Many paramyxoviruses appear to require cytoskeletal elements for particular steps in the virus life cycle. Measles virus and Sendai virus exhibit a requirement for microtubules in replication in vitro, whereas parainfluenza virus type 3 and RSV require actin for replication. To further elucidate the role of cytoskeletal function and rearrangement in the viral life cycle of RSV, we investigated the efficiency of virus entry, transcription, replication, and budding in the presence of a variety of pharmacological agents that stabilize or depolymerize actin or microtubules. We found that alteration of microtubule or actin function resulted in blocks at entry, formation of cell-associated virus, virus release, local cell-to-cell spread, and syncytium formation. Actin and microtubules act in cooperation to facilitate replication of RSV, although microtubules play a dominant role in the formation of cell-associated virus while actin plays a more prominent role in virus release.

Memory B cells expressing the intestinal homing marker α4β7 are important for protective immunity against human rotavirus (RV). It is not known whether the B cell repertoire of intestinal homing B cells differs from B cells of the systemic compartment. In this study, we analyzed the RV-specific VH and VL repertoire in human IgD− B cells expressing the intestinal homing marker α4β7. The mean frequency of RV-specific B cells in the systemic compartment of healthy adult subjects was 0.6% (range, 0.2–1.2). The mean frequency of IgD− B cells that were both RV specific and α4β7 was 0.04% (range, 0.01–0.1), and a mean of 10% (range, 1–32) of RV-specific peripheral blood human B cells exhibited an intestinal homing phenotype. We previously demonstrated that VH1–46 is the dominant Ab H chain gene segment in RV-specific systemic B cells from adults and infants. RV-specific systemic IgD− or intestinal homing IgD−/α4β7+ B cells in the current study also used the gene segment VH1–46 at a high frequency, while randomly selected B cells with those phenotypes did not. These data show that VH1–46 is the immunodominant gene segment in human RV-specific effector B cells in both the systemic compartment and in intestinal homing lymphocytes. The mean replacement/silent mutation ratio of systemic compartment IgD− B cells was >2, consistent with a memory phenotype and antigenic selection. Interestingly, RV-specific intestinal homing IgD−/α4β7+ B cells using the VH1–46 gene segment were not mutated, in contrast to systemic RV-specific IgD− B cells.

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