Pathogenesis of a Texas feline immunodeficiency virus isolate: An emerging subtype of clade B

Commercially Available Enzyme-Linked Immunosorbent Assay and Polymerase Chain Reaction Tests for Detection of Feline Immunodeficiency Virus Infection

BACKGROUND

Feline immunodeficiency virus (FIV) infection is an important cause of disease of cats worldwide. Initial screening is commonly performed by commercially available point-of-care (POC) ELISA tests. Confirmatory testing for positive POC test results is recommended. Polymerase chain reaction (PCR) tests for FIV are commonly used additional testing methods; however, reported measures of diagnostic accuracy vary widely between PCR tests, making interpretation of results difficult.

HYPOTHESIS/OBJECTIVE

There is very good agreement between results of a commercially available PCR test and a POC ELISA test for FIV for specimens collected from owned and shelter-housed cats.

ANIMALS

Blood samples from 168 cats from 2 adoption guarantee shelters, an FIV Sanctuary, and 64 private homes were used.

METHODS

This was a prospective study. Whole blood samples were collected in K₂ -EDTA, divided, and submitted for PCR and ELISA testing. Follow-up whole blood samples were collected in lithium heparin from cats with discordant results and submitted for virus isolation (VI).

RESULTS

There was very good agreement between ELISA and PCR (kappa 0.87; P < .001; 95% CI 0.79, 0.95). Of 168 cats, eleven had discordant ELISA/PCR results: 7 ELISA+/PCR- and 4 ELISA-/PCR+. Using VI as a reference standard, there were 4 false-positive PCR results, 5 false-positive ELISA results, and 1 false-negative PCR result (1 cat lost to follow-up).

CONCLUSIONS AND CLINICAL IMPORTANCE

While there was good agreement between the POC ELISA and PCR tests, the discordant results highlight the importance of cautious interpretation of test results and the necessity of confirmatory testing.

Clinical aspects of feline retroviruses: a review

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are retroviruses with global impact on the health of domestic cats. The two viruses differ in their potential to cause disease. FeLV is more pathogenic, and was long considered to be responsible for more clinical syndromes than any other agent in cats. FeLV can cause tumors (mainly lymphoma), bone marrow suppression syndromes (mainly anemia), and lead to secondary infectious diseases caused by suppressive effects of the virus on bone marrow and the immune system. Today, FeLV is less commonly diagnosed than in the previous 20 years; prevalence has been decreasing in most countries. However, FeLV importance may be underestimated as it has been shown that regressively infected cats (that are negative in routinely used FeLV tests) also can develop clinical signs. FIV can cause an acquired immunodeficiency syndrome that increases the risk of opportunistic infections, neurological diseases, and tumors. In most naturally infected cats, however, FIV itself does not cause severe clinical signs, and FIV-infected cats may live many years without any health problems. This article provides a review of clinical syndromes in progressively and regressively FeLV-infected cats as well as in FIV-infected cats.

Clinical aspects of feline immunodeficiency and feline leukemia virus infection

Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) are retroviruses with a global impact on the health of domestic cats. The two viruses differ in their potential to cause disease. FIV can cause an acquired immunodeficiency syndrome that increases the risk of developing opportunistic infections, neurological diseases, and tumors. In most naturally infected cats, however, FIV itself does not cause severe clinical signs, and FIV-infected cats may live many years without any health problems. FeLV is more pathogenic, and was long considered to be responsible for more clinical syndromes than any other agent in cats. FeLV can cause tumors (mainly lymphoma), bone marrow suppression syndromes (mainly anemia) and lead to secondary infectious diseases caused by suppressive effects of the virus on bone marrow and the immune system. Today, FeLV is less important as a deadly infectious agent as in the last 20 years prevalence has been decreasing in most countries.

Dual-subtype feline immunodeficiency virus vaccine provides 12 months of protective immunity against heterologous challenge

The duration of immunity of the dual-subtype feline immunodeficiency virus (FIV) vaccine, Fel-O-Vax FIV, for protection against subtype-B FIV was assessed in this study. Vaccinated cats along with controls were challenged with FIV(FC1), a subtype-B FIV strain, 54 weeks after the final vaccination, and monitored for 46-48 weeks for provirus and viral RNA in peripheral blood, provirus in lymphoid organs, and CD4:CD8 ratios. Results of provirus detection in peripheral blood and lymphoid organs and plasma viral RNA loads showed that 10/14 vaccinated cats were fully protected for 48 weeks against infection with FIV(FC1) whereas 5/5 controls were persistently infected with FIV(FC1). CD4:CD8 inversions were noted in association with FIV infection and viral loads were not significantly different between FIV infected controls and the unprotected vaccinated animals.