Field Performance of a Rapid Test to Detect Progressive, Regressive, and Abortive Feline Leukemia Virus Infections in Domestic Cats in Australia and Germany

Mark E Westman; Juliana Giselbrecht; Jacqueline M Norris; Richard Malik; Jennifer Green; Elle Burton-Bradley; Ashley Cheang; Theres Meili; Marina L Meli; Katrin Hartmann; Regina Hofmann-Lehmann

doi:10.3390/v15020491

Field Performance of a Rapid Test to Detect Progressive, Regressive, and Abortive Feline Leukemia Virus Infections in Domestic Cats in Australia and Germany

Viruses. 2023 Feb 10;15(2):491. doi: 10.3390/v15020491.

Authors

Affiliations

¹ Sydney School of Veterinary Science, The University of Sydney, Sydney, NSW 2006, Australia.
² Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine LMU Munich, Veterinaerstrasse 13, 80539 Munich, Germany.
³ Clinical Laboratory, Department of Clinical Diagnostics and Services, and Center for Clinical Studies, Vetsuisse Faculty, The University of Zurich, CH-8057 Zurich, Switzerland.
⁴ The Sydney Institute for Infectious Diseases, The University of Sydney, Sydney, NSW 2006, Australia.
⁵ Centre for Veterinary Education, The University of Sydney, Sydney, NSW 2006, Australia.
⁶ School of Veterinary and Animal Science, Charles Sturt University, Wagga Wagga, NSW 2678, Australia.

Abstract

Different feline leukemia virus (FeLV) infection outcomes are possible in cats following natural exposure, such as progressive infections (persistent viremia), regressive infections (transient or no viremia followed by proviral persistence) and abortive infections (presence of only antibodies). Laboratory-based testing is currently required for categorization of infection outcomes in cats. The aim of this study was to evaluate the field performance of a novel, rapid, combination point-of-care (PoC) test kit commercially available in Europe (v-RetroFel^®Ag/Ab; 2020-2021 version) to determine different FeLV infection outcomes by concurrent detection of FeLV antigen (p27) and antibodies against FeLV transmembrane envelope protein (p15E). A secondary aim was to evaluate the performance of the same test kit (v-RetroFel^®FIV) to determine positive/negative feline immunodeficiency virus (FIV) infection status by the detection of antibodies to FIV capsid protein (p24) and transmembrane glycoprotein (gp40). Two cohorts of domestic cats were recruited and tested with v-RetroFel^® using plasma or serum, including cats in Australia (n = 200) and cats in Germany (n = 170). Results from p27 antigen PoC testing, proviral DNA PCR, and neutralizing antibody testing or testing for antibodies against non-glycosylated surface unit envelope protein (p45) were used to assign cats to groups according to different FeLV infection outcomes. Testing with a laboratory-based FeLV p15E antibody ELISA was also performed for comparison. In the first cohort, v-RetroFel^®Ag/Ab correctly identified 89% (109/122) FeLV-unexposed cats and 91% (21/23) progressive infections, but no regressive (0/23) or abortive (0/32) infections. In the second cohort, v-RetroFel^®Ag/Ab correctly identified 94% (148/158) FeLV-unexposed cats and 100% (4/4) progressive infections, but no regressive (0/2) and only 17% (1/6) abortive infections. There was test agreement between v-RetroFel^®Ab and the p15E laboratory ELISA in 58.9% of samples. As a secondary outcome of this study, the sensitivity and specificity of v-RetroFel^®FIV testing in cohort 1 were 94.7% (18/19) and 98.3% (178/181), and in cohort 2, 30.0% (3/10) and 100.0% (160/160), respectively. Prior history of FIV vaccination did not produce any false-positive FIV results. In conclusion, v-RetroFel^®Ag/Ab (2020-2021 version) was unable to accurately determine different FeLV infection outcomes in the field. Improvements of the test prior to application to field samples are required.

Keywords: FIV; FeLV; antibodies; humoral immunity; infection; v-RetroFel®; vaccination; veterinary science.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Antibodies, Neutralizing
Australia / epidemiology
Cats
Germany
Leukemia Virus, Feline*
Leukemia, Feline* / diagnosis
Leukemia, Feline* / epidemiology
Membrane Proteins

Substances

Antibodies, Neutralizing
Membrane Proteins

Grants and funding

This research was supported financially by the Australian Companion Animal Health Foundation and the Feline Health Research Fund. M.E.W. was supported by an Australian Postgraduate Award (APA), the Neil and Allie Lesue Scholarship, the Herbert Johnson Travel Grant Scholarship, and an Endeavour Research Fellowship. Scil paid the salary for Juliana Giselbrecht’s s employment as a research assistant at the Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine LMU Munich. Juliana Giselbrecht’s research visit to the Clinical Laboratory at the Vetsuisse Faculty, University of Zurich was also supported by a scholarship by the DAAD (German Academic Exchange Service) for the period of 1 July 2021 to 31 December 2021.