• Am. J. Respir. Crit. Care Med. · Dec 2022

    Human Infection Challenge with Serotype 3 Pneumococcus.

    • Ryan E Robinson, Elena Mitsi, Elissavet Nikolaou, Sherin Pojar, Tao Chen, Jesús Reiné, Tinashe K Nyazika, James Court, Kelly Davies, Madlen Farrar, Patricia Gonzalez-Dias, Josh Hamilton, Helen Hill, Lisa Hitchins, Ashleigh Howard, Angela Hyder-Wright, Maia Lesosky, Konstantinos Liatsikos, Agnes Matope, Daniella McLenaghan, Christopher Myerscough, Annabel Murphy, Carla Solórzano, Duolao Wang, Hassan Burhan, Manish Gautam, Elizabeth Begier, Christian Theilacker, Rohini Beavon, Annaliesa S Anderson, Bradford D Gessner, Stephen B Gordon, Andrea M Collins, and Daniela M Ferreira.
    • Clinical Sciences Department, Liverpool School of Tropical Medicine, Liverpool, UK.
    • Am. J. Respir. Crit. Care Med. 2022 Dec 1; 206 (11): 137913921379-1392.

    AbstractRationale: Streptococcus pneumoniae serotype 3 (SPN3) is a cause of invasive pneumococcal disease and associated with low carriage rates. Following the introduction of pediatric 13-valent pneumococcal conjugate vaccine (PCV13) programs, SPN3 declines are less than other vaccine serotypes and incidence has increased in some populations coincident with a shift in predominant circulating SPN3 clade, from I to II. A human challenge model provides an effective means for assessing the impact of PCV13 on SPN3 in the upper airway. Objectives: To establish SPN3's ability to colonize the nasopharynx using different inoculum clades and doses, and the safety of an SPN3 challenge model. Methods: In a human challenge study involving three well-characterized and antibiotic-sensitive SPN3 isolates (PFESP306 [clade Ia], PFESP231 [no clade], and PFESP505 [clade II]), inoculum doses (10,000, 20,000, 80,000, and 160,000 cfu/100 μl) were escalated until maximal colonization rates were achieved, with concurrent acceptable safety. Measurement and Main Results: Presence and density of experimental SPN3 nasopharyngeal colonization in nasal wash samples, assessed using microbiological culture and molecular methods, on Days 2, 7, and 14 postinoculation. A total of 96 healthy participants (median age 21, interquartile range 19-25) were inoculated (n = 6-10 per dose group, 10 groups). Colonization rates ranged from 30.0-70.0% varying with dose and isolate. 30.0% (29/96) reported mild symptoms (82.8% [24/29] developed a sore throat); one developed otitis media requiring antibiotics. No serious adverse events occurred. Conclusions: An SPN3 human challenge model is feasible and safe with comparable carriage rates to an established Serotype 6B human challenge model. SPN3 carriage may cause mild upper respiratory symptoms.

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