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Modumo J.,Onderstepoort Biological Products Ltd. | Venter E.H.,University of Pretoria
Journal of the South African Veterinary Association | Year: 2012

Recent outbreaks of bluetongue virus (BTV) serotypes 2 and 8 in many European countries provided an opportunity to investigate the possibility of improving the safety of the modified live vaccines administered mainly in South Africa. Modified live vaccines (MLV) released at a titre of 5 × 104 PFU/mL, raised concerns and prompted the need to determine the minimum titre which will still be protective and also safe. The BTV serotypes 2 and 8 vaccines were produced at the following titres: 102 PFU/mL, 103 PFU/mL and 104 PFU/mL, and were injected into 24 sheep which were then monitored. Blood was collected on days 0, 3, 6, 9, 12, 15, 18, 21, 25, 28 and 4 months post vaccination, for seroconversion and viraemia studies. These sheep were later challenged at 4 months post vaccination using BTV infected cell culture material, they were then observed and bled and again tested for viraemia. There was no viraemia post vaccination, however, a febrile reaction did occur and seroconversion was demonstrated at low titres for both BTV 2 and 8. Although viraemia was demonstrated post challenge, sheep vaccinated with the low titre BTV 2 vaccine showed more than a 90% protection index at a lower titre of 103 PFU/mL, compared with BTV 8 that showed a protection index above 90% at all the titres used. It is recommended that for BTV 2 vaccine, sheep should be vaccinated at a titre of 103 PFU/mL and at a titre of 102 PFU/mL with BTV 8 vaccine. © 2012.

Dungu B.,Onderstepoort Biological Products Ltd. | Louw I.,Onderstepoort Biological Products Ltd. | Lubisi A.,Onderstepoort Veterinary Institute | Hunter P.,Onderstepoort Biological Products Ltd. | And 2 more authors.
Vaccine | Year: 2010

The efficacy and safety of the naturally attenuated Rift Valley Fever (RVF) Clone 13 vaccine were evaluated in ovines in three different experiments involving 38 ewes at different stages of pregnancy, their offsprings and four rams. In Experiment 1, 4 rams and a total of 13 pregnant ewes were vaccinated and monitored during vaccination and after a challenge with a virulent RVF virus. The ewes were vaccinated at either 50 or 100 days of pregnancy and some were challenged after lambing. In Experiment 2, nine oestrus-synchronized ewes were vaccinated at 50 days of pregnancy and challenged at 100 days of pregnancy together with 5 unvaccinated ewes at the same stage of pregnancy. In Experiment 3, 16 oestrus-synchronized ewes were vaccinated with 3 different doses of the RVF Clone 13 vaccine and challenged together with unvaccinated pregnant ewes at either 30 or 50 days of pregnancy. The results from the three experiments indicated that the vaccine did not induce clinical manifestation of RVF such as abortion in pregnant ewes, teratogeny in their offsprings, or pyrexia in all vaccinated animals. Vaccination with RVF Clone 13 vaccine also prevented clinical RVF following virulent challenge at different stages of pregnancy while unvaccinated control ewes showed pyrexia, aborted or died of RVF. A vaccine dose-response effect was also observed. © 2010 Elsevier Ltd. All rights reserved.

Von Teichman B.,Onderstepoort Biological Products Ltd. | Engelbrecht A.,Onderstepoort Biological Products Ltd. | Zulu G.,Onderstepoort Biological Products Ltd. | Dungu B.,GalVmed Doherty Building Pentlands | And 2 more authors.
Vaccine | Year: 2011

Two modified live attenuated vaccines against the disease Rift Valley fever (RVF) have been tested for safety and efficacy in young calves. The RVF Smithburn vaccine produced in South Africa and used successfully to prevent and control the disease in endemic sub-Saharan countries was compared to the candidate vaccine RVF Clone 13. Five sero-negative calves per vaccine group were vaccinated with a single dose of each vaccine and tested for antibody response. All vaccinated calves were challenged with a highly virulent RVF virus together with five unvaccinated calves used as control of the challenge. Protection was confirmed in all vaccinated animals as they did not show any clinical signs typical of RVF. A good neutralizing antibody response was induced post-vaccination and no viraemia could be detected post-challenge in calves of both vaccine groups. All non-vaccinated control animals showed clinical symptoms of RVF, high viraemia and were euthanized. This study reported the first case of blindness in cattle resulting from virulent RVF virus infection in unvaccinated calves used as negative controls. © 2011 Elsevier Ltd.

von Teichman B.F.,Onderstepoort Biological Products Ltd. | Dungu B.,Onderstepoort Biological Products Ltd. | Smit T.K.,Onderstepoort Biological Products Ltd.
Vaccine | Year: 2010

The polyvalent African horsesickness (AHS) attenuated live virus (AHS-ALV) vaccine produced at Onderstepoort Biological Products incorporates 7 of the 9 known serotypes circulating in southern Africa. Serological cross-reaction has been shown in vitro to Serotypes 5 and 9 by Serotypes 8 and 6 respectively, but the degree of in vivo cross-protection between these serotypes in vaccinated horses has not previously been reported. Due to the increasing incidence of AHS Serotypes 5 and 9 in the field, over the last 3-4 seasons of AHS in South Africa, and the absence of Serotypes 5 and 9 in the AHS-ALV vaccine, it was necessary to conduct a vaccination-challenge study to determine in vivo cross-protection of vaccine-incorporated Serotypes 8 and 6 respectively. Groups of horses were vaccinated with either the polyvalent AHS-ALV vaccine or a monovalent Serotype 6 (vAHSV6) or 8 (vAHSV8) vaccine to determine the cross-protection of vaccinated horses following challenge with virulent AHS virus (AHSV) of either Serotype 5, 6, 8 or 9. Serial vaccination of naive horses with the polyvalent AHS-ALV vaccine generated a broad neutralizing antibody response to all vaccine strains as well as cross-neutralizing antibodies to Serotypes 5 and 9. Booster vaccination of horses with monovalent vaccine vAHSV6 or vAHSV8 induced an adequate protective immune response to challenge with homologous and heterologous virulent virus. In vivo cross-protection between AHSV6 and AHSV9 and AHSV8 and AHSV5 respectively, was demonstrated. © 2010 Elsevier Ltd.

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