Janet S. Bootman

Alterations in the hemagglutinin associated with adaptation of influenza B virus to growth in eggs

In 1943 Burnet reported on changes in the hemagglutinating properties of human influenza virus which occurred during adaptation of the virus to growth in chicken eggs. Only recently has direct evidence been presented that these changes affect the antigenic properties of the virus. Schild et al. (G. C. Schild, J. S. Oxford, J. C. deJong, and R. G. Webster (1983), Nature (London) 303, 706-709) demonstrated that egg adaptation of influenza B virus selects variants which are antigenically distinct from virus grown from the same source in mammalian cells. The molecular changes in the hemagglutinin (HA) of influenza B virus associated with adaptation to growth in eggs have now been identified. A specific glycosylation site at the distal tip of the HA of influenza B virus grown exclusively in mammalian cell culture is lost or altered during egg adaptation. Since the HA functions in adsorption of virus to cells, it is concluded that removal or modification of an oligosaccharide structure at this position is required for influenza B virus to attach to and infect the allantois cells of the egg and that this has important implications for the antigenic configuration of the molecule.

Immunization with class I human histocompatibility leukocyte antigen can protect macaques against challenge infection with SIVmac-32H.

Objective: To evaluate the efficacy of immunopurified class I human histocompatibility leukocyte antigen (HLA) to protect against SIV infection. Methods: HLA class I antigens were immunopurified from a human B‐lymphoblastoid cell line. Groups of four macaques were vaccinated subcutaneously with four doses of the immunogen in adjuvant, or with adjuvant alone and subsequently challenged intravenously with 10 median monkey infectious doses of cell‐free SIVmac‐32H. Infection was determined by polymerase chain reaction for SIVmac proviral DNA and by virus isolation. Antigen‐specific humoral and cellular immune responses were monitored. Results: Macaques immunized with the HLA molecules produced anti‐HLA class I antibodies that inhibited SIV replication in vitro and downregulated autologous T‐cell proliferation against irradiated C8166 cells. They were partially protected (two out of four) from virus infection for at least 33 weeks when challenged with SIV grown in human cells. All four control animals were infected. Conclusions: This demonstration of partial protection, together with our previous work reporting that vaccination with allogenic cynomolgus lymphocytes can protect against challenge infection with SIV grown in simian cells, suggests that allogenic immune response induced before or during establishment of HIV infection may have important implications for AIDS disease progression.

A host-cell-selected variant of influenza B virus with a single nucleotide substitution in HA affecting a potential glycosylation site was attenuated in virulence for volunteers.

SummaryAn influenza B virus was passaged in man (virus A) and then in human embryo trachea (C) and into embryonated eggs (D) or directly into eggs (B). Virus A, B, and C had the same (cell-like) haemagglutinin phenotype on reaction with selected monoclonal antibodies while D had an “egg-like” phenotype. The viruses were administered at a dose of 1,000 TCD50 (for MDCK cells) by intranasal inoculation to groups of 27 or 28 volunteers. Viruses A, B, and C all produced disease in six to eight volunteers, whereas D produced no illness and only four volunteers were infected. The viruses shed by the volunteers were indistinguishable from those with which they were inoculated. The haemagglutinin genes of the viruses were sequenced and changes were detected indicating amino acid substitutions at position 196–198 in the attenuated egg-grown virus D whereby a potential glycosylation site present in the other viruses was lost.

Sequence analysis of the hemagglutinin of B/Ann Arbor/1/86, an epidemiologically significant variant of influenza B virus.

Influenza B/Ann Arbor/1/86 is representative of antigenic variants responsible for the most important influenza epidemics during the 1985/1986 season. The nucleotide sequence of the hemagglutinin HA1 region and the deduced amino acid sequence are presented. Compared to the previous winters vaccine strain B/USSR/100/83, B/AA/1/86 possesses 18 amino acid substitutions and 2 amino acid insertions, 50% of which are distributed within the vicinity of the reported single immunodominant antigenic site.

The antigenic structure of a human influenza A (H1N1) virus isolate grown exclusively in MDCK cells

A panel of monoclonal antibodies has been produced against a 1983 human influenza A (H1N1) virus that has been isolated and grown exclusively in MDCK cells. Several of these antibodies were used to select variants from MDCK-derived virus in cells and their epitopes were then located by determining the HA1 amino acid sequence. The operational antigenic map of the haemagglutinin indicates the presence of two distinct immunodominant antigenic regions which correspond but are not identical to antigenic sites Sa and Sb of the A (H1N1) virus A/PR/8/34. Also during this study, we characterized a unique group of antibodies for which variants require two distinct and specific HA1 amino acid substitutions to escape neutralization.