Development of a diploid cell line from fetal rhesus monkey lung for virus vaccine production

Protocol for the Production of a Vaccine Against Argentinian Hemorrhagic Fever

Argentinian hemorrhagic Fever (AHF) is a febrile, acute disease caused by Junín virus (JUNV), a member of the Arenaviridae. Different approaches to obtain an effective antigen to prevent AHF using complete live or inactivated virus, as well as molecular constructs, have reached diverse development stages. This chapter refers to JUNV live attenuated vaccine strain Candid #1, currently used in Argentina to prevent AHF. A general standardized protocol used at Instituto Nacional de Enfermedades Virales Humanas (Pergamino, Pcia. Buenos Aires, Argentina) to manufacture the tissue culture derived Candid #1 vaccine is described. Intermediate stages like viral seeds and cell culture bank management, bulk vaccine manufacture, and finished product processing are also separately presented in terms of Production and Quality Control/Quality Assurance requirements, under the Adminitracion Nacional de Medicamentos, Alimentos y Tecnología Medica (ANMAT), the Argentine national regulatory authority.

Matrix and backstage: cellular substrates for viral vaccines

Vaccines are complex products that are manufactured in highly dynamic processes. Cellular substrates are one critical component that can have an enormous impact on reactogenicity of the final preparation, level of attenuation of a live virus, yield of infectious units or antigens, and cost per vaccine dose. Such parameters contribute to feasibility and affordability of vaccine programs both in industrialized countries and developing regions. This review summarizes the diversity of cellular substrates for propagation of viral vaccines from primary tissue explants and embryonated chicken eggs to designed continuous cell lines of human and avian origin.

Passage of dengue virus type 4 vaccine candidates in fetal rhesus lung cells selects heparin-sensitive variants that result in loss of infectivity and immunogenicity in rhesus macaques

Three dengue virus type 4 (DENV-4) vaccine candidates containing deletions in the 3' noncoding region were prepared by passage in DBS-FRhL-2 (FRhL) cells. Unexpectedly, these vaccine candidates and parental DENV-4 similarly passaged in the same cells failed to elicit either viremia or a virus-neutralizing antibody response. Consensus sequence analysis revealed that each of the three viruses, as well as the parental DENV-4 when passaged in FRhL cells, rapidly acquired a single Glu327-Gly substitution in domain III (DIII) of the envelope protein (E). These variants appear to have accumulated in response to growth adaptation to FRhL cells as shown by growth analysis, and the mutation was not detected in the virus following passage in C6/36 cells, primary African green monkey kidney cells, or Vero cells. The Glu327-Gly substitution was predicted by molecular modeling to increase the net positive charge on the surface of E. The Glu(327)-Gly variant of the full-length DENV-4 selected after three passages in FRhL cells showed increased affinity for heparan sulfate compared to the unpassaged DENV-4, as measured by heparin binding and infectivity inhibition assays. Evidence indicates that the Glu327-Gly mutation in DIII of the DENV-4 E protein was responsible for reduced infectivity and immunogenicity in rhesus monkeys. Our results point out the importance of cell substrates for vaccine preparation since the virus may change during passages in certain cells through adaptive selection, and such mutations may affect cell tropism, virulence, and vaccine efficacy.

Rotavirus vaccines: an overview

Rotavirus vaccine development has focused on the delivery of live attenuated rotavirus strains by the oral route. The initial "Jennerian" approach involving bovine (RIT4237, WC3) or rhesus (RRV) rotavirus vaccine candidates showed that these vaccines were safe, well tolerated, and immunogenic but induced highly variable rates of protection against rotavirus diarrhea. The goal of a rotavirus vaccine is to prevent severe illness that can lead to dehydration in infants and young children in both developed and developing countries. These studies led to the concept that a multivalent vaccine that represented each of the four epidemiologically important VP7 serotypes might be necessary to induce protection in young infants, the target population for vaccination. Human-animal rotavirus reassortants whose gene encoding VP7 was derived from their human rotavirus parent but whose remaining genes were derived from the animal rotavirus parent were developed as vaccine candidates. The greatest experience with a multivalent vaccine to date has been gained with the quadrivalent preparation containing RRV (VP7 serotype 3) and human-RRV reassortants of VP7 serotype 1, 2, and 4 specificity. Preliminary efficacy trial results in the United States have been promising, whereas a study in Peru has shown only limited protection. Human-bovine reassortant vaccines, including a candidate that contains the VP4 gene of a human rotavirus (VP4 serotype 1A), are also being studied.

Rotavirus vaccines and vaccination potential

The development of a successful rotavirus vaccine is a complex problem. Our review of rotavirus vaccine development shows that many challenges remain, and priorities for future studies need to be established. For example, the evaluation of administration of a vaccine with OPV or breast milk might receive less emphasis until a vaccine is made that shows clear efficacy against all virus serotypes. Samples remaining from previous trials should be analyzed to determine epitope-specific serum and coproantibody responses to clarify why only some trials were successful. Detailed evaluation of the antigenic properties of the viruses circulating and causing illness in vaccinated children also should be performed for comparisons with the vaccine strains. In future trials, sample collection should include monitoring for asymptomatic infections and cellular immune responses should be analyzed. The diversity of rotavirus serotype distribution must be monitored before, during, and after a trial in the study population and placebo recipients must be matched carefully to vaccine recipients. Epidemiologic and molecular studies should be expanded to document, or disprove, the possibility of animal to human rotavirus transmission, because, if this occurs, vaccine protection may be more difficult in those areas of the world where cohabitation with animals occurs. We also need to have an accurate assessment of the rate of protection that follows natural infections. Is it realistic to try to achieve 90% protective efficacy with a vaccine if natural infections with these enteric pathogens only provide 60% or 70% protection? Subunit vaccines should be considered to be part of vaccine strategies, especially if maternal antibody interferes with the take of live vaccines. The constraints on development of new vaccines are not likely to come from molecular biology. The challenge remains whether the biology and immunology of rotavirus infections can be understood and exploited to permit effective vaccination. Recent advances in developing small animal models for evaluation of vaccine efficacy should facilitate future vaccine development and understanding of the protective immune response(s) (Ward et al. 1990b; Conner et al. 1993).

Studies on in vitro interferon induction capacity and interferon sensitivity of simian foamy viruses

We demonstrate that Simian Foamy viruses (SFV) types 1, 2, 4 and 10 do not induce Interferon (IFN) production in mouse and primate (simian and human) cell lines, but that their cytopathogenic effect is blocked by this viral inhibitor. The mechanisms of action of IFN seems to be different from that of other Retroviridae. No trapping of virions appears in treated cells examined by ectron microscopy. Moreover, neither precursor nor mature virus particles were observed in infected cultures submitted to IFN treatment.

Activation of metastatic potential in African green monkey kidney cell lines by prolonged in vitro culture

Studies on the tumorigenicity of Vero kidney cells of Cercopithecus aethiops monkey origin were extended to various passage levels of BSC-1 aneuploid cells and to low passage CV-1 diploid cells (derived also from C. aethiops monkey kidney). It was found that BSC-1 cells -- like Vero cells -- showed increased tumorigenicity with increasing passage level in antithymocyte globulin (ATG) treated newborn rats and in nude mice. Cells passaged over 250 times in cultures formed invasive adenocarcinomas in newborn rats. Their malignant tumor growth was further demonstrated around the 500 passage level when tumor metastases were detected in the lungs of four of the 14 inoculated rats. Vero cells induced such lung metastases in rats already at passage 227. CV-1 diploid cells at low passage level produced small nodules of epithelioid cells in newborn rats at 6th day after inoculation that had disappeared by the 21st day, and caused no local invasion nor lung metastasis. In vitro tumorigenicity tests on BSC-1 and CV-1 cells, using chick embryo skin, human muscle and colony formation in agarose, confirmed the animal test results. The results of this study indicate that BSC-1 and Vero cell lines at low and high passage levels may prove to be useful tools to study the molecular basis of malignancy.

Primary isolation and serial passage of hepatitis A virus strains in primate cell cultures

Although several primate cell types have been reported to support replication of hepatitis A virus, optimal conditions for the isolation and production of quantities of virus have not been defined. We therefore examined seven different primate cell types for their ability to support replication of primate-passaged and wild-type virus as reflected by intracytoplasmic accumulation of viral antigen (direct immunofluorescence and radioimmunoassay) and propagation of cell culture-adapted virus. Of the cells tested, low-passage African green monkey kidney (AGMK) cells were most sensitive for initial isolation. Viral replication was documented after inoculation of AGMK cells with seven of nine hepatitis A virus antigen-positive fecal specimens (from seven epidemiologically distinct sources). With six inocula, virus was successfully passed in serial cultures. AGMK-adapted virus was readily propagated in continuous AGMK (BS-C-1) cells. The optimal temperature for the growth of virus in BS-C-1 cells was 35 degrees C. Viral release into supernatant fluids was documented in the absence of any cytopathic effect, and infectivity titers in supernatant fluids 21 days after inoculation (50% tissue culture infective does [TCID50], 10(6.0)/ml) equalled or exceeded those in the cell fraction (TCID50, 10(5.5)/ml). Cells maintained in serum-free media readily supported viral growth, with yields of virus (TCID50, 10(6.5)/ml) equal to or greater than those obtained with cells maintained in 2% fetal bovine serum.

Characterisation of a polyomavirus in two foetal rhesus monkey kidney cell lines used for the growth of hepatitis A virus

Electron microscopy and prolonged incubation of cell cultures have revealed the presence of a papovavirus in two foetal rhesus monkey kidney cell lines, FRhK-4 and FRhK-6, which are used to grow hepatitis A virus. The papovavirus, designated FRKV, was present in culture fluids from both cell lines and in thin sections of FRhK-4 cells. The size of the virus, 47 nm, places FRKV within the Polyomavirus genus. FRKV has been grown in primary human embryo kidney and calf kidney cell cultures. Haemagglutinin has not been demonstrated. Preliminary investigations indicate that FRKV is antigenically identical to or closely related to stump-tailed macaque virus and is not one of the primate polyomaviruses SV40, SA12, BK or JC. FRKV reacts with antibody that occurs in pools of foetal and newborn bovine sera suggesting that the virus might be of bovine origin.

Dengue-2 vaccine: preparation from a small-plaque virus clone

The S-1 clone of dengue type 2 virus was used for the preparation of a live-attenuated vaccine after passage in DBS-FRhL-2 cell culture. The vaccine virus had a relatively higher replicative capacity at superoptimal temperatures than its precursor virus, S-1, passaged in primary green monkey kidney cells (S-1 PGMK). There was also a tendency for the S-1 vaccine virus to exhibit leakiness at increased temperatures. Another in vitro marker, replication in monkey peripheral blood leukocytes, indicated less host restriction for the S-1 vaccine in comparative assays with S-1 PGMK virus. Mouse virulence appeared to remain stable on passage in DBS-FRhL-2 cells, whereas monkey immunogenicity decreased. Cautious trials of the dengue type 2 S-1 vaccine in humans are indicated.

Extensive chromosome aberrations caused by [3H]thymidine incorporation in a diploid monkey cell line DBS-FRhL-2

Extensive chromosome aberrations were induced in a diploid monkey cell line designated as DBS-FRhL-2 after exposure to [3H]thymidine ([3H]Tdr) for either 30 or 60 min at a dose of 1 muCi per ml of medium. Cultures exposed to [3H]Tdr for a longer period had significantly larger numbers of aberrations than those exposed for a shorter period. The most common type of aberrations were chromatid breaks. The majority of aberrations were observed in cells which were in contact with [3H]Tdr during S phase, especially the middle S. Cells from cultures of early and late passages exposed to [3H]Tdr were affected to a similar extent when chromosomes were examined. No clear relationship between sites of breakage and intensity of labeling could be established.