Cytomegalovirus pp65 limits dissemination but is dispensable for persistence
Daniel Malouli, … , Louis J. Picker, Klaus Früh
Daniel Malouli, … , Louis J. Picker, Klaus Früh
Published April 1, 2014
Citation Information: J Clin Invest. 2014;124(5):1928-1944. https://doi.org/10.1172/JCI67420.
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Research Article Virology

Cytomegalovirus pp65 limits dissemination but is dispensable for persistence

Abstract

The most abundantly produced virion protein in human cytomegalovirus (HCMV) is the immunodominant phosphoprotein 65 (pp65), which is frequently included in CMV vaccines. Although it is nonessential for in vitro CMV growth, pp65 displays immunomodulatory functions that support a potential role in primary and/or persistent infection. To determine the contribution of pp65 to CMV infection and immunity, we generated a rhesus CMV lacking both pp65 orthologs (RhCMVΔpp65ab). While deletion of pp65ab slightly reduced growth in vitro and increased defective particle formation, the protein composition of secreted virions was largely unchanged. Interestingly, pp65 was not required for primary and persistent infection in animals. Immune responses induced by RhCMVΔpp65ab did not prevent reinfection with rhesus CMV; however, reinfection with RhCMVΔUS2-11, which lacks viral-encoded MHC-I antigen presentation inhibitors, was prevented. Unexpectedly, induction of pp65b-specific T cells alone did not protect against RhCMVΔUS2-11 challenge, suggesting that T cells targeting multiple CMV antigens are required for protection. However, pp65-specific immunity was crucial for controlling viral dissemination during primary infection, as indicated by the marked increase of RhCMVΔpp65ab genome copies in CMV-naive, but not CMV-immune, animals. Our data provide rationale for inclusion of pp65 into CMV vaccines but also demonstrate that pp65-induced T cell responses alone do not recapitulate the protective effect of natural infection.

Authors

Daniel Malouli, Scott G. Hansen, Ernesto S. Nakayasu, Emily E. Marshall, Colette M. Hughes, Abigail B. Ventura, Roxanne M. Gilbride, Matthew S. Lewis, Guangwu Xu, Craig Kreklywich, Nathan Whizin, Miranda Fischer, Alfred W. Legasse, Kasinath Viswanathan, Don Siess, David G. Camp II, Michael K. Axthelm, Christoph Kahl, Victor R. DeFilippis, Richard D. Smith, Daniel N. Streblow, Louis J. Picker, Klaus Früh

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Figure 3

Δpp65ab establishes primary and secondary infections and protects against superinfection with ΔUS2-11.

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Δpp65ab establishes primary and secondary infections and protects agains...
(i) Two RhCMV seronegative male RMs (filled circles, Rh22037; open circles, Rh23016) were infected s.c. with 107 PFUs of Δpp65ab at day 1. CD4+ (blue) and CD8+ (red) T cell responses were monitored in peripheral blood (PBMCs) by intracellular cytokine staining at the indicated days using overlapping peptides of pp65ab and IE1/2. (ii) On day 659, the 2 animals were inoculated s.c. with 107 PFUs of ΔUS2-11gag (green dotted line), and the T cell response to SIVgag was measured in addition. Note the absence of a T cell response to SIVgag or pp65 and a lack of boosting of responses to IE1. (iii) On day 876, the 2 RMs were inoculated with 107 PFUs of WTgag (black dotted line), and the T cell response was monitored by intracellular cytokine staining. Note the appearance of de novo responses to SIVgag and pp65 and a boosting of the T cell response to IE1. (iv) On day 1,107, the 2 RMs were inoculated with 107 PFUs of Δpp65ab-rtn (blue dotted line). Using overlapping 15-mer peptides, a de novo response to SIVretanef was detectable, indicating superinfection. Also note a boosting of the IE1 response but not of pp65- or SIVgag-specific responses. The corresponding T cell responses obtained from BAL fluid are shown in Supplemental Figure 2.