Mosquito-Associated Virus Isolation from Field-Collected Mosquitoes

Summary

Numerous novel virus-like sequences have been found in mosquitoes due to the extensive use of sequencing technologies. We provide an effective procedure for isolating and amplifying viruses using vertebrate and mosquito cell lines, which might serve as the basis for future studies on mosquito-associated viruses, including mosquito-borne and mosquito-specific viruses.

Abstract

With the broad application of sequencing technologies, many novel virus-like sequences have been discovered in arthropods, including mosquitoes. The two main categories of these new mosquito-associated viruses are "mosquito-borne viruses (MBVs)" and "mosquito-specific viruses (MSVs)". These novel viruses might be pathogenic to both vertebrates and mosquitoes, or they could just be symbiotic with mosquitoes. Entity viruses are essential to confirm the biological characters of these viruses. Thus, a detailed protocol has been described here for virus isolation and amplification from field-collected mosquitoes. First, the mosquito samples were prepared as supernatants of mosquito homogenates. After centrifugation twice, the supernatants were then inoculated into either mosquito cell line C6/36 or vertebrate cell line BHK-21 for virus amplification. After 7 days, the supernatants were collected as the P1 supernatants and stored at -80 °C. Next, P1 supernatants were passaged twice more in C6/36 or BHK-21 cells while the cell status was being checked daily. When cytopathogenic effect (CPE) on the cells was discovered, these supernatants were collected and used to identify viruses. This protocol serves as the foundation for future research on mosquito-associated viruses, including MBVs and MSVs.

Introduction

Mosquitoes are a group of important pathogenic arthropod vectors. There are approximately 3,500 species of mosquitoes in the family Culicidae^1,2. The development of high-throughput sequencing technologies has led to the discovery of many novel, virus-like sequences in mosquitoes from different parts of the world³. Generally, these mosquito-associated viruses can be classified into two main groups: MBVs and MSVs.

MBVs are a group of diverse viruses that are causative agents of many human or animal illnesses, such as yellow fever virus (YFV), dengue virus (DENV....

Protocol

1. Mosquito sampling and sorting

1. Trap the adult mosquitoes through the light traps MXA-02 or carbon dioxide mosquito traps in the field.
2. Kill the collected mosquitoes by dipping in liquid nitrogen^10,11. Transport them to the laboratory by the cold-chain logistics system¹².
   NOTE: Dry ice was primarily used in the cold-chain logistics system.
3. (Optional) If the sample sites were near the lab, directly send the alive mosquitoes in the net traps to the laboratory and euthanize them by freezing at ≤-20 °C for 30 min

Discussion

The objective of this method was to offer a practical way for isolating mosquito-associated viruses using various cell lines. It is critical to add the Antibiotic-Antimycotic (Penicillin-Streptomycin-Amphotericin) to the supernatants of the mosquito homogenates to avoid contamination by bacteria or fungi. Mosquitoes and viral supernatants obtained in the field must be refrigerated at -80 °C to avoid repeated freeze-thaw cycles.

Another critical step in the protocol was grinding. Mosquito .......

Materials

Name	Company	Catalog Number	Comments
0.22 µm membrane filter	Millipore	SLGP033RB	Polymer films with specific pore ratings.To remove cell debris and bacteria.
24-well plates	CORNING	3524	Containers for cell
75 cm2 flasks	CORNING	430641	Containers for cell
a sterile 2 mL tube with 3 mm ceramic beads
Antibiotic-Antimycotic	Gibco	15240-062	Antibiotic in the medium to prevent contamination from bacteria and fungi
Automated nucleic acid extraction system	NanoMagBio	S-48
BHK-21 cells	National Virus Resource Center, Wuhan Institute of Virology
C6/36 cells	National Virus Resource Center, Wuhan Institute of Virology
Centrifugal machine	Himac	CF16RN	Instrument for centrifugation of mosquito samples
CO2
Dulbecco’s minimal essential medium (DMEM)	Gibco	C11995500BT	medium for vertebrate cell lines
Ebinur Lake virus			Cu20-XJ isolation
Feta Bovine Serum (FBS)	Gibco	10099141C	Provide nutrition for cells
high-speed low-temperature tissue homogenizer	servicebio	KZ-III-F	Instrument for grinding
incubator (28 °C)	Panasonic	MCO-18AC	Instrument for cell culture
incubator (37 °C)	Panasonic	MCO-18AC	Instrument for cell culture
PCR tube
penicillin-streptomycin	Gibco	15410-122	Antibiotic in the medium to prevent contamination from bacteria
Penicillin-Streptomycin-Amphotericin B Solution	Gibco	15240096
Refrigerator (-80 °C)	sanyo	MDF-U54V
Roswell Park Memorial Institute  medium (RPMI)	Gibco	C11875500BT	medium for mosiquto cell lines
Screw cap storage tubes (2 mL)	biofil	FCT010005
sterile pestles	Tiangen	OSE-Y004	Consumables  for grinding
TGrinder OSE-Y30 electric tissue grinder	Tiangen	OSE-Y30	Instrument for grinding
The dissecting microscope	ZEISS	stemi508
the light traps MXA-02	Maxttrac
The mosquito absorbing machine	Ningbo Bangning
The pipette tips	Axygen	TF
The QIAamp viral RNA mini kit	QIAGEN	52906
Tweezers	Dumont	0203-5-PO