Phase I study of CC-90010, a reversible, oral BET inhibitor in patients with advanced solid tumors and relapsed/refractory non-Hodgkin's lymphoma.

BACKGROUND: Bromodomain and extra-terminal (BET) proteins are epigenetic readers that regulate expression of genes involved in oncogenesis. CC-90010 is a novel, oral, reversible, small-molecule BET inhibitor. PATIENTS AND METHODS: CC-90010-ST-001 (NCT03220347; 2015-004371-79) is a phase I dose-escalation and expansion study of CC-90010 in patients with advanced or unresectable solid tumors and relapsed/refractory (R/R) non-Hodgkin's lymphoma (NHL). We report results from the dose escalation phase, which explored 11 dose levels and four dosing schedules, two weekly (2 days on/5 days off; 3 days on/4 days off), one biweekly (3 days on/11 days off), and one monthly (4 days on/24 days off). The primary objectives were to determine the safety, maximum tolerated dose (MTD) and/or recommended phase II dose (RP2D) and schedule. Secondary objectives were to evaluate signals of early antitumor activity, pharmacokinetics, and pharmacodynamics. RESULTS: This study enrolled 69 patients, 67 with solid tumors and two with diffuse large B-cell lymphoma (DLBCL). The median age was 57 years (range, 21-80) and the median number of prior regimens was four (range, 1-9). Treatment-related adverse events (TRAEs) were mostly mild and manageable; grade 3/4 TRAEs reported in more than two patients were thrombocytopenia (13%), anemia, and fatigue (4% each). Six patients had dose-limiting toxicities. MTDs were 15 mg (2 days on/5 days off), 30 mg (3 days on/11 days off), and 45 mg (4 days on/24 days off). The RP2D and schedule selected for expansion was 45 mg (4 days on/24 days off). As of 8 October 2019, one patient with grade 2 astrocytoma achieved a complete response, one patient with endometrial carcinoma had a partial response, and six patients had prolonged stable disease ≥11 months. CONCLUSIONS: CC-90010 is well tolerated, with single-agent activity in patients with heavily pretreated, advanced solid tumors.

Deficient recognition of emotional prosody in primary focal dystonia.

BACKGROUND: Primary dystonia is a movement disorder attributed mainly to basal ganglia dysfunction. Besides motor control, striatopallidal structures are known to implement also non-motor functions including processing of cognitive and emotional information. Previous research has already demonstrated deficient recognition of emotional faces in patients with primary focal dystonia. However, it remains elusive if emotional prosody processing in dystonia is also affected. METHODS: In this study, 30 patients with primary cervical dystonia (CD) and 30 healthy control subjects (HC) had to classify auditory presented words according to their emotional prosody (angry, happy, relaxed, sad). RESULTS: Analysis of hit rates and reaction times revealed a significantly poorer performance of patients with CD in judging angrily intonated words. Additional psychological assessment (SCL-90 R) demonstrated a higher level of psychological distress in patients with CD who displayed symptoms of somatization, anxiety and depression. CONCLUSIONS: Together these findings bring further insight into the basal ganglia involvement in processing of emotional prosody and emphasize the importance to identify the psychopathological symptoms in patients with CD as complementary to the motor deficit.

Multicentre phase II studies evaluating imatinib plus hydroxyurea in patients with progressive glioblastoma.

BACKGROUND: We evaluated the efficacy of imatinib mesylate in addition to hydroxyurea in patients with recurrent glioblastoma (GBM) who were either on or not on enzyme-inducing anti-epileptic drugs (EIAEDs). METHODS: A total of 231 patients with GBM at first recurrence from 21 institutions in 10 countries were enrolled. All patients received 500 mg of hydroxyurea twice a day. Imatinib was administered at 600 mg per day for patients not on EIAEDs and at 500 mg twice a day if on EIAEDs. The primary end point was radiographic response rate and secondary end points were safety, progression-free survival at 6 months (PFS-6), and overall survival (OS). RESULTS: The radiographic response rate after centralised review was 3.4%. Progression-free survival at 6 months and median OS were 10.6% and 26.0 weeks, respectively. Outcome did not appear to differ based on EIAED status. The most common grade 3 or greater adverse events were fatigue (7%), neutropaenia (7%), and thrombocytopaenia (7%). CONCLUSIONS: Imatinib in addition to hydroxyurea was well tolerated among patients with recurrent GBM but did not show clinically meaningful anti-tumour activity.

A novel family of serine/threonine kinases participating in spermiogenesis.

The molecular mechanisms regulating the spectacular cytodifferentiation observed during spermiogenesis are poorly understood. We have recently identified a murine testis-specific serine kinase (tssk) 1, constituting a novel subfamily of serine/threonine kinases. Using low stringency screening we have isolated and molecularly characterized a second closely related family member, tssk 2, which is probably the orthologue of the human DGS-G gene. Expression of tssk 1 and tssk 2 was limited to the testis of sexually mature males. Immunohistochemical staining localized both kinases to the cytoplasm of late spermatids and to structures resembling residual bodies. tssk 1 and tssk 2 were absent in released sperms in the lumen of the seminiferous tubules and the epididymis, demonstrating a tight window of expression restricted to the last stages of spermatid maturation. In vitro kinase assays of immunoprecipitates containing either tssk 1 or tssk 2 revealed no autophosphorylation of the kinases, however, they led to serine phosphorylation of a coprecipitating protein of approximately 65 kD. A search for interacting proteins using the yeast two-hybrid system with tssk 1 and tssk 2 cDNA as baits and a prey cDNA library from mouse testis, led to the isolation of a novel cDNA, interacting specifically with both tssk 1 and tssk 2, and encoding the coprecipitated 65-kD protein phosphorylated by both kinases. Interestingly, expression of the interacting clone was also testis specific and paralleled the developmental expression observed for the kinases themselves. These results represent the first demonstration of the involvement of a distinct kinase family, the tssk serine/threonine kinases, together with a substrate in the cytodifferentiation of late spermatids to sperms.

Combined FTY720/cyclosporine treatment promotes graft survival and lowers the peripheral lymphocyte count in a murine cardiac allotransplantation model.

BACKGROUND: FTY720 lowers the peripheral lymphocyte count (PLC) by accelerating the migration of circulating lymphocytes to secondary lymphoid organs. We investigated the efficacy of combined FTY720+cyclosporine (CsA) treatment versus monotherapy on prolonging graft survival and on lowering the PLC. METHODS: BALB/c hearts were heterotopically grafted in C3H mice. FTY720 was administered alone or in combination with CsA. PLC and body weight were determined on day 7, day 28, or the day of rejection. RESULTS: Combining FTY720 with CsA prolonged, dose-dependently and significantly, the allograft survival. FTY720, but not CsA, lowered the PLC dose-dependently. The granulocyte count was not reduced in any group. FTY720 concentrations were not influenced by the CsA co-administration. CONCLUSIONS: Combined FTY720 and CsA treatment was well tolerated, promoted graft survival, and suppressed the inflammatory allo-response. The PLC lowering correlated well with the antirejection effects in the two-drug regimens, suggesting that the PLC might guide FTY720 therapy at low doses.

Prevention of graft vessel disease by combined FTY720/cyclosporine. A treatment in a rat carotid artery transplantation model.

BACKGROUND: Graft vessel disease (GVD) is an important problem often responsible for late graft loss. The effects of FTY720, an immunomodulator with a novel mechanism of action were investigated in combination with cyclosporine A (CsA) in a carotid artery allograft model. METHODS: A segment of the carotid artery of Lewis rats was replaced by a DA allograft. Seven groups of eight rats were treated for 8 weeks with vehicle (P), CsA 0.3 (C0.3), 1 (C1) or 3 (C3) mg x kg(-1).day(-1) or a combination of CsA 1 with FTY 0.01 (C1F0.01), 0.03 (C1F0.03), and 0.1 (C1F0.1) mg x kg(-1).day(-1). Lumen area was estimated by magnetic resonance imaging, peripheral lymphocyte count and drug concentrations were determined at 1 and 8 weeks. Neointima, media, and lumen area were measured morphometrically. Intimal and adventitial infiltration of mononuclear cells, and medial smooth muscle cells number was assessed using a score. RESULTS: FTY720 did not influence CsA blood concentrations. FTY720 but not CsA decreased the PLC dose dependently. Magnetic resonance imaging revealed that treatment groups have larger lumen size than group P. Histological and morphometric evaluation showed that all aspects of GVD were dose dependently suppressed by treatment and lumen narrowing was prevented. CONCLUSIONS: CsA, at clinically relevant blood levels, suppressed GVD only partly. The addition of FTY720 was well tolerated and completely suppressed GVD development. In vivo lumen size did not correlate with the histologically estimated neointimal thickness.

Transplantation-induced endothelial dysfunction as studied in rat aorta allografts.

BACKGROUND: Clinical evidence indicates that vascular endothelial cell (EC) dysfunction occurs early after transplantation (Tx) and initiates chronic graft vasculopathy. This study explored this phenomenon in rat aorta Tx using the stringent Dark Agouti (DA)-to-Lewis (LEW) and the weak Fischer 344 (F344)-to-LEW strain combinations. METHODS: Donor abdominal aortae were orthotopically grafted into LEW rats. At post-Tx days 7, 14, 28, and 56, grafts were collected to assess changes in EC morphology (en face silver staining) and EC function, i.e., vasodilatory response to acetylcholine (ACH) after phenylephrine (PHE) precontraction; changes in vascular smooth muscle cell (VSMC) alpha-actin (western blotting), degree of apoptosis (caspase-3 activity), and morphology. RESULTS: In DA allografts, VSMC and EC dysfunctions developed concomitantly and were completed at 14 days post-Tx, most likely due to the EC and alpha-actin-positive VSMC loss. Meanwhile, allografts revealed markedly increased caspase-3 activity. Neointima formation, restricted to the edges of allografts at day 28, covered the entire allografts by day 56 post-Tx. In F344-allografts, VSMC function was maintained up to day 14 post-Tx, whereas ACH-induced relaxation was reduced by 50% at day 7 and abolished at day 14. EC denudation was not seen up to 56 days post-Tx, despite prominent leukocyte adhesion. Neointima formation was not detected at day 28 post-Tx but appeared along the entire allografts at day 56 post-Tx. CONCLUSIONS: These results confirm that Tx-induced EC dysfunction precedes the development of vasculopathy in rat aorta allografts and suggest that this early phenomenon can be best studied in the F344-to-LEW strain combination.

Rare KIT (CD117) expression in multiple myeloma abrogates the usefulness of imatinib mesylate treatment.

BACKGROUND: Imatinib mesylate blocks the tyrosine kinase activity of KIT (CD117) and is an effective treatment for gastrointestinal stromal tumors. In multiple myeloma, KIT expression has been detected by flow cytometry in about 33% of specimens, but no previous immunohistochemical assessment has yet been made of the expression pattern of KIT. MATERIALS AND METHODS: We performed immunohistochemical analyses of 100 patients, including 72 with multiple myeloma (MM), 8 with lymphoplasmacytic lymphoma (LPL), 10 with monoclonal gammopathy of undetermined significance (MGUS) and 10 with reactive plasmocytosis. One KIT-positive MM was sequenced using polymerase chain reaction analysis. RESULTS: In MM, only 2 cases (2.8%) were KIT positive. The great majority of the cases (97, 2%) did not express the KIT receptor tyrosine kinase. No mutation of the c-kit gene was detected. CONCLUSIONS: KIT expression is a rare event in MM and not detectable in MGUS and LPL. Therefore, treatment with imatinib is unlikely to be effective in these patients.

The peripheral lymphocyte count predicts graft survival in DA to Lewis heterotopic heart transplantation treated with FTY720 and SDZ RAD.

OBJECTIVE: The new immunomodulator 2-amino-2-(2-[4-octylphenyl]ethyl)-1,3-propanediol hydrochloride (FTY720) lowers the peripheral lymphocyte count (PLC) by inducing migration of circulating lymphocytes to secondary lymphoid organs. This effect is dose-dependent at low (up to 0.1 mg/kg per day) doses in rats. We investigated the correlation between PLC and the later rejection, when FTY720 was combined with RAD. METHODS: Heterotopic cardiac grafting was performed using the DA-Lewis strain combination. FTY720 and RAD were administered as single daily doses by gavage alone and in combination starting 3 days before to 28 days after transplantation. Graft survival was monitored daily by palpation. PLC was determined at 1 and 4 weeks, body weight (BW) weekly. Histologic evaluation of grafted hearts was performed after rejection. MAIN FINDINGS: FTY720 at doses of 0.03, 0.1 and 0.3 mg/kg per day prolonged graft survival dose-dependently from 6 (placebo) to 7, 9.5 and 15 days median survival time (MST). RAD at doses of 0.3, 1 and 3 mg/kg per day delayed rejection to 8.5, 18 and 37.5 days MST. Very small FTY720 doses added to the lower RAD doses were effective in maintaining grafts throughout the treatment period and with normal weight gain, as opposed to regimens with 1 mg/kg or more per day RAD, which resulted in delayed weight gain. FTY720 lowered the PLC significantly and dose-dependently. The PLC correlated well with graft survival [Spearman rank correlation (n = 30, rs = -0.75)]. CONCLUSIONS: Fully effective FTY720 + RAD combination regimens caused no side effects with respect to the rats' general well-being or weight gain and were better tolerated than equiactive RAD monotherapy, suggesting a broader therapeutic window for the combinations. Under the experimental conditions, the PLC decrease showed an interesting correlation with the anti-rejection effects in these two-drug regimens. Thus, in rats the PLC is helpful for monitoring the biological activity of FTY720 at low doses (< 0.1 mg/kg per day), i.e. in the range of the steep part of its dose-response relationship.

Efficacy of SDZ RAD compared with CsA monotherapyand combined Rad/FTY720 treatment in a murine cardiac allotransplantation model.

OBJECTIVE: The macrolide immunosuppressant RAD and the immunomodulator FTY720 have distinct mechanisms ofaction. We investigated the efficacy of RAD (everolimus, certican) alone or in combination with FTY720 on graft survival (GS)and histology in comparison with CsA, using mouse strains with strong MHC disparity. METHODS: Heterotopic cardiac grafting was performed using the C57B1/6 to C3H strain combination. Osmotic mini-pumps filled with CsA or RAD were implanted subcutaneously. IFTY720 was administered as a single daily dose by gavage. Peripheral lymphocyte count (PLC) was determined at 1, 4 and 8 weeks or on the day of sacrifice. Body weight was recorded on the day of surgery and weekly. Grafts were histologically evaluated. MAIN FINDINGS: In placebo-treated mice the allografts were rejected after 7 days. Monotherapy with 10 and 30 mg/kg/day CsA achieved 10 and 22.5 days median survival time (MST), while 0.1, 0.3, 1 and 3 mg/kg/day RAD resulted in 10.5, 20, > 56 and > 56 days MST, respectively. FTY720 lowered the PLC significantly, while the lower CsA dose and RAD did not influence the PLC. Adding FTY720 to the 0.6 mg/kg/day dose of RAD extended GS modestly but reduced significantly the perivascular infiltration and endothelialitis in the grafts compared with RAD monotherapy. CONCLUSIONS: Underthe conditions of the present experiment RAD was more potent than CsA in extending the GS. Combining FTY720 and RADwas well tolerated with respect to weight gain and lack of clinically detectable infections in the mice. The 2-drug regimens suppressed the inflammatory allo-response better than RAD monotherapy.

Combined FTY720/cyclosporine A treatment promotes graft survival and lowers the peripheral lymphocyte count in DA to lewis heart and skin transplantation models.

OBJECTIVE: The immunomodulator, FTY720, lowers the peripheral lymphocyte count (PLC) by inducing migration of circulating lymphocytes to secondary lymphoid organs. We investigated the efficacy of mono- vs. combined-FTY720/CsA therapy on graft survival (GS) and on lowering the PLC in a solid organ and a skin graft model, using strains with strong MHC disparity. METHODS: Heterotopic cardiac or tail skin grafting was performed using the DA (RT1a) to Lewis (RT1(1)) rat strain combination. FTY720 was administered as a single daily dose by gavage alone or in combination with subcutaneously delivered CsA. PLC, body weight and drug concentrations were determined on day 7, 28, or the day of rejection. MAIN FINDINGS: In placebo-treated animals the heart and skin allografts rejected after 6 and 8 days. FTY720 delayed rejection of both the solid organ and skin grafts. The maximal effect was achieved at 1 mg x kg(-l) x day(-1) FTY720, resulting in a median survival time (MST) of 14 days for both allotransplants comparable to the effect achieved by 1 mg x kg x day(-1) CsA in both models. In the cardiac graft experiment with CsA co-administration, doses of 0.3 and 1 mg/kg were used. Under these conditions very small doses of FTY720 were effective in maintaining grafts throughout the treatment period. Adding higher FTY720 doses to the 1 mg x kg(-1) x day(-1) CsA was needed to effectively extend the skin GS, e.g. 0.3 mg x kg(-l) x day(-1) FTY720 prolonged GS from 13 to 47.5 days MST, i.e. well beyond the 28 day-treatment period. CsA did not influence the PLC at clinically relevant doses. FTY720 lowered the PLC significantly and dose-dependently, at doses lower than those needed for the prolongation of both cardiac and skin GS with FTY720 monotherapy. In rats with skin grafts the PLC was markedly lowered up to 1 mg x kg(-1) x day(-1) FTY720, whereas, in the heart model, it was lowered up to 0.1 mg x kg(-1) x day(-1). Independently of the graft type, within the combination regimens 0.3 mg x kg(-1) x day(-1) FTY720 achieved a maximal PLC depletion. CONCLUSIONS: Combining FTY720 and CsA was very well tolerated with respect to weight gain and lack of any clinically detectable infections. In the strain combination used FTY720 monotherapy was less effective than previously reported in maintaining grafts. The two-drug regimens extended strikingly the GS for both models. However, the prolongation of the heart GS was smoothly dose-related with FTY720 doses ranging from 0.01 to 1 mg x kg(-1) x day(-1) , whereas, the skin graft prolongation was modest at doses up to 0.1 mg x kg(-1) x day(-1) and remarkably enhanced at 0.3 and 1 mg x kg(-1) x day(-1) FTY720.

Demonstration of nitric oxide synthase (NOS) in marmosets by NADPH diaphorase (NADPH-d) histochemistry and NOS immunoreactivity.

Since species interdiversity often prevents the extrapolation of laboratory rodent data to man and similar problems may exist for nitric oxide synthase (NOS), NADPH-d activity and immunohistochemistry of NOS were investigated in the New World monkey Callithrix jacchus (marmoset), which has been shown to be close to the human situation in many respects. Using the NADPHd reaction with beta-NADPH and nitroblue tetrazolium (NBT) on acetone-chloroform pretreated cryosections, NBT formazan was found in many neural and non-neural (e.g. diverse epithelia, striated muscle fibers, vascular endothelium) cells in numerous tissues and organs. Prefixation with formaldehyde lowered the number of NADPH-d active sites and the amount of formazan with the exception of neuronal NADPH-d as did incubation of fresh or acetone-chloroform-pretreated sections for NADPH-d in the presence of 0.5% formaldehyde. When 1% formaldehyde or 0.5 mM permanganate were used significant amounts of formazan appeared only in central and peripheral neurons, vasal endothelial cells, small intestinal enterocytes, plasma membrane region of striated muscle fibers as well as arteriolar cells in the kidney; except for enterocytes, these observations were confirmed by NOS-immunohistochemistry which revealed in addition reactive cells in the thymus and intestinal lamina propria.

Female sex organs malignancies incidence in Plovdiv district for the period 1986-1996.

The aim of the recent survey is to investigate the dynamics of female sex organs malignancies (carcinoma of the uterine corpus, cervical carcinoma and ovarial carcinoma) incidence and to make a structural analysis. The incidence of female sex organs malignancies increases every other year from 37.7 cases in 1986 to 58.64 cases per 100,000 women in 1996. The cervical carcinoma incidence for that period increases from 8.1 cases in 1986 to 14.65 cases per 100,000 women in 1996. For the same period endometrial carcinoma incidence increases from 16.2 cases to 24.74 cases per 100,000 and ovarial carcinoma incidence--from 13.0 cases to 19.64 cases per 100,000. Malignancy staging is an important part of the study. Clinical stage I is diagnosed only in 25.28% of the new cases, stage II--in 46.02%, stage III--in 17.75% and, stage IV--in 10.95% of the cases. The incidence of female sex organs malignancies in the examined, regions and locations shows that there are some differences between the three regions of Plovdiv district (Plovdiv, Pazardjik and Smolyan). The region of Plovdiv has a highest incidence. There are also a differences in the incidence between the citizens of the town and the villages.

Estimation of trends of morbidity of colorectal cancer in Plovdiv district for the period from 1985 to 1996.

The present study concerns the incidence rate of colorectal cancer (CRC) in Plovdiv region (population 1,269,464). The study was carried out over a 12-year period and aimed at establishing the increase rate of this disease. Results show that incidence rate of CRC increased progressively for the mentioned period from 22.14 to 34.98 per 100,000 people and was almost twice as high as that for the country. It is a particularly disturbing fact that the morbidity and mortality rates due to colorectal cancer is rising--2.36 times for 12 years. We propose screening for asymptomatic and high risk patients with considerable results for opportune diagnostics.

Trends in the incidence of colorectal carcinoma in three regions of south Bulgaria for the period 1985-1998.

The purpose of the present study was to evaluate the increase of colorectal carcinoma incidence in three regions of South Bulgaria (a total population of 1,269,464 persons) over a 14-year period (1985-1998). The data about the incidence rate are retrieved from the oncological hospital records of the patients and Bulgarian National Oncological Register. The census data are provided by the National Institute of Statistics, Sofia. The results show that the incidence rate of colorectal carcinoma for the studied period increased steadily from 22.14/100,000 to 37.18/100,000 (an increment of 15.04/100,000) which is almost twice the average for the country. Compared to the baseline year of 1985 the increase in these three regions is 67.93% or approximately 5% annually. The incidence rate in Plovdiv region was almost twice that of Smolyan region. The incidence rate of colorectal carcinoma in both genders was greater than that of stomach cancer. The highest incidence rate was found in the 70-79-year-age group (193.5/100,000). A major part of our study was to find the stage in which colorectal carcinoma (CRC) is detected. In 1985 only 0.57% of the patients were diagnosed as being in the I-st clinical stage, 37.76%--in the II-nd, and 61.67%--in III-IV clinical stages. This unfavorable trend was preserved in 1998, when only 3.17% were diagnosed as having the first clinical stage, 38.62%--the II-nd and 58.21%--the III-IV clinical stages. The 14-year pronounced trend of increase of the prevalence rate (a 2.91 times increment) and the mortality rate (a 2.50 times increment) of colorectal carcinoma is especially alarming. We propose screening of the asymptomatic patients and high-risk persons which gives considerable results in the timely diagnostics of colorectal carcinoma.

[Interepidemic influenza in Bulgaria based on laboratory research data]. / Mezhépidemicheskii gripp v Bolgarii po dannym laboratornykh issledovanii.

During the interepidemic periods of 34 years (1955-1988) the National Influenza Centre of Bulgaria with the aid of 11 supporting stations investigated a total of 27240 nasopharyngeal washings and 42530 paired sera of patients with acute respiratory diseases. Eighty strains of subtype A (H1N1) influenza virus, 60 strains of subtype a (H2N2), 148 strains of subtype A (H3N2), 3 strains of subtype A (Heg2, Neg2), 2 strains of subtype A (Hsw1N1), 14 strains of type B, and 6 strains of type C were isolated. Serologically positive results for influenza were observed in 12.65% for influenza type A virus, 3.83% for type B, and 1.78% for type C (on the whole in 18.26%). The data obtained enable to recommend that practicing physicians should not hesitate to make the diagnosis of influenza during the interepidemic periods on the basis of sufficient clinical and especially epidemiological data and should actively try to get the laboratory verification of the preliminary diagnosis.

[Age profile of the antihemagglutinins and antineuraminidase antibodies in type A influenza (author's transl)]. / Vozrastnoi profil' antigemaggliutininov i antineiraminidaznykh antitel pri grippe tipa A

Antineuraminidase and antihemagglutinating antibody studies were carried out in parallel in sera from subjects born in Bulgaria in 1968-1972, 1956-1960, 1946-1950, 1925-1935 and 1917-1920. It was found that the amount of both antineuraminidase and antihemagglutinating antibody in sera from normal subjects could vary depending upon the year of birth and the strain used for the test. The antibody spectrum was most narrow in children under 4 and wider in subjects born before 1925. Serograms of the age distribution of antineuraminidase antibody were different in 4 out of 5 strains used which confirmed the hypothesis of Francis and Davenport of the more solid immunological response to the first exposure to virus. Parallel examinations of the antibody spectrum in human sera confirmed differences in the antigenic specificity of the "active center" of neuraminidases of A/Hong Kong/1/68 (H3N2) and A/Singapore/1/57 (H2N2) viruses and for the first time provided evidence attesting to the existence of similar strain differences in neuraminidases belonging to the N1 group. Examinations for antineuraminidase antibody in addition to antihemagglutinins increase the effectiveness of evaluation of the immunological structure of the population.

[Study of human influenza viruses isolated in 1982 which are antigenically related to the swine flu virus]. / Izuchenie virusov grippa chelovka 1982 g. vydeleniia, antigenno rodstvennykh virusu grippa svinei.

Influenza A viruses (H1N1 serovariant) antigenically related to swine influenza viruses were isolated in March, 1982, from two sick adolescents in a rural area of Bulgaria who had had contacts with each other and with animals. The isolates, A/PRB/120/82 and A/PRB/121/82, were found to have hemagglutinin containing antigenic regions typical of hemagglutinin of both A/New Jersey/8/76 strain and A/swine/Finister/HG/82 strain. Because of the unusual structure of hemagglutinin, it is assumed that these viruses have not been introduced into Europe from the American continent. The limited nature of the outbreak is associated with the presence in virions of A/PRB/120/82 and A/PRB/121/82 strains of NP-protein typical of animal influenza viruses.

[Antigenic characteristics of different variants of influenza virus A(H3/N2) and their circulation in the USSR and People's Republic of Bulgaria in 1968-1980]. / Antigennaia kharakteristika raznykh variantov virusa grippa A(H3/N2) i ikh tsirkuliatsiia v SSSR i NRB v 1968-1980 gg.

Influenza A (H3N2) virus strains isolated in 1968-1980 in the USSR (1908 strains), PRB (1413 strains) and in other countries were studied comparatively. Among 15 drift variants described in the literature only 6 were found to have sequential epidemic spread. In all the instances the epidemics occurred after importation of the virus from abroad, the interval between the emergence of a new drift variant and its detection in the study areas ranged from 2 1/2 months to 1 1/2 years and was not synchronous for the USSR and PRB. A progressive decrease of the antigenic determinant typical of the prototype A/Hong Kong/1/68 in hemagglutinin and neuraminidase of the drift variants was observed. The strains isolated in 1979-1980 were not directly related to the A/Hong Kong/1/68 strain but were connected with it through intermediate variants circulating in 1974-1975.

[The laboratory epidemiological study of the joint circulation of the influenza virus A subtypes A/H1N1/ and A/H3N2/ in Bulgaria]. / Laboratorno-épidemiologicheskoe izuchenie sovmestnoi tsirkuliatsii podtipov A/H1N1/ i A/H3N2/ virusa grippa A v Bolgarii.

The National Influenza Center of Bulgaria made the epidemiological analysis of the spread of influenza virus, type A, for the period of 11 years on the basis of mass laboratory investigations. Subtype A (H1N1) was found to be the main factor of epidemics in 1978 and 1982, while the epidemics of 1980, 1983, 1985, 1986, 1987 and 1988 were mainly caused by subtype A (H3N2). The data of laboratory and epidemiological studies indicated that after 20-year absence influenza virus A, subtype A (H1N1), was found again to circulate among the population of Bulgaria, and in 1978-1988 circulated simultaneously with the previous subtype A (H3N2). The simultaneous circulation of two subtypes of influenza virus was of great importance for the frequency, spread and duration of influenza epidemics.