Helen L. Lucia

Activity of (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) against guinea pig cytomegalovirus infection in cultured cells and in guinea pigs

(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine, HPMPC, and two HPMPC-related nucleoside analogs, (S)-9-(3-hydroxy-2-phosphonylmethoxypropyl)adenine, HPMPA, and (2-phosphonylmethoxyethyl)guanine, PMEG, were evaluated for their antiviral activities against guinea pig cytomegalovirus (GPCMV) infection in guinea pig embryo (GPE) cells and human cytomegalovirus (HCMV) infection in human diploid fibroblast (MRC-5) cells. DHPG, 9-(1,3-dihydroxy-2-propoxymethyl)guanine, was used for comparison. The antiviral activity of HPMPC against GPCMV infection in vivo and its toxicity to Hartley guinea pigs were also evaluated. The 50% antiviral effective doses (ED50) of HPMPC, HPMPA, PMEG and DHPG against GPCMV infection in GPE cells were 0.22, 1.4, 0.07 and 62 microM, respectively; and against HCMV infection in MRC-5 cells, the ED50s were 0.51, 0.72, 0.01 and 17.5 microM, respectively. Their cytotoxic doses (CyD50) in GPE replicating cells were 84, 35, 1.4 and 700 microM, respectively and in MRC-5 cells were approximately 114, 31, 0.86 and 750 microM, respectively. Based on their calculated therapeutic indexes, HPMPC was the most potent and selective of the four compounds tested. In vivo, during acute infection, the spleen indexes of all infected animals that were treated with 1.25 to 5.0 mg/kg/day of HPMPC for 5 days were significantly reduced as compared with sham-treated animals. Virus infectivity titers in blood and various tissues of infected animals treated with HPMPC, 2.5 or 1.25 mg/kg/day were not significantly lower than those of the infected, sham-treated animals; with 5 mg/kg/day, infectivity titers in the blood, spleen, and salivary gland were significantly lower in HPMPC-treated than in sham-treated animals. However, HPMPC was toxic to guinea pigs especially at doses of 5 to 10 mg/kg/day. These data showed that HPMPC was highly active and selective in cultured guinea pig cells and human fibroblast cells against CMV infection but did not effectively inhibit GPCMV infection in guinea pigs at minimum toxic concentrations.

Arenavirus infection in the guinea pig model: Antiviral therapy with recombinant interferon-α, the immunomodulator CL246, 738 and ribavirin

Human arenaviral infections have a high mortality, and are dangerous to work with in the laboratory. There is a need for good antiviral agents to treat these infections. Pichinde virus infection of the inbred strain 13 guinea pig is a relatively safe, good animal model for human arenavirus infections. Mortality is consistently 100% between days 12 and 25 (mean 14.8) days after infection. When infected animals were treated with recombinant human interferon alpha A, or with CL246,783, an immunomodulator known to induce interferon, no beneficial effect was noted. When animals received ribavirin, 25 mg/kg/day for the first 14 days of infection, the course of infection was prolonged, with death occurring a mean of 22.5 days after infection. If ribavirin was administered for 28 days, mortality was reduced to 25%, with those animals dying a mean of 21.0 days after infection. These results confirm the studies that indicate that ribavirin is a useful agent for treating arenaviral infections. However, treatment with this agent must be prolonged. They also demonstrate the potential usefulness of Pichinde virus infection in strain 13 guinea pigs as an animal model of human disease.

Effect of Acyclovir and Phosphonoformate on Cytomegalovirus Infection in Guinea Pigs

Adult Hartley guinea pigs infected with guinea pig cytomegalovirus (CMV) develop a mononucleosis syndrome with a brief viremia, splenomegaly, lymphadenopathy, and peripheral lymphocytosis with circulating atypical lymphocytes. The present study used this experimental model to evaluate in vivo the therapeutic efficacy of acyclovir (ACV) and phosphonoformate (PFA) during CMV infection. Guinea pigs were treated with ACV or PFA from day 3 to day 7 postinoculation. The course of the mononucleosis syndrome and the spread of virus in various tissues were similar in drug- and sham-treated infected guinea pigs. Infected animals treated with ACV or PFA developed disseminated CMV disease with severe interstitial pneumonia, whereas sham-treated infected and drug-treated noninfected animals did not. In addition, mortality rates in infected animals treated with ACV were significantly higher than those in sham-treated animals. Furthermore, the normal lymphoproliferative response to CMV infection appeared to be reduced in ACV-treated as compared to sham-treated animals, with fewer peripheral lymphocytes, less lymphoid tissue in the spleen and lymph nodes, and less mononuclear inflammation around the inclusion-containing cells of the liver and salivary gland. These results show that ACV and PFA are not useful in the treatment of CMV infection in guinea pigs but instead may have harmful effects.

Effects of Cyclosporine on the Pathogenesis of Primary Cytomegalovirus Infection in the Guinea Pig

The effects of cyclosporin A (CsA) upon the pathogenesis of primary cytomegalovirus (CMV) infection were investigated. Hartley and strain 2 guinea pigs were inoculated subcutaneously on day 0 with 10(4) TCD50 of virulent, salivary-gland-passaged guinea pig CMV and received oral CsA (20 mg/kg/day) for 14 days. CMV-infected, CsA-treated animals lost approximately 20% of their total body weight in 14 days and had more than twice the rate of CMV isolation from internal organs when compared with untreated controls, despite similar rates of viremia. Internal organs of CsA-treated animals demonstrated widespread viral inclusions and minimal inflammatory response to the presence of CMV-infected cells. The mean change in peripheral blood lymphocyte values for CMV-infected, CsA-treated Hartley guinea pigs was -2,867 +/- 2,955 (mean +/- SD) lymphocytes/microliters as compared to +10,933 +/- 7,583 in CMV-infected, untreated controls (p less than 0.01). In the guinea pig model, CsA administration had adverse effects upon the pathogenesis of primary CMV infection.

Group A Streptococcal Rapid Test Antigen Detection After 18-24 Hours of Penicillin Therapy

We studied 29 children, aged 19 months to 16 years, prior to and after 18-24 hours of oral penicillin therapy to confirm the rapid disappearance of detectable pharyngeal antigen and to determine whether the antigen detectable by commercially available kits was excreted into the urine. Patients were recruited based on the presence of pharyngitis, no antibiotic therapy in the preceding 2 weeks, and a positive latex agglutination (LA) for group A beta hemolytic streptococci (GABHS) antigen on pharyngeal swab. Diagnosis was confirmed by positive GABHS culture on blood agar plates. Twenty-five of these children were also tested for GABHS antigen by enzyme-linked immunoassay (EIA). After 18-24 hours of oral antibiotic therapy, only 10 patients had a positive test for GABHS on throat swab. Five of 29 subjects (17%) remained positive by blood agar plate (BAP) culture, eight of 29 (29%) by LA, and four of 23 (17%) by EIA. GABHS antigen was undetectable by LA or EIA in the urines of any of these patients, either prior to or after initiation of treatment, even in specimens concentrated as high as 100 fold. Clinicians should routinely seek a history of prior antibiotic therapy in assessing pharyngitis. Neither of the kits tested are reasonably accurate for GABHS disease by detection of antigen in the pharynx after partial treatment or in the urine at any time.

Effects of Cyclosporine on Chronic Cytomegalovirus Infection in the Guinea Pig

Following establishment of chronic guinea pig cytomegalovirus (GPCMV) infection, animals received by gavage either cyclosporine (CS), 20-33 mg/kg, or drug vehicle daily for 28 days. At sacrifice the frequency of CMV isolation from tissues of GPCMV-infected animals was 20% for the immunosuppressed group versus 12% for controls (difference, NS). GPCMV isolation rates from lymphoid tissues (thymus, spleen, cervical lymph nodes) of experimental animals was 7 of 69 (10%) vs. 0 of 42 (0%) from controls (p less than 0.05). Although CS immunosuppression was associated with increased rates of GPCMV isolation from lymphoid tissues of chronically infected animals, it was not accompanied by detectable systemic disease.

Effect of cyclosporin A immunosuppression on primary lymphotropic herpesvirus infection in the guinea pig

Female guinea pigs pretreated for 2 days with cyclosporin A (CsA), were then inoculated intranasally (IN) or intraperitoneally (IP) with a lymphotropic herpesvirus (GPHLV) and followed by 4 additional daily doses of CsA. Immunosuppressed animals did not show lymphocytosis and virus infectivity titers in their spleen, cervical lymph node and blood mononuclear cells were lower than those of oil-treated controls. While IN-inoculated CsA-treated animals expressed higher virus infectivity titer in their lungs compared to oil-treated controls, this difference was not seen in the IP-inoculated groups. At histopathology, lymphoid depletion was seen in all CsA-treated animals, but lymphocytic interstitial pneumonia was observed only in the lungs of IN-inoculated CsA-treated guinea pigs. Thus, CsA immunosuppression altered the pathogenesis of primary GPHLV infection with some notable differences attributed to the route of virus inoculation.