Progress toward the development of a genetically engineered attenuated hepatitis A virus vaccine.
Mutations which positively affect growth of hepatitis A virus in cell culture may negatively affect growth in vivo. Therefore, development of an attenuated vaccine for hepatitis A may require a careful balancing of mutations to produce a virus that will grow efficiently in cells suitable for vaccine production and still maintain a satisfactory level of attenuation in vivo. Since such a balance could be achieved most directly by genetic engineering, we are analyzing mutations that accumulated during serial passage of the HM-175 strain of hepatitis A virus in MRC-5 cell cultures in order to determine the relative importance of the mutations for growth in MRC-5 cells and for attenuation in susceptible primates. Chimeric viral genomes of the HM-175 strain were constructed from cDNA clones derived from a virulent virus and from two attenuated viruses adapted to growth in African green monkey kidney (AGMK) and MRC-5 cells, respectively. Viruses encoded by these chimeric genomes were recovered by in vitro or in vivo transfection and assessed for their ability to grow in cultured MRC-5 cells or to cause hepatitis in primates (tamarins). The only MRC-5-specific mutations that substantially increased the efficiency of growth in MRC-5 cells were a group of four mutations in the 5' noncoding (NC) region. These 5' NC mutations and a separate group of 5' NC mutations that accumulated during earlier passages of the HM-175 virus in primary AGMK cells appeared, independently and additively, to result in decreased biochemical evidence of hepatitis in tamarins. However, neither group of 5' NC mutations had a demonstrable effect on the extent of virus excretion or liver pathology in these animals.
Hepatitis Viruses Section, Laboratory of Infectious Diseases, National Institutes of Allergy and Infectious Diseases, Bethesda, Maryland 20892, USA.
A W
AW
Funkhouser
G
G
Raychaudhuri
R H
RH
Purcell
S
S
Govindarajan
R
R
Elkins
S U
SU
Emerson
D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D005818:Genetic Engineering; D022362:Hepatitis A Vaccines; D006507:Hepatovirus / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D006801:Humans; D016296:Mutagenesis; D012452:Saguinus; D014613:Vaccines, Attenuated / Q000235:genetics*; D014614:Vaccines, Synthetic; D014761:Viral Hepatitis Vaccines / Q000235:genetics*
D022362:Hepatitis A Vaccines; D014613:Vaccines, Attenuated; D014614:Vaccines, Synthetic; D014761:Viral Hepatitis Vaccines