Rift Valley Fever Vaccine Virus Clone 13 Is Able to Cross the Ovine Placental Barrier Associated with Foetal Infections, Malformations, and Stillbirths

• Published in: PLoS neglected tropical diseases Vol. 10; no. 3; p. e0004550
• Main Authors: Makoschey, Birgit, van Kilsdonk, Emma, Hubers, Willem R, Vrijenhoek, Mieke P, Smit, Marianne, Wichgers Schreur, Paul J, Kortekaas, Jeroen, Moulin, Véronique
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 31.03.2016; Public Library of Science (PLoS)
• Subjects: Animals; Antibodies, Viral - blood; Biology and Life Sciences; Births; Care and treatment; Cloning; Congenital Abnormalities - veterinary; Congenital Abnormalities - virology; CVI Virologie; CVI Virology; Diagnosis; Dose-Response Relationship, Immunologic; Experiments; Female; Fetuses; Fever; Health aspects; Infections; Infectious Disease Transmission, Vertical - veterinary; Medicine and Health Sciences; Mortality; Mosquitoes; Overdose; Placenta; Pregnancy; Pregnancy Complications, Infectious - veterinary; Pregnancy Complications, Infectious - virology; Research and Analysis Methods; Rift valley fever; Rift Valley Fever - prevention & control; Rift Valley Fever - transmission; Rift Valley Fever - virology; Rift Valley fever virus; Rift Valley fever virus - classification; Rift Valley fever virus - pathogenicity; Rift Valley fever virus - physiology; Risk factors; Ruminantia; Sheep; Sheep Diseases - etiology; Sheep Diseases - pathology; Sheep Diseases - prevention & control; Stillbirth; Stillbirth - veterinary; Studies; Tropical diseases; Vaccines; Vector-borne diseases; Viral vaccines; Viral Vaccines - adverse effects; Viral Vaccines - immunology; Virologie; Virology; Virulence; Virus Shedding; Europe; ANE, Europe; Africa
• ISSN: 1935-2735; 1935-2727; 1935-2735
• DOI: 10.1371/journal.pntd.0004550

Rift Valley fever virus (RVFV) is a mosquito-borne pathogen that affects domesticated ruminants and occasionally humans. Classical RVF vaccines are based on formalin-inactivated virus or the live-attenuated Smithburn strain. The inactivated vaccine is highly safe but requires multiple administrations and yearly re-vaccinations. Although the Smithburn vaccine provides solid protection after a single vaccination, this vaccine is not safe for pregnant animals. An alternative live-attenuated vaccine, named Clone 13, carries a large natural deletion in the NSs gene which encodes the major virulence factor of the virus. The Clone 13 vaccine was previously shown to be safe for young lambs and calves. Moreover, a study in pregnant ewes suggested that the vaccine could also be applied safely during gestation. To anticipate on a possible future incursion of RVFV in Europe, we have evaluated the safety of Clone 13 for young lambs and pregnant ewes. In line with the guidelines from the World Organisation for Animal health (Office International des Epizooties, OIE) and regulations of the European Pharmacopeia (EP), these studies were performed with an overdose. Our studies with lambs showed that Clone 13 dissemination within vaccinated animals is very limited. Moreover, the Clone 13 vaccine virus was not shed nor spread to in-contact sentinels and did not revert to virulence upon animal-to-animal passage. Importantly, a large experiment with pregnant ewes demonstrated that the Clone 13 virus is able to spread to the fetus, resulting in malformations and stillbirths. Altogether, our results suggest that Clone 13 can be applied safely in lambs, but that caution should be taken when Clone 13 is used in pregnant animals, particularly during the first trimester of gestation.