Days Post-infection Research Articles

The Type VII Secretion System (T7SSb) contributes to interbacterial competition in a murine model of Group BStreptococcus gastrointestinal colonization

Abstract Background Late-onset (LO) disease caused by Group B Streptococcus (GBS) infection is a significant source of morbidity and mortality in neonates. It is believed that gastrointestinal (GI) colonization with GBS plays an important role in the progression to LO disease, although the host-microbial interactions that facilitate GBS GI colonization are poorly understood. The Type VII secretion system (T7SSb) has been identified in several gram-positive bacteria, and its function depends on a membrane-bound ATPase (EssC) which drives secretion of virulence factors. In GBS, the T7SSb has been shown to contribute to vaginal colonization and brain cytotoxicity. We aimed to identify the role of the T7SSb in GBS GI colonization using a murine model and hypothesize that the T7SSb is necessary for sustained GBS GI colonization. Methods Two bacterial strains were used, a wild-type (WT) GBS of A909 background (serotype Ia) and an isogenic T7SSb mutant GBS strain (essC::Himar1, transposon inserted). Monocolonization and co-cocolonization experiments were performed by orally inoculating preweaning C57BL/6J mice (12-14 days of life) with one or both strains, respectively. Euthanasia was performed, rectal swabs collected, and the GI tract harvested at day 7 post infection. For co-colonization experiments, competitive indices were calculated at day 7 post infection to determine the contribution of T7SSb to GBS GI colonization. For monocolonization experiments, colonization status and bacterial burden at day 7 post infection were measured. Results In cocolonization, WT GBS A909 outcompeted the essC::Himar1 mutant at 7-days post infection with a geometric mean competitive index of 8.8, 95% CI [0.2, 350.1] by rectal swab; 35.7, 95% CI [19.2, 66.3] in the small intestine; 87.6, 95% CI [18.9, 407] in the cecum; and 91.7, 95% CI [33.4, 252] in the colon (Figure 1a). In monocolonization, we noted similar rates of colonization (p=NS, Fisher’s exact test) (Figure 1b) and no difference in bacterial burden (p=NS, 2-way ANOVA test) (Figure 1c) across the GI tract at 7 days post infection. Conclusion Our results suggest that T7SSb plays an important role in GBS bacterial competition in the GI tract but is likely not an essential factor for GBS GI colonization. Further exploration of the role of the T7SSb in interbacterial competition may yield relevant information regarding GI colonization dynamics. Figure 1. Establishing the role of T7SSb in a murine model of GI colonization. (a) Wild type (WT) A909 confers an advantage over an isogenic T7SSb mutant (essC::Himar1) strain in a cocolonization model. Data points represent geometric mean competition indices and error bars represent 95% confidence interval. (b) Colonization status by WT A909 and essC::Himar1 mutant in the GI tract 7-days post infection in monocolonization experiments (p-values represent two-sided Fisher’s exact test). (c) Bacterial burden of monocolonization by WT A909 and essC::Himar1 mutant in the GI tract 7-days post infection (p-values represent 2-way ANOVA test).

Acute Toxicity and IN VIVO Antischistosomal Effects of Entada africana Guill & Perott (Fabaceae) Methanol Stem Bark Extract in Albino Mice

The study was aimed at determining the acute toxicity and schistosomicidal effects of methanol extract (ME) of Entada africana (E. africana), in albino mice. Fresh stem bark of E. africana was shade-dried and extracted by Soxhlet extraction. Acute toxicity was carried out on 6 groups of mice (n=3) of 6-week-old, sizes 27-30g; to determine the therapeutic index, piloerection signs and possible mortality (LD50) in 24h exposure period. Cercaria from B. globosus snails were shed under a 100W bulb for 2 hours. In vivo antischistosomal assays was by used of 6-weeks old (27-30g) mice. Set I (n=10) involved investigation on schistosomules infection in the mice, 3-7 days post infection (PI). Set II (n=10) was infected and treated with E. africana ME extract, at concentrations 10-100mg/l, 35th day, PI for 5 consecutive days. Set III (n=10), were infected and treated with praziquantel– PZQ (positive control). While set IV (n=10) were infected and untreated (negative control). All were sacrificed, 75th day of PI. Data were analyzed by GraphPad® prism 8.4, version 2020. Findings revealed that E. africana ME did not generate any harmful or clinical effect within 24h, post administration; and there were no obvious reactions such as paw licking, stooling, piloerection or immediate death, except at phase II, 5000mg/kg bwt, (1⁄3) being the highest dosage. Worm burden decreased with increase in concentrations, especially at 70-100mg/l. Lower concentrations (10mg/l), had high worm population (76.00±21.28). Infected and untreated group had highest worm population (189.67±32.52). E. africana ME stem bark extract, showed antischistosomal effect and worm reduction in a dose- dependent pattern.

IL-6 deficiency accelerates cerebral cryptococcosis and alters glial cell responses

Cryptococcus neoformans (Cn) is an opportunistic encapsulated fungal pathogen that causes life-threatening meningoencephalitis in immunosuppressed individuals. Since IL-6 is important for blood-brain barrier support and its deficiency has been shown to facilitate Cn brain invasion, we investigated the impact of IL-6 on systemic Cn infection in vivo, focusing on central nervous system (CNS) colonization and glial responses, specifically microglia and astrocytes. IL-6 knock-out (IL-6−/−) mice showed faster mortality than C57BL/6 (Wild-type) and IL-6−/− supplemented with recombinant IL-6 (rIL-6; 40 pg/g/day) mice. Despite showing early lung inflammation but no major histological differences in pulmonary cryptococcosis progression among the experimental groups, IL-6−/− mice had significantly higher blood and brain tissue fungal burden at 7-days post infection. Exposure of cryptococci to rIL-6 in vitro increased capsule growth. In addition, IL-6−/− brains were characterized by an increased dystrophic microglia number during Cn infection, which are associated with neurodegeneration and senescence. In contrast, the brains of IL-6-producing or -supplemented mice displayed high numbers of activated and phagocytic microglia, which are related to a stronger anti-cryptococcal response or tissue repair. Likewise, culture of rIL-6 with microglia-like cells promoted high fungal phagocytosis and killing, whereas IL-6 silencing in microglia decreased fungal phagocytosis. Lastly, astrogliosis was high and moderate in infected brains removed from Wild-type and IL-6−/− supplemented with rIL-6 animals, respectively, while minimal astrogliosis was observed in IL-6−/− tissue, highlighting the potential of astrocytes in containing and combating cryptococcal infection. Our findings suggest a critical role for IL-6 in Cn CNS dissemination, neurocryptococcosis development, and host defense.

Nasally delivered chitosan-coated poly(lactide-co-glycolide) encapsulating honeybee venom enhances T helper 1-related immunity against Salmonella Typhimurium infection in pigs.

Salmonella Typhimurium is a significant zoonotic concern for human food poisoning and a substantial economic burden in the swine industry. We previously reported that nasally delivered chitosan-coated poly(lactide-co-glycolide) (PLGA) encapsulating honeybee venom (CP-HBV) could enhance CD4+ T helper 1 (Th1)-related immune responses in healthy pigs. Building upon these findings, the current study aimed to investigate the protective immune enhancement by nasally delivered CP-HBV in pigs challenged with S Typhimurium. 36 healthy, 4-week-old, female, Landrace X Yorkshire X Duroc pigs. 36 pigs were allocated into 3 groups: CP-HBV (n = 16), control (n = 16), and healthy baseline control (n = 4). CP-HBV and control groups were challenged with S Typhimurium 7 days post-treatment. Pigs from the healthy control group were sacrificed at 0 days postinfection (DPI), and 4 pigs from each of the control and CP-HBV groups were sacrificed at 1, 2, 4, and 7 DPI. Salmonella shedding, immune cell frequencies, cytokines, and transcriptional factor expression levels were measured. The CP-HBV group exhibited lower bacterial shedding and an enhanced Th1-related immune response characterized by an upregulation of CD4+ T cells and CD4+ Interferon-γ+ T cells, accompanied by increased expression of Th1-related cytokines and reduced expression of regulatory T cells and immunosuppressive cytokines compared to the control group. CP-HBV is a promising strategy for controlling Salmonella infections in pigs and improving public health.

Competitive exclusion products as an antimicrobial alternative to control Salmonella Heidelberg in broilers.

Intestinal infections caused by non-typhoidal Salmonella spp., along with antimicrobial resistance spread are a major food safety concern worldwide. Here, we evaluate the potential of competitive exclusion products developed by anaerobic or aerobic conditions to control systemic infection, cecal colonization, fecal excretion, and improve the intestinal health in broilers challenged by Salmonella Heidelberg (SH). A total of 105 day-old chickens were randomly distributed into three experimental groups: A (untreated control), B (treated with anaerobic culture), and C (treated with aerobic culture). During 21 days, morphometric parameters of the small intestine were analyzed using microscopy, fecal excretions by cloacal swabs, systemic infection, and cecal colonization by colony-forming unit counts (CFU/g). The results indicated the lowest number of positive swabs (45.33%) recovered from Group C, followed by Group B (71.8%) and Group A (85.33%). The bacterial enumeration revealed the lowest amounts in Group C at the necropsy realized in 5-, 7-, and 14-days post-infection (DPI) (P=0.0010, P=0.0048, and P=0.0094, respectively). Statistical differences between intestinal morphometrics were observed in the Group C at 21 DPI. Our results suggest that the product developed under aerobic conditions can improve intestinal health, protecting birds against SH.

Prevalence Study of Trichomonas gallinae in Domestic Pigeons in Northeastern Beijing and Experimental Model of Trichomoniasis in White King Squabs Measuring In Situ Apoptosis and Immune Factors in Crop and Esophagus.

Trichomonas gallinae (T. gallinae) is a flagellated protozoan and the causative agent of trichomoniasis, or canker, in birds. In the current study, the prevalence of T. gallinae was firstly investigated in five breeds. According to the results of the prevalence study, White King pigeons were selected as the experimental animals. A total of 135 White King squabs at one day of age were randomly divided into two groups and raised in separate isolators. The challenged group (N = 100) was challenged intranasally with 5 × 106 parasites/mL of the T. gallinae strain, and the control group (N = 35) was intranasally administered medium of equivalent volume. At 1, 2, 3 and 5 days post infection (DPIs), the crops and esophagi were collected for RNA extraction and formaldehyde fixation. The results showed that prevalence of T. gallinae in the five breeds ranged from 27.13% (White Carneau) to 43.14% (White King). After the challenge, mild microscopic lesions were observed in both tissues. Apoptosis rates were higher in the challenged group than in the control group at 2 and 5 DPIs in the crop and at 1, 2 and 7 DPIs in the esophagus. For both tissues, relative expression of IL-1β increased dramatically at the beginning and decreased at 5 DPIs, and TGF-β increased stably in the challenged group.

MicroRNA expression profile of chicken liver at different times after Histomonas meleagridis infection

Histomonas meleagridis, an anaerobic intercellular parasite, is known to infect gallinaceous birds, particularly turkeys and chickens. The resurgence of histomonosis in recent times has resulted in significant financial setbacks due to the prohibition of drugs used for disease treatment. Currently, research on about H. meleagridis primarily concentrate on the examination of its virulence, gene expression analysis, and the innate immunity response of the host organism. However, there is a lack of research on differentially expressed miRNAs (DEMs) related to liver infection induced by H. meleagridis. In this study, the weight gain and pathological changes at various post-infection time points were evaluated through animal experiments to determine the peak and early stages of infection. Next, High-throughput sequencing was used to examine the expression profile of liver miRNA at 10 and 15 days post-infection (DPI) in chickens infected with the Chinese JSYZ-F strain of H. meleagridis. A comparison with uninfected controls revealed the presence of 120 and 118 DEMs in the liver of infected chickens at 10 DPI and 15 DPI, respectively, with 74 DEMs being shared between the two time points. Differentially expressed microRNAs (DEMs) were categorized into three groups based on the time post-infection. The first group (L1) includes 45 miRNAs that were differentially expressed only at 10 DPI and were predicted to target 1646 genes. The second group (L2) includes 43 miRNAs that were differentially expressed only at 15 DPI and were predicted to target 2257 genes. The third group (L3) includes 75 miRNAs that were differentially expressed at both 10 DPI and 15 DPI and were predicted to target 1623 genes. At L1, L2, and L3, there were 89, 87, and 41 significantly enriched Gene Ontology (GO) terms, respectively (p<0.05). The analysis of differentially expressed miRNA target genes using KEGG pathways revealed significant enrichment at L1, L2, and L3, with 3, 4, and 5 pathways identified, respectively (p<0.05). This article suggests that the expression of liver miRNA undergoes dynamic alterations due to H. meleagridis and the host. It showed that the expression pattern of L1 class DEMs was more conducive to regulating the development of the inflammatory response, while the L2 class DEMs were more conducive to augmenting the inflammatory response. The observed patterns of miRNA expression associated with inflammation were in line with the liver's inflammatory process following infection. The results of this study provide a basis for conducting a comprehensive analysis of the pathogenic mechanism of H. meleagridis from the perspective of host miRNAs.

Trypanosoma vivax in and outside cattle blood: Parasitological, molecular, and serological detection, reservoir tissues, histopathological lesions, and vertical transmission evaluation

This study reports assessment of the sensitivity of diagnostic techniques to detect T. vivax in experimentally infected cattle. Additionally, it describes T. vivax extravascular parasitism during the acute and chronic phases of trypanosomosis and congenital transmission. The T. vivax diagnosis was compared using blood samples collected from the jugular, coccygeal and ear tip veins. For this study, 13 males and two females were infected with ≈ 1 × 106 viable T. vivax trypomastigotes (D0). One animal was kept as a negative control during the entire study. The 13 infected males were euthanized between 14 and 749 days post-infection (DPI). After confirming the cyclicity of both females (9 months of age), they were naturally mated with a bull. One female was euthanized at 840 DPI, and the other at 924 DPI. The two calves, one from each female, were euthanized at six months of age (924 DPI), and the negative control at 924 DPI. During this period, T. vivax in blood was assessed using direct methods (Woo test, cPCR, microscopic examination of fresh wet blood films and parasite quantification - Brener method), and serological methods (IFAT, ELISA, and IA). Tissue samples were collected from the liver, spleen, brain, cerebellum, heart, testicles, epididymis, kidneys, eyeballs, pre-scapular lymph nodes, ear tips, mammary glands, uterus, and ovaries. The protozoan DNA was examined using LAMP. There was no difference in the detection of T. vivax using the Woo test and Brener method among the jugular, coccygeal, and ear tip veins. The sensitivity of the detection methods varied depending on the disease phase. Direct methods (Woo test, Brener method, and cPCR) demonstrated higher sensitivity during the acute phase, while serological methods (IFAT, ELISA, and IA) were more sensitive during the chronic phase. Anti-T. vivax antibodies were detected up to 924 DPI. Tissue evaluation using LAMP demonstrated the presence of T. vivax DNA and associated histopathological changes up to 840 or 924 DPI. Only in mammary glands and ovaries was no DNA detected. The most frequently observed histopathological alteration was lymphohistioplasmocytic inflammatory infiltrate. No transplacental transmission of T. vivax was observed.

Lipid nanoparticle composition for adjuvant formulation modulates disease after influenza virus infection in quadrivalent influenza vaccine vaccinated mice.

There are considerable avenues through which currently licensed influenza vaccines could be optimized. We tested influenza vaccination in a mouse model with two adjuvants: Sendai virus-derived defective interfering (SDI) RNA, a RIG-I agonist; and an amphiphilic imidazoquinoline (IMDQ-PEG-Chol), a TLR7/8 agonist. The negatively charged SDI RNA was formulated into lipid nanoparticles (LNPs) facilitating direct delivery of SDI RNA to the cytosol, where RIG-I sensing induces inflammatory and type I interferon responses. We previously tested SDI RNA and IMDQ-PEG-Chol as standalone and combination adjuvants for influenza and SARS-CoV-2 vaccines. Here, we tested two different ionizable lipids, K-Ac7-Dsa and S-Ac7-Dog, for LNP formulations. The LNPs were incorporated with SDI RNA to determine its potential as a combination adjuvant with IMDQ-PEG-Chol by evaluating the host immune response to vaccination and infection in immunized BALB/c mice. Adjuvanticity of IMDQ-PEG-Chol with and without empty or SDI-loaded LNPs was validated with quadrivalent inactivated influenza vaccine (QIV), showing robust induction of antibody titers and T-cell responses. Depending on the adjuvant combination and LNP formulation, humoral and cellular vaccine responses could be tailored towards type 1 or type 2 host responses with specific cytokine profiles that correlated with the protective responses to viral infection. The extent of protection conferred by different vaccine/LNP/adjuvant combinations was tested by challenging mice with a vaccine-matched strain of influenza A virus A/Singapore/gp1908/2015 IVR-180 (H1N1). Groups that received either LNP formulated with SDI or IMDQ-PEG-Chol, or both, showed very low levels of viral replication in their lungs at 5 days post-infection (DPI). These studies provide evidence that the combination of vaccines with LNPs and/or adjuvants promote antigen-specific cellular responses that can contribute to protection upon infection. Interestingly, we observed differences in humoral and cellular responses to vaccination between different groups receiving K-Ac7-Dsa or S-Ac7-Dog lipids in LNP formulations. The differences were also reflected in inflammatory responses in lungs of vaccinated animals to infection, depending on LNP formulations. Therefore, this study suggests that the composition of the LNPs, particularly the ionizable lipid, plays an important role in inducing inflammatory responses in vivo, which is important for vaccine safety and to prevent adverse effects upon viral exposure.

Overview of Modern Commercial Kits for Laboratory Diagnosis of African Swine Fever and Swine Influenza A Viruses.

Rapid and early detection of infectious diseases in pigs is important, especially for the implementation of control measures in suspected cases of African swine fever (ASF), as an effective and safe vaccine is not yet available in most of the affected countries. Additionally, analysis for swine influenza is of significance due to its high morbidity rate (up to 100%) despite a lower mortality rate compared to ASF. The wide distribution of swine influenza A virus (SwIAV) across various countries, the emergence of constantly new recombinant strains, and the danger of human infection underscore the need for rapid and accurate diagnosis. Several diagnostic approaches and commercial methods should be applied depending on the scenario, type of sample and the objective of the studies being implemented. At the early diagnosis of an outbreak, virus genome detection using a variety of PCR assays proves to be the most sensitive and specific technique. As the disease evolves, serology gains diagnostic value, as specific antibodies appear later in the course of the disease (after 7-10 days post-infection (DPI) for ASF and between 10-21 DPI for SwIAV). The ongoing development of commercial kits with enhanced sensitivity and specificity is evident. This review aims to analyse recent advances and current commercial kits utilised for the diagnosis of ASF and SwIAV.

Human surfactant protein A inhibits SARS-CoV-2 infectivity and alleviates lung injury in a mouse infection model.

SARS coronavirus 2 (SARS-CoV-2) infects human angiotensin-converting enzyme 2 (hACE2)-expressing lung epithelial cells through its spike (S) protein. The S protein is highly glycosylated and could be a target for lectins. Surfactant protein A (SP-A) is a collagen-containing C-type lectin, expressed by mucosal epithelial cells and mediates its antiviral activities by binding to viral glycoproteins. This study examined the mechanistic role of human SP-A in SARS-CoV-2 infectivity and lung injury in vitro and in vivo. Human SP-A can bind both SARS-CoV-2 S protein and hACE2 in a dose-dependent manner (p<0.01). Pre-incubation of SARS-CoV-2 (Delta) with human SP-A inhibited virus binding and entry and reduced viral load in human lung epithelial cells, evidenced by the dose-dependent decrease in viral RNA, nucleocapsid protein (NP), and titer (p<0.01). We observed significant weight loss, increased viral burden, and mortality rate, and more severe lung injury in SARS-CoV-2 infected hACE2/SP-A KO mice (SP-A deficient mice with hACE2 transgene) compared to infected hACE2/mSP-A (K18) and hACE2/hSP-A1 (6A2) mice (with both hACE2 and human SP-A1 transgenes) 6 Days Post-infection (DPI). Furthermore, increased SP-A level was observed in the saliva of COVID-19 patients compared to healthy controls (p<0.05), but severe COVID-19 patients had relatively lower SP-A levels than moderate COVID-19 patients (p<0.05). Collectively, human SP-A attenuates SARS-CoV-2-induced acute lung injury (ALI) by directly binding to the S protein and hACE2, and inhibiting its infectivity; and SP-A level in the saliva of COVID-19 patients might serve as a biomarker for COVID-19 severity.

N-3 enriched Fish oil diet enhanced intestinal barrier integrity in broilers after Eimeria infection

Coccidiosis caused by Eimeria spp. results in substantial economic losses in the poultry industry. The objective of this study was to investigate the effects of dietary supplementation with n-3 polyunsaturated fatty acids-enriched fish oil on growth performance, intestinal barrier integrity, and intestinal immune response of broilers challenged with Eimeria spp. A total of 576 14-day-old broilers were randomly assigned in a completely randomized design with a 3×2 factorial arrangement, comprising two diets supplemented with either 5% fish oil or 5% soybean oil, and three Eimeria spp. infection levels: a non-challenge control, a low dose of Eimeria challenge, and a high challenge dose. The results of the study revealed significant interactions between diet and Eimeria challenge to parameters of gut barrier integrity and feed intake. A significant interaction was observed in feed intake between 5-8 days post-infection (DPI), where the fish oil groups exhibited a higher amount of feed intake compared to the soybean oil diet groups after coccidiosis infection. The effects of the fish oil diet resulted in enhanced gut barrier integrity, as evidenced by a trend of decreased gastrointestinal leakage and a lower mean of small intestine lesion scores after Eimeria challenge. Additionally, significant interactions were noted between Eimeria spp. challenge and diet regarding jejunal crypt depth. The positive impact of the fish oil diet was particularly noticeable with the high Eimeria challenge dose. Overall, these findings underscore the relationship between the fish oil diet and Eimeria challenge on broiler chicken intestinal health. Dietary supplementation of fish oil has the potential to maintain small intestine barrier integrity with severe Eimeria infection conditions.

Analysis of H5N8 influenza virus infection in chicken with mApple reporter genes in vivo and in vitro

H5N8 highly pathogenic avian influenza virus (HPAIV) has caused huge losses to the global poultry industry and critically threatens public health. Chickens are the important host for the transmission. However, the distribution of H5N8 avian influenza virus (AIV) in chicken and the infected cell types are limitedly studied. Therefore, in this study, we detected viral replication and infection by generating recombinant H5N8 AIV expressing an easily tracked mApple fluorescent reporter. The results showed that recombinant viruses passaged four times in chicken embryos successfully expressed mApple proteins detected by fluorescence microscopy and WB, which verified that the constructed recombinant viruses were stable. Compared to parental virus, although recombinant virus attenuated for replication in MDCK cells, it can still replicate effectively, and form visible plaques. Importantly, the experiments on infection of chicken PBMCs in vitro showed a strong correlation between mApple positivity rate and NP positivity rate (r = 0.7594, P =0.0176), demonstrating that mApple reporter could be used as an indicator to accurately reflect AIV infection. Then we infected monocytes/macrophages in PBMCs in vitro and detected the mApple positive percentage was 55.1%-80.4%, which confirmed the chicken primary monocytic/macrophages are important target cells for avian influenza virus infection. In chicken, compared with parental virus, the recombinant virus-infected chickens had lower viral titers in oropharyngeal cloacal and organs, but it can cause significant pathogenicity in chicken and the mortality rate was approximately 66%. In addition, the results of bioluminescent imaging showed that the fluorescence in the lungs was strongest at 5 days post-infection (DPI). Finally, we discovered the mApple positive expression in chicken lung immune cells (CD45+ cells), especially some T cells (CD4 and CD8 T cells) also carrying mApple, which indicates that the H5N8 AIV showed a tropism for immune cells including chicken T cells causing potentially aggressive against cellular immunity. We have provided a simple visualization for further exploration of H5N8 AIV infected chicken immune cells, which contributes to further understanding pathogenic mechanism of H5N8 AIV infection in chicken.

Bioinformatics characteristics and expression analysis of IL-8 and IL-10 in largemouth bass (Micropterus salmoides) upon Nocardia seriolae infection

IL-8 and IL-10 are crucial inflammatory cytokines that participate in defending host cells against infections. To demonstrate the function of the two interleukin genes in largemouth bass (Micropterus salmoides), we initially cloned and identified the cDNA sequences of il-8 and il-10 in largemouth bass, referred to as Msil-8 and Msil-10, respectively. The open reading frame (ORF) of Msil-8 was 324 bp in length, encoding 107 amino acids, while the ORF of Msil-10 consisted of 726 bp and encoded 241 amino acids. Furthermore, the functional domains of the SCY domain in MsIL-8 and the IL-10 family signature motif in MsIL-10 were highly conserved across vertebrates. Additionally, both MsIL-8 and MsIL-10 showed close relationships with M. dolomieu. Constitutive expression of Msil-8 and Msil-10 was observed in various tissues, with the highest level found in the head kidney. Subsequently, largemouth bass were infected with Nocardia seriolae via intraperitoneal injection to gain a further understanding of the function of these two genes. Bacterial loads were initially detected in the foregut, followed by the midgut, hindgut, and liver. The mRNA expression of Msil-8 was significantly down-regulated after infection, especially at 2 days post-infection (DPI), with a similar expression to Msil-10. In contrast, the expression of Msil-8 and Msil-10 was significantly upregulated in the foregut at 14 DPI. Taken together, these results reveal that the function of IL-8 and IL-10 was likely hindered by N. seriolae, which promoted bacterial proliferation and intercellular diffusion.

Clinico-pathological assessment of virulent Newcastle Disease Virus in ducks.

Newcastle disease (ND) is an infectious, highly contagious and lethal disease of avian species. It is considered that ducks are natural reservoir or carrier for Newcastle disease virus (NDV) and are resistant against different strains of NDV. Current study was designed to evaluate the pathogenesis of Newcastle disease in domestic ducks through histopathology, immunohistochemistry (IHC) and serum biochemical changes. For this purpose, eighty ducks were reared for 42 days and divided in two groups A and B. Ducks in group A were challenged with (NDV) at rate of 0.1 ml of ELD50 (virus titer 107.32/100µl) on second week of age, whereas Group B was control negative. Splenomegaly, atrophy of thymus and necrotic lesion in kidney were observed on 9th day of post infection. Hepatic degeneration and mononuclear cell infiltration were noticed in proventriculus and intestine in challenged ducks. Viral antigen detected in lungs, intestine, proventriculus and lymphoid organs of infected ducks through IHC. Albumin and total protein values were significantly low in infected groups A as compared to control group B. ALT, AST, and ALP values were significantly high in infected group A. On 5th and 7th day of post infection oropharyngeal swabs were negative for NDV and cloacal swabs were positive for NDV through Reverse transcriptase polymerase chain reaction. It is concluded that ducks are susceptible to NDV and virulent strain of NDV caused disease in ducks.

Dynamics of ex vivo cytokine transcription during experimental Toxocara canis infection in Balb/c mice.

The cytokine microenvironment is crucial in generating and polarizing the immune response. A means of monitoring this environment would be of great value for better understanding Toxocara canis immune modulation. The aim of this study was to analyze the dynamics of cytokine transcription ex vivo, during early (24-48 hours) and late (15-30 days) times post-infection, in the mesenteric lymph nodes, spleen and intestinal mucosa of Balb/c mice experimentally infected with T. canis larvae. Mice in the treated group were infected with 100 third-stage larvae (L3), whereas mice in the control group were not infected. Analyses were performed at different times: 24-48 hours post-infection (HPI), 15-30 days post-infection (DPI). IL4, IL10, IL12 and Ym1 mRNA transcriptions were analyzed through qPCR. This study showed cytokine transcription mediated by migrating larvae in the mesenteric lymph nodes and spleen at 24-48 HPI, whereas cytokine transcription in the intestinal mucosa was observed only at late times (15-30 DPI). These results suggest that the T. canis larvae migration during infection might play a role in cytokine dynamics. Since the cytokine microenvironment is crucial in modulating immune response, knowledge of cytokine dynamics during T. canis infections pave the way to better understand its interaction with the host.

Testicular damage without clinical manifestations in BALB/c mice experimentally infected with Zika virus.

In 2015-2016, the Zika virus (ZIKV) caused a major epidemic in the Americas, increasing cases of microcephaly and Guillain-Barré syndrome. During this period, the discovery of ZIKV sexual transmission intensified studies on the impact of this virus on the reproductive organs. For this study, 2-month-old male BALB/c mice were infected with 1.26 x 106 PFU/mL of ZIKV in solution via the intravenous route. After three, seven, and fourteen days post-infection (DPI), blood and testicle samples were obtained to detect ZIKV RNA. The authors observed that the infected animals had slower weight gain than the control group. Viremia occurred only at 3DPI, and the ZIKV RNA was detected in one testis sample at 7DPI. The histopathological analysis of this organ revealed intense disorganization of the seminiferous tubules' structure, inflammatory infiltrate, necrosis, hemorrhage, fluid accumulation, congestion of blood vessels, and reduced sperm count. Ultrastructural analysis showed nuclear changes in tubule cells, activation of interstitial cells, and morphological changes in spermatozoa, in addition to fragmentation and decreased electron density of the genetic material of these cells. Thus, despite causing predominantly asymptomatic infections, ZIKV can cause significant subclinical and transient damage, including to male reproductive organs.

Mucosal immune responses of gut IgM in common carp (Cyprinus carpio) following infection with spring viremia of carp virus (SVCV)

Immunoglobulin M (IgM) specifically recognizes various antigens and can activate complement, mediate cytotoxicity, opsonize and agglutinate pathogens to induce phagocytosis, all of which play an important role in immunity. However, the IgM response of common carp (Cyprinus carpio) in the intestinal mucosa after viral infection has not been thoroughly. Therefore, we successfully produced an anti-carp IgM monoclonal antibody and developed a model of viral infection to study the kinetics of immune responses after viral infection. Our results showed that the expression of IL1-β and Igs were dramatically increased, implying that common carp exhibited a significant innate and adaptive immune response to viral infection. Furthermore, we found that the IgM responses varied between the two infection strategies. At 14 days post-infection (DPI), a significant population of IgM+ B cells were observed in the gut, accompanied by a sharp rise in IgM levels. The immune response to secondary infection started at 7 DPI, suggesting that the IgM response is faster in the gut after re-infection. Importantly, we also explored the variability of different gut compartments to viral infection, and result revealed a stronger immune response in the hindgut than in the foregut and midgut. Overall, our findings indicate that IgM plays an important role in the intestinal immune response following primary and secondary viral infection, in which the hindgut plays a major immune function.

COVID-19 and influenza infections mediate distinct pulmonary cellular and transcriptomic changes

SARS-CoV-2 infection can cause persistent respiratory sequelae. However, the underlying mechanisms remain unclear. Here we report that sub-lethally infected K18-human ACE2 mice show patchy pneumonia associated with histiocytic inflammation and collagen deposition at 21 and 45 days post infection (DPI). Transcriptomic analyses revealed that compared to influenza-infected mice, SARS-CoV-2-infected mice had reduced interferon-gamma/alpha responses at 4 DPI and failed to induce keratin 5 (Krt5) at 6 DPI in lung, a marker of nascent pulmonary progenitor cells. Histologically, influenza- but not SARS-CoV-2-infected mice showed extensive Krt5+ “pods” structure co-stained with stem cell markers Trp63/NGFR proliferated in the pulmonary consolidation area at both 7 and 14 DPI, with regression at 21 DPI. These Krt5+ “pods” structures were not observed in the lungs of SARS-CoV-2-infected humans or nonhuman primates. These results suggest that SARS-CoV-2 infection fails to induce nascent Krt5+ cell proliferation in consolidated regions, leading to incomplete repair of the injured lung.

The pathogenicity of blood stream and central nervous system forms of Trypanosoma brucei rhodesiense trypanosomes in laboratory mice: a comparative study.

Background: Human African trypanosomiasis (HAT) develops in two stages namely early stage when trypanosomes are found in the blood and late stage when trypanosomes are found in the central nervous system (CNS). The two environments are different with CNS environment reported as being hostile to the trypanosomes than the blood environment. The clinical symptoms manifested by the disease in the two environments are different. Information on whether blood stream are pathologically different from CNS trypanosomes is lacking. This study undertook to compare the inter-isolate pathological differences caused by bloodstream forms (BSF) and central nervous system (CNS) of five Trypanosoma brucei rhodesiense ( Tbr) isolates in Swiss white mice. Methods: Donor mice infected with each of the five isolates were euthanized at 21 days post infection (DPI) for recovery of BSF trypanosomes in heart blood and CNS trypanosomes in brain supernatants. Groups of Swiss white mice (n = 10) were then infected with BSF or CNS forms of each isolate and monitored for parasitaemia, packed cell volume (PCV), body weight, survivorship, trypanosome length, gross and histopathology characteristics. Results: Amplification of SRA gene prior to trypanosome morphology and pathogenicity studies confirmed all isolates as T. b. rhodesiense. At 21 DPI, CNS trypanosomes were predominantly long slender (LS) while BSF were a mixture of short stumpy and intermediate forms. The density of BSF trypanosomes was on average 2-3 log-scales greater than that of CNS trypanosomes with isolate KETRI 2656 having the highest CNS trypanosome density. Conclusions: The pathogenicity study revealed clear differences in the virulence/pathogenicity of the five (5) isolates but no distinct and consistent differences between CNS and BSF forms of the same isolate. We also identified KETRI 2656 as a suitable isolate for acute menigo- encephalitic studies.