Dose Response of Cold-Adapted, Reassortant Influenza A/California/10/78 Virus (H1N1) in Adult Volunteers

Comparative Study of Influenza Virus Replication in MDCK Cells and in Primary Cells Derived from Adenoids and Airway Epithelium

“…Unfortunately, we were unable to determine any significant correlation by Spearman's rank correlation analysis (P Ͼ 0.05) between degrees of restriction of ca A/California/10/78 (H1N1), ca A/Alaska/6/77 (H3N2), and ca A/Washington/897/80 (H3N2) strains in humans and those in any of the cell culture systems tested. However, our data demonstrated that the levels of attenuation of these three ca viruses in human subjects were consistently higher (ϳ2.8 logs) (10,(28)(29)(30) In this study, we observed that limited growth of ca vaccine viruses was reflected in HAEC and NHBE cultures. However, HAEC cells remain very difficult to grow and could vary between different donors, whereas the two other cell types studied are commercially available and therefore could be used from the same source/donor for different experiments.…”

“…Since the levels of replication of several wt and ca influenza A virus strains used in this study have been previously evaluated in clinical trials with adult and seronegative pediatric volunteers (10,11,28,29), we were able to compare their viral growth in humans and three tissue culture systems. Previous studies demonstrated that three ca reassortant viruses, ca A/California/10/78 (H1N1), ca A/Alaska/6/77 (H3N2), and ca A/Washington/897/80 (H3N2), exhibited different degrees of attenuation (Ͼ3.9, Ͼ4.5, and ϳ2.8 log units, respectively), as measured by comparison of mean peak viral titers (log 10 TCID 50 /ml of nasopharyngeal wash sample) between the wt and ca viruses administered at similar doses to humans (10,28,29). Unfortunately, we were unable to determine any significant correlation by Spearman's rank correlation analysis (P Ͼ 0.05) between degrees of restriction of ca A/California/10/78 (H1N1), ca A/Alaska/6/77 (H3N2), and ca A/Washington/897/80 (H3N2) strains in humans and those in any of the cell culture systems tested.…”

“…A similar pattern was observed for ca A/California/10/78 (H1N1) virus in NHBE cells isolated from a different human donor (data not shown). Despite the fact that all tissue culture models lack a functional adaptive immune system, which would obviously play a role in virus replication in the host, NHBE cells exhibited the best correlation between the degrees of restriction of viral replication of ca A/California/10/78 (H1N1), ca A/Alaska/6/77 (H3N2), and ca A/Washington/897/80 (H3N2) and those seen in clinical trials with humans (10,(28)(29)(30). ca A/New Caledonia/20/99 (H1N1), ca A/Panama/2007/99 (H3N2), and ca A/Wyoming/03/03 (H3N2) showed the lowest virus yields in NHBE cells, which were in good correlation with recently published data (6,23).…”

“…We can speculate that although NHBE cultures are able to reflect the restricted phenotype of ca influenza vaccine viruses, the lack of replication of the avian ca H9N2 vaccine virus seen in adults (18), but not in the NHBE cell model, suggests the presence of host immune factors in humans that induce innate and heterosubtypic protection against infection with avian ca vaccines. Such heterosubtypic immunity could be conferred by previous infection with influenza viruses belonging to another HA subtypes and appears to be enough to restrict to some extent the replication of human ca vaccines as well (10,28,29).…”

Principles Underlying the Development and Use of Live Attenuated Cold-Adapted Influenza A and B Virus Vaccines

“…The level of replication and the illness experienced by adult volunteers selected to have a low serum influenza A virus antibody level following experimental infection with wild-type or ca H1N1 and H3N2 reassortants are illustrated in Figure 4 and Table 2 (14,18,20,63,67,74,76,82). During experimental infection of adult humans, wild-type virus replicates to a mean peak titer of about 10 4 to 10 6 TCID 50 /mL and causes febrile or flu-like illness in 35-85% of subjects.…”