Pulmonary morphopathology as caused by the B.1.617.2 Delta Variant

February 11, 2023 | Histopathology

In May 2021, Delta variant was designated as a variant of concern (VOC). Having a 1.4 to 1.64 increased transmissibility rate compared to Alpha VOC, it outran the other variants. Additionally, studies showed that Delta was more aggressive than the previous strains.

Regardless of the causal VOC, COVID-19 pneumonia changes the lungs and their histology. SARS-CoV-2 infected patients tend to have heavy, firm, and edematous lungs, with diffused alveolar damage (DAD) as the most prevalent condition reported among COVID-19 patients.

In the Journal of Personalized Medicine, Jeican and colleagues published their study on the histopathological findings in the Delta variant. They examined 6 male and 4 female patients, aged 40 to 83 years who died from the infection by the Delta VOC. They performed an autopsy on 4 of the patients and a postmortem lung biopsy on 6 patients. Retrieving 2 necrotic lung fragments 12 hours after the patient’s death, the researchers used one sample for virology analysis and the other for histopathology.

Macroscopic examinations showed that the most common observed lesion is acute pulmonary edema which accounted for 70% of the cases, followed by DAD. In all of the 10 autopsied cases, the lungs exhibited an increase in weight, firmer and higher consistency on palpation, and lung hepatization.

There were unique cases of plexiform lesions, which is an attribute of severe pulmonary hypertension. There was also an isolated case of bronchopneumonia and purulent and hemorrhagic secretions. With insufficient antemortem clinical data, the researchers could not directly claim an association between plexiform lesions and COVID-19.

Moreover, the immunohistochemical examination indicated that 6 patients were positive for SARS-CoV-2 proteins. Interestingly, five of the cases had SARS-CoV-2 proteins in alveolocytes; one was in an endothelial cell, a specific finding denoting that SARS-CoV-2 can cause indirect damage from thrombosis.

Despite not revealing any unique pulmonary histopathological aspects from its predecessors, the study proved that the Delta variant is one of the most aggressive strains of COVID.