Summary A major obstacle to tuberculosis (TB) control is the problem of chronic TB infection (CTBI). NOS2-/-and gp91phox -/-mice given aminoguanidine [to suppress the effects of nitric oxide synthase 2 (NOS2)] -indicating minimal metabolic effect on the cysH mutant survival in these mice. The cysH mutant was also susceptible to peroxynitrite and hydrogen peroxide in vitro . These results show that CysH is important for Mtb protection during the chronic infection phase, and that resistance to nitrosative and oxidative stress may be the mechanism of this protection. Thus, this metabolic gene of an intracellular pathogen could have a secondary role in protection against the host immune response. Finally the lack of an endogenous human orthologue of cysH and its possible role in defence against adaptive immunity renders CysH an attractive enzyme for further studies as a target for therapeutics active against CTBI.

Animal models of Zika virus (ZIKV) are needed to better understand tropism and pathogenesis and to test candidate vaccines and therapies to curtail the pandemic. Humans and rhesus macaques possess similar fetal development and placental biology that is not shared between humans and rodents. We inoculated 2 non-pregnant rhesus macaques with a 2015 Brazilian ZIKV strain. Consistent with most human infections, the animals experienced no clinical disease but developed short-lived plasma viremias that cleared as neutralizing antibody developed. In 1 animal, viral RNA (vRNA) could be detected longer in whole blood than in plasma. Despite no major histopathologic changes, many adult tissues contained vRNA 14 days post-infection with highest levels in hemolymphatic tissues. These observations warrant further studies to investigate ZIKV persistence and its potential clinical implications for transmission via blood products or tissue and organ transplants.

Zika virus (ZIKV) infection of pregnant women can cause fetal microcephaly and other neurologic defects. We describe the development of a non-human primate model to better understand fetal pathogenesis. To reliably induce fetal infection at defined times, four pregnant rhesus macaques are inoculated intravenously and intraamniotically with ZIKV at gestational day (GD) 41, 50, 64, or 90, corresponding to first and second trimester of gestation. The GD41-inoculated animal, experiencing fetal death 7 days later, has high virus levels in fetal and placental tissues, implicating ZIKV as cause of death. The other three fetuses are carried to near term and euthanized; while none display gross microcephaly, all show ZIKV RNA in many tissues, especially in the brain, which exhibits calcifications and reduced neural precursor cells. Given that this model consistently recapitulates neurologic defects of human congenital Zika syndrome, it is highly relevant to unravel determinants of fetal neuropathogenesis and to explore interventions.

Increased mucus production in asthma is an important cause of airflow obstruction during severe exacerbations. To better understand the changes in airway epithelium that lead to increased mucus production, ovalbumin-sensitized and -challenged mice were used. The phenotype of the epithelium was dramatically altered, resulting in increased numbers of mucous cells, predominantly in the proximal airways. However, the total numbers of epithelial cells per unit area of basement membrane did not change. A 75% decrease in Clara cells and a 25% decrease in ciliated cells were completely compensated for by an increase in mucous cells. Consequently, by day 22, 70% of the total epithelial cell population in the proximal airways was mucous cells. Electron microscopy illustrated that Clara cells were undergoing metaplasia to mucous cells. Conversely, epithelial proliferation, detected with 5-chloro-2-deoxyuridine immunohistochemistry, was most marked in the distal airways. Using ethidium homodimer cell labeling to evaluate necrosis and terminal dUTP nick-end labeling immunohistochemistry to evaluate apoptosis, this proliferation was accompanied by negligible cell death. In conclusion, epithelial cell death did not appear to be the stimulus driving epithelial proliferation and the increase in mucous cell numbers was primarily a result of Clara cell metaplasia. (Am J

CD4 T follicular helper (Tfh) cells are important for the generation of durable and specific humoral protection against viral infections. The degree to which SARS-CoV-2 infection generates Tfh cells and stimulates the germinal center (GC) response is an important question as we investigate vaccine induced immunity against COVID-19. Here, we report that SARS-CoV-2 infection in rhesus macaques, either infused with convalescent plasma, normal plasma, or receiving no infusion, resulted in transient accumulation of pro-inflammatory monocytes and proliferating Tfh cells with a Th1 profile in peripheral blood. CD4 helper cell responses skewed predominantly toward a Th1 response in blood, lung, and lymph nodes. SARS-CoV-2 Infection induced GC Tfh cells specific for the SARS-CoV-2 spike and nucleocapsid proteins, and a corresponding early appearance of antiviral serum IgG antibodies. Collectively, the data show induction of GC responses in a rhesus model of mild COVID-19.

Polysialic acid (polySia) is a large glycan with restricted expression, typically found attached to the protein scaffold neural cell adhesion molecule (NCAM). PolySia is best known for its proposed role in modulating neuronal development. Its presence and potential functions outside the nervous systems are essentially unexplored. Herein we show the expression of polySia on hematopoietic progenitor cells, and demonstrate a role for this glycan in immune response using both acute inflammatory and tumor models. Specifically, we found that human NK cells modulate expression of NCAM and the degree of polymerization of its polySia glycans according to activation state. This contrasts with the mouse, where polySia and NCAM expression are restricted to multipotent hematopoietic progenitors and cells developing along a myeloid lineage. Sialyltransferase 8Sia IV−/− mice, which lacked polySia expression in the immune compartment, demonstrated an increased contact hypersensitivity response and decreased control of tumor growth as compared with wild-type animals. This is the first demonstration of polySia expression and regulation on myeloid cells, and the results in animal models suggest a role for polySia in immune regulation.

The Mycobacterium tuberculosis genome contains four copies of an operon called mce (mce1-4). Previously we reported that M. tuberculosis disrupted in the mce1 operon is more virulent than wild-type M. tuberculosis in mice. We generated single deletion mutants in mce3 (Dmce3) and mce4 (Dmce4) operons and a double deletion mutant (Dmce3/4). Similar doubling times and growth characteristics were observed for all mutants and the wild-type (parent) M. tuberculosis H37Rv strain in culture and in macrophages. In addition, similar bacterial burdens were detected in organs from mice infected with Dmce3 and the parent strain. However, the bacterial burdens of mice infected with Dmce4 and Dmce 3/4 were less than those of mice infected with the parent strain. The median survival times of mice infected with wild-type M. tuberculosis, Dmce3, Dmce4 and Dmce3/4 were 40.5, 46, 58 and 62 weeks, respectively. Histopathological examination of lungs at 15 weeks post-infection showed that the extent of the lung lesions was less prominent in mice infected with Dmce4 and Dmce 3/4 mutants than in mice infected with the other two strains. These observations suggest that the mce3 and mce4 operons have a role distinct from that of mce1 for in vivo survival of M. tuberculosis.

Psoriasis is a chronic autoimmune disease affecting the skin and characterized by aberrant keratinocyte proliferation and function. Immune cells infiltrate the skin and release proinflammatory cytokines that play important roles in psoriasis. The Th17 network, including IL-23 and IL-22, has recently emerged as a critical component in the pathogenesis of psoriasis. IL-22 and IL-23 signaling is dependent on the JAK family of protein tyrosine kinases, making Janus kinase (JAK) inhibition an appealing strategy for the treatment of psoriasis. Here we report the activity of SAR-20347, a small molecule inhibitor with specificity for JAK1 and Tyrosine Kinase 2 (TYK2) over other JAK family members. In cellular assays, SAR-20347 dose-dependently (1 nM-10 μM) inhibited JAK1 and/or TYK2 dependent signaling from the IL-12/IL-23, IL-22, and IFN-α receptors. In vivo, TYK2 mutant mice or treatment of wild type mice with SAR-20347 significantly reduced IL-12 induced IFN-γ production and IL-22-dependent Serum Amyloid A (SAA) to similar extents, indicating that in these models, SAR-20347 is probably acting through inhibition of TYK2. In an imiquimod-induced psoriasis model, the administration of SAR-20347 led to a striking decrease in disease pathology, including reduced activation of keratinocytes, and proinflammatory cytokine levels compared to both TYK2 mutant mice and wild type controls. Taken together, these data indicate that targeting both JAK1 and TYK2-mediated cytokine signaling is more effective than TYK2 inhibition alone in reducing psoriasis pathogenesis.