Isolation and characterization of a highly attenuated respiratory syncytial virus (RSV) vaccine candidate by mutagenesis of the incompletely attenuated RSV A2 ts-1 NG-1 mutant virus.
Ts-1, a temperature sensitive (ts) mutant of RSV, was previously derived from RSV A2 virus by mutagenesis with 5-fluorouracil (5-FU). Ts-1 was attenuated for adult volunteers and seropositive children but retained a low level of virulence in seronegative infant vaccinees as indicated by the occurrence of upper respiratory tract disease. Ts-1 NG-1, a more defective derivative of ts-1, was produced by mutagenesis of ts-1 with nitrosoguanidine. However, ts-1 NG-1 still retained a low level of virulence for the upper respiratory tract and showed some genetic instability in chimpanzees. With renewed interest in the goal of developing a live, attenuated RSV vaccine, we have now attempted to further attenuate ts-1 NG-1 by mutagenesis with 5-FU and 5-azacytidine. Four mutants that are phenotypically different from the ts-1 NG-1 parental virus were identified. Each of the four mutants was more restricted in replication in BALB/c mice compared with the ts-1 NG-1 parental virus. One of the ts-1 NG-1 derivatives, termed A-20-4, which showed the lowest (35 degrees C) in vitro shutoff temperature and which was also completely restricted in replication in BALB/c mice, was selected for further evaluation in seronegative chimpanzees. A-20-4 did not cause rhinorrhea in chimpanzees but induced detectable titers of serum RSV neutralizing antibodies in 2 of 4 chimpanzees. Apparent complete protection to subsequent challenge with wild-type RSV was observed in each of the four chimpanzees previously immunized with A-20-4.(ABSTRACT TRUNCATED AT 250 WORDS)
Hsu
K H
KH
Wyeth-Ayerst Research, Philadelphia, PA 19101, USA.
Crowe
J E
JE
Lubeck
M D
MD
Davis
A R
AR
Hung
P P
PP
Chanock
R M
RM
Murphy
B R
BR
D000818:Animals; D001374:Azacitidine / Q000494:pharmacology; D002294:Carcinoma, Squamous Cell / Q000821:virology; D002522:Chlorocebus aethiops; D005260:Female; D005472:Fluorouracil / Q000494:pharmacology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D016296:Mutagenesis; D002679:Pan troglodytes; D010641:Phenotype; D018357:Respiratory Syncytial Virus Infections / Q000276:immunology / Q000517:prevention & control; D018113:Respiratory Syncytial Virus, Human / Q000235:genetics* / Q000276:immunology*; D013696:Temperature; D014407:Tumor Cells, Cultured; D014613:Vaccines, Attenuated / Q000235:genetics* / Q000302:isolation & purification*; D014709:Vero Cells; D014765:Viral Vaccines / Q000235:genetics* / Q000302:isolation & purification*; D014779:Virus Replication / Q000502:physiology
D014613:Vaccines, Attenuated; D014765:Viral Vaccines; D001374:Azacitidine; D005472:Fluorouracil