Pascale Gueirard

Evidence of Bordetella pertussis infection in adults presenting with persistent cough in a french area with very high whole-cell vaccine coverage.

Although France has had a vaccination program for 40 years, since 1990, an increase in whooping cough cases with parent-infant transmission has been observed. This study prospectively assessed the frequency of Bordetella pertussis infection in adults who consulted general practitioners for a persistent cough without an evident diagnosis. Among 217 patients, 70 (32%) confirmed whooping cough cases were identified. One case was culture positive, 36 were polymerase chain reaction positive, and 40 had increases or decreases of > or =2-fold in anti-pertussis toxin IgG titer between serum samples collected during the acute and convalescent phases. The median duration of cough in confirmed cases was 49 days (range, 13-123 days). Of the patients, 60% reported vaccination, and 33% reported whooping cough in infancy. Pertussis should be considered for diagnosis of acute and chronic cough in adults. Future studies should evaluate the public health interest of booster doses of pertussis vaccine in adults.

Host cell traversal is important for progression of the malaria parasite through the dermis to the liver.

The malaria sporozoite, the parasite stage transmitted by the mosquito, is delivered into the dermis and differentiates in the liver. Motile sporozoites can invade host cells by disrupting their plasma membrane and migrating through them (termed cell traversal), or by forming a parasite-cell junction and settling inside an intracellular vacuole (termed cell infection). Traversal of liver cells, observed for sporozoites in vivo, is thought to activate the sporozoite for infection of a final hepatocyte. Here, using Plasmodium berghei, we show that cell traversal is important in the host dermis for preventing sporozoite destruction by phagocytes and arrest by nonphagocytic cells. We also show that cell infection is a pathway that is masked, rather than activated, by cell traversal. We propose that the cell traversal activity of the sporozoite must be turned on for progression to the liver parenchyma, where it must be switched off for infection of a final hepatocyte.

The Plasmodium eukaryotic initiation factor-2α kinase IK2 controls the latency of sporozoites in the mosquito salivary glands

Sporozoites, the invasive form of malaria parasites transmitted by mosquitoes, are quiescent while in the insect salivary glands. Sporozoites only differentiate inside of the hepatocytes of the mammalian host. We show that sporozoite latency is an active process controlled by a eukaryotic initiation factor-2α (eIF2α) kinase (IK2) and a phosphatase. IK2 activity is dominant in salivary gland sporozoites, leading to an inhibition of translation and accumulation of stalled mRNAs into granules. When sporozoites are injected into the mammalian host, an eIF2α phosphatase removes the PO4 from eIF2α-P, and the repression of translation is alleviated to permit their transformation into liver stages. In IK2 knockout sporozoites, eIF2α is not phosphorylated and the parasites transform prematurely into liver stages and lose their infectivity. Thus, to complete their life cycle, Plasmodium sporozoites exploit the mechanism that regulates stress responses in eukaryotic cells.

Development of the malaria parasite in the skin of the mammalian host

The first step of Plasmodium development in vertebrates is the transformation of the sporozoite, the parasite stage injected by the mosquito in the skin, into merozoites, the stage that invades erythrocytes and initiates the disease. The current view is that, in mammals, this stage conversion occurs only inside hepatocytes. Here, we document the transformation of sporozoites of rodent-infecting Plasmodium into merozoites in the skin of mice. After mosquito bite, ∼50% of the parasites remain in the skin, and at 24 h ∼10% are developing in the epidermis and the dermis, as well as in the immunoprivileged hair follicles where they can survive for weeks. The parasite developmental pathway in skin cells, although frequently abortive, leads to the generation of merozoites that are infective to erythrocytes and are released via merosomes, as typically observed in the liver. Therefore, during malaria in rodents, the skin is not just the route to the liver but is also the final destination for many inoculated parasites, where they can differentiate into merozoites and possibly persist.

Trafficking of Leishmania donovani promastigotes in non-lytic compartments in neutrophils enables the subsequent transfer of parasites to macrophages.

Inoculation of Leishmania (L.) spp. promastigotes in the dermis of mammals by blood‐feeding sand flies can be accompanied by the rapid recruitment of neutrophils, inflammatory monocytes and dendritic cells. Despite the presence of these lytic leucocytes, parasitism is efficiently established. We show here that Leishmania donovani promastigotes are targeted to two different compartments in neutrophils. The compartments harbouring either damaged or non‐damaged parasites were characterized at the electron microscopy (EM) level using the glucose 6‐phosphatase cytochemistry and endosome–phagosome fusion assays. One involves the contribution of lysosomes leading to the formation of highly lytic compartments where parasites are rapidly degraded. The other is lysosome‐independent and involves the contribution of a compartment displaying some features of the endoplasmic reticulum (ER) where parasites are protected from degradation. Using genetically modified parasites, we show that the promastigote surface lipophosphoglycan (LPG) is required to inhibit lysosome fusion and maintain parasites in neutrophil compartments displaying ER features. L. donovani‐harbouring neutrophils that eventually enter apoptosis can be phagocytosed by macrophages enabling the stealth entry of parasites into their final replicative host cells. Thus, the ability of L. donovani to avoid trafficking into lysosomes‐derived compartments in short‐lived neutrophils constitutes a key process for the subsequent establishment of long‐term parasitism.

Role of Adhesins and Toxins in Invasion of Human Tracheal Epithelial Cells by Bordetella pertussis

ABSTRACT Bordetella pertussis, the agent of whooping cough, can invade and survive in several types of eukaryotic cell, including CHO, HeLa 229, and HEp-2 cells and macrophages. In this study, we analyzed bacterial invasiveness in nonrespiratory human HeLa epithelial cells and human HTE and HAE0 tracheal epithelial cells. Invasion assays and transmission electron microscopy analysis showed that B. pertussis strains invaded and survived, without multiplying, in HTE or HAE0 cells. This phenomenon was bvg regulated, but invasive properties differed between B. pertussis strains and isolates and the B. pertussis reference strain. Studies with B. pertussis mutant strains demonstrated that filamentous hemagglutinin, the major adhesin, was involved in the invasion of human tracheal epithelial cells by bacteria but not in that of HeLa cells. Fimbriae and pertussis toxin were not found to be involved. However, we found that the production of adenylate cyclase-hemolysin prevents the invasion of HeLa and HTE cells byB. pertussis because an adenylate cyclase-hemolysin-deficient mutant was found to be more invasive than the parental strain. The effect of adenylate cyclase-hemolysin was mediated by an increase in the cyclic AMP concentration in the cells. Pertactin (PRN), an adhesin, significantly inhibited the invasion of HTE cells by bacteria, probably via its interaction with adenylate cyclase-hemolysin. Isolates producing different PRNs were taken up similarly, indicating that the differences in the sequences of the PRNs produced by these isolates do not affect invasion. We concluded that filamentous hemagglutinin production favored invasion of human tracheal cells but that adenylate cyclase-hemolysin and PRN production significantly inhibited this process.

Clonal conditional mutagenesis in malaria parasites.

We describe here an efficient method for conditional gene inactivation in malaria parasites that uses the Flp/FRT site-specific recombination system of yeast. The method, developed in Plasmodium berghei, consists of inserting FRT sites in the chromosomal locus of interest in a parasite clone expressing the Flp recombinase via a developmental stage-specific promoter. Using promoters active in mosquito midgut sporozoites or salivary gland sporozoites to drive expression of Flp or its thermolabile variant, FlpL, we show that excision of the DNA flanked by FRT sites occurs efficiently at the stage of interest and at undetectable levels in prior stages. We applied this technique to conditionally silence MSP1, a gene essential for merozoite invasion of erythrocytes. Silencing MSP1 in sporozoites impaired subsequent merozoite formation in the liver. Therefore, MSP1 plays a dual role in the parasite life cycle, acting both in liver and erythrocytic parasite stages.

INTRANASAL INOCULATION OF BORDETELLA BRONCHISEPTICA IN MICE INDUCES LONG-LASTING ANTIBODY AND T-CELL MEDIATED IMMUNE RESPONSES

Humoral and cellular immune responses were analysed in mice inoculated intranasally with Bordetella bronchiseptica. After infection, the number of bacteria that colonized the respiratory tract of the mice increased during the first day and decreased thereafter. Total IgG levels increased as early as 14 days after infection and decreased with time after infection, whereas total IgA and IgM levels were lower but remained stable. Specific antibodies to the bacteria were mainly IgG2a and IgA and persisted up to 10 months after infection. Some of these specific antibodies were directed against adenylate cyclase–haemolysin, the bacterial factor that had been shown to be necessary for initiation of infection. The proliferation of Bordetella bronchiseptica‐reactive spleen cells occurred during the acute phase of infection. T cells from infected mice produced increasing amounts of IFNγ and IL‐2 after infection. Although very low levels of IL‐10 were produced, no IL‐4 was detected after bacterial stimulation in vitro. These results suggest that Bordetella bronchiseptica infection induces primarily a Th1‐type T‐cell response. Importantly, the authors demonstrated that antibody and T‐cell responses directed against bacterial determinants of the virulent strain and to purified adenylate cyclase–haemolysin were long‐lasting. This observation could be due to the fact that Bordetella bronchiseptica may persist intracellularly in the host as it was demonstrated in vitro

A key role for Plasmodium subtilisin-like SUB1 protease in egress of malaria parasites from host hepatocytes.

Background: The subtilisin-like SUB1 is involved in Plasmodium egress from erythrocytes. Results: Using conditional mutagenesis, we show that SUB1 plays an essential role during Plasmodium hepatic stages. Conclusion: SUB1 has a dual pivotal role in parasite egress from host hepatocytes and erythrocytes. Significance: Its critical involvement in hepatic and erythrocytic parasite development qualifies SUB1 as a multistage drug target. In their mammalian host, Plasmodium parasites have two obligatory intracellular development phases, first in hepatocytes and subsequently in erythrocytes. Both involve an orchestrated process of invasion into and egress from host cells. The Plasmodium SUB1 protease plays a dual role at the blood stage by enabling egress of the progeny merozoites from the infected erythrocyte and priming merozoites for subsequent erythrocyte invasion. Here, using conditional mutagenesis in P. berghei, we show that SUB1 plays an essential role at the hepatic stage. Stage-specific sub1 invalidation during prehepatocytic development showed that SUB1-deficient parasites failed to rupture the parasitophorous vacuole membrane and to egress from hepatocytes. Furthermore, mechanically released parasites were not adequately primed and failed to establish a blood stage infection in vivo. The critical involvement of SUB1 in both pre-erythrocytic and erythrocytic developmental phases qualifies SUB1 as an attractive multistage target for prophylactic and therapeutic anti-Plasmodium intervention strategies.

Bordetella bronchiseptica persists in the nasal cavities of mice and triggers early delivery of dendritic cells in the lymph nodes draining the lower and upper respiratory tract.

ABSTRACT Early after the intranasal instillation of Bordetella bronchiseptica into mice, not only are mature dendritic leukocytes recovered from lung parenchyma and bronchoalveolar lavage fluid but their numbers are also increased in the mediastinal lymph nodes and the nasal mucosa-associated lymphoid tissue. Later during the infectious process, the bacteria persist mainly in the nasal cavity.