Seroepidemiologic studies of acute hemorrhagic conjunctivitis virus (enterovirus type 70) in West Africa. III. Studies with animal sera from Ghana and Senegal

Genetic and phenotypic characterization of recently discovered enterovirus D type 111

Members of the species Enterovirus D (EV-D) remain poorly studied. The two first EV-D types (EV-D68 and EV-D70) have regularly caused outbreaks in humans since their discovery five decades ago but have been neglected until the recent occurrence of severe respiratory diseases due to EV-D68. The three other known EV-D types (EV-D94, EV-D111 and EV-D120) were discovered in the 2000s-2010s in Africa and have never been observed elsewhere. One strain of EV-D111 and all known EV-D120s were detected in stool samples of wild non-human primates, suggesting that these viruses could be zoonotic viruses. To date, EV-D111s are only known through partial genetic sequences of the few strains that have been identified so far. In an attempt to bring new pieces to the puzzle, we genetically characterized four EV-D111 strains (among the seven that have been reported until now). We observed that the EV-D111 strains from human samples and the unique simian EV-D111 strain were not phylogenetically distinct, thus suggesting a recent zoonotic transmission. We also discovered evidences of probable intertypic genetic recombination events between EV-D111s and EV-D94s. As recombination can only happen in co-infected cells, this suggests that EV-D94s and EV-D111s share common replication sites in the infected hosts. These sites could be located in the gut since the phenotypic analysis we performed showed that, contrary to EV-D68s and like EV-D94s, EV-D111s are resistant to acid pHs. We also found that EV-D111s induce strong cytopathic effects on L20B cells, a cell line routinely used to specifically detect polioviruses. An active circulation of EV-D111s among humans could then induce a high number of false-positive detection of polioviruses, which could be particularly problematic in Central Africa, where EV-D111 circulates and which is a key region for poliovirus eradication.

Co-circulation of enteroviruses between apes and humans

A total of 139 stool samples from wild chimpanzees, gorillas and bonobos in Cameroon and Democratic Republic of Congo (DRC) were screened for enteroviruses (EVs) by reverse transcription PCR. Enterovirus RNA was detected in 10 % of samples, comprising eight from 58 sampled chimpanzees (13.8 %), one from 40 bonobos (2.5 %) and five from 40 gorillas (12.2 %). Three viruses isolated from chimpanzees grouped with human isolate EV-A89 and four (four chimpanzees, one gorilla) represented a newly identified type, EV-A119. These species A virus types overlapped with those circulating in human populations in the same area. The remaining six strains comprised a new species D type, EV-D120, infecting one chimpanzee and four gorillas, and a single EV variant infecting a bonobo that was remarkably divergent from other EVs and potentially constitutes a new enterovirus species. The study demonstrates both the circulation of genetically divergent EV variants in apes and monkeys as well as those shared with local human populations.

Detection and genetic characterization of enteroviruses circulating among wild populations of chimpanzees in Cameroon: relationship with human and simian enteroviruses

Enteroviruses (EVs), members of the family Picornaviridae, are a genetically and antigenically diverse range of viruses causing acute infections in humans and several Old World monkey (OWM) species. Despite their known wide distribution in primates, nothing is currently known about the occurrence, frequency, and genetic diversity of enteroviruses infecting apes. To investigate this, 27 chimpanzee and 27 gorilla fecal samples collected from undisturbed jungle areas with minimal human contact in Cameroon were screened for EVs. Four chimpanzee samples were positive, but none of the gorilla samples were positive. Genetic characterization of the VP1, VP4, and partial VP2 genes, the 5' untranslated region, and partial 3Dpol sequences enabled chimpanzee-derived EVs to be identified as (i) the species A type, EV76, (ii) a new species D type assigned as EV111, along with a human isolate from the Democratic Republic of Congo previously described by the International Committee on the Taxonomy of Viruses, and (iii) a new species B type (assigned as EV110) most closely related to, although a distinct type from, the SA5 isolate recovered from a vervet monkey. The identification of EVs infecting chimpanzees related to those circulating in human and OWM populations provides evidence for cross-species transmission of EVs between primates. However, the direction of transfer and the existence of primate sources of zoonotic enterovirus infections in humans require further investigation of population exposure and more extensive characterization of EVs circulating in wild ape populations.

Evolution of newly described enteroviruses

Several new enterovirus serotypes and a new human rhinovirus species have been characterized in the Enterovirus genus recently, raising a question about the origin of the new viruses. In this article we attempt to outline the general patterns of enterovirus evolution, ultimately leading to the emergence of new serotypes or species. Different evolutionary and epidemiological patterns can be deduced between different enterovirus species, between entero- and rhino-viruses and between different serotypes within a species. This article presents a hypothesis that the divergent evolution leading to a new serotype is likely to involve adaptation to a new ecological niche either within a single host species or due to interspecies transmission. By contrast, evolution within a serotype appears to occur primarily by genetic drift.

Animal serum factor(s) causing adverse effects on RIAs of human enterovirus IgM

The effects of animal sera used at various concentrations in dilution buffers for radioimmunoassays (RIAs) of human enterovirus-IgM were studied. The origin of the sera had no impact on the titres, but adverse effects on virus-specificity tests were noted when sera from some species were used. In attempts to block the binding of 35S-labelled virus by adding unlabelled virus, sera from cow, horse and lamb and from swine and man could usually not be used; instead of a blocking effect, an increase in bound labelled virus was noted in most cases. When fetal or newborn calf serum or sera from chicken were used, this phenomenon did not occur. The factor(s) causing the enhancement of virus binding could not be identified, but it was evident that it was not present in all sera from the same species and it was very probable that immunoglobulins were not involved.

Management and prevention of ocular viral and chlamydial infections

A majority of cases of preventable and/or curable ocular morbidity and blindness are caused by ocular infections. They may account for 70 to 90% of all ocular morbidity seen by family doctors, general practitioners, health centers, and local ophthalmologists in both developed and developing countries. Unfortunately, most health authorities and doctors, including ophthalmologists, consider these diseases to be of little or no importance because they are not fully aware of the high prevalence of these infections and the blinding sequelae which may occur following incorrect diagnosis and treatment. Also, they are not aware of the social and economic impact of these infections in the absence of proper management and implementation of preventive measures. In this review, we examine present knowledge of chlamydial and common viral ocular infections. We discuss the problems of diagnosis, management, and prevention and propose solutions relevant to developed and developing countries.

Evolution of enterovirus 70 in nature: all isolates were recently derived from a common ancestor

The data of large RNase T1-resistant oligonucleotide mapping of enterovirus 70 (EV 70) previously reported (Takeda et al., Virology 134, 375-388, 1984) were subjected to further genetical analysis to estimate the evolutionary rate of genome RNA of EV 70 and to clarify the phylogenetic relationship among isolates. A proportion of common spots between strains decreased as the year elapsed and eventually, only seven spots were common to all the 16 isolates tested, indicating that the substitution is scattered throughout the genome. On the other hand, some specific sets of spots were conserved among geographically or epidemiologically related strains. Base sequence variation of the isolates was deduced according to Aaronson et al. (Nucleic Acids Res. 10, 237-246, 1982) from pariwise comparison of the common spots and used as a genetic distance between them. The base substitution rate of virus genome was estimated by regression analysis of the genetic distance of the isolates against the sampling time. A fairly constant and rapid rate was obtained; it was 1.83 X 10(-3)/base/year. Based on the substitution rate, genetic distance and sampling time of the strains, the phylogenetic tree of EV 70 was constructed using Unweighted Pair Group Method Using Arithmetic Averages (UPGMA) (Nei, Molecular Population Genetics and Evolution, North Holland, Amsterdam, 1975). The tree supports the previous hypothesis that evolution of EV 70 started from a single common ancestor. The time of its emergence was estimated to be 1967 +/- 15 months. The virus branched into many strains early during the first pandemic and has evolved in a divergent fashion, yielding genetically polymorphic viruses in the world.

Quantitation of enterovirus 70 antibody by microneutralization test and comparison with standard neutralization, hemagglutination inhibition, and complement fixation tests with different virus strains

We describe here a microneutralization procedure for conveniently testing large numbers of specimens for antibodies to enterovirus 70. The test utilized human rhabdomyosarcoma cells and was read by staining with crystal violet after 4 days of incubation. The test compares well with other serological assays, being more sensitive than the standard tube neutralization test and the complement fixation test, but less sensitive than the hemagglutination inhibition test. However, the hemagglutination inhibition test required concentrated, partially purified virus as antigen, as did the complement fixation test, and was difficult to read, so that its greater sensitivity may not be of practical significance. By all four test procedures, a recent isolate of enterovirus 70 was a more sensitive antigen than the prototype strain, as shown by greater geometric mean titers in sera of patients from various epidemics.