Vaccinia virus, smallpox

Members of the poxvirus, herpesvirus and retrovirus families produce homologues that mimic RCA proteins and are thus able to escape complement action.20 The smallpox virus Variola major causes a serious, virulent infection in humans, while the virus that is used for vaccination against smallpox, vaccinia virus, usually causes only a very mild or even unapparent infection, at least in individuals with an intact immune system. 

Vaccines Vaccinia virus is a live poxvirus that can lead to strong cross-protection to smallpox for about five years, plus partial protection for ten or more years. If your are old enough, or have been in military service in recent years, you may have been vaccinated with this vaccine administered by dermal scarification, or intra-dermal jet injection. However, certain persons should NOT receive smallpox vaccine, including persons who are pregnant, persons who underwent a clinical immunosuppresion, persons with eczema, or persons with leukemia or lymphoma. 

No, smallpox vaccine does not contain smallpox virus but another live virus called vaccinia virus. Since this virus is related to smallpox virus, vaccination with vaccina provides immunity against infection from smallpox virus. 

The vaccine against smallpox is made with a virus related to smallpox virus called vaccinia virus. It is not made with smallpox virus called variola. The vaccine is a highly effective immunizing agent against smallpox infection. It was successfully used to eradicate smallpox from the human population. 

In addition to the stock of smallpox vaccine in the US, an additional 50-100 million doses are estimated to exist worldwide. Many countries still hold smallpox vaccine (vaccinia) stocks. WHO recommends that countries that still have stocks of smallpox vaccine (vaccinia) maintain these stocks. This recommendation has been made for two reasons. Firstly, small amounts of vaccine are still needed to vaccinate laboratory personnel handling vaccinia virus and other members of this virus family. Some of these viruses are found in nature and cause illness among animals, and some are used in research to make new, safer vaccines against a variety of infectious diseases. Secondly, smallpox vaccine, vaccinia, will also be needed in case of a deliberate or accidental release of smallpox virus, variola. 

The most notable example of live attenuated vaccines is the smallpox vaccine, first developed by Edward Jenner, although the origin of the vaccine (vaccinia virus) remains obscure. More recent examples of live attenuated vaccines include most of the viral vaccines currently in use, such as measles/mumps/rubella (MMR) and varicella zoster (VZV) vaccines, and some... 

Shalaby WSW (1995) Development of oral vaccines to stimulate mucosal and systemic immunity barriers and novel strategies. Clin Immunol Immunopath 74(2) 127-134 Sharon M, Nir P, Lior K, David BN, Tomer I, Paula S, Reuven L, Shlomo L (2007) Tail scarification with Vaccinia virus Lister as a model for evaluation of smallpox vaccine potency in mice. Vaccine 25(45) 7743-7753... 

Smallpox vaccines EMEA note for guidance on the development of vaccinia virus-based vaccines against smallpox 2002... 

A 26-year-old laboratory worker, who had been vaccinated against smallpox in childhood, developed a pustule and erythema on his left thumb 3 days after an accidental needle-stick while working with Vaccinia virus. Further pustules occurred on the fourth and fifth fingers of the same hand, accompanied by a large... 

A 13-year-old girl died of neuromyelitis optica. By inoculation of rabbits it was shown that the brain tissue contained Vaccinia antigen. Moreover, there were high titres against Vaccinia virus in both sera and spinal fluid. In infancy this patient had been vaccinated against smallpox (37). 

The term vaccination originated with the smallpox vaccine. In 1796, Edward Tenner developed an effective method for producing smallpox immunity by inoculating people with material from a cowpox lesion. He named the method vaccination, based on vacca, the Latin word for cow. During the nineteenth century, vaccinia virus, a related but genetically distinct Orthopoxvirus, replaced the cowpox virus in the vaccine (25). 

Inadvertent inoculation, the most frequent complication of smallpox vaccination, refers to the transmission of the vaccinia virus from the inoculation site to another part of the recipient s body (autoinoculation) or to the bodies of close contacts (Fig. 2.8 see color plate 2.8). It can occur because live vaccinia virus is present at the inoculation site from about 4 days after inoculation until the crust separates from the skin. Maximum viral shedding occurs 4-14 days after inoculation. Inadvertent inoculation is responsible for approximately half of all complications for primary vaccination and revaccination. Because inadvertent inoculation frequently results from touching the vaccination site and transmitting the virus manually, the most common affected sites are the face, eyelid, nose, mouth, genitalia, and rectum. Most cases heal without any specific treatment. Inadvertent inoculation of the eye can lead to comeal scarring and subsequent vision loss. Occasionally, vaccinia immune globulin (VIG) is necessary to treat periocular lesions (26). 

Another example concerns the potentiation of a virulence factor of vaccinia virus, the strain used for smallpox vaccinations.3 In this case a property (factor) of the virus was engineered to more effectively eliminate an essential component of the innate immune system, which acts as the first line of defence against an infection. 

However, large viruses such as smallpox (and other pox viruses) have evolved ways of disrupting the immune system. It has been found, for example, that in vaccinia (the viral strain used to make smallpox vaccine) there is a vaccinia virus complement control protein (VCP) which binds to and inhibits C3b and C4b. In 2002, by... 

D. Vaccine/Prophylaxis. Smallpox vaccine (vaccinia virus) is a licensed live poxvirus vaccine that induces strong cross-protection against smallpox. Reliable data are sparse as to efficacy and durability of protection. The duration vaccinia induced immunity is at least 3 years. Vaccine immunity may prevent or modify illness. Fully immune individuals exposed to the virus by the respiratory route may develop fever, sore throat, and conjunctivitis ("contact fever") lasting several days. The vaccine is administered by dermal scarification or intradermal jet injection. The appearance of a vesicle or pustule within several days indicates that the vaccine will be effective. Other available countermeasures include the postexposure use of Vaccinia immune globulin or primary vaccination within 3-4 days of exposure yields some protection. 

Smallpox vaccine is a viral vaccine. Introduction of infectious vaccinia virus into superficial layers of the skin results in viral multiplication, immunity and cellular hypersensitivity. It is used in immunization against smallpox disease. 

Genetically Engineered Vaccinia Virus - The vaccinia viruses, or pox virus, cause a number of diseases characterized by skin lesions in both humans and animals. With some pox virus types, for example variola (smallpox), the lesions can be considerably disseminated and deadly. The virus is an enveloped DNA virus with a large genome (180,000 base pairs) coding for over a hundred proteins. The virus has its own RNA... 

Vidarabine is used mainly in human HSV-1 and HSV-2 encephalitis, decreasing the mortality rate from 70 to 30%. Whitley et al. (57) reported that early vidarabine therapy is helpful in controlling complications of localized or disseminated herpes zoster in immunocompromised patients. Vidarabine also is useful in neonatal herpes labialis or genitalis, vaccinia virus, adenovirus, RNA viruses, papovavirus, CMV, and smallpox virus infections. Given the efficacy of vidarabine in certain viral infections, the U.S. FDA approved a 3% ointment for the treatment of herpes simplex keratoconjunctivitis and recurrent epithelial keratitis, and a 2% IV injection for the treatment of herpes simplex encephalitis and herpes zoster infections (Table 43.3). A topical ophthalmic preparation of vidarabine is useful in herpes simplex keratitis but shows little promise in herpes simplex labialis or genitalis. The monophosphate esters of vidarabine are more water-soluble and can be used in smaller volumes and even intramuscularly. These esters are under clinical investigation for the treatment of hepatitis B, systemic and cutaneous herpes simplex, and herpes zoster virus infections in immunocompromised patients. 

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