Implications for herpes simplex virus vaccine strategies based on antibodies produced to herpes simplex virus type 1 glycoprotein gC immune evasion domains

A Trivalent HSV-2 gC2, gD2, gE2 Nucleoside-Modified mRNA-LNP Vaccine Provides Outstanding Protection in Mice against Genital and Non-Genital HSV-1 Infection, Comparable to the Same Antigens Derived from HSV-1

HSV-1 disease is a significant public health burden causing orofacial, genital, cornea, and brain infection. We previously reported that a trivalent HSV-2 gC2, gD2, gE2 nucleoside-modified mRNA-lipid nanoparticle (LNP) vaccine provides excellent protection against vaginal HSV-1 infection in mice. Here, we evaluated whether this HSV-2 gC2, gD2, gE2 vaccine is as effective as a similar HSV-1 mRNA LNP vaccine containing gC1, gD1, and gE1 in the murine lip and genital infection models. Mice were immunized twice with a total mRNA dose of 1 or 10 µg. The two vaccines produced comparable HSV-1 neutralizing antibody titers, and surprisingly, the HSV-2 vaccine stimulated more potent CD8+ T-cell responses to gE1 peptides than the HSV-1 vaccine. Both vaccines provided complete protection from clinical disease in the lip model, while in the genital model, both vaccines prevented death and genital disease, but the HSV-1 vaccine reduced day two vaginal titers slightly better at the 1 µg dose. Both vaccines prevented HSV-1 DNA from reaching the trigeminal or dorsal root ganglia to a similar extent. We conclude that the trivalent HSV-2 mRNA vaccine provides outstanding protection against HSV-1 challenge at two sites and may serve as a universal prophylactic vaccine for HSV-1 and HSV-2.

A trivalent gC2/gD2/gE2 vaccine for herpes simplex virus generates antibody responses that block immune evasion domains on gC2 better than natural infection

Vaccines for prevention and treatment of genital herpes are high public health priorities. Our approach towards vaccine development is to focus on blocking virus entry mediated by herpes simplex virus type 2 (HSV-2) glycoprotein D (gD2) and to prevent the virus from evading complement and antibody attack by blocking the immune evasion domains on HSV-2 glycoproteins C (gC2) and E (gE2), respectively. HSV-2 gC2 and gE2 are expressed on the virion envelope and infected cell surface where they are potential targets of antibodies that bind and block their immune evasion activities. We demonstrate that antibodies produced during natural infection in humans or intravaginal inoculation in guinea pigs bind to gC2 but generally fail to block the immune evasion domains on this glycoprotein. In contrast, immunization of naïve or previously HSV-2-infected guinea pigs with gC2 subunit antigen administered with CpG and alum as adjuvants produces antibodies that block domains involved in immune evasion. These results indicate that immune evasion domains on gC2 are weak antigens during infection, yet when used as vaccine immunogens with adjuvants the antigens produce antibodies that block immune evasion domains.

DNA vaccine expressing herpes simplex virus 1 glycoprotein C and D protects mice against herpes simplex keratitis

AIM

To investigate whether DNA vaccine encoding herpes simplex virus 1 (HSV-1) glycoprotein C (gC) and glycoprotein D (gD) will achieve better protective effect against herpes simplex keratitis (HSK) than DNA vaccine encoding gD alone.

METHODS

DNA vaccine expressing gD or gC combined gD (gD.gC) were constructed and carried by chitosan nanoparticle. The expression of fusion protein gD and gC were detected in DNA/nanoparticle transfected 293T cells by Western-blot. For immunization, mice were inoculated with DNA/nanoparticle for 3 times with 2wk interval, and two weeks after the final immunization, the specific immune responses and clinical degrees of primary HSK were evaluated.

RESULTS

Fusion protein gD.gC could be expressed successfully in cultured 293T cells. And, pRSC-gC.gD-IL21 DNA/chitosan nanoparticle could effectively elicit strongest humoral and cellular immune response in primary HSK mice evidenced by higher levels of specific neutralizing antibody and sIgA production, enhanced cytotoxicities of splenocytes and nature killer cells (NK), when compared with those of gD alone or mocked vaccine immunized mice. As a result, gC-based vaccine immunized mice showed least HSK disease.

CONCLUSION

gC-based DNA vaccine could effectively prevent the progress of primary HSK, suggesting that this DNA vaccine could be a promising vaccine for HSK treatment in the future.

Immunization with a vaccine combining herpes simplex virus 2 (HSV-2) glycoprotein C (gC) and gD subunits improves the protection of dorsal root ganglia in mice and reduces the frequency of recurrent vaginal shedding of HSV-2 DNA in guinea pigs compared to immunization with gD alone

Attempts to develop a vaccine to prevent genital herpes simplex virus 2 (HSV-2) disease have been only marginally successful, suggesting that novel strategies are needed. Immunization with HSV-2 glycoprotein C (gC-2) and gD-2 was evaluated in mice and guinea pigs to determine whether adding gC-2 to a gD-2 subunit vaccine would improve protection by producing antibodies that block gC-2 immune evasion from complement. Antibodies produced by gC-2 immunization blocked the interaction between gC-2 and complement C3b, and passive transfer of gC-2 antibody protected complement-intact mice but not C3 knockout mice against HSV-2 challenge, indicating that gC-2 antibody is effective, at least in part, because it prevents HSV-2 evasion from complement. Immunization with gC-2 also produced neutralizing antibodies that were active in the absence of complement; however, the neutralizing titers were higher when complement was present, with the highest titers in animals immunized with both antigens. Animals immunized with the gC-2-plus-gD-2 combination had robust CD4+ T-cell responses to each immunogen. Multiple disease parameters were evaluated in mice and guinea pigs immunized with gC-2 alone, gD-2 alone, or both antigens. In general, gD-2 outperformed gC-2; however, the gC-2-plus-gD-2 combination outperformed gD-2 alone, particularly in protecting dorsal root ganglia in mice and reducing recurrent vaginal shedding of HSV-2 DNA in guinea pigs. Therefore, the gC-2 subunit antigen enhances a gD-2 subunit vaccine by stimulating a CD4+ T-cell response, by producing neutralizing antibodies that are effective in the absence and presence of complement, and by blocking immune evasion domains that inhibit complement activation.

Immunization with HSV-1 glycoprotein C prevents immune evasion from complement and enhances the efficacy of an HSV-1 glycoprotein D subunit vaccine

Herpes simplex virus type 1 (HSV-1) glycoprotein C (gC-1) binds complement component C3b and inhibits complement-mediated immunity. HSV-1 glycoprotein D (gD-1) is a potent immunogen and a candidate antigen for a subunit vaccine. We evaluated whether combined immunization with gD-1 and gC-1 provides better protection against challenge than gD-1 alone based on antibodies to gC-1 preventing HSV-1-mediated immune evasion. IgG purified from mice immunized with gC-1 blocked C3b binding to gC-1 and greatly increased neutralization by gD-1 IgG in the presence of complement. Passive transfer of gC-1 IgG protected complement intact mice against HSV-1 challenge but not C3 knockout mice, indicating that gC-1 antibody activity in vivo is complement-dependent. Immunizing mice with gD-1 and gC-1 provided better protection than gD-1 alone in preventing zosteriform disease and infection of dorsal root ganglia. Therefore, gC-1 immunization prevents HSV-1 evasion from complement and enhances the protection provided by gD-1 immunization.

Blocking antibody access to neutralizing domains on glycoproteins involved in entry as a novel mechanism of immune evasion by herpes simplex virus type 1 glycoproteins C and E

Herpes simplex virus type 1 (HSV-1) glycoprotein C (gC) blocks complement activation, and glycoprotein E (gE) interferes with IgG Fc-mediated activities. While evaluating gC- and gE-mediated immune evasion in human immunodeficiency virus (HIV)-HSV-1-coinfected subjects, we noted that antibody alone was more effective at neutralizing a strain with mutations in gC and gE (gC/gE) than a wild-type (WT) virus. This result was unexpected since gC and gE are postulated to interfere with complement-mediated neutralization. We used pooled human immunoglobulin G (IgG) from HIV-negative donors to confirm the results and evaluated mechanisms of the enhanced antibody neutralization. We demonstrated that differences in antibody neutralization cannot be attributed to the concentrations of HSV-1 glycoproteins on the two viruses or to the absence of an IgG Fc receptor on the gC/gE mutant virus or to enhanced neutralization of the mutant virus by antibodies that target only gB, gD, or gH/gL, which are the glycoproteins involved in virus entry. Since sera from HIV-infected subjects and pooled human IgG contain antibodies against multiple glycoproteins, we determined whether differences in neutralization become apparent when antibodies to gB, gD, or gH/gL are used in combination. Neutralization of the gC/gE mutant was greatly increased compared that of WT virus when any two of the antibodies against gB, gD, or gH/gL were used in combination. These results suggest that gC and gE on WT virus provide a shield against neutralizing antibodies that interfere with gB-gD, gB-gH/gL, or gD-gH/gL interactions and that one function of virus neutralization is to prevent interactions between these glycoproteins.

Anti-Immunology: Evasion of the Host Immune System by Bacterial and Viral Pathogens

Multicellular organisms possess very sophisticated defense mechanisms that are designed to effectively counter the continual microbial insult of the environment within the vertebrate host. However, successful microbial pathogens have in turn evolved complex and efficient methods to overcome innate and adaptive immune mechanisms, which can result in disease or chronic infections. Although the various virulence strategies used by viral and bacterial pathogens are numerous, there are several general mechanisms that are used to subvert and exploit immune systems that are shared between these diverse microbial pathogens. The success of each pathogen is directly dependant on its ability to mount an effective anti-immune response within the infected host, which can ultimately result in acute disease, chronic infection, or pathogen clearance. In this review, we highlight and compare some of the many molecular mechanisms that bacterial and viral pathogens use to evade host immune defenses.