Human Cathelicidin Compensates for the Role of Apolipoproteins in Hepatitis C Virus Infectious Particle Formation

Abstract

Exchangeable apolipoproteins (ApoA, -C, and -E) have been shown to redundantly participate in the formation of infectious hepatitis C virus (HCV) particles during the assembly process, although their precise role in the viral life cycle is not well understood. Recently, it was shown that the exogenous expression of only short sequences containing amphipathic ␣-helices from various apolipoproteins is sufficient to restore the formation of infectious HCV particles in ApoB and ApoE double-gene-knockout Huh7 (BE-KO) cells. In this study, through the expression of a small library of human secretory proteins containing amphipathic ␣-helix structures, we identified the human cathelicidin antimicrobial peptide (CAMP), the only known member of the cathelicidin family of antimicrobial peptides (AMPs) in humans and expressed mainly in bone marrow and leukocytes. We showed that CAMP is able to rescue HCV infectious particle formation in BE-KO cells. In addition, we revealed that the LL-37 domain in CAMP containing amphipathic ␣-helices is crucial for the compensation of infectivity in BE-KO cells, and the expression of CAMP in nonhepatic 293T cells expressing claudin 1 and microRNA miR-122 confers complete propagation of HCV. These results suggest the possibility of extrahepatic propagation of HCV in cells with low-level or no expression of apolipoproteins but expressing secretory proteins containing amphipathic ␣-helices such as CAMP. IMPORTANCEVarious exchangeable apolipoproteins play a pivotal role in the formation of infectious HCV during the assembly of viral particles, and amphipathic ␣-helix motifs in the apolipoproteins have been shown to be a key factor. To the best of our knowledge, we have identified for the first time the human cathelicidin CAMP as a cellular protein that can compensate for the role of apolipoproteins in the life cycle of HCV. We have also identified the domain in CAMP that contains amphipathic ␣-helices crucial for compensation and show that the expression of CAMP in nonhepatic cells expressing claudin 1 and miR-122 confers complete propagation of HCV. We speculate that low levels of HCV propagation might be possible in extrahepatic tissues expressing secretory proteins containing amphipathic ␣-helices without the expression of apolipoproteins. According to recent estimates, more than 160 million people worldwide are chronically infected with hepatitis C virus (HCV) (1), which causes liver-related pathologies that can result in life-threatening diseases such as cirrhosis and hepatocellular carcinoma (2). Chronic HCV infection is also associated with several extrahepatic manifestations, including immunological disorders such as cryoglobulinemia and B-cell non-Hodgkin lymphoma (3). A vaccine is not yet available, but recent advances in antiviral treatment, improving upon what was for many years the standard therapy of pegylated interferon alpha plus ribavirin, now include several direct-acting antivirals (DAAs) that have increased the rate of sustained virological response (SVR) up to 80 ...

Hepatitis C Virus (HCV)–Apolipoprotein Interactions and Immune Evasion and Their Impact on HCV Vaccine Design

“…Accordingly, two research groups highlighted the role of α-helical structures in HCV morphogenesis. The authors demonstrated that expression of short sequences containing amphipathic α-helices derived from apolipoproteins but also of other proteins such as the human cathelicidin antimicrobial peptide is sufficient to rescue the production of infectious HCV particles in apolipoprotein knockout cells ( 49 – 51 ). Of note, a recently published paper showed that α-helices found in host-derived apolipoproteins and in NS1 of other Flaviviridae may have overlapping roles in the formation of infectious flaviviral particles ( 52 ).…”

Roles of secretory glycoproteins in particle formation of Flaviviridae viruses

“…Patients with chronic hepatitis C often develop extrahepatic manifestations, and thus it may be feasible that the secretion of host proteins possessing amphipathic α‐helices could compensate for the role of exchangeable apolipoproteins in the production of infectious HCV particles. In another previous study, we showed that human cathelicidin hCAP18/LL‐37 (cathelicidin antimicrobial peptide [CAMP]), the only known member of the cathelicidin family of antimicrobial peptides (AMPs), plays a comparable role in the formation of infectious HCV particles with exchangeable apolipoproteins . Furthermore, it is possible that other host factors are involved in the formation of infectious HCV particles via a similar mechanism.…”

“…In another previous study, we showed that human cathelicidin hCAP18/LL-37 (cathelicidin antimicrobial peptide [CAMP]), the only known member of the cathelicidin family of antimicrobial peptides (AMPs), plays a comparable role in the formation of infectious HCV particles with exchangeable apolipoproteins. 32 Furthermore, it is possible that other host factors are involved in the formation of infectious HCV particles via a similar mechanism.…”

Hepatitis C virus–apolipoprotein interactions: molecular mechanisms and clinical impact

“…Finally, a study performed by the group Matsuuraa supported the importance of α-helix domains for HCV particle assembly. Indeed, they demonstrated that the human cathelicidin antimicrobial peptide (CAMP), a protein containing amphipathic α-helices, is able to rescue HCV infectious particle formation, raising the possibility of extra-hepatic propagation of HCV in cells with low-level or no expression of apolipoproteins [105]. To summarize, exchangeable apolipoproteins possess redundant roles in the assembly of HCV through the interaction of the amphipathic α-helices with viral particles.…”