VIROSOMES

Presented by-

Sushmita Gupta

M.Pharmacy

Industrial Pharmacy

Acharya & B.M. Reddy College of Pharmacy

Introduction

Structure of virosomes

Mechanism of action

Advantages

Methods of preparation

Characterization of virosomes

Applications

References

CONTENTS

Virosomes can be defined as a drug or a vaccine delivery mechanism consisting of unilamellar phospholipid ( either a monolayer or bilayer) vesicle incorporating virus derived proteins to allow the virosomes to fuse with the target cell.

They are lipid based , synthetic vesicles consisting of viral surface glycoproteins.

They have a typical mean diameter of 150 nm.

They protect the pharmaceutically active substance from proteolytic degradation and low pH within endosomes allowing their contents to remain intact when they reach the cytoplasm.

Introduction

Virosomes are produced by dissolving the envelop of virus by a detergent or short chain phospholipid followed by the complete removal of the viral genetic material and non-membranous protein.

The viral membrane is reconstituted producing a virosomecontaining the viral membrane protein and lipid after removing the detergent or short chain phospholipid.

Viral proteins confer to the virosome based vaccine structural stability , homogeneity and immunological properties.

Structure of virosomes

It is an influenza virus.

The envelop made up of influenza lipids constitute the membrane and proteins called haemagglutinin (HA) and neuraminidase (NA) are intercalated on it.

The nucleocapsid and the genetic material of the source virus is present inside the envelop.

Virosomes act both as carrier and as adjuvant with multifunctions during the induction of an immune response.

The carrier function comprises the positive effects of embedding the antigen into a higher structure, the virosome particle.

The adjuvant function relates to the immune stimulating properties of the virosomes and their components on the immune system.

It also suceeds in stimulating specific immunity without causing non-specific inflammation.

Mechanism of action

Virosomal technology is approved by FDA for use in humans and has higher safety profile. Virosomes are biodegradable, biocompatible and non-

toxic. There is no risk of disease transmission. No autoimmunogenity or anaphylaxis. It is broadly applicable to almost all important

drugs(anti-cancer, proteins, peptides, nucleic acid, antibiotics , fungicides etc).

It enables the drug delivery into the cytoplasm of the target.

cont… 1.

Advantages

* Promotes the fusion activity in the endolysosomalpathway.

* Protects the drugs against degradation.* Extended uptake, distribution and elimination of

drug in the body.* It allows patient specific modular vaccine regime.* The fully functional activity of virosome enables

receptor mediated uptake which leads to the stimulation of both arms of the immune system such as humoral and cellular immune response.

Selection of virus

Selection of antigen

Reconstitution of virus

Method of preparation

Virosomes are reconstituted viral envelop that can be derived from different virus.

Influenza virus envelop is mostly used for preparation of virosomes but virosome can also be made from sendai virus, epstein burr virus, HIV , herpes simplex virus, newcastle disease virus.

Selection of virus

Antigen is selected as per the requirements. Eg-parasite, carcinogenic cell, bacterium or whole cell.

Cell components such as DNA, RNA or plasmid can also be used as antigen.

This antigen is coupled with lipid anchor so antigen will be ready to load on virosomes.

Selection of antigen

Reconstitution of virosome

Due to solubilisation with detergent (octaglucoside, triton x100, nonidert p-40) ,the internal viral protein and genetic material will sediment.

The detergent is later removed by different methods such as dialysis and hydrophobic resins from supernatant.

Viral matrix protein and nucleiocapsid is removed by ultracentrifugation.

Viral phospholipids(82%) and viral protein is recovered.

The antigen which is already coupled to lipid anchor is mixed with polymer or surfactant solution.

This solution is processed with virosome carrier so that antigen bound virosome is obtained.

Protein detectionVirosome preparation should generally result in a relativelyuniform protein to lipid ratio. Sodium dodecyl sulphate poly 5acrylamide gel electrophoresis can confirm the presence ofHA protein in the virosomes. Structure and sizeNegative stain electron microscopy can be generally used todetermine the ultra structure and size of virosomes. Thestaining solutions should be of neutral pH to avoid acid-induced conformational changes of HA.

cont…

Characterisation of virosomes

Fusion activity

Virosomes exhibit pH dependent membrane fusion activity similar to native influenza virus. Virosomal fusion with biological or artificial target membrane are visualised with a fluorescent resonance energy transfer assay.

Cancer treatment

Virosomes are used in the oncology field to carry peptide corresponding to tumour associated antigen as in case of peptide from parathyroid hormone related protein or from recombinant protein.

Gene delivery

Haemagglutinin, the membrane fusion protein of influenza virus is known to mediate a low pH dependent fusion reaction between the viral envelop and the limiting membrane of endosomal cell compartment following cellular uptake of virus particle by receptor mediated endocytosis.

cont…

Applications

RNA/DNA delivery

Small interfering RNA encapsulated in virosomes are able to down regulate the synthesis newly induced and constitutively expressed proteins overcoming the lack of suitable delivery methods for these molecules.

Malarial therapy

Malarial vaccine containing virosome formulated anti-malarial peptides shows a good tolerability and high specific immune response in humans.

General applications

Blood substitute for haemoglobin.

Artificial blood surrogates.

Pharmaceutical pigments or dyes.

Biological response modifiers.

Radiopharmaceutical and radio diagnosis carriers.

Drug /protein drug delivery vehicle.

Drug solubilisation enhancers.

In cosmetics and dermatology.

Drug overdose treatment.

Separation and extraction technique.

Enzyme immobilisation.

In fabrication of micro capsulated dosage form.

Antifungal, antimicrobial and antiviral therapy.

Gautham M, Pulak M, Krishnakumar KK. Journal of pharmaceutical and scientific innovation. A novel strategy for delivery of drugs and targetting.

Babar et al., J Antivir Antiretrovir 2013. Virosomes-Hybrid drug delivery system.

Sharma R, Yasir M. Virosomes- A novel carrier for drug delivery. Int. J for Pharm Tech Research. Oct-dec 2010, vol.2, no.4 , pp 2327-39.

References

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