Andoh, T. F. | bioRxiv Science

bioRxiv2025

The human cytomegalovirus chemokine binding protein UL22A is necessary for efficient reactivation from latency in CD34+ hematopoietic progenitor cells.

Herpesviruses and Poxviruses encode secreted chemokine binding proteins that prevent the interaction between chemokines and their cognate G protein coupled receptors to alter chemotactic gradients and intracellular signaling pathways. Human cytomegalovirus (HCMV) encodes the secreted protein UL22A (formerly UL21.5), which is described as a CCL5 (RANTES) binding protein and requires sulfation at two tyrosine residues (Y65 and Y69) for efficient RANTES interaction. In this report, we show that the UL22A protein, and the UL22A Y65 and Y69 residues are necessary for efficient HCMV reactivation from latency in CD34+ hematopoietic progenitor cells and that UL22A expression is essential for reactivation in a humanized mouse model of latency. However, RANTES neutralization is not sufficient to complement the in vitro reactivation defect of UL22A mutant viruses. These data suggest that UL22A plays an important role in latency, possibly through interactions with additional chemokines or other types of ligands via its tyrosine residues, in order to mediate efficient HCMV reactivation. IMPORTANCEHCMV is a ubiquitous herpesvirus that infects 60-90% of the population worldwide. In immunocompetent individuals, primary infection is asymptomatic and results in lifelong latent infection in CD34+ hematopoietic progenitor cells (HPCs). Viral reactivation remains a major complication for immunosuppressed individuals, but current therapeutics targeting HCMV replication show significant toxicity. Thus, a better understanding of the mechanisms controlling latency and reactivation is necessary to develop new therapeutics targeting these stages of the HCMV lifecycle. We show that virus lacking the HCMV chemokine binding protein UL22A is incapable of efficient reactivation in CD34+ HPCs and in vivo. UL22A tyrosine residues important for interaction with the chemokine RANTES are necessary for reactivation. However, neutralizing RANTES does not complement the reactivation defect of UL22A mutant viruses, demonstrating that UL22A has functions other than RANTES binding. Together, our results reveal a novel role for UL22A in HPCs and a new understanding of UL22A-chemokine interactions.

microbiology↗

bioRxiv2025

Infection Of Rhesus Macaques With Onyong-nyong Virus UVIR-O804 Recapitulates Key Aspects of Human Clinical Disease

1.Onyong-nyong virus (ONNV) is a mosquito-borne alphavirus first isolated in Uganda in 1959. Since its discovery, ONNV has caused several outbreaks in Africa, manifesting clinically as fever, rash, and joint/muscle pain lasting months. Currently, we have a limited understanding of ONNV infection and disease in relevant animal models, which restricts the evaluation of vaccines and therapeutics. In 1967, Binn et al. reported that infection of rhesus macaques (RMs) with ONNV failed to induce viremia in two animals. This may be attributed to the potential attenuation of the virus through extensive passaging. To mitigate this issue, we constructed an infectious clone from the sequence of ONNV-UVRI0804 (ONNV0804), a 2017 clinical isolate from a febrile patient in Uganda. This strain demonstrated high pathogenicity in immunocompetent mice, resulting in an earlier and more severe onset of disease and significantly higher viremia compared to a highly passaged control strain ONNVUgMP30. In the current study, three male and three female rhesus macaques were subcutaneously inoculated with ONNV0804. All animals became viremic at 2 days post inoculation (dpi). Both classical and nonclassical monocytes were activated (CD169+), peaking at 3 dpi, which corresponded with the peak of viremia. Additionally, CD4+ and CD8+ effector memory T cells and memory B cells began proliferating in peripheral blood by day 7, peaking at day 10, which also corresponded to the timing of neutralizing antibody development, indicating a robust adaptive immune response to ONNV0804. Finally, key clinical disease manifestations were recapitulated, including lymphadenopathy and histological features of early-stage arthritis. Taken together, rhesus macaque infection with ONNV0804 clinical isolate is a promising model for investigating immune responses to alphaviruses and evaluating vaccines to protect against future epidemics. 2. Author summaryOnyong-nyong virus (ONNV) is a mosquito-transmitted alphavirus that causes fever, rash, and prolonged joint and muscle pain, similar to chikungunya virus and other arthritogenic alphaviruses. Despite its capacity to cause outbreaks in Africa, ONNV remains understudied, and there are currently no approved vaccines or therapeutics to prevent or treat infection and disease. A major barrier to advancing ONNV research has been the lack of suitable animal models to study the virus and investigate host immune responses. We engineered an ONNV infectious clone of a recent clinical isolate sequenced from a patient in Uganda (ONNV0804) that causes robust infection and disease in immunocompetent mice. In the current study, we provide data demonstrating that this contemporary ONNV strain infects rhesus macaques. Notably, rhesus macaques developed detectable viremia, rash, lymphadenopathy, joint and muscle inflammation, and strong innate and adaptive immune responses following subcutaneous ONNV0804 infection. These findings suggest that ONNV0804 infection in macaques is a promising model for studying ONNV pathogenesis and immunity. This model will be instrumental for evaluating future vaccine and therapeutic candidates aimed at preventing ONNV infection and related viral disease.

microbiology↗