Saltzman RW, Albin S, Russo P, Sullivan KE. of up to 40% are typical in high-risk patient populations despite first-line treatment. PcP affects immunosuppressed hosts, with cancer patients and organ transplant recipients accounting for the majority of cases in developed countries (3, 4). Patients receiving immunomodulatory agents and those with preexisting lung disease represent growing patient populations at risk of developing PcP. These factors contributed to an overall increase in the incidence of PcP in England from 2000 to 2010, despite a decline in the number of HIV-associated cases during that time period (3). While effective chemoprophylaxis for PcP exists, half of all PcP cases occur in those prescribed adequate prophylaxis, most commonly a result of noncompliance (5). Another threat to the effectiveness of chemoprophylaxis is the potential for the development of resistance to trimethoprim-sulfamethoxazole, unquestionably our most effective prophylactic and therapeutic agent (6). Mortality rates have changed little over the past few decades, emphasizing the need for additional treatment options. Immunization, passive or active, is a viable approach. Active immunization of children and adults with cancer against bacterial and viral pathogens during the initial phases of chemotherapy has been shown to protect them through periods of immunosuppression (7,C9). is an attractive target for vaccine-based prevention, since patient populations at risk for PcP can often be identified prior to patients becoming immunosuppressed. Active immunization with whole organisms is uniformly protective in animal models of PcP (10,C12). However, the antigenic profile of infecting each host is so distinct from that of infecting any other host species that cross-protective immunity is not induced. For example, immunization of mice with mouse-derived (fails to protect (13). The inability to cultivate the organism is a further impediment to vaccine development. Indomethacin (Indocid, Indocin) An alternative approach is to use molecular techniques to develop a subunit vaccine, especially one that contains cross-reactive epitopes. Such antigens are rare but do exist (13, 14). Thus far, the efficacy of subunit vaccines for has not matched that observed with whole-cell vaccination. We previously identified a protective monoclonal antibody (MAb), 4F11, that is cross-reactive with other species, including (13). Active immunization with a 142-amino-acid polypeptide (A12) that contains a 4F11 epitope elicits a protective response, decreasing organism burden and lung inflammation (15). We have now isolated and partially characterized the full-length cDNA from which the A12 C-terminal polypeptide was derived. On the basis of the findings described Indomethacin (Indocid, Indocin) herein, we suggest the name cross-reactive antigen 1 (Pca1) for this molecule. Here, we show that active immunization with the N-terminal half of Pca1 protected against infection in a CD4+ T cell-depleted mouse model of PcP. Furthermore, antibody generated from the immunization of mice with this protein also recognizes epitopes on the surface of the human pathogen, 0.0001 by Fisher’s exact test). The proportion of mice protected by Pca1 immunization was statistically indistinguishable from the proportion Indomethacin (Indocid, Indocin) protected by whole-cell immunization (Table 1). These results were confirmed by examining the lung homogenates after silver staining to identify cysts. Furthermore, PCR for the multicopy glycoprotein A (gpA) gene failed to detect any target DNA in lung samples from protected mice (data not shown). The finding of reduced organism burden compared to that in experimental controls in the few mice immunized with Pca1 but not completely protected may be an demonstration of dose-dependent response to immunization (Fig. 1A). Although not statistically significant, likely due to sample size, this provides additional evidence for vaccine efficacy. TABLE 1 Summary of protection by Pca1 immunization(positive control) 0.0001 for mice immunized with Pca1 or whole compared to the negative-control value by Fisher’s exact test. Open in FLJ13165 a separate window FIG 1 Pca1 immunization reduces organism burden in a dose-dependent trend. (A) Mice immunized with Pca1 fusion protein and with detected by qPCR (= 37) (triangles) had reduced (Pc) organism burdens compared to mice immunized with the fusion partner (= 10) (circles) or an irrelevant protein (= 18) (squares). Data points represent log transformation of qPCR, with the limit of assay detection marked by the dashed line. Data from six experiments are shown, and the data are color coded. (B) Increasing doses of Pca1 immunization resulted in an increased number of mice protected from infection. Values that are significantly different from the value for the negative control are indicated by asterisks as follows: **, 0.01; *, 0.05. Data from two pooled experiments are shown. To determine a threshold dose, mice were immunized with different doses of Pca1. As expected, the efficacy of Pca1 was dependent on.
Saltzman RW, Albin S, Russo P, Sullivan KE