scholarly journals Infectivity Assay for Detection of SARS‐CoV‐2 in Samples from Patients with COVID‐19

2021 ◽  
Author(s):  
Satoshi Hiroi ◽  
Ritsuko Kubota‐Koketsu ◽  
Tadahiro Sasaki ◽  
Saeko Morikawa ◽  
Kazushi Motomura ◽  
...  
Keyword(s):  
Infectivity Assay

A Nude Mouse Model as an in vivo Infectivity Assay for Cryptospomdiosis

1993 ◽  
Vol 27 (3-4) ◽  
pp. 65-68 ◽  
Author(s):  
B. H. Kwa ◽  
M. Moyad ◽  
M. A. Pentella ◽  
J. B. Rose
Keyword(s):  
Drinking Water ◽  
Mouse Model ◽  
Nude Mouse ◽  
Cryptosporidium Parvum ◽  
Nude Mice ◽  
Surface Waters ◽  
Nude Mouse Model ◽  
Infectivity Assay ◽  
Limiting Dilution

Cryptosporidium parvum is an important patliogen of diarrlieal disease which has been implicated in several outbreaks associated with contamination of surface waters. In monitoring for C. parvum in drinking water sources, it is important to asce tain the viability, and more importantly, the infectivity of low numbers of recovered oocysts. Groups of 10 Balb/C nude (nu/nu) mice, 4-8 weeks old at time of inoculation, were infected with C. parvum oocysts from naturally infected calves and purified using Sheather's sucrose gradients. Oocysts were counted using the Merifluor IFA kit (Meridian). Each group of 10 mice were infected with 1,10,100 and 1000 oocysts respectively. Numbers of oocysts per inoculation were determined by limiting dilution, and parallel inocula were counted microscopically to ascertain the accuracy of the dilutions. Two uninfected nude mice were kept in each cage to serve as controls. Mouse stools were collected every 4 days, concentrated using the Fekal Kontrate Concentration Kit (Meridian) and oocysts were counted with a UV microscope using the Merifluor IFA Kit (Meridian). Oocyst counts were expressed in terms of number of oocyst/g feces. Mice inoculated with 1000 oocysts began to shed oocysts on day 32, mice inoculated with 100 oocysts began to shed on days 44-48, mice inoculated with 10 oocysts began to shed on days 56-60, and mice inoculated with 1 oocyst shed on days 68-88. All infected mice continued to shed oocysts intermittently and with variable oocyst counts until day 180 when the experiment was terminated. This study established that it is possible to infect nude mice with very low numbers, down to a single oocyst. We are currently in the process of correlating the nude mouse assay with other viability assays.

An improved infectivity assay for DNA repair

1982 ◽  
Vol 10 (5) ◽  
pp. 347-347
Author(s):  
ANTON J. ALLDRICK ◽  
JOHN B. HAYS
Keyword(s):  
Dna Repair ◽  
Infectivity Assay

scholarly journals The VP5 Domain of VP4 Can Mediate Attachment of Rotaviruses to Cells

2000 ◽  
Vol 74 (2) ◽  
pp. 593-599 ◽  
Author(s):  
Selene Zárate ◽  
Rafaela Espinosa ◽  
Pedro Romero ◽  
Ernesto Méndez ◽  
Carlos F. Arias ◽  
...  
Keyword(s):  
Cell Surface ◽  
Binding Assay ◽  
Cell Attachment ◽  
Wild Type ◽  
Binding Assays ◽  
Virus Binding ◽  
Binding Characteristics ◽  
Surface Receptors ◽  
Infectivity Assay ◽  
Fusion Products

ABSTRACT Some animal rotaviruses require the presence of sialic acid (SA) on the cell surface to infect the cell. We have isolated variants of rhesus rotavirus (RRV) whose infectivity no longer depends on SA. Both the SA-dependent and -independent interactions of these viruses with the cell are mediated by the virus spike protein VP4, which is cleaved by trypsin into two domains, VP5 and VP8. In this work we have compared the binding characteristics of wild-type RRV and its variant nar3 to MA104 cells. In a direct nonradioactive binding assay, both viruses bound to the cells in a saturable and specific manner. When neutralizing monoclonal antibodies directed to both the VP8 and VP5 domains of VP4 were used to block virus binding, antibodies to VP8 blocked the cell attachment of wild-type RRV but not that of the variant nar3. Conversely, an antibody to VP5 inhibited the binding of nar3 but not that of RRV. These results suggest that while RRV binds to the cell through VP8, the variant does so through the VP5 domain of VP4. This observation was further sustained by the fact that recombinant VP8 and VP5 proteins, produced in bacteria as fusion products with glutathione S-transferase, were found to bind to MA104 cells in a specific and saturable manner and, when preincubated with the cell, were capable of inhibiting the binding of wild-type and variant viruses, respectively. In addition, the VP5 and VP8 recombinant proteins inhibited the infectivity of nar3 and RRV, respectively, confirming the results obtained in the binding assays. Interestingly, when the infectivity assay was performed on neuraminidase-treated cells, the VP5 fusion protein was also found to inhibit the infectivity of RRV, suggesting that RRV could bind to the cell through two sequential steps mediated by the interaction of VP8 and VP5 with SA-containing and SA-independent cell surface receptors, respectively.

Microwave Inactivation of Cyclospora cayetanensis Sporulation and Viability of Cryptosporidium parvum Oocysts

2006 ◽  
Vol 69 (8) ◽  
pp. 1957-1960 ◽  
Author(s):  
YNES R. ORTEGA ◽  
JYEYIN LIAO
Keyword(s):  
Cryptosporidium Parvum ◽  
Propidium Iodide ◽  
Cryptosporidium Oocyst ◽  
Cooking Time ◽  
Cyclospora Cayetanensis ◽  
The Third ◽  
Infectivity Assay ◽  
Cryptosporidium Oocysts ◽  
Cryptosporidium Parvum Oocysts ◽  
Cooking Times

The efficacy of microwave heating on the viability of Cryptosporidium parvum oocysts and on the sporulation of Cyclospora cayetanensis oocysts for various periods of cooking times (0, 10, 15, 20, 30, and 45 s) at 100% power was determined. Cyclospora oocysts were stored in 2.5% dichromate at 23°C for 2 weeks, and sporulation rates were then determined. The 4′,6-diamidino-2-phenylindole and propidium iodide vital stain and the neonate animal infectivity assay determined Cryptosporidium oocyst viability. Cryptosporidium oocysts could be completely inactivated with as little as 20 s of cooking time, whereas Cyclospora sporulation was observed up to 45 s. Two of the examined microwave ovens were more effective at reducing sporulation and viability than the third one. Because of the variability of temperature achieved by the various ovens, cooking time was not an accurate parameter for parasite inactivation. Cryptosporidium oocysts could be inactivated only when temperatures of 80°C or higher were reached in the microwave ovens.

Infectivity Assay on Local-Lesion Hosts

1998 ◽  
pp. 67-77
Author(s):  
Jeanne Dijkstra ◽  
Cees P. de Jager
Keyword(s):  
Local Lesion ◽  
Infectivity Assay

Tissue culture infectivity assay for porcine parvovirus

1984 ◽  
Vol 115 (5) ◽  
pp. 108-108
Author(s):  
K. Edwards ◽  
D. Thornton
Keyword(s):  
Tissue Culture ◽  
Porcine Parvovirus ◽  
Infectivity Assay

scholarly journals Pepino mosaic virus on Tomato Seed: Virus Location and Mechanical Transmission

Plant Disease ◽  
2008 ◽  
Vol 92 (12) ◽  
pp. 1701-1705 ◽  
Author(s):  
Kai-Shu Ling
Keyword(s):  
Mosaic Virus ◽  
Large Scale ◽  
Seed Transmission ◽  
Enzyme Linked Immunosorbent Assay ◽  
Mechanical Transmission ◽  
Tomato Seed ◽  
Tomato Production ◽  
Pepino Mosaic Virus ◽  
Infectivity Assay ◽  
Seed Coats

In just a few years, Pepino mosaic virus (PepMV) has become a major threat to greenhouse tomato production around the world. Although tomato seed is suspected to spread the disease, its importance as an initial virus inoculum for PepMV has not been established. To determine the potential for seed transmission, a tomato seed lot highly contaminated with PepMV was used for large-scale seedling grow-out tests. None of 10,000 grow-out seedlings was infected as determined by symptom expression, enzyme-linked immunosorbent assay (ELISA), or infectivity assay on Nicotiana benthamiana. Even though PepMV was not seed transmitted on tomato, the virus was effectively transmitted to tomato and N. benthamiana seedlings through mechanical transmission with seed extract. To examine the exact location where PepMV particles accumulated on the tomato seed, seed coats and embryos were carefully isolated and tested separately by ELISA, real-time RT-PCR, and bioassay on N. benthamiana. PepMV was detected in the seed coat fraction in both immature and mature tomato seeds, but not in the embryo. However, in N. benthamiana, the virus was neither seedborne nor seed-transmitted. Because PepMV is seedborne in tomato, efficient mechanical transmission of PepMV from the virus-contaminated tomato seed to seedlings could initiate a disease epidemic in a new tomato growing area. Thus, it is important to plant certified tomato seed that has been tested free of PepMV.

Rapid, targeted and culture-free viral infectivity assay in drop-based microfluidics

Lab on a Chip ◽  
2015 ◽  
Vol 15 (19) ◽  
pp. 3934-3940 ◽  
Author(s):  
Ye Tao ◽  
Assaf Rotem ◽  
Huidan Zhang ◽  
Connie B. Chang ◽  
Anindita Basu ◽  
...  
Keyword(s):  
High Throughput ◽  
Dynamic Range ◽  
High Sensitivity ◽  
Cost Effective ◽  
Serial Dilution ◽  
Viral Infectivity ◽  
Large Dynamic Range ◽  
Infectivity Assay ◽  
Dilution Experiments

We developed a rapid, targeted and culture-free infectivity assay using high-throughput drop-based microfluidics. The high sensitivity and large dynamic range of our cost effective assay alleviates the need for serial dilution experiments.

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