Dataset Information

Oligomers of hepatitis A virus (HAV) capsid protein VP1 generated in a heterologous expression system.

ABSTRACT:

Background

The quasi-enveloped picornavirus, Hepatitis A Virus (HAV), causes acute hepatitis in humans and infects approximately 1.5 million individuals a year, which does not include the asymptomatically infected population. Several severe outbreaks in developing nations in recent years have highlighted the reduction in HAV endemicity, which increases the risk of infections in the vulnerable population. The current HAV vaccines are based on growing wildtype or attenuated virus in cell culture, which raises the cost of production. For generation of cheaper, subunit vaccines or strategies for antibody-based diagnostics, production of viral structural proteins in recombinant form in easily accessible expression systems is a priority.

Results

We attempted several strategies for recombinant production of one of the major capsid proteins VP1, from HAV, in the E. coli expression system. Several efforts resulted in the formation of soluble aggregates or tight association of VP1 with the bacterial chaperone GroEL. Correctly folded VP1 was eventually generated in a discrete oligomeric form upon purification of the protein from inclusion bodies and refolding. The oligomers resemble oligomers of capsid proteins from other picornaviruses and appear to have the correct secondary and antigenic surface structure.

Conclusions

VP1 oligomers generated in the bacterial expression system can be utilized for understanding the molecular pathway of HAV capsid assembly and may also have potential biomedical usages in prevention and diagnostics of HAV infections.

SUBMITTER: Nain A

PROVIDER: S-EPMC8991588 | biostudies-literature | 2022 Apr

REPOSITORIES: biostudies-literature

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Publications

Oligomers of hepatitis A virus (HAV) capsid protein VP1 generated in a heterologous expression system.

Nain Anshu A Kumar Mohit M Banerjee Manidipa M

Microbial cell factories 20220407 1

<h4>Background</h4>The quasi-enveloped picornavirus, Hepatitis A Virus (HAV), causes acute hepatitis in humans and infects approximately 1.5 million individuals a year, which does not include the asymptomatically infected population. Several severe outbreaks in developing nations in recent years have highlighted the reduction in HAV endemicity, which increases the risk of infections in the vulnerable population. The current HAV vaccines are based on growing wildtype or attenuated virus in cell c ...[more]

PMID: 35392916

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Project description:Hepatitis A virus (HAV) infection often causes acute hepatitis, which results in a case fatality rate of 0.2% and fulminant hepatitis in 0.5% of cases. However, no specific potent anti-HAV drug is available on the market to date. In the present study, we focused on inhibition of HAV internal ribosomal entry site (IRES)-mediated translation and investigated novel therapeutic drugs through drug repurposing by screening for inhibitors of HAV IRES-mediated translation and cell viability using a reporter assay and cell viability assay, respectively. The initial screening of 1,158 drugs resulted in 77 candidate drugs. Among them, nicotinamide significantly inhibited HAV HA11-1299 genotype IIIA replication in Huh7 cells. This promising drug also inhibited HAV HM175 genotype IB subgenomic replicon and HAV HA11-1299 genotype IIIA replication in a dose-dependent manner. In the present study, we found that nicotinamide inhibited the activation of activator protein 1 (AP-1) and that knockdown of c-Jun, which is one of the components of AP-1, inhibited HAV HM175 genotype IB IRES-mediated translation and HAV HA11-1299 genotype IIIA and HAV HM175 genotype IB replication. Taken together, the results showed that nicotinamide inhibited c-Jun, resulting in the suppression of HAV IRES-mediated translation and HAV replication, and therefore, it could be useful for the treatment of HAV infection. IMPORTANCE Drug screening methods targeting HAV IRES-mediated translation with reporter assays are attractive and useful for drug repurposing. Nicotinamide (vitamin B3, niacin) has been shown to effectively inhibit HAV replication. Transcription complex activator protein 1 (AP-1) plays an important role in the transcriptional regulation of cellular immunity or viral replication. The results of this study provide evidence that AP-1 is involved in HAV replication and plays a role in the HAV life cycle. In addition, nicotinamide was shown to suppress HAV replication partly by inhibiting AP-1 activity and HAV IRES-mediated translation. Nicotinamide may be useful for the control of acute HAV infection by inhibiting cellular AP-1 activity during HAV infection processes.

Project description:The hepatitis A virus (HAV) cellular receptor 1 (HAVCR1), classified as CD365, was initially discovered as an HAV cellular receptor using an expression cloning strategy. Due to the lack of HAV receptor-negative replication-competent cells, it was not possible to fully prove that HAVCR1 was a functional HAV receptor. However, biochemistry, classical virology, and epidemiology studies further supported the functional role of HAVCR1 as an HAV receptor. Here, we show that an anti-HAVCR1 monoclonal antibody that protected African green monkey kidney (AGMK) cells against HAV infection only partially protected monkey Vero E6 cells and human hepatoma Huh7 cells, indicating that these two cell lines express alternative yet unidentified HAV receptors. Therefore, we focused our work on AGMK cells to further characterize the function of HAVCR1 as an HAV receptor. Advances in clustered regularly interspaced short palindromic repeat/Cas9 technology allowed us to knock out the monkey ortholog of HAVCR1 in AGMK cells. The resulting AGMK HAVCR1 knockout (KO) cells lost susceptibility to HAV infection, including HAV-free viral particles (vpHAV) and exosomes purified from HAV-infected cells (exo-HAV). Transfection of HAVCR1 cDNA into AGMK HAVCR1 KO cells restored susceptibility to vpHAV and exo-HAV infection. Furthermore, transfection of the mouse ortholog of HAVCR1, mHavcr1, also restored the susceptibility of AGMK HAVCR1 KO cells to HAV infection. Taken together, our data clearly show that HAVCR1 and mHavcr1 are functional HAV receptors that mediate HAV infection. This work paves the way for the identification of alternative HAV receptors to gain a complete understanding of their interplay with HAVCR1 in the cell entry and pathogenic processes of HAV.IMPORTANCE HAVCR1, an HAV receptor, is expressed in different cell types, including regulatory immune cells and antigen-presenting cells. How HAV evades the immune response during a long incubation period of up to 4 weeks and the mechanism by which the subsequent necroinflammatory process clears the infection remain a puzzle that most likely involves the HAV-HAVCR1 interaction. Based on negative data, a recent paper from the S. M. Lemon and W. Maury laboratories (A. Das, A. Hirai-Yuki, O. Gonzalez-Lopez, B. Rhein, S. Moller-Tank, R. Brouillette, L. Hensley, I. Misumi, W. Lovell, J. M. Cullen, J. K. Whitmire, W. Maury, and S. M. Lemon, mBio 8:e00969-17, 2017, https://doi.org/10.1128/mBio.00969-17) suggested that HAVCR1 is not a functional HAV receptor, nor it is it required for HAV infection. However, our data, based on regain of the HAV receptor function in HAVCR1 knockout cells transfected with HAVCR1 cDNA, disagree with their findings. Our positive data show conclusively that HAVCR1 is indeed a functional HAV receptor and lays the ground for the identification of alternative HAV receptors and how they interact with HAVCR1 in cell entry and the pathogenesis of HAV.

Dataset Information

Oligomers of hepatitis A virus (HAV) capsid protein VP1 generated in a heterologous expression system.

Background

Results

Conclusions

Publications

Oligomers of hepatitis A virus (HAV) capsid protein VP1 generated in a heterologous expression system.

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