V2-Specific Antibodies in HIV-1 Vaccine Research and Natural Infection: Controllers or Surrogate Markers
Round 1
Reviewer 1 Report
So far, only the RV144 vaccine trial showed the modest protection efficacy which might correlates with the elevated levels of V2-specific antibodies. A number of human and non-human primate vaccine studies have investigated the possible role of V2-specific antibodies to vaccine efficacy. In addition, diverse anti-V2 monoclonal antibodies were isolated and their distinct epitope regions characterized. However, the whole picture is not clear yet. In this review article, Duerr R and Gorny KM summarized the published studies on V2-specific antibody responses in HIV-1 vaccination and natural infection, and discussed their perspective on HIV vaccine research. The topic of this review is important to the related field, but the authors need to address the following concerns before it is published:
1) There are a number of potent and broad bnAbs been discovered in the last decade, the author should include a section describing the similarity and difference of anti-V2 bnAbs and other ones.
2) “The impact of blocking the gp120-α4β7 interaction by anti-V2 or anti-α4β7 Abs on HIV disease outcome is controversially discussed”, this needs further explanation.
3) It is difficult to see the Figure 2. Please use bigger fonts for the figure.
4) The targets of V2p, V2i, V2q and V2qt were repeatedly described several times in the article. Please remove the redundant sentences or make it concise.
5) The sentence “Non-neutralizing anti-gp41 mAb F240 did not reduce the number of infected animals significantly but achieved protection in two of five passively immunized animals” is controversial, as the protection of the two animals might not be the result of F240 treatment.
6) Section “2.3. High sequence diversity in V1V2 and clade-specific differences in antigenicity and immunogenicity” should be moved to before Section “2.2. Antiviral functions differ according to V2 antibody class and epitope region”.
Author Response
Point 1: There are a number of potent and broad bnAbs been discovered in the last decade, the author should include a section describing the similarity and difference of anti-V2 bnAbs and other ones.
Response 1: We acknowledged the reviewer's suggestion and included section 2.3.2, which focuses on anti-V2 bnAbs and their characteristic features in comparison to other bnAb classes.
Point 2: “The impact of blocking the gp120-α4β7 interaction by anti-V2 or anti-α4β7 Abs on HIV disease outcome is controversially discussed”, this needs further explanation.
Response 2: We agree with the reviewer. We deleted the sentence and now refer to chapter 5, where the impact of blocking the gp120-α4β7 interaction by anti-V2 or anti-α4β7 is explained in more detail. In chapter 5, we also added a sentence about a recent study on the synergistic effects of α4β7-inhibition and suboptimal doses of bnAb VRC01 (lines 575-577).
Point 3: It is difficult to see the Figure 2. Please use bigger fonts for the figure.
Response 3: According to the reviewer’s request, we increased the font sizes in Figure 2. In addition, we used bigger fonts for small labels in Figure 3 and we removed the term “native” in conjunction with the closed SOSIP structure in Figure 1, based on growing evidence that the SOSIP Env structure does not fully resemble the native Env conformation.
Point 4: The targets of V2p, V2i, V2q and V2qt were repeatedly described several times in the article. Please remove the redundant sentences or make it concise.
Response 4: As suggested by the reviewer, we removed redundant passages of text to define V2 antibody classes, i.e., we removed V2 Ab definitions in the figure legends of Figures 2 and 3, replaced only by a brief explanation of abbreviations used for V2 epitopes at the end of Figure legend 2.
Point 5: The sentence “Non-neutralizing anti-gp41 mAb F240 did not reduce the number of infected animals significantly but achieved protection in two of five passively immunized animals” is controversial, as the protection of the two animals might not be the result of F240 treatment.
Response 5: We changed the wording of the sentence to make it better understandable. It now says: “Non-neutralizing anti-gp41 mAb F240 achieved protection in two of five passively immunized animals, thus yielding a limited but overall non-significant reduction of infected animals” (lines 427-429).
Point 6: Section “2.3. High sequence diversity in V1V2 and clade-specific differences in antigenicity and immunogenicity” should be moved to before Section “2.2. Antiviral functions differ according to V2 antibody class and epitope region”.
Response 6: We thank the reviewer for the suggestion, which makes good sense. We changed the order of appearance of sections 2.2 and 2.3.
Reviewer 2 Report
Critique: Duerr and Gorny, Pacemaker or surrogate: V2-specific antibodies in HIV-1 vaccine research and natural infection
Summary: This review covers an important topic in the HIV vaccine field. The significance of V2-specific antibodies became a major focus following the RV144 trial, where they were found to correlate with protection. This finding stimulated many additional studies, including NHP studies designed to directly evaluate protective efficacy of non-neutralizing, loop-directed antibodies. To many in the field this area remains confusing, because the follow-up studies are not entirely clear. Thus the importance of V2-specific non-neutralizing antibodies remains controversial. The authors here provide a comprehensive review of the major findings in the field. The presentation is relatively logical and is accompanied by useful tables and figures. There are however redundancies in the review that limit readability, and some of the grammar could be improved to facilitate readability and provide clarity. Sections dealing with ADCC can be consolidated, and efforts to avoid redundancies throughout the text would improve the document. Some specific corrections, mostly grammatical, and suggestions for improvement are provided below:
1. The title is an odd one. I am not sure what the term “pacemaker” refers to in the title. I suggest using a different term unless there is meaning to this that can be clarified.
2. Abstract: For the sentence beginning on line 17 and the following sentence, suggest: “After RV144, a plethora of research studies were performed using different model systems, immunogens, protocols, and challenge viruses. These diverse studies failed to provide a clear picture regarding the contribution of V2 antibodies to vaccine efficacy.”
3. Line 68: “Abs that are non-neutralizing or only weakly neutralize Tier 1 viruses, broadly…”
4. Line 71: “are currently investigated” should read “are currently under investigation”
5. Line 75: the sentence reads poorly, suggest something simpler such as “their potential contribution to vaccine efficacy versus the possibility that they merely serve as surrogate markers for other immune responses.”
6. Line 131 “experiment” should be “experiments”
7. The discussion of a4b7 on lines 169-173 is brief but confusing, and should be eliminated. The role of a4b7 is discussed in its own section later in the review.
8. Sentence beginning on line 218 doesn’t make sense- “Differences in glycosylation patterns…were also discussed”. The authors should state what differences in glycosylation pattern were said to convey in reference 81, not just state that they were discussed.
9. Please eliminate redundancy throughout the text. For example, the fact that RV144 achieved 31.2% efficacy is repeatedly stated. The ability of V2-specific antibodies to mediate ADCC is present in numerous sections of the text and could be consolidated.
10. Line 295 does not connect with line 296; some part of the sentence appears to be missing.
11. Line 364 “SHI” should be “SHIV”
12. Line 378- the sentence beginning “It applies explicitly…” is very unclear. I think the authors mean that SHIVs rather than SIVse must be used as challenge viruses when evaluating the potential of a candidate HIV vaccines to generate protective antibody responses in NHPs. This needs to be rewritten.
13. Line 409- the study from the Franchini laboratory comparing an RV144-like regimen with gp120 adjuvanted either with alum or MF59 is briefly mentioned, and the connection to RV144 is not made. This study deserves more highlighting, and the reader should be made aware of the potential problem with the altered adjuvant now being employed in HVTN 702. This study is mentioned elsewhere, but there should be a connection made.
14. Line 473: the statement “where HIV and SIV pathogenesis essentially takes place” is a vast overstatement and should be revised. The GI tract is clearly important in pathogenesis, but pathogenesis occurs throughout lymphoid tissues and elsewhere in the body, not in the GI tract alone.
15. Line 438: the sentence does not make sense as written, as the two halves of the sentence are basically distinct statements.
Author Response
Point 1: The title is an odd one. I am not sure what the term “pacemaker” refers to in the title. I suggest using a different term unless there is meaning to this that can be clarified. Response 1: We acknowledged the reviewer’s suggestion and changed the title to “Controller or surrogate marker…” Both terms should illustrate the controversies about the suggested roles of V2 antibodies in recent vaccine protection experiments and studies of natural infection.
Point 2: Abstract: For the sentence beginning on line 17 and the following sentence, suggest: “After RV144, a plethora of research studies were performed using different model systems, immunogens, protocols, and challenge viruses. These diverse studies failed to provide a clear picture regarding the contribution of V2 antibodies to vaccine efficacy.”
Response 2: We appreciate the helpful suggestion. Both sentences were revised accordingly.
Point 3: The Line 68: “Abs that are non-neutralizing or only weakly neutralize Tier 1 viruses, broadly…”
Response 3: The sentence was edited as suggested.
Point 4: Line 71: “are currently investigated” should read “are currently under investigation”
Response 4: We thank the reviewer for the correction, which was adopted accordingly.
Point 5: Line 75: the sentence reads poorly, suggest something simpler such as “their potential contribution to vaccine efficacy versus the possibility that they merely serve as surrogate markers for other immune responses.”
Response 5: We acknowledged the useful suggestion of the reviewer and changed the sentence as advised.
Point 6: Line 131 “experiment” should be “experiments”
Response 6: The typo was corrected.
Point 7: The discussion of a4b7 on lines 169-173 is brief but confusing, and should be eliminated. The role of a4b7 is discussed in its own section later in the review.
Response 7: We agree with the reviewer and eliminated these lines, only leaving a short cross-reference to chapter 5.
Point 8: Sentence beginning on line 218 doesn’t make sense- “Differences in glycosylation patterns…were also discussed”. The authors should state what differences in glycosylation pattern were said to convey in reference 81, not just state that they were discussed.
Response 8: We agree with the reviewer and modified the sentence as shown below. Also we added References from Cao et al., 2017 and Andrabi et al., 2019 who compared SIV and HIV Env structures and N-Glycosylations. They identified an overall comparable Env architecture but subtle differences in V1V2 glycans between HIV and SIV strains. Furthermore, we included References from Yen et al., 2014 and Cole et al., 2004 who performed mutational analysis with SIV Env.
In lines 183-188 we now say: “Differences in glycan content and composition (complex/high-mannose glycans) and the capacity of Env glycoproteins to stimulate/modulate the expression of genes involved in innate or adaptive immune responses in the context of different vectors and adjuvants may have contributed to the observed dissimilarities in immunogenicity between SIV and HIV-1 [38,63,65-70]. Of interest, removal of glycans in V1 of SIV gp120 can redirect humoral immune responses to V3 [69].”
Point 9: Please eliminate redundancy throughout the text. For example, the fact that RV144 achieved 31.2% efficacy is repeatedly stated. The ability of V2-specific antibodies to mediate ADCC is present in numerous sections of the text and could be consolidated.
Response 9: We acknowledged the reviewer’s request and deleted the statement about the “31.2% vaccine efficacy of RV144” in the Introduction (line 37) and deleted “modest efficacy” in Table 2. Also, in lines 359-360, we deleted the statement that ADCC only correlated with reduced risk of infection in participants with low Env-specific plasma IgA levels.” Some further minor edits were made throughout the manuscript to make it more concise and to include recently published literature.
Point 10: Line 295 does not connect with line 296; some part of the sentence appears to be missing.
Response 10: We agree that the second sentence was not adequately connected with the prior one. In lines 350-354, it now says: “The qualitatively different V2 Ab immune response in RV144 compared with VAX003 might have been due to the usage of a gp160 DNA prime in a canarypox vector, the more immunogenic CRF01_AE A244 and TH023 antigens, and a better sequence match between the immunogens and the regionally prevalent challenge viruses in RV144.”
Point 11: Line 364 “SHI” should be “SHIV”
Response 11: The typo was corrected.
Point 12: Line 378- the sentence beginning “It applies explicitly…” is very unclear. I think the authors mean that SHIVs rather than SIVse must be used as challenge viruses when evaluating the potential of a candidate HIV vaccines to generate protective antibody responses in NHPs. This needs to be rewritten.
Response 12: We agree with the reviewer and revised the sentence as follows: “Experiments using SHIV as a challenging virus are the closest model for evaluating the potential of candidate HIV vaccines to generate protective antibody responses in NHPs.” (lines 461-463)
Point 13: Line 409- the study from the Franchini laboratory comparing an RV144-like regimen with gp120 adjuvanted either with alum or MF59 is briefly mentioned, and the connection to RV144 is not made. This study deserves more highlighting, and the reader should be made aware of the potential problem with the altered adjuvant now being employed in HVTN 702. This study is mentioned elsewhere, but there should be a connection made.
Response 13: We thank the reviewer for stressing this important point. We extended the part describing the mentioned Franchini study in section 4.2 to lines 501-516. Also, a connection to this section was made in section 3.3, lines 383-386.
Point 14: Line 473: the statement “where HIV and SIV pathogenesis essentially takes place” is a vast overstatement and should be revised. The GI tract is clearly important in pathogenesis, but pathogenesis occurs throughout lymphoid tissues and elsewhere in the body, not in the GI tract alone.
Response 14: We fully agree. We removed the overstatement and changed to: “which is one of the primary sites of HIV and SIV pathogenesis.”
Point 15: Line 438: the sentence does not make sense as written, as the two halves of the sentence are basically distinct statements.
Response 15: We appreciate the reviewer’s thorough revision of the manuscript. The term “thus” was changed into “and”. Lines 542-544 now say: “Importantly, α4β7 serves as an attachment factor for HIV and not as an entry receptor, and α4β7 blocking does not neutralize HIV-1 infection.”
Reviewer 3 Report
In the manuscript entitled “Pacemaker or surrogate: V2-specific antibodies in HIV-1 vaccine research and natural infection”, the authors made a comprehensive review on the roles of V2-specific antibodies in previous HIV vaccine researches and natural infections, which provides very valuable insights for the HIV vaccine design in future. The authors have thoroughly discussed all the important HIV vaccine studies conducted on human as well as NHP, and the role(s) of V2-specific antibodies played in the protection effects, if any, observed in these studies. The authors also highlighted the high level of variations in the V1V2 region of HIV envelop protein, which may have contributed to the V2-specific antibodies’ performance among these HIV vaccine studies.
In general, this is a very well-written, comprehensive review about V2-specific antibodies and HIV vaccine development.
Minor concern:
1. Page 15, Section 4.1: Here the authors only discussed the studies with non-neutralizing antibodies. Is there any study with broadly neutralizing antibodies (bnAbs) on NHPs, and what’s their protecting effects?
Author Response
Point 1: Page 15, Section 4.1: Here the authors only discussed the studies with non-neutralizing antibodies. Is there any study with broadly neutralizing antibodies (bnAbs) on NHPs, and what’s their protecting effects?
Response 1: The reviewer raised a good point. Accordingly, section 4.1 now includes information on passive NHP vaccinations with bnAbs targeting V2 and other Env epitopes. Also, we included a separate section (section 2.3.2) that describes the characteristics of anti-V2 bnAbs in more detail.
