Pulmonary manifestations of other agents: brucella, Q fever, tularemia and smallpox

Brucella, Q fever, tularemia, and smallpox are all rare infections in the United States but are potential agents of biologic terrorism. The pulmonary manifestations of these infections range from uncommon (brucella and smallpox) to expected (Q fever and tularemia). and all have clinical and radiologic presentations that can be confused with other, more endemic,diseases. Once the release of these agents has been determined, the diagnosis of presenting patients will be straightforward. The onus is on the clinician,however, to be able to recognize the first few, unexpected cases, because early identification will be paramount in helping curb the effect of the outbreak.

Variola virus immune evasion proteins

Variola virus, the causative agent of smallpox, encodes approximately 200 proteins. Over 80 of these proteins are located in the terminal regions of the genome, where proteins associated with host immune evasion are encoded. To date, only two variola proteins have been characterized. Both are located in the terminal regions and demonstrate immunoregulatory functions. One protein, the smallpox inhibitor of complement enzymes (SPICE), is homologous to a vaccinia virus virulence factor, the vaccinia virus complement-control protein (VCP), which has been found experimentally to be expressed early in the course of vaccinia infection. Both SPICE and VCP are similar in structure and function to the family of mammalian complement regulatory proteins, which function to prevent inadvertent injury to adjacent cells and tissues during complement activation. The second variola protein is the variola virus high-affinity secreted chemokine-binding protein type II (CKBP-II, CBP-II, vCCI), which binds CC-chemokine receptors. The vaccinia homologue of CKBP-II is secreted both early and late in infection. CKBP-II proteins are highly conserved among orthopoxviruses, sharing approximately 85% homology, but are absent in eukaryotes. This characteristic sets it apart from other known virulence factors in orthopoxviruses, which share sequence homology with known mammalian immune regulatory gene products. Future studies of additional variola proteins may help illuminate factors associated with its virulence, pathogenesis and strict human tropism. In addition, these studies may also assist in the development of targeted therapies for the treatment of both smallpox and human immune-related diseases.

Analysis of the complete genome of smallpox variola major virus strain Bangladesh-1975

We analyzed the 186,102 base pairs (bp) that constitute the entire DNA genome of a highly virulent variola virus isolated from Bangladesh in 1975. The linear, double-stranded molecule has relatively small (725 bp) inverted terminal repeat (ITR) sequences containing three 69-bp direct repeat elements, a 54-bp partial repeat element, and a 105-base telomeric end-loop that can be maximally base-paired to contain 17 mismatches. Proximal to the right-end ITR sequences are another seven 69-bp elements and a 53- and a 27-bp partial element. Sequence analysis showed 187 closely spaced open reading frames specifying putative major proteins containing > or = 65 amino acids. Most of the virus proteins correspond to proteins in current databases, including 150 proteins that have > 90% identity to major gene products encoded by vaccinia virus, the smallpox vaccine. Variola virus has a group of proteins that are truncated compared with vaccinia virus counterparts and a smaller group of proteins that are elongated. The terminal regions encode several novel proteins and variants of other poxvirus proteins that potentially augment variola virus transmissibility and virulence for its only natural host, humans.

The virology of variola minor. Correlation of laboratory tests with the geographic distribution and human virulence of variola isolates

Several groups of variola isolates were compared in DNA structure, and by four independent biologic markers. Isolates of variola minor from Europe and South America (alastrim virus) could be distinguished from African isolates of variola minor by DNA structure and by two of the four biologic markers. Taken as a group, the properties of African isolates, in general, differed from those of variola major, but this difference was confined to properties which depended (in the laboratory) on the recent history of the virus concerned. The suggestion made previously that there was an "intermediate" or "African" variety of variola virus is discounted. Laboratory tests did not distinguish any individual African isolate from variola major virus. It is concluded that a virus which may be called "alastrim" represents a "fixed" variant of variola virus, whose distribution is consistent with the dramatic spread of variola minor through the Americas and Europe in the early part of this century, and that variola minor in Africa in recent years was due to variola virus which was not alastrim and which laboratory evidence fails to identify as an entity distinguishable from variola major virus.

A successful eradication campaign. Global eradication of smallpox

Smallpox was the first important disease to be eradicated; it was the success of the Smallpox Eradication Programme that inspired this conference. Several biological reasons favored the eradication of smallpox, the most important of which were probably that recurrent infectivity did not occur, that there was no animal reservoir, and that an effective stable vaccine was available. The importance of smallpox as a disease that travelers might import into countries free of smallpox provided a powerful stimulus for its global eradication. This paper highlights some of the problems associated with the eradication of smallpox in two countries where eradication was difficult, India and Ethiopia, and the measures adopted to overcome the problems. The paper also stresses the importance of the development of methods for the certification of smallpox eradication from countries, from regions, and finally from the whole world. It is noted that close links between field work and research were important throughout the eradication campaign.

Comparison of white pock (h) mutants of monkeypox virus with parental monkeypox and with variola-like viruses isolated from animals

Monkeypox mutants arising spontaneously or after serial, high multiplicity passage were characterized phenotypically and by restriction endonuclease mapping. Some resemble "whitepox" and variola viruses in several of the markers tested but all are distinguishable phenotypically from these. None resembles "whitepox" viruses in genome structure although near-terminal deletions or symmetrical, terminal rearrangements, relative to parental monkeypox, occurred. "Whitepox" viruses isolated from animals closely resemble variola in both phenotype and genome structure.

Variola virus strains of 1960--1975: the range of intraspecies variability and relationship between properties and geographic origin

A comparative study of 61 variola virus strains recovered from patients in various geographic regions of the world revealed significant intraspecies variability in some biological properties, established the range of this variability and demonstrated the existence of strains with atypical properties. There was a certain correlation between some laboratory markers of variola virus and the degree of its pathogenicity for man. The prevalence of more virulent and thermoresistant strains in the Hindustan subcontinent and the peculiarity and heterogeneity of the strains circulating in Africa were demonstrated. Alastrim virus was detected among the African isolates.

[Localization of specific antigen in the organs of newborn animals vaccinated with liver smallpox vaccine]

Of 20 suckling rabbits, 4-5-days old, inoculated with live smallpox vaccine intradermally 6 displayed symptoms of generalized pox virus and neuroparalysis complications. Intensive accumulation of specific antigen in the brain, lungs, spleen, and the lymph glands was revealed by immunofluorescent method. The smallpox vaccine virus was isolated from these organs. Prolonged persistance of the attenuated smallpox virus was observed in the brain, spinal cord, lungs, spleen, and the lymph glands of 14 suckling rabbits showing no signs of any disease; specific antigen was revealed by immunofluorescent test. Vascular disturbances and slight cell changes were observed in the brain tissue of the inoculated animals. These changes were more severe in the sick animals.

Viral diseases of the skin, 1975: a 25-year perspective

Most of the major advances in modern virology during the past 25 years have been due principally to the development of refined laboratory techniques and tools and have provided a fund of new knowledge and information about the nature of viral infection and pathogenesis. One group of viruses of interest to dermatologists, the herpesviruses, is undergoing intensive biochemical investigation to determine whether it is carcinogenic. As a result of the success of the World Health Organization's campaign to eradicate smallpox, it is predicted that by the end of 1976, smallpox will have been eradicated. Other viruses of dermatologic interest which are now being studied include the agents of warts, molluscum contagiosum, cat-scratch disease, and enteroviruses. Current research in the field of viral chemotherapy may provide the basis for successfully treating these diseases in the future.

[Use of electron microscopy for the rapid diagnosis of poxvirus diseases (smallpox) in swine]

For a rapid proving of the pig pox virus in the skin of naturally infected pigs, the simple electron microscopic method of negative staining was used. The result was checked by means of the finding of intracytoplasmatic inclusions in the histological sections and the proving of the presence of virions in the ultra-thin sections through the cells of the epidermis.

Virus content of smallpox scabs

Log titres of smallpoxvirus (pock-forming units per 0.1 g of scab) were estimated in scabs from 5 patients from the 13th to the 24th days of illness. They were found to vary from 3.72 to 6.54 with no diminution as convalescence progressed, and they were not related to the primary vaccination status of the patient or the clinical severity of the disease.

Virus excretion in smallpox. 2. Excretion in the throats of household contacts

Throat swabs of 34 of 328 family contacts of 52 smallpox cases, examined 4-8 days after the onset of the disease in the family, were positive for variola virus. The log titre of virus per swab ranged from 2 to 3.95. A higher proportion of unvaccinated than of vaccinated contacts excreted the virus. Only 4 of the virus-positive contacts developed clinical smallpox; this occurred 5-7 days after their swabs were examined. Excretion of virus in the throats of these contacts, a few of whom were in the incubation period of the disease, suggests the possibility that they could have spread the infection. This possibility, if kept in mind, may help in tracing the source of infection or in determining the incubation period in a few instances when difficulty is experienced.

Virus excretion in smallpox. 1. Excretion in the throat, urine, and conjunctiva of patients

Excretion of virus in the throat, urine, and conjunctiva of smallpox patients was studied daily for 2-3 weeks after the onset of fever. The virus titre in the throat and urine of haemorrhagic and confluent cases was higher than in discrete cases. The duration of virus excretion was also greater in confluent cases than in discrete cases. Conjunctival swabs from all 12 smallpox patients with conjunctivitis were positive for virus. The duration and titre of virus excretion in the throat, urine, and conjunctiva of patients were not related to their age or sex and did not depend on whether or not they had received a primary vaccination.

Evaluation of virological laboratory methods for smallpox diagnosis

Between July 1966 and May 1972 the Vesicular Disease Laboratory, Center for Disease Control, Atlanta, Ga., USA, tested specimens from 849 suspected smallpox cases by at least 2 methods, electron microscopy and chick embryo chorioallantoic membrane (CAM) cultures. A smaller number of specimens was tested by each of 4 methods: electron microscopy, CAM culture, agar gel precipitation, and tissue culture. For specimens handled in the field the CAM culture method was less sensitive than electron microscopy because the adverse conditions often inactivated the virus. CAM cultures were valuable for identifying members of the poxvirus subgroups, however, particularly when supplemented by tissue culture. The agar gel precipitation test was the least sensitive but was of value in confirming the results of electron microscopy. The latter was highly effective for the diagnosis of varicella, but dependably identified only about half of the vaccinia infections; for vaccinia, the CAM technique was essential. The occurrence of human monkeypox cases in West Africa emphasized that the usual smallpox diagnostic methods were inadequate. More sophisticated tests, such as the rabbit dermal sensitivity test, are necessary for accurate diagnosis of these cases as monkeypox.

Trsmission of smallpox by contact and by aerosol routes in Macaca irus

Smallpox is believed not to occur naturally in species other than man. However, reports of several epizootics of an exanthematous disease, similar to smallpox, in wild monkeys have raised the question of a simian reservoir. If such a reservoir for smallpox exists, the eradication of this disease from the world would be a difficult or impossible task. Transmission of smallpox in Macaca irus has been studied to determine whether transmission occurs and if infection chains can be maintained by this species.Transmission was consistently accomplished by both contact and aerosol routes. In the contact transmission studies, the smallpox infection was maintained through 6 passages but was lost with the seventh passage. The virulence of the virus did not appear to increase as the virus was serially passed in monkeys. Continuing studies of the possible occurrence of smallpox and of monkeypox in simian populations are warranted.