Neutralizing activity of antibodies against the major herpes simplex virus type 1 glycoproteins

Oncolytic herpes simplex virus tumor targeting and neutralization escape by engineering viral envelope glycoproteins

Oncolytic herpes simplex viruses (oHSVs) have been approved for clinical usage and become more and more popular for tumor virotherapy. However, there are still many issues for the oHSVs used in clinics and clinical trials. The main issues are the limited anti-tumor effects, intratumor injection, and some side effects. To overcome such challenges, here we review the genetic engineering of the envelope glycoproteins for oHSVs to target tumors specifically, and at the same time we summarize the many neutralization antibodies against the envelope glycoproteins and align the neutralization epitopes with functional domains of the respective glycoproteins for future identification of new functions of the glycoproteins and future engineering of the epitopes to escape from host neutralization.

Prophylactic Herpes Simplex Virus 2 (HSV-2) Vaccines Adjuvanted with Stable Emulsion and Toll-Like Receptor 9 Agonist Induce a Robust HSV-2-Specific Cell-Mediated Immune Response, Protect against Symptomatic Disease, and Reduce the Latent Viral Reservoir

Several prophylactic vaccines targeting herpes simplex virus 2 (HSV-2) have failed in the clinic to demonstrate sustained depression of viral shedding or protection from recurrences. Although these vaccines have generated high titers of neutralizing antibodies (NAbs), their induction of robust CD8 T cells has largely been unreported, even though evidence for the importance of HSV-2 antigen-specific CD8 T cells is mounting in animal models and in translational studies involving subjects with active HSV-2-specific immune responses. We developed a subunit vaccine composed of the NAb targets gD and gB and the novel T cell antigen and tegument protein UL40, and we compared this vaccine to a whole-inactivated-virus vaccine (formaldehyde-inactivated HSV-2 [FI-HSV-2]). We evaluated different formulations in combination with several Th1-inducing Toll-like receptor (TLR) agonists in vivo In mice, the TLR9 agonist cytosine-phosphate-guanine (CpG) oligodeoxynucleotide formulated in a squalene-based oil-in-water emulsion promoted most robust, functional HSV-2 antigen-specific CD8 T cell responses and high titers of neutralizing antibodies, demonstrating its superiority to vaccines adjuvanted by monophosphoryl lipid A (MPL)-alum. We further established that FI-HSV-2 alone or in combination with adjuvants as well as adjuvanted subunit vaccines were successful in the induction of NAbs and T cell responses in guinea pigs. These immunological responses were coincident with a suppression of vaginal HSV-2 shedding, low lesion scores, and a reduction in latent HSV-2 DNA in dorsal root ganglia to undetectable levels. These data support the further preclinical and clinical development of prophylactic HSV-2 vaccines that contain appropriate antigen and adjuvant components responsible for programming elevated CD8 T cell responses.IMPORTANCE Millions of people worldwide are infected with herpes simplex virus 2 (HSV-2), and to date, an efficacious prophylactic vaccine has not met the rigors of clinical trials. Attempts to develop a vaccine have focused primarily on glycoproteins necessary for HSV-2 entry as target antigens and to which the dominant neutralizing antibody response is directed during natural infection. Individuals with asymptomatic infection have exhibited T cell responses against specific HSV-2 antigens not observed in symptomatic individuals. We describe for the first time the immunogenicity profile in animal models of UL40, a novel HSV-2 T cell antigen that has been correlated with asymptomatic HSV-2 disease. Additionally, vaccine candidates adjuvanted by a robust formulation of the CpG oligonucleotide delivered in emulsion were superior to unadjuvanted or MPL-alum-adjuvanted formulations at eliciting a robust cell-mediated immune response and blocking the establishment of a latent viral reservoir in the guinea pig challenge model of HSV-2 infection.

Patient-Specific Neutralizing Antibody Responses to Herpes Simplex Virus Are Attributed to Epitopes on gD, gB, or Both and Can Be Type Specific

Herpes simplex virus 1 (HSV-1) and HSV-2 infect many humans and establish a latent infection in sensory ganglia. Although some infected people suffer periodic recurrences, others do not. Infected people mount both cell-mediated and humoral responses, including the production of virus-neutralizing antibodies (Abs) directed at viral entry glycoproteins. Previously, we examined IgGs from 10 HSV-seropositive individuals; all neutralized virus and were directed primarily against gD or gD+gB. Here, we expand our studies and examine 32 additional sera from HSV-infected individuals, 23 of whom had no recurrent disease. Using an Octet RED96 system, we screened all 32 serum samples directly for both glycoprotein binding and competition with known neutralizing anti-gD and -gB monoclonal Abs (MAbs). On average, the recurrent cohort exhibited higher binding to gD and gB and had higher neutralization titers. There were similar trends in the blocking of MAbs to critical gD and gB epitopes. When we depleted six sera of Abs to specific glycoproteins, we found different types of responses, but always directed primarily at gD and/or gB. Interestingly, in one dual-infected person, the neutralizing response to HSV-2 was due to gD2 and gB2, whereas HSV-1 neutralization was due to gD1 and gB1. In another case, virus neutralization was HSV-1 specific, with the Ab response directed entirely at gB1, despite this serum blocking type-common anti-gD and -gB neutralizing MAbs. These data are pertinent in the design of future HSV vaccines since they demonstrate the importance of both serotypes of gD and gB as immunogens.

IMPORTANCE

We previously showed that people infected with HSV produce neutralizing Abs directed against gD or a combination of gD+gB (and in one case, gD+gB+gC, which was HSV-1 specific). In this more extensive study, we again found that gD or gD+gB can account for the virus neutralizing response and critical epitopes of one or both of these proteins are represented in sera of naturally infected humans. However, we also found that some individuals produced a strong response against gB alone. In addition, we identified type-specific contributions to HSV neutralization from both gD and gB. Contributions from the other entry glycoproteins, gC and gH/gL, were minimal and limited to HSV-1 neutralization. Knowing the variations in how humans see and mount a response to HSV will be important to vaccine development.

Dissection of the antibody response against herpes simplex virus glycoproteins in naturally infected humans

Relatively little is known about the extent of the polyclonal antibody (PAb) repertoire elicited by herpes simplex virus (HSV) glycoproteins during natural infection and how these antibodies affect virus neutralization. Here, we examined IgGs from 10 HSV-seropositive individuals originally classified as high or low virus shedders. All PAbs neutralized virus to various extents. We determined which HSV entry glycoproteins these PAbs were directed against: glycoproteins gB, gD, and gC were recognized by all sera, but fewer sera reacted against gH/gL. We previously characterized multiple mouse monoclonal antibodies (MAbs) and mapped those with high neutralizing activity to the crystal structures of gD, gB, and gH/gL. We used a biosensor competition assay to determine whether there were corresponding human antibodies to those epitopes. All 10 samples had neutralizing IgGs to gD epitopes, but there were variations in which epitopes were seen in individual samples. Surprisingly, only three samples contained neutralizing IgGs to gB epitopes. To further dissect the nature of these IgGs, we developed a method to select out gD- and gB-specific IgGs from four representative sera via affinity chromatography, allowing us to determine the contribution of antibodies against each glycoprotein to the overall neutralization capacity of the serum. In two cases, gD and gB accounted for all of the neutralizing activity against HSV-2, with a modest amount of HSV-1 neutralization directed against gC. In the other two samples, the dominant response was to gD.

IMPORTANCE

Antibodies targeting functional epitopes on HSV entry glycoproteins mediate HSV neutralization. Virus-neutralizing epitopes have been defined and characterized using murine monoclonal antibodies. However, it is largely unknown whether these same epitopes are targeted by the humoral response to HSV infection in humans. We have shown that during natural infection, virus-neutralizing antibodies are principally directed against gD, gB, and, to a lesser extent, gC. While several key HSV-neutralizing epitopes within gD and gB are commonly targeted by human serum IgG, others fail to induce consistent responses. These data are particularly relevant to the design of future HSV vaccines.

Immunogenicity and safety of different formulations of an adjuvanted glycoprotein D genital herpes vaccine in healthy adults: a double-blind randomized trial

Herpes simplex virus (HSV) type 2 (HSV-2) is the main cause of genital and neonatal herpes and is highly prevalent worldwide. Previous phase I and II studies showed the immunogenicity and safety of the candidate prophylactic HSV-2 glycoprotein D-based subunit vaccine (gD2-AS04), containing aluminum hydroxide and 3-O-deacylated monophosphoryl lipid A (MPL) as adjuvant (AS04), in healthy adults. The primary objective of the study presented here was to compare the immunogenicity and safety of five different vaccine formulations: 3 different antigen doses [20, 40 or 80 μg of truncated glycoprotein D from HSV-2 strain (gD-2t)], different aluminum salts [AlPO₄ or Al(OH)₃], different preservatives or different volumes of vaccine (0.5 or 1 ml). One hundred and fifty healthy men and women aged 18–45 years, with negative serological markers for HSV-1 and HSV-2 infection, were vaccinated with one of 5 formulations of the gD2-AS04 candidate vaccine according to a 0-, 1-, 6-month schedule. No statistically significant difference was observed in humoral or cellular immune responses between different antigen doses or the different aluminum salts, preservatives or volumes of vaccine. The gD2-AS04 vaccine was well tolerated by study participants for the duration of the study period. Local symptoms were more frequently reported than general symptoms, with muscle stiffness and/or injection site redness being the most frequently reported. Overall, the incidence of adverse events was comparable in all groups. Based on these results the gD2-AS04 formulation, containing 20 μg of gD-2t, was selected for evaluation of prophylactic efficacy in further clinical trials.

Therapeutic vaccination against chronic viral infections

Chronic viral infections such as those caused by hepatitis B virus, human papilloma virus, herpes simplex virus, and HIV, in theory, present logical targets of active specific immunotherapy. Indeed, immunological mechanisms are involved in several aspects of their pathogenesis and natural course, such as virus persistence, destruction of infected cells and control of viral replication. Therapeutic vaccination could therefore be an adequate replacement for, or adjunct to, existing therapies. Almost all approaches to therapeutic vaccination have been evaluated in those four disease areas. Despite encouraging results in animals none of these attempts has, so far, been completely successful in the human setting. However, with a better understanding of the immunological mechanisms involved in the control of disease successful therapeutic vaccines, used alone or in combination with other therapies, are an achievable goal.

Directed selection of recombinant human monoclonal antibodies to herpes simplex virus glycoproteins from phage display libraries

Human monoclonal antibodies have considerable potential in the prophylaxis and treatment of viral disease. However, only a few such antibodies suitable for clinical use have been produced to date. We have previously shown that large panels of human recombinant monoclonal antibodies against a plethora of infectious agents, including herpes simplex virus types 1 and 2, can be established from phage display libraries. Here we demonstrate that facile cloning of recombinant Fab fragments against specific viral proteins in their native conformation can be accomplished by panning phage display libraries against viral glycoproteins "captured" from infected cell extracts by specific monoclonal antibodies immobilized on ELISA plates. We have tested this strategy by isolating six neutralizing recombinant antibodies specific for herpes simplex glycoprotein gD or gB, some of which are against conformationally sensitive epitopes. By using defined monoclonal antibodies for the antigen-capture step, this method can be used for the isolation of antibodies to specific regions and epitopes within the target viral protein. For instance, monoclonal antibodies to a nonneutralizing epitope can be used in the capture step to clone antibodies to neutralizing epitopes, or antibodies to a neutralizing epitope can be used to clone antibodies to a different neutralizing epitope. Furthermore, by using capturing antibodies to more immunodominant epitopes, one can direct the cloning to less immunogenic ones. This method should be of value in generating antibodies to be used both in the prophylaxis and treatment of viral infections and in the characterization of the mechanisms of antibody protective actions at the molecular level.

An evaluation of a hemagglutination-inhibition test for the detection of antibodies to herpes simplex virus type 1

BACKGROUND

We have recently demonstrated the ability of herpes simplex virus type 1 (HSV-1) to agglutinate mouse red blood cells, and identified glycoprotein C (gC-1) as a major virus hemagglutinin. Based on this a classical hemagglutination-inhibition (HI) assay was developed.

OBJECTIVES

Regarding significant structural differences between HSV-1 gC-1 and its herpes simplex virus type 2 (HSV-2) counterpart, gC-2, the possibility of application of a classical HI assay for the detection of HSV-1-specific antibodies was explored.

STUDY DESIGN

HI antibody titers were compared with those of gC-1-specific enzyme-linked immunoassay (ELISA), and with the results of the standard gG-1- and gG-2-specific immunodot enzymatic assays for the detection of type-specific antibodies to HSV-1 and HSV-2 respectively.

RESULTS

The sensitivity of HI test was 89% and 97% of that gC-1-ELISA and gG-1-immunodot respectively. Approximately 21% of serum specimens, defined as containing antibodies specific for only HSV-2, showed low HI titers. Heterotypic reactivity with purified gC-1 antigen was also observed in both ELISA and immunoblot assays.

CONCLUSION

Antibodies detectable in HI assay were mainly HSV-1-specific; however, a limited degree of serologic reactivity between HSV-2-specific sera and HSV-1 hemagglutinin also occurred. Thus, our results confirmed prevalent opinion about the presence of a limited number of antigenic determinants shared by HSV-1 gC-1 and HSV-2 gC-2.

Vaccinating guinea pigs with recombinant glycoprotein D of herpes simplex virus in an efficacious adjuvant formulation elicits protection against vaginal infection

Guinea pigs were immunized with glycoprotein gD-2t in SAF-m or saline, then challenged with herpes simplex virus, type 2 (HSV-2). Animals given gD-2t in SAF-m had higher anti-gD-2t antibodies, fewer and less severe vaginal lesions, and decreased ganglionic latency compared to animals given gD-2t in saline. Leucocytes from animals vaccinated with gD-2t in SAF-m had greater proliferative responses to gD-2t in vitro than cells from control animals. MHC II-restricted, gD-2t-specific cytotoxic T cells were induced in guinea pigs vaccinated with gD-2t in SAF-m. Thus, immunization of guinea pigs with gD-2t in SAF-m markedly reduced the incidence and severity of primary HSV-2 by eliciting both humoral and cell-mediated responses.

The diagnostic significance of the polymerase chain reaction and isoelectric focusing in herpes simplex virus encephalitis

In this study, serum and CSF samples of 55 neurological patients have been examined to confirm the diagnosis of herpes simplex virus encephalitis (HSVE). Different methods were applied, including serological titer evaluations, determination of intrathecally-produced HSV-specific antibodies by isoelectric focusing with affinity immunoblotting (IEF), as well as HSV-specific ELISA and HSV-specific polymerase chain reaction (PCR). The results of IEF and PCR have been compared and contrasted to develop general directions for virological diagnosis of HSVE. Of 14 patients suffering from clinically diagnosed HSVE, HSVE was confirmed in 12 cases by the demonstration of PCR or IEF positivity. A HSV-specific CNS infection could be excluded in 2 of these 14 patients. In 17 patients suffering from non-HSVE, PCR and IEF results were negative. Twenty-four patients, suffering from other neurological diseases, serving as a control group, were PCR- and HSV-IEF-negative. The study indicated that there are two possibilities for unequivocal demonstration of HSV-specific CNS involvement: first, performance of PCR especially in the acute phase of disease and in suspicious relapses, and second, performance of HSV-specific IEF for determination of intrathecally synthesized HSV-specific antibodies. It is suggested that these two methods should be introduced in routine diagnosis of viral encephalitis.

Protective effect of anti-glycoprotein D antibody on herpetic chorioretinitis in newborn rabbits

Subcutaneous injection of type 2 herpes simplex virus (HSV-2) (10(3) PFU) to newborn rabbits produced severe skin lesions and wide dissemination of the virus to various organs including the eye. Ocular lesions were characterized by retinal folds and choroiditis. HSV could be isolated from mononuclear cells (MNCs) of infected animal blood. Newborn rabbits treated with monoclonal antibody (MAb) against glycoprotein D (gD) of HSV on days 0, 2 and 4 postinfection had little or no skin lesions (0.0-2.3 mm) compared to controls (2.8-13.0 mm). In addition, the MAb treatment significantly suppressed dissemination of the virus to the eye (0% in MAb-treated vs 83% in control) and other organs and reduced the rate of chorioretinitis (0% in MAb-treated vs 50% in control). The treatment of HSV-infected MNCs with MAb resulted in 91-100% reduction in infectivity of the cells. The results suggest that anti-gD MAb protects newborn rabbits from HSV-2 eye infection by neutralizing the virus in skin and inactivating HSV-infected MNCs in blood.

HSV-1 gB and VZV gp-II crossreactive antibodies in human sera

The specificity and prevalence of human IgG antibodies crossreactive between HSV-1 (ANG) and VZV (Ellen) was examined in immunoblots. Using antibody fractions purified on HSV- and VZV-coated affinity chromatography columns and by preadsorption of sera with HSV and/or VZV lysates a crossreactivity between HSV-1 gB and VZV gp-II was demonstrated. Crossreaction of human IgG antibodies among other structural and nonstructural viral proteins, however, was not detected. The frequency of human IgG antibodies crossreactive between HSV-1 gB and VZV gp-II was highest in HSV-seropositive patients experiencing an acute primary VZV infection (4 out of 5 sera tested). In contrast, no crossreactive antibodies were found in sera of HSV-seronegative patients with acute primary VZV infection (0/6) or in sera from individuals with acute recurrent HSV or VZV infection (0/12). Analysis of sera from individuals with previous HSV and/or VZV infection showed the presence of antibodies crossreactive between HSV-1 gB and VZV gp-II in 3 out of 30 sera tested.

Reactivity of human sera with overlapping synthetic peptides of herpes simplex virus type 1 glycoprotein D

Thirty eight human sera, seropositive for herpes simplex virus (HSV) and 56 human sera, seronegative for HSV by immunofluorescence and by ELISA, were investigated for reactivity with a series of overlapping synthetic peptides of HSV type 1 glycoprotein D (gD-1). Thirty four out of the 38 human sera positive for HSV reacted with peptides located between residues 300 and 369; the HSV-negative sera reacted with six of the gD-1 peptides, but with none of the peptides within residues 300 to 369.

Identification of herpes simplex virus type 1 glycoproteins interacting with the cell surface

To investigate the interaction of herpes simplex virus type 1 (HSV-1) with the cell surface, we studied the formation of complexes by HSV-1 virion proteins with biotinylated cell membrane components. HSV-1 virion proteins reactive with surface components of HEp-2 and other cells were identified as gC, gB, and gD. Results from competition experiments suggested that binding of gC, gB, and gD occurred in a noncooperative way. The observed complex formation could be specifically blocked by monospecific rabbit antisera against gB and gD. The interaction of gD with the cell surface was also inhibited by monoclonal antibody IV3.4., whereas other gD-specific monoclonal antibodies, despite their high neutralizing activity, were not able to inhibit this interaction. Taken together, these data provide direct evidence that at least three of the seven known HSV-1 glycoproteins are able to form complexes with cellular surface structures.

Relatedness of glycoproteins expressed on the surface of simian herpes-virus virions and infected cells to specific HSV glycoproteins

The antigenic relatedness of the surface glycoprotein antigens of six herpesviruses indigenous to human and nonhuman primates was examined. Binding of anti-viral sera to viral antigens expressed on the surface of infected cells demonstrated that the surface antigens of herpes simplex virus type 1 (HSV 1), HSV 2, simian agent 8 (SA8), and Herpesvirus simiae (B virus) exhibit extensive cross-reactivity. Surface antigens of two viruses isolated from South American primates, H. saimiri 1 (HVS 1) and H. ateles 1 (HVA 1), were comparatively more virus-specific in their antigenic reactivity. Endpoint neutralization tests performed in the presence and absence of complement confirmed these results. Immunoprecipitation of viral proteins was used to identify those representing cross-reactive surface antigens. A glycoprotein of approximately 110,000-125,000 Daltons (110-125 k) was immunoprecipitated from cells infected with each of the six primate herpesvirus by antisera to each of the viruses. Using monospecific antisera, these glycoproteins were shown to be antigenically related to the gB glycoproteins of HSV. Although these glycoproteins were antigenically conserved among all six viruses, antibodies to the gB glycoproteins did not cross-neutralize heterologous viruses. A glycoprotein of approximately 60-70 k was precipitated from HSV 1, HSV 2, SA8, and B virus infected cells by antisera to each of these four viruses. These SA8 and B virus glycoproteins were shown to be antigenically related to the gD glycoproteins of HSV 1 and HSV 2 and to be involved in cross-neutralization among these viruses. Antisera to HVS 1 and HVA 1 did not recognize these gD glycoproteins nor was a glycoprotein of similar molecular weight precipitable from HVS 1 or HVA 1 infected cells by antisera to the other four viruses. Southern blot hybridizations using probes for HSV glycoprotein genes confirmed the conservation of the gB glycoproteins among all the simian viruses and of the gD gene in SA8 and B virus. A glycoprotein of approximately 75-80 k was, however, precipitated from HVS 1 and HVA 1 infected cells by antisera to either of these two viruses. In addition, at least one glycoprotein which appeared to be predominantly virus-specific in its reactivity was identified for five of the viruses.