Mokola Virus Research Articles

Protection from rabies by a vaccinia virus recombinant containing the rabies virus glycoprotein gene.

Inoculation of rabbits and mice with a vaccinia-rabies glycoprotein recombinant (V-RG) virus resulted in rapid induction of high concentrations of rabies virus-neutralizing antibodies and protection from severe intracerebral challenge with several strains of rabies virus. Protection from virus challenge also was achieved against the rabies-related Duvenhage virus but not against the Mokola virus. Effective immunization by V-RG depended on the expression of a rabies glycoprotein that registered proline rather than leucine as the eighth amino acid from its NH2 terminus (V-RGpro8). A minimum dose required for effective immunization of mice was 10(4) plaque-forming units of V-RGpro8 virus. beta-propiolactone-inactivated preparations of V-RGpro8 virus also induced high levels of rabies virus-neutralizing antibody and protected mice against intracerebral challenge with street rabies virus. V-RGpro8 virus was highly effective in priming mice to generate a secondary rabies virus-specific cytotoxic T-lymphocyte response following culture of lymphocytes with either ERA or PM strains of rabies virus.

Arthropod studies with rabies-related Mokola virus.

A cell culture-adapted variant of the rabies-related Mokola virus was demonstrated to replicate in inoculated Aedes aegypti mosquitoes. Replication was slow compared to many arboviruses in their vectors. Maximum titers were not obtained until after approximately 6 weeks of extrinsic incubation. Mokola virus underwent nine mosquito-mosquito passages at approximately monthly intervals and was thus maintained in insects for 340 days before terminating the study. Virus antigen was detected by immunofluorescence in a variety of mosquito tissues and organs, including salivary glands, but primarily in nervous tissue. Irrefutable virus transmission by bite could not be demonstrated because of equivocal results. Transovarial passage of virus was observed in the mosquito. Viremia in baby mice was demonstrable. Ornithodoros moubata nymphal ticks were exposed to viremic mice but failed to become infected.

Premier isolement du virus Mokola à partir d'un rongeur ( Lophuromys sikapusi)

Summary An isolate of Mokola virus (AnRB3247) was obtained from the brain of a wild rodent Lophuromys sikapusi caught in the Central African Republic. This was the first isolation of Mokola virus from a rodent and the first isolation of this virus in the Central African Republic. This isolate was identified with Mokola virus by complement fixation and seroneutralization tests. The antigenic pattern of this isolate was determined with a panel of monoclonal antibodies, and was compared to those of Mokola isolates from Nigeria and Cameroun, of Lagos bat virus and of Duvenhage virus.

Mokola virus infection in cats and a dog in Zimbabwe.

Mokola virus infection in cats and a dog in Zimbabwe.

Rabies serogroup viruses in neuroblastoma cells: propagation, "autointerference," and apparently random back-mutation of attenuated viruses to the virulent state.

Each of several strains of fixed rabies virus was found to replicate to high titers in C1300 mouse neuroblastoma (clone NA) cells, without adaptation. Rabies serogroup Lagos bat, Mokola, and Duvenhage viruses also replicated efficiently in NA cells. Kotonkan and Obodhiang viruses replicated efficiently after adaptation, to titers not previously obtained in vitro. Infection in NA cells was frequently more cytopathic than in BHK-21 cells, allowing titration of Kotonkan and Obodhiang viruses by plaque assay. Duvenhage virus caused syncytium formation. Serial propagation of rabies viruses at a high multiplicity of infection in NA cells led to a rapid decline in virus yields; similar "autointerference" has not previously been demonstrated with rabies virus in other cell systems. Rabies virus infection in NA cells exhibited extreme sensitivity to interference by experimentally added defective interfering virions. Although several strains of attenuated rabies virus consistently reverted rapidly to virulence after propagation in NA cells, other strains of attenuated rabies and rabies serogroup viruses acquired increased virulence at a more gradual rate or not at all, suggesting that diverse characters may control virulence. When attenuated Flury HEP rabies virus was serially propagated at a low multiplicity of infection in either NA cells or suckling mouse brain, virulence appeared at a very variable rate, indicating that these systems may selectively enhance replication of randomly occurring virulent virus mutants.

Antigenic characterization of the bangui strain (ANCB-672d) of lagos bat virus

The newly isolated strain of Lagos bat virus (ANCB-672d) has been compared with the prototype strain by means of the kinetic neutralization of fluorescent foci in CER-cell culture. The two strains are identical when neutralized by the Lagos bat prototype immune serum, but are readily distinguishable when tested against the immune serum prepared with the ANCB-672d strain. Furthermore the relationship between Mokola virus are closer with the ANCB-672d strain than with the Lagos bat prototype strain: the immune serum to Mokola virus reacts more rapidly with the ANCB-672d strain than with the prototype strain of Lagos bat virus. To the contrary, rabies (CVS) virus and Duvenhage virus immune sera do not differenciate between the two strains of Lagos bat virus.

Synthesis of RNA by mutants of vesicular stomatitis virus (Indiana serotype) and the ability of wild-type VSV New Jersey to complement the VSV Indiana ts G I-114 transcription defect

The ability of certain vesicular stomatitis virus (VSV; Indiana serotype) temperature-sensitive (ts) mutants to synthesize intracellular viral complementary RNA (vcRNA) at permissive or nonpermissive temperatures for productive infections has been investigated. Mutants belonging to complementation groups II, III, and V synthesize RNA at nonpermissive temperature in amounts essentially equivalent to that obtained at permissive temperatures. Mutant ts G I-114 possesses a thermolabile transcriptase and does not synthesize vcRNA at 40 degrees C; however, mutants ts O I-5, O I-53, O I-78, and O I-80 possess thermostabile transcriptases that are capable of some vcRNA synthesis at 40 degrees C. All five group I mutants are defective in their secondary transcription ability at 40 degrees C. Wild-type VSV New Jersey virus is able to complement the transcription defect of ts G I-114 at 40 degrees C. This complementation is inhibited by puromycin, suggesting that a viral gene product of VSV New Jersey (e.g., its transcriptase or a transcriptase component) is involved. Mokola virus is not able to complement the ts G I-114 defect, although Mokola does synthesize vcRNA in infected cells (in the presence or absence of cycloheximide).

Relationship of two arthropod-borne rhabdoviruses (kotonkan and Obodhiang) to the rabies serogroup.

Indirect immunofluorescence confirmed the antigenic relationship between kotankan and Obodhiang viruses and Mokola virus that had originally been shown by complement fixation test. This relationship suggests inclusion of these two arthropod isolates in the rabies subgroup of the Rhabdoviridae family. Cross-reactivity with Mokola virus was also demonstrated by direct immunofluorescence but was easily eliminated when conjugates were diluted. No crossreactivities were found by neutralization tests or by surface immunofluorescence. Other than these immunological ties to the rabies serogroup, other biological characteristics of kotonkan and Obodhiang viruses were distinct. Maximum yield of infectivity of kotonkan and Obodhiang in cell culture was at 30 C, antigen usually filled the cytoplasm of infected cells diffusely, and syncytia were formed before severe cytonecrosis. By electron microscopy, virus particles and their nucleocapsids appeared cone shaped (mean lengths: kotonkan, 182 nm; Obodhiang, 170 nm). Viral morphogenesis took place on plasma membranes of cells in culture, mouse brain neurons, and inflammatory cells (macrophages) in brain lesions. All of these characteristics of the two viruses, and the known association of kotonkan virus with an acute, febrile illness of cattle in Nigeria, suggest a biological relationship with bovine ephemeral fever virus. The latter is known to exist in the same geographic area but exhibits no serological cross-reaction with either kotonkan or Obodhiang virus. The question of whether these two viruses deserve placement in an expanded rabies subgroup (at the cost of a less precise definition of the subgroup) or in a separate subgroup (which would include bovine ephemeral fever virus) of the Rhabdoviridae family will only be answered by further physicochemical characterization and comparison.

Arbovirus infection of vertebrate and insect cell cultures, with special emphasis on Mokola, Obodhiang, and kotonkan viruses of the rabies serogroup.

Multiplication of rabies serogroup viruses, Obodhiang and kotonkan (two presumptive arboviruses), was induced in vertebrate cell cultures with Singh's A. albopictus cell cultures used as "helper cells" in cocultivation experiments. Plaque formation without prior in vitro adaptation was induced in Vero cell cultures with eight rabies serogroup viruses: in all five instances by cocultivation of either infected BHK-21 or A. albopictus cells with Vero cells under agar overlay and in three of eight instances by direct plaque assay of infected mouse brain suspensions. In cross-plaque reduction neutralization tests with cloned viruses that represented human pathogens, rabies, Duvenhage, and Mokola, on the one hand, and the presumptive arboviruses Obodhiang and kotonkan, on the other hand, Mokola virus shared common antigenic components with both the nonarboviruses and the arboviruses. Biologically, Mokola virus was different from the other two human pathogens, rabies and Duvenhage, in that it multiplied in both vertebrate and invertebrate cell cultures. Mokola virus thus appears to be the biologic and serologic bridging agent.

Plasticity of phenotypic characters of rabies-related viruses: spontaneous variation in the plaque morphology, virulence, and temperature-sensitivity characters of serially propagated Lagos bat and Mokola viruses.

Rabies-related Mokola and Lagos bat rhabdoviruses produced heterogeneous plaque populations after growth in BHK/21 cells. Three plaque clones of each virus differed in plaque morphology, pathogenicity for mice, capacity for replication at elevated temperatures of incubation, and degree of inactivation by antiserum to rabies virus. Although each type of clone was thrice clone-purified, certain clones continued to produce diverse types of plaques; further selection of plaque variants revealed continuous spontaneous alteration of several phenotypic characters. Two Mokola clones yielded subclones of widely diverse plaque morphology; nonpathogenic clone no. 1 yielded both pathogenic and nonpathogenic plaque variants. Mouse-pathogenic Lagos clone no. 3 also yielded subclones differing widely in plaque morphology and temperature sensitivity. Several subclones of Lagos clone no. 3 were either apathogenic for mice or different from the parental virus in length of incubation period in vivo or in dose-response pattern of the death curve. All subclones of Lagos and Mokola virus retained antigens that cross-reacted with antiserum to rabies virus. Attempts to select or, induce variants that did not react with rabies antiserum were unsuccessful.

Biological studies and plaquing of Mokola virus (rabies serogroup) in porcine kidney (PS) cells.

The continuous pig kidney cell line (PS) is very sensitive to the propagation of Mokola virus. No prior adaptation of the virus to the cells was necessary before the demonstration of high virus titers. Virus activity in the cells can be easily quantified in terms of cytopathic effect, titer of complement-fixing antigen in the culture fluid, and plaque formation. There was no inclusion body formation. The plaques were quite clear, measuring 1–2 mm, and were countable from the 4th day. The results of the plaque neutralization test as well as the neutralization test in baby mice showed no significant cross-reaction between Mokola virus and rabies virus.

Experimental infection of dogs and monkeys with two rabies serogroup viruses, Lagos bat and Mokola (IbAn 27377). Gross pathologic and histopathologic changes.

Dogs and monkeys were inoculated intracerebrally or intramuscularly with Lagos bat virus or Mokola virus, two viruses serologically and morphologically related to rabies virus. All animals inoculated intracerebrally died, but some animals inoculated intramuscularly survived. One monkey inoculated intramuscularly with Lagos bat virus survived with a hemiparesis. In both dogs and monkeys that died there was a nonsuppurative meningoencephalomyelitis and ganglionitis. Lesions were more extensive than those reported after infection with street rabies virus. Intracytoplasmic inclusions, morphologically indistinguishable from Negri bodies, were seen in the central nervous system of monkeys, but not dogs, that died. With fluorescent-antibody microscopy, granular aggregations of viral antigen were observed in the cytoplasm of many neurons in the central nervous system. In some animals, the retina and ciliary body of the eye had focal inflammatory changes.

Mokola virus: experimental infection and transmission studies with the shrew, a natural host.

Wild-caught shrews (Crocidura sp.), the only known wildlife host of the rabiesrelated agent Mokola virus, were given various dose levels of Mokola virus by different routes (subcutaneous, intramuscular, and oral), and then were examined for recovery of virus, presence of histopathologic lesions, and ability to transmit virus by bite to laboratory mice. Thirteen shrews, given virus by each of the routes, showed evidence of having become infected. Eleven of these became ill and yielded virus from multiple tissues, in which lesions were observed. Of the two infected shrews that remained asymptomatic, both showed histopathologic lesions and one also yielded virus, while the other was virus-negative (only brain was tested) but transmitted virus to a mouse. Four of the shrews that were virus-positive also transmitted the virus to mice. Thirty other inoculated shrews, as well as control shrews, did not yield virus and failed either to show lesions compatible with Mokola virus infection or to transmit virus.

Kotonkan, a new rhabdovirus related to Mokola virus of the rabies serogroup.

Kotonkan, a new rhabdovirus related to Mokola virus of the rabies serogroup.

A fatal human infection with Mokola virus.

A six-year-old Nigerian girl presented in hospital with symmetrical paralysis of the extremities and drowsiness which progressed to deep coma. She died 72 hours after admission. Mokola, a rabies related virus, was isolated from brain material obtained at autopsy, making her the first known case of fatal human infection with this virus. Histologically, sections of the brain showed perivascular cuffing mostly by lymphocytes, although many atypical primitive lymphoblastoid cells were also present. Sections stained with phloxine tartrazine revealed large numbers of finely granular, stippled cytoplasmic inclusion bodies in many neurons. The inclusion bodies are easily distinguishable from Negri bodies and may be a distinctive feature of infection with Mokola virus.

Mokola Virus

IbAn 27377 virus, a rabies-related agent which it is proposed to name Mokola virus, has been isolated six times in Ibadan, Nigeria. The original three strains and one other were recovered from non-nervous tissue of shrews, Crocidura sp. The remaining strains both came from children. The first child, who was admitted to University College Hospital with convulsions and later recovered, yielded Mokola virus from cerebrospinal fluid. The second child, who died of a poliomyelitis-like illness, yielded Mokola virus from brain. In a serum survey, neutralizing antibody to the virus was detected in 1 of 57 sera from cattle, 1 of 30 from goats, 1 of 78 from swine, 1 of 23 from birds, and 1 of 5 from bats (Eidolon helvum); results were negative for 29 sera from other bats, 82 sera from man, 91 from shrews, and 13 from sheep.