Molecular Mimicry Between the Rabies Virus Glycoprotein and Human Immunodeficiency Virus-1 GP120: Cross-Reacting Antibodies Induced by Rabies Vaccination

Induction of Cross-Reacting Antibodies Against the COVID-19 by BCG Vaccination in the Mouse Model

It was reported that tuberculosis and BCG vaccination are potential tools for reducing the burden of COVID-19, mainly through the non-specific trained immunity. We have investigated whether BCG vaccination is able to induce cross-reacting antibodies against the SARS-CoV-2. We have tested the induced humoral immune responses against the SARS-CoV-2 Spike in the mouse model, after either BCG or rabies DNA-based vaccination alone or in Prime/Boost approach to COVID-19 DNA-based vaccination. We have demonstrated that BCG vaccination alone was able to induce cross-reacting antibodies to SARS-CoV-2 Spike. It can also boost the antibody response induced by a COVID-19 DNA-based vaccination. Hence, both BCG and latent tuberculosis infection can explain the lower burden of COVID-19 in developing countries, not only through the trained immunity but also by inducing cross-reacting antibodies. Furthermore, with the emergence of different COVID-19 variants, or eventually other Betacoronaviruses, the use of BCG vaccination can help against immune escapes of the current vaccines.

Superantigenic character of an insert unique to SARS-CoV-2 spike supported by skewed TCR repertoire in patients with hyperinflammation

Multisystem Inflammatory Syndrome in Children (MIS-C) associated with COVID-19 is a newly recognized condition in children with recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. These children and adult patients with severe hyperinflammation present with a constellation of symptoms that strongly resemble toxic shock syndrome, an escalation of the cytotoxic adaptive immune response triggered upon the binding of pathogenic superantigens to T cell receptors (TCRs) and/or major histocompatibility complex class II (MHCII) molecules. Here, using structure-based computational models, we demonstrate that the SARS-CoV-2 spike (S) glycoprotein exhibits a high-affinity motif for binding TCRs, and may form a ternary complex with MHCII. The binding epitope on S harbors a sequence motif unique to SARS-CoV-2 (not present in other SARS-related coronaviruses), which is highly similar in both sequence and structure to the bacterial superantigen staphylococcal enterotoxin B. This interaction between the virus and human T cells could be strengthened by a rare mutation (D839Y/N/E) from a European strain of SARS-CoV-2. Furthermore, the interfacial region includes selected residues from an intercellular adhesion molecule (ICAM)-like motif shared between the SARS viruses from the 2003 and 2019 pandemics. A neurotoxin-like sequence motif on the receptor-binding domain also exhibits a high tendency to bind TCRs. Analysis of the TCR repertoire in adult COVID-19 patients demonstrates that those with severe hyperinflammatory disease exhibit TCR skewing consistent with superantigen activation. These data suggest that SARS-CoV-2 S may act as a superantigen to trigger the development of MIS-C as well as cytokine storm in adult COVID-19 patients, with important implications for the development of therapeutic approaches.

The Cholinergic Anti-Inflammatory Response and the Role of Macrophages in HIV-Induced Inflammation

Macrophages are phagocytic immune cells that protect the body from foreign invaders and actively support the immune response by releasing anti- and proinflammatory cytokines. A seminal finding revolutionized the way macrophages are seen. The expression of the neuronal alpha7 nicotinic acetylcholine receptor (α7-nAChR) in macrophages led to the establishment of the cholinergic anti-inflammatory response (CAR) in which the activation of this receptor inactivates macrophage production of proinflammatory cytokines. This novel neuroimmune response soon began to emerge as a potential target to counteract inflammation during illness and infection states. Human immunodeficiency virus (HIV)-infected individuals suffer from chronic inflammation that persists even under antiretroviral therapy. Despite the CAR’s importance, few studies involving macrophages have been performed in the HIV field. Evidence demonstrates that monocyte-derived macrophages (MDMs) recovered from HIV-infected individuals are upregulated for α7-nAChR. Moreover, in vitro studies demonstrate that addition of an HIV viral constituent, gp120_IIIB, to uninfected MDMs also upregulates the α7-nAChR. Importantly, contrary to what was expected, activation of upregulated α7-nAChRs in macrophages does not reduce inflammation, suggesting a CAR disruption. Although it is reasonable to consider this receptor as a pharmacological target, additional studies are necessary since its activity seems to differ from that observed in neurons.

Natural Scrub Typhus Antibody Suppresses HIV CXCR4(X4) Viruses

Viral load generally rises in HIV-infected individuals with a concomitant infection, but falls markedly in some individuals with scrub typhus (ST), a common Asian rickettsial infection. ST infection appears to shift the viral population from CXCR4-using (X4) to CCR5-utilizing (R5) strains, and there is evidence of cross-reactivity between ST-specific antibodies and HIV-1. We examined the mechanism of ST suppression of HIV by measuring the effects of ST infection on X4 and R5 viruses in vivo and in vitro, and assessing the relative contributions of antibodies and chemokines to the inhibitory effect. In vivo, a single scrub typhus plasma infusion markedly reduced the subpopulation of HIV-1 viruses using the X4 co-receptor in all 8 recipients, and eliminated X4 viruses 6 patients. In vitro, the 14 ST sera tested all inhibited the replication of an X4 but not an R5 virus. This inhibitory effect was maintained if ST sera were depleted of chemokines but was lost upon removal of antibodies. Sera from STinfected mice recognized a target that co-localized with X4 HIV gp120 in immunofluorescent experiments. These in vivo and in vitro data suggest that acute ST infection generates cross-reactive antibodies that produce potent suppression of CXCR4- but not CCR5-using HIV-1 viruses. ST suppression of HIV replication could reveal novel mechanisms that could be exploited for vaccination strategies, as well as aid in the development of fusion inhibitors and other new therapeutic regimens. This also appears to be the first instance where one pathogen is neutralized by antibody produced in response to infection by a completely unrelated organism.

Restoration of the antibody response upon rabies vaccination in HIV-infected patients treated with HAART

DESIGN

Rabies vaccine was used as a T-cell-dependent neoantigen to investigate several aspects of the primary and booster immune response in vivo in HIV-infected individuals receiving antiretroviral treatment.

METHODS

Study participants received rabies vaccination twice, within a 3-month interval. Serum samples were taken before and 1, 2 and 4 weeks after both vaccinations and 1 and 5 years after the primary vaccination. Antirabies antibodies [immunoglobulin G (IgG), IgG subclasses, immunoglobulin A (IgA) and immunoglobulin M (IgM)] were determined; antibody avidity was measured after both vaccinations. T-cell subsets were characterized by flow cytometry.

RESULTS

Eighteen healthy controls and 30 HIV-infected adults, treated with HAART for almost 4 years, with a median CD4(+) T-cell count of 537 cells/microl, were immunized. The postvaccination concentrations of antirabies IgG and IgM were significantly lower in HIV-infected individuals as compared with controls. Three T-cell-dependent processes, a true booster response, a class switch from IgM to IgG and avidity maturation were present in both healthy controls and HIV-infected individuals. Higher age was associated with lower postvaccination antirabies IgG and IgM titers. Five years after the primary vaccination, 63% of the HIV-infected individuals still had antibody titers above the protection threshold.

CONCLUSION

Immune restoration in HIV-infected individuals treated with HAART, resulting in a CD4(+) T-cell count greater than 500 cells/microl, is incomplete. However, the majority of HIV-infected individuals are capable of mounting a long-lasting immune response, including several pivotal T-cell-dependent processes, upon vaccination with a neoantigen such as the rabies vaccine.

Nicotine prevents HIVgp120-caused electrophysiological and motor disturbances in rats

Human immunodeficiency virus (HIV)-associated dementia (HAD) is a frequent complication in HIV+ subjects. Several electrophysiological markers and motor control are altered in HIV+ subjects, including event-related potentials (N2-P3 changes). These are electrophysiological indicators of cognitive processing. The mechanisms by which HIV induces neurophysiological abnormality is still under research. However, several neurotransmitters have been implicated. For example, glutamate and the vasoactive intestinal neuropeptide (VIP). In this study, we support further this notion indicating that HIVgp120, a glycoprotein derived from HIV, is involved in the pathogenesis of neuropsychiatric abnormalities. We also have observations suggesting that one HIVgp120 mechanism of action is to interfere with cholinergic neurotransmission. Our results indicate that event-related potentials (ERP) were affected by HIVgp120, in particular N2 and P3. In addition, motor coordination was severely affected. Both parameters were maintained near normality when rats were simultaneously treated with nicotine. These results support further an HIVgp120-caused alteration of cholinergic neurotransmission that might be part of the etiology of neuropsychiatric disturbances.

Spying on HIV with SPR

The application of surface plasmon resonance (SPR)-based optical biosensors has contributed extensively to our understanding of functional aspects of HIV. SPR biosensors allow the analysis of real-time interactions of any biomolecule, be it protein, nucleic acid, lipid, carbohydrate or small molecule, without the need for intrinsic or extrinsic probes. As such, the technology has been used to analyze molecular interactions associated with every aspect of the viral life cycle, from basic studies of binding events occurring during docking, replication, budding and maturation to applied research related to vaccine and inhibitory drug development. Along the way, SPR biosensors have provided a unique and detailed view into the inner workings of HIV.

Mechanisms of HIV type 1-induced cognitive impairment: evidence for hippocampal cholinergic involvement with overstimulation of the VIPergic system by the viral coat protein core

HIV-1 is associated with a neuroAIDS syndrome that includes cognitive impairment. Several components of HIV-1 are capable of affecting cognition, but which of these is the major mediator is unknown. We injected into the lateral cerebral ventricle of mice HIV-1 pseudoviruses expressing the full viral genome with or without the viral coat glycoproteins, gp120/gp41. Only virus possessing gp120/gp41 induced defects in memory as assessed in an active avoidance T-maze footshock paradigm. By itself, gp120 also induced impairments that were reversed by hippocampal cholinergic stimulation. Paradoxically, low doses of gp120 could improve memory. Such low-dose, paradoxic improvement is a characteristic of substances that impair memory by overstimulating pathways that normally sustain memory. Consistent with this, a low, but not a high, dose of gp120 reversed memory impairment induced by overstimulation of the VIPergic system, a memory-sustaining pathway. Further characterization showed that two strains of gp120 (SF and MN) were equally effective at improving memory and that, unlike other actions of gp120, glycation was not required. We conclude that (1) the predominant cognitive-impairing component of HIV-1 is its viral coat glycoproteins, (2) gp120 impairs memory by overstimulating pathways that normally sustain memory, (3) the cognitive effect of gp120 is mediated by its protein core, and (4) gp120 likely impairs memory by affecting the cholinergic/VIPergic system.

An attempt to predict a possible existence of antiviral and antimicrobial activity

It is known that many pathogenic and toxic agents may attach to binding site of the same endogenic receptor. Such an effect is due to the resemblance between chemical structures in foreign agents. One may imagine the structure which contains binding-site fragments and may compete with the receptor for foreign agents. Then next suggestions are probable: (1)The same substance may interact with some agents with established resemblance; (2) If substance (1) interacts with agents A and B and substance (2) influences agent (2) only then (2) ought to act at agent B as well. In terms 'key-keyhole' this means an existence of the key fitting several keyholes. Application of this conception has given a possibility to predict an anti-HIV and antimicrobial activity of an antirabies immunoglobulin.

Mimicking the nicotinic receptor binding site by a single chain Fv selected by competitive panning from a synthetic phage library

We have developed a novel competitive method to select from a phage display library a single chain Fv which is able to mimic the alpha-bungarotoxin binding site of the muscle nicotinic receptor. The single chain Fv was selected from a large synthetic library using alpha-bungarotoxin-coated magnetic beads. Toxin-bound phages were then eluted by competition with affinity purified nicotinic receptor. Recognition of the toxin by the anti-alpha-bungarotoxin single chain Fv was very similar to that of the receptor, such as indicated by the epitope mapping of alpha-bungarotoxin through overlapping synthetic peptides. Moreover, several positively charged residues located in the toxin second loop and in the C-terminal region were found to be critical, to a similar extent, for toxin recognition by the single chain Fv and the receptor. However, although the anti-alpha-bungarotoxin single chain Fv seems to mimic the toxin binding site of the nicotinic receptor, it does not bind other nicotinic agonists or antagonists. Our results suggest that competitive selection of anti-ligand antibody phages can allow the production of receptor-mimicking molecules directly and exclusively targeted at one specific ligand. Since physiologically and pharmacologically different ligands can produce opposite effects on receptor functions, such selective ligand decoys can have important therapeutic applications.

Recombinant rabies virus as potential live-viral vaccines for HIV-1

Recombinant, replication-competent rabies virus (RV) vaccine strain-based vectors were developed expressing HIV type I (HIV-1) envelope glycoprotein (gp160) from both a laboratory-adapted (CXCR4-tropic) and a primary (dual-tropic) HIV-1 isolate. An additional transcription stop/start unit within the RV genome was used to express HIV-1 gp160 in addition to the other RV proteins. The HIV-1 gp160 protein was stably and functionally expressed, as indicated by fusion of human T cell lines after infection with the recombinant RVs. Inoculation of mice with the recombinant RVs expressing HIV-1 gp160 induced a strong humoral response directed against the HIV-1 envelope protein after a single boost with recombinant HIV-1 gp120 protein. Moreover, high neutralization titers up to 1:800 against HIV-1 could be detected in the mouse sera. These data indicate that a live recombinant RV, a rhabdovirus, expressing HIV-1 gp160 may serve as an effective vector for an HIV-1 vaccine.

Angiocentric CD3(+) T-cell infiltrates in human immunodeficiency virus type 1-associated central nervous system disease in children

A significant proportion of brain tissue specimens from children with AIDS show evidence of vascular inflammation in the form of transmural and/or perivascular mononuclear-cell infiltrates at autopsy. Previous studies have shown that in contrast to inflammatory lesions observed in human immunodeficiency virus type 1 (HIV-1) encephalitis, in which monocytes/macrophages are the prevailing mononuclear cells, these infiltrates consist mostly of lymphocytes. Perivascular mononuclear-cell infiltrates were found in brain tissue specimens collected at autopsy from five of six children with AIDS and consisted of CD3(+) T cells and equal or greater proportions of CD68(+) monocytes/macrophages. Transmural (including endothelial) mononuclear-cell infiltrates were evident in one patient and comprised predominantly CD3(+) T cells and small or, in certain vessels, approximately equal proportions of CD68(+) monocytes/macrophages. There was a clear preponderance of CD3(+) CD8(+) T cells on the endothelial side of transmural infiltrates. In active lesions of transmural vasculitis, CD3(+) T-cell infiltrates exhibited a distinctive zonal distribution. The majority of CD3(+) cells were also CD8(+) and CD45RO+. Scattered perivascular monocytes/macrophages in foci of florid vasculitis were immunoreactive for the p24 core protein. In contrast to the perivascular space, the intervening brain neuropil was dominated by monocytes/macrophages, microglia, and reactive astrocytes, containing only scant CD3(+) CD8(+) cells. Five of six patients showed evidence of calcific vasculopathy, but only two exhibited HIV-1 encephalitis. One patient had multiple subacute cerebral and brainstem infarcts associated with a widespread, fulminant mononuclear-cell vasculitis. A second patient had an old brain infarct associated with fibrointimal thickening of large leptomeningeal vessels. These infiltrating CD3(+) T cells may be responsible for HIV-1-associated CNS vasculitis and vasculopathy and for endothelial-cell injury and the opening of the blood-brain barrier in children with AIDS.