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.
Funkhouser
A W
AW
Hepatitis Viruses Section, Laboratory of Infectious Diseases, National Institutes of Allergy and Infectious Diseases, Bethesda, Maryland 20892, USA.
Raychaudhuri
G
G
Purcell
R H
RH
Govindarajan
S
S
Elkins
R
R
Emerson
S U
SU
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