Cellular and humoral responses to an adenoviral vector vaccine against RSV: a first-in-human RCT.

Cicconi P, Jones C, Sarkar E, Silva-Reyes L, Klenerman P, de Lara C, Hutchings C, Moris P, Janssens M, Lisette LA, Picciolato M, Leach A, Gonzalez-Lopez A, Dieussaert I and D.Snap M. 

This paper presents the results of a novel chimpanzee-derived replication-deficient adenoviral vector vaccine against RSV (ChAd155-RSV), based on 3 RSV viral proteins including F (fusion), N(nucleocapsid), and M2-1 (antitermination). Although the intended use is in the infant population, this phase 1 first-in-human study aimed to investigate safety, reactogenicity, and immunogenicity of ChAd155-RSV in healthy adults aged 18–45 years. Adenoviral vector vaccines have shown to be able to elicit long-term cellular and humoral immune responses and are efficient in delivering foreign antigens into host cells. Although potent, the immune response elicited by this type of vaccine is dependent on the recipient’s immune status. While ChAd155-RSV antibodies could decrease the overall efficacy of the vaccine and preexisting anti-RSV NAb could mask the humoral response, a vaccine response was seen in about 60% of the high-dosage group and 20% in the low-dosage group. The key value of this study is confirmation of the ability of viral vector vaccines to intrinsically promote a combined cellular and humoral immune response to one of the most important pathogens in infancy. With low levels of preexisting antibodies against both RSV and adenovirus in the pediatric population, the potency of these vaccines in eliciting a vaccine response may be higher compared to the adult population.

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