Frequent compartmentalization of hepatitis C virus variants in circulating B cells and monocytes

Abstract

Differences in the composition of the hepatitis C virus (HCV) quasispecies between plasma and blood mononuclear cells (BMC) strongly suggest that BMCs support viral replication. We examined the frequency of such compartmentalization, the cell types involved, the constraints exerted on the different variants, and the role of immunoglobulin-complexed variants. We screened the hypervariable region (HVR1) of HCV isolates from 14 HBsAg-and HIV-seronegative patients with chronic HCV infection. HCV RNA was amplified and cloned from plasma, the immunoglobulin G (IgG)-bound fraction, and total and sorted BMCs (CD19؉, CD8؉, CD4؉, and CD14؉ cells). Compartmentalization was estimated using a matrix correlation test. The ratio of nonsynonymous/synonymous substitutions (d N /d S ratio) was calculated for each compartment. HCV RNA was detected in 3/3 BMC, 11/11 CD19؉, 10/11 CD14؉, 4/11 CD8؉ and 0/11 CD4؉ cell samples. HVR1 sequences were significantly different between plasma and at least one cellular compartment in all nine cases analyzed, and between B cells (CD19؉) and monocytes ( H epatitis C virus (HCV) is an enveloped, positive-stranded RNA virus that circulates in vivo as a complex population of closely related variants referred to as a quasispecies. 1 Hepatitis C infection is frequently chronic, and its quasispecies nature probably plays a major role in viral persistence. 2,3 HCV genetic heterogeneity is particularly strong within a small hypervariable region (HVR1) that encodes a 27-amino acid peptide located at the N-terminus of the second envelope glycoprotein (E2) and is subjected to selective pressures by humoral and cellular immune responses. 4 One potential viral strategy explaining the persistence of HCV is infection of immune cells. Convincing evidence of HCV lymphotropism has been obtained in vitro in experiments showing that minor quasispecies components of strain H77 are selected in lymphoblastoid cell lines. 5 Subsequently, it was found that blood mononuclear cells (BMC) from chimpanzees that had been inoculated with this strain became infected by the same lymphotropic quasispecies components as those selected in vitro. 6 In vivo, HCV RNA has been detected in BMC by many teams. 7-14 Viral replication in these cells, shown by the detection of negatively stranded HCV RNA, an obligatory replication intermediate, generally occurs at a low level. 9,[15][16][17][18] Mutations in the 5Ј untranslated region-the viral internal ribosomal entry site-have been described in HCV strains isolated from BMCs. These mutations could influence the translational efficiency of the internal ribosomal entry site structure in lymphoblastoid cell lines 19 and point to HCV adaptation to BMCs. 6,20,21

Extrahepatic replication of HCV: Insights into clinical manifestations and biological consequences

“…20 Although there is limited data to suggest that HCV replication occurs in B lymphocytes, [21][22][23] chronic antigenic stimulation by the virus may trigger B cell proliferation resulting in a wide spectrum of pathology ranging from minor expansion of B cell populations to an aggressive high-grade lymphoma. A high prevalence of HCV in patients with B cell non-Hodgkin's lymphoma (NHL) has been reported in some, but not all studies.…”

Repression of Interferon Regulatory Factor 1 by Hepatitis C Virus Core Protein Results in Inhibition of Antiviral and Immunomodulatory Genes

“…The persistence of the virus in the majority of infected individuals is linked to the ability of HCV to evade and/or antagonize the host immune response at both the local and systemic levels. Accordingly, although hepatocytes are a major target of HCV infection, the virus can also replicate in immune cells, including effector cells (1,11). In this respect, resistance to interferon (IFN) therapy is a hallmark of evolution in persistence, indicating that knocking down the antiviral and immunomodulating effects of IFN is a successful strategy for evading the host immune surveillance (21).…”

HCV persistence: Cure is still a four letter word

“…It has been proposed that HCV compartmentalization may occur, in which HCV confined to a given "compartment" may not be capable of "infecting" other compartments. 23 Such a theory could explain the finding of HCV virions in PBMCs but not in liver in many of the patients studied.…”