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Gammaherpesvirus Co-infection with Malaria Suppresses Anti-parasitic Humoral Immunity.

Matar CG, Anthony NR, O'Flaherty BM, Jacobs NT, Priyamvada L, Engwerda CR, Speck SH, Lamb TJ - PLoS Pathog. (2015)

Bottom Line: Importantly, this resulted in the transformation of a non-lethal P. yoelii XNL infection into a lethal one; an outcome that is correlated with a defect in the maintenance of germinal center B cells and T follicular helper (Tfh) cells in the spleen.Notably, co-infection with an M2- mutant MHV68 eliminates lethality of P. yoelii XNL.Collectively, our data demonstrates that an acute gammaherpesvirus infection can negatively impact the development of an anti-malarial immune response.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, United States of America; Microbiology and Molecular Genetics Graduate Program, Laney Graduate School, Emory University, Atlanta, Georgia, United States of America.

ABSTRACT
Immunity to non-cerebral severe malaria is estimated to occur within 1-2 infections in areas of endemic transmission for Plasmodium falciparum. Yet, nearly 20% of infected children die annually as a result of severe malaria. Multiple risk factors are postulated to exacerbate malarial disease, one being co-infections with other pathogens. Children living in Sub-Saharan Africa are seropositive for Epstein Barr Virus (EBV) by the age of 6 months. This timing overlaps with the waning of protective maternal antibodies and susceptibility to primary Plasmodium infection. However, the impact of acute EBV infection on the generation of anti-malarial immunity is unknown. Using well established mouse models of infection, we show here that acute, but not latent murine gammaherpesvirus 68 (MHV68) infection suppresses the anti-malarial humoral response to a secondary malaria infection. Importantly, this resulted in the transformation of a non-lethal P. yoelii XNL infection into a lethal one; an outcome that is correlated with a defect in the maintenance of germinal center B cells and T follicular helper (Tfh) cells in the spleen. Furthermore, we have identified the MHV68 M2 protein as an important virus encoded protein that can: (i) suppress anti-MHV68 humoral responses during acute MHV68 infection; and (ii) plays a critical role in the observed suppression of anti-malarial humoral responses in the setting of co-infection. Notably, co-infection with an M2- mutant MHV68 eliminates lethality of P. yoelii XNL. Collectively, our data demonstrates that an acute gammaherpesvirus infection can negatively impact the development of an anti-malarial immune response. This suggests that acute infection with EBV should be investigated as a risk factor for non-cerebral severe malaria in young children living in areas endemic for Plasmodium transmission.

No MeSH data available.


Related in: MedlinePlus

The MHV68 M2 gene product is necessary for virus mediated humoral suppression and lethality during Plasmodium co-infection.(A) MHV68 specific IgG titers from serum of animals infected with the MR (M2.Marker Rescue) or M2.Stop (ST, M2-) viruses. Serum was collected and analyzed on days 7, 14 and 21 post infection with either virus (n = 10/ virus) (Day 21, MR vs. M2.Stop, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p<0.05). (B) P. yoelii XNL specific IgG response during P. yoelii XNL co-infection with either the M2.MR or M2.Stop virus. Serum was collected at day 20 post infection with P. yoelii XNL (WT + P. yoelii co-infected vs. P. yoelii, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p<0.05/ WT + P. yoelii co-infected vs. M2.Stop + P. yoelii, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p>0.05). (C) Survival curve during P. yoelii XNL co-infection with either the M2.MR or M2.Stop virus. Note: data representing P. yoelii XNL + MHV68 co-infection is the identical data set to that in Fig 1B. It was added in panel C for comparative purposes. (D) % parasitemia in the periphery during P. yoelii XNL, P. yoelii XNL +MR and P. yoelii XNL + M2.Stop infection.
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ppat.1004858.g006: The MHV68 M2 gene product is necessary for virus mediated humoral suppression and lethality during Plasmodium co-infection.(A) MHV68 specific IgG titers from serum of animals infected with the MR (M2.Marker Rescue) or M2.Stop (ST, M2-) viruses. Serum was collected and analyzed on days 7, 14 and 21 post infection with either virus (n = 10/ virus) (Day 21, MR vs. M2.Stop, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p<0.05). (B) P. yoelii XNL specific IgG response during P. yoelii XNL co-infection with either the M2.MR or M2.Stop virus. Serum was collected at day 20 post infection with P. yoelii XNL (WT + P. yoelii co-infected vs. P. yoelii, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p<0.05/ WT + P. yoelii co-infected vs. M2.Stop + P. yoelii, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p>0.05). (C) Survival curve during P. yoelii XNL co-infection with either the M2.MR or M2.Stop virus. Note: data representing P. yoelii XNL + MHV68 co-infection is the identical data set to that in Fig 1B. It was added in panel C for comparative purposes. (D) % parasitemia in the periphery during P. yoelii XNL, P. yoelii XNL +MR and P. yoelii XNL + M2.Stop infection.

Mentions: The data presented above clearly points to a suppressed humoral response as being a critical mediator of lethality during P. yoelii XNL co-infection with MHV68. As such, we hypothesized that if we could restore the parasite specific humoral response, we could rescue mice from lethality caused by an MHV68 and P. yoelii XNL co-infection. It has previously been shown that the M2 gene product of MHV68 can induce significant levels of IL-10 production from B cells and modulate the surface phenotype of infected B cells [32,33]. IL-10 is known to have multiple immunomodulatory roles, one of which is to negatively regulate T cell responses [34,35]. We hypothesized that one reason Tfh cells did not function correctly could be due to M2-induced suppression, a hypothesis supported by published work showing that in the absence of M2, mice are able to mount enhanced virus specific CD8+ T cell responses [33]. Given that the downstream effect of MHV68 induced immunosuppression was a result of impaired anti-malarial antibody responses, we initially asked whether levels of virus specific IgG responses were enhanced in the absence of M2 expression. To avoid a known defect in the establishment of splenic infection following intranasal inoculation of M2-deficient MHV68 mutants [36]we opted to infect mice with the same dose of virus (1000 PFU) as used in the previous experiments, but via the intraperitoneal route—a route and dose of virus which allow the M2-deficient mutant to efficiently infect the spleen [36]. As a proper control, the marker rescue virus (i.e, a recombinant MHV68 in which the genetic mutation introduced into the M2 mutant was restored to the wild type virus sequence) [37], was also administered via the IP route. Notably, we have extensively compared IN versus IP MHV68 co-infection with P. yoelii and found there to be no difference in outcome. M2.Stop (M2 virus; M2.St) infection in a C57BL/6 mouse induced a nearly 2-fold higher MHV68 specific IgG response as compared to infection with the marker rescue control virus (M2.MR; MR) (Fig 6A; day 21 post-infection Mann Whitney-U test p<0.05). It is important to note that day 21 post-MHV68 infection in this experiment corresponds to day 14 post-co-infection with P. yoelii XNL. The time point at which the virus specific humoral response is suppressed overlaps with the timing at which parasite specific IgG responses become severely compromised during co-infection (Fig 1C and 1E). This observation suggests that M2 may be mediating the virus-induced suppression of anti-malarial humoral immune responses.


Gammaherpesvirus Co-infection with Malaria Suppresses Anti-parasitic Humoral Immunity.

Matar CG, Anthony NR, O'Flaherty BM, Jacobs NT, Priyamvada L, Engwerda CR, Speck SH, Lamb TJ - PLoS Pathog. (2015)

The MHV68 M2 gene product is necessary for virus mediated humoral suppression and lethality during Plasmodium co-infection.(A) MHV68 specific IgG titers from serum of animals infected with the MR (M2.Marker Rescue) or M2.Stop (ST, M2-) viruses. Serum was collected and analyzed on days 7, 14 and 21 post infection with either virus (n = 10/ virus) (Day 21, MR vs. M2.Stop, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p<0.05). (B) P. yoelii XNL specific IgG response during P. yoelii XNL co-infection with either the M2.MR or M2.Stop virus. Serum was collected at day 20 post infection with P. yoelii XNL (WT + P. yoelii co-infected vs. P. yoelii, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p<0.05/ WT + P. yoelii co-infected vs. M2.Stop + P. yoelii, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p>0.05). (C) Survival curve during P. yoelii XNL co-infection with either the M2.MR or M2.Stop virus. Note: data representing P. yoelii XNL + MHV68 co-infection is the identical data set to that in Fig 1B. It was added in panel C for comparative purposes. (D) % parasitemia in the periphery during P. yoelii XNL, P. yoelii XNL +MR and P. yoelii XNL + M2.Stop infection.
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ppat.1004858.g006: The MHV68 M2 gene product is necessary for virus mediated humoral suppression and lethality during Plasmodium co-infection.(A) MHV68 specific IgG titers from serum of animals infected with the MR (M2.Marker Rescue) or M2.Stop (ST, M2-) viruses. Serum was collected and analyzed on days 7, 14 and 21 post infection with either virus (n = 10/ virus) (Day 21, MR vs. M2.Stop, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p<0.05). (B) P. yoelii XNL specific IgG response during P. yoelii XNL co-infection with either the M2.MR or M2.Stop virus. Serum was collected at day 20 post infection with P. yoelii XNL (WT + P. yoelii co-infected vs. P. yoelii, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p<0.05/ WT + P. yoelii co-infected vs. M2.Stop + P. yoelii, Kruskal Wallis p<0.05; Dunn’s pairwise comparison test p>0.05). (C) Survival curve during P. yoelii XNL co-infection with either the M2.MR or M2.Stop virus. Note: data representing P. yoelii XNL + MHV68 co-infection is the identical data set to that in Fig 1B. It was added in panel C for comparative purposes. (D) % parasitemia in the periphery during P. yoelii XNL, P. yoelii XNL +MR and P. yoelii XNL + M2.Stop infection.
Mentions: The data presented above clearly points to a suppressed humoral response as being a critical mediator of lethality during P. yoelii XNL co-infection with MHV68. As such, we hypothesized that if we could restore the parasite specific humoral response, we could rescue mice from lethality caused by an MHV68 and P. yoelii XNL co-infection. It has previously been shown that the M2 gene product of MHV68 can induce significant levels of IL-10 production from B cells and modulate the surface phenotype of infected B cells [32,33]. IL-10 is known to have multiple immunomodulatory roles, one of which is to negatively regulate T cell responses [34,35]. We hypothesized that one reason Tfh cells did not function correctly could be due to M2-induced suppression, a hypothesis supported by published work showing that in the absence of M2, mice are able to mount enhanced virus specific CD8+ T cell responses [33]. Given that the downstream effect of MHV68 induced immunosuppression was a result of impaired anti-malarial antibody responses, we initially asked whether levels of virus specific IgG responses were enhanced in the absence of M2 expression. To avoid a known defect in the establishment of splenic infection following intranasal inoculation of M2-deficient MHV68 mutants [36]we opted to infect mice with the same dose of virus (1000 PFU) as used in the previous experiments, but via the intraperitoneal route—a route and dose of virus which allow the M2-deficient mutant to efficiently infect the spleen [36]. As a proper control, the marker rescue virus (i.e, a recombinant MHV68 in which the genetic mutation introduced into the M2 mutant was restored to the wild type virus sequence) [37], was also administered via the IP route. Notably, we have extensively compared IN versus IP MHV68 co-infection with P. yoelii and found there to be no difference in outcome. M2.Stop (M2 virus; M2.St) infection in a C57BL/6 mouse induced a nearly 2-fold higher MHV68 specific IgG response as compared to infection with the marker rescue control virus (M2.MR; MR) (Fig 6A; day 21 post-infection Mann Whitney-U test p<0.05). It is important to note that day 21 post-MHV68 infection in this experiment corresponds to day 14 post-co-infection with P. yoelii XNL. The time point at which the virus specific humoral response is suppressed overlaps with the timing at which parasite specific IgG responses become severely compromised during co-infection (Fig 1C and 1E). This observation suggests that M2 may be mediating the virus-induced suppression of anti-malarial humoral immune responses.

Bottom Line: Importantly, this resulted in the transformation of a non-lethal P. yoelii XNL infection into a lethal one; an outcome that is correlated with a defect in the maintenance of germinal center B cells and T follicular helper (Tfh) cells in the spleen.Notably, co-infection with an M2- mutant MHV68 eliminates lethality of P. yoelii XNL.Collectively, our data demonstrates that an acute gammaherpesvirus infection can negatively impact the development of an anti-malarial immune response.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, United States of America; Microbiology and Molecular Genetics Graduate Program, Laney Graduate School, Emory University, Atlanta, Georgia, United States of America.

ABSTRACT
Immunity to non-cerebral severe malaria is estimated to occur within 1-2 infections in areas of endemic transmission for Plasmodium falciparum. Yet, nearly 20% of infected children die annually as a result of severe malaria. Multiple risk factors are postulated to exacerbate malarial disease, one being co-infections with other pathogens. Children living in Sub-Saharan Africa are seropositive for Epstein Barr Virus (EBV) by the age of 6 months. This timing overlaps with the waning of protective maternal antibodies and susceptibility to primary Plasmodium infection. However, the impact of acute EBV infection on the generation of anti-malarial immunity is unknown. Using well established mouse models of infection, we show here that acute, but not latent murine gammaherpesvirus 68 (MHV68) infection suppresses the anti-malarial humoral response to a secondary malaria infection. Importantly, this resulted in the transformation of a non-lethal P. yoelii XNL infection into a lethal one; an outcome that is correlated with a defect in the maintenance of germinal center B cells and T follicular helper (Tfh) cells in the spleen. Furthermore, we have identified the MHV68 M2 protein as an important virus encoded protein that can: (i) suppress anti-MHV68 humoral responses during acute MHV68 infection; and (ii) plays a critical role in the observed suppression of anti-malarial humoral responses in the setting of co-infection. Notably, co-infection with an M2- mutant MHV68 eliminates lethality of P. yoelii XNL. Collectively, our data demonstrates that an acute gammaherpesvirus infection can negatively impact the development of an anti-malarial immune response. This suggests that acute infection with EBV should be investigated as a risk factor for non-cerebral severe malaria in young children living in areas endemic for Plasmodium transmission.

No MeSH data available.


Related in: MedlinePlus