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Characterization of antibodies to orthopoxviruses in human sera by radioimmunoassay.

Serological surveillance of suspected orthopoxvirus infections in man is important for confirming the success of the worldwide smallpox eradication programme. An adsorption radioimmunoassay (RIA) was used to differentiate sera from patients who were naturally infected with human monkeypox or variola virus, and individuals who were immunized with vaccinia virus. The antisera were adsorbed with uninfected chicken chorioallantoic membrane (CAM) and vaccinia-infected CAM before reacting in RIA with vaccinia, monkeypox, and variola antigens. Each serum group showed characteristic patterns of residual antibody activity which made it possible to identify antibody specificities.When 45 human sera were tested by this method, 71% were identified as having vaccinia, variola, or monkeypox adsorption characteristics, while the remaining 29% could not be identified. Of the identified sera, 9 were characteristic of vaccinia, 8 of variola, and 15 of monkeypox. Six of the 15 monkeypox sera were virologically confirmed monkeypox infections, 6 were suspected monkeypox infections but were not virologically confirmed, and 3 were of unknown aetiology.The adsorption RIA provides a method of identifying serologically the poxvirus responsible for infection long after the acute phase of illness.

Animals↗

Orthopoxvirus DNA: a comparison of restriction profiles and maps.

Characteristic DNA endonuclease digest fragment electropherograms and restriction site maps permitted differentiation and genome structure analysis of 38 orthopoxviruses that included isolates of monkeypox virus from humans and animals, monkeypox white variants, variola, vaccinia, ectromelia, Tatera (gerbil) and raccoon poxviruses, and cowpox and camelpox viruses. HindIII cleavage sites mapped on the 38 virus genome DNAs plus SmaI, BglI, SacI, KpnI, XhoI, and SalI maps for variola (Harvey) and monkeypox (Copenhagen) virus DNAs were derived essentially by cross-hybridizations with monkeypox, vaccinia, and variola virus-cloned DNA restriction fragments, thus digest fragments could be assigned homologous regions on previously established genome maps. Salient of our observations, the DNA HindIII maps correlated to a high degree, but variations in middle and especially terminal DNA region cleavage sites provided a basis for discerning species, strains and variants. The extent of the inverted terminal repetitions (ITRs) for 37 DNAs were determined with HindIII, PvuI, SalI, and ClaI, plus nine more restriction enzymes for Bangladesh variola virus DNA by hybridizations with either the terminal tandemly repeated 70-bp segment or an EcoRI-PvuI near hairpin-end 75-bp segment from WR vaccinia virus. The opposite terminal regions of variola DNA were considerably asymmetrical compared to the large symmetrical ITRs of the other species examined. An apparent DNA inversion and concurrent deletion (1 kbp) with subsequent repair of DNA to original structure was suggested from right terminal region maps of four viruses chosen from a variola virus passage series in monkeys. Correlative with virus geographic distribution, two strains of monkeypox virus, each containing two variants, were differentiated by DNA profiles of isolates from smallpox-like disease (SLD) patients of the African rainforest region. The DNAs of five monkeypox viruses isolated from laboratory and zoo animals resembled most DNAs from SLD monkeypox viruses from Sierra Leone. A poxvirus from an American raccoon contained 40% DNA that did not cross-hybridize with orthopoxvirus DNA probes. The DNAs of recent isolates from a gerbil and from a camel each mapped as unique African orthopoxvirus species and differed from variola virus.

Animals↗

[Tenth anniversary of smallpox eradication: Results of epidemiological and virological surveillance and studies in the post-eradication period].

In accordance with recommendations of the Global Commission on the certification of smallpox eradication for the 10-year period after the eradication of this infection, all suspected cases of smallpox have been thoroughly checked up, and in none of them the diagnosis of smallpox has been confirmed. The study of monkeypox in humans has revealed that this zoonosis is spread over a wider area than supposed earlier and covers 7 countries of Equatorial Africa, occurring most frequently in Zaire. In about 70% of cases of monkeypox in human the disease is contracted from animals serving as natural virus carriers and in about one-third of such cases, from humans having monkeypox. The infectivity of humans with monkeypox for persons having close contacts with them is somewhat lower (12.3%) than in smallpox when this characteristic varies from 37% to 88%. Monkeypox in humans may take an asymptomatic course. Some species of tropical squirrels serve as natural virus carriers. These investigations have also resulted in essential corrections being made in understanding the ecology of cowpox virus, another orthopoxvirus pathogenic for man. At least 5 species of rodents have proved to be of interest as natural carriers of cowpox virus.

Africa↗

[Human monkey pox: its clinico-epidemiological characteristics].

During the course of the smallpox eradication programme, a new eruptive disease clinically resembling smallpox was discovered in Zaire. The disease, which was named monkeypox after the virus, is a zoonosis occurring sporadically in countries of western and central Africa with tropical rain forest. The studies carried out in Zaire from 1980 through 1985 showed that monkeypox affects mainly children in relatively small remote villages whose population has traditionally frequent contacts with wild animals. Apart from the wildlife, the virus can be transmitted from man to man, but among other sources of infection sick persons did not exceed 20%. Presumed human transmission has occurred in 38 out of 61 outbreaks of human monkeypox and only once reached the third and once the fourth generation; the transmission in all affected villages under observation has extinguished itself. Considering the sporadic and relatively rare occurrence of the disease and expected complications following the immunization with vaccinia which protects from monkeypox, introduction of mass vaccination in the areas at risk is hardly justified at present.

Africa, Central↗

Poxviruses isolated from clinically ill and asymptomatically infected monkeys and a chimpanzee.

Poxviruses were isolated from the kidneys of an outwardly healthy chimpanzee trapped in an area of the Democratic Republic of the Congo where a case of monkeypox had recently occurred in man, from the kidneys of clinically healthy cynomolgus monkeys in a colony in the Netherlands, and from monkeys suffering from monkeypox during outbreaks in colonies in the USA. It was established that two of the three viruses isolated from animals asymptomatically infected-namely, strain Chimp-9 from the chimpanzee and strain 64-7255 from the cynomolgus monkeys-although similar to one another differed markedly from the classical Copenhagen strain of monkeypox virus. These two viruses were characterized by the formation of small, monomorphic, well-defined pocks without haemorrhages on infected chick embryo chorioallantoic membrane, by the small plaques of the proliferative type that they produced in cell cultures, by the absence of reactions when they were applied to scarified rabbit skin and the absence of marked necrosis when they were inoculated intradermally into rabbits, by their intensive replication in pig embryo kidney cell cultures, and by a number of other features. It is therefore possible to describe both the viruses as being very close to the variola virus. The Chimp-9 and 64-7255 strains differed from the variola virus only in their greater pathogenicity for white mice after intracerebral inoculation. The other virus isolated from a symptomless cynomolgus monkey-strain 64-9411-resembled the two viruses isolated from monkeys suffering from monkeypox and did not differ from the Copenhagen strain.

Animals↗

Adjuvant-enhanced antibody responses to recombinant proteins correlates with protection of mice and monkeys to orthopoxvirus challenges.

Recombinant proteins are being evaluated as smallpox and monkeypox vaccines because of their perceived safety compared to live vaccinia virus. Previously, we demonstrated that three or more injections of a Ribi-type adjuvant with a combination of three proteins from the outer membranes of intracellular (L1 protein) and extracellular (A33 and B5 proteins) forms of vaccinia virus protected mice against a lethal intranasal challenge with vaccinia virus. Here, we compared several adjuvants and found that QS-21 and to a lesser extent alum+CpG oligodeoxynucleotides accelerated and enhanced neutralizing antibody responses to a mixture of L1 and A33 proteins, provided the highest ratio of IgG2a to IgG1 isotype response, and protected mice against disease and death after only two immunizations 3 weeks apart. In addition, monkeys immunized with recombinant vaccinia virus proteins and QS-21 developed neutralizing antibody to monkeypox virus and had reduced virus load, skin lesions, and morbidity compared to the non-immunized group following monkeypox virus challenge.

Adjuvants, Immunologic↗

Orthopoxvirus strains defective in surface antigen induction.

Various strains of vaccinia, variola, whitepox, monkeypox and cowpox viruses were examined for their capacity to induce a specific early antigen detectable on the surface of infected cells. The Elstree strain of vaccinia, two strains of variola minor and white variants of cowpox and monkeypox viruses lacked the capacity to induce the antigen. Variation of the parent cowpox and monkeypox viruses to white variants was always accompanied by the loss of the antigen-inducing capacity.

Animals↗

[The development and use of an immunoenzyme test system for detecting and the species identification of the monkey pox virus].

An enzyme immunoassay (EIA) system for the species-specific diagnosis of monkeypox, based on the use of monoclonal antibodies (McAb) to monkeypox virus, has been developed. Immunoglobulins, isolated from McAb-containing cultural and immune ascitic fluids, have been conjugated with horse-radish peroxidase and used as detector antibodies. For immunosorption, rabbit polyclonal antibodies to the vaccine virus have been used. The specificity and sensitivity of the EIA system thus obtained have been tested on animals and humans having monkeypox and confirmed by traditional diagnostic methods (the isolation of the virus on chick embryo chorioallantoic membranes and in cell culture).

Animals↗

[Monkey pox virus infection in humans in the Central African Republic].

A human monkeypox outbreak is reported which occurred in January 1984 in the extreme south-west areas of the Central African Republic. Six persons were found to be affected in a Pygmy camp with an estimated population of 50 residents. In the two affected families, out of 11 members, only unvaccinated children and a 22 year old unvaccinated woman contracted the disease. The disease was of moderate severity in two patients and very mild in the other four. The clinical diagnosis was confirmed by virus isolation from skin lesions of 4 patients and by sero-immunologic tests in all of them. The clinically apparent monkeypox case reported in the Central African Republic in 1983, the presently described outbreak, as well as information on the disease obtained from Pygmies and missionary paramedical staff who are in frequent contact with them, suggest that monkeypox is enzootic in the tropical rain forest in the south-west areas of the Central African Republic.

Central African Republic↗

[Data from a serological survey of the population of the Republic of Congo for the presence of antibodies to orthopoxviruses. II. The species identification of the antibodies by using a solid-phase variant of immunoenzyme method].

To differentiate antibodies to monkeypox and vaccinia viruses, the solid-phase ELISA with preliminary adsorption of sera with vaccinia virus was used. The identification of antibodies in 99 serum samples obtained in the Republic of Congo from children without vaccination scars was carried out by means of this assay. No antibodies to monkeypox virus were revealed. In 62% of cases the presence of antibodies was due to vaccinia virus. In the sera of 32% of children under examination antibodies differing from those to vaccinia and monkeypox viruses were revealed. To find out the origin of these antibodies, further seroepidemiological studies are necessary.

Adolescent↗

Zoonotic poxvirus infections in humans.

PURPOSE OF REVIEW: The 2003 USA monkeypox epidemic caused by imported African rodents, newly emergent poxvirus zoonoses in Brazil and the possible use of variola virus for biological warfare has led to renewed interest in poxviruses and anti-poxviral therapies. Increasing foreign travel and importation of exotic animal species increases the likelihood of poxvirus infections occurring outside their usual geographical range and diagnostic delay has important implications. The present review provides an overview of these rare zoonoses. RECENT FINDINGS: Three genera of Poxviridae are known to cause human zoonoses: orthopoxviruses, parapoxviruses and yatapoxvirus. Most cases are occupational, sporadic and have few cutaneous lesions with low morbidity. The exception is monkeypox, similar to smallpox, with significant morbidity and childhood mortality. Molecular characterization using polymerase chain reaction (PCR) amplification and other methods provides accurate phylogenetic identification and suggests that a cowpox-like virus is the probable ancestor of variola and other zoonotic poxviruses. DNA genomic sequencing of the Brazilian Cantagalo and Araçatuba viruses shows a close relationship to vaccinia virus. Poxviruses have potential in cancer immunotherapy and their ability to evade host-cell immune responses may provide a basis for new antipoxvirus therapies. Other agents, particularly nucleoside phosphonates such as cidofovir, show therapeutic action against poxviruses. SUMMARY: Human zoonotic poxvirus infections are rare but increasingly encountered outside their usual geographical range. The 2003 USA monkeypox outbreak emphasizes the importance of early accurate diagnosis, particularly because increasing numbers of immunosuppressed individuals increases the potential for severe or fatal infections. PCR methodology enables accurate phylogenetic typing and has identified new diseases, but rapid, reliable methods must be made available for clinicians. More research into therapeutic agents for the prevention and treatment of poxvirus infections is required.

Animals↗

DNA sequence variation as a clue to the phylogenesis of orthopoxviruses.

We have sequenced DNA equivalent to the E5R ORF of Copenhagen vaccinia virus from an additional strain of vaccinia and from cowpox (three strains), camelpox (two strains), taterapox and ectromelia viruses. None of these showed the disruptions previously reported in the equivalent region of monkeypox virus. We also constructed a viable recombinant of vaccinia virus strain Dairen in which the E5R sequence was disrupted by a 436 bp deletion and substitution of the E. coli gpt gene. Quantitative analysis of the sequences, including available sequences from monkeypox, variola and vaccinia viruses revealed four main groupings, namely cowpox, ectromelia, monkeypox and a cluster which includes variola, camelpox, taterapox and vaccinia viruses. It was noted that, at over 75 % of the positions which differentiated species. all species but one had a common nucleotide. Although the analysis covers one single gene only, the results accord with what is known of the biology of the viruses.

Base Sequence↗

The detection of subtle differences between different orthopoxvirus genomes by heteroduplex analysis.

Corresponding DNA fragments from variola (Harvey) and monkeypox (Denmark) viruses which had been cloned into different plasmid vectors were subjected to heteroduplex analysis. Characteristic deletion loops corresponding to differences between the cloning vectors served as internal markers to identify and to orientate the heteroduplexed molecules. Partial denaturation of the resulting heteroduplexes was used as a primary screen to locate regions of heterogeneity between the poxvirus inserts. The denaturation threshold for homoduplexes was consistently higher than that for heteroduplexes. However, significant sequence divergence between corresponding fragments was indicated by larger than usual differences in thresholds between corresponding homo- and heteroduplexes. Denaturation bubbles of 0.1-0.5 kb were detected and hence small regions of heterogeneity between the genomes (180 kb) of variola and monkeypox viruses were localised. This procedure has a general application in comparative studies on large, complex but closely related DNA molecules.

Base Sequence↗

Conservation and variation in Orthopoxvirus genome structure.

Orthopoxvirus DNA from representative strains of rabbitpox, vaccinia, monkeypox, variola, cowpox and ectromelia viruses was analysed by cleavage with restriction endonucleases HindIII, XhoI or SmaI. Genome mol. wt. vary from about 120 x 10(6) for rabbitpox to about 145 x 10(6) for cowpox. Physical maps of cleavage sites are similar and characteristic for strains of the same Orthopoxvirus type. The distribution of HindIII sites suggests that an internal region of mol. wt. about 30 x 10(6) is highly conserved between Orthopoxvirus genomes although some type-specific differences occur within this region, especially with strains of ectromelia virus. Conservation of internal sequences is less marked following analysis with XhoI although cleavages within this central region of particular genomes appear to represent a subset of preferred sites. Endonuclease SmaI cleaves exceptionally infrequently and distinguishes variola, monkeypox, vaccinia, cowpox or ectromelia viruses. Type specific differences result largely from extensive, near terminal variations in length and sequence. Representative Orthopoxvirus genomes have rapidly renaturing terminal restriction fragments confirming the presence of near terminal, covalent cross-links. Terminal restriction fragments from the same or different genomes generally cross hybridize indicating the presence of near terminal repetitions of mol. wt. up to 6 x 10(6) and which share at least a subset of common sequences. Variola strains however, appear to lack such sequences from one specific terminus which maps shorter than that of related viruses.

Base Sequence↗

Monkeypoxvirus infections.

During and after the smallpox eradication campaign, human cases of monkeypox appeared in West and Central Africa, as isolated cases or as small epidemics. Since inter-human transmission has never or only very exceptionally been documented, monkeypox does not represent a serious threat to humans. The virus reservoir is among tree squirrels living in the tropical rain forests of Africa and humans are infected by hunting, killing and skinning these animals. However, the modernization of society lessens human contact with the virus reservoir. Since the eradication of smallpox, stocks of variola virus have been maintained; whether these stocks should now be destroyed is a political question, which is seriously compromised by mistrust between countries.

Animals↗

Human poxvirus disease after smallpox eradication.

A 5-year-old boy living in a small camp in the rural Ivory Coast had a disease resembling smallpox. This occurred 4 years after smallpox had been eradicated from the Ivory Coast and 1.5 years after the last case of smallpox was detected in West and Central Africa. Clinical, serological, and epidemiological evidence indicated this disease was probably monkeypox, a poxvirus of the variola/vaccina subgroup. A serologic survey of poxvirus antibodies in the wild animal population detected neutralizing antibodies in rodents, larger mammals, primates, and birds. The laboratory and ecological characteristics of poxviruses require further elucidation, especially those which have been found in animals near human monkeypox cases.

Adolescent↗

[Biohazards due to Orthopoxvirus: should we re-vaccinate against smallpox?].

Although the WHO declared global smallpox eradication in 1980, the Orthopoxvirus remains a source of concern for several reasons. Firstly, stocks of the smallpox virus have been preserved for experimental use (at least officially in the USA and Russia) so that an escaped isolate could lead to reemergence and spread of the disease worldwide. Secondly discontinuation of smallpox vaccination programs has led to dwindling acquired immunity in the world population thus raising the risk of epidemic extension of several Orthopoxvirus zoonoses (e.g., monkeypox). Thirdly stocks of camelpox virus which is very similar to Smallpox virus and was intended for biological warfare were discovered during the Gulf War in 1991 and pose a potentially serious threat. Finally official stocks of Smallpox virus could be stolen and used by bioterrorists. Thus reemergence of Orthopoxvirus including smallpox, monkeypox, cowpox, and camelpox is a real danger and contingency planning is needed to define prophylactic and therapeutic strategies to prevent and/or stop an epidemics. Adverse effects from earlier smallpox vaccine (vaccinia) in healthy people or immunocompromised people (congenital or acquired as in HIV infected patients) are absolute contraindications to smallpox vaccination at this time. Further research is needed to develop new vaccines (e.g., attenuated isolates of vaccinia) and effective treatment. This is the only valid reasons for postponing planned destruction of remaining Smallpox virus stocks.

Biological Warfare↗

[Contagiousness of monkey pox for humans: results of an investigation of 2 outbreaks of the infection in Zaire].

The results of the investigation of two outbreaks of group monkeypox infection among humans (altogether 8 cases) in the zone of Bumba, Equatorial Province, Zaire, are presented. The primary source of infection in both outbreaks was not established, the outbreaks were supposedly caused by sick wild animals. Almost all persons affected by this infection were children aged 7 months to 7 years, never vaccinated against smallpox; the only exception was a 29-year old female patient, formerly vaccinated and revaccinated against smallpox. During one of the outbreaks the laboratory-confirmed transmission of infection from man to man was established in two generations. During the other outbreak there were grounds to suspect the transmission of infection in three generations, though the possibility of contacting infection from animals could not be completely ruled out. The existence of the inapparent form of monkeypox in humans was revealed.

Adult↗