Palivizumab is highly effective in suppressing respiratory syncytial virus in an immunosuppressed animal model.

Respiratory syncytial virus (RSV) is widely recognized as a leading cause of pneumonia, with substantial mortality, in bone marrow transplant recipients. We tested the efficacy of a systemic monoclonal antibody (MAB) preparation possessing a high titer of anti-RSV neutralizing antibody, palivizumab (Synagis) for prophylaxis and therapy of RSV infection in cytoxan (CY) immunosuppressed cotton rats, a model in which the efficacy of a polyclonal anti-RSV product (Respigam) has been demonstrated. Both prophylaxis and therapy with this MAB were highly effective in reducing pulmonary viral replication. However, multiple sequential therapeutic doses of MAB were necessary to control rebound viral replication in continually suppressed animals.

Contribution of the human parainfluenza virus type 3 HN-receptor interaction to pathogenesis in vivo.

The envelope of human parainfluenza virus type 3 (HPF3) contains two viral glycoproteins, the hemagglutinin-neuraminidase (HN) protein and the fusion (F) protein. In a previous study, highly fusogenic variant HPF3 viruses were isolated, including two, C-0 and C-22, that exhibit increased avidity for sialic acid receptors due to single amino acid changes in the HN protein and one, C-28, that has decreased neuraminidase activity relative to that of the wild type (wt) and is delayed in the release of virus particles into the supernatant fluid. These variants form very large plaques and destroy a cell monolayer more rapidly than does wt HPF3 in cell culture. These variant viruses allowed us to formulate hypotheses about the roles of HN in pathogenesis. We investigated the behavior of wt HPF3 and the three variant viruses in the cotton rat model. In the cotton rat, there was no delayed clearance of any of the variant viruses compared to that of the wt. The variant plaque morphology was preserved in vivo, and there was no reversion to the wt phenotype in the infected animals. In spite of a slight advantage of wt virus in viral titer, there were no differences in the severities of peribronchiolitis between wt viruses and the variants. However, there were marked differences in severities in alveolitis and interstitial pneumonitis when each of the three variants was compared to the wt, with the variants causing enhanced disease. Thus, despite similar or lower viral titers and similar clearance rates, the variants caused more extensive disease in the lung. The results show that mutations in HN conferring altered fusion properties in cell culture also confer striking differences in the ability of HPF3 to cause extensive disease in the cotton rat lung and that this effect is dissociated from any effect on viral replication.

Serious infections of the central nervous system: encephalitis, meningitis, and brain abscess.

Central nervous system infections in adolescents range from the diffuse cerebritis of encephalitis to the regional inflammation of meningitis, and very focal disease of brain abscess. Clinical presentations reflect this wide spectrum, with encephalitis primarily characterized by altered mental status, meningitis by fever, headache, and neck stiffness, and brain abscess manifesting localizing findings. Encephalitis and viral meningitis are frequently caused by the seasonal enteroviruses and arboviruses, while most adolescent bacterial meningitis is due to Neisseria meningitidis and Streptococcus pneumoniae. The microbiology of brain abscess reflects underlying host risk factors. Gram-positive cocci are seen in patients with congenital heart disease, while respiratory flora including anaerobes are associated with sinus or otic disease. Lumbar puncture to characterize and culture the CSF remains the optimal test for the diagnosis and management of encephalitis and meningitis, while CT-guided needle biopsy may be both diagnostic and therapeutic for brain abscesses. New diagnostic tests include the use of PCR. A variety of safe and effective treatment regimens exists for most bacterial infections as well as for some herpesvirus infections. New vaccines are under study to further control bacterial meningitis.

Enhanced pulmonary pathology in cotton rats upon challenge after immunization with inactivated parainfluenza virus 3 vaccines.

Vaccine-induced potentiation was studied in cotton rats immunized with formalin-inactivated human parainfluenza type 3, ultraviolet light-inactivated virus, or infection with live virus. Immunized animals and unimmunized controls were later challenged by intranasal inoculation of live virus and evaluated for pulmonary pathology 4 days later. Animals immunized with either of the inactivated vaccines developed marked peribronchiolitis, perivasculitis, and an alveolar cellular infiltration much more severe than seen in animals infected previously, or in unmanipulated but challenged animals. Disease enhancement after immunization with killed virus is thus a characteristic of a member of each of three genera of the family, Paramyxoviridae, and is not restricted to immunization with formalin-inactivated virus.

Effectiveness of RSVIG prophylaxis and therapy of respiratory syncytial virus in an immunosuppressed animal model.

Respiratory syncytial virus (RSV) has emerged as a leading cause of pneumonia, with high mortality, in bone marrow transplant (BMT) recipients, as well as in other profoundly immunocompromised patients, such as myelosuppressed adults with leukemia. We tested the efficacy of immunoglobulin with high anti-RSV neutralizing antibody levels (RSVIG) for prophylaxis and therapy of RSV infection in cotton rats undergoing prolonged immunosuppression with cyclophosphamide. These animals experience persistent infection, a model which is similar to the disease seen in post-BMT humans. Both prophylaxis and therapy reduced pulmonary viral replication over 500-fold to nearly undetectable levels. In animals receiving continual immunosuppression, the use of multiple therapeutic doses of RSVIG was able to prevent rebound viral replication, though virus was not completely eliminated.

Inactivation of respiratory syncytial virus by generic hand dishwashing detergents and antibacterial hand soaps.

In an in-vitro test, generic liquid hand dishwashing detergents were as much as 100-fold more effective than proprietary antibacterial soaps in inactivating respiratory syncytial virus (RSV). The use of such detergents for hand washing during annual RSV epidemics, or the incorporation of their antiviral components into antibacterial soaps might be considered to limit nosocomial spread.

Eradication of Cryptosporidium in a child undergoing maintenance chemotherapy for leukemia using high dose azithromycin therapy.

PURPOSE: To describe a case of severe diarrhea caused by Cryptosporidium in a patient undergoing maintenance chemotherapy. Important aspects of disease caused by Cryptosporidium, including diagnosis and treatment, are also reviewed. METHODS AND RESULTS: A 4-year-old boy with acute lymphoblastic anemia in remission had a prolonged course of diarrhea and wasting. C. parvum was identified in the gastrointestinal tract by biopsy and in the stool using modified acid fast staining. Improvement in the stool consistency was noted after 3 days of therapy with azithromycin, and, after 14 days of therapy, Cryptosporidium oocysts could no longer be identified in the stool. CONCLUSIONS: C. parvum should be considered in all immunocompromised patients with severe or prolonged diarrhea, especially if there is no blood or leukocytes in the stool. Because Cryptosporidium is not always tested for in a routine ova and parasite examination, the lab should be notified if it is in the differential diagnosis. Azithromycin therapy may prove beneficial in the treatment of intestinal Cryptosporidium in immunocompromised individuals.

Immunoprophylaxis of group B respiratory syncytial virus infection in cotton rats.

Two antigenic groups of respiratory syncytial virus (RSV) have been identified: A (RSV/A) and B (RSV/B). Topical administration of human IgG screened for high titers of antibody to RSV/A (RSVIg) is protective against RSV/A infection in the cotton rat model. The study attempted to determine if topical RSVIg would also be protective against RSV/B. Cotton rats were pretreated intranasally with RSVIg or with monospecific antiserum obtained from animals previously infected with RSV/A or RSV/B (day 0), challenged intranasally with RSV/A or RSV/B (day 1), and sacrificed for virus titration (day 5). Cotton rat antiserum to RSV/B protected against RSV/A and RSV/B, while antiserum to RSV/A protected only against RSV/A. RSVIg, although prepared on the basis of activity against RSV/A, was also protective against RSV/B.

Prospects for vaccines during pregnancy and in the newborn period.

Maternal and neonatal vaccine strategies have been used successfully throughout the world for many years. In addition, new vaccine technologies are likely to overcome the scientific issues related to safety, immunogenicity, and efficacy of neonatal vaccines. There are obvious advantages to maternal or neonatal immunizations. Immunologic protection in the first 8 to 12 weeks of life occurs only by passive immunization with IgG or by actively immunizing the mother or newborn baby (or by doing both as in hepatitis B). Although mothers may have protective levels of antibody to many pathogens, only active immunization of mothers or babies ensures that reliable protective levels are abundant in the neonate. Also, premature infants receive lower levels of passive maternal antibody and may not be protected regardless of maternal levels of specific antibodies. Thus, there is a particular need for development of neonatal immunization strategies in these babies. There is another value of neonatal immunization in the newborn period and that is compliance. In all areas of the world there is often poor compliance with infant vaccination policies. The newborn period offers the earliest possible time at which many infants can be reliably started on their immunization program. In many parts of the developing world this is already being put into practice for selected vaccines. Many of the vaccines currently used or under consideration for maternal or neonatal immunization are listed in Table 4. What are the impediments to progress in this area? For neonatal immunization there are several issues; however, the main impediment is providing vaccines that are safe, provide rapid protection, and are highly immunogenic if given to babies with an immature immune system. As reviewed in this article, current vaccines are safely and effectively used in newborn babies. As new vaccine technologies improve immunogenicity and allow mucosal delivery, the routine childhood immunization may move into the newborn period. Maternal immunization is a more complex issue. Currently available vaccines and new conjugate vaccines are immunogenic in women, and there is no convincing evidence of risk to the fetus by immunizing pregnant women with bacterial vaccines, toxoids, or inactive viral vaccines. The reduction in anti-PRP antibody in mothers receiving PRP-T conjugate vaccine within 4 weeks of a tetanus shot, however, demonstrates the necessity to demonstrate immunogenicity, safety, and efficacy of maternal immunization strategies before universal implementation. To hasten the availability and utilization of maternal vaccines, an increasing emphasis on research with increased funding should focus on vaccine development specifically to provide protection for infants in the first weeks of life (both maternal and neonatal vaccine strategies). The pharmaceutical industry, physicians, and the FDA must work together to develop guidelines for studies that will efficiently analyze the safety and efficacy of candidate vaccines. Liability issues also must be addressed so that physicians and the pharmaceutical industry can become comfortable with producing and employing vaccines that will protect babies at the earliest possible time.

Prevention and treatment recommendations for respiratory syncytial virus infection. Background and clinical experience 40 years after discovery.

Though 40 years have passed since its discovery, respiratory syncytial virus (RSV), one of the most ubiquitous viruses known, continues to evade most of our efforts to prevent or treat the clinical disease it causes. Long recognised as the most common cause of lower respiratory tract infections in virtually all children in the first 2 years of life, it has been increasingly recognised as a cause of more serious disease in several 'high risk' populations. These populations include infants with cardiac or pulmonary disease and infants and adults with immunodeficiencies, particularly those undergoing bone marrow transplantation. Early attempts to immunise children with a simple formalin-inactivated vaccine led to severe disease in vaccinated children who subsequently were infected with RSV from the community. Other vaccine constructs have failed for a variety of reasons, although surface glycoprotein subunit vaccines may hold promise. For years, ribavirin, a synthetic nucleoside analogue administered by constant aerosol, has been felt by many to lead to more rapid improvement in clinical disease caused by RSV, but it is still unclear whether its benefits are truly significant. An intravenous immunoglobulin product prepared from donors screened for the presence of high titres of RSV neutralising antibody (known as RSVIG) appears to be well tolerated and relatively effective in protecting high-risk infants against serious RSV disease, although therapeutic use has proven less dramatic. At least one monoclonal antibody undergoing current testing may prove easier to use in similar immunoprophylactic use. Results on the use of corticosteroids as supportive therapy have not been conclusive. In short, RSV will continue to be a challenge for clinicians and researchers well into the next century.

Semi-permissive replication and functional aspects of the immune response in a cotton rat model of human parainfluenza virus type 3 infection.

A cotton rat (Sigmodon fulviventer) model of human parainfluenza virus type 3 (HPIV-3) infection was used to study patterns of HPIV-3 replication in naive and immune hosts. Growth curves revealed that nasal and pulmonary tissues of naive animals were semi-permissive for virus replication, with amounts of progeny virus proportional to inoculating doses. In naive animals there was a total eclipse in nasal tissues beginning 4 h after inoculation. By contrast, there was only partial eclipse of virus in pulmonary tissues, most pronounced at 1 h after inoculation. Immune animals demonstrated a delayed eclipse in pulmonary tissues upon rechallenge. Infection with very low doses of HPIV-3 induced complete protection against high-dose challenge in the absence of systemic neutralizing antibody, suggesting a significant role for other systemic or local immune effectors.

Delayed-type hypersensitivity skin testing in human immunodeficiency virus-infected pediatric patients.

OBJECTIVE: To evaluate whether pediatric patients infected with human immunodeficiency virus (HIV) can mount appropriate delayed-type hypersensitivity (DTH) skin responses to recall antigens and whether these responses can be correlated with clinical or immunologic parameters. DESIGN: Prospective evaluation of DTH responses in HIV-infected children. Uninfected children born to HIV-infected mothers served as control subjects. Antigens used for yearly DTH testing included Candida albicans (1:100, 1:10); mumps virus; Trichophyton; purified protein derivative of tuberculin; and tetanus toxoid (1:100, 1:10). At the time of each DTH test, patients were staged according to two Centers for Disease Control and Prevention pediatric HIV classification systems, and T-cell subsets were obtained. RESULTS: Twenty-seven HIV-infected patients with a median age at entry of 74.1 (range, 12 to 156) months were followed. Forty-four DTH skin tests in 21 symptom-free HIV-infected patients (PI) and 18 tests in 10 HIV-infected patients with symptoms (P2), as well as 43 DTH skin tests in 18 patients who had either mild or moderate clinical symptoms or immunosuppression and 19 tests in 13 patients with severe symptoms or immunosuppression, were evaluated. Sixteen DTH skin tests were performed in 14 uninfected patients. HIV-infected patients tended to have fewer DTH responses to antigens and of smaller size than did uninfected patients. When controlled for age, few differences in DTH responsiveness were seen between HIV-infected and uninfected patients. Anergy was associated with symptomatic disease, evidence of advanced clinical or immunologic disease, and low CD4+ percentages (p <0.05). CONCLUSIONS: HIV-infected children are able to mount antigen-specific cell-mediated immune responses that are qualitatively similar to those of age-matched control subjects. Loss of DTH responsiveness correlates with both clinical and immunologic evidence of HIV disease progression.

Unilateral nasal infection of cotton rats with respiratory syncytial virus allows assessment of local and systemic immunity.

An in vivo model for the study of local and systemic effectors of immunity to respiratory syncytial virus (RSV) is described. Cotton rats (Sigmodon fulviventer) inoculated in one nostril with a small volume (2 microliters) of virus suspension contracted a unilateral nasal infection which did not extend to the contralateral nasal turbinates, nor to the lungs. Immunity to subsequent RSV challenge could be induced by small priming doses ( < 10 p.f.u. per animal), but was dependent upon viral replication, as virus inactivated by UV light was not immunogenic. Immunity occurred in the absence of detectable neutralizing serum antibody. The onset of resistance to viral challenge occurred simultaneously in ipsilateral nasal, contralateral nasal and pulmonary tissues. However, low levels of transient viral replication occurred in contralateral nasal turbinates and in lungs following virus challenge, thus indicating that local components of immunity acting at the ipsilateral site of infection were more effective than systemic components acting at the other sites. Further evidence is provided to suggest that three types of immunological effectors - local, persistent, systemic and transient systemic - participate in the immune response to RSV infection.

Topical immunoglobulin is an effective therapy for parainfluenza type 3 in a cotton rat model.

A cotton rat model was used to test the efficacy of topical immunotherapy against parainfluenza type 3 (PIV3) infection. On day 3 after experimental infection with 10(5.5) pfu of PIV3, animals were treated with 2-fold dilutions of convalescent cotton rat serum or with one of two purified human immunoglobulin preparations; all three had moderate titers of anti-PIV3 neutralizing antibody (range, 1:200-1:1000). Therapy with high concentrations of all three preparations resulted in significant reductions of > or = 2 logs (> or = 100-fold) of pulmonary virus titers compared with titers for control animals. Little or no reduction in virus titers were seen in nasal tissues.

A cotton rat model of effectors of immunity to respiratory syncytial virus other than serum antibody.

A model for studying effectors of immunity to respiratory syncytial virus (RSV) was developed. Paris of inbred cotton rats (Sigmodon hispidus) were joined surgically using the technique of parabiosis. One week later, one animal of each pair was primed intranasally with a small volume of RSV suspension. Fourteen days after priming, both animals of each pair were bled for determination of serum neutralizing antibody titers, and challenged intranasally with a standard dose of RSV suspension. Single, unprimed cotton rats were challenged concomitantly and served as controls. Four days after challenge, all animals were sacrificed for virus titration of nasal tissues and lungs. Parabiosed cotton rats were surgically separated at varying intervals between priming and challenge (days 7, 9, 12, or 14 after priming) or were kept joined until sacrificed (day 18). Significant transfer of nasal and pulmonary immunity from primed to unprimed parabionts began 9 days after priming, gradually increasing through 18 days. Resistance to RSV challenge in spite of low levels of serum neutralizing antibody suggests that non-antibody immunologic mediators were responsible for the transferred immunity. Evidence is presented for three broad categories of RSV immunologic effectors: systemic, local with a transient systemic phase, and local without a systemic phase. These categories are now amenable to further study using the described model.

Systemic immunoprophylaxis of nasal respiratory syncytial virus infection in cotton rats.

The cotton rat model was used to test whether systemically administered immunoglobulin could protect nasal tissues against low challenge doses of respiratory syncytial virus (RSV). Animals were pretreated by intraperitoneal injection of human immunoglobulin with moderate (1:2226) or high (1:15,000) neutralizing antibody titers to RSV (day 0), challenged intranasally with RSV Long at doses ranging from 10(1) to 10(5) pfu (day 1), and sacrificed for virus titration (day 5). Pretreatment with moderate-titer immunoglobulin effected complete or near complete nasal protection against low to moderate (10(1)-10(3) pfu) RSV challenge doses and a significant reduction in nasal RSV titers at high (10(4)-10(5) pfu) challenge doses. Pretreatment with high-titer immunoglobulin effected near complete nasal protection at an RSV challenge dose of 10(3) pfu and highly significant and significant reductions in nasal RSV titers at challenge doses of 10(4) and 10(5) pfu, respectively. Immunoprophylaxis effected complete or near complete pulmonary protection at all RSV challenge doses.

Staphylococcus aureus meningitis associated with pyogenic infection of the sacroiliac joint.

Although we have reported the first case of Staphylococcus aureus meningitis due to pyogenic arthritis of the sacroiliac joint, this finding is actually not surprising, given the strong association between this form of meningitis and underlying bone, joint, and soft tissue infections. The physician faced with a case of meningitis due to S aureus in a patient without a history of trauma or neurosurgical manipulation must do a prompt and thorough search for underlying infectious conditions. In the case of sacroiliitis in particular, a high index of suspicion needs to be maintained, given the difficulties and delays in diagnosis associated with this infection. Radionuclide scanning with 99mTc or 67Ga is usually helpful in the early confirmation of this condition, the presence of which may be suspected on the basis of thorough physical examination.

Immunotherapy of respiratory syncytial virus infection in cotton rats (Sigmodon fulviventer) using IgG in a small-particle aerosol.

To determine whether aerosolized IgG can be used effectively in the treatment of respiratory syncytial virus (RSV) infections, cotton rats were infected intranasally with RSV and treated 3 days later with human IgG containing anti-RSV antibodies delivered in a small-particle aerosol. Pulmonary histology and virus titers were determined 24 h after IgG treatment. A single 15-min exposure to aerosolized IgG did not exacerbate pulmonary pathology and effected a 50-fold reduction in pulmonary virus titer (2.95 vs. 4.67 log10 geometric mean pfu/g for untreated controls, P < .001), which was comparable to that effected by intranasally instilled IgG (50 mg/kg) (3.24 vs. 4.67 log10 geometric mean pfu/g for controls, P < .001). A 15-min exposure to aerosolized ribavirin (20 mg/mL) was not effective in reducing pulmonary virus. This study suggests that aerosolized IgG could be useful in the treatment of RSV lower respiratory tract infections and that it compares favorably with ribavirin.