On the benefits of sin

Antigenic cooperation in viral populations: Transformation of functions of intra-host viral variants

In this paper, we study intra-host viral adaptation by antigenic cooperation - a mechanism of immune escape that serves as an alternative to the standard mechanism of escape by continuous genomic diversification and allows to explain a number of experimental observations associated with the establishment of chronic infections by highly mutable viruses. Within this mechanism, the topology of a cross-immunoreactivity network forces intra-host viral variants to specialize for complementary roles and adapt to the host's immune response as a quasi-social ecosystem. Here we study dynamical changes in immune adaptation caused by evolutionary and epidemiological events. First, we show that the emergence of a viral variant with altered antigenic features may result in a rapid re-arrangement of the viral ecosystem and a change in the roles played by existing viral variants. In particular, it may push the population under immune escape by genomic diversification towards the stable state of adaptation by antigenic cooperation. Next, we study the effect of a viral transmission between two chronically infected hosts, which results in the merging of two intra-host viral populations in the state of stable immune-adapted equilibrium. In this case, we also describe how the newly formed viral population adapts to the host's environment by changing the functions of its members. The results are obtained analytically for minimal cross-immunoreactivity networks and numerically for larger populations.

What Can We Learn from Research with Monoclonal Antibody 1F7?

1F7 is a monoclonal antibody that recognizes an idiotypic determinant expressed on primate antibodies binding to HIV-1 and hepatitis C proteins. This monoclonal antibody was used as a tool to dissect the immune response in humans infected with HIV-1 and hepatitis B. Furthermore, 1F7 was also used to manipulate the immune response against HIV-1 in macaques. The generation of a monoclonal antibody describing a network suggests similar antibodies could be developed as tools to dissect entangled networks in autoimmune diseases and allergic reactions. This review discusses the body of work done with 1F7 in the light of contemporary immunology.

Antiviral potential of plant polysaccharide nanoparticles actuating non-specific immunity

The development of high-end targeted drugs and vaccines against modern pandemic infections, such as COVID-19, can take a too long time that lets the epidemic spin up and harms society. However, the countermeasures must be applied against the infection in this period until the targeted drugs became available. In this regard, the non-specific, broad-spectrum anti-viral means could be considered as a compromise allowing overcoming the period of trial. One way to enhance the ability to resist the infection is to activate the nonspecific immunity using a suitable driving-up agent, such as plant polysaccharides, particularly our drug Panavir isolated from the potato shoots. Earlier, we have shown the noticeable anti-viral and anti-bacterial activity of Panavir. Here we demonstrate the pro-inflammation activity of Panavir, which four-to-eight times intensified the ATP and MIF secretion by HL-60 cells. This effect was mediated by the active phagocytosis of the Panavir particles by the cells. We hypothesized the physiological basis of the Panavir proinflammatory activity is mediated by the indol-containing compounds (auxins) present in Panavir and acting as a plant analog of serotonin.

Anti-Idiotypic Agonistic Antibodies: Candidates for the Role of Universal Remedy

Anti-idiotypic antibodies (anti-IDs) were discovered at the very beginning of the 20th century and have attracted attention of researchers for many years. Nowadays, there are five known types of anti-IDs: α, β, γ, ε, and δ. Due to the ability of internal-image anti-IDs to compete with an antigen for binding to antibody and to alter the biologic activity of an antigen, anti-IDs have become a target in the search for new treatments of autoimmune illnesses, cancer, and some other diseases. In this review, we summarize the data about anti-IDs that mimic the structural and functional properties of some bioregulators (autacoids, neurotransmitters, hormones, xenobiotics, and drugs) and evaluate their possible medical applications. The immune system is potentially able to reproduce or at least alter the effects of any biologically active endogenous or exogenous immunogenic agent via the anti-idiotypic principle, and probably regulates a broad spectrum of cell functions in the body, being a kind of universal remedy or immunacea, by analogy to the legendary ancient goddess of universal healing Panacea (Πανάκεια, Panakeia in Greek) in the treatment and prevention of diseases, possibly including non-infectious somatic and even hereditary ones.

Local immunodeficiency: Minimal networks and stability

Some basic aspects of the recently discovered phenomenon of local immunodeficiency (Skums et al. [1]) generated by antigenic cooperation in cross-immunoreactivity (CR) networks are investigated. We prove that local immunodeficiency (LI) that is stable under perturbations already occurs in very small networks and under general conditions on their parameters. Therefore our results are applicable not only to Hepatitis C where CR networks are known to be large (Skums et al. [1]), but also to other diseases with CR. A major necessary feature of such networks is the non-homogeneity of their topology. It is also shown that one can construct larger CR networks with stable LI by using small networks with stable LI as their building blocks. Our results imply that stable LI occurs in networks with quite general topology. In particular, the scale-free property of a CR network, assumed in Skums et al. [1], is not required.

Combined Action of Anti-CD4 Autoantibodies and Rheumatoid Factor in the Development of CD4 Lymphocytopenia in Rats Immunized with HIV-1 gp120

The development of immunodeficiency in HIV-infected patients is known to result from CD4⁺ lymphocyte depletion. Most CD4⁺ lymphocyte cells destined to die are not infected. The mechanism of HIV-uninfected cell death has not yet been fully elucidated. The aim of this study is to examine the role of anti-CD4 autoantibodies and physiological rheumatoid factor (RF) in the development of CD4⁺ lymphocytopenia. Immunization of Wistar rats with gp120 HIV-1 induces chronic production of anti-CD4 autoantibodies and decreases CD4⁺ lymphocytes in the blood. However, the anti-CD4 autoantibodies produced as part of the immune response to gp120 do not kill CD4⁺ cells directly. In rats producing anti-CD4 autoantibodies, a low level of peripheral CD4 lymphocytes is associated with high blood RF levels. The sera containing RF killed lymphocytes when the lymphocytes were pretreated with sera containing anti-CD4 autoantibodies. Thus, the death of CD4⁺ lymphocytes in rats immunized with gp120 is a result of the combined action of anti-CD4 autoantibodies and RF, and the action of these factors can be separated in time. The fact that two signals are needed for CD4⁺ lymphocyte death in HIV gp120-immunized rats does not contradict the hypothesis of the activation-induced death of uninfected CD4⁺ cells in HIV-infected humans.

The Homophilic Domain - An Immunological Archetype

The homophilic potential emerges as an important biological principle to boost the potency of immunoglobulins. Since homophilic antibodies in human and mouse sera exist prior environmental exposure, they are part of the natural antibody repertoire. Nevertheless, hemophilic properties are also identified in induced antibody repertoire. The use of homophilicity of antibodies in the adaptive immunity signifies an archetypic antibody structure. The unique feature of homophilicity in the antibody repertoire also highlights an important mechanism to boost the antibody potency to protect against infection and atherosclerosis as well to treat cancer patients.

The Neutralizing Antibody Response in an Individual with Triple HIV-1 Infection Remains Directed at the First Infecting Subtype

The effect of serial HIV-1 infection on the development of the broadly neutralizing antibody (bNAb) response was studied in an individual, H01-10366, with a serial HIV-1 superinfection (SI), hence triple infection, and compared with the bNAb response in three superinfected as well as 11 monoinfected men who have had sex with men (MSM) from Amsterdam, the Netherlands. Neutralization assays measuring heterologous neutralizing antibody (NAb) titers on a panel of six representative viruses from different HIV-1 subtypes were performed on blood serum samples obtained ∼3 years after primary HIV infection (PHI) and longitudinally for H01-10366. A bNAb response was defined as having a geometric mean neutralization titer (the reciprocal serum dilution giving 50% inhibition of virus infection, inhibitory dilution (ID₅₀)) ≥100 and neutralizing >50% of viruses in the panel with an ID₅₀ titer ≥100. H01-10366 quickly developed a potent NAb response against subtype B viruses before subtype B SI, but no broadening of the response occurred after the second subtype B infection or the third infection with CRF01_AE. When comparing H01-10366 with matched monoinfected (N = 11) and superinfected (N = 3) individuals analyzed 3 years after PHI, we found that 5 of the 15 individuals (4/11 monoinfected, 1/4 SI) developed a bNAb response. However, there was no statistically discernible difference between the bNAb response and HIV-1 SI. Thus, HIV-1 SI was not associated with the breadth and potency of the bNAb response in this small group of Dutch MSM with SI that included a triple HIV-1-infected individual.

The Significance of a Common Idiotype (1F7) on Antibodies against Human Immune Deficiency Virus Type 1 and Hepatitis C Virus

In this review, we trace the concept and potential functional role of regulatory idiotypes in the immune response to human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus, and hepatitis C virus (HCV). A major idiotype involved in these viral infections is recognized and defined by a murine monoclonal antibody (1F7). Antibodies expressing the idiotype defined by 1F7 are dominant in HIV-1 infection and are also found on many broadly neutralizing antibodies against HIV-1. This regulatory idiotypic axis offers opportunities for exploitation in vaccine development for HIV-1, HCV, and other chronic viral infections.

Network Analysis of the Chronic Hepatitis C Virome Defines Hypervariable Region 1 Evolutionary Phenotypes in the Context of Humoral Immune Responses

Hypervariable region 1 (HVR1) of hepatitis C virus (HCV) comprises the first 27 N-terminal amino acid residues of E2. It is classically seen as the most heterogeneous region of the HCV genome. In this study, we assessed HVR1 evolution by using ultradeep pyrosequencing for a cohort of treatment-naive, chronically infected patients over a short, 16-week period. Organization of the sequence set into connected components that represented single nucleotide substitution events revealed a network dominated by highly connected, centrally positioned master sequences. HVR1 phenotypes were observed to be under strong purifying (stationary) and strong positive (antigenic drift) selection pressures, which were coincident with advancing patient age and cirrhosis of the liver. It followed that stationary viromes were dominated by a single HVR1 variant surrounded by minor variants comprised from conservative single amino acid substitution events. We present evidence to suggest that neutralization antibody efficacy was diminished for stationary-virome HVR1 variants. Our results identify the HVR1 network structure during chronic infection as the preferential dominance of a single variant within a narrow sequence space.

IMPORTANCE

HCV infection is often asymptomatic, and chronic infection is generally well established in advance of initial diagnosis and subsequent treatment. HVR1 can undergo rapid sequence evolution during acute infection, and the variant pool is typically seen to diverge away from ancestral sequences as infection progresses from the acute to the chronic phase. In this report, we describe HVR1 viromes in chronically infected patients that are defined by a dominant epitope located centrally within a narrow variant pool. Our findings suggest that weakened humoral immune activity, as a consequence of persistent chronic infection, allows for the acquisition and maintenance of host-specific adaptive mutations at HVR1 that reflect virus fitness.

Novel vaccine concept based on back-boost effect in viral infection

A novel vaccine concept is discussed based on recent evidence of a "back-boost" effect in Influenza infection. The initial immune response to the infection is imprinted through an immune memory pathway. The immune memory in the back-boost mechanism could be used in reversed order as a "forward-boost" in the proposed vaccine concept.

Antigenic cooperation among intrahost HCV variants organized into a complex network of cross-immunoreactivity

Hepatitis C virus (HCV) has the propensity to cause chronic infection. Continuous immune escape has been proposed as a mechanism of intrahost viral evolution contributing to HCV persistence. Although the pronounced genetic diversity of intrahost HCV populations supports this hypothesis, recent observations of long-term persistence of individual HCV variants, negative selection increase, and complex dynamics of viral subpopulations during infection as well as broad cross-immunoreactivity (CR) among variants are inconsistent with the immune-escape hypothesis. Here, we present a mathematical model of intrahost viral population dynamics under the condition of a complex CR network (CRN) of viral variants and examine the contribution of CR to establishing persistent HCV infection. The model suggests a mechanism of viral adaptation by antigenic cooperation (AC), with immune responses against one variant protecting other variants. AC reduces the capacity of the host's immune system to neutralize certain viral variants. CRN structure determines specific roles for each viral variant in host adaptation, with variants eliciting broad-CR antibodies facilitating persistence of other variants immunoreacting with these antibodies. The proposed mechanism is supported by empirical observations of intrahost HCV evolution. Interference with AC is a potential strategy for interruption and prevention of chronic HCV infection.

Obstacles to ideal anti-HIV antibody-dependent cellular cytotoxicity responses

A safe and effective vaccine against HIV is a global health priority. Large-scale phase III clinical vaccine trials based on neutralizing antibodies and cytotoxic T-lymphocytes have failed to provide protection, highlighting the lack of understanding of basic immune correlates of protection against HIV. The partial success of the RV144 vaccine trial, however, sparked an intense research effort to identify and describe the protective potential of non-neutralizing antibodies. Correlates of protection analyses have identified antibodies that induced antibody-dependent cellular cytotoxicity (ADCC) as potentially important. Despite the attractiveness of utilizing ADCC antibodies for HIV vaccine design, it is important to note that effective ADCC responses are contingent on many factors. As discussed in this review, these factors are important considerations for determining the feasibility of designing an optimal ADCC antibody-inducing vaccine construct. Important determinants of ADCC responses include characteristics of the antibody, such as isotype and subclass, antigen-specificity, titer, durability and glycosylation of the constant region. Second, ADCC immune responses are highly contingent on the natural killer (NK) cell effectors. This review will describe the current state of knowledge regarding the ontogeny of NK cells, highlighting the continuous "education" they undergo that determines their functional potential upon stimulation. Other important NK cell factors, such as constant region receptor polymorphisms, cellular exhaustion, and the effects of the cytokine milieu on cellular function, will also be covered. Finally, an exciting, but yet untested, role for NK cell-mediated ADCC lies in its potential ability to eliminate latently infected cells, which harbor the viral reservoir. The review will address the potential of a two-pronged attack, where latently infected cells are induced to express HIV antigens and then eliminated by NK cells via an ADCC mechanism, with the goal of inducing a cure.