The murine gammaherpesvirus 68 M2 gene is required for efficient reactivation from latently infected B cells

• Authors: Jeremy Herskowitz, Emory University; Meagan A. Jacoby, Emory University; Samuel Speck, Emory University
• Journal Title: Journal of Virology
• Volume: Volume 79, Number 4
• Publisher: American Society for Microbiology | 2005-02-01, Pages 2261-2273
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1128/JVI.79.4.2261-2273.2005
• Subjects: Health Sciences, Immunology; Health Sciences, General
• Keywords: Science & Technology; Life Sciences & Biomedicine; Virology; VIROLOGY; EPSTEIN-BARR-VIRUS; GAMMA-HERPESVIRUS INFECTION; SPLENIC LATENCY; IMMUNE-SYSTEM; 68 GENOME; T-CELLS; IN-VIVO; MODEL; MICE; PATHOGENESIS

Abstract

Murine gammaherpesvirus 68 (γHV68) infection of mice provides a tractable small-animal model system for assessing the requirements for the establishment and maintenance of gammaherpesvirus latency within the lymphoid compartment. The M2 gene product of γHV68 is a latency-associated antigen with no discernible homology to any known proteins. Here we focus on the requirement for the M2 gene in splenic B-cell latency. Our analyses showed the following. (i) Low-dose (100 PFU) inoculation administered via the intranasal route resulted in a failure to establish splenic B-cell latency at day 16 postinfection. (ii) Increasing the inoculation dose to 4 × 10 5 PFU administered via the intranasal route partially restored the establishment of B-cell latency at day 16, but no virus reactivation was detected upon explant into tissue cultures. (iii) Although previous data failed to detect a phenotype of the M2 mutant upon high-dose intraperitoneal inoculation, decreasing the inoculation dose to 100 PFU administered intraperitoneally revealed a splenic B-cell latency phenotype at day 16 that was very similar to the phenotype observed upon high-dose intranasal inoculation. (iv) After low-dose intraperitoneal inoculation, fractionated B-cell populations showed that the M2 mutant virus was able to establish latency in surface immunoglobulin B-negative (sIgD - ) B cells; by 6 months postinfection, equivalent frequencies of M2 mutant and marker rescue viral genome-positive sIgD - B cells were detected. (v) Like the marker rescue virus, the M2 mutant virus also established latency in splenic naive B cells upon low-dose intraperitoneal inoculation, but there was a significant lag in the decay of this latently infected reservoir compared to that seen with the marker rescue virus. (vi) After low-dose intranasal inoculation, by day 42 postinfection, latency was observed in the spleen, although at a frequency significantly lower than that in the marker rescue virus-infected mice; by 3 months postinfection, nearly equivalent levels of viral genome-positive cells were observed in the spleens of marker rescue virus- and M2 mutant virus-infected mice, and these cells were exclusively sIgD - B cells. Taken together, these data convincingly demonstrate a role for the M2 gene product in reactivation from splenic B cells and also suggest that disruption of the M2 gene leads to dose- and route-specific defects in the efficient establishment of splenic B-cell latency.