Isolation of a virus responsible for an outbreak of acute haemorrhagic conjunctivitis in Morocco

Methylene Blue Inhibits Acute Hemorrhagic Conjunctivitis Virus Production and Induction of Caspase-3 Mediated Human Corneal Cell Cytopathy

Background

Acute hemorrhagic conjunctivitis (AHC) is a highly contagious eye disease caused by enterovirus type 70 (E70) and Coxsackievirus A24 variant (CA24v) with no clinically approved treatment. The antiviral activity of methylene blue (MB; a WHO essential medicine) against AHC viruses was investigated using human corneal epithelial cells (HCEC).

Methods

Time and concentration-dependent MB accumulation by HCEC was determined colorimetrically and MB inhibition of virus production of 5 E70 and 3 CA24v AHC epidemic isolates in HCEC was determined by micro-plaque assay. AHC virus cytopathy inhibition by MB was detected by reductions in virus-induced caspase-3 activity and polymeric DNA fragments.

Results

MB uptake by HCEC was rapid and concentration dependent. MB inhibition of E70 and CA24v production was concentration dependent. AHC virus yields were significantly lower (50 to >10,000 fold) in HCEC pre-treated with 0.25–1% MB than in placebo controls (p’s ≤ 0.01). MB pre-treatment significantly inhibited virus-induced caspase-3 activation and DNA fragmentation (p’s<0.01). Virus-infected cells accumulate oxidized MB and MB application up to 6 h after infection inhibited virus production and virus-induced HCEC cytopathy.

Conclusion

The results suggest MB treatment prior to and shortly after infection can inhibit AHC virus production and caspase-mediated HCEC cytopathy. The results support the therapeutic potential of ophthalmic solutions containing MB against AHC virus infection during epidemics.

[Enteroviruses responsible for acute hemorrhagic conjunctivitis]

Acute hemorrhagic conjunctivitis (AHC) is an epidemic form of highly contagious conjunctivitis, characterized by conjunctival hemorrhages. The first AHC outbreak was described in 1969 in Ghana, West Africa, and was called Apollo disease, from the Apollo landing on the moon. This outbreak was caused by Enterovirus 70 (EV70) together with a Coxsackievirus A24 (CVA24v) variant, which are the major etiological agents involved in AHC outbreaks worldwide. AHC is known to be directly transmitted by close person-to-person contact or indirectly through soiled ophthalmological materials or unsafe recreational water. Recently, a possible airborne virus spread was suggested which could explain the high transmission rate of the disease. In the absence of a specific antiviral therapy, a rapid diagnosis of the causative agent is required to distinguish AHC due to enteroviruses from other ocular infectious diseases, for there are active drugs, or to quickly implement proper public health measures to limit the extension of the outbreak. However, virus identification remains difficult and time-consuming. Moreover, virological diagnosis is difficult to implement in developing countries where AHC has recently become a major problem for public health.

Two outbreaks of acute hemorrhagic conjunctivitis in Africa due to genotype III coxsackievirus A24 variant

Reported here are two outbreaks of acute hemorrhagic conjunctivitis that occurred in the Democratic Republic of the Congo and in Morocco in the summers of 2003 and 2004, respectively, with a large impact on public health. Virus was isolated from the conjunctival swabs of 30 Congolese and 20 Moroccan patients. Enterovirus-specific cytopathic effect was observed in all samples. None of the strains could be typed using a conventional neutralization assay with the Melnick intersecting pools; however, by sequencing the VP1 region, the viruses could be identified as coxsackie A24 variants. Phylogenetic analysis of the 3C protease region revealed that these strains were closely related to each other as well as to genotype III isolates detected in Korea in 2002, thus proving their worldwide spread. This is the first report of an epidemic of acute hemorrhagic conjunctivitis due to a coxsackievirus A24 variant in Africa since 1987 and the first ever from Morocco.

Molecular evolution of the major capsid protein VP1 of enterovirus 70

Nucleotide sequences of the genome RNA encoding capsid protein VP1 (918 nucleotides) of 18 enterovirus 70 (EV70) isolates collected from various parts of the world in 1971 to 1981 were determined, and nucleotide substitutions among them were studied. The genetic distances between isolates were calculated by the pairwise comparison of nucleotide difference. Regression analysis of the genetic distances against time of isolation of the strains showed that the synonymous substitution rate was very high at 21.53 x 10(-3) substitution per nucleotide per year, while the nonsynonymous rate was extremely low at 0.32 x 10(-3) substitution per nucleotide per year. The rate estimated by the average value of synonymous and nonsynonymous substitutions (W.-H. Li, C.-C. Wu, and C.-C. Luo, Mol. Biol. Evol. 2:150-174, 1985) was 5.00 x 10(-3) substitution per nucleotide per year. Taking the average value of synonymous and nonsynonymous substitutions as genetic distances between isolates, the phylogenetic tree was inferred by the unweighted pairwise grouping method of arithmetic average and by the neighbor-joining method. The tree indicated that the virus had evolved from one focal place, and the time of emergence was estimated to be August 1967 +/- 15 months, 2 years before first recognition of the pandemic of acute hemorrhagic conjunctivitis. By superimposing every nucleotide substitution on the branches of the phylogenetic tree, we analyzed nucleotide substitution patterns of EV70 genome RNA. In synonymous substitutions, the proportion of transitions, i.e., C<==>U and G<==>A, was found to be extremely frequent in comparison with that reported on other viruses or pseudogenes. In addition, parallel substitutions (independent substitutions at the same nucleotide position on different branches, i.e., different isolates, of the tree) were frequently found in both synonymous and nonsynonymous substitutions. These frequent parallel substitutions and the low nonsynonymous substitution rate despite the very high synonymous substitution rate described above imply a strong restriction on nonsynonymous substitution sites of VP1, probably due to the requirement for maintaining the rigid icosahedral conformation of the virus.

[Acute hemorrhagic conjunctivitis, in Cuiabá, Mato Grosso, Brazil 1983]

Foi feita investigação de natureza etiológica clínica e laboratorial durante uma epidemia de conjuntivite hemorrágica aguda (CHA), ocorrida em Cuiabá, MT durante os meses de dezembro de 1982 e fevereiro de 1983; atendidos 68 pacientes e colhidos espécimes da conjuntiva, orofaringe e soro. Em 28 pares de soros foram realizados testes de neutralização em tubos de cultura de tecidos para o enterovirus 70 (EV 70) e fixaço do complemento para os adenovirus. Os resultados revelaram conversão sorológica de 89,3% (25 pares de soro) para o EV 70. A Secretaria de Saúde do Estado do Mato Grosso estima que aproximadamente 70% da população tenha sido atingida durante o surto. Não foram observadas evidências de comprometimento neurológico em pacientes de conjuntivite, durante ou logo após o surto.

Detection of enterovirus 70 with monoclonal antibodies

To improve the ability to identify enterovirus-70 (EV-70) from patients with acute hemorrhagic conjunctivitis, we developed four monoclonal antibodies (MAbs) to EV-70. We reacted the four MAbs against nine previously characterized strains of EV-70 and heterologous viruses by virus neutralization, indirect immunofluorescence, and enzyme-linked immunosorbent assay (ELISA). Two of the MAbs neutralized all nine strains of EV-70 and none of the other enterovirus types tested. Two of the MAbs gave a positive reaction with all nine strains by indirect immunofluorescence, and three reacted with all nine strains by ELISA. None of the MAbs gave a positive reaction with heterologous viruses, including those associated with eye disease, by indirect immunofluorescence or ELISA. The two neutralizing MAbs failed to give a positive reaction with some of the strains of EV-70 by indirect immunofluorescence and ELISA, yet they neutralized these viruses. By ELISA with a polyclonal serum as capture antibody and a mixture of MAbs as detector antibody, we were able to detect from 10(2.2) to 10(5.8) 50% tissue culture infective doses of virus and to type lyophilized isolates of EV-70 sent from Taiwan from which we could not recover infectious virus. By choosing the appropriate MAb, or mixture of MAbs, we could construct a test which had the type specificity and strain sensitivity needed to type isolates of EV-70.

Evolution of enterovirus type 70: oligonucleotide mapping analysis of RNA genome

Different isolates of enterovirus type 70 (EV70) taken between 1971 and 1981 were studied by molecular biological methods to elucidate their evolutional change. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that only a few isolates had a slight alteration in mobility in some viral proteins. On the contrary, oligonucleotide mapping of virion RNA could clearly delineate the molecular changes among isolates. The number of base changes of isolates became greater as the years elapsed. In addition, the number of base changes among recent isolates from different areas of the world was much greater than those among early isolates. Thus, when the isolates were arranged three-dimensionally according to the number of base changes between each other, the constellation of the strains gave rise to a conical shape. The central axis of the figure was the time of isolation of the strains. The early isolates clustered near the top of the conical figure and the recent isolates tended to disperse divergently at the bottom. The figure indicated that all EV70 strains were derived from a common ancestor, and its top would be the time of emergence of the original strain. It was estimated to be around 1966, 3 years prior to the first epidemic in Accra, Ghana. From the results, it was presumed that EV70 would have emerged at a single focus in Africa as a novel human virus. After having circulated there for a few years, the virus spread to the other parts of the world. Based on the difference in the oligonucleotide spots between the recent isolates and early isolates, the base changes of EV70 that occurred during 10 years was estimated to be 320, about 4% (0.4% a year on the average) of the bases of the total RNA genome.

Oligonucleotide fingerprint analysis of enterovirus 70 isolates from the 1980 to 1981 pandemic of acute hemorrhagic conjunctivitis: evidence for a close genetic relationship among Asian and American strains

Enterovirus 70 isolates obtained in Asia and the Americas between 1980 and 1981 from cases of acute hemorrhagic conjunctivitis were found to be very closely related by RNase T1 oligonucleotide fingerprinting. Two closely related isolates from the first acute hemorrhagic conjunctivitis epidemic (1969 to 1972) differed by many oligonucleotides from the 1980 to 1981 pandemic strains. The strong similarities of oligonucleotide patterns of isolates from the same epidemic but from distant regions of the world suggest that the genome of enterovirus 70 tends to be conserved during natural infection, a possible consequence of the transient nature of the disease.