Characterizing the phenotypic and genetic changes of pre-epidemic HIV-2 group F virus following serial passage in humanized mice.

HIV-2 Group F virus with an origin in NHPs was isolated from only two individuals. Two serial passages in hu-mice showed increased viral loads, CD4+ T cell decline and nonsynonymous genetic changes showing its capacity for further evolution, and spread in the human.

Viral evolution of SIV chimpanzee toward HIV-1 using humanized mice.

HIV-1 emerged from SIVcpz evolving in humans. Humanized mice are an effective tool for assessing viral evolution via measuring viral loads, CD4+ T cell decline, and analyzing genetic changes. Four serial passages showed many non-synonymous mutations important for the adaptation and evolution of SIVcpz to human immune cells.

Zika virus induced microcephaly and aberrant hematopoietic cell differentiation modeled in novel neonatal humanized mice.

Introduction: Immunocompetent and immunocompromised murine models have been instrumental in answering important questions regarding ZIKV pathogenesis and vertical transmission. However, mimicking human congenital zika syndrome (CZS) characteristics in these murine models has been less than optimal and does not address the potential viral effects on the human immune system. Methods: Here, we utilized neonatal humanized Rag2-/-γc-/- mice to model CZS and evaluate the potential viral effects on the differentiation of human hematopoietic stem cells in vivo. Newborn Rag2-/-γc-/- mice were engrafted with ZIKV-infected hematopoietic stem cells (HSC) and monitored for symptoms and lesions. Results: Within 13 days, mice displayed outward clinical symptoms that encompassed stunted growth, hunched posture, ruffled fur, and ocular defects. Striking gross pathologies in the brain and visceral organs were noted. Our results also confirmed that ZIKV actively infected human CD34+ hematopoietic stem cells and restricted the development of terminally differentiated B cells. Histologically, there was multifocal mineralization in several different regions of the brain together with ZIKV antigen co-localization. Diffuse necrosis of pyramidal neurons was seen with collapse of the hippocampal formation. Discussion: Overall, this model recapitulated ZIKV microcephaly and CZS together with viral adverse effects on the human immune cell ontogeny thus providing a unique in vivo model to assess the efficacy of novel therapeutics and immune interventions.

Evolution of SIVmac239 following serial passaging in humanized mice.

Serial passage of SIVmac239 allows for greater understanding of the genetic changes necessary for cross-species transmission of primate lentiviruses into humans. Using humanized mice, we show that adaptive mutations continue to accumulate in SIVmac239 during four serial passages, with persistent CD4+ T cell decline and increases in plasma viral loads.

Long-term evolutionary adaptation of SIVcpz toward HIV-1 using a humanized mouse model.

Critical genetic adaptations needed for SIV chimpanzee to evolve into HIV-1 are not well understood. Using humanized mice, we mimicked the evolution of SIVcpzLB715 into HIV-1 Group M over the course of four generations. Higher initial viral load, increased CD4+ T-cell decline, and nonsynonymous substitutions arose suggesting viral evolution.

In vivo infection dynamics and human adaptive changes of SIVsm-derived viral siblings SIVmac239, SIVB670 and SIVhu in humanized mice as a paralog of HIV-2 genesis.

Simian immunodeficiency virus native to sooty mangabeys (SIVsm) is believed to have given rise to HIV-2 through cross-species transmission and evolution in the human. SIVmac239 and SIVB670, pathogenic to macaques, and SIVhu, isolated from an accidental human infection, also have origins in SIVsm. With their common ancestral lineage as that of HIV-2 from the progenitor SIVsm, but with different passage history in different hosts, they provide a unique opportunity to evaluate cross-species transmission to a new host and their adaptation/evolution both in terms of potential genetic and phenotypic changes. Using humanized mice with a transplanted human system, we evaluated in vivo replication kinetics, CD4+ T cell dynamics and genetic adaptive changes during serial passage with a goal to understand their evolution under human selective immune pressure. All the three viruses readily infected hu-mice causing chronic viremia. While SIVmac and SIVB670 caused CD4+ T cell depletion during sequential passaging, SIVhu with a deletion in nef gene was found to be less pathogenic. Deep sequencing of the genomes of these viruses isolated at different times revealed numerous adaptive mutations of significance that increased in frequency during sequential passages. The ability of these viruses to infect and replicate in humanized mice provides a new small animal model to study SIVs in vivo in addition to more expensive macaques. Since SIVmac and related viruses have been indispensable in many areas of HIV pathogenesis, therapeutics and cure research, availability of this small animal hu-mouse model that is susceptible to both SIV and HIV viruses is likely to open novel avenues of investigation for comparative studies using the same host.

Cross-Species Transmission and Evolution of SIV Chimpanzee Progenitor Viruses Toward HIV-1 in Humanized Mice.

The genetic evolution of HIV-1 from its progenitor virus SIV following cross-species transmission is not well understood. Here we simulated the SIVcpz initial transmission to humans using humanized mice and followed the viral evolution during serial passages lasting more than a year. All three SIVcpz progenitor viruses used, namely LB715 and MB897 (group M) as well as EK505 (group N) readily infected hu-mice resulting in chronic viremia. Viral loads increased progressively to higher set-points and the CD4+ T cell decline became more pronounced by the end of the second serial passage indicating viral adaptation and increased pathogenicity. Viral genomes sequenced at different time points revealed many non-synonymous variants not previously reported that occurred throughout the viral genome, including the gag, pol, env, and nef genes. These results shed light on the potential changes that the SIVcpz genome had undergone during the initial stages of human infection and subsequent spread.

Evolution of SIVsm in humanized mice towards HIV-2.

Through the accumulation of adaptive mutations, HIV-2 originated from SIVsm. To identify these evolutionary changes, a humanized mouse model recapitulated the process that likely enabled this cross-species transmission event. Various adaptive mutations arose, as well as increased virulence and CD4+ T-cell decline as the virus was passaged in humanized mice.

Mimicking SIV chimpanzee viral evolution toward HIV-1 during cross-species transmission.

HIV-1 evolved from SIV during cross-species transmission events, though viral genetic changes are not well understood. Here, we studied the evolution of SIVcpzLB715 into HIV-1 Group M using humanized mice. High viral loads, rapid CD4+ T-cell decline, and non-synonymous substitutions were identified throughout the viral genome suggesting viral adaptation.

SIVcpz cross-species transmission and viral evolution toward HIV-1 in a humanized mouse model.

HIV-1 evolved from its progenitor SIV strains, but details are lacking on its adaptation to the human host. We followed the evolution of SIVcpz in humanized mice to mimic cross-species transmission. Increasing viral loads, CD4+ T-cell decline, and non-synonymous mutations were seen in the entire genome reflecting viral adaptation.

SIV progenitor evolution toward HIV: A humanized mouse surrogate model for SIVsm adaptation toward HIV-2.

How SIV progenitors evolved into deadly HIV-1 and HIV-2 following initial cross-species transmission still remains a mystery. Here, we used humanized mice as a human surrogate system to evaluate SIVsm evolution into HIV-2. Increased viral virulence to human CD4+ T cells and adaptive genetic changes were observed during serial passages.

Zika viral infection and neutralizing human antibody response in a BLT humanized mouse model.

Many murine and non-human primate animal models have been recently developed to understand Zika viral pathogenesis. However, a major limitation with these models is the inability to directly examine the human-specific immune response. Here, we utilized a BLT humanized mouse model endowed with a transplanted human immune system. Plasma viremia could be detected within 48h after viral challenge and viremia persisted for as long as 220 days in some mice. Neutralizing human antibody was detected in infected mice and mouse sera showed reactivity with the viral envelope and capsid proteins in a radio-immunoprecipitation assay. Human monocytes/macrophages, B cells and hematopoietic stem cells in the bone marrow were found to be virus infected. These data establish that BLT mice are permissive for Zika viral infection and are capable of generating viral-specific human immune responses thus providing a human surrogate model for future testing of vaccine and antiviral therapeutic candidates.

Modeling the evolution of SIV sooty mangabey progenitor virus towards HIV-2 using humanized mice.

HIV-2 is thought to have originated from an SIV progenitor native to sooty mangabeys. To model the initial human transmission and understand the sequential viral evolution, humanized mice were infected with SIVsm and serially passaged for five generations. Productive infection was seen by week 3 during the initial challenge followed by chronic viremia and gradual CD4+ T cell decline. Viral loads increased by the 5th generation resulting in more rapid CD4+ T cell decline. Genetic analysis revealed several amino acid substitutions that were nonsynonymous and fixed in multiple hu-mice across each of the 5 generations in the nef, env and rev regions. The highest rate of substitution occurred in the nef and env regions and most were observed within the first two generations. These data demonstrated the utility of hu-mice in modeling the SIVsm transmission to the human and to evaluate its potential sequential evolution into a human pathogen of HIV-2 lineage.