The BCL2 protooncogene encodes an inner mitochondrial membrane protein that blocks programmed cell death. BCL2 was isolated from the chromosomal breakpoint of follicular B-cell lymphoma. Transgenic mice that overexpress BCL2 display extended survival of resting B cells. In this study we use a monospecific anti-human BCL2 antibody to define the distribution of BCL2 protein within organized tissues. BCL2 is restricted within germinal centers to the follicular mantle and to portions of the light zone implicated in the selection and maintenance of plasma cells and memory B cells. BCL2 is present in the surviving T cells in the thymic medulla. All hematopoietic lineages that derive from a renewing stem cell also display BCL2. A limited number of nonlymphoid tissues demonstrate BCL2 and can be grouped as (i) glandular epithelium in which hormones or growth factors regulate hyperplasia and involution, (i) complex differentiating epithelium such as skin and intestine characterized by long-lived stem cells, and (iii) long-lived postmitotic cells such as neurons.Within these tissues that demonstrate apoptotic cell turnover, BCL2 is often topographically restricted to long-lived or proliferating cell zones. BCL2's function as an antidote to apoptosis may confer longevity to progenitor and effector cells in these tissues.

In mice deficient in either lymphotoxin-alpha (LT-alpha) or the type I tumor necrosis factor (TNF) receptor, but not the type II TNF receptor, germinal centers failed to develop in peripheral lymphoid organs. Germinal center formation was restored in LT-alpha-deficient mice by transplantation of normal bone marrow, indicating that the LT-alpha-expressing cells required to establish this lymphoid structure are derived from bone marrow.

Pneumococcal surface protein A (PspA), a cross-reactive protein expressed by all pneumococci, is known to elicit an antibody in animals that can passively protect mice from infection with Streptococcus pneumoniae. A phase I trial with recombinant PspA showed the protein to be immunogenic in humans. Pre- and postimmune serum samples from this trial were examined, and human antibody to PspA could protect mice from pneumococcal infection. The serum samples of subjects immunized twice with 125 microg of PspA had >100 times as much antibody per milliliter as was required to consistently protect mice from fatal infection (1.3 microg/dose). At least 98% of PspAs fall into PspA sequence/serologic families 1 or 2. Human antibodies elicited by a family 1 PspA protected against infection with S. pneumoniae expressing either family 1 or 2 PspAs and with strains of all 3 capsular types tested: 3, 6A, and 6B. These studies suggest that PspA may have efficacy as a human vaccine.

Streptococcus pneumoniae (pneumococcus) is a major human pathogen producing structurally diverse capsular polysaccharides. Widespread use of highly successful pneumococcal conjugate vaccines (PCVs) targeting pneumococcal capsules has greatly reduced infections by the vaccine types but increased infections by nonvaccine serotypes. Herein, we report a new and the 100th capsule type, named serotype 10D, by determining its unique chemical structure and biosynthetic roles of all capsule synthesis locus (cps) genes. The name 10D reflects its serologic cross-reaction with serotype 10A and appearance of cross-opsonic antibodies in response to immunization with 10A polysaccharide in a 23-valent pneumococcal vaccine. Genetic analysis showed that 10D cps has three large regions syntenic to and highly homologous with cps loci from serotype 6C, serotype 39, and an oral streptococcus strain (S. mitis SK145). The 10D cps region syntenic to SK145 is about 6 kb and has a short gene fragment of wciNα at the 5′ end. The presence of this nonfunctional wciNα fragment provides compelling evidence for a recent interspecies genetic transfer from oral streptococcus to pneumococcus. Since oral streptococci have a large repertoire of cps loci, widespread PCV usage could facilitate the appearance of novel serotypes through interspecies recombination. IMPORTANCE The polysaccharide capsule is essential for the pathogenicity of pneumococcus, which is responsible for millions of deaths worldwide each year. Currently available pneumococcal vaccines are designed to elicit antibodies to the capsule polysaccharides of the pneumococcal isolates commonly causing diseases, and the antibodies provide protection only against the pneumococcus expressing the vaccine-targeted capsules. Since pneumococci can produce different capsule polysaccharides and therefore reduce vaccine effectiveness, it is important to track the appearance of novel pneumococcal capsule types and how these new capsules are created. Herein, we describe a new and the 100th pneumococcal capsule type with unique chemical and serological properties. The capsule type was named 10D for its serologic similarity to 10A. Genetic studies provide strong evidence that pneumococcus created 10D capsule polysaccharide by capturing a large genetic fragment from an oral streptococcus. Such interspecies genetic exchanges could greatly increase diversity of pneumococcal capsules and complicate serotype shifts.

ABSTRACTAlthough virulence ofStreptococcus pneumoniaeis associated with its capsule, some pathogenicS. pneumoniaeisolates lack capsules and are serologically nontypeable (NT). We obtained 64 isolates that were identified as NT “pneumococci” (i.e., bacteria satisfying the conventional definition but without the multilocus sequence typing [MLST]-based definition ofS. pneumoniae) by the traditional criteria. All 64 were optochin sensitive and hadlytA, and 63 hadply. Twelve isolates hadcpsA, suggesting the presence of a conventional but defective capsular polysaccharide synthesis (cps) locus. The 52cpsA-negative isolates could be divided into three null capsule clades (NCC) based onaliC(aliB-like ORF1),aliD(aliB-like ORF2), and our newly discovered gene,pspK, in theircpsloci.pspKencodes a protein with a long alpha-helical region containing an LPxTG motif and a YPT motif known to bind human pIgR. There were nine isolates in NCC1 (pspK+but negative foraliCandaliD), 32 isolates in NCC2 (aliC+aliD+but negative forpspK), and 11 in NCC3 (aliD+but negative foraliCandpspK). Among 52cpsA-negative isolates, 41 were identified asS. pneumoniaeby MLST analysis. All NCC1 and most NCC2 isolates wereS. pneumoniae, whereas all nine NCC3 and two NCC2 isolates were notS. pneumoniae. Several NCC1 and NCC2 isolates from multiple individuals had identical MLST andcpsregions, showing that unencapsulatedS. pneumoniaecan be infectious among humans. Furthermore, NCC1 and NCC2S. pneumoniaeisolates could colonize mice as well as encapsulatedS. pneumoniae, althoughS. pneumoniaewith an artificially disruptedcpslocus did not. Moreover, an NCC1 isolate withpspKdeletion did not colonize mice, suggesting thatpspKis critical for colonization. Thus, PspK may provide pneumococci a means of surviving in the nasopharynx without capsule.IMPORTANCEThe presence of a capsule is critical for many pathogenic bacteria, including pneumococci. Reflecting the pathogenic importance of the pneumococcal capsule, pneumococcal vaccines are designed to elicit anticapsule antibodies. Additional evidence for the pathogenic importance of the pneumococcal capsule is the fact that in pneumococci all the genes necessary for capsule production are together in one genetic locus, which is called thecpslocus. However, there are occasional pathogenic pneumococci without capsules, and how they survive in the host without the capsule is unknown. Here, we show that in these acapsular pneumococci, thecpsloci have been replaced with various novel genes and they can colonize mouse nasopharynges as well as capsulated pneumococci. Since the genes that replace thecpsloci are likely to be important in host survival, they may show new and/or alternative capsule-independent survival mechanisms used by pneumococci.