No benefit of therapeutic vaccination in clinically healthy cats persistently infected with feline leukemia virus

Helfer-Hungerbuehler, A. Katrin; Spiri, Andrea M.; Riond, Barbara; Grest, Paula; Boretti, Felicitas S; Hofmann‐Lehmann, Regina

doi:10.1016/j.vaccine.2015.02.009

Cited by 10 publications

(9 citation statements)

References 21 publications

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“…In contrast to our results, no beneficial effect on anti-FeLV antibodies or plasma viral load was reported in a FeLV vaccine trial where two licensed prophylactic FeLV vaccines were tested for possible therapeutic potentials in persistently infected cats 25 . Similar to our findings, however, significant progress is being made in the development of therapeutic vaccines against HPV and HIV, although none has been approved for clinical use yet 23 , 26 .…”

Section: Discussioncontrasting

confidence: 99%

Therapeutic vaccination of koalas harbouring endogenous koala retrovirus (KoRV) improves antibody responses and reduces circulating viral load

et al. 2020

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The long-term survival of the koala is under serious threat from multiple factors, including infectious disease agents such as Chlamydia and koala retrovirus (KoRV). KoRV is present in both exogenous and endogenous forms, depending on the geographical location of the population. In the northern half of Australia, it is present as an endogenous infection in all koalas, making a case for an urgent need to develop a therapeutic vaccine that might prevent KoRV-associated pathologies in these koalas. To this end, we determined the therapeutic effects of vaccinating koalas harbouring endogenous KoRV with a recombinant KoRV Env protein combined with a Tri-adjuvant. We found that vaccination led to a significant increase in circulating anti-KoRV IgG levels, as well as increase in neutralising antibodies. Our study also showed that post-vaccination antibodies were able to recognize epitopes on the Env protein that were unrecognised pre-vaccination, as well as resulting in an increase in the recognition of the previously recognised epitopes. The vaccine also induced antibodies that were cross-reactive against multiple KoRV-subtypes. Finally, we found a complete clearance of KoRV-A in plasma from koalas that had detectable levels of KoRV-A pre-vaccination. Similarly, there was a significant reduction in the expression of KoRV-B viral RNA levels post-vaccination. Collectively, this study showed that koalas harbouring endogenous KoRV can benefit from prophylactic vaccination against KoRV using a recombinant KoRV-A Env protein and that the mechanism of this protection might be through the boosting of natural anti-KoRV antibodies and expanding the breadth of the recognised epitopes.

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Section: Discussioncontrasting

confidence: 99%

Therapeutic vaccination of koalas harbouring endogenous koala retrovirus (KoRV) improves antibody responses and reduces circulating viral load

et al. 2020

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“… † euthanized/died a Status observed until 149 weeks post transfusion b Euthanized for humane reasons c During follow-up study, without re-exposure to FeLV [ 35 ] …”

Section: Resultsmentioning

confidence: 99%

“…In week 84, the persistently viremic cat P2 had to be euthanized because of severe dyspnea caused by pleural effusion when the cat was vaccinated but not re-exposed to FeLV (listed as BZ3 in [ 35 ]) in a follow-up study. Cytological examination of the pleural effusion revealed numerous lymphatic blasts with a total nucleated cell count of 40.53 × 10 3 /µL.…”

Section: Resultsmentioning

confidence: 99%

Retroviral DNA—the silent winner: blood transfusion containing latent feline leukemia provirus causes infection and disease in naïve recipient cats

et al. 2015

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Background The feline leukemia virus (FeLV) is a gamma-retrovirus of domestic cats that was discovered half a century ago. Cats that are infected with FeLV may develop a progressive infection resulting in persistent viremia, immunodeficiency, tumors, anemia and death. A significant number of cats mount a protective immune response that suppresses viremia; these cats develop a regressive infection characterized by the absence of viral replication and the presence of low levels of proviral DNA. The biological importance of these latter provirus carriers is largely unknown.ResultsHere, we demonstrate that ten cats that received a transfusion of blood from aviremic provirus carriers developed active FeLV infections, some with a progressive outcome and the development of fatal FeLV-associated disease. The infection outcome, disease spectrum and evolution into FeLV-C in one cat mirrored those of natural infection. Two cats developed persistent antigenemia; six cats were transiently antigenemic. Reactivation of infection occurred in some cats. One recipient developed non-regenerative anemia associated with FeLV-C, and four others developed a T-cell lymphoma, one with secondary lymphoblastic leukemia. Five of the ten recipient cats received provirus-positive aviremic blood, whereas the other five received provirus- and viral RNA-positive but aviremic blood. Notably, the cats that received blood containing only proviral DNA exhibited a later onset but graver outcome of FeLV infection than the cats that were transfused with blood containing proviral DNA and viral RNA. Leukocyte counts and cytokine analyses indicated that the immune system of the latter cats reacted quicker and more efficiently.ConclusionsOur results underline the biological and epidemiological relevance of FeLV provirus carriers and the risk of inadvertent FeLV transmission via blood transfusion and demonstrate the replication capacity of proviral DNA if uncontrolled by the immune system. Our results have implications not only for veterinary medicine, such as the requirement for testing blood donors and blood products for FeLV provirus by sensitive polymerase chain reaction, but are also of general interest by revealing the importance of latent retroviral DNA in infected hosts. When aiming to eliminate a retroviral infection from a population, provirus carriers must be considered.Electronic supplementary materialThe online version of this article (doi:10.1186/s12977-015-0231-z) contains supplementary material, which is available to authorized users.

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“…Administering FeLV vaccines to infected cats is of no therapeutic value and every unnecessary vaccination carries the risk of potential adverse reactions. 99 If a vaccinated cat’s status is unknown and the cat is later determined to have a progressive FeLV infection, vaccine efficacy would be questioned, and vaccine failure suspected. Cats should be tested for FeLV infection before initial vaccination.…”

Section: Prevention Of Retrovirus Infectionsmentioning

confidence: 99%

2020 AAFP Feline Retrovirus Testing and Management Guidelines

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Hartmann³

et al. 2020

Journal of Feline Medicine and Surgery

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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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No benefit of therapeutic vaccination in clinically healthy cats persistently infected with feline leukemia virus

Abstract: Therapeutic vaccinations have a potential application in infections where no curative treatment

Cited by 10 publications

References 21 publications

Therapeutic vaccination of koalas harbouring endogenous koala retrovirus (KoRV) improves antibody responses and reduces circulating viral load

Therapeutic vaccination of koalas harbouring endogenous koala retrovirus (KoRV) improves antibody responses and reduces circulating viral load

Retroviral DNA—the silent winner: blood transfusion containing latent feline leukemia provirus causes infection and disease in naïve recipient cats

2020 AAFP Feline Retrovirus Testing and Management Guidelines

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