Convalescence from prototype SARS-CoV-2 protects Syrian hamsters from disease caused by the Omicron variant

Abstract

The mutation profile of the SARS-CoV-2 Omicron variant poses a concern for naturally acquired and vaccine-induced immunity. We investigated the ability of prior infection with an early SARS-CoV-2, 99.99% identical to Wuhan-Hu-1, to protect against disease caused by the Omicron variant. We established that infection with Omicron in naive Syrian hamsters resulted in a less severe disease than a comparable dose of prototype SARS-CoV-2 (Australia/VIC01/2020), with fewer clinical signs and less weight loss. We present data to show that these clinical observations were almost absent in convalescent hamsters challenged with the same dose of Omicron 50 days after an initial infection with Australia/VIC01/2020. The data provide evidence for immunity raised against prototype SARS-CoV-2 being protective against Omicron in the Syrian hamster model. Further investigation is required to conclusively determine whether Omicron is less pathogenic in Syrian hamsters and whether this is predictive of pathogenicity in humans.

Pathogenicity of SARS-CoV-2 Omicron in Syrian hamsters and its neutralization with different Variants of Concern

“…The disease characteristics of the Omicron variant observed here are similar to those reported for other SARS-CoV-2 variants like Alpha, Beta, Kappa and Delta in hamsters by earlier studies except that of the body weight loss [9,19,32,33]. Our finding corroborated with the few recent studies which also reported the limited or negligible body weight loss in hamsters post infection with Omicron variants [22][23][24][25][26]. The age and virus dose can affect the body weight loss and disease severity in hamsters post SARS-CoV-2 infection [20,32].…”

“…The virus titration showed early virus clearance from the nasal turbinates by day 5 and from lungs by day 7. We found no evidence that Omicron produce less severe lung disease or more predilection to upper respiratory tract in comparison to lung as reported earlier [20,22,23,24].…”

“…The age and virus dose can affect the body weight loss and disease severity in hamsters post SARS-CoV-2 infection [20,32]. We have used 5-6 week old hamsters and other published studies on Omicron infection in Syrian hamsters have also used animals of the age range of 4 to 8 weeks except Ryan et al, have used 20-22 week animals [22]. Even high Omicron virus doses could not result in body weight loss in hamsters [23].…”

“…The model have been effectively used for the studies on the vaccines, antivirals, pathogenesis, transmissibility, virus shedding and disease severity associated with SARS-CoV-2 VOC's [9,[11][12][13][14][15][16][17][18][19][20][21]. Recently, few studies have been published on the pathogenesis aspect of Omicron variant in mice and Syrian hamsters in comparison with other VOC's demonstrating decreased severity of infection [22][23][24][25][26][27].…”

An Interpretable Deep Learning Model for Predicting the Risk of Severe COVID-19 from Spike Protein Sequence

“…56,57 Omicron has also been found to be less infective in the lung and cause less severe disease in a Syrian hamster model. 58,59 The decrease in severe disease is also consistent with preliminary clinical and epidemiological evidence that had emerged by the time of this manuscript's submission, suggesting that patients had less severe disease in South Africa. 60 Reduced severe disease in South Africa may be due to a particularly high degree of seroprevalence in South Africa as a result of prior infection and vaccination of the vulnerable population.…”