Characterization of the infectivity of an Indonesian Zika virus strain in mammalian cell lines

Objective:To characterize the infection patterns and growth characteristics of the Zika virus(ZIKV)strain JMB-185 from Indonesia in various mammalian cell lines.Methods:ZIKV was grown in human(A549,HEK293,HepG2,Huh7,Jurkat,and THP-1)and non-human mammalian(RAW264.7,Vero,and Vero76)cell lines.Viral replication kinetics were measured using plaque assay,while intra-and extracellular viral RNA concentrations were assessed using RT-PCR.Flow cytometry was used to quantify the infected cells and cell viability was measured using an MTT assay.The ability of ZIKV to infect cell lines was visualized using a fluorescence immunostaining assay.Results:This ZIKV strain preferentially infected the lung,kidney,and liver cell lines A549,HEK293,Huh7,Vero,and Vero76,but not the immune cells Jurkat,RAW264.7,and THP-1.By contrast,the ZIKV showed no sign of infection in HepG2 cells,while maintaining viral titer over 3 days post-infection,with no infection recorded in immunostaining,no increase in viral RNA,and no indication of cell deterioration.Conclusions:The Indonesian ZIKV strain has a similar infection profile as other strains,except for its poor infectivity on HepG2 cells.Information on the growth characteristics of Indonesia ZIKV will help expand our understanding of the biology of ZIKV which will be useful for various applications including antiviral discovery.

Probability Distribution of SARS-Cov-2 (COVID) Infectivity Following Onset of Symptoms: Analysis from First Principles

The phasing out of protective measures by governments and public health agencies, despite continued seriousness of the coronavirus pandemic, leaves individuals who are concerned for their health with two basic options over which they have control: 1) minimize risk of infection by being vaccinated and by wearing a face mask when appropriate, and 2) minimize risk of transmission upon infection by self-isolating. For the latter to be effective, it is essential to have an accurate sense of the probability of infectivity as a function of time following the onset of symptoms. Epidemiological considerations suggest that the period of infectivity follows a lognormal distribution. This proposition is tested empirically by construction of the lognormal probability density function and cumulative distribution function based on quantiles of infectivity reported by several independent investigations. A comprehensive examination of a prototypical ideal clinical study, based on general statistical principles (the Principle of Maximum Entropy and the Central Limit Theorem) reveals that the probability of infectivity is a lognormal random variable. Subsequent evolution of new variants may change the parameters of the distribution, which can be updated by the methods in this paper, but the form of the probability function is expected to remain lognormal as this is the most probable distribution consistent with mathematical requirements and available information.

Omicron variant (B.1.1.529) of SARS-CoV-2: Mutation, infectivity, transmission, and vaccine resistance

The appearance of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)variant Omicron(B.1.1.529)has caused panic responses around the world because of its high transmission rate and number of mutations.This review summarizes the highly mutated regions,the essential infectivity,transmission,vaccine breakthrough and antibody resistance of the Omicron variant of SARSCoV-2.The Omicron is highly transmissible and is spreading faster than any previous variant,but may cause less severe symptoms than previous variants.The Omicron is able to escape the immune system’s defenses and coronavirus disease 2019 vaccines are less effective against the Omicron variant.Early careful preventive steps including vaccination will always be key for the suppression of the Omicron variant.

Stability and infectivity of coronaviruses in inanimate environments

Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)is a highly contagious virus that can transmit through respiratory droplets,aerosols,or contacts.Frequent touching of contaminated surfaces in public areas is therefore a potential route of SARS-CoV-2 transmission.The inanimate surfaces have often been described as a source of nosocomial infections.However,summaries on the transmissibility of coronaviruses from contaminated surfaces to induce the coronavirus disease 2019 are rare at present.This review aims to summarize data on the persistence of different coronaviruses on inanimate surfaces.The literature was systematically searched on Medline without language restrictions.All reports with experimental evidence on the duration persistence of coronaviruses on any type of surface were included.Most viruses from the respiratory tract,such as coronaviruses,influenza,SARS-CoV,or rhinovirus,can persist on surfaces for a few days.Persistence time on inanimate surfaces varied from minutes to up to one month,depending on the environmental conditions.SARSCoV-2 can be sustained in air in closed unventilated buses for at least 30 min without losing infectivity.The most common coronaviruses may well survive or persist on surfaces for up to one month.Viruses in respiratory or fecal specimens can maintain infectivity for quite a long time at room temperature.Absorbent materials like cotton are safer than unabsorbent materials for protection from virus infection.The risk of transmission via touching contaminated paper is low.Preventive strategies such as washing hands and wearing masks are critical to the control of coronavirus disease 2019.

Comparative Study on the Infectivity and Spore Surface Protein of Nosema bombycis and Its Morphological Variant Strain

A new morphological variant strain of microsporidium was produced by infecting the mulberry looper, Hemerophilaatrilineata [Phthonandria atrilineata], with Nosema bombycis successively for 24 times, and named 24Nbh. Comparativestudies on morphology, infectivity and spore surface protein were conducted. 24Nbh was short and wide, and had asignificant difference (P<0.01) over the Nb spores. The infectivity tests conducted on second instar silkworm larvaeshowed that IC50 of 24Nbh was 1.98104 spores mL-1 and of Nb was 1.72103 spores mL-1, thus indicating that the infectivityof Nb decreased 11.5 times after multiplying in mulberry looper for 24 times. The IC50 of spores from silkworm infected with24 Nbh was 6.9 times less than Nb, showing that the infectivity of 24Nbh spores rejuvenated very fast when reinfected tosilkworms, further more, the length and width of such spore was larger than 24Nbh (P<0.01) and smaller than Nb (P<0.05).The SDS-PAGE profiles of Nb and 24Nbh were generally the same, 4 distinct proteins of 12, 17, 30, 33 kDa were obtainedwith difference in quantity. When 120 g of protein was applied for 2D-PAGE, five suspected different proteins withdifference in quantity were observed. These results demonstrate that these differential proteins maybe associated withvariation in infectivity of the spores.

Infectivity Analysis of Cloned Genomic DNA of P1 Agent in vitro

The ultrastructure of porcine kidney(PK)-15 cells was examined after lipofectamine-aided transfection of the molecular clone of the P1 agent.PK-15 cells transfected with the tandem dimer of the P1molecular DNA clone had numbers of intracytoplasmic inclusions,and a few cells had intranuclear inclusions.Intracytoplasmic inclusions were round to oval and 0.1-0.3μm in diameter,and intranuclear inclusions,which were more electron dense,were of two general types:the first were round and small(0.1μm approximately)and the second were hexagonal and larger(0.4-0.8μm in diameter).Cells transfected with the tandem dimer of the P1 molecular DNA clone tested positive for P1 DNA at passage 5.This is the first report that the P1 molecular clone has infectivity in vitro and it will provide fundamental materials for further study of the biological characterization of P1.

Infectivity of Severe Acute Respiratory Syndrome during Its Incubation Period

Objective To evaluate the infectivity of severe acute respiratory syndrome （SARS） during its incubation period by investigating chains of transmission and individuals isolated for medical observation with a view to providing scientific evidence for updating protocols of medical isolation. Methods Individuals related with the two SARS chains of transmission in Beijing in 2003 and a group of individuals isolated for medical observation in Haidian district of Beijing during the SARS outbreak were selected as subjects of study. Contactors with SARS patients and those with symptom development following the contacts were investigated via questionnaire. Serum samples were collected from super transmitters and tested for SARS-CoV antibody by neutralization test and enzyme linked immunosorbent assay （ELISA）. Results A total of 1 112 contactors were investigated in three surveys. Of them, 669 had a history of close contact with symptomatic SARS patients, 101 developed symptoms with a rate of 15.1%, 363 had a history of close contact with patients in their incubation period, none of whom developed symptoms （0%）. Serum samples were collected fi＇om 32 highly-exposed individuals, of whom 13 developing SARS symptoms atter contact had serum samples positive for SARS-CoV antibody. Samples collected from the asymptomatic contactors were all negative for SARS-CoV antibody. Conclusion SARS cases are infectious only during their symptomatic period and are non-infectious during the incubation period. Isolation for medical observation should be placed for individuals who are in close contact with symptomatic SARS patients. The results of our study are of decisive significance for the Ministry of Health to the definition of SARS close contactor.

TWO DIFFERENTIAL INFECTIVITY EPIDEMIC MODELS WITH NONLINEAR INCIDENCE RATE

This paper considers two differential infectivity（DI） epidemic models with a nonlinear incidence rate and constant or varying population size. The models exhibits two equilibria, namely., a disease-free equilibrium O and a unique endemic equilibrium. If the basic reproductive number σ is below unity,O is globally stable and the disease always dies out. If σ〉1, O is unstable and the sufficient conditions for global stability of endemic equilibrium are derived. Moreover,when σ〈 1 ,the local or global asymptotical stability of endemic equilibrium for DI model with constant population size in n-dimensional or two-dimensional space is obtained.

<i>Brucella melitensis</i>Differs from <i>B. suis</i>in Growth and Urease Activity <i>In-Vitro</i>, and Infectivity in Fisher-344 Rats <i>In-Vivo</i>

Importance of urease activity on pathogenic differences among Brucella species was evaluated. In cell-free extracts, the B. suis urease showed 12 times greater specific activity than the B. melitensis urease. When Fisher-344 rats were inoculated intraperitoneally (IP), at 1 week post-inoculation (PI), B. melitensis wild type 16 M was recovered from spleens and livers in greater numbers than B. suis wild type 1330. At 8 weeks PI, spleens were clear of B. melitensis, whereas B. suis remained. The wild type and the urease deficient strains of B. suis did not differ from each other in terms of recovery from spleen or liver. Our observations suggest that B. melitensis induces greater acute infectivity in Fisher-344 rats, whereas B. suis causes chronic infectivity;and urease activity has no influence on Brucella infection using an IP route.

Formulation of an Early Warning Infectivity Score System for Adult Patients with Acute Bacterial Diarrhea

The aim of our study was to develop a scoring system to predict whether diarrhea is of a bacterial origin and whether the diarrheal patients constitute a potential source of infection to others. Adults with acute diarrhea （n=424） were enrolled in the study. Logistic regression and standard regression coefficients were used to formulate the Early Warning Infectivity Score System for Adults with Acute Bacterial Diarrhea （EWIS-ABD）. Four risk factors were identified by logistic regression, including body temperature （P〈0.01）, abdominal pain （P〈0.01）, leukocyte count in stool （P〈0.01）, and unclean dietary history （P〈0.01）. EWIS-ABD was thus developed, in which the value 〉5 points was set as an indicator of bacterial diarrhea. The incidence of bacterial diarrhea increased along with the elevated score. EWIS-ABD was more specific for bacterial diarrhea than for viral diarrhea. The accuracy and reliability of EWIS-ABD was high by prospective validation in 478 patients with acute diarrhea.

Single amino acid mutation of SR-BI decreases infectivity of hepatitis C virus derived from cell culture in a cell culture model

AIM To investigate the effect of a single amino acid mutation in human class B scavenger receptor I(SR-BI) on the infectivity of cell culture-derived hepatitis C virus(HCVcc) in SR-BI knock-down Huh7-si SR-BI cells.METHODS Site-directed mutagenesis was used to construct the SR-BI S112 F mutation,and the mutation was confirmed by nucleotide sequencing. SR-BI knock-down Huh7-si SR-BI cells were transfected with SR-BI S112 F,SR-BI wild type(WT) and control plasmids,and then infected with HCVpp(HCV pseudoparticles) and hepatitis C virus derived from cell culture(HCVcc). A fluorescence assay was performed to analyze the effect of the S112 F mutation on HCV entry; quantitative real-time PCR,immunofluorescence,and Western blot assays were used to analyze the effect of the S112 F mutation on HCV infectivity. CHO cells expressing WT and SRBI S112 F were incubated with the HCV E2 protein expressed in HEK 293 T cells,and flow cytometry was performed to examine the ability of SR-BI S112 F to bind to the HCV E2 protein. Huh7-si SR-BI cells were transfected with SR-BI WT and the S112 F mutant,andthen Di I-HDL was added and images captured under the microscope to assess the ability of SR-BI S112 F to take up HDL.RESULTS The SR-BI S112 F mutation was successfully constructed. The S112 F mutation decreased the expression of the SR-BI m RNA and protein. SR-BI S112 F decreased HCV entry and HCVcc infectivity in Huh7-si SR-BI cells. The S112 F mutation impaired the binding of SR-BI to HCV E2 protein and decreased the HDL uptake of SR-BI.CONCLUSION The S112 F single amino acid mutation in SR-BI decreased the levels of the SR-BI m RNA and protein,as well as the ability of SR-BI to bind to the HCV E2 protein. Amino acid 112 in SR-BI plays important roles in HCV entry and the infectivity of HCVcc in vitro.

Infectivity of SARS-CoV-2 and protection against reinfection in rats

DEAR EDITOR,The severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) pandemic remains an important global public health issue. In this study, we unexpectedly found that wildtype Sprague-Dawley(SD) rats can be infected with the SARS-CoV-2 prototype. Our results showed direct experimental evidence of the infectivity of SARS-CoV-2 infection, subsequent pathogenicity, and protection against reinfection in rats.

Experimental infectivity of Theileria luwenshuni and Theileria uilenbergi in Chinese Kunming mice

Theileria luwenshuni and Theileria uilenbergi are important tick-borne pathogens and cause substantial losses to the sheep industry in China. The improvement in detection techniques has allowed the identification of multi-homing parasitism in Theileria parasites. Herein we evaluated the experimental infectivity of T. luwenshuni and T. uilenbergi in Chinese Kunming mice by screening blood samples of experimentally inoculated mice by microscopic examination（ME） and PCR. T. luwenshuni infected Chinese Kunming mice and 20 mice inoculated with this parasite were positive by ME and PCR. In addition, T. uilenbergi infected mice and 20 mice inoculated with this species were positive by ME and PCR. However, the number of red blood cells and the levels of hemoglobin of 40 infected mice had no obvious changes in the course of infection. Our results demonstrated the multi-homing parasitism of T. luwenshuni and T. uilenbergi, which were believed to be parasites of sheep and goats. This study was the first to demonstrate the infection of T. luwenshuni and T. uilenbergi in Kunming mice.

Variation of resistance and infectivity between Pseudomonas fluorescens SBW25 and bacteriophage Ф2 and its therapeutic implications

Dear Editor,Studies of the coevolutionary dynamics between Pseudomonas fluorescens SBW25 and bacteriophageФ2 can explore host resistance and parasite infectivity with applications in the ecological and therapeutic fields.Coevolutionary dynamics determine the efficacy of phage-based therapy.In the study described here,bacterial resistance and phage infectivity fluctuated with culture

ApoB-containing lipoproteins promote infectivity of chlamydial species in human hepatoma cell line

AIM:To evaluate the direct binding of two main chlamydial biovars(C.trachomatis and C.pneumoniae) to plasma lipoproteins and its effect on chlamydial infection rate in human hepatoma cell line(HepG2 cells). METHODS:Murine plasma lipoproteins were fractionated and isolated using fast-performance liquid chromatography(FPLC),spotted on nitrocellulose membrane and incubated with chlamydial suspensions. Direct binding of chlamydial particles to lipoprotein fractions has been studied using lipopolysaccharide-specific antibodies in immuno-dot blot binding assay and immunoprecipitation analysis.Immunostaining protocol as well as flow cytometry analysis have been employed to study the infectivity rate of chlamydial species in HepG2 cells. RESULTS:Elementary bodies of both C.trachomatis and C.pneumoniae bind ApoB-containing fractions of plasma lipoproteins.That binding becomes stronger when heat-denatured FPLC fractions are used, suggesting a primary role of apolipoproteins in interaction between chlamydial particle and lipoprotein. Both chlamydial biovars efficiently propagate in human hepatoma cell line-HepG2 cells even in serum free conditions forming late-stage inclusion bodies and releasing extracellular elementary bodies.Preincubation of C.trachomatis and C.pneumoniae with native ApoB-containing lipoproteins enhances the rate of chlamydial infection in HepG2 cells.CONCLUSION:A productive infection caused by C. trachomatis and C.pneumoniae may take place in human-derived hepatocytes revealing hepatic cells as possible target in chlamydial infection.Obtained results may suggest the participation of lipoprotein receptors in the mechanism of attachment and/or entry of chlamydial particles into target cells.

Laboratory studies on the infectivity of human respiratory viruses:Experimental conditions,detections,and resistance to the atmospheric environment

The environmental stability of infectious viruses in the laboratory setting is crucial to the transmission potential of human respiratory viruses.Different experimental techniques or conditions used in studies over the past decades have led to diverse understandings and predictions for the stability of viral infectivity in the atmospheric environment.In this paper,we review the current knowledge on the effect of simulated atmospheric conditions on the infectivity of respiratory viruses,mainly focusing on influenza viruses and coronaviruses,including severe acute respiratory syndrome coronavirus 2 and Middle East respiratory syndrome coronavirus.First,we summarize the impact of the experimental conditions on viral stability;these involve the methods of viral aerosol generation,storage during aging and collection,the virus types and strains,the suspension matrixes,the initial inoculum volumes and concentrations,and the drying process.Second,we summarize and discuss the detection methods of viral infectivity and their disadvantages.Finally,we integrate the results from the reviewed studies to obtain an overall understanding of the effects of atmospheric environmental conditions on the decay of infectious viruses,especially aerosolized viruses.Overall,this review highlights the knowledge gaps in predicting the ability of viruses to maintain infectivity during airborne transmission.

gp120-derived amyloidogenic peptides form amyloid fibrils that increase HIV-1 infectivity

Apart from mediating viral entry,the function of the free HIV-1 envelope protein(gp120)has yet to be elucidated.Our group previously showed that EP2 derived from oneβ-strand in gp120 can form amyloid fibrils that increase HIV-1 infectivity.Importantly,gp120 contains~30β-strands.We examined whether gp120 might serve as a precursor protein for the proteolytic release of amyloidogenic fragments that form amyloid fibrils,thereby promoting viral infection.Peptide array scanning,enzyme degradation assays,and viral infection experiments in vitro confirmed that manyβ-stranded peptides derived from gp120 can indeed form amyloid fibrils that increase HIV-1 infectivity.These gp120-derived amyloidogenic peptides,or GAPs,which were confirmed to form amyloid fibrils,were termed gp120-derived enhancers of viral infection(GEVIs).GEVIs specifically capture HIV-1 virions and promote their attachment to target cells,thereby increasing HIV-1 infectivity.Different GAPs can cross-interact to form heterogeneous fibrils that retain the ability to increase HIV-1 infectivity.GEVIs even suppressed the antiviral activity of a panel of antiretroviral agents.Notably,endogenous GAPs and GEVIs were found in the lymphatic fluid,lymph nodes,and cerebrospinal fluid(CSF)of AIDS patients in vivo.Overall,gp120-derived amyloid fibrils might play a crucial role in the process of HIV-1 infectivity and thus represent novel targets for anti-HIV therapeutics.

HearNPV Pseudotyped with PIF1,2,and 3 from MabrNPV：Infectivity and Complex Stability

Effective oral infection is set off by interaction of a group of conserved per os infectivity factors(PIFs) with larval midgut columnar epithelial cells. We constructed pseudotyped viruses by substituting pif1, pif2 or pif3 genes of Helicoverpa armigera nucleopolyhedrovirus(Hear NPV) with their homologs from Mamestra bracissae multiple nucleopolyhedrovirus and tested their infectivity to tissue culture cells and to larvae. Transfection and infection assays revealed that all recombinant viruses generated infectious budded virus in both cell culture and in larvae. Electron microscopy showed synthesized occlusion body and occlusion derived virus(ODV) were morphologically indistinguishable from those of the parental virus. By contrast, feeding assays revealed that pseudotyped viruses could not rescue oral infectivity except for pif3 pseudotyped virus that only partially rescued oral infectivity but at a mortality rate much lower than that of the parental Hear NPV. Consistent with the bioassay result, PIF complex was detected in ODVs of pif3 pseudotyped virus only but not in pif1 or pif2 pseudotyped viruses. Our results suggest that PIF complex is essential for oral infectivity, and in the formation of the PIF complex, PIF1, 2 are virus-specific while PIF3 does not appear to be as specific and can function in heterologous environment, albeit to a much more limited extent.

试管婴儿妊娠合并结外NK/T细胞淋巴瘤鼻型1例

1临床资料患者,女,31岁,因咽部不适1个月余,咽痛6 d,发热2 d入院。患者1个月前出现咽部不适,6 d前转为咽部锐痛,吞咽时加重,伴有鼻塞、睡眠打鼾、张口呼吸,于当地医院住院治疗,诊断为咽旁间隙感染,予头孢类抗生素治疗效果欠佳。后发热2 d,体温最高38.5℃,咽痛较前加重,暂以“咽旁间隙感染”收入青岛大学附属医院耳鼻咽喉头颈外科治疗。患者既往体健,行试管婴儿后孕20周。

Multilocular thymic cysts can be easily misdiagnosed as malignant tumor on computer tomography:A case report

BACKGROUND Multilocular thymic cyst(MTC)is a rare mediastinal lesion which is considered to occur in the process of acquired inflammation.It is usually characterized by well-defined cystic density and is filled with transparent liquid.CASE SUMMARY We report on a 39-year-old male with a cystic-solid mass in the anterior mediastinum.Computer tomography(CT)imaging showed that the mass was irregular with unclear boundaries.After injection of contrast agent,there was a slight enhancement of stripes and nodules.According to CT findings,it was diagnosed as thymic cancer.CONCLUSION After surgery,MTC accompanied by bleeding and infection was confirmed by pathological examination.The main lesson of this case was that malignant thymic tumor and MTC of the anterior mediastinum sometimes exhibit similar CT findings.Caution is necessary in clinical work to avoid misdiagnosis.