Phenotypic expression of HA-NA combinations in human-avian influenza A virus reassortants

Abstract

Human-avian and human-mammalian influenza A virus reassortant clones with the neuraminidase (NA) gene of the A/USSR/90/77 (H1N1) strain and hemagglutinin (HA) genes of H3, H4 and H13 subtypes had been shown in an earlier publication to produce low HA yields in the embryonated chicken eggs. The low HA titers had been shown to be due, at least in part, to the formation of virion clusters at 4 degrees C; the clustering was removed by the treatment with bacterial neuraminidase [Rudneva et al., Arch. Virol (1993) 133: 437-450]. By serial passages of the reassortants in chick embryos non-aggregating variants were selected: the variants produced HA titers of the same order as A/USSR/90/77 parent virus. The assessment of the virus yields by the analysis of the partially purified virus preparations from fixed volumes of the allantoic fluid revealed that actual virion yields of the initial reassortants were lower than the yields of their passaged variants or of the parent viruses. The passaged variant of a reassortant possessing the HA gene of A/Duck/Ukraine/1/63 (H3N2) virus differed from the original (non-passaged) reassortant and from the parent A/Duck/Ukraine/1/63 virus in the reaction with a panel of monoclonal antibodies against H3 hemagglutinin. The data suggest that some HA-NA combinations may lead to an incomplete functional match between HA and NA and to the formation of low-yield reassortants, thus representing a possible limiting factor in the emergence of new HA-NA combinations in natural conditions.

Interdependence of Hemagglutinin Glycosylation and Neuraminidase as Regulators of Influenza Virus Growth: a Study by Reverse Genetics

“…Otherwise, the enhanced receptor binding is a serious disadvantage in the late stage of infection because it prevents the release of progeny viruses from host cells. The need for such a match of HA and NA activities had so far only been deduced from studies analyzing natural virus isolates or laboratory-generated reassortants (15,16,22,32). Taken together, our data represent the first concise study of the functional interrelationship of distinct HA and NA species and provide experimental evidence for the strict requirement of a fine tuning of HA receptor-binding and NA receptor-destroying activity in order to allow efficient influenza virus propagation (Fig.…”

“…When different natural and laboratory-derived influenza viruses were analyzed for their HA and NA composition, it was striking to see that some combinations of antigenic subtypes occurred quite frequently while others were never detected (18,32). In the latter case, the failure to produce stable highyield reassortant strains with some HA and NA combinations has been attributed to an incompatibility between the opposing activities of these two glycoproteins leading to viral aggregation.…”

NP, PB1, and PB2 Viral Genes Contribute to Altered Replication of H5N1 Avian Influenza Viruses in Chickens

“…One possible reason may be that HA-NA incompatibility is responsible for inefficient replication of the rIndo/rEgret NA reassortant virus in 293T cells or ECEs. The HA and NA proteins of influenza work together to efficiently bind and release virus from the cells during replication, and it is known that HA-NA incompatibility can result in inefficient viral replication or aggregation on the cell (10,44). The importance of a balanced HA-NA relationship often results in the coevolution of NA along with changes in HA of influenza viruses to maintain a functional unit (34,35,57).…”

Exploitation of Nucleic Acid Packaging Signals To Generate a Novel Influenza Virus-Based Vector Stably Expressing Two Foreign Genes

“…We have demonstrated that sequences in the 3Ј and 5Ј ends of the coding regions within the HA (the present study), NA (6), M (J. Maeda and Y. Kawaoka, unpublished data), and NS (K. Fujii and Y. Kawaoka, unpublished data) vRNAs are required for their efficient incorporation into virions, suggesting that packaging of vRNA segments (most likely as a viral ribonucleoprotein complex) is mediated by RNA-RNA interactions occurring in trans among the viral RNA segments. If so, specific incorporation signals within each segment may restrict reassortment, just as functional interactions (e.g., formation of the polymerase complex [12], HA-NA [12,16,21,32,33,38], and cleavable HA-M2 functional associations [10,11,26,36]) restrict the random reassortment of viral proteins. In this context, it is interesting that in both the 1957 and 1968 pandemics, the PB1, HA, and/or NA genes were introduced into human viruses from avian viruses (17), suggesting a possible link between the HA and PB1 RNA segments.…”