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Human adenovirus type 36 (HAdV-D36) has been putatively linked to obesity in animals and has been associated with obesity in humans in some but not all studies. Despite extensive epidemiological research there is limited information about its receptor profile. We investigated the receptor portfolio of HAdV-D36 using a combined structural biology and virology approach. The HAdV-D36 fiber knob domain (FK), which mediates the primary attachment of many HAdVs to host cells, has a significantly elongated DG loop that alters known binding interfaces for established adenovirus receptors such as the coxsackie- and adenovirus receptor (CAR) and CD46. Our data suggest that HAdV-D36 attaches to host cells using a versatile receptor pool comprising sialic acid-containing glycans and CAR. Sialic acids are recognized at the same binding site used by other HAdVs of species D such as HAdV-D37. Using glycan microarrays, we demonstrate that HAdV-D36 displays a binding preference for glycans containing a rare sialic acid variant, 4-O,5-N-diacetylneuraminic acid, over the more common 5-N-acetylneuraminic acid. To date, this sialic acid variant has not been detected in humans, although it can be synthesized by various animal species, including a range of domestic and livestock animals. Taken together, our results indicate that HAdV-D36 has evolved to recognize a specialized set of primary attachment receptors that are different from known HAdV types and coincides with a unique host range and pathogenicity profile. Author summary: Most human adenoviruses do not infect animals. HAdV-D36 stands out, as it can infect a wide range of animals and cause obesity in them. It is also associated with obesity in humans. Here, we demonstrate that HAdV-D36 can use a diacetylated sialic acid monosaccharide (4-O-acetyl-Neu5Ac) as a cellular receptor. 4-O-acetyl-Neu5Ac is synthesized in animal cells but not in human cells. In humans, 4-O-acetyl-Neu5Ac is expected to be metabolized upon dietary intake and presented on cells in similarity with other non-human sialic acids. We conclude that HAdV-D36 has evolved to recognize a distinct receptor that is different from those used by other human adenoviruses. [ABSTRACT FROM AUTHOR]

Human adenovirus serotype 26 (Ad26) is used as a gene-based vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and HIV-1. However, its primary receptor portfolio remains controversial, potentially including sialic acid, coxsackie and adenovirus receptor (CAR), integrins, and CD46. We and others have shown that Ad26 can use CD46, but these observations were questioned on the basis of the inability to cocrystallize Ad26 fiber with CD46. Recent work demonstrated that Ad26 binds CD46 with its hexon protein rather than its fiber. We examined the functional consequences of Ad26 for infection in vitro and in vivo. Ectopic expression of human CD46 on Chinese hamster ovary cells increased Ad26 infection significantly. Deletion of the complement control protein domain CCP1 or CCP2 or the serine-threonine-proline (STP) region of CD46 reduced infection. Comparing wild-type and sialic acid-deficient CHO cells, we show that the usage of CD46 is independent of its sialylation status. Ad26 transduction was increased in CD46 transgenic mice after intramuscular (i.m.) injection but not after intranasal (i.n.) administration. Ad26 transduction was 10-fold lower than Ad5 transduction after intratumoral (i.t.) injection of CD46-expressing tumors. Ad26 transduction of liver was 1,000-fold lower than that ofAd5 after intravenous (i.v.) injection. These data demonstrate the use of CD46 by Ad26 in certain situations but also show that the receptor has little consequence by other routes of administration. Finally, i.v. injection of high doses of Ad26 into CD46 mice induced release of liver enzymes into the bloodstream and reduced white blood cell counts but did not induce thrombocytopenia. This suggests that Ad26 virions do not induce direct clotting side effects seen during coronavirus disease 2019 (COVID-19) vaccination with this serotype of adenovirus. IMPORTANCE The human species D Ad26 is being investigated as a low-seroprevalence vector for oncolytic virotherapy and gene-based vaccination against HIV-1 and SARS-CoV-2. However, there is debate in the literature about its tropism and receptor utilization, which directly influence its efficiency for certain applications. This work was aimed at determining which receptor(s) this virus uses for infection and its role in virus biology, vaccine efficacy, and, importantly, vaccine safety.

Adenovirus type 37 (Ad37) is one of the principal agents responsible for epidemic keratoconjunctivitis (EKC), a severe ocular infection that remains without any available treatment. Recently, a trivalent sialic acid derivative (ME0322, Angew. Chem. Int. Ed., 2011, 50, 6519) was shown to function as a highly potent inhibitor of Ad37, efficiently preventing the attachment of the virion to the host cells and subsequent infection. Here, new trivalent sialic acid derivatives were designed, synthesized and their inhibitory properties against Ad37 infection of the human corneal epithelial cells were investigated. In comparison to ME0322, the best compound (17a) was found to be over three orders of magnitude more potent in a cell-attachment assay (IC50 = 1.4 nM) and about 140 times more potent in a cell-infection assay (IC50 = 2.9 nM). X-ray crystallographic analysis demonstrated a trivalent binding mode of all compounds to the Ad37 fiber knob. For the most potent compound ophthalmic toxicity in rabbits was investigated and it was concluded that repeated eye administration did not cause any adverse effects.