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Free keywords:
Cytotoxicity; Griscelli syndrome type 2; granuloma; hemophagocytic lymphohistiocytosis; live vaccine; primary immunodeficiency; rubella virus.
Abstract:
Background
Rubella virus-induced granulomas have been described in patients with various inborn errors of immunity. Most defects impair T-cell immunity, suggesting a critical role of T cells in rubella elimination. However, the molecular mechanism of virus control remains elusive.
Objective
To understand the defective effector mechanism allowing rubella vaccine virus persistence in granulomas.
Methods
Starting from an index case with Griscelli syndrome type 2 and rubella skin granulomas, we combined an international survey with a literature search to identify patients with cytotoxicity defects and granuloma. We performed rubella virus immunohistochemistry and PCR and T-cell migration assays.
Results
We identified 21 patients with various genetically confirmed cytotoxicity defects, who presented with skin and visceral granulomas. Rubella virus was demonstrated in all 12 accessible biopsies. Granuloma onset was typically before age 2 years and lesions persisted from months to years. Granulomas were particularly frequent in MUNC13-4 and RAB27A deficiency, where 50% of patients at risk were affected. Although these proteins have also been implicated in lymphocyte migration, 3D migration assays revealed no evidence of impaired migration of patient T cells. Notably, patients showed no evidence of reduced control of concomitantly given measles, mumps or varicella live-attenuated vaccine or severe infections with other viruses.
Conclusions
We identify lymphocyte cytotoxicity as a key effector mechanism for control of rubella vaccine virus, without evidence for its need in control of live measles, mumps or varicella vaccines. Rubella vaccine-induced granulomas are a novel phenotype with incomplete penetrance of genetic disorders of cytotoxicity.
