Eye Infection with SARS-CoV-2 as a Route to Systemic Immunization?

Abstract

Infectious diseases of the conjunctiva and cornea usually leave behind both broad local and systemic immunity. Case reports of SARS-CoV-2-positive conjunctivitis with subsequent systemic immunity suggest a new route of immunization preventing the primary infection of the airways. Material and Methods: A total of 24 Syrian field hamsters were treated. In systematic animal experiments, we infected the eyes of n = 8 animals (group 1) and the airways of another n = 8 animals (group 2) with SARS-CoV-2 (Wuhan type); n = 8 hamsters served as controls (group 3). The weight development of the animals was recorded. After two weeks of observation of disease symptoms, all animals were re-exposed to SARS-CoV-2 in the respiratory tract (challenge) to determine whether immunity to the virus had been achieved. Results: The epi-ocularly infected animals (group 1) showed no clinically visible disease during the ocular infection phase. At most, there was a slightly reduced weight gain compared to the control group (group 3), while the respiratory infected animals (group 2) all lost weight, became lethargic, and slowly recovered after two weeks. After the challenge, none of the animals in groups 1 and 2 became ill again. The animals in the negative control (group 3) all became ill. Cytotoxic antibodies were detectable in the blood of the infected groups before and after challenge, with higher titers in the epi-ocularly infected animals. Conclusion: By epi-ocular infection with SARS-CoV-2, the development of systemic immunity with formation of cytotoxic antibodies without severe general disease could be observed in the experimental animals, which did not induce any more disease upon a second infection in the respiratory tract. Therefore, it can be concluded that a purely epi-ocular infection with SARS-CoV2 only induces a weak disease pattern followed by systemic immunity.

Investigation of the causative pathogen in the 2023 conjunctivitis outbreak of Nepal using unbiased metagenomic next generation sequencing

“…Though some studies have found evidences of SARSCOV2 positive conjunctivitis, this could be remnants of respiratory COVID infection in the subject because this particular hit had only few reads. [31] Our findings correlated to results of PCR tests from National Public Health Laboratory (NPHL), which found enterovirus in eight of ten samples collected from a hospital in Lalitpur, Nepal.…”

“…Though some studies have found evidences of SARSCOV2 positive conjunctivitis, this could be remnants of respiratory COVID infection in the subject because this particular hit had only few reads. [31]…”

Dissecting the ocular impact of SARS-CoV-2 variants: Analysis of eye globe and retina in animal models

“…Consistently, SARS-CoV-2 ocular tropism has been described in humans and animal models 23,24 . SARS-CoV-2 nucleocapsid protein was detected in the eye globe of a COVID-19 patient that exhibited ocular manifestations 49 .…”

Detection of Airborne Influenza A and SARS-CoV-2 Virus Shedding following Ocular Inoculation of Ferrets

“…Recovery of SCOV2 from eyelid tissue following high-dose i.n. inoculation in Golden Syrian hamsters supports the need to more closely examine ocular involvement in other mammalian models that better recapitulate the severity of COVID-19 ( 25 , 38 ), especially as studies in this model support differences in disease severity based on the route of inoculation ( 23 ). Routine collection of ocular specimens and tissues during standard pathotyping assessments for both viruses would improve our understanding regarding the frequency with which these strains exhibit extrapulmonary spread to proximal tissues.…”

“…These studies have shown that IAV (both human seasonal and zoonotic) have a capacity to replicate within mammalian ocular tissues and use the eye as a portal of entry to establish a productive, and transmissible, respiratory infection ( 2 ). However, ocular exposure to coronaviruses has been rarely evaluated in laboratory settings, with a paucity of studies in small mammalian models ( 21 – 23 ). Furthermore, ocular specimens have been only rarely collected from intranasally (i.n.)…”