A 43-year-old woman healthy laboratory worker, not previously vaccinated against smallpox presented to the emergency department with a 5-day history of a nodule in the second right finger (Fig. 1A). These symptoms appeared 6 days after she had been handling Western Reserve Vaccinia strains. She denied any laboratory accident while working, but she realized she had a broken glove which must have occurred while handling the centrifuge tube cap. Local symptoms worsened, and on day 7 she noticed a hemorrhagic bulla surrounded by erythematous and flogotic skin (Fig. 1B) so bacterial superinfection was diagnosed and amoxicillin/clavunate was prescribed. The patient improved slowly (Fig. 1C and D) to give way to a small lesion with crusting (Fig. 1E) which gradually disappeared over the next two months (Fig. 1F–H) until its completely resolution.
Progression of local reaction on the second right finger after accidental inoculation with vaccinia virus (A: day 5, B: day 6, C: day 11, D: day 14, E: day 38, F: day 49, G: day 65 and H: day 120). WB analysis of proteins expressed in cell lines infected with poxvirus. Lysates from BSC40, DEF-1 or HTerT cells infected at an MOI of 10 with WR, MVA or MpX were transferred to nitrocellulose and used for Western blot analysis using the human serum collected from the infected laboratory worker as the primary antibody. An arrow indicates the protein detected exclusively in MPX infected cell lysates and an asterisk for in MVA-infected lysates.
The patient refused the direct sampling from the lesion, so the PCR could not be performed. Since the lesion was highly characteristic of vaccinia, the virus exposure and the clinical progression was favorable, no further insistence was made, and only serology was performed on the obtained blood sample.
Serum was isolated from an analytical blood sample of the infected worker and used as the primary antibody in an indirect Western blot (WB) analysis to assess the possible presence of poxvirus protein antibodies. To confirm the presence of poxviral antibodies in the serum, a collection of monkey, hamster and human cell lines were infected with several poxviruses, and viral proteins were analyzed by WB using the collected serum (Fig. 1I). Viral antibodies presented in the serum were numerous and allowed the identification of different poxvirus strains (Fig. 1I). Specifically, human anti-vaccinia virus antibodies were primarily reactive against vaccinia virus (VACV) (WR and MVA) and monkeypox (MPOX) proteins with a molecular mass of approximately 75 (absent in MVA), 62 (absent in MPOX), 59 (absent in MVA), 35, 33, 25 (19 in MPOX) and 14kDa. There was one prominent band with a molecular mass greater than 80kDa in MPOX-infected cell lysates that were not present in WR- or MVA-infected cell lysates (Fig. 1I arrow) and others greater that 38 presents exclusively in MVA-infected sample (Fig. 1I, asterisk). In parallel, we performed an additional WB using a specific antibody against VACV viral protein (E3) validating our results of poxvirus infection (Fig. 1J).
VACV is used in the laboratory for a wide variety of purposes in the development of recombinant vaccines, immunotherapies, or oncolytic virotherapies.1 However, it is potentially pathogenic in humans, and laboratory-acquired infections have been reported.2 VACV is highly contagious through contact with lesion exudates,3 and although it is less virulent than other poxviruses we cannot rule out its high pathogenicity in immunocompromised personnel, so it is necessary that laboratory workers would be fully vaccinated and use of safety precautions. As studies indicate robust VACV-specific immune responses in humans following vaccination, pre-exposure vaccination4 with VACV may prevent laboratory workers. The Advisory Committee on Immunization Practices recommends routine vaccination with live smallpox vaccine for laboratory personnel who directly work with this virus or other orthopoxviruses that infect humans to avoid possible transmission.5
This kind of vaccinia lesions have good prognosis although resolution is slow and a scar can persist. Treatment is usually symptomatic and the main aim is avoid complications as bacterial superinfections.
Authors’ contributionsEvery author contributed equally to the manuscript in redaction, writing, reviewing and submission.
FundingThis article didn’t receive any funding.
Conflict of interestThe authors have declared no conflicts of interest.
