12 research outputs found
Zika virus pathogenesis in rhesus macaques is unaffected by pre-existing immunity to dengue virus
Zika virus (ZIKV) is a re-emerging virus that has recently spread into dengue virus (DENV) endemic regions and cross-reactive antibodies (Abs) could potentially affect ZIKV pathogenesis. Using DENV-immune serum, it has been shown in vitro that antibody-dependent enhancement (ADE) of ZIKV infection can occur. Here we study the effects of pre-existing DENV immunity on ZIKV infection in vivo. We infect two cohorts of rhesus macaques with ZIKV; one cohort has been exposed to DENV 2.8 years earlier and a second control cohort is naïve to flaviviral infection. Our results, while confirming ADE in vitro, suggest that pre-existing DENV immunity does not result in more severe ZIKV disease. Rather our results show a reduction in the number of days of ZIKV viremia compared to naïve macaques and that the previous exposure to DENV may result in modulation of the immune response without resulting in enhancement of ZIKV pathogenesis
Decreased Dengue Replication and an Increased Anti-viral Humoral Response with the use of Combined Toll-Like Receptor 3 and 7/8 Agonists in Macaques
Pathogenic versus protective outcomes to Dengue virus (DENV) infection are associated with innate immune function. This study aimed to determine the role of increased TLR3- and TLR7/8-mediated innate signaling after Dengue infection of rhesus macaques in vivo to evaluate its impact on disease and anti-DENV immune responses.TLR3 and TLR7/8 agonists (emulsified in Montanide) were administered subcutaneously to rhesus macaques at 48 hours and 7 days after DENV infection. The Frequency and activation of myeloid dendritic cells, plasmacytoid dendritic cells, and B cells were measured by flow cytometry while the serum levels of 14 different cytokines and chemokines were quantified. Adaptive immune responses were measured by DENV-specific antibody subtype measurements. Results showed that the combined TLR agonists reduced viral replication and induced the development of a proinflammatory reaction, otherwise absent in Dengue infection alone, without any clear signs of exacerbated disease. Specifically, the TLR-induced response was characterized by activation changes in mDC subsets concurrent with higher serum levels of CXCL-10 and IL-1Ra. TLR stimulation also induced higher titers of anti-DENV antibodies and acted to increase the IgG2/IgG1 ratio of anti-DENV to favor the subtype associated with DENV control. We also observed an effect of DENV-mediated suppression of mDC activation consistent with prior in vitro studies.These data show that concurrent TLR3/7/8 activation of the innate immune response after DENV infection in vivo acts to increase antiviral mechanisms via increased inflammatory and humoral responses in rhesus macaques, resulting in decreased viremia and melioration of the infection. These findings underscore an in vivo protective rather than a pathogenic role for combined TLR3/7/8-mediated activation in Dengue infection of rhesus macaques. Our study provides definitive proof-of-concept into the mechanism by which DENV evades immune recognition and activation in vivo
Limited Impact of Delta Variant’s Mutations on the Effectiveness of Neutralization Conferred by Natural Infection or COVID-19 Vaccines in a Latino Population
The SARS-CoV-2 pandemic has impacted public health systems all over the world. The Delta variant seems to possess enhanced transmissibility, but no clear evidence suggests it has increased virulence. Our data show that pre-exposed individuals had similar neutralizing activity against the authentic COVID-19 strain and the Delta and Epsilon variants. After only one vaccine dose, the neutralization capacity expanded to all tested variants in pre-exposed individuals. Healthy vaccinated individuals showed a limited breadth of neutralization. One vaccine dose did induce similar neutralizing antibodies against the Delta as against the authentic strain. However, even after two doses, this capacity only expanded to the Epsilon variant
Transcriptional Activation of Interferon-Stimulated Genes but Not of Cytokine Genes after Primary Infection of Rhesus Macaques with Dengue Virus Type 1â–¿
Macaques are the only animal model used to test dengue virus (DENV) vaccine candidates. Nevertheless, the pathogenesis of DENV in macaques is not well understood. In this work, by using Affymetrix oligonucleotide microarrays, we studied the broad transcriptional modifications and cytokine expression profile after infecting rhesus macaques with DENV serotype 1. Five days after infection, these animals produced a potent, innate antiviral immune response by inducing the transcription of signature genes from the interferon (IFN) pathway with demonstrated antiviral activity, such as myxoprotein, 2′,5′-oligoadenylate synthetase, phospholipid scramblase 1, and viperin. Also, IFN regulatory element 7, IFN-stimulated gene 15, and protein ligases linked to the ISGylation process were up-regulated. Unexpectedly, no up-regulation of IFN-α, -β, or -γ genes was detected. Transcription of the genes of interleukin-10 (IL-10), IL-8, IL-6, and tumor necrosis factor alpha was neither up-regulated nor down-regulated. Results were confirmed by real-time PCR and by multiplex cytokine detection in serum samples
Effective control of early Zika virus replication by Dengue immunity is associated to the length of time between the 2 infections but not mediated by antibodies.
Little is known about the contribution of virus-specific and cross-reacting antibodies (Abs) or the cellular immune response generated by a primary dengue (DENV) infection on the course of a secondary zika (ZIKV) infection in vivo. Here we show that the length of time between DENV/ZIKV infections has a qualitative impact on controlling early ZIKV replication. Depletion of DENV2-specific Abs in sera confirmed that those type-specific Abs do not contribute to ZIKV control. We show that the magnitude and durability of the neutralizing antibodies (nAbs) induced by a secondary ZIKV infection is modest compared to the response induced after a secondary heterologous DENV infection. Our in vivo results are showing a complex interplay between the cellular and innate immune responses characterized by a high frequency of plasmacytoid dendritic cells (pDC) correlating with an increase in the frequency of DENV antigen specific T cells and a significant control of ZIKV replication which is time dependent. Taken together, our results suggest that early after ZIKV infection other mechanisms such as the innate and cellular immune responses may play a predominant role in controlling ZIKV replication. Regardless of the time elapsed between infections there was no evidence of in vivo antibody-dependent enhancement (ADE) of ZIKV by DENV immunity. These findings have pivotal implications while interpreting ZIKV pathogenesis in flavivirus-experimented populations, diagnostic results interpretation and vaccine designs and schedules among others
Serum levels of CXCL-10 and IL-1Ra are increased significantly after TLR stimulation and are inhibited by DENV.
<p>A: Coincident with the higher level of mDC activation, serum levels of
CXCL-10 increased significantly only in the TLR group when compared to
the Control group. Higher levels, albeit not significant, were also
found in the DENV/TLR group. The lowest levels among the experimental
groups were found in animals of the DENV group. This trend in the serum
levels of CXCL-10 among different groups confirms a stimulatory effect
of the TLR agonist but at the same time suggests an inhibitory role of
Dengue virus in the secretion of this cytokine. B: Serum levels of
IL-1Ra peaked 48 hours after the first TLR stimulation. An inhibitory
effect of DENV at this time point (also coincident with the viremia
peak) is supported by significantly higher values of this cytokine in
the TLR group when compared to the DENV and DENV/TLR groups. Both
groups, DENV/TLR and TLR, showed significantly higher serum levels of
this cytokine when compared to the DENV and Control groups. Ten days
after the infection (72 hours after second TLR stimulation), IL1-Ra
values were still increased in both groups receiving TLR agonists.
Significantly higher levels were present up to 15 days after the
infection (8 days after the last TLR stimulation). However, at the later
time point, there was no significant difference between the DENV/TLR and
TLR groups. Asterisks denote significant differences, (*) p
<0.05, (**) p<0.01, and (***) p<0.001.</p
Toll-like receptor agonists abrogate viremia.
<p>A: Left panel, a peak of viremia was detected at day 4 after DENV
infection in two of three animals (44Z and AM28). However, this peak was
completely absent in the four animals of the DENV/TLR group at 48 hours
after the TLR3 and 7/8 agonists [poly (I:C) and CL097M-012,
respectively] were administered (right panel). Results are
expressed in milliequivalent genomes per milliliter. B: Plasma levels of
DENV protein NS1 were not significantly different between the DENV group
and the treated group (DENV/TLR). However, NS1 levels were significantly
higher in the DENV group compared to the Control group (p<0.018),
whereas they were not significantly different between the DENV/LTR
(despite the Dengue infection) and the Control groups. This confirmatory
assay corroborates the role of TLRs in controlling DENV replication. The
results reflect the ratio of the sample O.D./Control O.D. according to
the manufacturer's instructions.</p
Dengue virus inhibits TLR-induced activation of mDC.
<p>A: Left panel, 48 hours after the first TLR stimulation, mDC were
activated in the groups receiving TLRs but not in the group receiving
only the virus. Coincident with the peak of viremia at day 4, an
inhibitory effect of DENV on the mDC subset was evidenced by the
frequency of activated cells in the DENV group, which was significantly
lower compared to the DENV/TLR and TLR groups. Right panel, 10 days
after the infection (72 hours after second TLR stimulation) the mDC
subset was still significantly activated in both groups that received
TLRs when compared to the Control group. However, the inhibitory effect
of DENV was absent as there were no significant differences between the
DENV and DENV/TLR groups, supporting the role of DENV replication in the
inhibitory effect on mDC activation on day 4. B: Ten days after
infection and 72 hours after the secondary TLR stimulation the frequency
of activated pDC was significantly higher in the DENV/TLR and TLR groups
compared to the DENV and Control groups. However, an inhibitory effect
of DENV on this subset of DC was not observed. Asterisks denote
significant differences, (*) p <0.05, (**) p <0.01,
and (***) p<0.00.</p
TLR3-7/8 stimulations in synergism with DENV induce quantitative and qualitative modifications of the humoral response.
<p>A: Ten days after the infection, the frequency of activated B cells was
significantly higher in DENV/TLR group when compared to all other
groups, showing a synergistic effect of DENV with the TLR agonists in
this activation. DENV alone was able to induce activation of B cells
when compared to the TLR and Control groups. However, in our model, TLR
agonists alone were not sufficient to induce B-cell activation. B: The
activation profile of B cells correlates with the levels of anti-DENV
antibodies. Antibody levels were significantly higher in the DENV/TLR
group compared to the DENV group. C: As early as 10 days after infection
and coincident with activation of B cells, the switch to IgG1 was
significantly diminished in the DENV/TLR group. This difference had
disappeared by 15 days after the infection, but it was re-established on
day 30. D: Although antibody O.D. values were limited, the difference in
the IgG1 and IgG2 levels translated into a significant increase of the
IgG2/IgG1 ratio (>11 and 6 times on days 10 and 30 after the
infection, respectively). Asterisks denote significant differences,
(*) p<0.05, (**) p<0.01, and (***)
p<0.001.</p
Immune cell composition varies by age, sex and exposure to social adversity in free‑ranging Rhesus Macaques
Increasing age is associated with dysregulated immune function and increased inflammation—patterns that are also observed in individuals exposed to chronic social adversity. Yet we still know little about how social adversity impacts the immune system and how it might promote age-related diseases. Here, we investigated how immune cell diversity varied with age, sex and social adversity (operationalized as low social status) in free-ranging rhesus macaques. We found age-related signatures of immunosenescence, including lower proportions of CD20 + B cells, CD20 + /CD3 + ratio, and CD4 + /CD8 + T cell ratio – all signs of diminished antibody production. Age was associated with higher proportions of CD3 + /CD8 + Cytotoxic T cells, CD16 + /CD3- Natural Killer cells, CD3 + /CD4 + /CD25 + and CD3 + /CD8 + /CD25 + T cells, and CD14 + /CD16 + /HLA-DR + intermediate monocytes, and lower levels of CD14 + /CD16-/HLA-DR + classical monocytes, indicating greater amounts of inflammation and immune dysregulation. We also found a sex-dependent effect of exposure to social adversity (i.e., low social status). High-status males, relative to females, had higher CD20 + /CD3 + ratios and CD16 + /CD3 Natural Killer cell proportions, and lower proportions of CD8 + Cytotoxic T cells. Further, low-status females had higher proportions of cytotoxic T cells than high-status females, while the opposite was observed in males. High-status males had higher CD20 + /CD3 + ratios than low-status males. Together, our study identifies the strong age and sex-dependent effects of social adversity on immune cell proportions in a human-relevant primate model. Thus, these results provide novel insights into the combined effects of demography and social adversity on immunity and their potential contribution to age-related diseases in humans and other animals