Constitutively Opa-Expressing and Opa-Deficient Neisseria gonorrhoeae Strains Differentially Stimulate and Survive Exposure to Human Neutrophils

TheNeisseria gonorrhoeae (the gonococcus [Gc]) opacity-associated (Opa) proteins mediate bacterial binding and internalization by human epithelial cells and neutrophils (polymorphonuclear leukocytes [PMNs]). Investigating the contribution of Opa proteins to gonococcal pathogenesis is complicated by high-frequency phase variation of theopa genes. We therefore engineered a derivative of Gc strain FA1090 in which allopa genes were deleted in frame, termed Opaless. Opaless Gc remained uniformly Opa negative (Opa− ), whereas cultures of predominantly Opa− parental Gc and an intermediate lacking the “translucent” subset ofopa genes (ΔopaBEGK ) stochastically gave rise to Opa-positive (Opa+ ) bacterial colonies. Loss of Opa expression did not affect Gc growth. Opaless Gc survived exposure to primary human PMNs and suppressed the PMN oxidative burst akin to parental, Opa− bacteria. Notably, unopsonized Opaless Gc was internalized by adherent, chemokine-primed, primary human PMNs, by an actin-dependent process. When a non-phase-variable, in-frame allele of FA1090opaD was reintroduced into Opaless Gc, the bacteria induced the PMN oxidative burst, and OpaD+ Gc survived less well after exposure to PMNs compared to Opa− bacteria. These derivatives provide a robust system for assessing the role of Opa proteins in Gc biology.