Immunogenicity and Therapeutic Efficacy of a Sendai-Virus-Vectored HSV-2 Vaccine in Mouse and Guinea Pig Models
Stephen Jennings
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this manuscript, Ren et al. describe a combinatorial vaccination strategy designed to induce robust humoral and cellular immune responses. The vaccine is based on Sendai virus (SeV), but how the vaccine was constructed is not mentioned. The authors optimized the vaccination dose, timing and combination of the two vectors and showed that vaccination did indeed induce some neutralizing antibodies against gD and ICP27-specific CD8 responses. Furthermore, they show that this strategy could reduce the frequency of HSV-2 recurrence and disease severity in latently infected guinea pigs. Although the beneficial effects in animal models are encouraging, the authors should compare the immune responses between the vaccinated and control groups to show that the therapeutic effects are due to vaccine-induced anti-HSV-2 immune responses.
1. The rationale for selecting ICP27 and gD for the anti-HSV-2 vaccine is not clear.
2. The construction of the SeV vector is not described.
3. The legend of Figure 1 is poorly written and misleading.
4. Statistical analysis is needed for Figures 6 and 7.
5. In the guinea pig model, the authors should compare the neutralizing antibody titers and HSV-2-specific CD8 responses between the vaccinated and control groups.
Comments on the Quality of English LanguageThe manuscript is not well written and requires extensive language editing.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe field of HSV-2 virus vaccination should be properly described as the prior finding might change your explanations and data analysis. Your paper has missed out just about most significant publications as listed below. Please see if you can rewrite your introduction with proper recognition to prior work and then reanalyze your data based on any previous data along with an explanation of the outcome analysis.
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Comments on the Quality of English LanguageMinor editing will help but it is not an issue
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript by Ren et al. describes the construction and in-vivo testing of an HSV-2 therapeutic vaccine. Their approach is based on the expression of HSV-2 gD and ICP27 in the Sendai virus replication-defective vectors. The resulting recombinant viruses were tested in mice to optimize dosage and regimen and in guinea pigs to assess their therapeutic efficacy. Overall the data suggest that the treatment regimen resulted in some reduction of severity of recurrent lesions, and duration and frequency of recurrences as compared to negative control (PBS). The study is not really novel (both gD and ICP27 were previously explored as components of subunit vaccines), however, it provides an incremental improvement in understanding of the topic. The results seem to be straightforward, but their presentation and description lack clarity, logic, and purpose. The specific comments are listed below:
Line 99 - PFU is plaque-forming units (not particle forming units)
Line 101 - indicate the strain of the mice used (I know it is indicated in other places, but this is the correct place to describe it).
Line 112 - what volume was injected i.m.?
Table 1 is very chaotic and confusing, different treatment groups need to be spelled out and properly described
Results 3.1 - The justification for using 10^8 CIU doesn’t make much sense. The 10-fold difference in dose will not compensate for the ~2000-fold difference in body weight between mice and humans but may be quite significant from the safety standpoint.
Line 383 - for the simultaneous vaccination, did the authors use 10^8 CIU of each virus or combined (that is 10^4 of each virus)?
Results 3.2 - the study is missing an important control - SeV -F alone, how do the authors measure the contribution of the vector to the observed effects?
Results 3.2 - why no immunology work was performed in guinea pigs? How do the authors know that the observed effects are the result of HSV antigen expression and not something else? With this experimental design, the correlative effects are not established.
The discussion reads as an introduction and doesn’t really “discuss” the data. The discussion needs to be re-written to discuss the data from this study in the context of knowledge available in the field.
For all figures - the figure legends poorly describe the context of the figure leaving readers guessing what they are looking at.
Comments on the Quality of English Language
Language: multiple typos, inconsistencies, and grammatical errors throughout the whole manuscript. While I realize that the authors are not native English speakers and appreciate their effort, the manuscript needs to be reviewed/edited by a professional editor to improve clarity and make it more readable.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsThe manuscript describes the evaluation of Sendai virus-based recombinants expressing HSV-2 gD and HSV-2 ICP27 as the basis for a protective vaccine against genital HSV-2 reactivated infection. The immunological studies in the BALB/c mouse model are sound and well presented, while the protective studies in the guinea pig model are suggestive of efficacy. However, there are some issues with the study that diminish overall enthusiasm.
The authors state that HSV-2 gD and HSV-2 ICP27 were chosen to induce humoral and cellular immunity, respectively, in BALB/c mice. However, there is no explicit explanation why these viral proteins were chosen. While it is well known that gD induces neutralizing antibodies, it should be stated what role ICP27 plays in inducing CD4 or CD8 T cell responses.
The authors present strong evidence of an effective HSV-2-specific antibody response and T cell response following immunization with the recombinant gD- and ICP27-expressing Sendai virus vectors. The analysis of the neutralizing antibody titers and the cytokine profiles induced by both CD4 and CD8 T cell subpopulations indicate the validity of the immunization protocol in BALB/c mice in the induction of an immune response. However, it is not demonstrated, in the mouse system, that such an immune response is protective. This would have strengthened the findings of the manuscript.
For the measurement of protection, the authors switch to a guinea pig model. The choice of the guinea pig model, in which latent HSV-2 reactivates and induces secondary lesions, is valid to the study. However, the authors have not shown that the recombinant Sendai virus vectors induce the same immune response in the guinea pig model. While it is clear that both gD and ICP27 induce B and T cell responses, respectively, in BALB/c mice, it is not clear that the same is true for guinea pigs. While it is likely that gD will serve as a target for B cells and the induction of neutralizing antibodies, it is not clear that ICP27 contains epitopes that can bind to guinea pig MHC and induce an appropriate T cell response. It would have strengthened the study to include a group of animals that received only the gD vaccine alone to determine if the ICP27-expressing recombinant played any role in the guinea pig model.
Overall, there are some strong aspects to the study, but there is a disconnect between the immunogenic studies in the mouse and the protective studies in the guinea pig. Reconciling these issues would strengthen the manuscript.
Comments on the Quality of English Language
The quality of the language is excellent. There are a few misspellings to be addressed in editing.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have not adequately substantiated that the observed protective effects in the guinea pig model are a direct result of the vaccine-induced immunological responses, as seen in the mouse model. To enhance the robustness of their findings, it is imperative that the authors consider demonstrating the vaccine's efficacy in a mouse model of HSV-2 infection. This step would provide a critical link between the vaccine's immunological responses and its protective effects, thereby strengthening the overall scientific rigor of their investigation
Comments on the Quality of English LanguageMinor editing will help but it is not an issue.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsI had provided a list of most relevant papers that must be cited and their findings compared with the conclusions drawn in this research; none of the references I suggested were included in the revision; please explain why is the this inclusion not acceptable.
Comments on the Quality of English LanguageSubstantial improvement required;
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 3
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have addressed my concerns.
Reviewer 2 Report
Comments and Suggestions for AuthorsThe authors have added relevant citations, even though more are needed but sufficient.
Comments on the Quality of English LanguageAlso, the writing style is more informal and not suitable for research publications. Authors can benefit from the editing services of MDPI or another service.
