Env-Specific Antibodies in Chronic Infection versus in Vaccination

To bnAb or Not to bnAb: Defining Broadly Neutralising Antibodies Against HIV-1

Since their discovery, antibodies capable of broad neutralisation have been at the forefront of HIV-1 research and are of particular interest due to in vivo passive transfer studies demonstrating their potential to provide protection. Currently an exact definition of what is required for a monoclonal antibody to be classed as a broadly neutralising antibody (bnAb) has not yet been established. This has led to hundreds of antibodies with varying neutralisation breadth being studied and has given insight into antibody maturation pathways and epitopes targeted. However, even with this knowledge, immunisation studies and vaccination trials to date have had limited success in eliciting antibodies with neutralisation breadth. For this reason there is a growing need to identify factors specifically associated with bnAb development, yet to do this a set of criteria is necessary to distinguish bnAbs from non-bnAbs. This review aims to define what it means to be a HIV-1 bnAb by comparing neutralisation breadth, genetic features and epitopes of bnAbs, and in the process highlights the challenges of comparing the array of antibodies that have been isolated over the years.

Intra-host evolutionary dynamics of the hepatitis C virus among people who inject drugs

Most individuals chronically infected with hepatitis C virus (HCV) are asymptomatic during the initial stages of infection and therefore the precise timing of infection is often unknown. Retrospective estimation of infection duration would improve existing surveillance data and help guide treatment. While intra-host viral diversity quantifications such as Shannon entropy have previously been utilized for estimating duration of infection, these studies characterize the viral population from only a relatively short segment of the HCV genome. In this study intra-host diversities were examined across the HCV genome in order to identify the region most reflective of time and the degree to which these estimates are influenced by high-risk activities including those associated with HCV acquisition. Shannon diversities were calculated for all regions of HCV from 78 longitudinally sampled individuals with known seroconversion timeframes. While the region of the HCV genome most accurately reflecting time resided within the NS3 gene, the gene region with the highest capacity to differentiate acute from chronic infections was identified within the NS5b region. Multivariate models predicting duration of infection from viral diversity significantly improved upon incorporation of variables associated with recent public, unsupervised drug use. These results could assist the development of strategic population treatment guidelines for high-risk individuals infected with HCV and offer insights into variables associated with a likelihood of transmission.

Induction of Identical IgG HIV-1 Envelope Epitope Recognition Patterns After Initial HIVIS-DNA/MVA-CMDR Immunization and a Late MVA-CMDR Boost

In the RV144 trial, to date the only HIV-1 vaccine efficacy trial demonstrating a modestly reduced risk of HIV-1 acquisition, antibody responses toward the HIV Envelope protein (Env) variable (V) 2 and V3 regions were shown to be correlated with a reduced risk of infection. These potentially protective antibody responses, in parallel with the vaccine efficacy, however, waned quickly. Dissecting vaccine-induced IgG recognition of antigenic regions and their variants within the HIV-1 Env from different vaccine trials will aid in designing future HIV-1 immunogens and vaccination schedules. We, therefore, analyzed the IgG response toward linear HIV-1 Env epitopes elicited by a multi-clade, multigene HIVIS-DNA priming, and heterologous recombinant modified vaccinia virus Ankara (MVA-CMDR) boosting regimen (HIVIS03) and assessed whether a late MVA-CMDR boost 3 years after completion of the initial vaccination schedule (HIVIS06) restored antibody responses toward these epitopes. Here we report that vaccination schedule in the HIVIS03 trial elicited IgG responses against linear epitopes within the V2 and V3 tip as well as against the gp41 immunodominant region in a high proportion of vaccinees. Antibodies against the V2 and gp41 Env regions were restricted to variants with close homology to the MVA-CMDR immunogen sequence, while V3 responses were more cross-reactive. Boosting with a late third MVA-CMDR after 3 years effectively restored waned IgG responses to linear Env epitopes and induced targeting of identical antigenic regions and variants comparable to the previous combined HIVIS-DNA/MVA-CMDR regimen. Our findings support the notion that anti-HIV-1 Env responses, associated with a reduced risk of infection in RV144, could be maintained by regular boosting with a single dose of MVA-CMDR.