Longitudinal Study of Cellular and Systemic Cytokine Signatures to Define the Dynamics of a Balanced Immune Environment During Disease Manifestation in Zika Virus-Infected Patients

Background

Since its unexpected reemergence, Zika virus (ZIKV) has caused numerous outbreaks globally. This study characterized the host immune responses during ZIKV infection.

Methods

Patient samples were collected longitudinally during the acute, convalescence and recovery phases of ZIKV infection over 6 months during the Singapore outbreak in late 2016. Plasma immune mediators were profiled via multiplex microbead assay, while changes in blood cell numbers were determined with immunophenotyping.

Results

Data showed the involvement of various immune mediators during acute ZIKV infection accompanied by a general reduction in blood cell numbers for all immune subsets except CD14⁺ monocytes. Importantly, viremic patients experiencing moderate symptoms had significantly higher quantities of interferon γ–induced protein 10, monocyte chemotactic protein 1, interleukin 1 receptor antagonist, interleukin 8, and placental growth factor 1, accompanied by reduced numbers of peripheral CD8⁺ T cells, CD4⁺ T cells, and double-negative T cells. Levels of T-cell associated mediators, including interferon γ–induced protein 10, interferon γ, and interleukin 10, were high in recovery phases of ZIKV infection, suggesting a functional role for T cells. The identification of different markers at specific disease phases emphasizes the dynamics of a balanced cytokine environment in disease progression.

Conclusions

This is the first comprehensive study that highlights specific cellular changes and immune signatures during ZIKV disease progression, and it provides valuable insights into ZIKV immunopathogenesis.

Plasmodium co-infection protects against chikungunya virus-induced pathologies

Co-infection with Plasmodium and chikungunya virus (CHIKV) has been reported in humans, but the impact of co-infection on pathogenesis remains unclear. Here, we show that prior exposure to Plasmodium suppresses CHIKV-associated pathologies in mice. Mechanistically, Plasmodium infection induces IFNγ, which reduces viraemia of a subsequent CHIKV infection and suppresses tissue viral load and joint inflammation. Conversely, concomitant infection with both pathogens limits the peak of joint inflammation with no effect on CHIKV viraemia. Reduced peak joint inflammation is regulated by elevated apoptosis of CD4+ T-cells in the lymph nodes and disrupted CXCR3-mediated CD4+ T-cell migration that abolishes their infiltration into the joints. Virus clearance from tissues is delayed in both infection scenarios, and is associated with a disruption of B cell affinity-maturation in the spleen that reduces CHIKV-neutralizing antibody production.

Efficient detection of Zika virus RNA in patients' blood from the 2016 outbreak in Campinas, Brazil

Infection with Zika virus (ZIKV), a mosquito-borne flavivirus has been casually linked with increased congenital microcephaly in Brazil from 2015 through 2016. Sensitive and specific diagnosis of patients with Zika fever (ZIKF) remains critical for patient management. We developed a ZIKV NS5 qRT-PCR assay by combining primers described by Balm et al. and a new Taqman probe. The assay was evaluated and compared with another assay described by Lanciotti et al. (ZIKV 1107) using 51 blood and 42 urine samples from 54 suspected ZIKV patients. ZIKV NS5 performed better in terms of sensitivity with more samples detected as ZIKV-positive (n = 37) than ZIKV 1107 (n = 34) for urine, and ZIKV-positive (n = 29) than ZIKV 1107 (n = 26) for blood. Both assays displayed good overall agreement for urine (κappa = 0.770) and blood (κappa = 0.825) samples. Improved availability of validated diagnostic tests, such ZIKV NS5 qRT-PCR, will be critical to ensure adequate and accurate ZIKV diagnosis.

Persistence of Zika virus in conjunctival fluid of convalescence patients

A widespread epidemic of Zika fever, caused by Zika virus (ZIKAV) has spread throughout the Pacific islands, the Americas and Southeast Asia. The increased incidences of ocular anomalies observed in ZIKAV-infected infants and adults may be associated with the rapid spread of ZIKAV. The objective of this study was to check if ZIKAV could be detected in human tears after the first week of infection. Twenty-nine patients with PCR confirmed ZIKAV infection during the Singapore August 2016 ZIKAV outbreak were enrolled for the study. Detection and quantification of ZIKAV RNA was performed on conjunctival swabs collected from both eyes of these patients at the late convalescent phase (30 days post-illness). Efficiency of viral isolation from swab samples was confirmed by the limit of detection (as low as 0.1 PFU/µL, equivalent to copy number of 4.9) in spiked swabs with different concentrations of ZIKAV (PFU/µL). Samples from three patients were found positive by qRT-PCR for ZIKAV and the viral RNA copy numbers detected in conjunctival swabs ranged from 5.2 to 9.3 copies respectively. ZIKAV could persist in the tears of infected patients for up to 30 days post-illness, and may therefore possess a potential public health risk of transmission.

Specific Biomarkers Associated With Neurological Complications and Congenital Central Nervous System Abnormalities From Zika Virus-Infected Patients in Brazil

Background

Zika virus (ZIKV) infections have been linked to different levels of clinical outcomes, ranging from mild rash and fever to severe neurological complications and congenital malformations.

Methods

We investigated the clinical and immunological response, focusing on the immune mediators profile in 95 acute ZIKV-infected adult patients from Campinas, Brazil. These patients included 6 pregnant women who later delivered during the course of this study. Clinical observations were recorded during hospitalization. Levels of 45 immune mediators were quantified using multiplex microbead-based immunoassays.

Results

Whereas 11.6% of patients had neurological complications, 88.4% displayed mild disease of rash and fever. Several immune mediators were specifically higher in ZIKV-infected patients, and levels of interleukin 10, interferon gamma-induced protein 10 (IP-10), and hepatocyte growth factor differentiated between patients with or without neurological complications. Interestingly, higher levels of interleukin 22, monocyte chemoattractant protein 1, TNF-α, and IP-10 were observed in ZIKV-infected pregnant women carrying fetuses with fetal growth–associated malformations. Notably, infants with congenital central nervous system deformities had significantly higher levels of interleukin 18 and IP-10 but lower levels of hepatocyte growth factor than those without such abnormalities born to ZIKV-infected mothers.

Conclusions

This study identified several key markers for the control of ZIKV pathogenesis. This will allow a better understanding of the molecular mechanisms of ZIKV infection in patients.

Severity of Plasma Leakage Is Associated With High Levels of Interferon γ-Inducible Protein 10, Hepatocyte Growth Factor, Matrix Metalloproteinase 2 (MMP-2), and MMP-9 During Dengue Virus Infection

BACKGROUND

 Dengue virus infection typically causes mild dengue fever, but, in severe cases, life-threatening dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) occur. The pathophysiological hallmark of DHF and DSS is plasma leakage that leads to enhanced vascular permeability, likely due to a cytokine storm.

METHODS

 Ninety patients with dengue during 2010-2012 in Singapore were prospectively recruited and stratified according to their disease phase, primary and secondary infection status, and disease severity, measured by plasma leakage. Clinical parameters were recorded throughout the disease progression. The levels of various immune mediators were quantified using comprehensive multiplex microbead-based immunoassays for 46 immune mediators.

RESULTS

 Associations between clinical parameters and immune mediators were analyzed using various statistical methods. Potential immune markers, including interleukin 1 receptor antagonist, interferon γ-inducible protein 10, hepatocyte growth factor, soluble p75 tumor necrosis factor α receptor, vascular cell adhesion molecule 1, and matrix metalloproteinase 2, were significantly associated with significant plasma leakage. Secondary dengue virus infections were also shown to influence disease outcome in terms of disease severity.

CONCLUSIONS

 This study identified several key markers for exacerbated dengue pathogenesis, notably plasma leakage. This will allow a better understanding of the molecular mechanisms of DHF and DSS in patients with dengue.

Myeloid Cell Arg1 Inhibits Control of Arthritogenic Alphavirus Infection by Suppressing Antiviral T Cells

Arthritogenic alphaviruses, including Ross River virus (RRV) and chikungunya virus (CHIKV), are responsible for explosive epidemics involving millions of cases. These mosquito-transmitted viruses cause inflammation and injury in skeletal muscle and joint tissues that results in debilitating pain. We previously showed that arginase 1 (Arg1) was highly expressed in myeloid cells in the infected and inflamed musculoskeletal tissues of RRV- and CHIKV-infected mice, and specific deletion of Arg1 from myeloid cells resulted in enhanced viral control. Here, we show that Arg1, along with other genes associated with suppressive myeloid cells, is induced in PBMCs isolated from CHIKV-infected patients during the acute phase as well as the chronic phase, and that high Arg1 expression levels were associated with high viral loads and disease severity. Depletion of both CD4 and CD8 T cells from RRV-infected Arg1-deficient mice restored viral loads to levels detected in T cell-depleted wild-type mice. Moreover, Arg1-expressing myeloid cells inhibited virus-specific T cells in the inflamed and infected musculoskeletal tissues, but not lymphoid tissues, following RRV infection in mice, including suppression of interferon-γ and CD69 expression. Collectively, these data enhance our understanding of the immune response following arthritogenic alphavirus infection and suggest that immunosuppressive myeloid cells may contribute to the duration or severity of these debilitating infections.

Mosquito-transmitted chikungunya virus (CHIKV), Ross River virus (RRV), and related alphaviruses cause epidemics involving millions of persons, such as on-going CHIKV outbreaks in the Caribbean and Central and South America. Infection with these viruses results in severe pain due to inflammation of musculoskeletal tissues that can persist for months and even years. There are no specific therapeutics or licensed vaccines for these viruses. Suppressive myeloid cells have been shown to inhibit anti-pathogen immune responses, including T cell responses, which can promote chronic disease. We showed previously that a gene associated with suppressive myeloid cells, arginase 1 (Arg1), was induced in musculoskeletal tissues and macrophages of mice infected with RRV or CHIKV, and mice that lacked Arg1 expression in myeloid cells had reduced viral loads at late times post-infection. Here, we demonstrate that Arg1 is induced in PBMCs isolated from CHIKV-infected patients, and Arg1 expression is associated with viral loads. Moreover, we found that Arg1-expressing myeloid cells inhibit the activation and function of antiviral T cells in RRV-infected mice. These studies underscore the role of suppressive myeloid cells in modulating the T cell response to arthritogenic alphaviruses and provide a therapeutic target to enhance viral clearance and potentially limit chronic disease.

Loss of TLR3 aggravates CHIKV replication and pathology due to an altered virus-specific neutralizing antibody response

RNA-sensing toll-like receptors (TLRs) mediate innate immunity and regulate anti-viral response. We show here that TLR3 regulates host immunity and the loss of TLR3 aggravates pathology in Chikungunya virus (CHIKV) infection. Susceptibility to CHIKV infection is markedly increased in human and mouse fibroblasts with defective TLR3 signaling. Up to 100-fold increase in CHIKV load was observed in Tlr3^−/− mice, alongside increased virus dissemination and pro-inflammatory myeloid cells infiltration. Infection in bone marrow chimeric mice showed that TLR3-expressing hematopoietic cells are required for effective CHIKV clearance. CHIKV-specific antibodies from Tlr3^−/− mice exhibited significantly lower in vitro neutralization capacity, due to altered virus-neutralizing epitope specificity. Finally, SNP genotyping analysis of CHIKF patients on TLR3 identified SNP rs6552950 to be associated with disease severity and CHIKV-specific neutralizing antibody response. These results demonstrate a key role for TLR3-mediated antibody response to CHIKV infection, virus replication and pathology, providing a basis for future development of immunotherapeutics in vaccine development.

An integrated lab-on-chip for rapid identification and simultaneous differentiation of tropical pathogens

Tropical pathogens often cause febrile illnesses in humans and are responsible for considerable morbidity and mortality. The similarities in clinical symptoms provoked by these pathogens make diagnosis difficult. Thus, early, rapid and accurate diagnosis will be crucial in patient management and in the control of these diseases. In this study, a microfluidic lab-on-chip integrating multiplex molecular amplification and DNA microarray hybridization was developed for simultaneous detection and species differentiation of 26 globally important tropical pathogens. The analytical performance of the lab-on-chip for each pathogen ranged from 10² to 10³ DNA or RNA copies. Assay performance was further verified with human whole blood spiked with Plasmodium falciparum and Chikungunya virus that yielded a range of detection from 200 to 4×10⁵ parasites, and from 250 to 4×10⁷ PFU respectively. This lab-on-chip was subsequently assessed and evaluated using 170 retrospective patient specimens in Singapore and Thailand. The lab-on-chip had a detection sensitivity of 83.1% and a specificity of 100% for P. falciparum; a sensitivity of 91.3% and a specificity of 99.3% for P. vivax; a positive 90.0% agreement and a specificity of 100% for Chikungunya virus; and a positive 85.0% agreement and a specificity of 100% for Dengue virus serotype 3 with reference methods conducted on the samples. Results suggested the practicality of an amplification microarray-based approach in a field setting for high-throughput detection and identification of tropical pathogens.

Tropical diseases consist of a group of debilitating and fatal infections that occur primarily in rural and urban settings of tropical and subtropical countries. While the primary indices of an infection are mostly the presentation of clinical signs and symptoms, outcomes due to an infection with tropical pathogens are often unspecific. Accurate diagnosis is crucial for timely intervention, appropriate and adequate treatments, and patient management to prevent development of sequelae and transmission. Although, multiplex assays are available for the simultaneous detection of tropical pathogens, they are generally of low throughput. Performing parallel assays to cover the detection for a comprehensive scope of tropical infections that include protozoan, bacterial and viral infections is undoubtedly labor-intensive and time consuming. We present an integrated lab-on-chip using microfluidics technology coupled with reverse transcription (RT), PCR amplification, and microarray hybridization for the simultaneous identification and differentiation of 26 tropical pathogens that cause 14 globally important tropical diseases. Such diagnostics capacity would facilitate evidence-based management of patients, improve the specificity of treatment and, in some cases, even allow contact tracing and other disease-control measures.