Human coronavirus OC43-elicited CD4+ T cells protect against SARS-CoV-2 in HLA transgenic mice.

SARS-CoV-2-reactive T cells are detected in some healthy unexposed individuals. Human studies indicate these T cells could be elicited by the common cold coronavirus OC43. To directly test this assumption and define the role of OC43-elicited T cells that are cross-reactive with SARS-CoV-2, we develop a model of sequential infections with OC43 followed by SARS-CoV-2 in HLA-B*0702 and HLA-DRB1*0101 Ifnar1-/- transgenic mice. We find that OC43 infection can elicit polyfunctional CD8+ and CD4+ effector T cells that cross-react with SARS-CoV-2 peptides. Furthermore, pre-exposure to OC43 reduces subsequent SARS-CoV-2 infection and disease in the lung for a short-term in HLA-DRB1*0101 Ifnar1-/- transgenic mice, and a longer-term in HLA-B*0702 Ifnar1-/- transgenic mice. Depletion of CD4+ T cells in HLA-DRB1*0101 Ifnar1-/- transgenic mice with prior OC43 exposure results in increased viral burden in the lung but no change in virus-induced lung damage following infection with SARS-CoV-2 (versus CD4+ T cell-sufficient mice), demonstrating that the OC43-elicited SARS-CoV-2 cross-reactive T cell-mediated cross-protection against SARS-CoV-2 is partially dependent on CD4+ T cells. These findings contribute to our understanding of the origin of pre-existing SARS-CoV-2-reactive T cells and their effects on SARS-CoV-2 clinical outcomes, and also carry implications for development of broadly protective betacoronavirus vaccines.

Human Monkeypox: A Comprehensive Overview of Epidemiology, Pathogenesis, Diagnosis, Treatment, and Prevention Strategies.

Monkeypox virus (MPXV) is an emerging zoonotic virus that belongs to the Orthopoxvirus genus and presents clinical symptoms similar to those of smallpox, such as fever and vesicular-pustular skin lesions. However, the differential diagnosis between smallpox and monkeypox is that smallpox does not cause lymphadenopathy but monkeypox generates swelling in the lymph nodes. Since the eradication of smallpox, MPXV has been identified as the most common Orthopoxvirus to cause human disease. Despite MPXV being endemic to certain regions of Africa, the current MPXV outbreak, which began in early 2022, has spread to numerous countries worldwide, raising global concern. As of the end of May 2023, over 87,545 cases and 141 deaths have been reported, with most cases identified in non-endemic countries, primarily due to human-to-human transmission. To better understand this emerging threat, this review presents an overview of key aspects of MPXV infection, including its animal reservoirs, modes of transmission, animal models, epidemiology, clinical and immunological features, diagnosis, treatments, vaccines, and prevention strategies. The material presented here provides a comprehensive understanding of MPXV as a disease, while emphasizing the significance and unique characteristics of the 2022 outbreak. This offers valuable information that can inform future research and aid in the development of effective interventions.

SARS-CoV-2 and Dengue Virus Coinfection in a Mexican Pediatric Patient: A Case Report from Early Molecular Diagnosis.

Mexico is an endemic region for dengue virus (DENV). The increase in this disease coincides with outbreaks of COVID-19, both of which are single-stranded positive RNA viruses. These characteristics make it difficult to distinguish each disease because they share clinical and laboratory features, which can consequently result in misdiagnoses. This is why the use of precision confirmatory tests (qRT-PCR) are crucial for early diagnosis. We herein report a pediatric patient who presented a coinfection for DENV and COVID-19, "SARS-CoV-2/Dengue". This patient initially presented a fever, cough, and headache and, three days later, developed generalized pain and epistaxis. Blood studies revealed thrombocytopenia and leukopenia, and the patient was admitted to the hospital for a probable DENV infection. Within 48 h, qRT-PCR tests specific for SARS-CoV-2 and DENV were performed and resulted as positive. The patient immediately received pharmacological treatment with azithromycin, oseltamivir, and metamizole. During hospitalization (9 days), the patient had no signs of respiratory distress and maintained normal body temperature and normal blood oxygen saturation. This case warns of the need for early diagnosis and adequate clinical and pharmacological management in the face of a "SARS-CoV-2/Dengue" coinfection. Early molecular detection of both viruses and timely treatment helped the patient to achieve a favorable recovery.

A Zika virus mutation enhances transmission potential and confers escape from protective dengue virus immunity.

Zika virus (ZIKV) and dengue virus (DENV) are arthropod-borne pathogenic flaviviruses that co-circulate in many countries. To understand some of the pressures that influence ZIKV evolution, we mimic the natural transmission cycle by repeating serial passaging of ZIKV through cultured mosquito cells and either DENV-naive or DENV-immune mice. Compared with wild-type ZIKV, the strains passaged under both conditions exhibit increased pathogenesis in DENV-immune mice. Application of reverse genetics identifies an isoleucine-to-valine mutation (I39V) in the NS2B proteins of both passaged strains that confers enhanced fitness and escape from pre-existing DENV immunity. Introduction of I39V or I39T, a naturally occurring homologous mutation detected in recent ZIKV isolates, increases the replication of wild-type ZIKV in human neuronal precursor cells and laboratory-raised mosquitoes. Our data indicate that ZIKV strains with enhanced transmissibility and pathogenicity can emerge in DENV-naive or -immune settings, and that NS2B-I39 mutants may represent ZIKV variants of interest.

An Overview of Vaccines against SARS-CoV-2 in the COVID-19 Pandemic Era.

The emergence of SARS-CoV-2 in late 2019 led to the COVID-19 pandemic all over the world. When the virus was first isolated and its genome was sequenced in the early months of 2020, the efforts to develop a vaccine began. Based on prior well-known knowledge about coronavirus, the SARS-CoV-2 spike (S) protein was selected as the main target. Currently, more than one hundred vaccines are being investigated and several of them are already authorized by medical agencies. This review summarizes and compares the current knowledge about main approaches for vaccine development, focusing on those authorized and specifically their immunogenicity, efficacy preventing severe disease, adverse side effects, protection, and ability to cope with emergent SARS-CoV-2 variants.

CD8+ T cells mediate protection against Zika virus induced by an NS3-based vaccine.

Zika virus (ZIKV) is associated with congenital malformations in infants born to infected mothers, and with Guillain-Barré syndrome in infected adults. Development of ZIKV vaccines has focused predominantly on the induction of neutralizing antibodies, although a suboptimal antibody response may theoretically enhance disease severity through antibody-dependent enhancement (ADE). Here, we report induction of a protective anti-ZIKV CD8+ T cell response in the HLA-B*0702 Ifnar1-/- transgenic mice using an alphavirus-based replicon RNA vaccine expressing ZIKV nonstructural protein NS3, a potent T cell antigen. The NS3 vaccine did not induce a neutralizing antibody response but elicited polyfunctional CD8+ T cells that were necessary and sufficient for preventing death in lethally infected adult mice and fetal growth restriction in infected pregnant mice. These data identify CD8+ T cells as the major mediators of ZIKV NS3 vaccine-induced protection and suggest a new strategy to develop safe and effective anti-flavivirus vaccines.

Spiking Pandemic Potential: Structural and Immunological Aspects of SARS-CoV-2.

SARS-Coronavirus-2 (SARS-CoV-2) causes Coronavirus disease 2019 (COVID-19), an infectious respiratory disease causing thousands of deaths and overwhelming public health systems. The international spread of SARS-CoV-2 is associated with the ease of global travel, and societal dynamics, immunologic naiveté of the host population, and muted innate immune responses. Based on these factors and the expanding geographic scale of the disease, the World Health Organization (WHO) declared the COVID-19 outbreak a pandemic-the first caused by a coronavirus. In this review, we summarize the current epidemiological status of COVID-19 and consider the virological and immunological lessons, animal models, and tools developed in response to prior SARS-CoV and MERS-CoV outbreaks that can serve as resources for development of SARS-CoV-2 therapeutics and vaccines. In particular, we discuss structural insights into the SARS-CoV-2 spike protein, a major determinant of transmissibility, and discuss key molecular aspects that will aid in understanding and fighting this new global threat.

Toward Nanotechnology-Enabled Approaches against the COVID-19 Pandemic.

The COVID-19 outbreak has fueled a global demand for effective diagnosis and treatment as well as mitigation of the spread of infection, all through large-scale approaches such as specific alternative antiviral methods and classical disinfection protocols. Based on an abundance of engineered materials identifiable by their useful physicochemical properties through versatile chemical functionalization, nanotechnology offers a number of approaches to cope with this emergency. Here, through a multidisciplinary Perspective encompassing diverse fields such as virology, biology, medicine, engineering, chemistry, materials science, and computational science, we outline how nanotechnology-based strategies can support the fight against COVID-19, as well as infectious diseases in general, including future pandemics. Considering what we know so far about the life cycle of the virus, we envision key steps where nanotechnology could counter the disease. First, nanoparticles (NPs) can offer alternative methods to classical disinfection protocols used in healthcare settings, thanks to their intrinsic antipathogenic properties and/or their ability to inactivate viruses, bacteria, fungi, or yeasts either photothermally or via photocatalysis-induced reactive oxygen species (ROS) generation. Nanotechnology tools to inactivate SARS-CoV-2 in patients could also be explored. In this case, nanomaterials could be used to deliver drugs to the pulmonary system to inhibit interaction between angiotensin-converting enzyme 2 (ACE2) receptors and viral S protein. Moreover, the concept of "nanoimmunity by design" can help us to design materials for immune modulation, either stimulating or suppressing the immune response, which would find applications in the context of vaccine development for SARS-CoV-2 or in counteracting the cytokine storm, respectively. In addition to disease prevention and therapeutic potential, nanotechnology has important roles in diagnostics, with potential to support the development of simple, fast, and cost-effective nanotechnology-based assays to monitor the presence of SARS-CoV-2 and related biomarkers. In summary, nanotechnology is critical in counteracting COVID-19 and will be vital when preparing for future pandemics.

CD4+ T Cells Cross-Reactive with Dengue and Zika Viruses Protect against Zika Virus Infection.

The underlying mechanisms by which prior immunity to dengue virus (DENV) affords cross-protection against the related flavivirus Zika virus (ZIKV) are poorly understood. Here, we examine the ability of DENV/ZIKV-cross-reactive CD4+ T cells to protect against versus exacerbate ZIKV infection by using a histocompatibility leukocyte antigen (HLA)-DRB1∗0101 transgenic, interferon α/ß receptor-deficient mouse model that supports robust DENV and ZIKV replication. By mapping the HLA-DRB1∗0101-restricted T cell response, we identify DENV/ZIKV-cross-reactive CD4+ T cell epitopes that stimulate interferon gamma (IFNγ) and/or tumor necrosis factor (TNF) production. Vaccination of naive HLA-DRB1∗0101 transgenic mice with these peptides induces a CD4+ T cell response sufficient to reduce tissue viral burden following ZIKV infection. Notably, this protective response requires IFNγ and/or TNF secretion but not anti-ZIKV immunoglobulin G (IgG) production. Thus, DENV/ZIKV-cross-reactive CD4+ T cells producing canonical Th1 cytokines can suppress ZIKV replication in an antibody-independent manner. These results may have important implications for increasing the efficacy and safety of DENV/ZIKV vaccines and for developing pan-flavivirus vaccines.

Human Polyclonal Antibodies Prevent Lethal Zika Virus Infection in Mice.

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus that represents a major threat to global health. ZIKV infections in adults are generally asymptomatic or present with mild symptoms. However, recent outbreaks of ZIKV have revealed that it can cause Congenital Zika Syndrome in neonates and Guillain-Barré syndrome in adults. Currently, no ZIKV-specific vaccines or antiviral treatments are available. In this study, we tested the efficacy of convalescent plasma IgG hyperimmune product (ZIKV-IG) isolated from individuals with high neutralizing anti-ZIKV titers as a therapeutic candidate against ZIKV infection using a model of ZIKV infection in Ifnar1-/- mice. ZIKV-IG successfully protected mice from lethal ZIKV challenge. In particular, ZIKV-IG treatment at 24 hours after lethal ZIKV infection improved survival by reducing weight loss and tissue viral burden and improving clinical score. Additionally, ZIKV-IG eliminated ZIKV-induced tissue damage and inflammation in the brain and liver. These results indicate that ZIKV-IG is efficacious against ZIKV, suggesting this human polyclonal antibody is a viable candidate for further development as a treatment against human ZIKV infection.

Correction: CD4+ T cells promote humoral immunity and viral control during Zika virus infection.

[This corrects the article DOI: 10.1371/journal.ppat.1007474.].

Detection of Zika virus in mouse mammary gland and breast milk.

Clinical reports of Zika Virus (ZIKV) RNA detection in breast milk have been described, but evidence conflicts as to whether this RNA represents infectious virus. We infected post-parturient AG129 murine dams deficient in type I and II interferon receptors with ZIKV. ZIKV RNA was detected in pup stomach milk clots (SMC) as early as 1 day post maternal infection (dpi) and persisted as late as 7 dpi. In mammary tissues, ZIKV replication was demonstrated by immunohistochemistry in multiple cell types including cells morphologically consistent with myoepithelial cells. No mastitis was seen histopathologically. In the SMC and tissues of the nursing pups, no infectious virus was detected via focus forming assay. However, serial passages of fresh milk supernatant yielded infectious virus, and immunohistochemistry showed ZIKV replication protein associated with degraded cells in SMC. These results suggest that breast milk may contain infectious ZIKV. However, breast milk transmission (BMT) does not occur in this mouse strain that is highly sensitive to ZIKV infection. These results suggest a low risk for breast milk transmission of ZIKV, and provide a platform for investigating ZIKV entry into milk and mechanisms which may prevent or permit BMT.

CD4+ T cells promote humoral immunity and viral control during Zika virus infection.

Several Zika virus (ZIKV) vaccines designed to elicit protective antibody (Ab) responses are currently under rapid development, but the underlying mechanisms that control the magnitude and quality of the Ab response remain unclear. Here, we investigated the CD4+ T cell response to primary intravenous and intravaginal infection with ZIKV. Using the LysMCre+Ifnar1fl/fl (myeloid type I IFN receptor-deficient) C57BL/6 mouse models, we identified six I-Ab-restricted ZIKV epitopes that stimulated CD4+ T cells with a predominantly cytotoxic Th1 phenotype in mice primed with ZIKV. Intravenous and intravaginal infection with ZIKV effectively induced follicular helper and regulatory CD4+ T cells. Treatment of mice with a CD4+ T cell-depleting Ab reduced the plasma cell, germinal center B cell, and IgG responses to ZIKV without affecting the CD8+ T cell response. CD4+ T cells were required to protect mice from a lethal dose of ZIKV after infection intravaginally, but not intravenously. However, adoptive transfer and peptide immunization experiments showed a role for memory CD4+ T cells in ZIKV clearance in mice challenged intravenously. These results demonstrate that CD4+ T cells are required mainly for the generation of a ZIKV-specific humoral response but not for an efficient CD8+ T cell response. Thus, CD4+ T cells could be important mediators of protection against ZIKV, depending on the infection or vaccination context.

Cross-reactive Dengue virus-specific CD8+ T cells protect against Zika virus during pregnancy.

As Zika virus (ZIKV) emerges into Dengue virus (DENV)-endemic areas, cases of ZIKV infection in DENV-immune pregnant women may rise. Here we show that prior DENV immunity affects maternal and fetal ZIKV infection in pregnancy using sequential DENV and ZIKV infection models. Fetuses in ZIKV-infected DENV-immune dams were normal sized, whereas fetal demise occurred in non-immune dams. Moreover, reduced ZIKV RNA is present in the placenta and fetuses of ZIKV-infected DENV-immune dams. DENV cross-reactive CD8+ T cells expand in the maternal spleen and decidua of ZIKV-infected dams, their depletion increases ZIKV infection in the placenta and fetus, and results in fetal demise. The inducement of cross-reactive CD8+ T cells via peptide immunization or adoptive transfer results in decreased ZIKV infection in the placenta. Prior DENV immunity can protect against ZIKV infection during pregnancy in mice, and CD8+ T cells are sufficient for this cross-protection. This has implications for understanding the natural history of ZIKV in DENV-endemic areas and the development of optimal ZIKV vaccines.

Dengue virus-reactive CD8+ T cells mediate cross-protection against subsequent Zika virus challenge.

Zika virus (ZIKV) and dengue virus (DENV) are antigenically related flaviviruses that share cross-reactivity in antibody and T cell responses, and co-circulate in increasing numbers of countries. Whether pre-existing DENV immunity can cross-protect or enhance ZIKV infection during sequential infection of the same host is unknown. Here, we show that DENV-immune Ifnar1 -/- or wild-type C57BL/6 mice infected with ZIKV have cross-reactive immunity to subsequent ZIKV infection and pathogenesis. Adoptive transfer and cell depletion studies demonstrate that DENV-immune CD8+ T cells predominantly mediate cross-protective responses to ZIKV. In contrast, passive transfer studies suggest that DENV-immune serum does not protect against ZIKV infection. Thus, CD8+ T cell immunity generated during primary DENV infection can confer protection against secondary ZIKV infection in mice. Further optimization of current DENV vaccines for T cell responses might confer cross-protection and prevent antibody-mediated enhancement of ZIKV infection.

A Mouse Model of Zika Virus Sexual Transmission and Vaginal Viral Replication.

Case reports of Zika virus (ZIKV) sexual transmission and genital persistence are mounting. Venereal transmission and genital persistence threaten public health within and beyond the range of ZIKV's mosquito vectors. In this study, we administered ZIKV into the vaginas of AG129 mice and LysMCre+IFNARfl/fl C57BL/6 mice after hormonal treatments. Mice infected during estrus-like phase were resistant to vaginal infection. In contrast, when infected during diestrus-like phase, AG129 mice succumbed to infection, whereas LysMCre+IFNARfl/fl mice experienced transient illness. Patency of transgenital transmission (TGT) in diestrus-like mice was demonstrated by detection of viremia and ZIKV replication in spleen and brain, and viral RNA persisted in vaginal washes as late as 10 days post-infection. In these lethal and sublethal mouse models, this study indicates that intravaginal deposition of ZIKV can cause TGT, hormonal changes in the female reproductive tract (FRT) influence transmission, and ZIKV replication persists in the FRT for several days.