Chronic chikungunya disease (CCD): clinical insights, immunopathogenesis, and therapeutic perspectives.

Chikungunya virus, an arthropod-borne pathogen is recognised by the World Health Organization as a top priority Emerging Infectious Disease and is ranked fourth in public health needs according to the Coalition for Epidemic Preparedness Innovations (CEPI). Despite its substantial impact, as evidenced by an annual estimate of 120,274 disability-adjusted life years, our understanding of the chronic aspects of chikungunya disease remains limited. This review focuses on Chronic Chikungunya Disease (CCD), emphasising its clinical manifestations, immunopathogenesis, therapeutic options, and disease burden.

FHL1 promotes chikungunya and o'nyong-nyong virus infection and pathogenesis with implications for alphavirus vaccine design.

Arthritogenic alphaviruses are positive-strand RNA viruses that cause debilitating musculoskeletal diseases affecting millions worldwide. A recent discovery identified the four-and-a-half-LIM domain protein 1 splice variant A (FHL1A) as a crucial host factor interacting with the hypervariable domain (HVD) of chikungunya virus (CHIKV) nonstructural protein 3 (nsP3). Here, we show that acute and chronic chikungunya disease in humans correlates with elevated levels of FHL1. We generated FHL1-/- mice, which when infected with CHIKV or o'nyong-nyong virus (ONNV) displayed reduced arthritis and myositis, fewer immune infiltrates, and reduced proinflammatory cytokine/chemokine outputs, compared to infected wild-type (WT) mice. Interestingly, disease signs were comparable in FHL1-/- and WT mice infected with arthritogenic alphaviruses Ross River virus (RRV) or Mayaro virus (MAYV). This aligns with pull-down assay data, which showed the ability of CHIKV and ONNV nsP3 to interact with FHL1, while RRV and MAYV nsP3s did not. We engineered a CHIKV mutant unable to bind FHL1 (CHIKV-ΔFHL1), which was avirulent in vivo. Following inoculation with CHIKV-ΔFHL1, mice were protected from disease upon challenge with CHIKV and ONNV, and viraemia was significantly reduced in RRV- and MAYV-challenged mice. Targeting FHL1-binding as an approach to vaccine design could lead to breakthroughs in mitigating alphaviral disease.

Role of MXRA8 in Ross River Virus Disease Pathogenesis.

Arthritogenic alphaviruses such as Ross River virus (RRV) and Chikungunya virus (CHIKV) are responsible for large-scale epidemics that cause debilitating acute and chronic musculoskeletal diseases. MXRA8 was recently discovered as an entry receptor for multiple alphaviruses including CHIKV, RRV, Mayaro virus (MAYV), and O'nyong-nyong virus (ONNV). However, the role of MXRA8 in the development of alphavirus-induced musculoskeletal inflammation has not yet been fully studied. Here, we attempt to fully characterize the contribution of MXRA8 to RRV disease in an established mouse model. MXRA8 knockout (MXRA8-/-) mice generated on a C57BL/6J background, showed abrogated disease signs and reduced viral replication, which correlated with lower viral load, diminished proinflammatory cytokines, and limited cell infiltrates in inflamed tissues. Immunomodulation genes were upregulated to higher levels in RRV-infected wild-type (WT) mice than in MXRA8-/- mice. Intriguingly, Cdkn1a and Ifi44 genes in blood and CD127/IL7RA, CD45, BatF3, IFNGR, Ly6G/Ly6C, CD40, CD127, F4/80, and MHC-II genes in quadriceps were found to be upregulated in RRV-infected MXRA8-/- mice compared to WT mice. Our results showed an essential role of MXRA8 in the immune response of mice infected with RRV and, more importantly, demonstrated novel changes in immunomodulation genes, which shed light on the immunopathogenesis of alphavirus-induced disease. IMPORTANCE Previous studies have shown the importance of the cell surface protein MXRA8 as an entry receptor for several different prominent alphaviruses such as CHIKV, RRV, MAYV, and ONNV. In particular, the role of MXRA8 in the tissue tropism, viral pathogenesis, and immune response of a CHIKV mouse model have already been briefly characterized. However, the role of MXRA8 warrants further characterization in RRV disease background, since there are noticeable differences in the disease profile between CHIKV and RRV. For example, patients infected with CHIKV are usually affected by sudden onset of severe arthritis and fever, whereas RRV-infected patients generally only have minor joint pain and mild fever. Here, we characterized the role of MXRA8 in RRV disease and assessed several key mechanisms of MXRA8 that may contribute to the disease progression.

Repurposing of drugs targeting the cytokine storm induced by SARS-CoV-2.

A cytokine storm is one of the leading causes of acute respiratory distress syndrome (ARDS) and sepsis-associated multiple organ failure in many respiratory viral infections, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The coronavirus disease 2019 (COVID-19) pandemic has caused millions of deaths worldwide, resulting in an urgent need for effective therapeutic interventions. Repurposing immunosuppressive drugs that target cytokines with immunomodulatory properties is a promising approach to counteract SARS-CoV-2-induced ARDS at the infective and post-infective stages. In this minireview, we examine drugs targeting IL-1ß, IL-4/IL-13, IL-6 and TNF-α tested in COVID-19 patients.

Ocular tropism of SARS-CoV-2 in animal models with retinal inflammation via neuronal invasion following intranasal inoculation.

Although ocular manifestations are reported in patients with COVID-19, consensus on ocular tropism of SARS-CoV-2 is lacking. Here, we infect K18-hACE2 transgenic mice with SARS-CoV-2 using various routes. We observe ocular manifestation and retinal inflammation with production of pro-inflammatory cytokines in the eyes of intranasally (IN)-infected mice. Intratracheal (IT) infection results in dissemination of the virus from the lungs to the brain and eyes via trigeminal and optic nerves. Ocular and neuronal invasions are confirmed using intracerebral (IC) infection. Notably, the eye-dropped (ED) virus does not cause lung infection and becomes undetectable with time. Ocular and neurotropic distribution of the virus in vivo is evident in fluorescence imaging with an infectious clone of SARS-CoV-2-mCherry. The ocular tropic and neuroinvasive characteristics of SARS-CoV-2 are confirmed in wild-type Syrian hamsters. Our data can improve the understanding regarding viral transmission and clinical characteristics of SARS-CoV-2 and help in improving COVID-19 control procedures.

The Delta SARS-CoV-2 Variant of Concern Induces Distinct Pathogenic Patterns of Respiratory Disease in K18-hACE2 Transgenic Mice Compared to the Ancestral Strain from Wuhan.

Compared to the original ancestral strain of SARS-CoV-2, the Delta variant of concern has shown increased transmissibility and resistance toward COVID-19 vaccines and therapies. However, the pathogenesis of the disease associated with Delta is still not clear. In this study, using K18-hACE2 transgenic mice, we assessed the pathogenicity of the Delta variant by characterizing the immune response following infection. We found that Delta induced the same clinical disease manifestations as the ancestral SARS-CoV-2, but with significant dissemination to multiple tissues, such as brain, intestine, and kidney. Histopathological analysis showed that tissue pathology and cell infiltration in the lungs of Delta-infected mice were the same as in mice infected with the ancestral SARS-CoV-2. Delta infection caused perivascular inflammation in the brain and intestinal wall thinning in K18-hACE2 transgenic mice. Increased cell infiltration in the kidney was observed in both ancestral strain- and Delta-infected mice, with no clear visible tissue damage identified in either group. Interestingly, compared with mice infected with the ancestral strain, the numbers of CD45+ cells, T cells, B cells, inflammatory monocytes, and dendritic cells were all significantly lower in the lungs of the Delta-infected mice, although there was no significant difference in the levels of proinflammatory cytokines between the two groups. Our results showed distinct immune response patterns in the lungs of K18-hACE2 mice infected with either the ancestral SARS-CoV-2 or Delta variant of concern, which may help to guide therapeutic interventions for emerging SARS-CoV-2 variants. IMPORTANCE SARS-CoV-2 variants, with the threat of increased transmissibility, infectivity, and immune escape, continue to emerge as the COVID-19 pandemic progresses. Detailing the pathogenesis of disease caused by SARS-CoV-2 variants, such as Delta, is essential to better understand the clinical threat caused by emerging variants and associated disease. This study, using the K18-hACE2 mouse model of severe COVID-19, provides essential observation and analysis on the pathogenicity and immune response of Delta infection. These observations shed light on the changing disease profile associated with emerging SARS-CoV-2 variants and have potential to guide COVID-19 treatment strategies.

TIR-Domain-Containing Adapter-Inducing Interferon-ß (TRIF)-Dependent Antiviral Responses Protect Mice against Ross River Virus Disease.

Ross River virus (RRV) is the major mosquito-borne virus in the South Pacific region. RRV infections are characterized by arthritic symptoms, which can last from several weeks to months. Type I interferon (IFN), the primary antiviral innate immune response, is able to modulate adaptive immune responses. The relationship between the protective role of type I IFN and the induction of signaling proteins that drive RRV disease pathogenesis remains poorly understood. In the present study, the role of TIR-domain-containing adapter-inducing interferon-ß (TRIF), an essential signaling adaptor protein downstream of Toll-like receptor (TLR) 3, a key single-stranded RNA (ssRNA)-sensing receptor, was investigated. We found that TRIF-/- mice were highly susceptible to RRV infection, with severe disease, high viremia, and a low type I IFN response early during disease development, which suggests the TLR3-TRIF axis may engage early in response to RRV infection. The number and the activation level of CD4+ T cells, CD8+ T cells, and NK cells were reduced in TRIF-/- mice compared to those in infected wild-type (WT) mice. In addition, the number of germinal center B cells was lower in TRIF-/- mice than WT mice following RRV infection, with lower titers of IgG antibodies detected in infected TRIF-/- mice compared to WT. Interestingly, the requirement for TRIF to promote immunoglobulin class switch recombination was at the level of the local immune microenvironment rather than B cells themselves. The slower resolution of RRV disease in TRIF-/- mice was associated with persistence of the RRV genome in muscle tissue and a continuing IFN response. IMPORTANCE RRV has been prevalent in the South Pacific region for decades and causes substantial economic and social costs. Though RRV is geographically restricted, a number of other alphaviruses have spread globally due to expansion of the mosquito vectors and increased international travel. Since over 30 species of mosquitoes have been implicated as potent vectors for RRV dissemination, RRV has the potential to further expand its distribution. In the pathogenesis of RRV disease, it is still not clear how innate immune responses synergize with adaptive immune responses. Type I IFN is crucial for bridging innate to adaptive immune responses to viral invasion. Hence, key signaling proteins in type I IFN induction pathways, which are important for type I IFN modulation, may also play critical roles in viral pathogenesis. This study provides insight into the role of TRIF in RRV disease development.

Comorbidities in SARS-CoV-2 Patients: a Systematic Review and Meta-Analysis.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has rapidly spread across the globe at unprecedented speed and is showing no signs of slowing down. The outbreak of coronavirus disease 2019 (COVID-19) has led to significant health burden in infected patients especially in those with underlying comorbidities. The aim of this study was to evaluate the correlation between comorbidities and their role in the exacerbation of disease in COVID-19 patients leading to fatal outcomes. A systematic review was conducted using data from MEDLINE, Scopus, Web of Science, and EMBASE databases published from 1 December 2019 to 15 September 2020. Fifty-three articles were included in the systematic review. Of those 53 articles, 8 articles were eligible for meta-analysis. Hypertension, obesity, and diabetes mellitus were identified to be the most prevalent comorbidities in COVID-19 patients. Our meta-analysis showed that cancer, chronic kidney diseases, diabetes mellitus, and hypertension were independently associated with mortality in COVID-19 patients. Chronic kidney disease was statistically the most prominent comorbidity leading to death. However, despite having high prevalence, obesity was not associated with mortality in COVID-19 patients.IMPORTANCE COVID-19 has plagued the world since it was first identified in December 2019. Previous systematic reviews and meta-analysis were limited by various factors such as the usage of non-peer reviewed data and were also limited by the lack of clinical data on a global scale. Comorbidities are frequently cited as risk factors for severe COVID-19 outcomes. However, the degree to which specific comorbidities impact the disease is debatable. Our study selection involves a global reach and covers all comorbidities that were reported to be involved in the exacerbation of COVID-19 leading to fatal outcomes, which allows us to identify the specific comorbidities that have higher risk in patients. The study highlights COVID-19 high-risk groups. However, further research should focus on the status of comorbidities and prognosis in COVID-19 patients.

Development of vaccines for SARS-CoV-2.

COVID-19 emerged in late 2019 and has rapidly spread through many countries globally. The causative SARS-CoV-2 virus was not known until recently, and there is little or no natural immunity in human populations. There is an urgent need for vaccines and drugs to combat this new pandemic. In just a few months, huge efforts and resources by government, academia, and industry have been thrown into the race to develop a vaccine. This brief review summarizes and discusses the array of technologies being applied to vaccine development, highlighting the strengths and weaknesses of the various approaches.

Occurrence of zoonotic Cryptosporidium and Giardia duodenalis species/genotypes in urban rodents.

This report describes the detection of zoonotic Cryptosporidium muris, C. parvum subgenotype IIa and Giardia duodenalis genotype B in urban rodents in Malaysia. A rare occurrence of C. meleagridis was also reported suggesting a role of rodents in mechanical transmission of this pathogen. Utilization of DNA sequencing and subtyping analysis confirmed the presence of zoonotic C. parvum subtypes IIaA17G2R1 and IIaA16G3R1 for the first time in rodents.