Hepatitis C virus-specific cytolytic T lymphocyte and T helper cell responses in seronegative persons

Hepatitis C virus (HCV) is a common infection worldwide, and in most persons, it leads to persistent viremia and liver damage. Efforts to identify the correlates of protective immunity are hampered by this high rate of persistent infection in both infected humans and the only animal model, the chimpanzee. Peripheral blood mononuclear cells from seronegative persons were stimulated with synthetic peptides that represent epitopes recognized by HCV-specific cytotoxic T lymphocytes (CTL) after natural infection. In addition, CD4+ proliferative responses to recombinant HCV proteins were examined in these same persons. CTL responses directed against a peptide epitope of HCV and proliferative responses in 2 HCV-seronegative persons with possible occupational exposure to HCV were found. These otherwise healthy persons were not viremic, suggesting that they may have recovered from acute HCV infection. Characterization of virus-specific immune responses in exposed but seronegative persons may provide important clues as to the nature of protective immunity in HCV.

A case of laboratory acquired infection with Escherichia coli O157:H7

A case of laboratory-acquired infection with Escherichia coli O157:H7 is presented. Evidence of the identity of the infecting strain was provided by toxin type and plasmid profiles. Because no obvious technical errors in laboratory practices could be demonstrated we conclude that the infecting dose for E. coli O157:H7 may be small. The clinical course was uncomplicated; during reconvalescence, the patient's serum recognized a unique 87 kDa band on immunoblots of the infecting strain.

Seroconversion to simian immunodeficiency virus in two laboratory workers

Simian immunodeficiency viruses (SIVs) are lentiviruses that cause acquired immunodeficiency syndrome (AIDS)-like illnesses in susceptible macaque monkeys and are used in the study of AIDS (1). In November 1988, CDC published guidelines to minimize the risk of SIV transmission to research laboratory workers (2). This report summarizes the investigation of two laboratory workers who seroconverted following occupational exposures to SIV.

Lymphocytic choriomeningitis outbreak associated with nude mice in a research institute

OBJECTIVE

After an employee at a cancer research institute was diagnosed with lymphocytic choriomeningitis, an investigation was performed to determine the extent of lymphocytic choriomeningitis virus (LCMV) infections among the institute's employees and to identify risk factors for infection.

DESIGN

Retrospective cohort study.

SETTING

A US cancer research institute.

PARTICIPANTS

Eighty-two of 90 institute employees.

MAIN OUTCOME MEASURES

Serum LCMV antibodies.

RESULTS

Seven workers (9%) with definite LCMV infection (LCMV IgG antibody titer greater than or equal to 16) and one worker (1%) with probable infection (IgG titer = 8) were identified (10% overall seroprevalence). All infected employees handled animals or animal tissues and were more likely than other animal handlers to have worked with nude mice (Mus musculus) (P less than .02). Among the 31 employees who worked with nude mice at the institute, infected workers were more likely to clean the cages of nude mice (P much less than .001), change their bedding (P less than .01), and change their water (P less than .001). The institute had been injecting nude mice with LCMV-infected tumor cell lines and had recently increased the nude mouse population and the duration of experiments. These changes would have increased the LCMV burden at the facility and were temporally associated with the cluster of LCMV infections in employees.

CONCLUSIONS

This LCMV outbreak, the first reported since 1974, is the first associated with nude mice. It illustrates the ongoing hazard LCMV poses in research laboratories. Since the symptoms of LCMV infection can be nonspecific, clinicians should consider this diagnosis in ill patients who report laboratory rodent exposure.

Risk of occupational exposure to Herpesvirus simiae (B virus) in Quebec

Herpesvirus simiae (B virus) causes a mild infection in macaques. Transmission to humans may result in life-threatening encephalomyelitis. To evaluate the risk of occupational exposure to B virus we surveyed the directors of 11 biomedical laboratories in Quebec that use monkeys. Information was obtained on the monkey population and on the use of infection control measures recommended by the US Centers for Disease Control (CDC), Atlanta. Of the 519 monkeys belonging to susceptible species the serologic status was positive in 264 (51%), all captured in the wilds, and it was unknown in 24 (5%). All of the monkeys were caged individually, and newly acquired ones were quarantined for 2 to 8 weeks. Of the 84 workers 52 (62%) handled monkeys whose serologic status was either positive or unknown. Only five laboratories (representing 61% of the workers) complied fully with the CDC guidelines. Nine of the laboratories had a wound management protocol, but only six had a designated specialist for consultation and prophylaxis. Although no cases of B virus infection have been reported from Quebec the severity of human illness necessitates strict adherence to infection control measures and expert management of occupational exposure to susceptible monkeys.

[Occurrence of HBs antigen and anti-HBs antibodies in analytical laboratory workers in Warsaw]

The study aimed at answering the question whether markers of the viral hepatitis, namely HBs antigen and anti-HBs antibodies, are significantly more frequent in the personnel of the analytical laboratories than in blood donors of the City Blood Donation Centre. Together 1,284 persons employed at 88 analytical laboratories were examined. These persons were divided into the groups according to the occupation, age and duration of the employment. HBs antigen was detected with EIA technique in 13 subjects making 1,025% of all examined individuals whereas anti-HBs antibodies were detected with EIP technique in 20 subjects, i.e. 1,560%. Detectability of HBs antigen and anti-HBS antibodies in blood donors was 0.443% and 0.04% respectively. The obtained results indicate significantly more frequent occurrence of both markers in the employees of the analytical laboratories.

Comparison of different serotests for specific Toxoplasma IgM-antibodies (ISAGA, SPIHA, IFAT) and detection of circulating antigen in two cases of laboratory acquired Toxoplasma infection

Two symptomatic Toxoplasma infections of laboratory personnel have been serologically followed up for 5.5 and 10 months, respectively. Results obtained by commonly used test systems (indirect fluorescent antibody tests for IgG and IgM antibodies, complement fixation test) were compared with those of two recently developed and improved tests for IgM detection (immunosorbent agglutination assay [ISAGA] and solid-phase indirect haemadsorption assay [SPIHA] as well as with those of a test designed for the detection of circulating antigen (cag-ELISA).

Rabies pre-exposure prophylaxis using intradermal human diploid cell vaccine: immunologic efficacy and cost-effectiveness in a university medical center and a review of selected literature

The authors studied the antigenicity of intradermal human diploid cell rabies vaccine administered to 40 laboratory workers considered to be at-risk at the University of Virginia Medical Center. A 1-year postvaccination serology was determined for 20 of those 40, all of whom demonstrated an antirabies titer greater than or equal to 1:50 by the raped fluorescent focus inhibition test. By 2 years' postvaccination, 5 of 40 subjects had "unprotective levels" (less than 1:5), whereas 35 had titers greater than or equal to 1:5, and none had a titer greater than or equal to 1:50. Booster doses given to four subjects whose titers had declined produced a 1-month postvaccination antirabies titer greater than or equal to 1:50 in all cases. Vaccine administration by the intradermal rather than the intramuscular route resulted in a cost savings of $120 (U.S.) per employee. This data indicate that the intradermal administration of human diploid cell vaccine for rabies pre-exposure prophylaxis achieves an immunologic response thought to be protective while providing a substantial cost savings when compared with the intramuscular route of administration. Those who receive primary pre-exposure rabies vaccination should have serologic confirmation of immunologic protection every 2 years with a booster dose given to subjects demonstrating a titer less than 1:5.

Serological studies on a case of laboratory dengue infection

One of the authors (Y.O.), who had previously been immunized with Japanese encephalitis (JE) vaccine, showed symptoms of typical dengue fever 6 days after accidental infection with a newly isolated dengue type 4 virus strain from a patient with dengue hemorrhagic fever (DHF) in Thailand. His sera were examined by hemagglutination inhibition (HI), complement fixation (CF) and neutralization (N) tests. The JE N antibody titers of his sera were high even on the first day of the illness and remained almost constant during the next year. Antibodies that reacted with dengue viruses were detected from a very early stage of the illness by all three serological tests. In addition, his convalescent phase sera showed high titers against all 4 types of dengue virus. These data suggest that the dengue infection caused secondary stimulation of antigens of flavivirus. Sedimentation analysis of antibodies in Y.O.'s serum (day 9) was carried out and IgM antibody that reacted only with dengue type 4 virus and homologous infecting virus was separated. These findings clearly demonstrated that the laboratory infection of Y.O. was primary dengue infection with dengue type 4 virus.

Arbovirus infections among laboratory personnel in Ibadan, Nigeria

Laboratory-acquired infections encountered between 1963 and 1977 among personnel of the Virus Research Laboratory, Ibadan, Nigeria, are reported. Two cases of chikungunya infection occurred and one each with Dugbe, Wesselsbron, and dengue viruses. In each case, virus was isolated or development of antibody demonstrated. Among virus and two each to chikungunya and Rift Valley fever viruses, without experiencing any clinically recognized disease.

Use of a sensitive microplate enzyme-linked immunosorbent assay in a retrospective serological analysis of a laboratory population at risk to infection with typhus group rickettsiae

A microplate enzyme-linked immunosorbent assay (ELISA), developed for the detection of antibodies to typhus group rickettsiae, was used to analyze human sera from individuals engaged directly or indirectly in rickettsial research. The earliest serum available from each of 112 individuals was tested for immunoglobulin M (IgM) and IgG antibodies against Rickettsia typhi and Rickettsia prowazekii by ELISA at a 1:500 dilution. In at least one assay, nine sera had ELISA optical densities of greater than 0.2, which were above the mean optical densities plus three standard deviations of the other 103 sera. Three of the positive sera were from individuals with known clinical cases of typhus infection. The other sera with predominantly IgG titers were from individuals with extended laboratory exposure to rickettsiae or histories of typhus vaccination, or both. During continued serological surveillance, eight additional people with repeated occupational exposure to typhus rickettsiae had seroconversions in the ELISA to optical densities of greater than 0.2. No apparent clinical illness occurred in two individuals, whereas six clinical cases of infection occurred in others subsequent to accidental laboratory autoinoculation (one) or aerosol exposures (five). In the clinical infections, antibodies were first detected at 7 days, but in subsequent sera, rises and declines in titers were quite variable and were influenced by vaccination, relapse, and time and extent of antibiotic therapy. In primary infections the sera of several individuals who received immediate antibiotic therapy had brief strong IgM responses without pronounced increases in IgG. In contrast, much higher IgG levels were attained in three cases in which relapse occurred, the individual had previously been immunized, or treatment had been delayed. The microplate ELISA proved to be a highly sensitive and reliable test for detection of the human serological response to typhus antigens.

California encephalitis group viruses isolated from mosquitoes collected in Southern and Arctic Norway

Three virus strains serologically related to the California encephalitis group (Bunyaviridae) of arboviruses were isolated from 7331 mosquitoes collected in Norway in June-August 1975. Two of the isolates (S 548 and S 618) seemed to be closely related and the third, S 568, more distantly related by serological techniques to Tahyna virus. Viruses were found in the mosquito species Aedes sticticus, A. diantaeus and A. hexodontus colllected (in order) from Oyern (59 degrees N, 11 degrees 12' E), Trandum (60 degrees 08' N, 11 degrees 10' E) and Masi (69 degrees 26' N, 23 degrees 39' E). The Masi isolate seems to be the northernmost arbovirus isolate in the world so far. Strain S 568 was from 16 male A. diantaeus, indicating transovarial transmission of the virus. An accidental infection demonstrated the potential human pathogenicity of one of the newly-isolated strains (S 568), and the ability of CE viruses to persistently infect suckling mouse brains was indicated by in vivo findings. The biological characteristics of the new strains so far investigated are consistent with those of the California encephalitis group. During this work the Aerosil absorption method for production of haemagglutinating antigens proved useful for Tahyna virus and the newly-isolated strains. Trypsinization of erythrocytes improved the haemagglutinating capacities of these viruses.

Immunization against tularemia: analysis of the effectiveness of live Francisella tularensis vaccine in prevention of laboratory-acquired tularemia

A retrospective analysis was made of cases of laboratory-acquired infections with Francisella tularensis among civilian employees at Fort Detrick, Maryland. The incidence and clinical presentation of tularemia during the decade 1950-1959, when the phenol-killed Foshay vaccine was used routinely for immunization of employees, were compared with similar data from the first decade (1960-1969) after the live tularemia vaccine had come into use. The incidence of typhoidal tularemia fell (from 5.70 to 0.27 cases per 1,000 at-risk employee-years; P less than 0.001), whereas the incidence of ulceroglandular tularemia remained unchanged (from 0.76 to 0.54 cases per 1,000 at-risk employee-years). Ulceroglandular tularemia in employees immunized with live vaccine was characterized by clinical signs and symptoms that were milder than those in employees vaccinated with the Foshay vaccine.