral RNA be detected by RT-PCR?
2. How do SARS-CoV-2 susceptibility and infection dynamics compare across variants of concern?
3. What is the duration of antibody persistence and are post-infection deer protected from re-infection with the same variant (homologous infection) or against a different (heterologous infection) variant?
4. What is the in vitro susceptibility of various deer cell lines to infection with variants of concern, how do growth curves compare among variants, and how do different variants respond in competitive growth assays?
Approach:
Animals: Yearling white-tailed does, from private a producer (n=20). Testing will be conducted to determine possible prior exposure to SARS-CoV-2.
Animals will be housed according to treatment group in Animal Biosafety Level 3 animal rooms at NADC in Ames, IA.
Infection for pathogenesis comparison and duration of immunity
Group 1: Delta variant of concern (VOC) SARS-CoV-2 strain B.1.617.2 (n=10)
Group 2: Omicron VOC SARS-CoV-2 strain B.1.1.529 (n=10)
Deer will be inoculated intranasally with virus suspension containing 105 to 106 TCID50 of either Omicron or Delta VOCs of SARS-CoV-2. Clinical signs, virus shedding, and persistence of antibody titers will be compared between the two groups.
Swab sampling for both groups:
• Nasal swabs and/or oral swabs for PCR and virus isolation (VI)
• Days 0-7, 9, 11, 14, 18, 21, 28, then every 2-weeks thereafter.
Serum sampling for serology
• Days 0, 7, 14, 21, 28, then every 2-weeks thereafter.
Protection from reinfection:
When antibody titers wane, both groups will be rechallenged with either Delta or Omicron as described above. For one of the groups this would be a homologous challenge and for the other group a heterologous challenge.
Swab sampling for both reinfection groups:
• Nasal swabs and/or oral swabs for PCR and VI
• Days 0-7, 9, 11, 14, 18, 21, 28, then every 2-weeks thereafter.
Serum sampling for serology
• Days 0, 7, 14, 21, 28, then every 2-weeks thereafter, until antibody titers wane.
Necropsy and examination of tissues:
At the end of the study, animals will be humanely euthanized and examined.
Tissues collected for examination are based on our previous deer studies with SARS-CoV-2.
H&E slides and ISH slides will be examined by two experienced pathologists at NADC.
Publications in scientific peer-reviewed journals:
1. The initial comparison of clinical signs and virus shedding in deer infected with either Delta or Omicron variants represents novel information and advances our understanding of SARS-CoV-2 infection in deer sufficiently to warrant publication.
2. Antibody titer persistence and protection from reinfection represents novel information and advances our understanding of SARS-CoV-2 infection in deer sufficiently to warrant publication.
