Key mutations in the C-terminus of the HBV surface glycoprotein correlate with lower HBsAg levels <i>in vivo</i>, hinder HBsAg secretion <i>in vitro</i> and reduce HBsAg structural stability in the setting of HBeAg-negative chronic HBV genotype-D infection
Creators: name: Salpini, Romina
name: Battisti, Arianna
name: Piermatteo, Lorenzo
name: Carioti, Luca
name: Anastasiou, Olympia E.
name: Upkar S. Gill
name: Carlo, Domenico Di
name: Colagrossi, Luna
name: Duca, Leonardo
name: Bertoli, Ada
name: Rosa, Katia Yu La
name: Fabeni, Lavinia
name: Iuvara, Alessandra
name: Malagnino, Vincenzo
name: Cerva, Carlotta
name: Lichtner, Miriam
name: Mastroianni, Claudio M.
name: Sanctis, Giuseppe Maria De
name: Paoloni, Maurizio
name: Marignani, Massimo
name: Pasquazzi, Caterina
name: Iapadre, Nerio
name: Parruti, Giustino
name: Vecchiet, Jacopo
name: Sarmati, Loredana
name: Andreoni, Massimo
name: Angelico, Mario
name: Grelli, Sandro
name: Kennedy, Patrick
name: Verheyen, Jens
name: Aquaro, Stefano
name: Silberstein, Francesca Ceccherini
name: Perno, Carlo Federico
name: Svicher, Valentina
Publisher: name: Taylor & Francis
Year: 2020
Subjects: subject: Biochemistry
subject: Medicine
subject: Microbiology
subject: FOS: Biological sciences
subject: FOS: Biological sciences
subject: Molecular Biology
subject: 39999 Chemical Sciences not elsewhere classified
subject: FOS: Chemical sciences
subject: FOS: Chemical sciences
subject: Immunology
subject: FOS: Clinical medicine
subject: FOS: Clinical medicine
subject: 111714 Mental Health
subject: FOS: Health sciences
subject: FOS: Health sciences
subject: 110309 Infectious Diseases
subject: 60506 Virology
subject: Computational Biology

description: Increasing evidences suggest that HBsAg-production varies across HBV-genotypes. HBsAg C-terminus plays a crucial role for HBsAg-secretion. Here, we evaluate HBsAg-levels in different HBV-genotypes in HBeAg-negative chronic infection, the correlation of specific mutations in HBsAg C-terminus with HBsAg-levels <i>in-vivo,</i> their impact on HBsAg-secretion <i>in-vitro</i> and on structural stability <i>in-silico</i>. HBsAg-levels were investigated in 323 drug-naïve HBeAg-negative patients chronically infected with HBV genotype-D(N=228), -A(N=65) and -E(N=30). Genotype-D was characterized by HBsAg-levels lower than genotype-A and -E (3.3[2.7-3.8]IU/ml; 3.8[3.5-4.2]IU/ml and 3.9[3.7-4.2]IU/ml, P&lt;0.001). Results confirmed by multivariable analysis correcting for patients’demographics, HBV-DNA, ALT and infection-status. In genotype-D, specific C-terminus mutations (V190A-S204N-Y206C-Y206F-S210N) significantly correlate with HBsAg&lt;1,000IU/ml(P-value from &lt;0.001 to 0.04). These mutations lie in divergent pathways involving other HBsAg C-terminus mutations: V190A + F220L (Phi=0.41, P=0.003), S204N + L205P (Phi=0.36, P=0.005), Y206F + S210R (Phi=0.47, P&lt;0.001) and S210N + F220L (Phi=0.40, P=0.006). Notably, patients with these mutational pairs present HBsAg-levels 1log lower than patients without them(P-value from 0.003 to 0.02). <i>In-vitro</i>, the above-mentioned mutational pairs determined a significant decrease in HBsAg secretion-efficiency compared to wt(P-value from &lt;0.001 to 0.02). Structurally, these mutational pairs reduced HBsAg C-terminus stability and determined a rearrangement of this domain. In conclusion, HBsAg-levels in genotype-D are significantly lower than in genotype-A and -E in HBeAg-negative patients. In genotype-D, specific mutational clusters in HBsAg C-terminus correlate with lower HBsAg-levels <i>in-vivo</i>, hamper HBsAg-release <i>in-vitro</i> and affect its structural stability, supporting their detrimental role on HBsAg-secretion. In this light, genotypic-testing can be a valuable tool to optimize the clinical interpretation of HBsAg in genotype-D and to provide information on HBV-pathogenicity and disease-progression.