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.

Keywords: MALT; SARS-CoV-2; SARS-CoV-2 conjunctivitis; conjunctiva; immunization; mucosa.

Figure 1

Body weight of the group G4 with a SARS-CoV-2 intranasal primary infection then 21 days later (challenge) as intranasal re-infection with SARS-CoV-2 virus (Mean of n = 7 animals + -standard deviation) From day 2 to day 8 weight loss and recovery after 12 days.

Figure 2

Body weight of the group G2 with a SARS-CoV-2 epi-ocular primary infection then 21 days later (challenge) with intranasal re-infection with SARS-CoV-2 virus (mean of n = 7 animals + -standard deviation). From day 4 to day 8 a slight weight loss, then recovery and increase of weight.

Figure 3

Whole body plethysmographic data as dimensionless value of Penh of all hamster groups during the experiment from 12 h before infection (bi) up to 14 days post infection (dpi) with SARS-CoV-2 virus.

Figure 4

Lung weight of the right lung [g] relative to the whole body weight [g] in the different groups.

Figure 5

SARS-CoV-2-neutralising antibodies in the serum of the different groups of hamsters. The Y scale is in dilutions of serum resulting in a 50% mortality of the VeroE6 cells as described above. There is evidence of high antibody levels in the two previously infected and healed groups G2 and G4.