Evaluation of a quantitative enzyme-linked immunosorbent assay for feline leukemia virus p27 antigen and comparison to proviral DNA loads by real-time polymerase chain reaction

Beall, Melissa J.; Buch, Jesse; Cahill, Roberta; Clark, Genevieve H; Hanscom, Jancy; Эстрада, Марко; Leutenegger, Christian M.; Chandrashekar, Ramaswamy

doi:10.1016/j.cimid.2019.101348

Cited by 15 publications

(21 citation statements)

References 24 publications

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“…At times, concentrations of one or the other can drop below the level of detection of some tests, leading to discordant results that may change over time. 61 Quantitative PCR assays for provi-ral DNA are becoming commercially available in more countries and they provide additional information to classify a cat’s status. 15,61 Cats that initially test positive by both p27 antigen and PCR can transition to a regressive infection pattern, usually within 16 weeks of infection.…”

Section: Diagnosis Of Retrovirus Infectionsmentioning

confidence: 99%

2020 AAFP Feline Retrovirus Testing and Management Guidelines

Little

Levy

Hartmann³

et al. 2020

Journal of Feline Medicine and Surgery

140

207

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Clinical importance: Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) infections are found in cats worldwide. Both infections are associated with a variety of clinical signs and can impact quality of life and longevity. Scope: This document is an update of the 2008 American Association of Feline Practitioners' feline retrovirus management guidelines and represents current knowledge on pathogenesis, diagnosis, prevention and treatment of retrovirus infections in cats. Testing and interpretation: Although vaccines are available for FeLV in many countries and for FIV in some countries, identification of infected cats remains an important factor for preventing new infections. The retrovirus status of every cat at risk of infection should be known. Cats should be tested as soon as possible after they are acquired, following exposure to an infected cat or a cat of unknown infection status, prior to vaccination against FeLV or FIV, and whenever clinical illness occurs. It might not be possible to determine a cat's infection status based on testing at a single point in time; repeat testing using different methods could be required. Although FeLV and FIV infections can be associated with clinical disease, some infected cats, especially those infected with FIV, can live for many years with good quality of life. Management of infected cats:There is a paucity of data evaluating treatments for infected cats, especially antiretroviral and immunomodulatory drugs. Management of infected cats is focused on effective preventive healthcare strategies, and prompt identification and treatment of illness, as well as limiting the spread of infection.

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Section: Diagnosis Of Retrovirus Infectionsmentioning

confidence: 99%

2020 AAFP Feline Retrovirus Testing and Management Guidelines

Little

Levy

Hartmann³

et al. 2020

Journal of Feline Medicine and Surgery

140

207

View full text Add to dashboard Cite

show abstract

“…When compared to the patient's sample diluted with an unrelated antiserum, a 50% or greater reduction in absorbance between the two wells of the assay is considered to be specific binding and confirms the presence of FeLV p27 antigen. In the current study, this same microtiter plate ELISA was performed with quantitation, as previously described, using a panel of recombinant p27 calibrators to determine the concentration of p27 antigen in the sample [27]. The resulting limit of quantitation was estimated to be 1 ng/mL, while the limit of detection for the assay was estimated to be 0.2 ng/mL.…”

Section: Enzyme-linked Immunosorbent Assay (Elisa) Testingmentioning

confidence: 99%

“…From an eluate of 150 μL, a 5 μL aliquot was added to a 12.6 μL PCR reaction. The quantitative real-time PCR assay includes six internal quality controls and utilizes standardized instrumentation that allows an optimized batch of master mix to be calibrated to a standard curve which is generated from serial dilutions of a synthetic oligonucleotide positive control [27]. The dynamic range of the assay covers 7 orders of magnitude and can detect one copy of the standard per reaction which equates to a limit of quantitation of 300 proviral DNA equivalents/mL of whole blood [27].…”

Section: Real-time Polymerase Chain Reaction (Pcr)mentioning

confidence: 99%

“…Given that focal and regressive infections are associated with lower amounts of p27 antigen and copy numbers of proviral DNA as compared with progressive infections, discordant results between these two methods may be a consequence of the biology of the disease, and also the ability of these assays to consistently produce a positive qualitative result near their limit of detection. When fully quantitative assays for p27 antigen and proviral DNA were applied to a convenience population of commercial diagnostic laboratory samples, a positive correlation between the concentration of p27 antigen and the copy numbers of proviral DNA was observed, and discordant results were more numerous at the lower end of the quantitative range [27]. The purpose of this study was to establish cutoff values for the concentration of p27 antigen and the copy numbers of proviral DNA that could distinguish high positive versus low positive cats and determine if the classification of cats by these cutoff values would be associated with survival during the four-year study period.…”

Section: Introductionmentioning

confidence: 99%

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Feline Leukemia Virus p27 Antigen Concentration and Proviral DNA Load Are Associated with Survival in Naturally Infected Cats

Beall

Buch

Clark

et al. 2021

Viruses

Self Cite

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Longitudinal studies of cats naturally infected with feline leukemia virus (FeLV) are important for understanding disease outcomes. Levels of p27 antigen and copy numbers of proviral DNA have been associated with FeLV-infection courses. The purpose of this prospective study was to establish cutoff values for p27 antigen concentration and proviral DNA load that distinguished high positive from low positive groups of cats and to evaluate an association with survival. At enrollment, 254 cats were tested by point-of-care and microtiter plate enzyme-linked immunosorbent assays (ELISAs) for p27 antigen and real-time polymerase chain reaction (PCR) for proviral DNA. The 127 positive cats were retested monthly for six months and monitored for survival over the four-year study. A receiver operating characteristic-based analysis of samples with concordant or discordant qualitative results for p27 antigen and proviral DNA was used to establish cutoff values, and when applied to test results at enrollment for classifying cats as high positive or low positive, a significant difference in survival was observed. High positive cats had a median survival of 1.37 years (95% CI 0.83–2.02) from time of enrollment, while most low positive cats were still alive (93.1% survival). Quantitative results for p27 antigen concentration and proviral DNA load were highly correlated with survival times in FeLV-infected cats.

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“…Moreover, several studies have demonstrated that FeLV test results can revert from positive to negative status, potentially signaling a regressive or abortive infection. 1,[8][9][10] Even when using high-accuracy tests, the complex natural history of FeLV infection makes it difficult to secure a definitive diagnosis, which presents an added challenge to the identification and effective management of FeLV-infected shelter cats. 10,11 Regressive infections are associated with a robust immune response that may, at times, suppress viral loads below the level of detection following an initial period of transient antigenemia.…”

Section: Introductionmentioning

confidence: 99%

Outcome of cats referred to a specialized adoption program for feline leukemia virus-positive cats

Lockhart

Levy

Amirian

et al. 2020

Journal of Feline Medicine and Surgery

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Objectives The purpose of this retrospective study was to assess outcomes of cats referred to a specialized adoption program for feline leukemia virus (FeLV)-positive cats. Methods Cats referred to an FeLV-specific adoption program between January 2018 and July 2019 at an animal shelter in Austin, TX, USA, were first identified based on their putative FeLV status as reported by the referring shelter, rescue group, veterinarian or individual. Each cat was re-screened for FeLV upon admission and subsequently deemed infected or uninfected. Data on cat source, admission date, outcome date, outcome type, signalment and comorbidities at the time of admission were extracted from the shelter database. Outcomes were recorded up to 15 December 2019. Results In total, 801 cats suspected to be infected with FeLV were referred to the FeLV adoption program. Of these, 149 (18.6%) were ultimately deemed uninfected, and infection was confirmed in 652 (81.4%) cats. Adoption was the most common outcome for FeLV-infected cats (n = 514 cats; 78.8%), followed by euthanasia or death in care (n = 109; 16.7%). Upper respiratory infection (URI) was the most common comorbidity in FeLV-infected cats (n = 106; 16.3%) at the time of admission, which was not significantly different than URI in the cats that were deemed not to be infected with FeLV (n = 29; 19.5%). Conclusions and relevance This study demonstrated high national demand for a lifesaving option for cats diagnosed with FeLV. FeLV infections could not be confirmed in approximately one in five cats referred to the FeLV adoption program, a reminder of the risk behind basing the fate of a cat on a single positive test result. The majority of cats referred to the FeLV program were adopted, demonstrating that programs centered on adopter education and post-adoption support can create lifesaving outcomes for most FeLV-infected cats, despite uncertainty regarding their long-term prognosis.

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Evaluation of a quantitative enzyme-linked immunosorbent assay for feline leukemia virus p27 antigen and comparison to proviral DNA loads by real-time polymerase chain reaction

Cited by 15 publications

References 24 publications

2020 AAFP Feline Retrovirus Testing and Management Guidelines

2020 AAFP Feline Retrovirus Testing and Management Guidelines

Feline Leukemia Virus p27 Antigen Concentration and Proviral DNA Load Are Associated with Survival in Naturally Infected Cats

Outcome of cats referred to a specialized adoption program for feline leukemia virus-positive cats

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