Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “MP-12 strain”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

5 recordsLinked to original sources
PubMed2025

Efficient Expression of Oropouche Virus Nonstructural Proteins NSs and NSm.

Oropouche fever, a mosquito- or midge-borne emerging zoonotic disease endemic to South and Central America, manifests as a dengue-like acute febrile illness with occasional occurrences of meningitis or meningoencephalitis. The causative agent, Oropouche virus (OROV), belongs to the genus Orthobunyavirus within the family Peribunyaviridae. Its tripartite negative-sense RNA genome comprises small (S), medium (M), and large (L) segments, encoding structural N, Gn/Gc, and L proteins, respectively. Additionally, the S- and M-segments encode nonstructural proteins: NSs and NSm, which may act as virulence factors. OROV NSs functions as an interferon antagonist with an unknown mechanism, while the roles of OROV NSm remain elusive. This chapter introduces efficient expression systems for OROV NSm and NSs proteins. Validating the presence of a signal peptide at the N-terminus of NSm protein is essential for its expression. Furthermore, expressing OROV NSs protein independently of an RNA polymerase II promoter is crucial to prevent restricted gene expression, potentially caused by NSs inhibiting cellular RNA polymerase II, as observed in closely related bunyavirus NSs proteins. These protein expression strategies offer insights into the molecular characterization of OROV NSm and NSs proteins, facilitating a deeper understanding of their virulence mechanisms.

Viral Nonstructural Proteins↗
PubMed1995

Characterization of clone 13, a naturally attenuated avirulent isolate of Rift Valley fever virus, which is altered in the small segment.

The 74HB59 strain of Rift Valley fever (RVF) virus, isolated from a human case in the Central African Republic, was shown to be composed of a heterogeneous population of viruses when plaque-purified clones were analyzed for their reactivity with monoclonal antibodies (MAbs) directed against the nucleocapsid (N) protein or the nonstructural (NSs) protein. One of these clones, C13, was of particular interest in that it proved to be avirulent in mice and hamsters, and highly immunogenic. Although C13 showed normal reactivity with a large panel of MAbs directed at the glycoproteins, it failed to react with specific MAbs or polyclonal antibodies directed at the NSs protein and with a specific MAb recognizing the N protein of the Egyptian strains. Consequently, the small RNA segment, which encodes the N and NSs proteins in an ambisense strategy, was sequenced and compared with the existing sequence of the attenuated MP-12 RVF virus strain. We found that the NSs gene contained, in addition to two conservative coding changes, a large internal deletion of 549 nucleotides that removes 69% of the open reading frame but conserves in-frame the N and C termini of the predicted translation product. In addition, the sequence revealed that the N protein of C13 contained a single amino acid change. Clone C13 replicated normally in certain cell types in vitro and in Culex pipiens mosquitoes after intrathoracic inoculation, but established abortive infections in MRC-5 human fibroblasts.

Animals↗
PubMed1990

Use of reassortant viruses to map attenuating and temperature-sensitive mutations of the Rift Valley fever virus MP-12 vaccine.

A live-attenuated vaccine for Rift Valley fever virus (RVFV), MP-12, has been developed recently by undirected, serial mutagenesis of a RVFV strain (ZH548) isolated during the 1977 epidemic in Egypt. In the present study, the mutations responsible for attenuation of this virus have been examined by analysis of reassortant viruses generated between the vaccine strain and a wild RVFV strain isolated in Senegal. Reassortant viruses were generated efficiently in multiply infected Vero cells, and were readily isolated without application of selective pressures. The origin of the S and M genomic RNA segments in each cloned reassortant virus was determined with monoclonal antibodies capable of differentiating the nucleocapsid protein (S segment marker) or G1 glycoprotein (M segment marker) of the parental strains. The L segment of the vaccine strain was found to contain a temperature-sensitive (ts) mutation, and the origin of the L segment in most reassortants could be inferred by analysis of their ts phenotype. Analysis of the virulence properties of selected reassortant viruses in mice demonstrated that virulence characteristics were under polygenic control, and that at least one mutation capable of independently attenuating the virus existed on each genome segment. The L and M RNA segments were also found to contain ts mutations. These findings suggest that reversion to virulence is unlikely, and further indicate that genetic reassortment with wild-type viruses during a vaccination programme in endemic areas would also be expected to yield attenuated variants.

Animals↗
PubMed1991

Further evaluation of a mutagen-attenuated Rift Valley fever vaccine in sheep.

A previous study demonstrated that a mutagen-attenuated Rift Valley fever virus (RVFV) vaccine, RVF MP-12, was immunogenic and non-abortogenic when ewes, 90-110 days pregnant, were inoculated with 5 x 10(5) plaque-forming units (p.f.u.) of the virus strain. The ewes delivered live, healthy lambs that had no neutralizing antibody to RVFV until after they had ingested colostrum. To assess further the safety and protective capability of this candidate vaccine, six pregnant ewes were inoculated with 5 x 10(3) p.f.u. of RVF MP-12 and challenged with 5 x 10(5) p.f.u. of virulent ZH-501 strain of RVFV 30 days later. No viraemia was detected after vaccination or challenge and all six ewes delivered live, healthy lambs. Those lambs tested before their nursing did not have neutralizing antibody to RVFV but quickly acquired antibody titres of 1:320 to greater than or equal to 1:10,240 after ingesting colostrum. To test the safety of the RVF MP-12 immunogen in neonates, lambs less than or equal to 7 days old, born to unvaccinated ewes, were inoculated with 5 x 10(5) p.f.u. of RVF MP-12. With the exception of brief pyrexia in 18 of 26 lambs, and a transient low-titred viraemia in 16 of 26 lambs after inoculation, no untoward effects were observed. Serum-neutralizing antibody to RVFV was detected 5-7 days after inoculation. Lambs vaccinated with either 5 x 10(5) or 5 x 10(3) p.f.u. of RVF MP-12 were protected against virulent RVFV challenge at 14 days postvaccination.

Animals↗
PubMed1997

Safety of a mutagen-attenuated Rift Valley fever virus vaccine in fetal and neonatal bovids.

OBJECTIVE: To examine effects of in utero inoculation with a mutagen-attenuated Rift Valley fever virus (RVFV) vaccine (RVF MP-12) on fetal bovids and to assess the safety and efficacy of calfhood vaccination with RVF MP-12. ANIMALS: 18 pregnant Hereford and Hereford-type cows in the third or fifth month of gestation, their progeny, and 25 calves from cows immunized with RVF MP-12 during pregnancy. PROCEDURE: Bovine fetuses were inoculated, via laparotomy, with 1 ml of RVF MP-12 containing 5 log10 plaque-forming units (PFU) of virus. Blood was obtained from newborn calves prior to their ingestion of colostrum. Immune-naive calves and calves born to RVF MP-12-vaccinated dams, ranging in age from 2 to 45 days, were vaccinated with RVF MP-12, and some were later challenge exposed with 1 ml of 5.7 log10 PFU of virulent RVFV strain ZH-501. Cows were monitored for viremia and antibody responses and for hematologic and serum biochemical alterations through parturition or abortion. RESULTS: Surviving in utero-vaccinated calves were healthy, with no noticeable defects. Except for 1 vaccine-inoculated fetus that died on postinoculation day 21, all in utero-vaccinated fetuses had serum neutralizing antibody titer > or = 1:20 at the time of delivery. All dams of in utero-vaccinated fetuses also developed neutralizing antibody titer. Calves born to cows vaccinated during gestation did not have antibody at birth, and all but 1 quickly acquired colostral antibody. Postparturient inoculation of immune-naive calves and calves with colostral antibodies resulted in no untoward effects, and all calves with detectable neutralizing antibodies were protected against virulent virus challenge exposure. CONCLUSIONS: Fetal death and abortion would be rare even if fetuses were exposed to RVF MP-12. The trauma and complications associated with in utero inoculation do not make this a practical method of immunization. RVF MP-12 was safe, immunogenic, and protective in calves as young as 2 days of age.

Abortion, Veterinary↗