RESUMO
The adenovirus type 2 (Ad2) early region 3 (E3) codes for a 19-kDa glycoprotein (gp19) that associates with the class I major histocompatibility (MHC) heavy chain in the endoplasmic reticulum (ER) and prevents the transport of class I MHC protein products to the cell surface. It has been shown previously in tissue culture that this reduction in class I MHC expression allows infected cells to escape detection by class I MHC restricted CD8+ cytotoxic T-lymphocytes (CTL). We now report the results of studies on the effects of Ad2/gp19 expression on virulence in vivo. Since we wanted to isolate the effect of Ad2/gp19 from the effects of other Ad E3 region gene products and human Ads do not replicate in the mouse, we cloned the Ad2/gp19 open reading frame (ORF) into the HindIII C region of WR vaccinia virus (VV). Two VV recombinants were constructed by inserting the Ad2/gp19 ORF in either an expressing (V-e19(+)) or a non-expressing (V-e19(-)) orientation under control of the VV P7.5 promoter. The V-e19(+)recombinant expressed Ad2/gp19 in infected tissue and could be co-precipitated with an antibody to the class I MHC antigen Kd. However, intracerebral or intranasal infections of BALB/c (H-2d), BALB.G (H-2g), or C3H (H-2k) mice showed that Ad2/gp19 expression by V-e19(+) had no significant effect either on viral lethality or on its ability to replicate in vivo when compared to V-e19(-). Furthermore, the nature of the CD8+ CTL response to a V-e19(+)-induced pneumonia in (H-2d) mice was unchanged by Ad2/gp19 expression. Modulating the CD8+ CTL response, by interfering with infected target presentation, may not be important in the control of VV replication or virulence in vivo when other aspects of the immune response to viral infection are not altered. However, the two VV recombinants V-e19(+) and V-e19(-) were both equally attenuated (10-fold) when compared to wild-type VV. This attenuation, which has been reported previously for an intracerebral infection, is believed to be caused by the disruption of a 37-kDa ORF in the VV HindIII C region. Interestingly, our studies showed that the attenuation is not accompanied by a reduction in viral titers in infected tissue.
Assuntos
Proteínas E3 de Adenovirus/imunologia , Adenovírus Humanos/patogenicidade , Antígenos H-2/imunologia , Camundongos Endogâmicos/imunologia , Pneumonia Viral/imunologia , Proteínas E3 de Adenovirus/genética , Adenovírus Humanos/genética , Adenovírus Humanos/imunologia , Animais , Antígenos CD4/imunologia , Antígenos CD8/imunologia , Modelos Animais de Doenças , Antígenos H-2/genética , Dose Letal Mediana , Pulmão/microbiologia , Pulmão/patologia , Camundongos , Camundongos Endogâmicos BALB C/imunologia , Camundongos Endogâmicos C3H/imunologia , Proteínas Recombinantes/imunologia , Subpopulações de Linfócitos T/imunologia , Vaccinia virus/genética , Ensaio de Placa Viral , VirulênciaRESUMO
Since the E3 region of human adenoviruses codes for a series of proteins that are probably involved in viral pathogenesis, the nucleotide sequence for a 3.6-kilobase DNA fragment in the corresponding region (map units 77 through 89) of the mouse adenovirus type 1 genome has been determined. Analysis of the sequence revealed that the genes for the fiber and for the precursor to the hexon-associated protein, pVIII, that usually flank the E3 region, are well conserved. However, many of the open reading frames contained in the E3 region of human adenoviruses between the pVIII and the fiber genes were absent from the mouse adenovirus type 1 genome.
