Eyedrop vaccination: an immunization route with promises for effective responses to pandemics

ABSTRACT

Introduction

Mucosal vaccines have several advantages over parenteral vaccines. They induce both systemic and mucosal antigen-specific immune responses, allow easy administration, and bypass the need for trained medical personnel.

Areas covered

Eye mucosa is a novel route of mucosal vaccine administration. Eyedrop vaccination induces systemic and mucosal immune responses similar to other forms of mucosal vaccines such as oral and intranasal vaccines.

Expert opinion

Eyedrop vaccines are free of serious adverse side effects like the infiltration of CNS by pathogens. Studies over the years have shown promising results for eye drop vaccines against infectious agents like the influenza virus, Salmonella typhi, and Escherichia coli in animal models. Such efficacy and safety of eyedrop vaccination enable the application of eyedrop vaccines against other infectious diseases as well as chronic diseases. In this review of published literature, we examine the mechanism, efficacy, and safety of eyedrop vaccines and contemplate their role in times of a pandemic.

KEYWORDS:

• Eyedrop
• mucosal vaccination
• Vaccination

Article highlights

• Eyes have their own mucosa-associated lymphoreticular tissues in conjunctiva and tear ducts; protein antigen administration to the mucosal surfaces of eyes in the form of eye drops has elicited immune responses similar to other mucosal vaccines.

• Conjunctiva-associated lymphoreticular tissues and tear duct-associated lymphoreticular tissues have been proven through animal studies to function as independent mucosal inductive sites.

• Protein antigen administrations to eyes have successfully elicited immune responses against influenza virus, Toxoplasma gondii, Escherichia coli, and Salmonella typhimurium in animal studies.

• By targeting antigens like P. gingivalis, eyedrop vaccines may also play a role in the prevention or management of chronic diseases in the future.

• Eye drops may be easily applied to a large number of people in a short period of time; eye drops may be a desirable form of vaccine distribution during pandemics.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Abbreviations

(Abbreviations are listed in the order of appearance)

CMIS - common mucosal immune system

MALT - mucosa-associated lymphoid tissues

NALT - nose-associated lymphoid tissues

DC - dendritic cells

APC - antigen presenting cells

CT – cholera toxin

CNS - central nervous system

GALT – gut-associated lymphoid tissue

dmLT - double mutant heat LT

LT - Escherichia labile toxin

CALT - conjunctiva-associated lymphoreticular tissues

TALT - tear duct-associated lymphoreticular tissues

SMLN - submandibular lymph nodes

NLD - nasolacrimal ducts

PBS - phosphate-buffered saline

NDV - Newcastle disease virus

EID₅₀ - 50% embryo infectious doses

EHEC - Enterohemorrhagic E. coli

OMV - outer membrane vesicle

TLA - toxoplasma lysate antigen

TGF-ß - transforming growth factor-beta

Tregs - T cells