State of the Field: Cytotoxic Immune Cell Responses in C. neoformans and C. deneoformans Infection

Round 1

Reviewer 1 Report

Cryptococcosis is a systemic fungal infection caused by Cryptococcus neoformans. Severe infection occurs mainly in immunocompromised individuals, as C. neoformans can cause fatal disease, either by new exposure or by reactivation of a previously acquired latent infection. On the other hand, in immunocompetent patients, cryptococcal infection is usually confined to the lungs.

An example of the severity of cryptococcal infection is meningitis, which is characterized as a serious clinical disease that can manifest in immunocompromised individuals due to AIDS or use of immunosuppressive drugs.

In this excellent review submitted by Elizabeth C. Okafor and Kirsten Nielsen, the authors discuss the immunological aspects in the course of infection. The authors elegantly report on the dysfunction of CD4+ T cells and associated cytokine signaling pathways, the optimization of phagocytic cell function against fungal cells, and the identification of robust antigens for vaccine development.

It is also important to emphasize that there is a growing body of literature on cytotoxic cells, specifically CD8+ T cells, Natural Killer (NK) cells, gamma/delta T cells, NK T cells, and cytotoxic CD4+ T cells, and their role in the innate and adaptive immune response during infection by C. neoformans and C. deneoformans.

Among the points that were very well discussed in this review, it is evident the information on relevant information on data collected from studies in mice and humans on the function and phenotype of cytotoxic cells, different results presented in the literature on cellular responses in mouse models and human infection were presented and discussed, it was possible to identify relevant data innovative immunological tools can improve the study of cytotoxic cells and their potential immunomodulation during cryptococcosis.

In short, the review is interesting and very pleasant to read.

However, since it is a review on cryptococcosis, it would be interesting to add information on the main immunomodulation mechanism of this microorganism: capsular polysaccharides.

I believe that citations about polysaccharides at the beginning of the review are necessary. I think it is unacceptable to introduce Cryptococcus and neglect the capsule.

* I SUGGEST THE AUTHORS COMMENT THAT THE FUNGUS IS CAPSULED AND HAS TWO POLYSACCHARIDE COMPONENTS, WHICH ARE GLUCURONOXYLOMANNAN (GXM) AND GLUCURONOXYLOMANNOGALACTAN (GXMGAL), AND TO COMMENT THAT THESE COMPONENTS HAVE IMPORTANT IMMUNOMODULATORY ACTIVITIES.

Below are some references that can be used:

1. Decote-Ricardo D, Larocque-De-Freitas IF, Rocha JDB, Nascimento DO, Nunes MP, Morrot A, et al. Immunomodulatory Role of Capsular Polysaccharides Constituents of Cryptococcus neoformans. Frontiers in Medicine. 2019;6.

2. Larocque-De-Freitas IF, Da Silva-Junior EB, Gemieski LP, Da Silva Dias Lima B, Diniz-Lima I, De Carvalho Vivarini A, et al. Inhibition of Microbicidal Activity of Canine Macrophages DH82 Cell Line by Capsular Polysaccharides from Cryptococcus neoformans. Journal of Fungi. 2024;10(5):339.

3. Villena SN, Pinheiro RO, Pinheiro CS, Nunes MP, Takiya CM, DosReis GA, et al. Capsular polysaccharides galactoxylomannan and glucuronoxylomannan from Cryptococcus neoformans induce macrophage apoptosis mediated by Fas ligand. Cell Microbiol. 2008;10(6):1274-85.

4. Monari C, Paganelli F, Bistoni F, Kozel TR, Vecchiarelli A. Capsular polysaccharide induction of apoptosis by intrinsic and extrinsic mechanisms. Cell Microbiol. 2008;10(10):2129-37.

5. Monari C, Pericolini E, Bistoni G, Casadevall A, Kozel TR, Vecchiarelli A. Cryptococcus neoformans capsular glucuronoxylomannan induces expression of fas ligand in macrophages. J Immunol. 005;174(6):3461 6. Larocque-De-Freitas IF, Rocha JDB, Nunes MP, Oliveira PAV, Nascimento DDO, Freire-De-Lima L, et al. Involvement of the capsular GalXM-induced IL-17 cytokine in the control of Cryptococcus neoformans infection. Scientific Reports. 2018;8(1).

6. Larocque-De-Freitas IF, Rocha JDB, Nunes MP, Oliveira PAV, Nascimento DDO, Freire-De-Lima L, et al. Involvement of the capsular GalXM-induced IL-17 cytokine in the control of Cryptococcus neoformans infection. Scientific Reports. 2018;8(1). 

Cryptococcosis is a systemic fungal infection caused by Cryptococcus neoformans. Severe infection occurs mainly in immunocompromised individuals, as C. neoformans can cause fatal disease, either by new exposure or by reactivation of a previously acquired latent infection. On the other hand, in immunocompetent patients, cryptococcal infection is usually confined to the lungs.

An example of the severity of cryptococcal infection is meningitis, which is characterized as a serious clinical disease that can manifest in immunocompromised individuals due to AIDS or use of immunosuppressive drugs.

In this excellent review submitted by Elizabeth C. Okafor and Kirsten Nielsen, the authors discuss the immunological aspects in the course of infection. The authors elegantly report on the dysfunction of CD4+ T cells and associated cytokine signaling pathways, the optimization of phagocytic cell function against fungal cells, and the identification of robust antigens for vaccine development.

It is also important to emphasize that there is a growing body of literature on cytotoxic cells, specifically CD8+ T cells, Natural Killer (NK) cells, gamma/delta T cells, NK T cells, and cytotoxic CD4+ T cells, and their role in the innate and adaptive immune response during infection by C. neoformans and C. deneoformans.

Among the points that were very well discussed in this review, it is evident the information on relevant information on data collected from studies in mice and humans on the function and phenotype of cytotoxic cells, different results presented in the literature on cellular responses in mouse models and human infection were presented and discussed, it was possible to identify relevant data innovative immunological tools can improve the study of cytotoxic cells and their potential immunomodulation during cryptococcosis.

In short, the review is interesting and very pleasant to read.

However, since it is a review on cryptococcosis, it would be interesting to add information on the main immunomodulation mechanism of this microorganism: capsular polysaccharides.

I believe that citations about polysaccharides at the beginning of the review are necessary. I think it is unacceptable to introduce Cryptococcus and neglect the capsule.

* I SUGGEST THE AUTHORS COMMENT THAT THE FUNGUS IS CAPSULED AND HAS TWO POLYSACCHARIDE COMPONENTS, WHICH ARE GLUCURONOXYLOMANNAN (GXM) AND GLUCURONOXYLOMANNOGALACTAN (GXMGAL), AND TO COMMENT THAT THESE COMPONENTS HAVE IMPORTANT IMMUNOMODULATORY ACTIVITIES.

Below are some references that can be used:

1. Decote-Ricardo D, Larocque-De-Freitas IF, Rocha JDB, Nascimento DO, Nunes MP, Morrot A, et al. Immunomodulatory Role of Capsular Polysaccharides Constituents of Cryptococcus neoformans. Frontiers in Medicine. 2019;6.

2. Larocque-De-Freitas IF, Da Silva-Junior EB, Gemieski LP, Da Silva Dias Lima B, Diniz-Lima I, De Carvalho Vivarini A, et al. Inhibition of Microbicidal Activity of Canine Macrophages DH82 Cell Line by Capsular Polysaccharides from Cryptococcus neoformans. Journal of Fungi. 2024;10(5):339.

3. Villena SN, Pinheiro RO, Pinheiro CS, Nunes MP, Takiya CM, DosReis GA, et al. Capsular polysaccharides galactoxylomannan and glucuronoxylomannan from Cryptococcus neoformans induce macrophage apoptosis mediated by Fas ligand. Cell Microbiol. 2008;10(6):1274-85.

4. Monari C, Paganelli F, Bistoni F, Kozel TR, Vecchiarelli A. Capsular polysaccharide induction of apoptosis by intrinsic and extrinsic mechanisms. Cell Microbiol. 2008;10(10):2129-37.

5. Monari C, Pericolini E, Bistoni G, Casadevall A, Kozel TR, Vecchiarelli A. Cryptococcus neoformans capsular glucuronoxylomannan induces expression of fas ligand in macrophages. J Immunol. 005;174(6):3461 6. Larocque-De-Freitas IF, Rocha JDB, Nunes MP, Oliveira PAV, Nascimento DDO, Freire-De-Lima L, et al. Involvement of the capsular GalXM-induced IL-17 cytokine in the control of Cryptococcus neoformans infection. Scientific Reports. 2018;8(1).

6. Larocque-De-Freitas IF, Rocha JDB, Nunes MP, Oliveira PAV, Nascimento DDO, Freire-De-Lima L, et al. Involvement of the capsular GalXM-induced IL-17 cytokine in the control of Cryptococcus neoformans infection. Scientific Reports. 2018;8(1). 

 

Author Response

Please see the attachment.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Cryptococcosis is a disease of considerable significance, attracting growing attention within the scientific community. Nonetheless, substantial gaps persist in our understanding of the immune response to this pathogen, particularly regarding the roles of CD8+ T lymphocytes and NK cells. Thus, a comprehensive review examining the involvement of these cells in both human and murine models of cryptococcosis would be highly valuable. 

I have few comments to make.

The beginning of the review addresses the issue concerning C. neoformans. However, towards the end of the introduction, it is stated that pulmonary and CNS diseases caused by C. deneoformans will also be discussed. Therefore, it would be pertinent to provide a brief description of the current nomenclature.

Although the undeniable importance of CD8+ T cells was described in item 2, and it was noted that the presence of CD4+ T cells is not required for the trafficking of CD8+ T cells to the lungs, for example, I believe it is important to highlight the role of CD4+ T cells in the immune response to Cryptococcus. These articles, for instance, demonstrate this.: Huffnagle GB, Yates JL, Lipscomb MF. J Exp Med. 1991 Apr 1;173(4):793-800. doi: 10.1084/jem.173.4.793 and Ma LL, Spurrell JC, Wang JF, Neely GG, Epelman S, Krensky AM, Mody CH. J Immunol. 2002 Nov 15;169(10):5787-95. doi: 10.4049/jimmunol.169.10.5787. 

 

The figures distinguish between detection, signaling, and response. However, I am not convinced of the effectiveness of this separation, as receptors that recognize fungal structures are important signalers and inducers of effector responses.

In line 129 ("CD8+ T-cell anti-cryptococcal effects while IL-2R expression increases upon coculture"), it is not clear which coculture is being referenced.

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

This review discusses the role of cytotoxic immune cells in the host defense to C. neoformans. Overall, the review is written well and nicely summarizes what is known in the field and the gaps in knowledge that need to be studied.

The authors have done a nice job on this review. I only have a few comments.

 

1.       There are some minor grammar mistakes that should be fixed, but overall, it reads well.

2.       Can you add a summary figure for the lesser studied cytotoxic cells (gamma-delta T cells, NK T cells, and cytotoxic CD4 T cells) that is similar to Figures 1 and 2?

There are minor grammar issues on lines 102,134-135, 142, and 322.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf