Titration of hepatitis B virus infectivity in the sera of pre‐acute and late acute phases of HBV infection: Transmission experiments to chimeric mice with human liver repopulated hepatocytes

The infectivity of hepadnavirus virions produced during either acute or chronic stages of infection was compared by testing the ability of the virions of woodchuck hepatitis virus (WHV) to induce productive acute infection in naive adult woodchucks. Serum WHV collected during acute infection was compared to virions harvested from WHV-infected woodchucks during either (i) early chronic infection, when WHV-induced hepatocellular carcinoma (HCC) was not yet developed, or (ii) late chronic infection, when established HCC was terminal. All tested types of WHV inoculum were related, because they were collected from woodchucks that originally were infected with standardized WHV7 inoculum. Despite the individual differences between animals, the kinetics of accumulation of serum relaxed circular DNA of WHV demonstrated that the virions produced during early or late chronic infection are fully capable of inducing productive acute infection with long-lasting high viremia. These findings were further supported by the analysis of such intrahepatic markers of WHV infection as replicative intermediate DNA, covalently closed circular DNA, pregenomic RNA, and the percentage of WHV core antigen-positive hepatocytes measured at several time points over the course of 17.5 weeks after the inoculation. In addition, the observed relationship between the production of antibodies against WHV surface antigens and parameters of WHV infection appears to be complex. Taken together, the generated data suggest that in vivo hepadnavirus virions produced during different phases of chronic infection did not demonstrate any considerable deficiencies in infectivity compared to that of virions generated during the acute phase of infection. IMPORTANCEThe generated data suggest that infectivity of virions produced during the early or late stages of chronic hepadnavirus infection is not compromised. Our novel results provided several lines of further evidence supporting the idea that during the state of chronic infection in vivo, the limitations of hepadnavirus cell-to-cell spread/superinfection (observed recently in the woodchuck model) are not due to the diminished infectivity of the virions circulating in the blood and likely are (i) related to the properties of hepatocytes (i.e., their capacity to support hepadnavirus infection/replication) and (ii) influenced by the immune system. The obtained results further extend the understanding of the mechanisms regulating the persistence of hepadnavirus infection. Follow-up studies that will further investigate hepadnavirus cell-to-cell spread as a potential regulator of the chronic state of the infection are warranted. Hepatitis B virus (HBV) is a very significant human pathogen that causes transient and chronic liver infections. Approximately 400 million individuals around the world are chronic carriers of HBV. Chronic HBV infection is the number one risk factor for development of hepatocellular carcinoma (HCC) (1-3). Woodchuck hepatitis virus (WHV) is another member of the Hepadnaviridae family,...

Section: Discussioncontrasting

confidence: 90%

Section: Discussioncontrasting

confidence: 89%

Section: Discussionmentioning

confidence: 94%

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Infection Patterns Induced in Naive Adult Woodchucks by Virions of Woodchuck Hepatitis Virus Collected during either the Acute or Chronic Phase of Infection

Freitas

Lukash

Rodrigues

et al. 2015

“…Similar observations of time-dependent virus infectivity have also been reported in hepatitis C virus (HCV) and hepatitis B virus (HBV) infections (1,16,18,20,45). The basis of the decline in infectivity for these viruses also still remains to be explained.…”

Section: Discussionsupporting

confidence: 60%

Viral Dynamics during Primary Simian Immunodeficiency Virus Infection: Effect of Time-Dependent Virus Infectivity

Vaidya

Ribeiro

Miller

et al. 2010

A recent experiment involving simian immunodeficiency virus (SIV) infection of macaques revealed that the infectivity of this virus decreased over the first few months of infection. Based on this observation, we introduce a viral dynamic model in which viral infectivity varies over time. The model is fit to viral load data from eight (donor) monkeys infected by intravaginal inoculation of SIVmac251, three monkeys infected by intravenous inoculation of virus isolated from the donors during the ramp-up phase of acute infection, and three monkeys infected by intravenous inoculation of virus isolated at the viral set-point. Although we only analyze data from 14 monkeys, the new model with time-dependent infectivity seems to fit the data significantly better than a widely used model with constant infectivity (P ‫؍‬ 2.44 ؋ 10 ؊11 ). Our results indicate that plasma virus infectivity on average decays ϳ8-fold (95% confidence interval [CI] ‫؍‬ 5.1 to 10.3) over the course of acute infection, with the decay occurring exponentially with an average rate of 0.28 day ؊1 (95% CI ‫؍‬ 0.14 to 0.42 day ؊1 ). The decay rate in set point plasma virus recipient animals is ϳ16 times slower than in ramp-up plasma virus recipient animals and ϳ6 times slower than in donor animals. Throughout acute infection up to the set-point, the infection rate is higher in ramp-up plasma virus recipient animals than in set-point plasma virus recipient animals. These results show that the infectivity depends upon the source of viral infection.During primary human immunodeficiency virus type 1 (HIV-1) infection, the number of virus particles in plasma increases rapidly, reaches a peak, and then declines until it reaches a set-point level (i.e., a quasi-steady state) (9, 43). During the first 1 to 3 weeks of a typical HIV infection the viral load remains below the limit of detection of conventional assays (12). This period, known as the eclipse phase, is followed by a 2-to 4-week ramp-up period, during which rapid (exponential) viral replication takes place, resulting in high plasma viral RNA levels and significant depletion of CCR5 ϩ CD4 ϩ T cells (12,24,31,47).A recent experiment indicates that the infectivity of SIV changes over time during primary infection (26). Ma et al. (26) infected macaques with SIV isolated either during ramp-up or at set-point. They found that early-stage plasma containing 20 SIV RNA copies could successfully infect animals, while with set-point plasma ϳ1,500 SIV RNA copies were needed to establish infection. As suggested by Ma et al. (26), the highly infectious virus during the early phase compared to the chronic phase could be due to (i) insufficient rounds of replication during the early phase to produce enough noninfectious viral genomes; (ii) coating of the set-point phase plasma virions with antibodies that interfere with infectivity; and/or (iii) efficient elimination during early-phase infection of less-infectious genomes. Preliminary data comparing the ratio of the 50% tissue culture infectious dose (TCID 50 ) wit...

“…In fact, as few as 20 HCV RNA copies in acute-stage serum can transmit HCV infection to a naïve chimpanzee, while HCV transmission with plasma collected after seroconversion requires 1,000-fold higher levels of HCV (18). Similar findings of very high infectivity of ramp-up-versus set-pointstage plasma have been established for HBV, both in chimpanzees and in chimeric mice with humanized livers (20,43); in the latter system, ramp-up-stage HBV serum is about 100 times more infectious than later-stage serum. As with SIV and HIV, the potential explanations for the relatively low infectivity of chronic-stage plasma in HCV infection include the presence of large numbers of defective virions or noninfectious antibody-virion immune complexes.…”

Section: Discussionmentioning

confidence: 61%

High Specific Infectivity of Plasma Virus from the Pre-Ramp-Up and Ramp-Up Stages of Acute Simian Immunodeficiency Virus Infection

Zhong

Stone

Piatak

et al. 2009

116

To define the ratio of simian immunodeficiency virus (SIV) RNA molecules to infectious virions in plasma, a ramp-up-stage plasma pool was made from the earliest viral RNA (vRNA)-positive plasma samples (collected approximately 7 days after inoculation) from seven macaques, and a set-point-stage plasma pool was made from plasma samples collected 10 to 16 weeks after peak viremia from seven macaques; vRNA levels in these plasma pools were determined, and serial 10-fold dilutions containing 1 to 1,500 vRNA copies/ml were made. Intravenous (i.v.) inoculation of a 1-ml aliquot of diluted ramp-up-stage plasma containing 20 vRNA copies infected 2 of 2 rhesus macaques, while for the set-point-stage plasma, i.v. inoculation with 1,500 vRNA copies was needed to transmit infection. Further, when the heat-inactivated set-point-stage plasma pool was mixed with ramp-up-stage virions, infection of inoculated macaques was blocked. Notably, 2 of 2 animals inoculated with 85 ml of a pre-ramp-up plasma pool containing <3 SIV RNA copies/ml developed SIV infections characterized by high levels of viral replication, demonstrating that "vRNA-negative" plasma collected from macaques in the pre-ramp-up stage is infectious. Furthermore, there is a high ratio of infectious virions to total virions in ramp-up-stage plasma (between 1:1 and 1:10) and a lower ratio in set-point-stage plasma (between 1:75 and 1:750). Heat-inactivated chronic-stage plasma can "neutralize" the highly infectious ramp-up-stage virions. These findings have implications for the understanding of the natural history of SIV and human immunodeficiency virus infection and transmission.