Carbapenemase-producing Enterobacteriaceae in Sweden 2007-2013: Experiences from seven years of systematic surveillance and mandatory reporting.

Carbapenemase-producing Enterobacteriaceae (CPE) are increasing worldwide, and are a major threat to healthcare systems. Recent European data support that many countries have interregional spread of CPE or an endemic situation. In Sweden mandatory laboratory reporting of CPE of both colonisation and infection has been practiced since 2007 and since 2012 also by treating physicians. Between 2007 and 2013, 94 cases of CPE were detected in Sweden, out of which 24 were considered to cause clinical infections (bloodstream infection (n=4), urinary tract infection (n=12), wound infection (n=4), respiratory tract infection (n=2) and catheter related (n=2). The majority were detected in the hospital setting through faecal screening or as probable colonisers in clinical cultures. Travel abroad was observed in the majority of the patients (81%), and among them 84% had been hospitalised. During the study period only two chains of transmissions in Swedish hospitals were reported, involving four patients. Klebsiella pneumoniae was the primarily isolated species (n=57) followed by Escherichia coli (n=29). blaNDM was the predominant carbapenemase gene (n=36), followed by blaOXA-48-group, blaKPC and blaVIM. In 26/94 cases (28%) isolates were categorised as possible XDR (extensively drug-resistant). CPE are increasing in Sweden, but are still at a comparably low level.

Immunization with apoptotic pseudovirus transduced cells induces both cellular and humoral responses: a proof of concept study in macaques.

Dendritic cells are able to present viral antigens to T-cells after uptake of apoptotic bodies derived from virus-infected cells. Immunization with virus-infected apoptotic cells was previously shown to induce HIV-specific immune responses in mice. Here we evaluate the safety and immunogenicity of immunization with activated apoptotic cells in non-human primates using autologous T-cells infected with replication defective VSV pseudotyped SIV(mac239)Δenv. Animals were immunized with γ-irradiated activated T-cells carrying the VSVenvSIV(mac239)Δenv pseudovirus. SIV Gag-specific cellular immune responses were induced as early as two weeks after the first immunization eliciting a biased IFN-γ and IL-2 response. In addition, induction of SIV Gag-specific antibody responses and high titer neutralizing activity against the SIV pseudovirus harboring a VSV-env were detected after two immunizations. The vaccinated group and a control group of Chinese rhesus macaques were intravenously challenged with pathogenic SIV(mac251.) All animals became infected, but SIV-replication was effectively suppressed (below 100 copies/ml) in several animals in both groups. However the group immunized with apoptotic cells revealed better preservation of the gut CD4(+) T-cell compartment. Viral control was inversely correlated with an early (4 weeks) but transient increase in the percentage of Ki67(+)CD4(+) peripheral blood T-cells (Spearman -0.73). We here show that immunizations with activated apoptotic lymphocytes expressing transduced SIV genes result in induction of both cellular and humoral immune responses. This study provides evidence for an immunological principle demonstrating that certain apoptotic cells can be considered as carriers of antigens directing immune responses in macaques.

Generation of neutralizing antibodies and divergence of SIVmac239 in cynomolgus macaques following short-term early antiretroviral therapy.

Neutralizing antibodies (NAb) able to react to heterologous viruses are generated during natural HIV-1 infection in some individuals. Further knowledge is required in order to understand the factors contributing to induction of cross-reactive NAb responses. Here a well-established model of experimental pathogenic infection in cynomolgus macaques, which reproduces long-lasting HIV-1 infection, was used to study the NAb response as well as the viral evolution of the highly neutralization-resistant SIVmac239. Twelve animals were infected intravenously with SIVmac239. Antiretroviral therapy (ART) was initiated ten days post-inoculation and administered daily for four months. Viral load, CD4(+) T-cell counts, total IgG levels, and breadth as well as strength of NAb in plasma were compared simultaneously over 14 months. In addition, envs from plasma samples were sequenced at three time points in all animals in order to assess viral evolution. We report here that seven of the 12 animals controlled viremia to below 10(4) copies/ml of plasma after discontinuation of ART and that this control was associated with a low level of evolutionary divergence. Macaques that controlled viral load developed broader NAb responses early on. Furthermore, escape mutations, such as V67M and R751G, were identified in virus sequenced from all animals with uncontrolled viremia. Bayesian estimation of ancestral population genetic diversity (PGD) showed an increase in this value in non-controlling or transient-controlling animals during the first 5.5 months of infection, in contrast to virus-controlling animals. Similarly, non- or transient controllers displayed more positively-selected amino-acid substitutions. An early increase in PGD, resulting in the generation of positively-selected amino-acid substitutions, greater divergence and relative high viral load after ART withdrawal, may have contributed to the generation of potent NAb in several animals after SIVmac239 infection. However, early broad NAb responses correlated with relatively preserved CD4(+) T-cell numbers, low viral load and limited viral divergence.

Neutralizing activity and cellular immune responses induced in mice after immunization with apoptotic HIV-1/murine leukemia virus infected cells.

Dendritic cells present microbial antigens to T cells after uptake of apoptotic vesicles from infected cells. We previously reported that immunizations with apoptotic HIV-1/murine leukemia virus (MuLV) infected cells lead to induction of both cellular and humoral immune responses as well as resistance to mucosal challenge with live HIV-1/MuLV infected cells. Here we extended those studies and investigated whether apoptotic cells from HIV-1/MuLV infected cells stimulate the production of HIV-1 neutralizing activity. We compared different routes of administration and were able to induce p24- and Nef-specific cellular proliferation after intraperitoneal (i.p.), intranasal (i.n.), subcutaneous (s.c.) and intramuscular (i.m.) immunizations. Serum IgG and IgA antibodies directed against gp160, p24, or Nef were also produced regardless of immunization route used. However, the induction of mucosa-associated IgAs from faeces or vaginal secretions were detected only after either i.p. or i.n. immunizations. We were able to measure neutralizing activity in sera of mice after i.p. and i.n. immunization. Neutralizing reactivity was also detected after s.c. and i.m. immunizations in the presence of the cytokine adjuvant granulocyte macrophage-colony stimulating factor (GM-CSF). Conclusively we show induction of cellular and humoral immune responses including neutralizing activity after immunization with apoptotic HIV-1/MuLV infected cells in mice. The results from this study support further evaluations using apoptotic cells as antigen delivery system for vaccination against HIV-1 in other animal models.

A novel assay for assessment of HIV-specific cytotoxicity by multiparameter flow cytometry.

BACKGROUND: Assessment of CD8(+) T-cell activity is of significant importance for the evaluation of cellular immune responses to viral infections, especially in HIV. We present a new assay for the assessment of HIV-specific cytotoxicity by multiparameter flow cytometry. METHODS: Target cells, pulsed with peptide pools (Gag or Nef), were stained with 5- (and -6)-carboxyfluorescein diacetate succinimidyl ester (CFSE), cultured with specific or nonspecific effector cells, and finally stained with propidium iodide (PI). Determination of cytolysis is based on the enumeration of viable target cells (CFSE(hi)PI(-)) in the test sample (target and specific effector cells) as compared with that of the viable target cells in the control sample (target and nonspecific effector cells). The (51)Cr-release assay and IFN-gamma ELISpot were performed by standard procedures. RESULTS: A comparison with the Cr-release showed that the two assays were strongly correlated (r = 0.67; P < 0.001) but the sensitivity of the flow cytometric assay was significantly higher (P < 0.05), and the reproducibility good (CV, 7.7%). Good correlation was also found with the ELISpot assay (r = 0.66; P < 0.01). CONCLUSION: This new assay provides both specific and sensitive results when employed for the detection of HIV-specific CTL and can be a valuable tool for the evaluation of cytolytic activity in vaccine trials or in HIV-infected subjects, especially if such responses are present at low levels.

ELISpot and ELISA analysis of spontaneous, mitogen-induced and antigen-specific cytokine production in cynomolgus and rhesus macaques.

Evaluation of cytokine production in macaques has been hampered by a lack of availability of optimized and standardized immunoassays such as ELISA and enzyme-linked immune spot assay (ELISpot); only a limited number of macaque cytokines have been assessed by ELISpot. Using monoclonal antibodies (mAb) to human cytokines that cross-react with cynomolgus and rhesus macaque interferon-gamma (IFN-gamma), interleukin (IL)-2, IL-4, IL-5, IL-6, IL-12, IL-13 and granulocyte monocyte colony-stimulating factor, we measured macaque cytokine production by ELISA and ELISpot. Quantitation of spontaneous as well as phytohemagglutinin (PHA)-induced cytokine production in peripheral blood mononuclear cells (PBMC) from rhesus and cynomolgus macaques and humans were compared. The proportional distribution of the different cytokines, in terms of PBMC synthesizing different cytokines as well as the levels of the different cytokines produced, were similar in all species. Spontaneous- and PHA-induced cytokine productions thus appear to be similarly regulated in macaques and man. ELISpot and ELISA assays for macaque IFN-gamma were further used to measure antigen-specific immune responses of PBMC from cynomolgus macaques exposed to, or vaccinated against, simian immunodeficiency virus (SIV). The establishment of reliable immunoassays for detection of macaque cytokines is of importance for future progress of research utilizing macaques as experimental animals.