NANOPARTICLES: “A nanoparticle (or nanopowder or nanocluster or nanocrystal) is a microscopic particle with at least one dimension less than 100 nm”

1. NANOPARTICLES IN VACCINE DELIVERY SYSTEM
NANOPARTICLES:
“A nanoparticle (or nanopowder or nanocluster or nanocrystal) is a microscopic particle
with at least one dimension less than 100 nm”
 Vaccines have a major responsible for the elimination or effective control of potentially
fatal diseases in many cases vaccines met a consequence of the inability evoking the
appropriate immune responses. To overcome this nanopartices are used to stabilize
vaccine antigens and act as adjuvants nanoscale size (<1000 nm) materials such as virus-
like particles, liposomes, ISCOMs, polymeric, and non-degradable nanospheres are used
as a potential delivery vehicles for vaccines.
 Importantly, some nanoparticles (NPs) have the ability to enter antigen-presenting cells by
different pathways, thereby modulating the immune response to the antigen. This may be
critical for the induction of protective Th1-type immune responses to intracellular
pathogens.
 Nanoparticle based delivery systems have the potential to enhance the duration of antigen
presence , enhance dendritic cell (DC)-mediated antigen uptake, direct the stimulation of
DCs, and promote cross-presentation. Nanoparticles also offer the potential to protect
antigens and adjuvant from premature enzymatic and proteolytic degradation.
 Nanoparticle delivery systems offer the added strength of multi-component loading which
is of considerable significance particularly in immunotherapy where simultaneous delivery
of antigens, immunoadjuvants, and targeting ligands is ideal.
 Application of a variety of different classes of nanoparticles in immunotherapeutic
applications. These include peptide amphiphile micelles , pH responsive polymer-based
nanoparticles , cationic liposomes , polysaccharide-based nanoparticles , and nanoparticles
formed from biodegradable polymers such as polylactic-co-glycolide (PLGA) and
polyanhydrides

2. Schematic representation of the nanocarriers:
Antigen can be conjugated to the nanoparticles surface or incapsulated into core of the
particles. Decoration of the nanoparticles surface with targeting molecules (antibodies, Fab –
fragments, peptides, etc) could further increase the delivery of particles into the antigen
presenting cells (APCs) to induce innate and adaptive immune response
DIFFERENT TYPES OF NANOPARTICLE BASED DELIVERY SYSTEMS

3. 1. LIPOSOMES
In addition to polymeric NPs, liposomes are the second most widely
explored vaccine and drug delivery vehicle in the nanomedicine field. The synthesis of
liposomes is a spontaneous process, where hydration of lipids enables the lipid bilayer
formation around an aqueous core. So far, different types of liposomes, including
unilamellar or multilamellar vesicles composed of biodegradable phospholipids (e.g.,
phosphatidylserine, phosphatidylcholin and cholesterol) were included in the vaccine
studies. Liposomes deliver vaccines by fusion with the target cell membrane. The
structurally flexible and versatile liposomes are able to encapsulate both hydrophilic and
hydrophobic substances. The hydrophilic molecules can be incorporated into the aqueous
core, while hydrophobic molecules are encased within the phospholipid bilayer.
Earlier reports have shown that delivery of antigenic proteins entrapped in multilamellar
lipid vesicles elicit strong T and B-cell responses. Similarly antigenic peptides
conjugated to phosphatidylserine (PS)-liposomes were readily internalized by APCs to
potentiate T-helper cell mediated immune responses and delivery of heat shock protein
encoding vaccine DNA using liposomes elicited strong protective immunity against
fungal infection. Because of their foreseen applications, several liposome based vaccine
nano-formulations have been approved for clinical trials against intracellular pathogens,
including viruses and M. tuberculosis . One such study already demonstrated the potency
of liposomal aerosol carriers in the generation of protective immunity against M.
tuberculosis infection. Other studies have tried a combination of dimethyl dioctadecyl
ammonium (DDA) lipid based liposomes and various immunomodulators to enhance
immunity against influenza, chlamydia, erythrocytic-stage malaria, and tuberculosis
infections. In the context of DNA vaccines, lipid-DNA complexes have been
successfully delivered to the lungs of monkeys
2. EMULSIONS
Emulsions have been long studies as adjuvant formulations and more
recently studied as vaccine delivery systems. Emulsions are dispersions of two or more
immiscible liquids composed of oil, emulsifiers and excipients.

4. Two broad classes of emulsions may be found
 Water – in- oil emulsions
 Oil in water emulsions
The most famous vaccine adjuvant emulsion is MF59 consists of squalene oil, span 85,
and tween 80 in a citrate buffer
3. POLYMERIC NANOPARTICLES
In recent years, polymeric NPs have received great attention for their
applications in the delivery of a number of vaccines. This is primarily due to their ease in
preparation, biodegradability, biocompatibility, reduced cytotoxicity, and the possibility
to fine-tune surface properties as needed. Moreover, it is relatively easy to control the
rate of vaccine release by altering the composition or ratio of co-polymers during the NP
synthesis process. The most commonly used polymeric NPs for vaccine delivery are poly
(lactic-co-glycolic acid; PLGA) or poly (lactic acid; PLA). PLGA NPs have already been
tried in the delivery of a broad range of antigens, including hydrophobic antigens,
hepatitis-B virus antigens, Bacillus anthracis, tetanus toxoid, and ovalbumin. The use of
PLGA conjugated antigens exhibited strong immunostimulatory property by inducing
cytokine and nitric oxide production against mycobacteria infection.
In addition to synthetic polymers, some natural biopolymers such as
alginate, pullans, inulins, and chitosan have been used as adjuvants. Inulin, a known
activator of the complement cascade, conferred better protection against hepatitis B and
influenza viruses. Similarly, chitosan NPs were demonstrated as nanocarrier molecules
for HBV antigens, DNA vaccine, and Newcastle disease vaccine. The delivery of PLGA
and chitosan NP conjugated vaccine molecules enhanced the immune responses at the
mucosal site. Our recent study also showed that delivery of M. tuberculosis lipids using
biocompatible chitosan NPs was able to induce significant humoral as well as cellular
immune responses when compared to lipids alone in mice. We also found that
intraperitoneal administration of these conjugates showed better activation of splenic T-
cells

5. 4. NATURAL BIOPOLYMER-BASED NANODELIVERY SYSTEMS
Natural biopolymers, including chitosan and pullulan, have been studied
as vaccine or adjuvant delivery systems. Chitosan is biocompatible, nontoxic,
biodegradable, and provides a cationic charge that may facilitate endocytosis. In the
context of vaccine delivery, chitosan displays valuable properties, including muco
adhesiveness and an adjuvanticity that acts by promoting the maturation of DCs. The
muco adhesiveness of chitosan has been exploited inmucosal vaccine delivery
formulations.
5. INORGANIC NANOPARTICLES
Some biocompatible inorganic NPs such as gold, carbon and silica have
been exploited in the vaccine delivery studies. These NPs can be synthesized in various
shapes, size and surface modified forms. Some of the viral antigens were successfully
delivered using inorganic NPs as carriers. This caused increase in antigen stability by
protecting them from premature degradation by proteolytic enzymes. Delivery of viral
and bacterial antigens using gold NPs was also found to induce quite robust host immune
responses against influenza, immunodeficiency virus, foot and mouth, and tuberculosis
diseases in mice. Encapsulation of plasmid DNA that encode mycobacterial hsp65
antigen in gold NPs exhibited significant reduction in the Mycobacterium tuberculosis,
causative agent of human tuberculosis, burden in infected mice. Few studies have used
hollow mesosporous silica, nanotube and spherical forms of carbon NPs as adjuvants to
improve the immunogenicity and delivery of protein and peptide antigens against viral
infections. Silica based NPs contain abundant silanol groups that can be utilized to
introduce specific functional groups on their surface to gain access for vaccine molecules
into target cells. The major advantages of inorganic NPs include low production cost,
reproducibility and safety in application

6. ADVANTAGES OF NANOVACCINES:
 Nanovaccine have potential to deliver are and more effective vaccine
 Nanobead covalently coupled with antigen offer distinct advantages – a low dose
of antigen is required, efficient processing by antigen presenting cells and stability
during storage
 Encapsulated nanoparticles easily deliver antigen, protects the antigen from
degradation and is found to be effective with a single dose due to slow release of
the antigen
 Many of the nanovaccine are non invasive, delivered by the oral or nasal route,
diffusion patches or microneedle arrays, thus allowing pain free delivery with
minimal damage. This is an advantage over conventional vaccine, which are
usually multi- injection, multi –dose delivery systems
 The nanoemulsion preparation of hepatitis B antigen found to be tolerable and
effective and dose not require refrigeration and it is effective for a month at 25°C
and for 6 week at 40 °C, therefore it facilitate its final distribution in small areas
villages developing countries

7. DISADVANTAGES OF NANOVACCINE
 Cost of production
 Nanomaterials can change size, shpe but not composition, which may change
their toxicity
 Small nanoparticles are cleared quickly from the body, large counterparts may
accumulate in vital organs causing toxic problems
 Reproducibility of formulation during manufacturing is one of the major hurdles
in the use of nanoparticles as vaccine

8. DEFENITION:
Nano-immuno stimulators
Nano-immuno stimulators are the nano scale (20– 100 nm) vaccine particles that can
improve the vaccine efficacy in vivo better than bulk molecules. Some of the known
nano-immuno stimulators that have been used for this specific purpose are inorganic NPs
(iron and silica), polymeric NPs (chitosan, PLGA, PVPONAlk, γ-PGA), liposomes
(cholesterol and lipids) and virus like particles (VLPs)
REFERENCE
Rashmirekha et al., Nanoparticle vaccine Against infectious disease. Frontiers in
immunology, review 2018.