Parvoviruses are highly attractive templates for the engineering of safe, efficient, and specific gene therapy vectors, as best exemplified by adeno-associated virus (AAV). Another candidate that currently garners increasing attention is human bocavirus 1 (HBoV1). Notably, HBoV1 capsids can cross-package recombinant (r)AAV2 genomes, yielding rAAV2/HBoV1 chimeras that specifically transduce polarized human airway epithelia (pHAEs). Here, we largely expanded the repertoire of rAAV/BoV chimeras, by assembling packaging plasmids encoding the capsid genes of four additional primate bocaviruses, HBoV2–4 and GBoV (Gorilla BoV). Capsid protein expression and efficient rAAV cross-packaging were validated by immunoblotting and qPCR, respectively. Interestingly, not only HBoV1 but also HBoV4 and GBoV transduced pHAEs as well as primary human lung organoids. Flow cytometry analysis of pHAEs revealed distinct cellular specificities between the BoV isolates, with HBoV1 targeting ciliated, club, and KRT5+ basal cells, whereas HBoV4 showed a preference for KRT5+ basal cells. Surprisingly, primary human hepatocytes, skeletal muscle cells, and T cells were also highly amenable to rAAV/BoV transduction. Finally, we adapted our pipeline for AAV capsid gene shuffling to all five BoV isolates. Collectively, our chimeric rAAV/BoV vectors and bocaviral capsid library represent valuable new resources to dissect BoV biology and to breed unique gene therapy vectors.

Rapid proliferation of Plasmodium falciparum parasites in human red blood cells is the cause of malaria and is underpinned by an unconventional cell division mode, called schizogony. Contrary to model organisms, P. falciparum replicates by multiple rounds of closed and asynchronous nuclear divisions that are not interrupted by cytokinesis. Organization and dynamics of the critical nuclear division factors are, however, poorly understood. Centriolar plaques, the centrosomes of P. falciparum, are important regulators of division and serve as microtubule organizing centers. Early microscopy studies reveal an acentriolar, amorphous structure although its detailed organization remains elusive. Intranuclear microtubules mediate chromosome segregation, but the small size of parasite nuclei has precluded detailed analysis of their arrangement by classical fluorescence microscopy. We apply our recently developed STED super-resolution microscopy protocol and live cell imaging to describe the reconfiguration of microtubules during schizogony. Analysis of centrin, nuclear pore, and microtubule positioning reveals a bipartite organization of the centriolar plaque. While centrin is extranuclear, we confirm by correlative light and electron tomography that microtubules are nucleated in a previously unknown and extended intranuclear compartment, which is devoid of chromatin. This study enables us to build a working model of the organization of an unconventional centrosome and better understand the diversity of eukaryotic cell division modes.

Novel tick-borne phleboviruses in the Phenuiviridae family, which are highly pathogenic in humans and all closely related to Uukuniemi virus (UUKV), have recently emerged on different continents. How phleboviruses assemble, bud, and exit cells remains largely elusive. Here, we performed high-resolution, label-free mass spectrometry analysis of UUKV immuno-precipitated from cell lysates and identified 39 cellular partners interacting with the viral envelope glycoproteins. The importance of these host factors for UUKV infection was validated by silencing each host factor by RNA interference. This revealed Golgi-specific brefeldin Aresistance guanine nucleotide exchange factor 1 (GBF1), a guanine nucleotide exchange factor resident in the Golgi, as a critical host factor required for the UUKV life cycle. An inhibitor of GBF1, Golgicide A, confirmed the role of the cellular factor in UUKV infection. We could pinpoint the GBF1 requirement to UUKV replication and particle assembly. When the investigation was extended to viruses from various positive and negative RNA viral families, we found that not only phleboviruses rely on GBF1 for infection, but also Flavi-, Corona-, Rhabdo-, and Togaviridae. In contrast, silencing or blocking GBF1 did not abrogate infection by the human adenovirus serotype 5 and immunodeficiency retrovirus type 1, the replication of both occurs in the nucleus. Together our results indicate that UUKV relies on GBF1 for viral replication, assembly and egress. This study also highlights the proviral activity of GBF1 in the infection by a broad range of important zoonotic RNA viruses.