Cell-to-Cell Spread Blocking Activity Is Extremely Limited in the Sera of Herpes Simplex Virus 1 (HSV-1)- and HSV-2-Infected Subjects

Effector functions are required for broad and potent protection of neonatal mice with antibodies targeting HSV glycoprotein D

Multiple failed herpes simplex virus (HSV) vaccine candidates induce robust neutralizing antibody (Ab) responses in clinical trials, raising the hypothesis that Fc-domain-dependent effector functions may be critical for protection. While neonatal HSV (nHSV) infection results in mortality and lifelong neurological morbidity in humans, it is uncommon among neonates with a seropositive birthing parent, supporting the hypothesis that Ab-based therapeutics could protect neonates from HSV. We therefore investigated the mechanisms of monoclonal Ab (mAb)-mediated protection in a mouse model of nHSV infection. For a panel of glycoprotein D (gD)-specific mAbs, neutralization and effector functions contributed to nHSV-1 protection. In contrast, effector functions alone were sufficient to protect against nHSV-2, exposing a functional dichotomy between virus types consistent with vaccine trial results. Effector functions are therefore crucial for protection by these gD-specific mAbs, informing effective Ab and vaccine design and demonstrating the potential of polyfunctional Abs as therapeutics for nHSV infections.

An Adagio for Viruses, Played Out on Ancient DNA

Studies of ancient DNA have transformed our understanding of human evolution. Paleogenomics can also reveal historic and prehistoric agents of disease, including endemic, epidemic, and pandemic pathogens. Viruses-and in particular those with single- or double-stranded DNA genomes-are an important part of the paleogenomic revolution, preserving within some remains or environmental samples for tens of thousands of years. The results of these studies capture the public imagination, as well as giving scientists a unique perspective on some of the more slowly evolving viruses which cause disease. In this review, we revisit the first studies of historical virus genetic material in the 1990s, through to the genomic revolution of recent years. We look at how paleogenomics works for viral pathogens, such as the need for careful precautions against modern contamination and robust computational pipelines to identify and analyze authenticated viral sequences. We discuss the insights into virus evolution which have been gained through paleogenomics, concentrating on three DNA viruses in particular: parvovirus B19, herpes simplex virus 1, and smallpox. As we consider recent worldwide transmission of monkeypox and synthetic biology tools that allow the potential reconstruction of extinct viruses, we show that studying historical and ancient virus evolution has never been more topical.

Ancient herpes simplex 1 genomes reveal recent viral structure in Eurasia

Human herpes simplex virus 1 (HSV-1), a life-long infection spread by oral contact, infects a majority of adults globally. Phylogeographic clustering of sampled diversity into European, pan-Eurasian, and African groups has suggested the virus codiverged with human migrations out of Africa, although a much younger origin has also been proposed. We present three full ancient European HSV-1 genomes and one partial genome, dating from the 3rd to 17th century CE, sequenced to up to 9.5× with paired human genomes up to 10.16×. Considering a dataset of modern and ancient genomes, we apply phylogenetic methods to estimate the age of sampled modern Eurasian HSV-1 diversity to 4.68 (3.87 to 5.65) ka. Extrapolation of estimated rates to a global dataset points to the age of extant sampled HSV-1 as 5.29 (4.60 to 6.12) ka, suggesting HSV-1 lineage replacement coinciding with the late Neolithic period and following Bronze Age migrations.

Antiviral CD19+CD27+ Memory B Cells Are Associated with Protection from Recurrent Asymptomatic Ocular Herpesvirus Infection

Reactivation of herpes simplex virus 1 (HSV-1) from latently infected neurons of the trigeminal ganglia (TG) leads to blinding recurrent herpetic disease in symptomatic (SYMP) individuals. Although the role of T cells in herpes immunity seen in asymptomatic (ASYMP) individuals is heavily explored, the role of B cells is less investigated. In the present study, we evaluated whether B cells are associated with protective immunity against recurrent ocular herpes. The frequencies of circulating HSV-specific memory B cells and of memory follicular helper T cells (CD4⁺ T_fh cells), which help B cells produce antibodies, were compared between HSV-1-infected SYMP and ASYMP individuals. The levels of IgG/IgA and neutralizing antibodies were compared in SYMP and ASYMP individuals. We found that (i) the ASYMP individuals had increased frequencies of HSV-specific CD19⁺CD27⁺ memory B cells, and (ii) high frequencies of HSV-specific switched IgG⁺CD19⁺CD27⁺ memory B cells detected in ASYMP individuals were directly proportional to high frequencies of CD45R0⁺CXCR5⁺CD4⁺ memory T_fh cells. However, no differences were detected in the level of HSV-specific IgG/IgA antibodies in SYMP and ASYMP individuals. Using the UV-B-induced HSV-1 reactivation mouse model, we found increased frequencies of HSV-specific antibody-secreting plasma HSV-1 gD⁺CD138⁺ B cells within the TG and circulation of ASYMP mice compared to those of SYMP mice. In contrast, no significant differences in the frequencies of B cells were found in the cornea, spleen, and bone-marrow. Our findings suggest that circulating antibody-producing HSV-specific memory B cells recruited locally to the TG may contribute to protection from symptomatic recurrent ocular herpes. IMPORTANCE Reactivation of herpes simplex virus 1 (HSV-1) from latently infected neurons of the trigeminal ganglia (TG) leads to blinding recurrent herpetic disease in symptomatic (SYMP) individuals. Although the role of T cells in herpes immunity against blinding recurrent herpetic disease is heavily explored, the role of B cells is less investigated. In the present study, we found that in both asymptomatic (ASYMP) individuals and ASYMP mice, there were increased frequencies of HSV-specific memory B cells that were directly proportional to high frequencies of memory T_fh cells. Moreover, following UV-B-induced reactivation, we found increased frequencies of HSV-specific antibody-secreting plasma B cells within the TG and circulation of ASYMP mice compared to those of SYMP mice. Our findings suggest that circulating antibody-producing HSV-specific memory B cells recruited locally to the TG may contribute to protection from recurrent ocular herpes.

Extracellular vesicles originating from autophagy mediate an antibody-resistant spread of classical swine fever virus in cell culture

Free spread is a classical mode for mammalian virus transmission. However, the efficiency of this transmission approach is generally low as there are structural barriers or immunological surveillances in the extracellular environment under physiological conditions. In this study, we systematically analyzed the spreading of classical swine fever virus (CSFV) using multiple viral replication analysis in combination with antibody neutralization, transwell assay, and electron microscopy, and identified an extracellular vesicle (EV)-mediated spreading of CSFV in cell cultures. In this approach, intact CSFV virions are enclosed within EVs and transferred into uninfected cells with the movement of EVs, leading to an antibody-resistant infection of the virus. Using fractionation assays, immunostaining, and electron microscopy, we characterized the CSFV-containing EVs and demonstrated that the EVs originated from macroautophagy/autophagy. Taken together, our results showed a new spreading mechanism for CSFV and demonstrated that the EVs in CSFV spreading are closely related to autophagy. These findings shed light on the immune evasion mechanisms of CSFV transmission, as well as new functions of cellular vesicles in virus lifecycles.Abbreviations: 3-MA: 3-methyladenine; CCK-8: Cell Counting Kit-8; CSF: classical swine fever; CQ: chloroquine; CSFV: classical swine fever virus; DAPI, 4-,6-diamidino-2-phenylindole; EVs: extracellular vesicles; hpi: h post infection; IEM: immunoelectron microscopy; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MOI: multiplicity of infection; MVs: microvesicles; ND50: half neutralizing dose; PCR: polymerase chain reaction; PBS: phosphate-buffered saline; SEC: size-exclusion chromatography; siRNA: small interfering RNA; TEM: transmission electron microscopy.

Peripheral B Cell Deficiency and Predisposition to Viral Infections: The Paradigm of Immune Deficiencies

In the era of COVID-19, understanding how our immune system responds to viral infections is more pertinent than ever. Immunodeficiencies with very low or absent B cells offer a valuable model to study the role of humoral immunity against these types of infection. This review looks at the available evidence on viral infections in patients with B cell alymphocytosis, in particular those with X-linked agammaglobulinemia (XLA), Good’s syndrome, post monoclonal-antibody therapy and certain patients with Common Variable Immune Deficiency (CVID). Viral infections are not as infrequent as previously thought in these conditions and individuals with very low circulating B cells seem to be predisposed to an adverse outcome. Particularly in the case of SARS-CoV2 infection, mounting evidence suggests that peripheral B cell alymphocytosis is linked to a poor prognosis.

B cells, antibody-secreting cells, and virus-specific antibodies respond to herpes simplex virus 2 reactivation in skin

Tissue-based T cells are important effectors in the prevention and control of mucosal viral infections; less is known about tissue-based B cells. We demonstrate that B cells and antibody-secreting cells (ASCs) are present in inflammatory infiltrates in skin biopsy specimens from study participants during symptomatic herpes simplex virus 2 (HSV-2) reactivation and early healing. Both CD20+ B cells, most of which are antigen inexperienced based on their coexpression of IgD, and ASCs - characterized by dense IgG RNA expression in combination with CD138, IRF4, and Blimp-1 RNA - were found to colocalize with T cells. ASCs clustered with CD4+ T cells, suggesting the potential for crosstalk. HSV-2-specific antibodies to virus surface antigens were also present in tissue and increased in concentration during HSV-2 reactivation and healing, unlike in serum, where concentrations remained static over time. B cells, ASCs, and HSV-specific antibody were rarely detected in biopsies of unaffected skin. Evaluation of samples from serial biopsies demonstrated that B cells and ASCs followed a more migratory than resident pattern of infiltration in HSV-affected genital skin, in contrast to T cells. Together, these observations suggest the presence of distinct phenotypes of B cells in HSV-affected tissue; dissecting their role in reactivation may reveal new therapeutic avenues to control these infections.

Mass Spectrometric Characterization of HSV-1 L-Particles From Human Dendritic Cells and BHK21 Cells and Analysis of Their Functional Role

Herpes simplex virus type 1 (HSV-1) is a very common human pathogenic virus among the world’s population. The lytic replication cycle of HSV-1 is, amongst others, characterized by a tripartite viral gene expression cascade, the assembly of nucleocapsids involving their subsequent nuclear egress, tegumentation, re-envelopment and the final release of progeny viral particles. During productive infection of a multitude of different cell types, HSV-1 generates not only infectious heavy (H-) particles, but also non-infectious light (L-) particles, lacking the capsid. In monocyte-derived mature dendritic cells (mDCs), HSV-1 causes a non-productive infection with the predominant release of L-particles. Until now, the generation and function of L-particles is not well understood, however, they are described as factors transferring viral components to the cellular microenvironment. To obtain deeper insights into the L-particle composition, we performed a mass-spectrometry-based analysis of L-particles derived from HSV-1-infected mDCs or BHK21 cells and H-particles from the latter one. In total, we detected 63 viral proteins in both H- and L-particle preparations derived from HSV-1-infected BHK21 cells. In L-particles from HSV-1-infected mDCs we identified 41 viral proteins which are differentially distributed compared to L-particles from BHK21 cells. In this study, we present data suggesting that L-particles modify mDCs and suppress their T cell stimulatory capacity. Due to the plethora of specific viral proteins incorporated into and transmitted by L-particles, it is tempting to speculate that L-particles manipulate non-infected bystander cells for the benefit of the virus.

Model of vaccine efficacy against HSV-2 superinfection of HSV-1 seropositive mice demonstrates protection by antibodies mediating cellular cytotoxicity

A majority of the world’s population is infected with HSV-1, highlighting the need for vaccines that are effective in HSV-1-seropositive hosts. We established a superinfection model by infecting mice intranasally with a sublethal dose of HSV-1, which results in high rates of seropositive, latently infected mice susceptible to HSV-2 superinfection. Sublethal HSV-1 induced a predominantly neutralizing antibody response. Vaccination of HSV-1-seropositive mice with recombinant adjuvanted glycoprotein D (rgD-2) failed to significantly boost HSV total or neutralizing antibody responses and provided no significant increased protection against HSV-2 superinfection compared to control-vaccinated HSV-1-seropositive mice. In contrast, immunization with a single-cycle virus deleted in gD (ΔgD-2) significantly boosted total HSV-specific antibody titers and elicited new antibody-dependent cell-mediated cytotoxicity responses, providing complete protection from death following HSV-2 superinfection. This model recapitulates clinical responses to natural infection and the rgD-2 vaccine trial outcomes and suggests that ΔgD-2 may prove protective in HSV-1-seropositive hosts.

Host Src controls gallid alpha herpesvirus 1 intercellular spread in a cellular fatty acid metabolism-dependent manner

Viral spread is considered a promising target for antiviral therapeutics, but the associated mechanisms remain unclear for gallid alpha herpesvirus 1 (ILTV). We previously identified proto-oncogene tyrosine-protein kinase Src (Src) as a crucial host determinant of ILTV infection. The present study revealed accelerated spread of ILTV upon Src inhibition. This phenomenon was independent of either viral replication or the proliferation of infected cells and could not be compromised by neutralizing antibody. Neither extracellular vesicles nor the direct cytosol-to-cytosol connections between adjacent cells contributed to the enhanced spread of ILTV upon Src inhibition. Further genome-wide transcriptional profile analyses in combination with functional validation identified fatty acid metabolism as an essential molecular event during modulation of the intercellular spread and subsequent cytopathic effect of ILTV by Src. Overall, these data suggest that Src controls the cell-to-cell spread of ILTV in a cellular fatty acid metabolism-dependent manner, which determines the virus's cytopathic effect.