Correlate of Immune Protection Against HSV-1 Genital Disease in Vaccinated Women

Gallagher

et al. 2015

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. IMPORTANCEWe 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. Herpes simplex virus 1 (HSV-1) and HSV-2 cause human diseases, ranging from benign cold sores to life-threatening infections such as encephalitis and neonatal HSV disease (1, 2). The hallmark of HSV infection is the ability of each serotype to establish a lifelong latent infection in sensory neurons. Reactivation can lead to clinical symptoms such as oral or genital lesions. Currently, 47% of the U.S. population is seropositive for HSV-1 and 16% are seropositive for HSV-2 (3). Many seropositive individuals are asymptomatic, although a number of people shed virus regardless of clinical signs of disease (4). However,...

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confidence: 99%

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

Cairns

Gallagher

et al. 2015

“…Immunization with multiple antigens involved in virus entry failed to improve the protection provided by gD2 alone (31). We base our vaccine approach on the observation that most viral vaccines effective against mucosal infection, such as HSV-2, depend on antibodies for protection (32,33). In addition, the gC2 and gE2 immune evasion molecules that we are targeting are expressed on the virion envelope and at the infected cell surface; therefore, they are accessible to blocking antibodies, while T-cell immune evasion molecules are located within infected cells and are difficult to access.…”

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confidence: 99%

Blocking Herpes Simplex Virus 2 Glycoprotein E Immune Evasion as an Approach To Enhance Efficacy of a Trivalent Subunit Antigen Vaccine for Genital Herpes

Awasthi

Shaw

et al. 2014

Herpes simplex virus 2 (HSV-2) subunit antigen vaccines targeting virus entry molecules have failed to prevent genital herpes in human trials. Our approach is to include a virus entry molecule and add antigens that block HSV-2 immune evasion. HSV-2 glycoprotein C (gC2) is an immune evasion molecule that inhibits complement. We previously reported that adding gC2 to gD2 improved vaccine efficacy compared to the efficacy of either antigen alone in mice and guinea pigs. Here we demonstrate that HSV-2 glycoprotein E (gE2) functions as an immune evasion molecule by binding the IgG Fc domain. HSV-2 gE2 is synergistic with gC2 in protecting the virus from antibody and complement neutralization. Antibodies produced by immunization with gE2 blocked gE2-mediated IgG Fc binding and cell-to-cell spread. Mice immunized with gE2 were only partially protected against HSV-2 vaginal challenge in mice; however, when gE2 was added to gC2/gD2 to form a trivalent vaccine, neutralizing antibody titers with and without complement were significantly higher than those produced by gD2 alone. Importantly, the trivalent vaccine protected the dorsal root ganglia (DRG) of 32/33 (97%) mice between days 2 and 7 postchallenge, compared with 27/33 (82%) in the gD2 group. The HSV-2 DNA copy number was significantly lower in mice immunized with the trivalent vaccine than in those immunized with gD2 alone. The extent of DRG protection using the trivalent vaccine was better than what we previously reported for gC2/gD2 immunization. Therefore, gE2 is a candidate antigen for inclusion in a multivalent subunit vaccine that attempts to block HSV-2 immune evasion. IMPORTANCEHerpes simplex virus is the most common cause of genital ulcer disease worldwide. Infection results in emotional distress for infected individuals and their partners, is life threatening for infants exposed to herpes during childbirth, and greatly increases the risk of individuals acquiring and transmitting HIV infection. A vaccine that prevents genital herpes infection will have major public health benefits. Our vaccine approach includes strategies to prevent the virus from evading immune attack. Mice were immunized with a trivalent vaccine containing an antigen that induces antibodies to block virus entry and two antigens that induce antibodies that block immune evasion from antibody and complement. Immunized mice demonstrated no genital disease, and 32/33 (97%) animals had no evidence of infection of dorsal root ganglia, suggesting that the vaccine may prevent the establishment of latency and recurrent infections. T he efficacy of the herpes simplex virus 2 (HSV-2) glycoprotein D (gD2) subunit antigen vaccine for prevention of genital herpes was evaluated in three large human trials (1, 2). In 2002, the first two trials reported that the gD2 vaccine prevented HSV-2 genital disease in HSV-1/HSV-2-seronegative women; however, this result was not reproduced in the 2012 Herpevac trial for women that showed gD2 vaccine efficacy in preventing genital disease caused by HSV-1 but n...

“…They also showed that deletion of gC or gE from HSV-2 increased its susceptibility to neutralization by gD antibodies and suggested that differential effects of gC and gE in the two HSV serotypes may account for the observed differences in neutralization. Separately, Belshe et al (13) reported that among the gD2 vaccine trial participants, serum antibodies against gD2, but not cell-mediated immunity, correlated with protection against HSV-1 genital disease. Given the documented relevance of gD-specific serum antibodies to virus neutralization and protection from disease, our goal in the current study was to dissect the humoral response to gD2 epitopes elicited by the vaccine.…”

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confidence: 99%

Repertoire of Epitopes Recognized by Serum IgG from Humans Vaccinated with Herpes Simplex Virus 2 Glycoprotein D

Whitbeck

Cairns

et al. 2014

). The vaccine consisted of a soluble form of herpes simplex virus 2 (HSV-2) glycoprotein D (gD2) with adjuvant. The goal of the current study was to examine the composition of the humoral response to gD2 within a selected subset of vaccinated individuals. Serum samples from 30 vaccine recipients were selected based upon relative enzyme-linked immunosorbent assay (ELISA) titers against gD2; 10 samples had high titers, 10 had medium titers, and the remaining 10 had low ELISA titers. We employed a novel, biosensor-based monoclonal antibody (MAb)-blocking assay to determine whether gD2 vaccination elicited IgG responses against epitopes overlapping those of well-characterized MAbs. Importantly, IgGs from the majority of gD2-immunized subjects competed for gD binding with four antigenically distinct virus-neutralizing MAbs (MC2, MC5, MC23, and DL11). Screening of patient IgGs against overlapping peptides spanning the gD2 ectodomain revealed that about half of the samples contained antibodies against linear epitopes within the N and C termini of gD2. We found that the virus-neutralizing abilities of the 10 most potent samples correlated with overall gD-binding activity and to an even greater extent with the combined content of IgGs against the epitopes of MAbs MC2, MC5, MC23, and DL11. This suggests that optimal virus-neutralizing activity is achieved by strong and balanced responses to the four major discontinuous neutralizing epitopes of gD2. IMPORTANCESeveral herpes simplex virus 2 (HSV-2) subunit vaccine studies have been conducted in human subjects using a recombinant form of HSV-2 glycoprotein D (gD2). Although several distinct, well-characterized virus-neutralizing epitopes on gD2 are targeted by murine monoclonal antibodies, it is not known whether the same epitopes are targeted by the humoral response to gD2 in humans. We have developed a novel, biosensor-based competition assay to directly address this important question. Using this approach, we identified epitopes that elicit strong humoral responses in humans, as well as other epitopes that elicit much weaker responses. These data provide new insight into the human response to known neutralizing gD2 epitopes and reveal characteristics of this response that may guide future vaccine development.