Serological evaluation of a simplified immunization schedule using quadruple DPT-polio vaccine in Burkina Faso.

The immunogenicity of quadruple DPT-polio vaccine used in a two-dose regimen was investigated in a cross-sectional serological survey involving 355 children under 5 years of age. This schedule is currently applied in the EPI programme in three provinces in Burkina Faso, West Africa. It was found that two doses of quadruple DPT-polio vaccine induced antibodies at protective levels to diphtheria and tetanus toxin, and to the three types of polioviruses in over 90% of 179 children. The persistence of antibodies to tetanus and polioviruses is good, since over 90% of the children studied still had antibodies more than 2 years after their last vaccination. The antibodies to diphtheria toxin tend to decline in the first 6 months after vaccination, which is not uncommon. However, our data indicate clearly that a very high percentage (98%) of children have been primed to diphtheria toxin. Of 176 non-vaccinated children, up to 25% of the older ones had antibodies to polioviruses, most of them only to one type. This appears to be a sensitive parameter for the circulation of wild polioviruses in the environment. As the vaccination coverage in the study area was low (< 60%), it was to be expected that the circulation of polioviruses in the community could not be interrupted. The present study demonstrates the applicability of a two-dose strategy for primary immunization with a quadruple DPT-polio vaccine especially for poliovirus components and the toxoids. To induce pertussis immunity, however, a third vaccination is recommended.

Bovine polyomavirus, a cell-transforming virus with tumorigenic potential.

The early region of bovine polyomavirus (BPyV) was tested for its cell transformation potential employing an assay of dense focus formation. Dense foci of morphologically transformed cells were observed upon transfection of primary rodent cells with a plasmid construct encoding the complete early region of BPyV under the transcriptional control of the long terminal repeat of Rous sarcoma virus. No transformation of primary rodent cells was observed upon transfection of these cells with a plasmid encoding the complete early region of BPyV under the control of its own transcriptional regulatory sequences. In BPyV-transformed cells, the viral sequences had become integrated into the cellular genome, and expression of large T antigen could be detected in a high percentage of cells. The transformed cells were demonstrated to be capable of anchorage-independent growth and to be oncogenic in immunocompromised newborn rats. Therefore BPyV should be considered as a potentially tumorigenic polyomavirus. Since many commercial batches of calf serum have been shown to be contaminated with BPyV, our observations may have implications for the use of calf serum in cell culture.

Frequent detection of bovine polyomavirus in commercial batches of calf serum by using the polymerase chain reaction.

Twenty commercial batches of calf serum, obtained from several suppliers, were tested for the presence of bovine polyomavirus (BPyV) DNA and antibodies against the virus. Using polymerase chain reaction (PCR) technology, BPyV DNA was detected in 70% of the batches; no BPyV was detected in any of the negative control samples. The specificity of the amplification reactions was proven by hybridization. PCR results were confirmed by virus isolation experiments performed with five PCR-positive and five PCR-negative serum batches. The results indicate that the use of calf serum to supplement tissue culture media involves a serious risk of contaminating cell cultures with BPyV. No correlation was observed between the presence or absence of anti-BPyV immunoglobulins and the detection of BPyV-specific DNA sequences in the serum batches.

Human peripheral blood lymphocytes from recently vaccinated individuals produce both type-specific and intertypic cross-reacting neutralizing antibody on in vitro stimulation with one type of poliovirus.

An in vitro system of poliovirus-specific antibody production by peripheral blood B cells on stimulation by the virus has been developed. Virus-neutralizing antibodies in culture supernatant fluids, or virus-specific antibody-secreting cells (ASC) were detected by microneutralization assay and ELISA-SPOT test, respectively. After booster immunization with polio vaccine, anti-poliovirus-neutralizing ASC were present in circulation. This response was measurable between 5 and 12 days after booster vaccination. At between 12 and 90 days, another subset of B cells was found in peripheral blood that only produced poliovirus-specific neutralizing antibody after in vitro antigenic stimulation. The in vitro virus-induced response required B cells, monocytes, and T4+ (T helper) cells, and was shown to result from de novo protein synthesis. The anti-poliovirus-neutralizing response in vitro could be dissected in a type-specific and intertypic cross-reactive response by using various antigen concentrations for in vitro stimulation. Evidence was obtained by absorption studies for the existence of intertypic cross-reactive neutralization-inducing epitopes.

Induction of antigen-specific antibody response in human peripheral blood lymphocytes in vitro by a dog kidney cell vaccine against rabies virus (DKCV).

In the present report an in vitro method for obtaining a secondary human antibody response to a dog kidney cell vaccine against rabies virus (DKCV) is described. Cultures of peripheral blood mononuclear cells from normal rabies-immune and nonimmune donors were stimulated in vitro by DKCV. The production of virus-specific antibody in supernatant fluids was monitored by ELISA. Antibody was produced by lymphocytes from rabies-immune individuals, whereas those of nonimmune subjects consistently failed to produce anti-rabies antibodies after in vitro stimulation with DKCV. The generation of the anti-rabies virus antibody response of lymphocytes stimulated with DKCV was shown to be an antigen-dependent, as well as an antigen-specific process. Optimal antigen-specific responses were observed at relatively low concentrations of antigen (10(-1) to 10(-2) micrograms/culture). At increasing concentrations of antigen in culture (greater than 1 microgram/culture), the anti-rabies virus response was suppressed. Antibody produced upon stimulation was capable of neutralizing rabies virus. The response to rabies virus requires T cell help because lymphocytes depleted of SE rosetting cells did not respond to an antigenic stimulus. Studies in which the same individuals were followed over time showed a sequential development of circulating B cell subsets. The system may provide a model for the study of human B cell differentiation in vivo and in vitro and may be valuable for testing the potency of rabies vaccines in vitro.

Monoclonal antibodies to polioviruses. Comparison of intratypic strain differentiation of poliovirus type 1 using monoclonal antibodies versus cross-absorbed antisera.

A panel of 10 monoclonal antibodies raised to 3 different poliovirus type 1 strains was tested in a micro-enzyme-linked immunosorbent assay and in a micro-neutralization test against 87 poliovirus type 1 strains. The results, evaluated in a newly developed system for intratypic strain characterization, were compared with the results obtained with the classical sero-differentiation system by using a small number of strain-specific, cross-absorbed antisera. The new system not only uses results obtained with strain-specific antibody preparations, but also uses the information obtained with monoclonal antibodies reacting with less unique antigenic determinants. In a theoretical pattern fitting computer program, each virus strain could be compared with all the other strains for which serological data were stored in the memory of the computer. The results obtained with the new system coincided well with those obtained with the classical system: all except one of the strains classified as Sabin-like or intermediate in the classical system scored 'perfect fit' or 'related' with the Sabin 1 vaccine strain in the new system. Likewise, all virus isolates classified as Kuwait-like in the classical system scored 'perfect fit' or 'related' with the Dutch Kuwait-like isolate strain 78-9030.

Monoclonal antibodies to polioviruses. Production of specific monoclonal antibodies to the Sabin vaccine strains.

Murine lymphocyte hybridomas which produce neutralizing or non-neutralizing monoclonal antibodies to different type 1, 2 or 3 poliovirus strains were isolated. The majority of these monoclonal antibodies reacted with antigenic determinants present on different poliovirus strains of the same type. However, hybridomas producing monoclonal antibodies specific for each of the three Sabin vaccine strains were also generated.