Comparison of active and combined passive/active immunization of Navajo children against Haemophilus influenzae type b.

In a high risk Navajo population we compared the immunogenicity of a new Haemophilus influenzae type b mutant-diphtheria toxic conjugate vaccine (HbOC) with simultaneous active (HbOC) and passive immunization with bacterial polysaccharide immunoglobulin prepared from adults immunized with H. influenzae b, pneumococcal and meningococcal vaccines. Only 7 of 26 (27%) 2-month-olds had an increase in H. influenzae b capsular polysaccharide antibody after a single dose of HbOC, a proportion similar to that of saline controls (9 of 25, 36%). After a second HbOC dose at 4 months 88% had antibody concentrations of 0.15 microgram or more, and after a third dose at 6 months all had antibody levels greater than or equal to 0.15 microgram/ml. The group receiving both HbOC and bacterial polysaccharide immunoglobulin at 2 months uniformly had H. influenzae b CP antibody concentrations of greater than or equal to 0.15 microgram/ml at 4 months (P less than 0.001 relative to "HbOC alone" group) and subsequently responded similarly to second and third doses of HbOC vaccine as did also the "HbOC alone" group. We conclude that combined passive/active immunization with bacterial polysaccharide immunoglobulin and HbOC at 2 months maintains antibody at concentrations thought to be protective (greater than or equal to 0.15 microgram/ml) without interfering with the active antibody response to second and third doses of HbOC at 4 and 6 months of age.

Superinfection rescue of an integrated defective polyomavirus genome.

We have characterized the viral sequences integrated in a polyomavirus-transformed mouse cell line, Py-3T3 (clone Py-6), and followed their excision and packaging upon superinfection. The polyomavirus sequences contained in Py-6 cells are present as a single insert of nonidentical tandem copies which includes, in addition to a normal middle T-antigen-coding region, some very rearranged sequences. Infection of Py-6 cells with polyomavirus strains encoding a normal large T antigen leads to the reproducible recovery in the resulting viral stock of specific defective viral genomes. The defective genomes contain a wild-type coding region for middle and small T antigens and intact viral origin and enhancer sequences. The remainder of the viral genome is rearranged or lost, so that there is no capacity to code for large T antigen or viral capsid proteins. The recovered defective sequences are also found integrated in Py-6 genomic DNA. Presumably, in infections of Py-6 cells, large T antigen, provided by the superinfecting virus, amplifies and excises the integrated viral sequences. The superinfecting helper virus must also produce viral capsids for packaging of the defective viral DNA and thus provides a means to shuttle the defective sequences from the mouse cells into other hosts, such as rat cells. In the latter host, the defective sequences are able to induce transformation.

Properties of cells transformed by the middle T-antigen-coding region of polyomavirus.

A series of 10 Fischer rat transformed clonal cell lines were independently obtained in infections with a defective polyomavirus containing a scrambled genome except for an intact middle and small T-antigen-coding region. These cells synthesize middle and small T antigens; no fragment of large T antigen can be detected in any of them. The transformed phenotype of this set of cell lines (designated LT-) has been studied with respect to serum dependence, saturation density, and anchorage independence and compared with the phenotype of a set of six transformants (designated LT+) which synthesize detectable to high levels of shortened or normal-sized large T antigen. Both the LT+ and the LT- groups of polyomavirus transformants display a range of transformed phenotypes. These ranges overlap, and the variations within each group are larger than the variations between the two groups. Thus, the results suggest that, for established Fischer rat fibroblasts, the maintenance of any of the three phenotypes tested and, in particular, of serum independence is not necessarily correlated with the levels of large T antigen or fragments thereof.

Expression of proto-oncogenes in normal and papovavirus-transformed or -infected rat fibroblasts.

Dot blot hybridization was used to determine the transcript levels of 10 cellular oncogenes in Fischer rat fibroblasts transformed or infected in tissue culture by polyoma virus or SV40. The level of these messages was compared to that determined for nontransformed, noninfected control cells. The analysis includes the oncogenes myc, sis, mos, erbB, erbA, Ha-ras, Ki-ras, src, fps, and abl. For all the oncogenes tested, except for mos, detectable expression was observed in all cell lines studied including the normal control cells; when normal and transformed or infected cells were compared, no significant difference in transcript level was found for any of the oncogenes except one. A slight elevation of sis message was observed for some transformants. The results of this study apply to six polyoma and seven SV40 transformants which were chosen with the purpose of analyzing transformants displaying a variety of properties. Thus, the polyoma-transformed cell lines varied in their expression of the transformed phenotype as judged by anchorage-independent growth and cell morphology, in their coding capacity for and expression of early gene products, and included two classes of rat fibroblasts transformed by ts-a mutants: those with a temperature-insensitive transformed phenotype, and those with a temperature-sensitive phenotype, A-type and N-type, respectively. Concerning the latter two types, no differences in oncogene expression were observed between cells grown at low and those grown at high temperatures, or between the two groups of cells at either temperature.

Prevention of Haemophilus influenzae type b infections in high-risk infants treated with bacterial polysaccharide immune globulin.

Apache Indian infants have a high frequency of Haemophilus influenzae type b (Hib) and pneumococcal infections. Forty percent of Hib infections in these infants occur before the age of six months, when active immunization may not be protective. To evaluate the efficacy of passive immunization with a human hyperimmune globulin (bacterial polysaccharide immune globulin [BPIG]) prepared from the plasma of immunized adult donors, we randomly assigned 703 infants in a double-blind fashion to receive 0.5 ml of BPIG per kilogram of body weight (n = 353) or 0.5 ml of saline (n = 350) intramuscularly at 2, 6, and 10 months of age. Hib-antibody levels were significantly higher in BPIG recipients than in placebo recipients at 4, 6, and 10 months of age (P less than 0.001). During the first 90 days after BPIG or placebo injection, no Hib or pneumococcal infections were detected in the BPIG group, whereas seven Hib infections (six cases of bacteremia and one of meningitis) and four pneumococcal infections (bacteremia) were detected in the placebo group (P = 0.007 and 0.06, respectively). During the fourth month, one case of Hib meningitis and two cases of pneumococcal bacteremia developed in the BPIG group, whereas there were no Hib or pneumococcal infections in the placebo group. We conclude that BPIG given at four-month intervals provided significant protection against serious Hib disease for three months, and that in high-risk infants it might be used alone, perhaps at three-month intervals, or together with active immunization.