Glycoprotein G enables HSV-2 neuroinvasion and provides protection as a glycosylated vaccine antigen
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A mouse study examined membrane-associated glycoprotein G of HSV-2 (mgG-2) both as a factor in infection and as a recombinant vaccine antigen. Mice immunized three times with the glycosylated antigen and then challenged genitally survived more often, had lower disease scores and had less viral DNA in nerve tissue than mice immunized with the same antigen stripped of both its N- and O-linked sugars. The work is preclinical — this study reports no vaccination data in people — and the authors state that animal vaccine models have so far not predicted clinical outcomes.
The infection arm compared wild-type HSV-2, a mutant that cannot make mgG-2 and a rescued strain in which the gene was put back, in two mouse strains infected vaginally. Without mgG-2 the virus still replicated in vaginal tissue but was severely impaired in spreading to the dorsal root ganglia and the central nervous system, and most infected mice survived. For the vaccine arm the antigen was made in CHO-K1 cells and its sugars mapped by mass spectrometry; of 70 possible O-linked sites, 12 carried glycans.
After genital challenge, survival was 93.7% in the group given the glycosylated antigen (n = 26) and 43.8% in the group given the antigen with both N- and O-linked glycans removed (n = 16). Mean disease score was 0.3 versus 2.7 in the same comparison, and the deglycosylated group also had more viral DNA in dorsal root ganglia and spinal cord. Removing N-linked glycans, O-linked glycans or sialic acids on their own did not take protection away; the loss appeared only when both glycan types were removed together.
Immunized mice mounted humoral and Th1-polarized CD4 T-cell responses. When spleen cells were restimulated with peptide pools, IFN-γ, IL-2 and TNF-α responses were lower in the deglycosylated-antigen group; restimulated with the intact antigen, only IL-2 differed significantly. This is a preclinical animal study of a vaccine antigen, not a vaccine in development: no clinical testing, sponsor or trial is reported, and the authors present the findings as a rationale for pursuing glycosylated mgG-2 in prophylactic and therapeutic vaccines. The paper itself notes that results in mice and guinea pigs have only partly translated to clinical trials, and that earlier prophylactic candidates built on gB-2 and gD-2 reached phase III without preventing HSV-2 infection.
That history is tracked here under Herpevac (gD2 subunit, GSK). One stated limit of the infection work is that viral load was not measured in tissues outside those on the described intravaginal infection route, so wider spread could not be confirmed.
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This entry was drafted with AI assistance and then checked. Every statement below was matched, word for word, to a passage in the full text of the source by software (21 passages and 17 numbers traced). A separate AI pass, run independently and shown only the source and the statements, then tried to find errors (supported, with a caveat noted, Sep 27, 2026). The editor (Mark) read and approved it on Sep 27, 2026. This is an editorial check, not peer review.
Editor revised two sentences flagged by the independent check (cytokine condition; human-data wording) before approval.
- In a mouse genital infection model, an HSV-2 mutant lacking membrane-associated glycoprotein G (mgG-2) still replicated in vaginal epithelial cells but was severely impaired in reaching the dorsal root ganglia and central nervous system.
Using a mouse genital infection model, we show that an mgG-2-deficient HSV-2 mutant replicates in vaginal epithelial cells but is severely impaired in dissemination to dorsal root ganglia and the central nervous system
- Mice were immunized intramuscularly three times with the respective recombinant antigen and then challenged genitally with 25 x LD50 of wild-type HSV-2.
C57BL/6 mice were immunized intramuscularly three times with respective antigen, followed by genital challenge with 25 x lethal dose 50% (LD 50 ) of HSV-2 WT
- Survival 14 days after challenge was 93.7% in mice immunized with the glycosylated antigen (n = 26) versus 43.8% in mice immunized with the antigen stripped of both N- and O-linked glycans (n = 16).
Immunization with EXCT4-mgG-2 conferred protection, showing 93.7% survival 14 days post infection (d.p.i.) (n = 26), while immunization with EXCT4-mgG-2(−N − O) resulted in a survival of 43.8% (p = 0.0005, n = 16)
- Mean disease score at 14 days was 0.3 with the glycosylated antigen compared with 2.7 with the deglycosylated antigen.
The mean disease score for mice immunized with EXCT4-mgG-2 was 0.3 at 14 d.p.i., as compared to a mean disease score of 2.7 for the mice immunized with EXCT4-mgG-2(−N − O)
- Mice immunized with the deglycosylated antigen had more HSV-2 DNA in dorsal root ganglia and in spinal cord than mice immunized with the glycosylated antigen.
Mice immunized with EXCT4-mgG-2(−N − O) presented with higher levels of HSV-2 DNA in DRG than mice immunized with EXCT4-mgG-2, 48 hours post infection (h.p.i.) (p = 0.013)
- Removing N-linked glycans, O-linked glycans or sialic acids on their own did not remove protection; only removing both N- and O-linked glycans did.
In contrast, immunization with EXCT4-mgG2(-N) (n = 8), EXCT4-mgG-2(-O) (n = 8) or EXCT4-mgG-2(-SA) (n = 8), all conferred protection against HSV-2 WT and the mice showed similar disease score as mice immunized with EXCT4-mgG-2
- The authors report that immunization with recombinant mgG-2 produced humoral and Th1-polarized CD4 T-cell responses alongside protection against genital challenge.
immunization with recombinant mgG-2 elicited strong humoral and Th1-polarized CD4 + T-cell responses and conferred protection against genital HSV-2 challenge
- After peptide-pool restimulation, splenocytes from mice given the glycosylated antigen expressed more IFN-gamma, IL-2 and TNF-alpha than those from mice given the deglycosylated antigen (with the intact antigen, only IL-2 differed significantly).
interferon gamma (IFN-γ), interleukin 2 (IL-2) and tumour necrosis factor alpha (TNF-α) were significantly more expressed in splenocytes from EXCT4-mgG-2-immunized mice compared to those from EXCT4-mgG-2(−N − O)-immunized mice
- Most mice infected with the mgG-2-negative virus survived, and the authors conclude the mutant has a greatly reduced capacity to cause genital and neurological disease.
After infection with HSV-2 ΔmgG-2 , 25 of 29 (86%) mice survived.
- Of 70 possible O-linked glycosylation sites on the recombinant antigen, 12 were found to carry glycan structures.
Of the 70 possible sites (Ser/Thr) for O-linked glycosylation, 12 were found to carry glycan structures
- The antigen was produced recombinantly in CHO-K1 cells and its glycan profile was mapped by liquid chromatography tandem mass spectrometry.
we produced a recombinant truncated mgG-2 (EXCT4-mgG-2) in Chinese Hamster Ovary (CHO-K1) cells
- The infection experiments used wild-type HSV-2 strain 333, an mgG-2-negative mutant and a rescued strain, across two mouse strains.
we used HSV-2 wild type strain 333 (HSV-2 WT , Fig 1A ), an mgG-2 negative mutant (HSV-2 ΔmgG-2, ( Fig 1B ), and a rescued HSV-2 strain in which the mgG-2 gene was reintroduced (HSV-2 rescue ) in a genital infection model across two mouse strains.
- The authors state that animal vaccine models have so far not predicted outcomes in clinical studies.
We conclude that none of the vaccination animal models have so far predicted the outcome in clinical studies.
- The authors note that results after vaccination in mice and guinea pigs have only partly translated into clinical trials.
The major challenge has been that promising results after vaccination in mice and guinea pigs has only in part been translated and replicated in clinical trials.
- Viral load was not measured in tissues outside those on the described intravaginal infection route, so wider dissemination could not be confirmed.
However, this cannot be confirmed, as viral load was not assessed in tissues outside those relevant to the natural course of intravaginal inoculation described by Parr and Parr [ 39 ].
- The authors present their results as a rationale for targeting glycosylated mgG-2 in future prophylactic and therapeutic HSV-2 vaccine development.
provide a strong rationale for targeting glycosylated mgG-2 in the development of both prophylactic and therapeutic vaccines against HSV-2
- The paper notes that earlier prophylactic candidates based on HSV-2 gB-2 and/or gD-2 reached phase III trials and did not prevent HSV-2 infection.
Two prophylactic vaccine candidates, based on HSV-2 envelope glycoprotein gB-2 and/or gD-2, have reached phase III clinical trials but failed to prevent HSV-2 infection