Cells in Dengue Virus Infection In Vivo

Dengue has been recognized as one of the most important vector-borne emerging infectious diseases globally. Though dengue normally causes a self-limiting infection, some patients may develop a life-threatening illness, dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS). The reason why DHF/DSS occurs in certain individuals is unclear. Studies in the endemic regions suggest that the preexisting antibodies are a risk factor for DHF/DSS. Viremia and thrombocytopenia are the key clinical features of dengue virus infection in patients. The amounts of virus circulating in patients are highly correlated with severe dengue disease, DHF/DSS. Also, the disturbance, mainly a transient depression, of hematological cells is a critical clinical finding in acute dengue patients. However, the cells responsible for the dengue viremia are unresolved in spite of the intensive efforts been made. Dengue virus appears to replicate and proliferate in many adapted cell lines, but these in vitro properties are extremely difficult to be reproduced in primary cells or in vivo. This paper summarizes reports on the permissive cells in vitro and in vivo and suggests a hematological cell lineage for dengue virus infection in vivo, with the hope that a new focus will shed light on further understanding of the complexities of dengue disease

SARS-CoV-2 Antibody Profiles in Maternal Serum and Breast Milk Following mRNA COVID-19 Vaccination: A Longitudinal Prospective Observational Cohort Study

COVID-19 vaccination during pregnancy protects infants against symptomatic COVID-19. Vaccination of lactating mothers may offer additional protection, but our understanding of immune responses in breast milk is limited. We, therefore, performed a single-center prospective cohort study of lactating mothers who received a COVID-19 mRNA primary vaccine series to evaluate the durability, breadth, and neutralizing capacity of the antibody responses in breast milk. Spike IgG- and IgA-binding antibodies of ancestral SARS-CoV-2 in serum and breast milk were quantified over 9 months using Meso Scale Discovery (MSD) V-PLEX assays, and ancestral titers were compared to four variants of concern (Alpha, Beta, Delta, Gamma) at a single time point. Neutralizing antibodies against ancestral SARS-CoV-2 and Omicron BA.4/5 were compared before and after vaccination using a pseudovirus-neutralization assay. Eleven lactating mothers received either Pfizer BNT162b2 (7/11) or Moderna mRNA-1273 (4/11) vaccine primary series. IgG and IgA titers increased in serum and breast milk following each dose, peaking 1–4 weeks after series completion. Titers remained significantly elevated for 7–9 months, except for in breast milk IgA which returned to baseline within 1 month. Furthermore, binding antibodies against all included variants were detected in breast milk collected 1–3 weeks after series completion. However, while vaccination induced a strong neutralizing response against ancestral SARS-CoV-2 in serum and more modest response in breast milk, it did not induce neutralizing antibodies against Omicron BA.4/5 in either specimen type. This study demonstrates that maternal COVID-19 mRNA vaccination may enhance immune protection for infants through breast milk via increased IgG- and IgA-binding-and-neutralizing antibodies; although, variant-specific boosters may be required to optimize immune protection

Multiploid CD61+ Cells Are the Pre-Dominant Cell Lineage Infected during Acute Dengue Virus Infection in Bone Marrow

<div><p>Depression of the peripheral blood platelet count during acute infection is a hallmark of dengue. This thrombocytopenia has been attributed, in part, to an insufficient level of platelet production by megakaryocytes that reside in the bone marrow (BM). Interestingly, it was observed that dengue patients experience BM suppression at the onset of fever. However, few studies focus on the interaction between dengue virus (DENV) and megakaryocytes and how this interaction can lead to a reduction in platelets. In the studies reported herein, BM cells from normal healthy rhesus monkeys (RM) and humans were utilized to identify the cell lineage(s) that were capable of supporting virus infection and replication. A number of techniques were employed in efforts to address this issue. These included the use of viral RNA quantification, nonstructural protein and infectivity assays, phenotypic studies utilizing immunohistochemical staining, anti-differentiation DEAB treatment, and electron microscopy. Cumulative results from these studies revealed that cells in the BM were indeed highly permissive for DENV infection, with human BM having higher levels of viral production compared to RM. DENV-like particles were predominantly observed in multi-nucleated cells that expressed CD61+. These data suggest that megakaryocytes are likely the predominant cell type infected by DENV in BM, which provides one explanation for the thrombocytopenia and the dysfunctional platelets characteristic of dengue virus infection.</p> </div

Megakaryocytes were likely the dominant dengue virus antigen positive cells in monkey bone marrow.

<p>Smears of bone marrow cells were prepared and immunohistochemical stainings were performed as described in Methods. Dengue antigen (4G2 positivity) is indicated by DAB staining (brown) (A) Dengue viral antigen in a diploid megakaryocyte. (B) Dengue antigen in a multi-lobulated megakaryocyte. (C), Dengue antigen in cellular debris. Red, PAS staining. Blue, hematoxylin staining. (D and E) Dengue viral antigen-containing vesicles engulfed by phagocytic cells. (F) Isotype control.</p

CD61+ cells were the early cells infected by dengue virus bone marrow.

<p>Freshly aspirated bone marrows at various time points from DV infected rhesus monkeys were stained with dengue viral specific monoclonal antibody (clone 3H5) and cell lineage markers CD41, CD61, and CD14, and subjected to FACS analysis. Results revealed that viral antigen was observed early in CD61+ cells with a decreasing trend while the opposite trend was evident in CD14+ monocytic cells.</p

Human bone marrow is more permissive than rhesus macaque bone marrow to dengue virus infection in vitro.

<p>(A) A comparison of peak virus genome copy number levels in human and monkey BM cultures. (B) Comparison of NS1 in the supernatant fluid of human and monkey BMs. The levels of viral RNA and NS1 in the supernatant fluid from infected human BM were significantly higher than that from the rhesus monkey.</p

Human bone marrow is permissive for dengue virus infection in vitro.

<p>Healthy human BM cells were obtained from the BM transplantation center at Emory University and infected with dengue virus as described in the Methods. Supernatant fluids were collected at the indicated times; viral RNA and NS1 were quantified as described in the Methods. (A) Viral RNA in supernatant fluids. (B) NS1 in supernatant fluids.</p

Quantification of monkey bone marrow cells positive for dengue viral antigen^a.

a<p>values represent the percentage of surface marker positive or negative among 200 dengue positive (4G2+) cells with 3–5 histochemical stainings.</p><p>± standard deviation, P.I., post-infection, BDCA2, plasmacytoid dendritic cell antigen 2.</p