Histoplasma capsulatum infections of the central nervous system. A clinical review.

Central nervous system manifestations occur in 10 to 20% of patients with disseminated histoplasmosis. Additionally, histoplasmosis may be the cause of cases of chronic meningitis in patients with no other evidence for dissemination. Histoplasmosis may also cause cerebral or spinal cord mass lesions resembling neoplasms or abscesses, and encephalitis. Diagnosis of chronic meningitis or mass lesions caused by H. capsulatum may be difficult and involves careful analysis of serologic tests for antibodies, cultures and tests for HPA in body fluids. Amphotericin B remains the treatment of choice, but relapses occur in half of cases despite total courses of at least 35 mg/kg. Accordingly, careful long-term follow-up is required to identify patients with relapsing infection. Newer antifungal agents which cross the blood brain barrier are needed. A trial of amphotericin B treatment without surgical excision can be justified in patients with cerebral or spinal cord histoplasmomas, in view of the apparent success of such treatment in a few cases. Progression of clinical abnormalities or persistence of the lesion following completion of treatment would support the need for surgical excision.

Clinical and laboratory features of disseminated histoplasmosis during two large urban outbreaks.

Clinical and laboratory features have been reviewed in 66 episodes of disseminated histoplasmosis that occurred during two large urban outbreaks in Indianapolis. Immunosuppression, age greater than 54 years, and presence of other serious underlying illnesses predisposed to the disseminated form of the disease; only 21% of patients lacked one of these risk factors. Central nervous system findings, splenomegaly, hepatomegaly, and lymphopenia suggested disseminated disease but were present in only about one-third of patients. Miliary or diffuse pulmonary infiltrates also suggested dissemination and were noted in about one-third of patients, while mediastinal lymphadenopathy was present in only 17%. Histoplasmal serologic tests, positive in 90% of patients, provided useful diagnostic clues. The diagnosis could be confirmed by culture in 88% of patients, and special stains were positive in about two-thirds. Although 10% of patients recovered without treatment, 11 patients (17%) died because of failure to suspect the diagnosis and initiate therapy promptly. Amphotericin B was effective in all patients receiving at least 500 mg, but relapse occurred if the total dose was less than 30 mg/kg. Ketoconazole appeared effective in non-immunosuppressed patients but not in those with underlying immunosuppression; however, a controlled trial comparing ketoconazole and amphotericin B is required to establish the role of this new fungistatic oral agent.

Efficacy and safety of ofloxacin in the treatment of nongonococcal sexually transmitted disease.

This study compared doxycycline with ofloxacin in the treatment of nongonococcal urethritis in men and mucopurulent cervicitis in women and compared both drugs in the treatment of infections due to Chlamydia trachomatis in both men and women. Informed consent was obtained from all subjects. Eighteen men with nongonococcal urethritis and 12 with previously positive chlamydial cultures were randomly treated with doxycycline or ofloxacin. Eleven women with mucopurulent cervicitis, 14 with a previous positive untreated chlamydial culture, and nine having sexual contacts with men known to have chlamydial urethritis also were randomly treated. Culture specimens for chlamydia were obtained before treatment, five to nine days after therapy (return visit 1), and 21 to 28 days after therapy (return visit 2). Cultures for Ureaplasma urealyticum were obtained only in men. There were no significant differences in results in patients treated with doxycycline or ofloxacin. All but three of 20 men with symptoms were symptom-free on return visit 1 and all were symptom-free on return visit 2. Thirteen women with mucopurulent cervicitis had all resolved at visit 1, although signs of cervicitis reappeared at the second visit in two patients treated with doxycycline and one treated with ofloxacin. All patients with positive chlamydial cultures had negative cultures at the first return visit. One patient treated with doxycycline was positive at the second return visit. Laboratory and clinical abnormalities were mild and did not prevent completion of therapy. These data, together with previous published and unpublished data, indicate that ofloxacin is as effective as doxycycline in the treatment of chlamydial infections. The study also demonstrated that ofloxacin and doxycycline were equally effective in the treatment of nongonococcal urethritis in men and mucopurulent cervicitis in women.

Chlamydial infections.

Sexually transmitted infections caused by Chlamydia trachomatis are of epidemic proportions. Since chlamydial infections are often asymptomatic, identification of infected persons is the major public health challenge in the control of chlamydial disease. Unfortunately, asymptomatic infections in women can be complicated by salpingitis, ectopic pregnancy, and involuntary infertility. The best current diagnostic test is cell culture. Direct antigen tests are cheaper and more widely available than cell culture but are less sensitive. Improved diagnostic tests, screening of groups at risk, educating patients and health care providers, and reporting of chlamydial infections will be essential in controlling chlamydial disease.

Gender differences in sexual behaviours in response to genitourinary symptoms.

OBJECTIVE: To understand gender differences in sexual behaviours in response to genitourinary symptoms. METHODS: 473 (239 female and 234 male) subjects were enrolled at an STD clinic regardless of symptoms or infection status. Subjects completed a 30 day calendar recall interview of genitourinary symptoms, coital activity, sexual partners, and condom use. RESULTS: Of the total of 473 participants, 261 (55%) reported symptoms (61% women and 39% men). STI prevalence was 73% and 75% for symptomatic women and men, respectively. For black women the probability of coitus was decreased in the presence of vaginal discharge (OR 0.64, 95% CI 0.47 to 0.89). No change in coital activity was seen in non-black women in the presence of vaginal discharge. Having vaginal discharge did increase the likelihood of condom use by their partners (OR 2.48, 95% CI 1.05 to 5.88), if coitus occurred. Urethral discharge was not associated with coitus or condom use in men. However, in men, dysuria was associated with increased likelihood of condom use (OR 4.25, 95% CI 1.57 to 11.56) if coitus occurred. CONCLUSION: Black women altered both coital activity and condom use behaviours in response to vaginal discharge. In contrast, non-black women did not modify coital activity. Men increased condom use when having dysuria but did not alter coital activity. Changes in sexual behaviours may alter the risk of STI transmission independent of interactions with the healthcare system. STI education and prevention programmes need to better understand these gender and racial differences in developing effective strategies to reduce STI transmission.

The major outer membrane protein of a single Chlamydia trachomatis serovar can possess more than one serovar-specific epitope.

The major outer membrane proteins (MOMPs) of human Chlamydia trachomatis serovars exhibit four regions of variable amino acid sequences (VS1 to VS4) harboring serovar-specific B-cell epitopes. Antibody responses to these epitopes may contribute to acquired protection against human chlamydial infection. MOMP B-cell epitopes defined by 22 different serovar-specific or bispecific murine monoclonal antibodies were localized with synthetic peptides representing the four VS regions of seven genital serovars (D, Da, E, F, G, H, and K). Serovar F possessed two distinct serovar-specific epitopes, located in VS2 and VS4, while serovar K possessed three distinct serovar-specific epitopes, located in VS1, VS2, and VS4. Serovar D- and serovar Da-specific epitopes were located in VS1. Regardless of whether the serovar was from the B (serovars D, Da, and E), C (serovars H and K), or F-G (serovars F and G) serogroup, all serovar-specific epitopes were found in three discrete subgroups of MOMPs. These subregions comprised all central portion of VS1, residues 70 to 77; the amino-terminal half of VS2, residues 139 to 149; and the carboxyl-terminal third of VS4, residues 305 to 315. Monoclonal antibodies to each of these subregions neutralized infectivity in standard HaK cell culture assays. These findings are relevant to the development of an MOMP or MOMP subunit vaccine.

Analysis of the humoral immune response to chlamydial genital infection in guinea pigs.

Studies using the guinea pig model of chlamydial genital infection with the Chlamydia psittaci agent of guinea pig inclusion conjunctivitis (GPIC) have shown that serum and local antibodies play a role both in the resolution of infection and in protection against reinfection. Thus, this model is suited for further exploration of immune mechanisms and for vaccine studies with chlamydial macromolecules. We have further characterized the model by assessing the antigen-specific antibody response to experimental genital infection by using immunoblotting to assay both genital secretions and serum. The GPIC agent was characterized by analysis of outer membrane proteins, which indicated that the GPIC agent possessed a major outer membrane protein (MOMP), with a molecular mass of 39 kilodaltons (kDa), and a 61-kDa protein, analogous to cysteine-rich 60-kDa proteins or doublets of Chlamydia trachomatis strains. As indicated by immunoblotting, most infected animals produced serum immunoglobulin G antibodies to MOMP, the 61-kDa proteins, an 84-kDa outer membrane protein, and lipopolysaccharide. Such serum antibodies persisted for at least 813 days after primary genital infection. Immunoglobulin A antibodies against the 61-kDa proteins, lipopolysaccharide, and MOMP, but not the 84-kDa protein, were detected in secretions. Animals challenged with GPIC 825 days after primary infection became infected again despite the presence of serum antibodies, but the period of chlamydial shedding was significantly shorter and less intense than in primary infections. Although the specific mechanism is not known, these data suggest that a long-lasting immune effect is capable of altering the course of infection late after primary infection. Correlation of the antigen-specific antibody response and other immune parameters with the duration and degree of protective immunity induced by infection or vaccination may be helpful in further understanding the nature of such protective immunity.

Protective role of serum antibody in immunity to chlamydial genital infection.

Female guinea pigs were injected intraperitoneally with pooled immunoglobulin derived from animals immunized to the chlamydial agent of guinea pig inclusion conjunctivitis. Genital infections in animals receiving pooled immunoglobulin from immune animals were markedly decreased with regard to the number of inclusions detected compared with control animals. These data indicated that serum-derived antibody was able to provide a degree of protection against a chlamydial genital tract infection.

Susceptibility to reinfection after a primary chlamydial genital infection.

Female guinea pigs which had been infected genitally with the agent of guinea pig inclusion conjunctivitis were challenged at various times after infection with fresh inocula to determine the duration of immunity resulting from the primary infection. At 30 days after infection, most guinea pigs were resistant to reinfection, as indicated by the inability to isolate chlamydiae from cervical swabs. However, at 77, 155, and 294 days, all animals became reinfected, although the course of the infection was abbreviated and of lower intensity. When various immune parameters were examined, a decrease in antibodies in both serum (immunoglobulin G [( IgG]) and genital secretions (IgA, IgG) was observed after 30 days. A decrease in antibodies to the major outer membrane protein and an 84K component was noted in serum. In genital secretions, IgA antibodies to all major chlamydial components declined markedly after 30 days. Cell-mediated immunity as measured by proliferation of peripheral blood lymphocytes to guinea pig inclusion conjunctivitis antigen also was at a peak response 30 days after infection and decreased thereafter. Thus, loss of complete immunity could not be associated with a particular immune parameter. When genital secretions were examined 14 days after the challenge infection, IgA antibody levels to the lipopolysaccharide and 61K protein components had increased in intensity, whereas other antibodies were relatively low. In addition, complete immunity to a third infection was not increased in duration when animals had recovered from two previous genital infections.

Differences in outer membrane proteins of the lymphogranuloma venereum and trachoma biovars of Chlamydia trachomatis.

The lymphogranuloma venereum (LGV) and trachoma biovars of Chlamydia trachomatis exhibit differences in biological properties both in vivo and in vitro. To identify analogous biochemical differences, we studied the molecular charges of chlamydial outer membrane proteins (OMPs) by means of isoelectric focusing and nonequilibrium pH gradient electrophoresis. Analysis of proteins of whole elementary bodies biosynthetically labeled with L-[35S]cysteine revealed that most chlamydial proteins were neutral or acidic. The major OMPs (MOMPs) of all strains tested were acidic and had apparent isoelectric points (pIs) that varied within narrow limits (approximately 5.3 to 5.5) despite differences in molecular mass of up to 3,000 daltons (Da). However, a low-molecular-mass cysteine-rich OMP analogous to that previously described for Chlamydia psittaci varied consistently in molecular mass (12,500 versus 12,000 Da) and pI (5.4 versus 6.9) between LGV strains and trachoma strains, respectively. OMPs with a molecular mass of 60,000 Da in the trachoma biovar strains had pIs in the 7.3 to 7.7 range. However, analogous OMPs in the LGV strains existed as a doublet with a molecular mass of about 60,000 Da. Both members of the doublet were basic (pIs greater than 8.5). Both proteins of this basic doublet in LGV strains and the neutral analog in trachoma strains bound a species-specific monoclonal antibody in an immunoblot assay. These data indicate substantial differences in biochemical characteristics of analogous OMPs in the LGV and trachoma biovars. Such differences are the first structural differences described between LGV and trachoma strains which support their distinction into separate biovars and may be related to some of their biological differences.

Immunization against chlamydial genital infection in guinea pigs with UV-inactivated and viable chlamydiae administered by different routes.

Female guinea pigs were immunized with viable or UV light-inactivated chlamydiae (agent of guinea pig inclusion conjunctivitis), belonging to the species Chlamydia psittaci, by intravenous, subcutaneous, oral, or ocular routes. All animals were then inoculated vaginally with viable chlamydiae to determine the extent of protection against challenge infection induced by the various regimens. The course of genital infection was significantly reduced in intensity in all groups of animals except the unimmunized controls and those animals immunized orally with inactivated antigen. Guinea pigs immunized with viable antigen were more likely to develop resistance to challenge infection and, in general, had a significantly greater degree of protection than animals immunized with inactivated antigen. No one route seemed superior in producing a protective response. Animals in all groups demonstrating protection developed serum and secretion immunoglobulin G antibody responses to chlamydiae. Lymphocyte proliferative reactions to chlamydial antigen were variable among groups. Immunoblot analysis of serum and secretions indicated a wide range of antibody specificities, but most protected animals produced antibodies to the major outer membrane protein, lipopolysaccharide, and the 61-kilodalton protein. No definitive associations could be made between the increased ability of immunization with viable organisms to produce resistance to challenge infection and a particular immune parameter. These data indicate that viable chlamydiae given by various routes are able to induce a strong immune response which can provide resistance against reinfection in some cases or at least reduce the degree of infection to a greater degree than inactivated antigen. However, complete resistance to genital tract infection may be difficult to obtain and alternate immunizations strategies may have to be developed.

Effect of prior sexually transmitted disease on the isolation of Chlamydia trachomatis.

In developed nations, Chlamydia trachomatis is the most common sexually transmitted pathogen. To determine whether prior disease affects the probability of subsequent chlamydial infection, we took culture specimens from 2,546 men and 1,998 women attending a sexually transmitted diseases clinic. The men had nongonococcal urethritis and the women were contacts of men who had a positive chlamydial culture or nongonococcal urethritis. Significantly lower isolation rates for those with a history of sexually transmitted diseases were found for both men (29% vs. 38%; P less than 0.0001) and women (27% vs. 36%; P less than 0.0001). In addition, both men and women with previously documented chlamydial infections had a lower isolation rate at the index visit, if the previous infection occurred less than, as opposed to more than, six months earlier (men: 20% vs. 41%; P = 0.0006; women: 14% vs. 35%; P = 0.003). These relationships were found to be independent of age. However, the effect of partial immunity due to prior infection could not be distinguished from that of prior antibiotic therapy, and if such immunity does confer protection against reinfection, that protection appears to be both partial and of relatively short duration.

A randomized trial to compare 7- and 21-day tetracycline regimens in the prevention of recurrence of infection with Chlamydia trachomatis.

Standard therapy for Chlamydia trachomatis in the United States consists of a 7-day course of tetracycline administration. Recurrent infections are frequent, however, in circumstances in which reinfection seems unlikely, suggesting that the standard regimen may be insufficient to cure the infection. It may reduce the number of organisms, however, below a detectable level at a test-of-cure visit. To evaluate recurrent infection, the authors studied patients with chlamydia who were treated with standard therapy, and they found a recurrence rate of 29% among 2,983 patients who returned to the clinic during a 2-year follow-up period. Recurrent infection was associated with younger age but was not related to either race or gender. To test the hypothesis that a longer treatment course might be more effective in preventing recurrent infection, the authors conducted a randomized trial that compared 7- and 21-day regimens of tetracycline administration. Of the 918 subjects enrolled in the trial, 220 were infected with C. trachomatis. The overall recurrence rate among patients who were infected and returned was 18.4% (9/49) in the 21-day group and 13.8% (8/58) in the 7-day group (P = .60). Similar results were obtained using survival analysis methods. Given the number of subjects who returned, this study had approximately a 65% statistical power to detect a reduction in recurrence rate, from 20% to 5%. Because of the similarity of the results in the two groups, it was concluded that 21 days of tetracycline administration is no more effective in preventing recurrence than 7 days of administration.

Women at risk for gonorrhea: comparison of rosaramicin and ampicillin plus probenecid in the eradication of Neisseria gonorrhoeae, Chlamydia trachomatis and genital mycoplasmas.

Rosaramicin is a macrolide antibiotic with activity against Neisseria gonorrhoeae, Chlamydia trachomatis, and the genital mycoplasmas Ureaplasma urealyticum and Mycoplasma hominis. Its efficacy in the treatment of genital infections was evaluated and compared with that of single-dose ampicillin plus probenecid in women with known, or suspected, uncomplicated gonococcal infection. Isolation rates for N. gonorrhoeae, C. trachomatis, U. urealyticum, and M. hominis were 72%, 44%, 95%, and 65%, respectively. Rosaramicin cured 24 (89%) of 27 gonococcal infections and 11 (92%) of 12 chlamydial infections. It transiently reduced the carriage of U. urealyticum but had little effect on carriage of M. hominis. Rosaramicin may be of value in the treatment of concurrent gonococcal and chlamydial infections when tetracycline is contraindicated.

Hepatitis B virus vaccine: a randomized trial of a reduced dose regimen in hemodialysis patients.

To test the hypothesis that increasing the dose enhances response to hepatitis B virus vaccine in hemodialysis patients, we performed a randomized, double blind, controlled clinical trial. Twenty-four hemodialysis patients were randomly assigned to receive either three 20 mcg or the recommended three 40 mcg intramuscular injections over 6 months. In addition, 19 normal volunteers also received three 20 mcg doses of the vaccine. The presence of Anti-HBs was determined qualitatively and quantitatively. Non-uremic subjects seroconverted more frequently than did either of the dialysis patient groups. Doubling the individual doses of vaccine did not improve the response of the dialysis patients. We conclude that the response to the vaccine is not diminished when dialysis patients are given half the recommended dose of the vaccine and that the cost of vaccinating this high-risk population could be substantially reduced.

Serovar determination of Chlamydia trachomatis isolates by using type-specific monoclonal antibodies.

A panel of 15 monoclonal antibodies was prepared that could distinguish among the 15 serovars of Chlamydia trachomatis. Twelve of these antibodies were specific for a single serovar (A, B, C, D, E, F, G, H, I, K, L1, and L2) and three were specific for two serovars (B/Ba, C/J, and C/L3). Ten of the serovar-specific and two of the bispecific antibodies were shown by immunoblotting to recognize epitopes on the major outer membrane protein. These data provide evidence that such epitopes are closely correlated with and may be partly responsible for the antigenic variations detected by microimmunofluorescence that distinguish the currently recognized serovars. When used in a radioimmunoassay, these antibodies correctly identified the serovar of 17 strains that had been serotyped by the microimmunofluorescence test. In addition, we found that the chlamydial antigen derived from 1.0 cm2 of an infected HeLa cell monolayer was sufficient to allow serotyping with these antibodies. Thus, these monoclonal antibodies may provide a rapid and reliable alternative to mouse immunization and microimmunofluorescence for serotyping of clinical isolates.

Antigenic analysis of the major outer membrane protein of Chlamydia trachomatis with murine monoclonal antibodies.

We prepared monoclonal antibodies against prototype strains of the 15 serovars of Chlamydia trachomatis and identified a subset of reagents that reacted with the major outer membrane protein(s) (MOMPs) of one or more serovars. We then determined the specificities of these anti-MOMP monoclonal antibodies by radioimmunoassay and immunoblot assays against the 15 serovars of C. trachomatis and a C. psittaci strain. We identified 14 different anti-MOMP antibody specificities, including serovar-, several orders of subspecies-, and species-specific determinants. In addition, one antibody reacted with all C. trachomatis serovars and a C. psittaci strain, indicating the presence of a genus-specific epitope on MOMP. Many of the cross-reactions of the subspecies-specific antibodies were similar to those previously reported by use of the microimmunofluorescence technique. We also observed a number of cross-reactions that were unexpected but consistent with data derived by the microimmunofluorescence test. All antibodies, except the genus-specific antibodies, reacted with whole elementary bodies in a radioimmunoassay, suggesting surface exposure of the epitopes. These data confirm and extend previous observations that MOMPs among C. trachomatis serovars are antigenically complex and diverse. In addition, these data indicate that the cross-reaction patterns of some monoclonal antibodies directed against MOMP are similar to those detected by the microimmunofluorescence test and are consistent with the hypothesis that such determinants are contained within MOMPs.

Partial protection against genital reinfection by immunization of guinea-pigs with isolated outer-membrane proteins of the chlamydial agent of guinea-pig inclusion conjunctivitis.

Because partial protection against reinfection is induced by experimental infection in the guinea-pig model of genital chlamydial infection, we sought to induce immunity by immunization. Female guinea-pigs were immunized subcutaneously with the major outer-membrane protein (MOMP) and the 61 kDa cysteine-rich outer-membrane protein (61 kDa) of the agent of guinea-pig inclusion conjunctivitis (GPIC) eluted from SDS-polyacrylamide gels (SDS-MOMP, SDS-61 kDa). Post-immunization sera and secretions contained antibodies to the SDS-purified proteins at high titre as measured by immunoblotting, whereas enzyme immunoassays (EIA) using whole elementary bodies as antigen showed significantly lower titres (P < 0.001). Likewise, blastogenic responses of peripheral mononuclear cells to GPIC elementary bodies were weak. Animals immunized with SDS-MOMP and SDS-61 kDa were fully susceptible to intravaginal challenge, as were control animals immunized with buffer without protein. Another group of animals were immunized with material prepared by extraction of chlamydial outer-membrane complexes with octyl beta-D-glucopyranoside (OGP) and dithiothreitol, which consisted largely of MOMP (OGP-MOMP). In contrast to the SDS-MOMP group, sera and secretions in the OGP-MOMP group showed high titres in EIA, and high titre antibodies to MOMP by immunoblot; however, most animals also had antibodies to 61 kDa, 72 kDa and ca. 84 kDa outer-membrane proteins. OGP-MOMP animals were partially protected against genital challenge as evidenced by low inclusion scores compared to control animals, although duration of infection measured by culture isolation was similar to controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Association of recurrent chlamydial infection with gonorrhea.

To determine whether concurrent gonorrhea reactivates latent chlamydial infection, we studied 74 recurrent chlamydial infections and the effect of concurrent gonorrhea at the recurrent episode on the chlamydial serovar identified. Serotyping of 74 recurrent pairs of chlamydial isolates from patients attending a sexually transmitted diseases clinic indicated that 47.1% (16 of 34) with gonorrhea at the time of recurrence harbored chlamydiae of the same serovar as at the initial infection, while only 22.5% (9 of 40) without gonorrhea had the same serovar (P = .03). The proportion of recurrences by the same serovar in the group without gonorrhea did not differ from the proportion predicted by a random exposure model (22.2% vs. 18.4%, P = .46), while the proportion in the gonorrhea group did (47.1% vs. 19.8%, P less than .0001). The possibility of reinfection did not appear more likely in the group with gonorrhea than in the group without. These observations support the hypothesis that concurrent gonorrhea can reactivate latent chlamydial infection.

Role of cell-mediated immunity in the resolution of secondary chlamydial genital infection in guinea pigs infected with the agent of guinea pig inclusion conjunctivitis.

Guinea pigs which have recovered from a genital infection with the agent of guinea pig inclusion conjunctivitis demonstrate strong immunity to reinfection for a short period of time but then become susceptible to reinfection. The secondary infection is markedly shortened in duration and decreased in intensity. Previous studies have indicated an important role for humoral immunity in resistance to and in recovery from reinfection. However, the contribution of cell-mediated immunity to immunity toward or recovery from a secondary infection is not clear. Guinea pigs were infected in the genital tract with guinea pig inclusion conjunctivitis and were challenged at either 30 or 75 days after the primary infection. Prior to challenge, one group of animals were injected with rabbit anti-guinea pig thymocyte serum (ATS) while control groups received either normal rabbit serum or no treatment. Treatment was continued daily for the course of the experiment. On day 30, ATS-treated guinea pigs had a slightly higher rate of reinfection, and generally the infection persisted longer than in controls. On day 75, all animals became reinfected upon challenge, but control animals resolved their infections in 3 to 9 days. In contrast, most ATS-treated animals remained infected throughout the course of the experiment. Although the animals became reinfected, the levels of chlamydiae were much lower than those observed during the primary infection. ATS treatment abrogated T-cell responses, but serum and secretory antibody responses remained normal. Histopathological examination revealed some decrease in mononuclear infiltration of endocervical and uterine tissues in ATS-treated animals. These data indicate that previously infected guinea pigs require both cell-mediated immunity and humoral immunity for resolution of a challenge infection.