A Novel, Safe, Non-Adjuvanted Alphavirus Replicon-Based Vaccine Expressing the Feline Leukemia Virus Envelope Protein Protects Against Virulent FeLV Challenge
<b>Background/Objectives:</b> A number of different vaccines against feline leukemia virus (FeLV) are available; however, there is continuous debate regarding the efficacy advantages of adjuvanted vaccines versus the potential safety advantages of non-adjuvanted vaccines. <b>Method...
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2025-06-01
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| author | Kari Carritt Randall Davis Ken Stachura Paige Crumley Mark Mogler Madeleine Stahl Lijuan Deng Zach Xu Ian Tarpey |
| author_facet | Kari Carritt Randall Davis Ken Stachura Paige Crumley Mark Mogler Madeleine Stahl Lijuan Deng Zach Xu Ian Tarpey |
| author_sort | Kari Carritt |
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| description | <b>Background/Objectives:</b> A number of different vaccines against feline leukemia virus (FeLV) are available; however, there is continuous debate regarding the efficacy advantages of adjuvanted vaccines versus the potential safety advantages of non-adjuvanted vaccines. <b>Methods:</b> For this reason, we developed a non-adjuvanted vaccine based on a replicon RNA particle (RP) expressing the FeLV gp85 envelope protein, which possesses the safety of a non-adjuvanted vaccine while consistently providing high efficacy. <b>Results:</b> In two efficacy studies, a high-level of protection against virulent FeLV challenge was demonstrated with two doses given 3 weeks apart based on the prevention of FeLV p27 antigenemia. Furthermore, in both studies, we compared this novel vaccine against a non-adjuvanted, canarypox-vectored FeLV vaccine, demonstrating that none of the cats that received two doses of the RP-FeLV vaccine developed persistent antigenemia post-challenge. In comparison, of cats receiving the canarypox-vectored FeLV vaccine, three of seven (43%) became persistently antigenemic in one study, and three of ten (30%) became persistently antigenemic in the other study. In a field safety study using two commercial serials, safety of the RP-FeLV vaccine was demonstrated in over 800 cats receiving two doses of the vaccine. <b>Conclusions:</b> These data suggest that the RP-FeLV vaccine offers advantages over some current FeLV vaccines by combining the safety profile of a non-adjuvanted vaccine with the induction of a robust immune response demonstrated by some adjuvanted vaccines. |
| format | Article |
| id | doaj-art-7f067d58252945b79990a2ed910ea8ad |
| institution | DOAJ |
| issn | 2076-393X |
| language | English |
| publishDate | 2025-06-01 |
| publisher | MDPI AG |
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| series | Vaccines |
| spelling | doaj-art-7f067d58252945b79990a2ed910ea8ad2025-08-20T02:47:22ZengMDPI AGVaccines2076-393X2025-06-0113769710.3390/vaccines13070697A Novel, Safe, Non-Adjuvanted Alphavirus Replicon-Based Vaccine Expressing the Feline Leukemia Virus Envelope Protein Protects Against Virulent FeLV ChallengeKari Carritt0Randall Davis1Ken Stachura2Paige Crumley3Mark Mogler4Madeleine Stahl5Lijuan Deng6Zach Xu7Ian Tarpey8Research and Development Department, Merck Animal Health, Elkhorn, NE 68022, USAResearch and Development Department, Merck Animal Health, Elkhorn, NE 68022, USAResearch and Development Department, Merck Animal Health, Elkhorn, NE 68022, USAResearch and Development Department, Merck Animal Health, Elkhorn, NE 68022, USAResearch and Development Department, Merck Animal Health, Ames, IA 50010, USAVeterinary Insights and Medical Affairs, Merck Animal Health, Rahway, NJ 07065, USAGlobal Statistics and Data Management, Merck Animal Health, Elkhorn, NE 68022, USAResearch and Development Department, Merck Animal Health, Elkhorn, NE 68022, USAResearch and Development Department, MSD Animal Health, 5831 AN Boxmeer, The Netherlands<b>Background/Objectives:</b> A number of different vaccines against feline leukemia virus (FeLV) are available; however, there is continuous debate regarding the efficacy advantages of adjuvanted vaccines versus the potential safety advantages of non-adjuvanted vaccines. <b>Methods:</b> For this reason, we developed a non-adjuvanted vaccine based on a replicon RNA particle (RP) expressing the FeLV gp85 envelope protein, which possesses the safety of a non-adjuvanted vaccine while consistently providing high efficacy. <b>Results:</b> In two efficacy studies, a high-level of protection against virulent FeLV challenge was demonstrated with two doses given 3 weeks apart based on the prevention of FeLV p27 antigenemia. Furthermore, in both studies, we compared this novel vaccine against a non-adjuvanted, canarypox-vectored FeLV vaccine, demonstrating that none of the cats that received two doses of the RP-FeLV vaccine developed persistent antigenemia post-challenge. In comparison, of cats receiving the canarypox-vectored FeLV vaccine, three of seven (43%) became persistently antigenemic in one study, and three of ten (30%) became persistently antigenemic in the other study. In a field safety study using two commercial serials, safety of the RP-FeLV vaccine was demonstrated in over 800 cats receiving two doses of the vaccine. <b>Conclusions:</b> These data suggest that the RP-FeLV vaccine offers advantages over some current FeLV vaccines by combining the safety profile of a non-adjuvanted vaccine with the induction of a robust immune response demonstrated by some adjuvanted vaccines.https://www.mdpi.com/2076-393X/13/7/697feline leukemia virusRNA particleenvelope proteinvaccineefficacysafety |
| spellingShingle | Kari Carritt Randall Davis Ken Stachura Paige Crumley Mark Mogler Madeleine Stahl Lijuan Deng Zach Xu Ian Tarpey A Novel, Safe, Non-Adjuvanted Alphavirus Replicon-Based Vaccine Expressing the Feline Leukemia Virus Envelope Protein Protects Against Virulent FeLV Challenge Vaccines feline leukemia virus RNA particle envelope protein vaccine efficacy safety |
| title | A Novel, Safe, Non-Adjuvanted Alphavirus Replicon-Based Vaccine Expressing the Feline Leukemia Virus Envelope Protein Protects Against Virulent FeLV Challenge |
| title_full | A Novel, Safe, Non-Adjuvanted Alphavirus Replicon-Based Vaccine Expressing the Feline Leukemia Virus Envelope Protein Protects Against Virulent FeLV Challenge |
| title_fullStr | A Novel, Safe, Non-Adjuvanted Alphavirus Replicon-Based Vaccine Expressing the Feline Leukemia Virus Envelope Protein Protects Against Virulent FeLV Challenge |
| title_full_unstemmed | A Novel, Safe, Non-Adjuvanted Alphavirus Replicon-Based Vaccine Expressing the Feline Leukemia Virus Envelope Protein Protects Against Virulent FeLV Challenge |
| title_short | A Novel, Safe, Non-Adjuvanted Alphavirus Replicon-Based Vaccine Expressing the Feline Leukemia Virus Envelope Protein Protects Against Virulent FeLV Challenge |
| title_sort | novel safe non adjuvanted alphavirus replicon based vaccine expressing the feline leukemia virus envelope protein protects against virulent felv challenge |
| topic | feline leukemia virus RNA particle envelope protein vaccine efficacy safety |
| url | https://www.mdpi.com/2076-393X/13/7/697 |
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